Publications by authors named "Kay Huebner"

102 Publications

Abrogation of esophageal carcinoma development in miR-31 knockout rats.

Proc Natl Acad Sci U S A 2020 03 2;117(11):6075-6085. Epub 2020 Mar 2.

Department of Cancer Biology and Genetics, Comprehensive Cancer Center, The Ohio State University, Columbus, OH 43210;

MicroRNA-31 (miR-31) is overexpressed in esophageal squamous cell carcinoma (ESCC), a deadly disease associated with dietary Zn deficiency and inflammation. In a Zn deficiency-promoted rat ESCC model with miR-31 up-regulation, cancer-associated inflammation, and a high ESCC burden following -nitrosomethylbenzylamine (NMBA) exposure, systemic antimiR-31 delivery reduced ESCC incidence from 85 to 45% ( = 0.038) and miR-31 gene knockout abrogated development of ESCC ( = 1 × 10). Transcriptomics, genome sequencing, and metabolomics analyses in these Zn-deficient rats revealed the molecular basis of ESCC abrogation by miR-31 knockout. Our identification of EGLN3, a known negative regulator of nuclear factor κB (NF-κB), as a direct target of miR-31 establishes a functional link between oncomiR-31, tumor suppressor target EGLN3, and up-regulated NF-κB-controlled inflammation signaling. Interaction among oncogenic miR-31, EGLN3 down-regulation, and inflammation was also documented in human ESCCs. miR-31 deletion resulted in suppression of miR-31-associated EGLN3/NF-κB-controlled inflammatory pathways. ESCC-free, Zn-deficient miR-31 rat esophagus displayed no genome instability and limited metabolic activity changes vs. the pronounced mutational burden and ESCC-associated metabolic changes of Zn-deficient wild-type rats. These results provide conclusive evidence that miR-31 expression is necessary for ESCC development.
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http://dx.doi.org/10.1073/pnas.1920333117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7084137PMC
March 2020

Fhit-Fdxr interaction in the mitochondria: modulation of reactive oxygen species generation and apoptosis in cancer cells.

Cell Death Dis 2019 02 15;10(3):147. Epub 2019 Feb 15.

Department of Cancer Biology and Genetics, The Ohio State University Comprehensive Cancer Center, Columbus, OH, 43210, USA.

Fhit protein is lost in cancers of most, perhaps all, cancer types; when restored, it can induce apoptosis and suppress tumorigenicity, as shown in vitro and in mouse tumor models in vivo. Following protein cross-linking and proteomics analyses, we characterized a Fhit protein complex involved in triggering Fhit-mediated apoptosis. The complex includes the heat-shock chaperonin pair, HSP60/10, which is likely involved in importing Fhit into the mitochondria, where it interacts with ferredoxin reductase, responsible for transferring electrons from NADPH to cytochrome P450 via ferredoxin, in electron transport chain complex III. Overexpression of Fhit protein in Fhit-deficient cancer cells modulates the production of intracellular reactive oxygen species, causing increased ROS, following peroxide treatment, with subsequent increased apoptosis of lung cancer cells under oxidative stress conditions; conversely, Fhit-negative cells escape ROS overproduction and ROS-induced apoptosis, likely carrying oxidative damage. Thus, characterization of Fhit-interacting proteins has identified direct effectors of a Fhit-mediated apoptotic signal pathway that is lost in many cancers. This is of translational interest considering the very recent emphasis in a number of high-profile publications, concerning the role of oxidative phosphorylation in the treatment of human cancers, and especially cancer stem cells that rely upon oxidative phosphorylation for survival. Additionally, we have shown that cells from a Fhit-deficient lung cancer cell line, are sensitive to killing by exposure to atovaquone, thought to act as a selective oxidative phosphorylation inhibitor by targeting the CoQ10 dependence of the mitochondrial complex III, while the Fhit-expressing sister clone is resistant to this treatment.
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http://dx.doi.org/10.1038/s41419-019-1414-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6377664PMC
February 2019

PREFACE.

Authors:
Kay Huebner

Genes Chromosomes Cancer 2019 05 28;58(5):257-259. Epub 2019 Jan 28.

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http://dx.doi.org/10.1002/gcc.22722DOI Listing
May 2019

Human-like hyperplastic prostate with low ZIP1 induced solely by Zn deficiency in rats.

