Publications by authors named "Stephanie L Safgren"

30 Publications

  • Page 1 of 1

Cancer-specific CTCF binding facilitates oncogenic transcriptional dysregulation.

Genome Biol 2020 09 15;21(1):247. Epub 2020 Sep 15.

Center for Public Health Genomics, University of Virginia School of Medicine, Charlottesville, VA, USA.

Background: The three-dimensional genome organization is critical for gene regulation and can malfunction in diseases like cancer. As a key regulator of genome organization, CCCTC-binding factor (CTCF) has been characterized as a DNA-binding protein with important functions in maintaining the topological structure of chromatin and inducing DNA looping. Among the prolific binding sites in the genome, several events with altered CTCF occupancy have been reported as associated with effects in physiology or disease. However, hitherto there is no comprehensive survey of genome-wide CTCF binding patterns across different human cancers.

Results: To dissect functions of CTCF binding, we systematically analyze over 700 CTCF ChIP-seq profiles across human tissues and cancers and identify cancer-specific CTCF binding patterns in six cancer types. We show that cancer-specific lost and gained CTCF binding events are associated with altered chromatin interactions, partially with DNA methylation changes, and rarely with sequence mutations. While lost bindings primarily occur near gene promoters, most gained CTCF binding events exhibit enhancer activities and are induced by oncogenic transcription factors. We validate these findings in T cell acute lymphoblastic leukemia cell lines and patient samples and show that oncogenic NOTCH1 induces specific CTCF binding and they cooperatively activate expression of target genes, indicating transcriptional condensation phenomena.

Conclusions: Specific CTCF binding events occur in human cancers. Cancer-specific CTCF binding can be induced by other transcription factors to regulate oncogenic gene expression. Our results substantiate CTCF binding alteration as a functional epigenomic signature of cancer.
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http://dx.doi.org/10.1186/s13059-020-02152-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7493976PMC
September 2020

GLI1/GLI2 functional interplay is required to control Hedgehog/GLI targets gene expression.

Biochem J 2020 09;477(17):3131-3145

Schulze Center for Novel Therapeutics, Division of Oncology Research, Mayo Clinic, Rochester, MN, U.S.A.

The Hedgehog-regulated transcription factors GLI1 and GLI2 play overlapping roles in development and disease; however, the mechanisms underlying their interplay remain elusive. We report for the first time that GLI1 and GLI2 physically and functionally interact in cancer cells. GLI1 and GLI2 were shown to co-immunoprecipitate in PANC1 pancreatic cancer cells and RMS13 rhabdomyosarcoma cells. Mapping analysis demonstrated that the zinc finger domains of both proteins are required for their heteromerization. RNAi knockdown of either GLI1 or GLI2 inhibited expression of many well-characterized GLI target genes (BCL2, MYCN, PTCH2, IL7 and CCND1) in PANC1 cells, whereas PTCH1 expression was only inhibited by GLI1 depletion. qPCR screening of a large set of putative canonical and non-canonical Hedgehog/GLI targets identified further genes (e.g. E2F1, BMP1, CDK2) strongly down-regulated by GLI1 and/or GLI2 depletion in PANC1 cells, and demonstrated that ANO1, AQP1 and SOCS1 are up-regulated by knockdown of either GLI1 or GLI2. Chromatin immunoprecipitation showed that GLI1 and GLI2 occupied the same regions at the BCL2, MYCN and CCND1 promoters. Furthermore, depletion of GLI1 inhibited GLI2 occupancy at these promoters, suggesting that GLI1/GLI2 interaction is required for the recruitment of GLI2 to these sites. Together, these findings indicate that GLI1 and GLI2 co-ordinately regulate the transcription of some genes, and provide mechanistic insight into the roles of GLI proteins in carcinogenesis.
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http://dx.doi.org/10.1042/BCJ20200335DOI Listing
September 2020

Antitumor activity of Z-endoxifen in aromatase inhibitor-sensitive and aromatase inhibitor-resistant estrogen receptor-positive breast cancer.

Breast Cancer Res 2020 05 19;22(1):51. Epub 2020 May 19.

Department of Oncology, Mayo Clinic, Rochester, MN, USA.

Background: The tamoxifen metabolite, Z-endoxifen, demonstrated promising antitumor activity in endocrine-resistant estrogen receptor-positive (ER+) breast cancer. We compared the antitumor activity of Z-endoxifen with tamoxifen and letrozole in the letrozole-sensitive MCF7 aromatase expressing model (MCF7AC1), as well as with tamoxifen, fulvestrant, exemestane, and exemestane plus everolimus in a letrozole-resistant MCF7 model (MCF7LR).

Methods: MCF7AC1 tumor-bearing mice were randomized to control (no drug), letrozole (10 μg/day), tamoxifen (500 μg/day), or Z-endoxifen (25 and 75 mg/kg). Treatment in the letrozole arm was continued until resistance developed. MCF7LR tumor-bearing mice were then randomized to Z-endoxifen (50 mg/kg) or tamoxifen for 4 weeks and tumors harvested for microarray and immunohistochemistry analysis. The antitumor activity of Z-endoxifen in the MCF7LR tumors was further compared in a second in vivo study with exemestane, exemestane plus everolimus, and fulvestrant.

Results: In the MCF7AC1 tumors, both Z-endoxifen doses were significantly superior to control and tamoxifen in reducing tumor volumes at 4 weeks. Additionally, the 75 mg/kg Z-endoxifen dose was additionally superior to letrozole. Prolonged letrozole exposure resulted in resistance at 25 weeks. In MCF7LR tumor-bearing mice, Z-endoxifen significantly reduced tumor volumes compared to tamoxifen, letrozole, and exemestane, with no significant differences compared to exemestane plus everolimus and fulvestrant. Additionally, compared to tamoxifen, Z-endoxifen markedly inhibited ERα target genes, Ki67 and Akt expression in vivo.

Conclusion: In endocrine-sensitive and letrozole-resistant breast tumors, Z-endoxifen results in robust antitumor and antiestrogenic activity compared to tamoxifen and aromatase inhibitor monotherapy. These data support the ongoing development of Z-endoxifen.
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http://dx.doi.org/10.1186/s13058-020-01286-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7238733PMC
May 2020

The transcription factor GLI1 cooperates with the chromatin remodeler SMARCA2 to regulate chromatin accessibility at distal DNA regulatory elements.

J Biol Chem 2020 06 6;295(26):8725-8735. Epub 2020 May 6.

Schulze Center for Novel Therapeutics, Division of Oncology Research, Schulze Center for Novel Therapeutics, Rochester, Minnesota, USA

The transcription factor GLI1 (GLI family zinc finger 1) plays a key role in the development and progression of multiple malignancies. To date, regulation of transcriptional activity at target gene promoters is the only molecular event known to underlie the oncogenic function of GLI1. Here, we provide evidence that GLI1 controls chromatin accessibility at distal regulatory regions by modulating the recruitment of SMARCA2 (SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily A, member 2) to these elements. We demonstrate that SMARCA2 endogenously interacts with GLI1 and enhances its transcriptional activity. Mapping experiments indicated that the C-terminal transcriptional activation domain of GLI1 and SMARCA2's central domains, including its ATPase motif, are required for this interaction. Interestingly, similar to SMARCA2, GLI1 overexpression increased chromatin accessibility, as indicated by results of the micrococcal nuclease assay. Further, results of assays for transposase-accessible chromatin with sequencing (ATAC-seq) after GLI1 knockdown supported these findings, revealing that GLI1 regulates chromatin accessibility at several regions distal to gene promoters. Integrated RNA-seq and ATAC-seq data analyses identified a subset of differentially expressed genes located in to these regulated chromatin sites. Finally, using the GLI1-regulated gene () as a model, we demonstrate that GLI1 and SMARCA2 co-occupy a distal chromatin peak and that SMARCA2 recruitment to this HHIP putative enhancer requires intact GLI1. These findings provide insights into how GLI1 controls gene expression in cancer cells and may inform approaches targeting this oncogenic transcription factor to manage malignancies.
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http://dx.doi.org/10.1074/jbc.RA120.013268DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7324497PMC
June 2020

The extracellular sulfatase SULF2 promotes liver tumorigenesis by stimulating assembly of a promoter-looping GLI1-STAT3 transcriptional complex.

J Biol Chem 2020 02 27;295(9):2698-2712. Epub 2020 Jan 27.

