Publications by authors named "Kathy Q Cai"

70 Publications

Analysis of differential neonatal lethality in cystathionine β-synthase deficient mouse models using metabolic profiling.

FASEB J 2021 Jun;35(6):e21629

Cancer Biology Program, Fox Chase Cancer Center, Philadelphia, PA, USA.

Cystathionine beta-synthase (CBS) is a key enzyme of the trans-sulfuration pathway that converts homocysteine to cystathionine. Loss of CBS activity due to mutation results in CBS deficiency, an inborn error of metabolism characterized by extreme elevation of plasma total homocysteine (tHcy). C57BL6 mice containing either a homozygous null mutation in the cystathionine β-synthase (Cbs ) gene or an inactive human CBS protein (Tg-G307S Cbs ) are born in mendelian numbers, but the vast majority die between 18 and 21 days of age due to liver failure. However, adult Cbs null mice that express a hypomorphic allele of human CBS as a transgene (Tg-I278T Cbs ) show almost no neonatal lethality despite having serum tHcy levels similar to mice with no CBS activity. Here, we characterize liver and serum metabolites in neonatal Cbs , Tg-G307S Cbs , and Tg-I278T Cbs mice at 6, 10, and 17 days of age to understand this difference. In serum, we observe similar elevations in tHcy in both Tg-G307S Cbs and Tg-I278T Cbs compared to control animals, but methionine is much more severely elevated in Tg-G307S Cbs mice. Large scale metabolomic analysis of liver tissue confirms that both methionine and methionine-sulfoxide are significantly more elevated in Tg-G307S Cbs animals, along with significant differences in several other metabolites including hexoses, amino acids, other amines, lipids, and carboxylic acids. Our data are consistent with a model that the neonatal lethality observed in CBS-null mice is driven by excess methionine resulting in increased stress on a variety of related pathways including the urea cycle, TCA cycle, gluconeogenesis, and phosphatidylcholine biosynthesis.
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http://dx.doi.org/10.1096/fj.202100302RDOI Listing
June 2021

Ferroptotic cell death triggered by conjugated linolenic acids is mediated by ACSL1.

Nat Commun 2021 04 14;12(1):2244. Epub 2021 Apr 14.

Fox Chase Cancer Center, Philadelphia, Pennsylvania, USA.

Ferroptosis is associated with lipid hydroperoxides generated by the oxidation of polyunsaturated acyl chains. Lipid hydroperoxides are reduced by glutathione peroxidase 4 (GPX4) and GPX4 inhibitors induce ferroptosis. However, the therapeutic potential of triggering ferroptosis in cancer cells with polyunsaturated fatty acids is unknown. Here, we identify conjugated linoleates including α-eleostearic acid (αESA) as ferroptosis inducers. αESA does not alter GPX4 activity but is incorporated into cellular lipids and promotes lipid peroxidation and cell death in diverse cancer cell types. αESA-triggered death is mediated by acyl-CoA synthetase long-chain isoform 1, which promotes αESA incorporation into neutral lipids including triacylglycerols. Interfering with triacylglycerol biosynthesis suppresses ferroptosis triggered by αESA but not by GPX4 inhibition. Oral administration of tung oil, naturally rich in αESA, to mice limits tumor growth and metastasis with transcriptional changes consistent with ferroptosis. Overall, these findings illuminate a potential approach to ferroptosis, complementary to GPX4 inhibition.
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http://dx.doi.org/10.1038/s41467-021-22471-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8046803PMC
April 2021

Musashi-2 (MSI2) regulates epidermal growth factor receptor (EGFR) expression and response to EGFR inhibitors in EGFR-mutated non-small cell lung cancer (NSCLC).

Oncogenesis 2021 Mar 15;10(3):29. Epub 2021 Mar 15.

Molecular Therapeutics Program, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA, 19111, USA.

Non-small cell lung cancer (NSCLC) has limited treatment options. Expression of the RNA-binding protein (RBP) Musashi-2 (MSI2) is elevated in a subset of non-small cell lung cancer (NSCLC) tumors upon progression, and drives NSCLC metastasis. We evaluated the mechanism of MSI2 action in NSCLC to gain therapeutically useful insights. Reverse phase protein array (RPPA) analysis of MSI2-depleted versus control Kras; Trp53 NSCLC cell lines identified EGFR as a MSI2-regulated protein. MSI2 control of EGFR expression and activity in an NSCLC cell line panel was studied using RT-PCR, Western blots, and RNA immunoprecipitation. Functional consequences of MSI2 depletion were explored for cell growth and response to EGFR-targeting drugs, in vitro and in vivo. Expression relationships were validated using human tissue microarrays. MSI2 depletion significantly reduced EGFR protein expression, phosphorylation, or both. Comparison of protein and mRNA expression indicated a post-transcriptional activity of MSI2 in control of steady state levels of EGFR. RNA immunoprecipitation analysis demonstrated that MSI2 directly binds to EGFR mRNA, and sequence analysis predicted MSI2 binding sites in the murine and human EGFR mRNAs. MSI2 depletion selectively impaired cell proliferation in NSCLC cell lines with activating mutations of EGFR (EGFR). Further, depletion of MSI2 in combination with EGFR inhibitors such as erlotinib, afatinib, and osimertinib selectively reduced the growth of EGFR NSCLC cells and xenografts. EGFR and MSI2 were significantly co-expressed in EGFR human NSCLCs. These results define MSI2 as a direct regulator of EGFR protein expression, and suggest inhibition of MSI2 could be of clinical value in EGFR NSCLC.
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http://dx.doi.org/10.1038/s41389-021-00317-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7961039PMC
March 2021

Immune phenotype of patients with stage IV metastatic inflammatory breast cancer.

Breast Cancer Res 2020 12 2;22(1):134. Epub 2020 Dec 2.

Blood Cell Development and Function Program, Institute for Cancer Research, Fox Chase Cancer Center, 333 Cottman Ave, Philadelphia, PA, 19111, USA.

Background: Inflammatory breast cancer (IBC) is a rare but aggressive carcinoma characterized by severe erythema and edema of the breast, with many patients presenting in advanced metastatic disease. The "inflammatory" nature is not due to classic immune-mediated inflammation, but instead results from tumor-mediated blockage of dermal lymphatic ducts. Previous work has shown that expression of PD-L1 on tumor cells can suppress T cell activation in triple-negative (TN) non-IBC breast cancer. In the present work, we investigated immune parameters in peripheral blood of metastatic IBC patients to determine whether cellular components of the immune system are altered, thereby contributing to pathogenesis of the disease. These immune parameters were also compared to PD-1 and PD-L1 expression in IBC tumor biopsies.