Proc Natl Acad Sci U S A 2018 11 5;115(47):E11091-E11100. Epub 2018 Nov 5.

Department of Cancer Biology and Genetics, The Ohio State University, Columbus, OH 43210;

Prostate cancer is a leading cause of cancer death in men over 50 years of age, and there is a characteristic marked decrease in Zn content in the malignant prostate cells. The cause and consequences of this loss have thus far been unknown. We found that in middle-aged rats a Zn-deficient diet reduces prostatic Zn levels ( = 0.025), increases cellular proliferation, and induces an inflammatory phenotype with COX-2 overexpression. This hyperplastic/inflammatory prostate has a human prostate cancer-like microRNA profile, with up-regulation of the Zn-homeostasis-regulating miR-183-96-182 cluster (fold change = 1.41-2.38; = 0.029-0.0003) and down-regulation of the Zn importer ZIP1 (target of miR-182), leading to a reduction of prostatic Zn. This inverse relationship between miR-182 and ZIP1 also occurs in human prostate cancer tissue, which is known for Zn loss. The discovery that the Zn-depleted middle-aged rat prostate has a metabolic phenotype resembling that of human prostate cancer, with a 10-fold down-regulation of citric acid ( = 0.0003), links citrate reduction directly to prostatic Zn loss, providing the underlying mechanism linking dietary Zn deficiency with miR-183-96-182 overexpression, ZIP1 down-regulation, prostatic Zn loss, and the resultant citrate down-regulation, changes mimicking features of human prostate cancer. Thus, dietary Zn deficiency during rat middle age produces changes that mimic those of human prostate carcinoma and may increase the risk for prostate cancer, supporting the need for assessment of Zn supplementation in its prevention.
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http://dx.doi.org/10.1073/pnas.1813956115DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6255182PMC
November 2018

FHIT, a Novel Modifier Gene in Pulmonary Arterial Hypertension.

Am J Respir Crit Care Med 2019 01;199(1):83-98

1 Division of Pulmonary and Critical Care, Department of Medicine.

Rationale: Pulmonary arterial hypertension (PAH) is characterized by progressive narrowing of pulmonary arteries, resulting in right heart failure and death. BMPR2 (bone morphogenetic protein receptor type 2) mutations account for most familial PAH forms whereas reduced BMPR2 is present in many idiopathic PAH forms, suggesting dysfunctional BMPR2 signaling to be a key feature of PAH. Modulating BMPR2 signaling is therapeutically promising, yet how BMPR2 is downregulated in PAH is unclear.

Objectives: We intended to identify and pharmaceutically target BMPR2 modifier genes to improve PAH.

Methods: We combined siRNA high-throughput screening of >20,000 genes with a multicohort analysis of publicly available PAH RNA expression data to identify clinically relevant BMPR2 modifiers. After confirming gene dysregulation in tissue from patients with PAH, we determined the functional roles of BMPR2 modifiers in vitro and tested the repurposed drug enzastaurin for its propensity to improve experimental pulmonary hypertension (PH).

Measurements And Main Results: We discovered FHIT (fragile histidine triad) as a novel BMPR2 modifier. BMPR2 and FHIT expression were reduced in patients with PAH. FHIT reductions were associated with endothelial and smooth muscle cell dysfunction, rescued by enzastaurin through a dual mechanism: upregulation of FHIT as well as miR17-5 repression. Fhit mice had exaggerated hypoxic PH and failed to recover in normoxia. Enzastaurin reversed PH in the Sugen5416/hypoxia/normoxia rat model, by improving right ventricular systolic pressure, right ventricular hypertrophy, cardiac fibrosis, and vascular remodeling.

Conclusions: This study highlights the importance of the novel BMPR2 modifier FHIT in PH and the clinical value of the repurposed drug enzastaurin as a potential novel therapeutic strategy to improve PAH.
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http://dx.doi.org/10.1164/rccm.201712-2553OCDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6353016PMC
January 2019

Loss of fragile histidine triad (Fhit) protein expression alters the translation of cancer-associated mRNAs.

BMC Res Notes 2018 Mar 14;11(1):178. Epub 2018 Mar 14.

Center for RNA Biology, The Ohio State University, 484 West 12th Ave., Columbus, OH, 43210, USA.