Schulze Center for Novel Therapeutics, Mayo Clinic, Rochester, Minnesota 55902

The expression of the extracellular sulfatase SULF2 has been associated with increased hepatocellular carcinoma (HCC) growth and poor patient survival. However, the molecular mechanisms underlying SULF2-associated tumor growth remain unclear. To address this gap, here we developed a transgenic mouse overexpressing in hepatocytes under the control of the transthyretin promoter. In this model, overexpression potentiated diethylnitrosamine-induced HCC. Further analysis indicated that the transcription factor GLI family zinc finger 1 (GLI1) mediates expression during HCC development. A cross of the -overexpressing with -knockout mice revealed that inactivation impairs SULF2-induced HCC. Transcriptomic analysis revealed that overexpression is associated with signal transducer and activator of transcription 3 (STAT3)-specific gene signatures. Interestingly, the knockout abrogated SULF2-mediated induction of several STAT3 target genes, including suppressor of cytokine signaling 2/3 (); Pim-1 proto-oncogene, Ser/Thr kinase (); and Fms-related tyrosine kinase 4 (). Human orthologs were similarly regulated by SULF2, dependent on intact GLI1 and STAT3 functions in HCC cells. SULF2 overexpression promoted a GLI1-STAT3 interaction and increased GLI1 and STAT3 enrichment at the promoters of their target genes. Interestingly, the SULF2 overexpression resulted in GLI1 enrichment at select STAT3 consensus sites, and vice versa. siRNA-mediated STAT3 or GLI1 knockdown reduced promoter binding of GLI1 and STAT3, respectively. Finally, chromatin-capture PCR confirmed long-range co-regulation of SOCS2 and FLT3 through changes in promoter conformation. These findings define a mechanism whereby SULF2 drives HCC by stimulating formation of a GLI1-STAT3 transcriptional complex.
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http://dx.doi.org/10.1074/jbc.RA119.011146DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7049957PMC
February 2020

A Phase II Study of Alisertib in Children with Recurrent/Refractory Solid Tumors or Leukemia: Children's Oncology Group Phase I and Pilot Consortium (ADVL0921).

Clin Cancer Res 2019 06 18;25(11):3229-3238. Epub 2019 Feb 18.

Dana-Farber/Boston Children's Cancer and Blood Disorders Center, Boston, Massachusetts.

Purpose: Aurora A kinase (AAK) plays an integral role in mitotic entry, DNA damage checkpoint recovery, and centrosome and spindle maturation. Alisertib (MLN8237) is a potent and selective AAK inhibitor. In pediatric preclinical models, antitumor activity was observed in neuroblastoma, acute lymphoblastic leukemia, and sarcoma xenografts. We conducted a phase 2 trial of alisertib in pediatric patients with refractory or recurrent solid tumors or acute leukemias (NCT01154816).

Patients And Methods: Alisertib (80 mg/m/dose) was administered orally, daily for 7 days every 21 days. Pharmacogenomic (PG) evaluation for polymorphisms in the AURK gene and drug metabolizing enzymes (UGT1A1*28), and plasma pharmacokinetic studies (PK) were performed. Using a 2-stage design, patients were enrolled to 12 disease strata (10 solid tumor and 2 acute leukemia). Response was assessed after cycle 1, then every other cycle.

Results: A total of 139 children and adolescents (median age, 10 years) were enrolled, 137 were evaluable for response. Five objective responses were observed (2 complete responses and 3 partial responses). The most frequent toxicity was myelosuppression. The median alisertib trough concentration on day 4 was 1.3 μmol/L, exceeding the 1 μmol/L target trough concentration in 67% of patients. No correlations between PG or PK and toxicity were observed.

Conclusions: Despite alisertib activity in pediatric xenograft models and cogent pharmacokinetic-pharmacodynamic relationships in preclinical models and adults, the objective response rate in children and adolescents receiving single-agent alisertib was less than 5%.
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http://dx.doi.org/10.1158/1078-0432.CCR-18-2675DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6897379PMC
June 2019

Pharmacokinetics of dacarbazine (DTIC) in pregnancy.

Cancer Chemother Pharmacol 2018 03 5;81(3):455-460. Epub 2018 Jan 5.

Department of Pharmacy, University of Washington, 1959 NE Pacific Street, Seattle, WA, 98195, USA.

Purpose: The purpose of this report is to describe, for the first time, the pharmacokinetics of dacarbazine (DTIC) and its metabolites [5-[3-methyl-triazen-1-yl]-imidazole-4-carboxamide (MTIC), 5-[3-hydroxymethyl-3-methyl-triazen-1-yl]-imidazole-4-carboxamide (HMMTIC) and 5-aminoimidazole-4-carboxamide (AIC)] during pregnancy (n = 2) and postpartum (n = 1).

Methods: Non-compartmental DTIC, MTIC, HMMTIC, and AIC pharmacokinetics (PK) were estimated in one case at 29 week gestation and 18 day postpartum and a second case at 32 week gestation, in women receiving DTIC in combination with doxorubicin, bleomycin, and vinblastine for treatment of Hodgkin's lymphoma. Drug concentrations were measured by HPLC.

Results: In the subject who completed both pregnancy and postpartum study days, DTIC area under the concentration-time curve (AUC) was 27% higher and metabolite AUCs were lower by 27% for HMMTIC, 38% for MTIC, and 83% of AIC during pregnancy compared to postpartum. At 7 and 9 year follow-up, both subjects were in remission of their Hodgkin's lymphoma.

Conclusions: Based on these two case reports, pregnancy appears to decrease the metabolism of the pro-drug dacarbazine, likely through inhibition of CYP1A2 activity. Lower concentrations of active metabolites and decreased efficacy may result, although both these subjects experienced long-term remission of their Hodgkin's lymphoma.
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http://dx.doi.org/10.1007/s00280-017-3511-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5828904PMC
March 2018

First-in-Human Phase I Study of the Tamoxifen Metabolite Z-Endoxifen in Women With Endocrine-Refractory Metastatic Breast Cancer.

J Clin Oncol 2017 Oct 30;35(30):3391-3400. Epub 2017 Aug 30.

Matthew P. Goetz, Vera J. Suman, Joel M. Reid, Don W. Northfelt, Michael A. Mahr, Andrew T. Ralya, Mary Kuffel, Sarah A. Buhrow, Stephanie L. Safgren, Renee M. McGovern, John Black, Travis Dockter, Tufia Haddad, Charles Erlichman, Alex A. Adjei, Dan Visscher, Benjamin R. Kipp, Minetta C. Liu, John R. Hawse, Matthew M. Ames, and James N. Ingle, Mayo Clinic, Rochester, MN; Zachary R. Chalmers and Garrett Frampton, Foundation Medicine, Cambridge, MA; and John R. Hawse, James H. Doroshow, Jerry M. Collins, and Howard Streicher, National Cancer Institute, Bethesda, MD.

Purpose Endoxifen is a tamoxifen metabolite with potent antiestrogenic activity. Patients and Methods We performed a phase I study of oral Z-endoxifen to determine its toxicities, maximum tolerated dose (MTD), pharmacokinetics, and clinical activity. Eligibility included endocrine-refractory, estrogen receptor-positive metastatic breast cancer. An accelerated titration schedule was applied until moderate or dose-limiting toxicity occurred, followed by a 3+3 design and expansion at 40, 80, and 100 mg per day. Tumor DNA from serum (circulating cell free [cf); all patients] and biopsies [160 mg/day and expansion]) was sequenced. Results Of 41 enrolled patients, 38 were evaluable for MTD determination. Prior endocrine regimens during which progression occurred included aromatase inhibitor (n = 36), fulvestrant (n = 21), and tamoxifen (n = 15). Patients received endoxifen once daily at seven dose levels (20 to 160 mg). Dose escalation ceased at 160 mg per day given lack of MTD and endoxifen concentrations > 1,900 ng/mL. Endoxifen clearance was unaffected by CYP2D6 genotype. One patient (60 mg) had cycle 1 dose-limiting toxicity (pulmonary embolus). Overall clinical benefit rate (stable > 6 months [n = 7] or partial response by RECIST criteria [n = 3]) was 26.3% (95% CI, 13.4% to 43.1%) including prior tamoxifen progression (n = 3). cfDNA mutations were observed in 13 patients ( PIK3CA [n = 8], ESR1 [n = 5], TP53 [n = 4], and AKT [n = 1]) with shorter progression-free survival ( v those without cfDNA mutations; median, 61 v 132 days; log-rank P = .046). Clinical benefit was observed in those with ESR1 amplification (tumor; 80 mg/day) and ESR1 mutation (cfDNA; 160 mg/day). Comparing tumor biopsies and cfDNA, some mutations ( PIK3CA, TP53, and AKT) were undetected by cfDNA, whereas cfDNA mutations ( ESR1, TP53, and AKT) were undetected by biopsy. Conclusion In endocrine-refractory metastatic breast cancer, Z-endoxifen provides substantial drug exposure unaffected by CYP2D6 metabolism, acceptable toxicity, and promising antitumor activity.
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http://dx.doi.org/10.1200/JCO.2017.73.3246DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5648176PMC
October 2017

Molecular Modeling and Functional Analysis of Exome Sequencing-Derived Variants of Unknown Significance Identify a Novel, Constitutively Active FGFR2 Mutant in Cholangiocarcinoma.