Methods: Flow cytometry-based immune phenotyping was performed using fresh peripheral blood from 14 stage IV IBC patients and compared to 11 healthy age-similar control women. Immunohistochemistry for CD20, CD3, PD-1, and PD-L1 was performed on tumor biopsies of these metastatic IBC patients.

Results: IBC patients with Stage IV disease had lymphopenia with significant reductions in circulating T, B, and NK cells. Reductions were observed in all subsets of CD4 T cells, whereas reductions in CD8 T cells were more concentrated in memory subsets. Immature cytokine-producing CD56 NK cells expressed higher levels of FcγRIIIa and cytolytic granule components, suggesting accelerated maturation to cytolytic CD56 cells. Immunohistochemical analysis of tumor biopsies demonstrated moderate to high expression of PD-1 in 18.2% of patients and of PD-L1 in 36.4% of patients. Interestingly, a positive correlation was observed between co-expression levels of PD-L1 and PD-1 in tumor biopsies, and higher expression of PD-L1 in tumor biopsies correlated with higher expression of cytolytic granule components in blood CD4 T cells and CD56 NK cells, and higher numbers of CD8 effector memory T cells in peripheral blood. PD-1 expression in tumor also correlated with increased infiltration of CD20 B cells in the tumor.

Conclusions: Our results suggest that while lymphocyte populations are severely compromised in stage IV IBC patients, an immune response toward the tumor had occurred in some patients, providing biological rationale to evaluate PD-1/PD-L1 immunotherapies for IBC.
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http://dx.doi.org/10.1186/s13058-020-01371-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7709446PMC
December 2020

Netrin G1 Promotes Pancreatic Tumorigenesis through Cancer-Associated Fibroblast-Driven Nutritional Support and Immunosuppression.

Cancer Discov 2021 Feb 30;11(2):446-479. Epub 2020 Oct 30.

Cancer Biology Program, Institute for Cancer Research, Fox Chase Cancer Center, Philadelphia, Pennsylvania.

Pancreatic ductal adenocarcinoma (PDAC) has a poor 5-year survival rate and lacks effective therapeutics. Therefore, it is of paramount importance to identify new targets. Using multiplex data from patient tissue, three-dimensional coculturing assays, and orthotopic murine models, we identified Netrin G1 (NetG1) as a promoter of PDAC tumorigenesis. We found that NetG1 cancer-associated fibroblasts (CAF) support PDAC survival, through a NetG1-mediated effect on glutamate/glutamine metabolism. Also, NetG1 CAFs are intrinsically immunosuppressive and inhibit natural killer cell-mediated killing of tumor cells. These protumor functions are controlled by a signaling circuit downstream of NetG1, which is comprised of AKT/4E-BP1, p38/FRA1, vesicular glutamate transporter 1, and glutamine synthetase. Finally, blocking NetG1 with a neutralizing antibody stunts tumorigenesis, suggesting NetG1 as potential target in PDAC. SIGNIFICANCE: This study demonstrates the feasibility of targeting a fibroblastic protein, NetG1, which can limit PDAC tumorigenesis by reverting the protumorigenic properties of CAFs. Moreover, inhibition of metabolic proteins in CAFs altered their immunosuppressive capacity, linking metabolism with immunomodulatory function...
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http://dx.doi.org/10.1158/2159-8290.CD-20-0775DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7858242PMC
February 2021

TGFβR-SMAD3 Signaling Induces Resistance to PARP Inhibitors in the Bone Marrow Microenvironment.

Cell Rep 2020 10;33(1):108221

Sol Sherry Thrombosis Research Center and Fels Institute for Cancer Research and Molecular Biology, Lewis Katz School of Medicine at Temple University, Philadelphia, PA, USA. Electronic address:

Synthetic lethality triggered by PARP inhibitor (PARPi) yields promising therapeutic results. Unfortunately, tumor cells acquire PARPi resistance, which is usually associated with the restoration of homologous recombination, loss of PARP1 expression, and/or loss of DNA double-strand break (DSB) end resection regulation. Here, we identify a constitutive mechanism of resistance to PARPi. We report that the bone marrow microenvironment (BMM) facilitates DSB repair activity in leukemia cells to protect them against PARPi-mediated synthetic lethality. This effect depends on the hypoxia-induced overexpression of transforming growth factor beta receptor (TGFβR) kinase on malignant cells, which is activated by bone marrow stromal cells-derived transforming growth factor beta 1 (TGF-β1). Genetic and/or pharmacological targeting of the TGF-β1-TGFβR kinase axis results in the restoration of the sensitivity of malignant cells to PARPi in BMM and prolongs the survival of leukemia-bearing mice. Our finding may lead to the therapeutic application of the TGFβR inhibitor in patients receiving PARPis.
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http://dx.doi.org/10.1016/j.celrep.2020.108221DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7578922PMC
October 2020

Kinome Profiling of Primary Endometrial Tumors Using Multiplexed Inhibitor Beads and Mass Spectrometry Identifies SRPK1 as Candidate Therapeutic Target.

Mol Cell Proteomics 2020 12 29;19(12):2068-2090. Epub 2020 Sep 29.

Cancer Biology Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania, USA. Electronic address:

Endometrial carcinoma (EC) is the most common gynecologic malignancy in the United States, with limited effective targeted therapies. Endometrial tumors exhibit frequent alterations in protein kinases, yet only a small fraction of the kinome has been therapeutically explored. To identify kinase therapeutic avenues for EC, we profiled the kinome of endometrial tumors and normal endometrial tissues using Multiplexed Inhibitor Beads and Mass Spectrometry (MIB-MS). Our proteomics analysis identified a network of kinases overexpressed in tumors, including Serine/Arginine-Rich Splicing Factor Kinase 1 (SRPK1). Immunohistochemical (IHC) analysis of endometrial tumors confirmed MIB-MS findings and showed SRPK1 protein levels were highly expressed in endometrioid and uterine serous cancer (USC) histological subtypes. Moreover, querying large-scale genomics studies of EC tumors revealed high expression of SRPK1 correlated with poor survival. Loss-of-function studies targeting SRPK1 in an established USC cell line demonstrated SRPK1 was integral for RNA splicing, as well as cell cycle progression and survival under nutrient deficient conditions. Profiling of USC cells identified a compensatory response to SRPK1 inhibition that involved EGFR and the up-regulation of IGF1R and downstream AKT signaling. Co-targeting SRPK1 and EGFR or IGF1R synergistically enhanced growth inhibition in serous and endometrioid cell lines, representing a promising combination therapy for EC.
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http://dx.doi.org/10.1074/mcp.RA120.002012DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7710141PMC
December 2020

Wnt signaling mediates oncogenic synergy between Akt and Dlx5 in T-cell lymphomagenesis by enhancing cholesterol synthesis.