Objectives: In > 50% of cancers tumor development involves the early loss of Fhit (fragile histidine triad) protein expression, yet the mechanistic pathway(s) by which Fhit mediates its tumor suppressor functions are not fully understood. Earlier attempts to identify a Fhit-deficient gene expression profile relied on total cellular RNA and microarray analysis. The data here used RNA sequencing (RNA-Seq) of Fhit-negative and Fhit-positive cells as proof of principle for the impact of Fhit on specific mRNAs, and to lay the foundation for a study using ribosome profiling to identify mRNAs whose translation is affected by FHIT loss.

Data Description: RNA-Seq was performed on RNA from lines of Fhit-expressing and Fhit-deficient lung cancer cells. This identified changes in the levels of mRNAs for a number of cell survival and cell cycle progression genes. Polysome profile analysis performed on cytoplasmic extracts from Fhit-negative and Fhit-positive cells showed changes in the sedimentation of select mRNAs consistent with changes in translation efficiency. The impact of differential Fhit expression on the turnover of selected cancer-linked mRNAs was determined by RT-qPCR of cytoplasmic RNA isolated at intervals after treating cells with a transcription inhibitor.
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http://dx.doi.org/10.1186/s13104-018-3278-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5853088PMC
March 2018

Impact of FHIT loss on the translation of cancer-associated mRNAs.

Mol Cancer 2017 12 28;16(1):179. Epub 2017 Dec 28.

Center for RNA Biology, The Ohio State University, Columbus, OH, 43210, USA.

Background: FHIT is a genome caretaker/tumor suppressor that is silenced in >50% of cancers. Although it was identified more than 20 years ago, questions remain as to how FHIT loss contributes to cancer, and conversely, how FHIT acts to maintain genome integrity and suppress malignancy. Fhit belongs to the histidine triad family of enzymes that catalyze the degradation of nucleoside 5',5'-triphosphates, including the mGpppN 'caps' that are generated when mRNAs undergo 3'-5' decay. This raised the possibility that Fhit loss might affect changes in the translation of cancer-associated mRNAs, possibly as a consequence of increased intracellular concentrations of these molecules.

Results: Ribosome profiling identified several hundred mRNAs for which coding region ribosome occupancy changed as a function of Fhit expression. While many of these changes could be explained by changes in mRNA steady-state, a subset of these showed changes in translation efficiency as a function of Fhit expression. The onset of malignancy has been linked to changes in 5'-UTR ribosome occupancy and this analysis also identified ribosome binding to 5'-untranslated regions (UTRs) of a number of cancer-associated mRNAs. 5'-UTR ribosome occupancy of these mRNAs differed between Fhit-negative and Fhit-positive cells, and in some cases these differences correlated with differences in coding region ribosome occupancy.

Conclusions: In summary, these findings show Fhit expression impacts the translation of a number of cancer associated genes, and they support the hypothesis that Fhit's genome protective/tumor suppressor function is associated with post-transcriptional changes in expression of genes whose dysregulation contributes to malignancy.
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http://dx.doi.org/10.1186/s12943-017-0749-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5745650PMC
December 2017

The ubiquitous 'cancer mutational signature' 5 occurs specifically in cancers with deleted alleles.

Oncotarget 2017 Nov 6;8(60):102199-102211. Epub 2017 Nov 6.

Department of Cancer Biology & Genetics, The Ohio State University Comprehensive Cancer Center & Wexner Medical Center, Biomedical Research Tower, Columbus, OH 43210, USA.

The gene is located at the fragile FRA3B locus where activation by carcinogen-induced and endogenous replication stress causes deletions even in normal cells over a lifetime. Our lab has shown that loss of expression causes genome instability and provides single-strand DNA substrates for APOBEC3B hypermutation, in line with evidence that locus deletions occur in many cancers. Based on these biological features, we hypothesized that loss drives development of COSMIC mutational signature 5 and here provide evidence, including data mining of >6,500 TCGA samples, that is the cancer-associated gene with copy number alterations correlating most significantly with signature 5 mutation rate. In addition, tissues of Fhit-deficient mice exhibit a mutational signature strongly resembling signature 5 (cosine similarity value = 0.89). We conclude that loss is a molecular determinant for signature 5 mutations, which occur in all cancer types early in cancer development, are clock-like, and accelerated by carcinogen exposure. Loss of caretaker function may be a predictive and preventive marker for cancer development.
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http://dx.doi.org/10.18632/oncotarget.22321DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5731946PMC
November 2017

Nit1 is a metabolite repair enzyme that hydrolyzes deaminated glutathione.