JCO Precis Oncol 2017 1;2017. Epub 2017 Aug 1.

David L. Marks, Tara L. Hogenson, Anne M. Vrabel, Ashley N. Sigafoos, Ezequiel J. Tolosa, Ryan M. Carr, Stephanie L. Safgren, Elisa Enriquez Hesles, Luciana L. Almada, Paola A. Romecin-Duran, Eriko Iguchi, Aryan Ala'Aldeen, Jean-Pierre A. Kocher, Gavin R. Oliver, Naresh Prodduturi, David W. Mead, Asif Hossain, Norine E. Huneke, Colleen M. Tagtow, Sikander Ailawadhi, Stephen M. Ansell, Michaela S. Banck, Asher A. Chanan-Khan, Ronald S. Go, Thorvardur R. Halfdanarson, Richard W. Joseph, Prashant Kapoor, Aaron S. Mansfield, Amulya A. Nageswara Rao, Grzegorz S. Nowakowski, Animesh Pardanani, Sameer A. Parikh, John C. Cheville, Andrew L. Feldman, Ramesh K. Ramanathan, Steven I. Robinson, Heidi D. Finnes, Jennifer B. McCormick, Robert R. McWilliams, Aminah Jatoi, Mrinal M. Patnaik, Eric D. Wieben, Tammy M. McAllister, Kandelaria M. Rumilla, Sarah E. Kerr, Konstantinos N. Lazaridis, Gianrico Farrugia, Karl J. Clark, Eric W. Klee, and Martin E. Fernandez-Zapico, Mayo Clinic, Rochester; Ernesto Resnik, Bio-Techne, Minneapolis, MN; Sikander Ailawadhi, Asher A. Chanan-Khan, and Richard W. Joseph, Mayo Clinic, Jacksonville, FL; Jan B. Egan, Alan H. Bryce, Estrella M. Carballido, KellyK. Curtis, Chelsea D. Gawryletz, Thai H. Ho,Nathalie Meurice, Ramesh K. Ramanathan, Raoul Tibes, Alvin C. Silva, A. Keith Stewart, and Mitesh J. Borad, Mayo Clinic, Phoenix, AZ; and Eileen J. Kennedy, University of Georgia, Athens, GA.

Purpose: Genomic testing has increased the quantity of information available to oncologists. Unfortunately, many identified sequence alterations are variants of unknown significance (VUSs), which thus limit the clinician's ability to use these findings to inform treatment. We applied a combination of in silico prediction and molecular modeling tools and laboratory techniques to rapidly define actionable VUSs.

Materials And Methods: Exome sequencing was conducted on 308 tumors from various origins. Most single nucleotide alterations within gene coding regions were VUSs. These VUSs were filtered to identify a subset of therapeutically targetable genes that were predicted with in silico tools to be altered in function by their variant sequence. A subset of receptor tyrosine kinase VUSs was characterized by laboratory comparison of each VUS versus its wild-type counterpart in terms of expression and signaling activity.

Results: The study identified 4,327 point mutations of which 3,833 were VUSs. Filtering for mutations in genes that were therapeutically targetable and predicted to affect protein function reduced these to 522VUSs of interest, including a large number of kinases. Ten receptortyrosine kinase VUSs were selected to explore in the laboratory. Of these, seven were found to be functionally altered. Three VUSs (FGFR2 F276C, FGFR4 R78H, and KDR G539R) showed increased basal or ligand-stimulated ERK phosphorylation compared with their wild-type counterparts, which suggests that they support transformation. Treatment of a patient who carried FGFR2 F276C with an FGFR inhibitor resulted in significant and sustained tumor response with clinical benefit.

Conclusion: The findings demonstrate the feasibility of rapid identification of the biologic relevance of somatic mutations, which thus advances clinicians' ability to make informed treatment decisions.
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http://dx.doi.org/10.1200/PO.17.00018DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6369924PMC
August 2017

Pancreatic Cancer, A Mis-interpreter of the Epigenetic Language.

Yale J Biol Med 2016 12 23;89(4):575-590. Epub 2016 Dec 23.

Schulze Center for Novel Therapeutics, Mayo Clinic, Rochester, MN, USA.

Pancreatic cancer is the third leading cause of cancer mortality in the U.S. with close to 40,000 deaths per year. Pancreatic ductal adenocarcinoma (PDAC) represents approximately 90 percent of all pancreatic cancer cases and is the most lethal form of the disease. Current therapies for PDAC are ineffective and most patients cannot be treated by surgical resection. Most research efforts have primarily focused on how genetic alterations cause, alter progression, contribute to diagnosis, and influence PDAC management. Over the past two decades, a model has been advanced of PDAC initiation and progression as a multi-step process driven by the acquisition of mutations leading to loss of tumor suppressors and activation of oncogenes. The recognition of the essential roles of these genetic alterations in the development of PDAC has revolutionized our knowledge of this disease. However, none of these findings have turned into effective treatment for this dismal malignancy. In recent years, studies in the areas of chromatin modifications, and non-coding RNAs have uncovered mechanisms for regulating gene expression which occur independently of genetic alterations. Chromatin-based mechanisms are interwoven with microRNA-driven regulation of protein translation to create an integrated epigenetic language, which is grossly dysregulated in PDAC. Thus in PDAC, key tumor suppressors that are well established to play a role in PDAC may be repressed, and oncogenes can be upregulated secondary to epigenetic alterations. Unlike mutations, epigenetic changes are potentially reversible. Given this feature of epigenetic mechanisms, it is conceivable that targeting epigenetic-based events promoting and maintaining PDAC could serve as foundation for the development of new therapeutic and diagnostic approaches for this disease.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5168833PMC
December 2016

Evaluation of CYP2D6 enzyme activity using a 13C-dextromethorphan breath test in women receiving adjuvant tamoxifen.

Pharmacogenet Genomics 2015 Apr;25(4):157-63

Departments of aOncology bMolecular Pharmacology and Experimental Therapeutics cBiostatistics dLaboratory Medicine, Mayo Clinic, Rochester, Minnesota eDepartment of Hematology and Oncology, Mayo Clinic, Scottsdale, Arizona fCambridge Isotope Laboratories Inc. gPhysical Sciences Inc., Andover, Massachusetts, USA.

Background: In tamoxifen-treated patients, breast cancer recurrence differs according to CYP2D6 genotype and endoxifen steady-state concentrations (Endx Css). The ¹³C-dextromethorphan breath test (DM-BT), labeled with ¹³C at the O-CH3 moiety, measures CYP2D6 enzyme activity. We sought to examine the ability of the DM-BT to identify known CYP2D6 genotypic poor metabolizers and examine the correlation between DM-BT and Endx Css.

Methods: DM-BT and tamoxifen pharmacokinetics were obtained at baseline, 3, and 6 months following tamoxifen initiation. Potent CYP2D6 inhibitors were prohibited. The correlation between baseline DM-BT with CYP2D6 genotype and Endx Css was determined. The association between baseline DM-BT (where values ≤0.9 is an indicator of poor in vivo CYP2D6 metabolism) and Endx Css (using values≤11.2 known to be associated with poorer recurrence free survival) was explored.

Results: A total of 91 patients were enrolled and 77 were eligible. CYP2D6 genotype was positively correlated with baseline, 3, and 6 months DM-BT (r ranging from 0.457-0. 60; P<0.001). Both CYP2D6 genotype (r=0.47, 0.56, P<0.0001), and baseline DM-BT (r=0.60, 0.54, P<0.001) were associated with 3 and 6 months Endx Css, respectively. Seven (78%) of nine patients with low (≤11.2 nmol/l) 3 month Endx Css also had low DM-BT (≤0.9) including 2/2 CYP2D6 PM/PM and 5/5 IM/PM. In contrast, one (2%) of 48 patients with a low DM-BT had Endx Css more than 11.2 nmol/l.