Sci Rep 2020 09 28;10(1):15837. Epub 2020 Sep 28.

Cancer Biology Program, Fox Chase Cancer Center, Philadelphia, PA, 19111, USA.

The Dlx5 homeobox gene was first implicated as an oncogene in a T-ALL mouse model expressing myristoylated (Myr) Akt2. Furthermore, overexpression of Dlx5 was sufficient to drive T-ALL in mice by directly activating Akt and Notch signaling. These findings implied that Akt2 cooperates with Dlx5 in T-cell lymphomagenesis. To test this hypothesis, Lck-Dlx5;Lck-MyrAkt2 transgenic mice were generated. MyrAkt2 synergized with Dlx5 to greatly accelerate and enhance the dissemination of T-lymphomagenesis. RNA-seq analysis performed on lymphomas from Lck-Dlx5;Lck-MyrAkt mice revealed upregulation of genes involved in the Wnt and cholesterol biosynthesis pathways. Combined RNA-seq and ChIP-seq analysis of lymphomas from Lck-Dlx5;Lck-MyrAkt mice demonstrated that β-catenin directly regulates genes involved in sterol regulatory element binding transcription factor 2 (Srebf2)-cholesterol synthesis. These lymphoma cells had high Lef1 levels and were highly sensitive to β-catenin and Srebf2-cholesterol synthesis inhibitors. Similarly, human T-ALL cell lines with activated NOTCH and AKT and elevated LEF1 levels were sensitive to inhibition of β-catenin and cholesterol pathways. Furthermore, LEF1 expression positively correlated with expression of genes involved in the cholesterol synthesis pathway in primary human T-ALL specimens. Together, these data suggest that targeting β-catenin and/or cholesterol biosynthesis, together with AKT, could have therapeutic efficacy in a subset of T-ALL patients.
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http://dx.doi.org/10.1038/s41598-020-72822-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7522078PMC
September 2020

Cholesterol Pathway Inhibition Induces TGF-β Signaling to Promote Basal Differentiation in Pancreatic Cancer.

Cancer Cell 2020 10 24;38(4):567-583.e11. Epub 2020 Sep 24.

Molecular Therapeutics Program, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111, USA; The Marvin & Concetta Greenberg Pancreatic Cancer Institute, Fox Chase Cancer Center, Philadelphia, PA, USA; Kazan Federal University, Kazan, Russian Federation. Electronic address:

Oncogenic transformation alters lipid metabolism to sustain tumor growth. We define a mechanism by which cholesterol metabolism controls the development and differentiation of pancreatic ductal adenocarcinoma (PDAC). Disruption of distal cholesterol biosynthesis by conditional inactivation of the rate-limiting enzyme Nsdhl or treatment with cholesterol-lowering statins switches glandular pancreatic carcinomas to a basal (mesenchymal) phenotype in mouse models driven by Kras expression and homozygous Trp53 loss. Consistently, PDACs in patients receiving statins show enhanced mesenchymal features. Mechanistically, statins and NSDHL loss induce SREBP1 activation, which promotes the expression of Tgfb1, enabling epithelial-mesenchymal transition. Evidence from patient samples in this study suggests that activation of transforming growth factor β signaling and epithelial-mesenchymal transition by cholesterol-lowering statins may promote the basal type of PDAC, conferring poor outcomes in patients.
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http://dx.doi.org/10.1016/j.ccell.2020.08.015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7572882PMC
October 2020

NeuroD1 Dictates Tumor Cell Differentiation in Medulloblastoma.

Cell Rep 2020 06;31(12):107782

Cancer Biology Program, Fox Chase Cancer Center, Temple University Health System, Philadelphia, PA, USA. Electronic address:

Tumor cells are characterized by unlimited proliferation and perturbed differentiation. Using single-cell RNA sequencing, we demonstrate that tumor cells in medulloblastoma (MB) retain their capacity to differentiate in a similar way as their normal originating cells, cerebellar granule neuron precursors. Once they differentiate, MB cells permanently lose their proliferative capacity and tumorigenic potential. Differentiated MB cells highly express NeuroD1, a helix-loop-helix transcription factor, and forced expression of NeuroD1 promotes the differentiation of MB cells. The expression of NeuroD1 in bulk MB cells is repressed by trimethylation of histone 3 lysine-27 (H3K27me3). Inhibition of the histone lysine methyltransferase EZH2 prevents H3K27 trimethylation, resulting in increased NeuroD1 expression and enhanced differentiation in MB cells, which consequently reduces tumor growth. These studies reveal the mechanisms underlying MB cell differentiation and provide rationales to treat MB (potentially other malignancies) by stimulating tumor cell differentiation.
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http://dx.doi.org/10.1016/j.celrep.2020.107782DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7357167PMC
June 2020

BRCA1 Mutational Complementation Induces Synthetic Viability.

Mol Cell 2020 06 30;78(5):951-959.e6. Epub 2020 Apr 30.

Molecular Therapeutics Program, Fox Chase Cancer Center, Philadelphia, PA 19111, USA. Electronic address:

BRCA1 promotes the DNA end resection and RAD51 loading steps of homologous recombination (HR). Whether these functions can be uncoupled, and whether mutant proteins retaining partial activity can complement one another, is unclear and could affect the severity of BRCA1-associated Fanconi anemia (FA). Here we generated a Brca1 mouse with a coiled-coil (CC) domain deletion. Brca1 mice are born at low frequencies, and post-natal mice have FA-like abnormalities, including bone marrow failure. Intercrossing with Brca1, which is homozygous lethal, generated Brca1 mice at Mendelian frequencies that were indistinguishable from Brca1 mice. Brca1 and Brca1 proteins were individually responsible for counteracting 53BP1-RIF1-Shieldin activity and promoting RAD51 loading, respectively. Thus, Brca1 and Brca1 alleles represent separation-of-function mutations that combine to provide a level of HR sufficient for normal development and hematopoiesis. Because BRCA1 activities can be genetically separated, compound heterozygosity for functional complementary mutations may protect individuals from FA.
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http://dx.doi.org/10.1016/j.molcel.2020.04.006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7418109PMC
June 2020

RNF168-Mediated Ubiquitin Signaling Inhibits the Viability of -Null Cancers.