Proc Natl Acad Sci U S A 2017 04 3;114(16):E3233-E3242. Epub 2017 Apr 3.

Walloon Excellence in Lifesciences and Biotechnology, B-1200 Brussels, Belgium;

The mammalian gene (nitrilase-like protein 1) encodes a protein that is highly conserved in eukaryotes and is thought to act as a tumor suppressor. Despite being ∼35% sequence identical to ω-amidase (Nit2), the Nit1 protein does not hydrolyze efficiently α-ketoglutaramate (a known physiological substrate of Nit2), and its actual enzymatic function has so far remained a puzzle. In the present study, we demonstrate that both the mammalian Nit1 and its yeast ortholog are amidases highly active toward deaminated glutathione (dGSH; i.e., a form of glutathione in which the free amino group has been replaced by a carbonyl group). We further show that -KO mutants of both human and yeast cells accumulate dGSH and the same compound is excreted in large amounts in the urine of -KO mice. Finally, we show that several mammalian aminotransferases (transaminases), both cytosolic and mitochondrial, can form dGSH via a common (if slow) side-reaction and provide indirect evidence that transaminases are mainly responsible for dGSH formation in cultured mammalian cells. Altogether, these findings delineate a typical instance of metabolite repair, whereby the promiscuous activity of some abundant enzymes of primary metabolism leads to the formation of a useless and potentially harmful compound, which needs a suitable "repair enzyme" to be destroyed or reconverted into a useful metabolite. The need for a dGSH repair reaction does not appear to be limited to eukaryotes: We demonstrate that Nit1 homologs acting as excellent dGSH amidases also occur in and other glutathione-producing bacteria.
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http://dx.doi.org/10.1073/pnas.1613736114DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5402446PMC
April 2017

Fhit down-regulation is an early event in pancreatic carcinogenesis.

Virchows Arch 2017 Jun 13;470(6):647-653. Epub 2017 Mar 13.

Comprehensive Cancer Center, Department of Cancer Biology and Genetics, The Ohio State University, Columbus, OH, USA.

Aberrant Fhit expression characterizes a large proportion of primary pancreatic ductal adenocarcinomas (PDACs), but fragmentary information is available on Fhit expression during the phenotypic changes of pancreatic ductal epithelium during multistep transformation. We assessed Fhit expression by immunohistochemistry in two different multistep pancreatic carcinogenic processes: pancreatic intraepithelial neoplasia (PanIN) and intraductal papillary mucinous neoplasia (IPMN). We considered 105 surgically treated PDACs/IPMNs and selected 30 samples of non-neoplastic pancreatic parenchyma, 50 PanIN lesions, 30 IPMNs, 15 IPMNs with associated invasive carcinoma, and 60 adenocarcinomas. Normal pancreatic ducts and surrounding acinar cells consistently showed moderate to strong Fhit immunoreactivity. Significant down-regulation of Fhit expression was observed in association with increasing severity of dysplastia/neoplastia in both carcinogenic processes. This was further confirmed by studying multiple lesions obtained from the same surgical specimen. Of 60 PDACs, only 14 showed Fhit expression comparable to normal pancreatic ductal epithelium, while the remainder (77%) showed clearly negative or reduced Fhit expression. This study demonstrates that Fhit down-regulation is an early event in both multistep carcinogenic processes leading to PDAC.
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http://dx.doi.org/10.1007/s00428-017-2105-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5568551PMC
June 2017

Fragile Genes That Are Frequently Altered in Cancer: Players Not Passengers.

Cytogenet Genome Res 2016 16;150(3-4):208-216. Epub 2017 Feb 16.

Department of Cancer Biology and Genetics, Comprehensive Cancer Center, Ohio State University Wexner Medical Center, Columbus, OH, USA.