Conclusion: In patients not taking potent CYP2D6 inhibitors, DM-BT was associated with CYP2D6 genotype and 3 and 6 months Endx Css but did not provide better discrimination of Endx Css compared with CYP2D6 genotype alone. Further studies are needed to identify additional factors which alter Endx Css.
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http://dx.doi.org/10.1097/FPC.0000000000000121DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4356640PMC
April 2015

Loss of heterozygosity at the CYP2D6 locus in breast cancer: implications for germline pharmacogenetic studies.

J Natl Cancer Inst 2014 Dec 8;107(2). Epub 2014 Dec 8.

Department of Oncology (MPG, MMA, JNI), Department of Health Sciences Research (VJS, KRK), and Department of Molecular Pharmacology and Experimental Therapeutics (MPG, SLS, MK, MMA), Mayo Clinic, Rochester, MN; Department of Genetics, University of North Carolina, Chapel Hill, NC (GOS, CMP); Center for Personalized Therapeutics, University of Chicago, Chicago, IL (YN, NJC, MJR); Foundation Medicine Inc., Cambridge, MA (JXS, PJS, VAM, JSR, RY); Novartis Pharmaceuticals Corporation, East Hanover, NJ (DC); Department of Pathology and Laboratory Medicine, Albany Medical College, Albany, NY (JSR); Division of Hematology/Oncology, Vanderbilt University, Nashville, TN (HG); Department of Breast Medical Oncology, University of Texas MD Anderson Cancer Center, Houston, TX (AMGA, OB); Department Breast Cancer Susceptibility and Pharmacogenomics, Dr Margarete Fischer-Bosch-Institute of Clinical Pharmacology, Stuttgart, University Tuebingen, German Cancer Consortium (DKTK) and German Cancer Research (DKTK), Heidelberg, Germany (HB).Current affiliation of H. Gomez: Departamento de Medicina Oncologica, Instituto Nacional de Enfermedades Neoplasicas, Lima, Peru.

Background: Controversy exists regarding the impact of CYP2D6 genotype on tamoxifen responsiveness. We examined loss of heterozygosity (LOH) at the CYP2D6 locus and determined its impact on genotyping error when tumor tissue is used as a DNA source.

Methods: Genomic tumor data from the adjuvant and metastatic settings (The Cancer Genome Atlas [TCGA] and Foundation Medicine [FM]) were analyzed to characterize the impact of CYP2D6 copy number alterations (CNAs) and LOH on Hardy Weinberg equilibrium (HWE). Additionally, we analyzed CYP2D6 *4 genotype from formalin-fixed paraffin-embedded (FFPE) tumor blocks containing nonmalignant tissue and buccal (germline) samples from patients on the North Central Cancer Treatment Group (NCCTG) 89-30-52 tamoxifen trial. All statistical tests were two-sided.

Results: In TCGA samples (n =627), the CYP2D6 LOH rate was similar in estrogen receptor (ER)-positive (41.2%) and ER-negative (35.2%) but lower in HER2-positive tumors (15.1%) (P < .001). In FM ER+ samples (n = 290), similar LOH rates were observed (40.8%). In 190 NCCTG samples, the agreement between CYP2D6 genotypes derived from FFPE tumors and FFPE tumors containing nonmalignant tissue was moderate (weighted Kappa = 0.74; 95% CI = 0.63 to 0.84). Comparing CYP2D6 genotypes derived from buccal cells to FFPE tumor DNA, CYP2D6*4 genotype was discordant in six of 31(19.4%). In contrast, there was no disagreement between CYP2D6 genotypes derived from buccal cells with FFPE tumors containing nonmalignant tissue.

Conclusions: LOH at the CYP2D6 locus is common in breast cancer, resulting in potential misclassification of germline CYP2D6 genotypes. Tumor DNA should not be used to determine germline CYP2D6 genotype without sensitive techniques to detect low frequency alleles and quality control procedures appropriate for somatic DNA.
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http://dx.doi.org/10.1093/jnci/dju401DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4565524PMC
December 2014

Pharmacokinetics of endoxifen and tamoxifen in female mice: implications for comparative in vivo activity studies.

Cancer Chemother Pharmacol 2014 Dec 16;74(6):1271-8. Epub 2014 Oct 16.

Department of Oncology, Mayo Clinic, 200 First Street SW, Rochester, MN, 55905, USA.

Background: Reduced CYP2D6 metabolism and low Z-endoxifen (ENDX) concentrations may increase the risk of breast cancer recurrence in tamoxifen (TAM)-treated women. Little is known regarding the differences between TAM and ENDX murine pharmacokinetics or the effect of administration route on plasma concentrations of each drug.

Methods: The pharmacokinetics of TAM and ENDX were characterized in female mice.

Results: For subcutaneous [s.c.] and oral TAM (4, 10 and 20 mg/kg), TAM AUC increased in a linear manner, but concentrations of the active metabolites [ENDX and 4-hydroxytamoxifen (4HT)] remained low. For oral TAM (20 mg), 4HT concentrations were tenfold greater (>25 ng/ml) than achievable in TAM-treated humans. Both oral (10-200 mg/kg) and s.c. (2.5-25 mg/kg) ENDX·HCl resulted in a greater than dose-proportional increase in AUC, with eightfold greater ENDX concentrations than an equivalent TAM dose. ENDX accumulated in plasma after 5-day dosing of 25 or 100 mg/kg ENDX·HCl and exceeded target concentrations of 0.1 and 1.0 μM, respectively, by twofold to fourfold.

Conclusions: In murine models, oral ENDX yields substantially higher ENDX concentrations, compared to TAM. The low 4HT and ENDX concentrations observed in mice receiving s.c. TAM mirror the TAM pharmacokinetics in humans with impaired CYP2D6 metabolism. These data support the ongoing development of ENDX as a novel agent for the endocrine treatment of ER-positive breast cancer.
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http://dx.doi.org/10.1007/s00280-014-2605-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4343319PMC
December 2014

Comparative uterotrophic effects of endoxifen and tamoxifen in ovariectomized Sprague-Dawley rats.

Toxicol Pathol 2014 Dec 26;42(8):1188-96. Epub 2014 Mar 26.

Developmental Therapeutics Program, National Cancer Institute, Bethesda, Maryland, USA.

Endoxifen (4-hydroxy-N-desmethyl-tamoxifen), one of the major active metabolites of tamoxifen, has substantially greater estrogen antagonist properties and antiproliferative effects in breast tumor cells than tamoxifen, a mixed estrogen agonist/antagonist. An associated risk of endometrial cancer and hyperplasia has been linked to the estrogen agonist properties of tamoxifen. We evaluated endoxifen using a classic uterotrophic effects method. Rats were given endoxifen or tamoxifen orally for 3 days. Estradiol was the positive control. Endoxifen and tamoxifen plasma levels exceeded those previously observed clinically. Uterine weight was 3-fold higher in the estradiol group than in the tamoxifen or endoxifen groups, which did not differ from vehicle controls. Tamoxifen and endoxifen caused a greater increase in luminal epithelial cell height than estradiol. Both tamoxifen and endoxifen produced an increase in the stromal BrdU labeling index (LI) that was ≤ estradiol and inversely related to dose, but did not affect luminal epithelial cell BrdU LI. As expected, estradiol increased luminal epithelial cell proliferation. These results indicate that endoxifen induces uterotrophic effects, but is less potent than estradiol in eliciting these effects. Given prior preclinical observations that endoxifen has superior antitumor activity than tamoxifen, the observations of similar uterine effects suggest that the endoxifen risk/benefit ratio may be superior to tamoxifen.
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http://dx.doi.org/10.1177/0192623314525688DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4177029PMC
December 2014

UGT1A1 genotype-guided phase I study of irinotecan, oxaliplatin, and capecitabine.

Invest New Drugs 2013 Dec 10;31(6):1559-67. Epub 2013 Oct 10.

Department of Oncology, Mayo Clinic, Rochester, MN.

Purpose: We performed a UGT1A1 genotype-guided study to determine the maximum tolerated dose (MTD) and evaluate the toxicities and pharmacokinetics of the combination of capecitabine (CAP), oxaliplatin (OX), and irinotecan (IRIN).

Experimental Design: Patients were screened for UGT1A1 *28 genotype prior to treatment. The starting dose (mg/m(2)) was IRIN (150), OX (85) and CAP (400), days 2-15. Doses were escalated or de-escalated within each genotype group (*28/*28, *1/*28 and *1/*1). IRIN pharmacokinetics was performed at the MTD.