Cancer Res 2020 07 25;80(13):2848-2860. Epub 2020 Mar 25.

Molecular Therapeutics Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania.

gene mutations impair homologous recombination (HR) DNA repair, resulting in cellular senescence and embryonic lethality in mice. Therefore, BRCA1-deficient cancers require adaptations that prevent excessive genomic alterations from triggering cell death. RNF168-mediated ubiquitination of γH2AX at K13/15 (ub-H2AX) serves as a recruitment module for the localization of 53BP1 to DNA break sites. Here, we found multiple -mutant cancer cell lines and primary tumors with low levels of RNF168 protein expression. Overexpression of ectopic RNF168 or a ub-H2AX fusion protein induced cell death and delayed -mutant tumor formation. Cell death resulted from the recruitment of 53BP1 to DNA break sites and inhibition of DNA end resection. Strikingly, reintroduction of BRCA1 or 53BP1 depletion restored HR and rescued the ability of cells to maintain RNF168 and ub-H2AX overexpression. Thus, downregulation of RNF168 protein expression is a mechanism for providing BRCA1-null cancer cell lines with a residual level of HR that is essential for viability. Overall, our work identifies loss of RNF168 ubiquitin signaling as a proteomic alteration that supports -mutant carcinogenesis. We propose that restoring RNF168-ub-H2AX signaling, potentially through inhibition of deubiquitinases, could represent a new therapeutic approach. SIGNIFICANCE: This study explores the concept that homologous recombination DNA repair is not an all-or-nothing concept, but a spectrum, and that where a tumor stands on this spectrum may have therapeutic relevance..
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http://dx.doi.org/10.1158/0008-5472.CAN-19-3033DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7335334PMC
July 2020

Functional proteomics interrogation of the kinome identifies MRCKA as a therapeutic target in high-grade serous ovarian carcinoma.

Sci Signal 2020 02 18;13(619). Epub 2020 Feb 18.

Cancer Biology Program, Fox Chase Cancer Center, Philadelphia, PA 19111, USA.

High-grade serous ovarian carcinoma (HGSOC) is the most lethal gynecological cancer with few effective, targeted therapies. HGSOC tumors exhibit genomic instability with frequent alterations in the protein kinome; however, only a small fraction of the kinome has been therapeutically targeted in HGSOC. Using multiplexed inhibitor beads and mass spectrometry, we mapped the kinome landscape of HGSOC tumors from patients and patient-derived xenograft models. The data revealed a prevalent signature consisting of established HGSOC driver kinases, as well as several kinases previously unexplored in HGSOC. Loss-of-function analysis of these kinases in HGSOC cells indicated MRCKA (also known as CDC42BPA) as a putative therapeutic target. Characterization of the effects of MRCKA knockdown in established HGSOC cell lines demonstrated that MRCKA was integral to signaling that regulated the cell cycle checkpoint, focal adhesion, and actin remodeling, as well as cell migration, proliferation, and survival. Moreover, inhibition of MRCKA using the small-molecule BDP9066 decreased cell proliferation and spheroid formation and induced apoptosis in HGSOC cells, suggesting that MRCKA may be a promising therapeutic target for the treatment of HGSOC.
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http://dx.doi.org/10.1126/scisignal.aax8238DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7294993PMC
February 2020

Correction to: Prognostic impact of immune gene expression signature and tumor infiltrating immune cells in localized clear cell renal cell carcinoma.

J Immunother Cancer 2019 Oct 22;7(1):273. Epub 2019 Oct 22.

Fox Chase Cancer Center, 333 Cottman Ave, Philadelphia, PA, 19111, USA.

Following publication of the original article [1], the author reported that the current funding section "Kidney Cancer Association Young Investigator Grant provided funding for this project" should be replaced with "Kidney Cancer Association Young Investigator Grant and Bucks County Board provided funding for this project."
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http://dx.doi.org/10.1186/s40425-019-0735-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6806554PMC
October 2019

RPL22L1 induction in colorectal cancer is associated with poor prognosis and 5-FU resistance.

PLoS One 2019 3;14(10):e0222392. Epub 2019 Oct 3.

Blood Cell Development and Function Program, Fox Chase Cancer Center, Philadelphia, PA, United States of America.

We have previously demonstrated that loss of the tumor suppressive activity of ribosomal protein (RP) RPL22 predisposes to development of leukemia in mouse models and aggressive disease in human patients; however, the role of RPL22 in solid tumors, specifically colorectal cancer (CRC), had not been explored. We report here that RPL22 is either deleted or mutated in 36% of CRC and provide new insights into its mechanism of action. Indeed, Rpl22 inactivation causes the induction of its highly homologous paralog, RPL22L1, which serves as a driver of cell proliferation and anchorage-independent growth in CRC cells. Moreover, RPL22L1 protein is highly expressed in patient CRC samples and correlates with poor survival. Interestingly, the association of high RPL22L1 expression with poor prognosis appears to be linked to resistance to 5-Fluorouracil, which is a core component of most CRC therapeutic regimens. Indeed, in an avatar trial, we found that human CRC samples that were unresponsive to 5-Fluorouracil in patient-derived xenografts exhibited elevated expression levels of RPL22L1. This link between RPL22L1 induction and 5-Fluorouracil resistance appears to be causal, because ectopic expression or knockdown of RPL22L1 in cell lines increases and decreases 5-Fluorouracil resistance, respectively, and this is associated with changes in expression of the DNA-repair genes, MGMT and MLH1. In summary, our data suggest that RPL22L1 might be a prognostic marker in CRC and predict 5-FU responsiveness.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0222392PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6776433PMC
March 2020

Quantification of multiphoton and fluorescence images of reproductive tissues from a mouse ovarian cancer model shows promise for early disease detection.

J Biomed Opt 2019 09;24(9):1-16

University of Arizona, College of Optical Sciences, Tucson, Arizona, United States.