FHIT, located at FRA3B, is one of the most commonly deleted genes in human cancers, and loss of FHIT protein is one of the earliest events in cancer initiation. However, location of FHIT at a chromosomal fragile site, a locus prone to breakage and gap formation under even mild replication stress, has encouraged claims that FHIT loss is a passenger event in cancers. We summarize accumulated evidence that FHIT protein functions as a genome "caretaker" required to protect the stability of genomes of normal cells of most tissues from agents causing intrinsic and extrinsic DNA damage. FHIT loss leads to intracellular replication stress and subsequent genome instability, which provides an opportunistic mutational landscape in preneoplasias for selection of a variety of other cancer-driving mutations. We also review evidence showing that FHIT loss leads to enhanced activation of other common fragile sites, including the FRA16D/WWOX locus, and creates optimal single-stranded DNA substrates for the hypermutator enzyme, APOBEC3B.
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http://dx.doi.org/10.1159/000455753DOI Listing
April 2017

Identification of Fhit as a post-transcriptional effector of Thymidine Kinase 1 expression.

Biochim Biophys Acta Gene Regul Mech 2017 Mar 14;1860(3):374-382. Epub 2017 Jan 14.

Department of Cancer Biology and Genetics, The Ohio State University, 460 West 12 Ave., Columbus, OH 43210 USA.

FHIT is a genome caretaker gene that is silenced in >50% of cancers. Loss of Fhit protein expression promotes accumulation of DNA damage, affects apoptosis and epithelial-mesenchymal transition, though molecular mechanisms underlying these alterations have not been fully elucidated. Initiation of genome instability directly follows Fhit loss and the associated reduced Thymidine Kinase 1 (TK1) protein expression. The effects on TK1 of Fhit knockdown and Fhit induction in the current study confirmed the role of Fhit in regulating TK1 expression. Changes in Fhit expression did not impact TK1 protein turnover or transcription from the TK1 promoter, nor steady-state levels of TK1 mRNA or turnover. Polysome profile analysis showed that up-regulated Fhit expression resulted in decreased TK1 RNA in non-translating messenger ribonucleoproteins and increased ribosome density on TK1 mRNA. Fhit does not bind RNA but its expression increased luciferase expression from a transgene bearing the TK1 5'-UTR. Fhit has been reported to act as a scavenger decapping enzyme, and a similar result with a mutant (H96) that binds but does not cleave nucleoside 5',5'-triphosphates suggests the impact on TK1 translation is due to its ability to modulate the intracellular level of cap-like molecules. Consistent with this, cells expressing Fhit mutants with reduced activity toward cap-like dinucleotides exhibit DNA damage resulting from TK1 deficiency, whereas cells expressing wild-type Fhit or the H96N mutant do not. The results have implications for the mechanism by which Fhit regulates TK1 mRNA, and more broadly, for its modulation of multiple functions as tumor suppressor/genome caretaker.
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http://dx.doi.org/10.1016/j.bbagrm.2017.01.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5325794PMC
March 2017

Fhit and Wwox loss-associated genome instability: A genome caretaker one-two punch.

Adv Biol Regul 2017 Jan 26;63:167-176. Epub 2016 Sep 26.

Department of Cancer Biology and Genetics, The Ohio State University Wexner Medical Center, Columbus, OH, USA. Electronic address:

Expression of Fhit and Wwox protein is frequently lost or reduced in many human cancers. In this report, we provide data that further characterizes the molecular consequences of Fhit loss in the initiation of DNA double-strand breaks (DSBs), and of Wwox loss in altered repair of DSBs. We show that loss of Fhit initiates mild genome instability in early passage mouse kidney cells, confirming that DNA damage associated with Fhit-deficiency is not limited to cancer cells. We also demonstrate that the cause of Fhit-deficient DSBs: thymidine deficiency-induced replication stress, can be resolved with thymidine supplementation in early passage mouse kidney cells before extensive genome instability occurs. As for consequences of Wwox loss in cancer, we show in a small panel of breast cancer cells and mouse embryonic fibroblasts that Wwox expression predicts response to radiation and mitomycin C, all agents that cause DSBs. In addition, loss of Wwox significantly reduced progression free survival in a cohort of ovarian cancer patients treated with platin-based chemotherapies. Finally, stratification of a cohort of squamous lung cancers by Fhit expression reveals that Wwox expression is significantly reduced in the low Fhit-expressing group, suggesting that loss of Fhit is quickly succeeded by loss of Wwox. We propose that Fhit and Wwox loss work synergistically in cancer progression and that DNA damage caused by Fhit could be targeted early in cancer initiation for prevention, while DNA damage caused by Wwox loss could be targeted later in cancer progression, particularly in cancers that develop resistance to genotoxic therapies.
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http://dx.doi.org/10.1016/j.jbior.2016.09.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7213024PMC
January 2017

Fhit loss-associated initiation and progression of neoplasia in vitro.