Results: 50 patients were evaluable for toxicity [11 (*28/*28); 18 (*1/*28); 21 (*1/*1)]. UGT1A1 *28/*28 patients experienced hematologic dose limiting toxicity (DLT), requiring dose-de-escalation. The UGT1A1 *28/*28 recommended phase 2 dose (RP2D) was IRIN (75), OX (85), and CAP (400). In contrast, both UGT1A1 *1/*28 and *1/*1 tolerated higher doses of IRIN and non-hematologic toxicity was dose limiting for UGT1A1 *1/*1. The RP2D was IRIN (150), OX (85), and CAP (400) for UGT1A1*1/*28 and IRIN (150), OX (100), and CAP (1600) for UGT1A1 *1/*1. UGT1A1 *1/*28 and *1/*1 patients treated with IRIN (150) had similar AUCs for the active irinotecan metabolite, SN38 (366 +/- 278 and 350 +/- 159 ng/ml*hr, respectively). UGT1A1 *28/*28 patients (n = 3) treated with a lower IRIN dose (100) had non-significantly higher mean SN38 exposures (604 +/- 289 ng/ml*hr, p = 0.14). Antitumor activity was observed in all genotype groups.

Conclusions: UGT1A1 genotype affects the dose and pharmacokinetics of the CAPIRINOX regimen and UGT1A1 genotype-guided dosing of CAPIRINOX is ongoing in a phase II study of small bowel cancer (NCT00433550).
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http://dx.doi.org/10.1007/s10637-013-0034-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3880122PMC
December 2013

CYP2D6 metabolism and patient outcome in the Austrian Breast and Colorectal Cancer Study Group trial (ABCSG) 8.

Clin Cancer Res 2013 Jan 4;19(2):500-7. Epub 2012 Dec 4.

Department of Oncology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA.

Purpose: Controversy exists about CYP2D6 genotype and tamoxifen efficacy.

Experimental Design: A matched case-control study was conducted using the Austrian Breast and Colorectal Cancer Study Group Trial 8 (ABCSG8) that randomized postmenopausal women with estrogen receptor (ER)-positive breast cancer to tamoxifen for 5 years (arm A) or tamoxifen for 2 years followed by anastrozole for 3 years (arm B). Cases had disease recurrence, contralateral breast cancer, second non-breast cancer, or died. For each case, controls were identified from the same treatment arm of similar age, surgery/radiation, and tumor-node-metastasis (TNM) stage. Genotyping was conducted for alleles associated with no (PM; *3, *4, *6), reduced (IM; *10, and *41), and extensive (EM: absence of these alleles) CYP2D6 metabolism.

Results: The common CYP2D6*4 allele was in Hardy-Weinberg equilibrium. In arm A during the first 5 years of therapy, women with two poor alleles [PM/PM: OR, 2.45; 95% confidence interval (CI), 1.05-5.73, P = 0.04] and women with one poor allele (PM/IM or PM/EM: OR, 1.67; 95% CI, 0.95-2.93; P = 0.07) had a higher likelihood of an event than women with two extensive alleles (EM/EM). In years 3 to 5 when patients remained on tamoxifen (arm A) or switched to anastrozole (arm B), PM/PM tended toward a higher likelihood of a disease event relative to EM/EM (OR, 2.40; 95% CI, 0.86-6.66; P = 0.09) among women on arm A but not among women on arm B (OR, 0.28; 95% CI, 0.03-2.30).

Conclusion: In ABCSG8, the negative effects of reduced CYP2D6 metabolism were observed only during the period of tamoxifen administration and not after switching to anastrozole.
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http://dx.doi.org/10.1158/1078-0432.CCR-12-2153DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3548984PMC
January 2013

Gemcitabine and irinotecan as first-line therapy for carcinoma of unknown primary: results of a multicenter phase II trial.

PLoS One 2012 17;7(7):e39285. Epub 2012 Jul 17.

Mayo Clinic Rochester, Rochester, Minnesota, United States of America.

Unlabelled: Metastatic carcinoma of unknown primary (CUP) has a very poor prognosis, and no standard first-line therapy currently exists. Here, we report the results of a phase II study utilizing a combination of gemcitabine and irinotecan as first-line therapy. Treatment was with gemcitabine 1000 mg/m(2) and irinotecan 75 mg/m(2) weekly times four on a six week cycle (Cohort I). Due to excessive toxicity, the dose and schedule were modified as follows: gemcitabine 750 mg/m(2) and irinotecan 75 mg/m(2) given weekly times three on a four week cycle (Cohort II). The primary endpoint was the confirmed response rate (CR + PR). Secondary endpoints consisted of adverse events based upon the presence or absence of the UDP glucuronosyltransferase 1 family, polypeptide A1*28 (UGT1A1*28) polymorphism, time to progression, and overall survival. Thirty-one patients were enrolled with a median age of 63 (range: 38-94), and 26 patients were evaluable for efficacy. Significant toxicity was observed in Cohort 1, characterized by 50% (7/14) patients experiencing a grade 4+ adverse event, but not in cohort II. The confirmed response rate including patients from both cohorts was 12% (95% CI: 2-30%), which did not meet the criteria for continued enrollment. Overall median survival was 7.2 months (95% CI: 4.0 to 11.6) for the entire cohort but notably longer in cohort II than in cohort I (9.3 months (95% CI: 4.1 to 12.1) versus 4.0 months (95% CI: 2.2 to 15.6)). Gemcitabine and irinotecan is not an active combination when used as first line therapy in patients with metastatic carcinoma of unknown primary. Efforts into developing novel diagnostic and therapeutic approaches remain important for improving the outlook for this heterogeneous group of patients.

Trial Registration: ClinicalTrials.gov NCT00066781.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0039285PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3398897PMC
March 2013

Phase 2 trial of pemetrexed in children and adolescents with refractory solid tumors: a Children's Oncology Group study.

Pediatr Blood Cancer 2013 Feb 28;60(2):237-41. Epub 2012 Jun 28.

Uniformed Services University of the Health Sciences, Bethesda, MD 20814, USA.

Background: Pemetrexed is a multi-targeted antifolate that inhibits key enzymes involved in nucleotide biosynthesis. We performed a phase 2 trial of pemetrexed in children with refractory or recurrent solid tumors, including CNS tumors, to estimate the response rate and further define its toxicity profile.

Procedure: Pemetrexed, at a dose of 1910 mg/m(2) , was administered as a 10-minute intravenous infusion every 21 days. Patients also received vitamin B(12) , daily multivitamin supplementation, and dexamethasone. A two-stage design (10 + 10) was employed in each of the following disease strata: osteosarcoma, Ewing sarcoma/peripheral primitive neuroectodermal tumor (PNET), rhabdomyosarcoma, neuroblastoma, ependymoma, medulloblastoma/supratentorial PNET, and non-brainstem high-grade glioma.

Results: Seventy-two eligible subjects (39 males) were enrolled. Median age was 11 years (range 3-23). Sixty-eight were evaluable for response. The median number of cycles administered was 2 (range 1-13). No complete or partial responses were observed. Stable disease, for a median of 5 (range 4-13) cycles, was observed in five patients (ependymoma, Ewing sarcoma, medulloblastoma, neuroblastoma, osteosarcoma; n = 1 each). Neutropenia (44%), anemia (35%), and elevated alanine transaminase (35%) attributable to pemetrexed were the most commonly recurring toxicities observed in patients receiving multiple cycles. Other toxicities attributed to pemetrexed occurring in ≥10% of cycles included thrombocytopenia (30%), fatigue (18%), nausea (14), hyperglycemia (13%), rash (11%), vomiting (13%), and hypophosphatemia (11%).

Conclusions: Pemetrexed, administered as an intravenous infusion every 21 days, was tolerable in children and adolescents with refractory solid tumors, including CNS tumors, but did not show evidence of objective anti-tumor activity in the childhood tumors studied.
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http://dx.doi.org/10.1002/pbc.24244DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3463652PMC
February 2013

SULT1A1, CYP2C19 and disease-free survival in early breast cancer patients receiving tamoxifen.

Pharmacogenomics 2011 Nov 3;12(11):1535-43. Epub 2011 Oct 3.

Mayo Clinic, Rochester, MN 55905, USA.