Ovarian cancer is the deadliest gynecologic cancer due predominantly to late diagnosis. Early detection of ovarian cancer can increase 5-year survival rates from 40% up to 92%, yet no reliable early detection techniques exist. Multiphoton microscopy (MPM) is a relatively new imaging technique sensitive to endogenous fluorophores, which has tremendous potential for clinical diagnosis, though it is limited in its application to the ovaries. Wide-field fluorescence imaging (WFI) has been proposed as a complementary technique to MPM, as it offers high-resolution imagery of the entire organ and can be tailored to target specific biomarkers that are not captured by MPM imaging. We applied texture analysis to MPM images of a mouse model of ovarian cancer. We also conducted WFI targeting the folate receptor and matrix metalloproteinases. We find that texture analysis of MPM images of the ovary can differentiate between genotypes, which is a proxy for disease, with high statistical significance (p  <  0.001). The wide-field fluorescence signal also changes significantly between genotypes (p  <  0.01). We use the features to classify multiple tissue groups to over 80% accuracy. These results suggest that MPM and WFI are promising techniques for the early detection of ovarian cancer.
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http://dx.doi.org/10.1117/1.JBO.24.9.096010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6768507PMC
September 2019

Leukotriene Synthesis Is Critical for Medulloblastoma Progression.

Clin Cancer Res 2019 11 12;25(21):6475-6486. Epub 2019 Jul 12.

Cancer Biology Program, Fox Chase Cancer Center, Temple University Health System, Philadelphia, Pennsylvania.

Purpose: Here, we examined the role of leukotrienes, well-known inflammatory mediators, in the tumorigenesis of hedgehog pathway-associated medulloblastoma, and tested the efficacies of antagonists of leukotriene biosynthesis in medulloblastoma treatment. We examined the leukotriene levels in medulloblastoma cells by ELISA. We next tested whether leukotriene synthesis in medulloblastoma cells relied on activation of hedgehog pathway, or the presence of hedgehog ligand secreted by astrocytes. We then investigated whether leukotriene mediated hedgehog-induced Nestin expression in tumor cells. The functions of leukotriene in tumor cell proliferation and tumor growth in medulloblastoma were determined through knocking down 5-lipoxygenase (a critical enzyme for leukotriene synthesis) by shRNAs, or using 5-lipoxygenase-deficient mice. Finally, the efficacies of antagonists of leukotriene synthesis in medulloblastoma treatment were tested and .

Results: Leukotriene was significantly upregulated in medulloblastoma cells. Increased leukotriene synthesis relied on hedgehog ligand secreted by astrocytes, a major component of medulloblastoma microenvironment. Leukotriene stimulated tumor cells to express Nestin, a cytoskeletal protein essential for medulloblastoma growth. Genetic blockage of leukotriene synthesis dramatically suppressed medulloblastoma cell proliferation and tumor growth . Pharmaceutical inhibition of leukotriene synthesis markedly repressed medulloblastoma cell proliferation, but had no effect on proliferation of normal neuronal progenitors. Moreover, antagonists of leukotriene synthesis exhibited promising tumor inhibitory efficacies on drug-resistant medulloblastoma.

Conclusions: Our findings reveal a novel signaling pathway that is critical for medulloblastoma cell proliferation and tumor progression, and that leukotriene biosynthesis represents a promising therapeutic target for medulloblastoma treatment.
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http://dx.doi.org/10.1158/1078-0432.CCR-18-3549DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6825543PMC
November 2019

Inactivation of Cooperates with Losses of and to Drive the Development of Pleural Malignant Mesothelioma in Conditional Mouse Models.

Cancer Res 2019 08 31;79(16):4113-4123. Epub 2019 May 31.

Cancer Biology Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania.

Pleural malignant mesothelioma is a therapy-resistant cancer affecting the serosal lining of the thoracic cavity. Mutations/deletions of , and are the most frequent genetic lesions in human malignant mesothelioma. We introduced various combinations of these deletions in the pleura of conditional knockout (CKO) mice, focusing on the contribution of loss. While homozygous CKO of , or alone gave rise to few or no malignant mesotheliomas, inactivation of cooperated with loss of either or to drive development of malignant mesothelioma in approximately 20% of double-CKO mice, and a high incidence (22/26, 85%) of malignant mesotheliomas was observed in (triple)-CKO mice. Malignant mesothelioma onset was rapid in triple-CKO mice, with a median survival of only 12 weeks, and malignant mesotheliomas from these mice were consistently high-grade and invasive. Adenoviral-Cre treatment of normal mesothelial cells from CKO mice, but not from mice with knockout of one or any two of these genes, resulted in robust spheroid formation , suggesting that mesothelial cells from mice have stem cell-like potential. RNA-seq analysis of malignant mesotheliomas from triple-CKO mice revealed enrichment of genes transcriptionally regulated by the polycomb repressive complex 2 (PRC2) and others previously implicated in known Bap1-related cellular processes. These data demonstrate that somatic inactivation of , and results in rapid, aggressive malignant mesotheliomas, and that deletion of contributes to tumor development, in part, by loss of PRC2-mediated repression of tumorigenic target genes and by acquisition of stem cell potential, suggesting a potential avenue for therapeutic intervention. SIGNIFICANCE: Combinatorial deletions of , and result in aggressive mesotheliomas, with loss contributing to tumorigenesis by circumventing PRC2-mediated repression of oncogenic target genes.
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http://dx.doi.org/10.1158/0008-5472.CAN-18-4093DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6697648PMC
August 2019

Prognostic impact of immune gene expression signature and tumor infiltrating immune cells in localized clear cell renal cell carcinoma.

J Immunother Cancer 2019 05 28;7(1):139. Epub 2019 May 28.

Fox Chase Cancer Center, 333 Cottman Ave, Philadelphia, PA, 19111, USA.

Background: The tumor immune microenvironment has become the focus of research in clear cell renal cell carcinoma (ccRCC) due to its important role in immune surveillance post nephrectomy. This study investigates the correlation of tumor infiltrating immune cell characteristics with rates of recurrence following surgery in localized ccRCC.

Methods: We morphologically identified and scored tumor infiltrating lymphocytes (TILs) in hematoxylin and eosin (H&E) stained slides of patients with localized ccRCC (stage ≥T1b excluding stage IV). The University of Alabama at Birmingham (UAB) dataset (n = 159) was used to discover and the Fox Chase Cancer Center (FCCC) dataset (n = 198) was used to validate the results of morphologic immune cell analysis. We then performed gene expression analysis using the Immune Profile panel by NanoString in the UAB cohort and identified immune cells and pathways associated with recurrence, followed by validation in the Cancer Genome Atlas (TCGA) ccRCC dataset. Infiltrating immune cell types were identified by gene expression deconvolution.