Cancer Sci 2016 Nov 3;107(11):1590-1598. Epub 2016 Oct 3.

Department of Cancer Biology and Genetics, Ohio State University Wexner Medical Center, Columbus, Ohio, USA.

The FHIT gene, encompassing an active common fragile site, FRA3B, is frequently silenced in preneoplasia and cancer, through gene rearrangement or methylation of regulatory sequences. Silencing of Fhit protein expression causes thymidine kinase 1 downregulation, resulting in dNTP imbalance, and spontaneous replication stress that leads to chromosomal aberrations, allele copy number variations, insertions/deletions, and single-base substitutions. Thus, Fhit, which is reduced in expression in the majority of human cancers, is a genome "caretaker" whose loss initiates genome instability in preneoplastic lesions. To follow the early genetic alterations and functional changes induced by Fhit loss that may recapitulate the neoplastic process in vitro, we established epithelial cell lines from kidney tissues of Fhit-/- and +/+ mouse pups early after weaning, and subjected cell cultures to nutritional and carcinogen stress, which +/+ cells did not survive. Through transcriptome profiling and protein expression analysis, we observed changes in the Trp53/p21 and survivin apoptotic pathways in -/- cells, and in expression of proteins involved in epithelial-mesenchymal transition. Some Fhit-deficient cell lines showed anchorage-independent colony formation and increased invasive capacity in vitro. Furthermore, cells of stressed Fhit-/- cell lines formed s.c. and metastatic tumors in nude mice. Collectively, we show that Fhit loss and subsequent thymidine kinase 1 inactivation, combined with selective pressures, leads to neoplasia-associated alterations in genes and gene expression patterns in vitro and in vivo.
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http://dx.doi.org/10.1111/cas.13032DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5132276PMC
November 2016

Reduction in squamous cell carcinomas in mouse skin by dietary zinc supplementation.

Cancer Med 2016 08 17;5(8):2032-42. Epub 2016 May 17.

Department of Molecular Virology, Immunology and Medical Genetics, The Ohio State University Comprehensive Cancer Center, Columbus, Ohio.

Inadequate dietary Zn consumption increases susceptibility to esophageal and other cancers in humans and model organisms. Since Zn supplementation can prevent cancers in rodent squamous cell carcinoma (SCC) models, we were interested in determining if it could have a preventive effect in a rodent skin cancer model, as a preclinical basis for considering a role for Zn in prevention of human nonmelanoma skin cancers, the most frequent cancers in humans. We used the 7,12-dimethyl benzanthracene carcinogen/phorbol myristate acetate tumor promoter treatment method to induce skin tumors in Zn-sufficient wild-type and Fhit (human or mouse protein) knockout mice. Fhit protein expression is lost in >50% of human cancers, including skin SCCs, and Fhit-deficient mice show increased sensitivity to carcinogen induction of tumors. We hypothesized that: (1) the skin cancer burdens would be reduced by Zn supplementation; (2) Fhit(-/-) (Fhit, murine fragile histidine triad gene) mice would show increased susceptibility to skin tumor induction versus wild-type mice. 30 weeks after initiating treatment, the tumor burden was increased ~2-fold in Fhit(-/-) versus wild-type mice (16.2 versus 7.6 tumors, P < 0.001); Zn supplementation significantly reduced tumor burdens in Fhit(-/-) mice (males and females combined, 16.2 unsupplemented versus 10.3 supplemented, P = 0.001). Most importantly, the SCC burden was reduced after Zn supplementation in both strains and genders of mice, most significantly in the wild-type males (P = 0.035). Although the mechanism(s) of action of Zn supplementation in skin tumor prevention is not known in detail, the Zn-supplemented tumors showed evidence of reduced DNA damage and some cohorts showed reduced inflammation scores. The results suggest that mild Zn supplementation should be tested for prevention of skin cancer in high-risk human cohorts.
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http://dx.doi.org/10.1002/cam4.768DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4873604PMC
August 2016

Exome-wide single-base substitutions in tissues and derived cell lines of the constitutive Fhit knockout mouse.