Aim: Tamoxifen biotransformation to endoxifen, a potent antiestrogen, is catalyzed by CYP2D6. In addition, CYP2C19 and SULT1A1 have also been implicated in the metabolism of tamoxifen. We sought to evaluate the importance of SULT1A1 copy number and CYP2C19*17 on disease-free survival (DFS) in postmenopausal women randomized to tamoxifen monotherapy in North Central Cancer Treatment Group 89-30-52 from January 1991 to April 1995.

Materials & Methods: We extracted DNA from paraffin-embedded tumors and determined tumor SULT1A1 copy number and CYP2C19*17 genotype. The association of genotype with DFS was determined using the log-rank test. Multivariate cox modeling was performed using traditional prognostic factors, as well as CYP2D6 genotype. SULT1A1 copy number and CYP2C19*17 genotype was determined in 190 out of 256 patients (95% Caucasian).

Results: The median follow-up for living patients was 14 years. DFS did not differ according to SULT1A1 copy number (p = 0.482) or CYP2C19*17 genotype (p = 0.667). Neither SULT1A1 copy number or CYP2C19*17 genotype was associated with disease recurrence in this cohort.

Conclusion: Future studies are needed to identify whether other genetic and environmental factors which affect tamoxifen metabolism are associated with tamoxifen clinical outcomes.
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http://dx.doi.org/10.2217/pgs.11.97DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3235041PMC
November 2011

Phase II NCCTG trial of RT + irinotecan and adjuvant BCNU plus irinotecan for newly diagnosed GBM.

J Neurooncol 2010 Aug 9;99(1):73-80. Epub 2010 Jan 9.

Mayo Clinic Florida, 4500 San Pablo Road, Jacksonville, FL 32224, USA.

Irinotecan has radiosensitizing effects and shows synergism with nitrosoureas. We performed a Phase II study of RT and irinotecan, followed by BCNU plus irinotecan in newly-diagnosed GBM. The MTD for patients receiving enzyme-inducing anticonvulsants (EIAC) was as follows: irinotecan 400 mg/m(2)/week on Days 1, 8, 22 and 29 during RT, followed by BCNU 100 mg/m(2) Day 1, and irinotecan, 400 mg/m(2) on Days 1, 8, 22 and 29, every 6 weeks. The MTD for non-EIAC patients was as follows: irinotecan 125 mg/m(2)/week on Days 1, 8, 22 and 29 during RT, followed by BCNU 100 mg/m(2) Day 1 and irinotecan 75 mg/m(2) Days 1, 8, 22 and 29, every 6 weeks. Median OS was 10.8 mos. (95% CI: 7.7-14.9); OS at 12 months was 44.6% (95% CI: 33.3-59.8) and PFS 6 was 28.6% (95% CI: 18.9-43.2). Patients went off treatment due to adverse events (7%), refusal (11%), progressive disease (48%), death (9%), and other (9%); 16% completed protocol treatment. Survival was similar in patients with variant (6/7 or 7/7) and wild-type (6/6) UGT1A1*28 genotypic alleles. Grade 3-4 toxicity was more common in non-EIAC patients with variant alleles. SN-38 C(max) and AUC in EIAC patients receiving 400 mg/m(2) irinotecan were 20.9 ng/ml and 212 ng/ml h, and in non-EIAC patients receiving 125 mg/m(2), 15.5 ng/ml and 207 ng/ml h. SN-38 AUC varied by UGT1A1*28 status in non-EIAC patients. This regimen was not significantly active and radiosensitization was not observed. Non-EIAC patients with UGT1A1*28 variant alleles appear particularly sensitive to toxicity from irinotecan.
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http://dx.doi.org/10.1007/s11060-009-0103-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2897141PMC
August 2010

Phase I trial of two schedules of vincristine, oral irinotecan, and temozolomide (VOIT) for children with relapsed or refractory solid tumors: a Children's Oncology Group phase I consortium study.

Pediatr Blood Cancer 2010 Apr;54(4):538-45

Division of Hematology/Oncology, Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA.

Background: In preclinical models, temozolomide, and vincristine are additive or synergistic with irinotecan. We examined this three-drug combination in children with relapsed solid tumors. Patients received orally administered irinotecan together with temozolomide and vincristine on two different schedules, using cefixime to reduce irinotecan-associated diarrhea.

Methods: Oral irinotecan was given daily on days 1-5 and 8-12 (Schedule A), or on days 1-5 (Schedule B). Temozolomide was given on days 1-5, with vincristine 1.5 mg/m(2) administered on days 1 and 8 (Schedule A) or day 1 (Schedule B) in 21-day courses.

Results: On Schedule A, the maximum tolerated dose of oral irinotecan was 35 mg/m(2)/day combined with temozolomide 100 mg/m(2)/day and vincristine on days 1 and 8. Dose-limiting toxicities in 4 of 12 patients included hepatotoxicity, abdominal pain, anorexia, hypokalemia, and thrombocytopenia at 50 mg/m(2)/day. Using Schedule B, 0 of 6 patients experienced dose-limiting toxicity (DLT) at the highest doses studied of oral irinotecan 90 mg/m(2)/day, temozolomide 150 mg/m(2)/day x 5, and vincristine on day 1. First-course and cumulative toxicity was greater with Schedule A. UGT1A1*28 genotype did not correlate with DLT. At the irinotecan dose of 90 mg/m(2)/day, the mean SN-38 AUC(inf) was 63 ng/ml hr. Activity was seen in sarcoma patients, and overall eight patients received >or=6 courses.

Conclusions: The 5-day schedule of VOIT was well tolerated and provided SN-38 exposures similar to those achieved with intravenous IRN. Activity on this and prior studies suggests a potential role for VOIT in a spectrum of childhood solid tumors.
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http://dx.doi.org/10.1002/pbc.22407DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3074342PMC
April 2010

Association between CYP2D6 polymorphisms and outcomes among women with early stage breast cancer treated with tamoxifen.

JAMA 2009 Oct;302(13):1429-36

Dr Margarete Fischer-Bosch-Institute of Clinical Pharmacology, Auerbachstrasse 112, 70376 Stuttgart, Germany.

Context: The growth inhibitory effect of tamoxifen, which is used for the treatment of hormone receptor-positive breast cancer, is mediated by its metabolites, 4-hydroxytamoxifen and endoxifen. The formation of active metabolites is catalyzed by the polymorphic cytochrome P450 2D6 (CYP2D6) enzyme.

Objective: To determine whether CYP2D6 variation is associated with clinical outcomes in women receiving adjuvant tamoxifen.

Design, Setting, And Patients: Retrospective analysis of German and US cohorts of patients treated with adjuvant tamoxifen for early stage breast cancer. The 1325 patients had diagnoses between 1986 and 2005 of stage I through III breast cancer and were mainly postmenopausal (95.4%). Last follow-up was in December 2008; inclusion criteria were hormone receptor positivity, no metastatic disease at diagnosis, adjuvant tamoxifen therapy, and no chemotherapy. DNA from tumor tissue or blood was genotyped for CYP2D6 variants associated with reduced (*10, *41) or absent (*3, *4, *5) enzyme activity. Women were classified as having an extensive (n=609), heterozygous extensive/intermediate (n=637), or poor (n=79) CYP2D6 metabolism.

Main Outcome Measures: Time to recurrence, event-free survival, disease-free survival, and overall survival.

Results: Median follow-up was 6.3 years. At 9 years of follow-up, the recurrence rates were 14.9% for extensive metabolizers, 20.9% for heterozygous extensive/intermediate metabolizers, and 29.0% for poor metabolizers, and all-cause mortality rates were 16.7%, 18.0%, and 22.8%, respectively. Compared with extensive metabolizers, there was a significantly increased risk of recurrence for heterozygous extensive/intermediate metabolizers (time to recurrence adjusted hazard ratio [HR], 1.40; 95% confidence interval [CI], 1.04-1.90) and for poor metabolizers (time to recurrence HR, 1.90; 95% CI, 1.10-3.28). Compared with extensive metabolizers, those with decreased CYP2D6 activity (heterozygous extensive/intermediate and poor metabolism) had worse event-free survival (HR, 1.33; 95% CI, 1.06-1.68) and disease-free survival (HR, 1.29; 95% CI, 1.03-1.61), but there was no significant difference in overall survival (HR, 1.15; 95% CI, 0.88-1.51).

Conclusion: Among women with breast cancer treated with tamoxifen, there was an association between CYP2D6 variation and clinical outcomes, such that the presence of 2 functional CYP2D6 alleles was associated with better clinical outcomes and the presence of nonfunctional or reduced-function alleles with worse outcomes.
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http://dx.doi.org/10.1001/jama.2009.1420DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3909953PMC
October 2009

Overcoming S-phase checkpoint-mediated resistance: sequence-dependent synergy of gemcitabine and 7-ethyl-10-hydroxycamptothecin (SN-38) in human carcinoma cell lines.