Results: The presence of TILs identified by morphology correlated with higher T cell, Th1, CD8+ T and Treg gene signatures. Recurrence was associated with lower T cells and higher neutrophils. Higher Teffector (Teff)/Treg ratio correlated with lower rate of recurrence and was validated in the TCGA dataset. Genes associated with adaptive immune response were downregulated in tumors that recurred. Unsupervised hierarchical clustering identified a subset of patients with over-expression of adaptive response genes including CD8, CD3, GZMA/B, PRF1, IDO1, CTLA4, PDL1, ICOS and TIGIT. These patients had higher morphologic lymphocyte infiltration and T cell gene expression. Higher levels of TILs identified by morphology correlated with higher rates of recurrence in our discovery dataset but not in our validation set.

Conclusions: Recurrence of ccRCC following surgery was associated with lower T cell infiltrate, lower adaptive immune response and higher neutrophil gene expression. Presence of higher Teff/Treg ratio correlated with lower recurrence.
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http://dx.doi.org/10.1186/s40425-019-0621-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6540413PMC
May 2019

Influenza virus matrix protein M1 interacts with SLD5 to block host cell cycle.

Cell Microbiol 2019 08 16;21(8):e13038. Epub 2019 May 16.

CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.

Influenza virus matrix 1 protein (M1) is highly conserved and plays essential roles at many stages of virus life cycle. Here, we used a yeast two-hybrid system to identify the host protein SLD5, a component of the GINS complex, which is essential for the initiation of DNA replication in eukaryotic cells, as a new M1 interacting protein. M1 from several different influenza virus strains all interacted with SLD5. Overexpression of SLD5 suppressed influenza virus replication. Transient, stable, or inducible expression of M1 induced host cell cycle blockade at G0/G1 phase. Moreover, SLD5 partially rescued M1 expression- or influenza virus infection-induced G0/G1 phase accumulation in cell lines and primary mouse embryonic fibroblasts. Importantly, SLD5 transgenic mice exhibited higher resistance and improved lung epithelial regeneration after virus infection compared with wild-type mice. Therefore, influenza virus M1 blocks host cell cycle process by interacting with SLD5. Our finding reveals the multifunctional nature of M1 and provides new insight for understanding influenza virus-host interaction.
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http://dx.doi.org/10.1111/cmi.13038DOI Listing
August 2019

Overexpression and cytoplasmic localization of caspase-6 is associated with lamin A degradation in set of ovarian cancers.

Biomark Res 2018 30;6:30. Epub 2018 Oct 30.

2Sylvester Cancer Center (SCCC), Ovarian Cancer Program, University of Miami, Miami, Florida USA.

Background: In most women with ovarian cancer, the diagnosis occurs after dissemination of tumor cells beyond ovaries. Several molecular perturbations occur ahead of tumor initiation including loss of lamin A/C. Our hypothesis was that the loss of nuclear structural proteins A type lamins (lamin A/C) transcribed from LMNA gene and substrate for active caspase-6 maybe one of the molecular perturbations. Our objective is to investigate the association between the loss of lamin A/C and the overexpression of caspase-6 in ovarian cancer cells.

Method: Western blotting and immunofluorescence were used to analyze the expression of lamin A/C and active caspase-6 in normal human ovarian surface epithelial (HOSE) cells, immortalized human ovarian surface epithelial cells and a set of seven ovarian cancer cell lines (including OVCAR3, OVCAR5, and A2780). The activity of caspase-6 was measured by densitometry, fluorescence and flow cytometry. Immunohistochemistry was used to evaluate the expression of caspase-6 in set of ovarian cancer tissues previously reported to have lost lamin A/C.

Results: The results showed that HOSE cells expressed lamin A/C and no or low level of active caspase-6 while cancer cells highly expressed caspase-6 and no or low level of lamin A/C. The inhibition of caspase-6 activity in OVCAR3 cells increased lamin A but has no effect on lamin C; active caspase-6 was localized in the cytoplasm associated with the loss of lamin A.

Conclusion: Overexpression and cytoplasmic localization of caspase-6 in ovarian cancer cells may be involved in lamin A degradation and deficiency observed in some ovarian cancer cells.
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http://dx.doi.org/10.1186/s40364-018-0144-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6208109PMC
October 2018

BRCA1 Mutation-Specific Responses to 53BP1 Loss-Induced Homologous Recombination and PARP Inhibitor Resistance.

Cell Rep 2018 09;24(13):3513-3527.e7

Molecular Therapeutics Program, Fox Chase Cancer Center, Philadelphia, PA 19111, USA. Electronic address:

BRCA1 functions in homologous recombination (HR) both up- and downstream of DNA end resection. However, in cells with 53BP1 gene knockout (KO), BRCA1 is dispensable for the initiation of resection, but whether BRCA1 activity is entirely redundant after end resection is unclear. Here, we found that 53bp1 KO rescued the embryonic viability of a Brca1 mouse model that harbors a stop codon in the coiled-coil domain. However, Brca1;53bp1 mice were susceptible to tumor formation, lacked Rad51 foci, and were sensitive to PARP inhibitor (PARPi) treatment, indicative of suboptimal HR. Furthermore, BRCA1 mutant cancer cell lines were dependent on truncated BRCA1 proteins that retained the ability to interact with PALB2 for 53BP1 KO induced RAD51 foci and PARPi resistance. Our data suggest that the overall efficiency of 53BP1 loss of function induced HR may be BRCA1 mutation dependent. In the setting of 53BP1 KO, hypomorphic BRCA1 proteins are active downstream of end resection, promoting RAD51 loading and PARPi resistance.
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http://dx.doi.org/10.1016/j.celrep.2018.08.086DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6219632PMC
September 2018

Inactivation of Tp53 and Pten drives rapid development of pleural and peritoneal malignant mesotheliomas.

J Cell Physiol 2018 11 15;233(11):8952-8961. Epub 2018 Jun 15.

Cancer Biology Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania.