Cancer Sci 2016 Apr 23;107(4):528-35. Epub 2016 Feb 23.

Department of Molecular Virology, Immunology and Medical Genetics, Columbus, Ohio, USA.

Loss of expression of Fhit, a tumor suppressor and genome caretaker, occurs in preneoplastic lesions during development of many human cancers. Furthermore, Fhit-deficient mouse models are exquisitely susceptible to carcinogen induction of cancers of the lung and forestomach. Due to absence of Fhit genome caretaker function, cultured cells and tissues of the constitutive Fhit knockout strain develop chromosome aneuploidy and allele copy number gains and losses and we hypothesized that Fhit-deficient cells would also develop point mutations. On analysis of whole exome sequences of Fhit-deficient tissues and cultured cells, we found 300 to >1000 single-base substitutions associated with Fhit loss in the 2% of the genome included in exomes, relative to the C57Bl6 reference genome. The mutation signature is characterized by increased C>T and T>C mutations, similar to the "age at diagnosis" signature identified in human cancers. The Fhit-deficiency mutation signature also resembles a C>T and T>C mutation signature reported for human papillary kidney cancers and a similar signature recently reported for esophageal and bladder cancers, cancers that are frequently Fhit deficient. The increase in T>C mutations in -/- exomes may be due to dNTP imbalance, particularly in thymidine triphosphate, resulting from decreased expression of thymidine kinase 1 in Fhit-deficient cells. Fhit-deficient kidney cells that survived in vitro dimethylbenz(a)anthracene treatment additionally showed increased T>A mutations, a signature generated by treatment with this carcinogen, suggesting that these T>A transversions may be evidence of carcinogen-induced preneoplastic changes.
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http://dx.doi.org/10.1111/cas.12887DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4832848PMC
April 2016

TWIST1-Induced miR-424 Reversibly Drives Mesenchymal Programming while Inhibiting Tumor Initiation.

Cancer Res 2015 May 25;75(9):1908-21. Epub 2015 Feb 25.

Program in Molecular Biology, University of Colorado Anschutz Medical Campus, Aurora, Colorado. Department of Pharmacology, University of Colorado Anschutz Medical Campus, Aurora, Colorado. Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, Colorado.

Epithelial-to-mesenchymal transition (EMT) is a dynamic process that relies on cellular plasticity. Recently, the process of an oncogenic EMT, followed by a reverse mesenchymal-to-epithelial transition (MET), has been implicated as critical in the metastatic colonization of carcinomas. Unlike governance of epithelial programming, regulation of mesenchymal programming is not well understood in EMT. Here, we describe and characterize the first microRNA that enhances exclusively mesenchymal programming. We demonstrate that miR-424 is upregulated early during a TWIST1 or SNAI1-induced EMT, and that it causes cells to express mesenchymal genes without affecting epithelial genes, resulting in a mixed/intermediate EMT. Furthermore, miR-424 increases motility, decreases adhesion, and induces a growth arrest, changes associated with a complete EMT that can be reversed when miR-424 expression is lowered, concomitant with an MET-like process. Breast cancer patient miR-424 levels positively associate with TWIST1/2 and EMT-like gene signatures, and miR-424 is increased in primary tumors versus matched normal breast. However, miR-424 is downregulated in patient metastases versus matched primary tumors. Correspondingly, miR-424 decreases tumor initiation and is posttranscriptionally downregulated in macrometastases in mice, suggesting the need for biphasic expression of miR-424 to transit the EMT-MET axis. Next-generation RNA sequencing revealed miR-424 regulates numerous EMT and cancer stemness-associated genes, including TGFBR3, whose downregulation promotes mesenchymal phenotypes, but not tumor-initiating phenotypes. Instead, we demonstrate that increased MAPK-ERK signaling is critical for miR-424-mediated decreases in tumor-initiating phenotypes. These findings suggest miR-424 plays distinct roles in tumor progression, potentially facilitating earlier, but repressing later, stages of metastasis by regulating an EMT-MET axis.
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http://dx.doi.org/10.1158/0008-5472.CAN-14-2394DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4417413PMC
May 2015

WWOX: a fragile tumor suppressor.