Mol Pharmacol 2008 Sep 28;74(3):724-35. Epub 2008 May 28.

Division of Oncology Research and Department of Molecular Pharmacology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA.

Although agents that inhibit DNA synthesis are widely used in the treatment of cancer, the optimal method for combining such agents and the mechanism of their synergy is poorly understood. The present study examined the effects of combining gemcitabine (2',2'-difluoro 2'-deoxycytidine) and 7-ethyl-10-hydroxycamptothecin (SN-38; the active metabolite of irinotecan), two S-phaseselective agents that individually have broad antitumor activity, in human cancer cells in vitro. Colony-forming assays revealed that simultaneous treatment of Ovcar-5 ovarian cancer cells or BxPC-3 pancreatic cancer cells with gemcitabine and SN-38 resulted in antagonistic effects. In contrast, sequential treatment with these two agents in either order resulted in synergistic anti-proliferative effects, although the mechanism of synergy varied with the sequence. In particular, SN-38 arrested cells in S phase, enhanced the accumulation of gemcitabine metabolites, and diminished checkpoint kinase 1, thereby sensitizing cells in the SN-38 --> gemcitabine sequence. Gemcitabine treatment followed by removal allowed prolonged progression through S phase, contributing to synergy of the gemcitabine --> SN-38 sequence. These results collectively suggest that S-phase-selective agents might exhibit more cytotoxicity when administered sequentially rather than simultaneously.
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http://dx.doi.org/10.1124/mol.108.047787DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2574763PMC
September 2008

Targeted delivery of gemcitabine to pancreatic adenocarcinoma using cetuximab as a targeting agent.

Cancer Res 2008 Mar;68(6):1970-8

Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905, USA.

One of the key challenges in anticancer therapy is the toxicity and poor bioavailability of the anticancer drugs. Nanotechnology can play a pivotal role by delivering drugs in a targeted fashion to the malignant cells that will reduce the systemic toxicity of the anticancer drug. In this report, we show a stepwise development of a nanoparticle-based targeted delivery system for in vitro and in vivo therapeutic application in pancreatic cancer. In the first part of the study, we have shown the fabrication and characterization of the delivery system containing gold nanoparticle as a delivery vehicle, cetuximab as a targeting agent, and gemcitabine as an anticancer drug for in vitro application. Nanoconjugate was first characterized physico-chemically. In vitro targeting efficacy, tested against three pancreatic cancer cell lines (PANC-1, AsPC-1, and MIA Paca2) with variable epidermal growth factor receptor (EGFR) expression, showed that gold uptake correlated with EGFR expression. In the second part, we showed the in vivo therapeutic efficacy of the targeted delivery system. Administration of this targeted delivery system resulted in significant inhibition of pancreatic tumor cell proliferation in vitro and orthotopic pancreatic tumor growth in vivo. Tumor progression was monitored noninvasively by measuring bioluminescence of the implanted tumor cells. Pharmacokinetic experiments along with the quantitation of gold both in vitro and in vivo further confirmed that the inhibition of tumor growth was due to targeted delivery. This strategy could be used as a generalized approach for the treatment of a variety of cancers characterized by overexpression of EGFR.
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http://dx.doi.org/10.1158/0008-5472.CAN-07-6102DOI Listing
March 2008

A phase I study of 17-allylaminogeldanamycin in relapsed/refractory pediatric patients with solid tumors: a Children's Oncology Group study.

Clin Cancer Res 2007 Mar;13(6):1789-93

University of Minnesota Cancer Center and Department of Pediatrics, University of Minnesota, Minneapolis, MN 55455, USA.

Purpose: To determine the recommended phase 2 dose, dose-limiting toxicities (DLT), pharmacokinetic profile, and pharmacodynamics of the heat shock protein (Hsp) 90 inhibitor, 17-allylaminogeldanamycin (17-AAG).

Experimental Design: 17-AAG was administered as a 60-min infusion, on days 1, 4, 8, and 11 of a 21-day cycle at dose levels of 150, 200, 270, and 360 mg/m(2)/dose. Pharmacokinetic studies and evaluations for Hsp72 and Akt levels in peripheral blood mononuclear cells were done during the first course of therapy.

Results: Seventeen patients (7 males), median 7 years of age (range, 1-19 years), were enrolled using a standard dose escalation scheme. No DLTs were observed. Although there were no objective responses, three patients remain on therapy at 6+, 7+, and 9+ months with stable disease. One patient with hepatoblastoma had a reduction in alpha-fetoprotein and stable disease over three cycles. At 270 mg/m(2)/dose, the C(max) and areas under the plasma concentration-time curves of 17-AAG were 5,303 +/- 1,591 ng/mL and 13,656 +/- 4,757 ng/mL h, respectively, similar to the exposure in adults. The mean terminal half-life for 17-AAG was 3.24 +/- 0.80 h. Induction of Hsp72, a surrogate marker for inhibition of Hsp90, was detected at the 270 mg/m(2) dose level.

Conclusions: Drug exposures consistent with those required for anticancer activity in preclinical models were achieved without DLT. Evidence for drug-induced modulation of Hsp90 systemically was also detected. The recommended phase II dose of 17-AAG is 360 mg/m(2)/d. Non-DMSO-containing formulations may improve acceptance of this drug by children and their families.
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http://dx.doi.org/10.1158/1078-0432.CCR-06-2270DOI Listing
March 2007

The impact of cytochrome P450 2D6 metabolism in women receiving adjuvant tamoxifen.

Breast Cancer Res Treat 2007 Jan 18;101(1):113-21. Epub 2006 Nov 18.

Department of Oncology, Mayo Clinic College of Medicine, 200 First Street Southwest, Rochester, MN , 55905, USA,

Background: Tamoxifen is biotransformed to the potent anti-estrogen, endoxifen, by the cytochrome P450 (CYP) 2D6 enzyme. CYP2D6 genetic variation and inhibitors of the enzyme markedly reduce endoxifen plasma concentrations in tamoxifen-treated patients. Using a North Central Cancer Treatment Group adjuvant tamoxifen trial, we performed a comprehensive evaluation of CYP2D6 metabolism by assessing the combined effect of genetic variation and inhibition of the enzyme system on breast cancer recurrence and death.

Methods: Medical records were reviewed at each randomizing site to determine whether CYP2D6 inhibitors were co-prescribed with tamoxifen. Extensive metabolizers were defined as patients without a *4 allele (i.e., wt/wt) who were not co-prescribed a CYP2D6 inhibitor. Patients with decreased CYP2D6 metabolism were classified as intermediate or poor metabolizers (PM) based on the presence of one or two CYP2D6*4 alleles or the co-administration of a moderate or potent CYP2D6 inhibitor. The association between CYP2D6 metabolism and clinical outcome was assessed using Cox modeling.

Results: Medication history was available in 225/256 eligible patients and CYP2D6*4 genotype in 190 patients. Thirteen patients (6%) were co-prescribed a CYP2D6 inhibitor [potent (n = 3), moderate (n = 10)], resulting in the following CYP2D6 metabolism: extensive (n = 115) and decreased (n = 65). In the multivariate analysis, patients with decreased metabolism had significantly shorter time to recurrence (p = 0.034; adj HR = 1.91; 95% CI 1.05-3.45) and worse relapse-free survival (RFS) (p = 0.017; adj HR = 1.74; 1.10-2.74); relative to patients with extensive metabolism. Cox' modeling demonstrated that compared to extensive metabolizers, PM had the most significant risk of breast cancer relapse (HR 3.12, p = 0.007).

Conclusion: CYP2D6 metabolism, as measured by genetic variation and enzyme inhibition, is an independent predictor of breast cancer outcome in post-menopausal women receiving tamoxifen for early breast cancer. Determination of CYP2D6 genotype may be of value in selecting adjuvant hormonal therapy and it appears CYP2D6 inhibitors should be avoided in tamoxifen-treated women.
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http://dx.doi.org/10.1007/s10549-006-9428-0DOI Listing
January 2007

A phase I trial of twice-weekly 17-allylamino-demethoxy-geldanamycin in patients with advanced cancer.

Clin Cancer Res 2006 Oct;12(20 Pt 1):6087-93

Department of Oncology, Cancer Center Statistics, Mayo Clinic, Rochester, Minnesota 55905, USA.