Malignant mesothelioma (MM) is a therapy-resistant cancer arising primarily from the lining of the pleural and peritoneal cavities. The most frequently altered genes in human MM are cyclin-dependent kinase inhibitor 2A (CDKN2A), which encodes components of the p53 (p14ARF) and RB (p16INK4A) pathways, BRCA1-associated protein 1 (BAP1), and neurofibromatosis 2 (NF2). Furthermore, the p53 gene (TP53) itself is mutated in ~15% of MMs. In many MMs, the PI3K-PTEN-AKT-mTOR signaling node is hyperactivated, which contributes to tumor cell survival and therapeutic resistance. Here, we demonstrate that the inactivation of both Tp53 and Pten in the mouse mesothelium is sufficient to rapidly drive aggressive MMs. Pten ;Tp53 mice injected intraperitoneally or intrapleurally with adenovirus-expressing Cre recombinase developed high rates of peritoneal and pleural MMs (92% of mice with a median latency of 9.4 weeks and 56% of mice with a median latency of 19.3 weeks, respectively). MM cells from these mice showed consistent activation of Akt-mTor signaling, chromosome breakage or aneuploidy, and upregulation of Myc; occasional downregulation of Bap1 was also observed. Collectively, these findings suggest that when Pten and Tp53 are lost in combination in mesothelial cells, DNA damage is not adequately repaired and genomic instability is widespread, whereas the activation of Akt due to Pten loss protects genomically damaged cells from apoptosis, thereby increasing the likelihood of tumor formation. Additionally, the mining of an online dataset (The Cancer Genome Atlas) revealed codeletions of PTEN and TP53 and/or CDKN2A/p14ARF in ~25% of human MMs, indicating that cooperative losses of these genes contribute to the development of a significant proportion of these aggressive neoplasms and suggesting key target pathways for therapeutic intervention.
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http://dx.doi.org/10.1002/jcp.26830DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6168364PMC
November 2018

Specific Targeting of -Deleted Tumors with a Combination of 2'-Fluoroadenine and 5'-Methylthioadenosine.

Cancer Res 2018 08 29;78(15):4386-4395. Epub 2018 May 29.

Cancer Biology Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania.

Homozygous deletion of the methylthioadenosine phosphorylase ( gene is a frequent event in a wide variety of human cancers and is a possible molecular target for therapy. One potential therapeutic strategy to target -deleted tumors involves combining toxic purine analogues such as 6'-thioguanine (6TG) or 2'-fluoroadenine (2FA) with the MTAP substrate 5'-deoxy-5'-methylthioadenosine (MTA). The rationale is that excess MTA will protect normal cells from purine analogue toxicity because MTAP catalyzes the conversion of MTA to adenine, which then inhibits the conversion of purine base analogues into nucleotides. However, in tumor cells, no protection takes place because adenine is not formed. Here, we examine the effects of 6TG and 2FA in combination with MTA and , MTA protected against both 6TG and 2FA toxicity in an -dependent manner, shifting the IC concentration by one to three orders of magnitude. However, in mice, MTA protected against toxicity from 2FA but failed to protect against 6TG. Addition of 100 mg/kg MTA to 20 mg/kg 2FA entirely reversed the toxicity of 2FA in a variety of tissues and the treatment was well tolerated by mice. The 2FA+MTA combination inhibited tumor growth of four different human tumor cell lines in mouse xenograft models. Our results suggest that 2FA+MTA may be a promising combination for treating -deleted tumors. Loss of MTAP occurs in about 15% of all human cancers; the MTAP protection strategy presented in this study could be very effective in treating these cancers. .
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http://dx.doi.org/10.1158/0008-5472.CAN-18-0814DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6072572PMC
August 2018

NEDD9 promotes oncogenic signaling, a stem/mesenchymal gene signature, and aggressive ovarian cancer growth in mice.

Oncogene 2018 08 18;37(35):4854-4870. Epub 2018 May 18.

Molecular Therapeutics Program, Fox Chase Cancer Center, Philadelphia, PA, USA.

Neural precursor cell expressed, developmentally downregulated 9 (NEDD9) supports oncogenic signaling in a number of solid and hematologic tumors. Little is known about the role of NEDD9 in ovarian carcinoma (OC), but available data suggest elevated mRNA and protein expression in advanced stage high-grade cancers. We used a transgenic MISIIR-TAg mouse OC model combined with genetic ablation of Nedd9 to investigate its action in the development and progression of OC. A Nedd9 genotype delayed tumor growth rate, reduced incidence of ascites, and reduced expression and activation of signaling proteins including SRC, STAT3, E-cadherin, and AURKA. Cell lines established from MISIIR-TAg;Nedd9 and MISIIR-TAg;Nedd9 mice exhibited altered migration and invasion. Growth of these cells in a syngeneic allograft model indicated that systemic Nedd9 loss in the microenvironment had little impact on tumor allograft growth, but in a Nedd9 wild-type background Nedd9 allografts exhibited significantly reduced growth, dissemination, and oncogenic signaling compared to Nedd9 allografts. Gene expression analysis revealed that Nedd9 tumors exhibited more mesenchymal "stem-like" transcriptional program, including increased expression of Aldh1a1 and Aldh1a2. Conversely, loss of Nedd9 resulted in increased expression of differentiation genes, including fallopian tube markers Foxj1, Ovgp1, and Pax8. Collectively, these data suggest that tumor cell-intrinsic Nedd9 expression promotes OC development and progression by broad induction of oncogenic protein signaling and stem/mesenchymal gene expression.
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http://dx.doi.org/10.1038/s41388-018-0296-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6119087PMC
August 2018

A Nonpyroptotic IFN-γ-Triggered Cell Death Mechanism in Nonphagocytic Cells Promotes Clearance In Vivo.

J Immunol 2018 05 13;200(10):3626-3634. Epub 2018 Apr 13.

Blood Cell Development and Function Program, Fox Chase Cancer Center, Philadelphia, PA 19111;

The cytokine IFN-γ has well-established antibacterial properties against the bacterium in phagocytes, but less is known about the effects of IFN-γ on -infected nonphagocytic cells, such as intestinal epithelial cells (IECs) and fibroblasts. In this article, we show that exposing human and murine IECs and fibroblasts to IFN-γ following infection with triggers a novel form of cell death that is neither pyroptosis nor any of the major known forms of programmed cell death. Cell death required IFN-γ-signaling via STAT1-IRF1-mediated induction of guanylate binding proteins and the presence of live in the cytosol. In vivo, ablating IFN-γ signaling selectively in murine IECs led to higher bacterial burden in colon contents and increased inflammation in the intestine of infected mice. Together, these results demonstrate that IFN-γ signaling triggers release of from the -containing vacuole into the cytosol of infected nonphagocytic cells, resulting in a form of nonpyroptotic cell death that prevents bacterial spread in the gut.
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http://dx.doi.org/10.4049/jimmunol.1701386DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6034694PMC
May 2018

Dose intensification of TRAIL-inducing ONC201 inhibits metastasis and promotes intratumoral NK cell recruitment.