Purpose: To determine the maximum tolerated dose (MTD), dose-limiting toxicity, and pharmacokinetics of 17-allylamino-demethoxy-geldanamycin (17-AAG) administered on days 1, 4, 8, and 11 every 21 days and to examine the effect of 17-AAG on the levels of chaperone and client proteins.

Experimental Design: A phase I dose escalating trial in patients with advanced solid tumors was done. Toxicity and tumor responses were evaluated by standard criteria. Pharmacokinetics were done and level of target proteins was measured at various points during cycle one.

Results: Thirteen patients were enrolled in the study. MTD was defined as 220 mg/m2. Dose-limiting toxicities were as follows: dehydration, diarrhea, hyperglycemia, and liver toxicity. At the MTD, the mean clearance of 17-AAG was 18.7 L/h/m2. There was a significant decrease in integrin-linked kinase at 6 hours after infusion on day 1 but not at 25 hours in peripheral blood mononuclear cells. Treatment with 17-AAG on day 1 significantly increased pretreatment levels of heat shock protein (HSP) 70 on day 4, which is consistent with the induction of a stress response. In vitro induction of a stress response and up-regulation of HSP70 resulted in an increased resistance to HSP90-targeted therapy in A549 cells.

Conclusions: The MTD of 17-AAG on a twice-weekly schedule was 220 mg/m2. Treatment at this dose level resulted in significant changes of target proteins and also resulted in a prolonged increase in HSP70. This raises the possibility that HSP70 induction as part of the stress response may contribute to resistance to 17-AAG.
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http://dx.doi.org/10.1158/1078-0432.CCR-06-1015DOI Listing
October 2006

Pharmacogenetics of tamoxifen biotransformation is associated with clinical outcomes of efficacy and hot flashes.

J Clin Oncol 2005 Dec;23(36):9312-8

Department of Oncology, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.

Purpose: Polymorphisms in tamoxifen metabolizing genes affect the plasma concentration of tamoxifen metabolites, but their effect on clinical outcome is unknown.

Methods: We determined cytochrome P450 (CYP)2D6 (*4 and *6) and CYP3A5 (*3) genotype from paraffin-embedded tumor samples and buccal cells (living patients) in tamoxifen-treated women enrolled onto a North Central Cancer Treatment Group adjuvant breast cancer trial. The relationship between genotype and disease outcome was determined using the log-rank test and Cox proportional hazards modeling.

Results: Paraffin blocks were obtained from 223 of 256 eligible patients, and buccal cells were obtained from 17 living women. CYP2D6 (*4 and *6) and CYP3A5 (*3) genotypes were determined from 190, 194, and 205 patient samples and in 17 living women. The concordance rate between buccal and tumor genotype was 100%. Women with the CYP2D6 *4/*4 genotype had worse relapse-free time (RF-time; P = .023) and disease-free survival (DFS; P = .012), but not overall survival (P = .169) and did not experience moderate to severe hot flashes relative to women heterozygous or homozygous for the wild-type allele. In the multivariate analysis, women with the CYP2D6 *4/*4 genotype still tended to have worse RFS (hazard ratio [HR], 1.85; P = .176) and DFS (HR, 1.86; P = .089). The CYP3A5*3 variant was not associated with any of these clinical outcomes.

Conclusion: In tamoxifen-treated patients, women with the CYP2D6 *4/*4 genotype tend to have a higher risk of disease relapse and a lower incidence of hot flashes, which is consistent with our previous observation that CYP2D6 is responsible for the metabolic activation of tamoxifen to endoxifen.
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http://dx.doi.org/10.1200/JCO.2005.03.3266DOI Listing
December 2005

A phase I and pharmacokinetic study of the selective, non-peptidic inhibitor of matrix metalloproteinase BAY 12-9566 in combination with etoposide and carboplatin.

Anticancer Drugs 2005 Oct;16(9):997-1002

Department of Oncology, Mayo Clinic, Rochester, Minnesota 55905, USA.

Matrix metalloproteinases (MMPs) are zinc-dependent endopeptidases that degrade the extracellular matrix during the processes of invasion, metastasis and angiogenesis. BAY 12-9566 (BAY) is a selective, non-peptidic biphenyl inhibitor of MMPs, with nanomolar inhibitory activity against MMP-2, -3 and -9, and anti-invasive, anti-metastatic and anti-angiogenic activity in a variety of tumor models. This phase I study of oral BAY was conducted to evaluate the safety and pharmacokinetics of BAY when administered in combination with etoposide (VP-16) or in combination with VP-16 and carboplatin (CBDCA) in subjects with advanced cancer. The first cohort of patients (n=8) received a cycle of VP-16, 60 mg/m, followed 1 week later by a fixed daily oral dose of BAY, 800 mg b.i.d., to which three potential possible doses of VP-16 (low dose: 60 mg/m; mid dose: 90 mg/m; high dose: 120 mg/m) were added every 3 weeks as tolerated. The second cohort (n=5) received VP-16 (120 mg/m) and CBDCA (AUC=5) followed 1 week later by a fixed daily oral dose of BAY (800 mg) b.i.d., to which VP-16 (120 mg/m) and CBDCA (AUC=5) were added. Dose-limiting toxicity (DLT) was defined as toxicity grade 3 or above. Maximum tolerated dose was declared if two or more patients experienced DLT. A performance status of 0-2 and acceptable organ function were required for eligibility. Plasma concentrations of BAY and VP-16 were measured to investigate pharmacokinetic interactions. Eight eligible patients with a variety of tumor types (median age 64 years, range 44-76) were enrolled in the first cohort, six of who whom completed all three levels of VP-16. Progressive disease occurred in five of the eight patients; three patients continued on study with treatment. Drug level and pharmacokinetics analysis of BAY and VP-16 were also determined. The combination of BAY and VP-16 was tolerable in the first cohort, permitting enrollment of the second cohort. In the second cohort (n=5), the combination of BAY, VP-16 and CDBCA was intolerable at the doses used due to excessive hematologic toxicity in the first five patients enrolled. Pharmacokinetics and toxicity analysis was performed for this group of patients. Only Level 1 of treatment was completed for Cohort II. At this point the study was halted due to toxicity and the results of an interim analysis that failed to demonstrate sufficient clinical activity of this compound in other clinical trials. We conclude that the combination of BAY and VP-16 was well tolerated. However, the combination of BAY, VP-16 and CDBCA produces significant hematologic toxicity. Findings from this study may help to direct further studies with other inhibitors of MMPs.
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http://dx.doi.org/10.1097/01.cad.0000176504.86551.5cDOI Listing
October 2005

Phase I trial and pharmacokinetics of gemcitabine in children with advanced solid tumors.

J Clin Oncol 2004 Jun;22(12):2445-51

Mayo Clinic, Rochester, MN, USA.

Purpose: To determine the maximum tolerated dose, toxicity, and pharmacokinetics of gemcitabine in children with refractory solid tumors.

Patients And Methods: Gemcitabine was given as a 30-minute infusion for 2 or 3 consecutive weeks every 4 weeks, to 42 patients aged 1 to 21 years. Doses of 1000, 1200 and 1500 mg/m(2) were administered for 3 weeks. Subsequently, gemcitabine was given for only 2 consecutive weeks at 1500, 1800, and 2100 mg/m(2). Plasma concentrations of gemcitabine and its metabolite, 2'2'-difluorodeoxyuridine, were measured in 28 patients.

Results: Forty patients who received 132 courses of gemcitabine were assessable for toxicity. The maximum tolerated dose of gemcitabine given weekly for 3 weeks was 1200 mg/m(2). Dose-limiting toxicity was not seen in one-third of children treated at any doses given for 2 weeks. The major toxicity was myelosuppression in three of five patients at 1500 mg/m(2) for 3 weeks, and one of seven patients at 1800 mg/m(2) for 2 weeks. Other serious adverse events were somnolence, fever and hypotension, and rash in three patients. Gemcitabine plasma concentration-time data were fit to a one- (n = 5) or two-compartment (n = 23) open model. Mean gemcitabine clearance and half-life values were 2140 mL/min/m(2) and 13.7 minutes, respectively. One patient with pancreatic cancer had a partial response. Seven patients had stable disease for 2 to 17 months.

Conclusion: Gemcitabine given by 30-minute infusion for 2 or 3 consecutive weeks every 4 weeks was tolerated well by children at doses of 2100 mg/m(2) and 1200 mg/m(2), respectively.
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http://dx.doi.org/10.1200/JCO.2004.10.142DOI Listing
June 2004