J Clin Invest 2018 06 30;128(6):2325-2338. Epub 2018 Apr 30.

Laboratory of Translational Oncology and Experimental Cancer Therapeutics, Molecular Therapeutics Program and Department of Hematology/Oncology.

ONC201 is a first-in-class, orally active antitumor agent that upregulates cytotoxic TRAIL pathway signaling in cancer cells. ONC201 has demonstrated safety and preliminary efficacy in a first-in-human trial in which patients were dosed every 3 weeks. We hypothesized that dose intensification of ONC201 may impact antitumor efficacy. We discovered that ONC201 exerts dose- and schedule-dependent effects on tumor progression and cell death signaling in vivo. With dose intensification, we note a potent anti-metastasis effect and inhibition of cancer cell migration and invasion. Our preclinical results prompted a change in ONC201 dosing in all open clinical trials. We observed accumulation of activated NK+ and CD3+ cells within ONC201-treated tumors and that NK cell depletion inhibits ONC201 efficacy in vivo, including against TRAIL/ONC201-resistant Bax-/- tumors. Immunocompetent NCR1-GFP mice, in which NK cells express GFP, demonstrated GFP+ NK cell infiltration of syngeneic MC38 colorectal tumors. Activation of primary human NK cells and increased degranulation occurred in response to ONC201. Coculture experiments identified a role for TRAIL in human NK-mediated antitumor cytotoxicity. Preclinical results indicate the potential utility for ONC201 plus anti-PD-1 therapy. We observed an increase in activated TRAIL-secreting NK cells in the peripheral blood of patients after ONC201 treatment. The results offer what we believe to be a unique pathway of immune stimulation for cancer therapy.
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http://dx.doi.org/10.1172/JCI96711DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5983321PMC
June 2018

Metabolite Profiling Reveals the Glutathione Biosynthetic Pathway as a Therapeutic Target in Triple-Negative Breast Cancer.

Mol Cancer Ther 2018 01 11;17(1):264-275. Epub 2017 Oct 11.

Fox Chase Cancer Center, Philadelphia, Pennsylvania.

Cancer cells can exhibit altered dependency on specific metabolic pathways and targeting these dependencies is a promising therapeutic strategy. Triple-negative breast cancer (TNBC) is an aggressive and genomically heterogeneous subset of breast cancer that is resistant to existing targeted therapies. To identify metabolic pathway dependencies in TNBC, we first conducted mass spectrometry-based metabolomics of TNBC and control cells. Relative levels of intracellular metabolites distinguished TNBC from nontransformed breast epithelia and revealed two metabolic subtypes within TNBC that correlate with markers of basal-like versus non-basal-like status. Among the distinguishing metabolites, levels of the cellular redox buffer glutathione were lower in TNBC cell lines compared to controls and markedly lower in non-basal-like TNBC. Significantly, these cell lines showed enhanced sensitivity to pharmacologic inhibition of glutathione biosynthesis that was rescued by N-acetylcysteine, demonstrating a dependence on glutathione production to suppress ROS and support tumor cell survival. Consistent with this, patients whose tumors express elevated levels of γ-glutamylcysteine ligase, the rate-limiting enzyme in glutathione biosynthesis, had significantly poorer survival. We find, further, that agents that limit the availability of glutathione precursors enhance both glutathione depletion and TNBC cell killing by γ-glutamylcysteine ligase inhibitors Importantly, we demonstrate the ability to this approach to suppress glutathione levels and TNBC xenograft growth Overall, these findings support the potential of targeting the glutathione biosynthetic pathway as a therapeutic strategy in TNBC and identify the non-basal-like subset as most likely to respond. .
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http://dx.doi.org/10.1158/1535-7163.MCT-17-0407DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5892195PMC
January 2018

Succinate dehydrogenase deficiency in a PDGFRA mutated GIST.

BMC Cancer 2017 Aug 2;17(1):512. Epub 2017 Aug 2.

Molecular Therapeutics Program, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA, 19111-2497, USA.

Background: Most gastrointestinal stromal tumors (GISTs) harbor mutually exclusive gain of function mutations in the receptor tyrosine kinase (RTK) KIT (70-80%) or in the related receptor PDGFRA (~10%). These GISTs generally respond well to therapy with the RTK inhibitor imatinib mesylate (IM), although initial response is genotype-dependent. An alternate mechanism leading to GIST oncogenesis is deficiency in the succinate dehydrogenase (SDH) enzyme complex resulting from genetic or epigenetic inactivation of one of the four SDH subunit genes (SDHA, SDHB, SDHC, SDHD, collectively referred to as SDHX). SDH loss of function is generally seen only in GIST lacking RTK mutations, and SDH-deficient GIST respond poorly to imatinib therapy.

Methods: Tumor and normal DNA from a GIST case carrying the IM-resistant PDGFRA D842V mutation was analyzed by whole exome sequencing (WES) to identify additional potential targets for therapy. The tumors analyzed were separate recurrences following progression on imatinib, sunitinib, and the experimental PDGFRA inhibitor crenolanib. Tumor sections from the GIST case and a panel of ~75 additional GISTs were subjected to immunohistochemistry (IHC) for the SDHB subunit.

Results: Surprisingly, a somatic, loss of function mutation in exon 4 of the SDHB subunit gene (c.291_292delCT, p.I97Mfs*21) was identified in both tumors. Sanger sequencing confirmed the presence of this inactivating mutation, and IHC for the SDHB subunit demonstrated that these tumors were SDH-deficient. IHC for the SDHB subunit across a panel of ~75 GIST cases failed to detect SDH deficiency in other GISTs with RTK mutations.

Conclusions: This is the first reported case of a PDGFRA mutant GIST exhibiting SDH-deficiency. A brief discussion of the relevant GIST literature is included.
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http://dx.doi.org/10.1186/s12885-017-3499-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5541693PMC
August 2017