Exp Biol Med (Maywood) 2015 Mar 22;240(3):296-304. Epub 2014 Dec 22.

Department of Molecular Virology, Immunology and Medical Genetics, Comprehensive Cancer Center, Ohio State University Wexner Medical Center, Columbus, Ohio 43210, USA

WWOX, the WW domain-containing oxidoreductase gene at chromosome region 16q23.3-q24.1, spanning chromosomal fragile site FRA16D, encodes the 46 kDa Wwox protein, a tumor suppressor that is lost or reduced in expression in a wide variety of cancers, including breast, prostate, ovarian, and lung. The function of Wwox as a tumor suppressor implies that it serves a function in the prevention of carcinogenesis. Indeed, in vitro studies show that Wwox protein interacts with many binding partners to regulate cellular apoptosis, proliferation, and/or maturation. It has been reported that newborn Wwox knockout mice exhibit nascent osteosarcomas while Wwox(+/-) mice exhibit increased incidence of spontaneous and induced tumors. Furthermore, absence or reduction of Wwox expression in mouse xenograft models results in increased tumorigenesis, which can be rescued by Wwox re-expression, though there is not universal agreement among investigators regarding the role of Wwox loss in these experimental models. Despite this proposed tumor suppressor function, the overlap of the human WWOX locus with FRA16D sensitizes the gene to protein-inactivating deletions caused by replication stress. The high frequency of deletions within the WWOX locus in cancers of various types, without the hallmark protein inactivation-associated mutations of "classical" tumor suppressors, has led to the proposal that WWOX deletions in cancers are passenger events that occur in early cancer progenitor cells due to fragility of the genetic locus, rather than driver events which provide the cancer cell a selective advantage. Recently, a proposed epigenetic cause of chromosomal fragility has suggested a novel mechanism for early fragile site instability and has implications regarding the involvement of tumor suppressor genes at chromosomal fragile sites in cancer. In this review, we provide an overview of the evidence for WWOX as a tumor suppressor gene and put this into the context of fragility associated with the FRA16D locus.
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http://dx.doi.org/10.1177/1535370214561590DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4471953PMC
March 2015

FHIT loss-induced DNA damage creates optimal APOBEC substrates: Insights into APOBEC-mediated mutagenesis.

Oncotarget 2015 Feb;6(5):3409-19

Department of Molecular Virology, Immunology and Medical Genetics, Comprehensive Cancer Center, Ohio State University Wexner Medical Center, Columbus, Ohio, USA.

APOBEC cytidine deaminase activity is a major source of hypermutation in cancer. But previous studies have shown that the TC context signature of these enzymes is not observed in sizable fractions of cancers with overexpression of APOBEC, suggesting that cooperating factors that contribute to this mutagenesis should be identified. The fragile histidine triad protein (Fhit) is a tumor suppressor and DNA caretaker that is deleted or silenced in >50% of cancers. Loss of Fhit protein activity causes replication stress through reduced Thymidine Kinase 1 expression, increased DNA breaks, and global genome instability in normal and cancer cells. Using data from The Cancer Genome Atlas (TCGA), we show that FHIT-low/APOBEC3B-high expressing lung adenocarcinomas display significantly increased numbers of APOBEC signature mutations. Tumor samples in this cohort with normal FHIT expression do not exhibit APOBEC hypermutation, despite having high APOBEC3B expression. In vitro, silencing Fhit expression elevates APOBEC3B-directed C > T mutations in the TP53 gene. Furthermore, inhibition of Fhit loss-induced DNA damage via thymidine supplementation decreases the TP53 mutation burden in FHIT-low/APOBEC3B-high cells. We conclude that APOBEC3B overexpression and Fhit-loss induced DNA damage are independent events that, when occurring together, result in a significantly increased frequency of APOBEC-induced mutations that drive cancer progression.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4413662PMC
http://dx.doi.org/10.18632/oncotarget.2636DOI Listing
February 2015

FHIT suppresses epithelial-mesenchymal transition (EMT) and metastasis in lung cancer through modulation of microRNAs.

PLoS Genet 2014 Oct 23;10(10):e1004652. Epub 2014 Oct 23.

Department of Molecular Virology, Immunology and Medical Genetics, and Comprehensive Cancer Center, Ohio State University, Columbus, Ohio, United States of America.

Metastasis is the principal cause of cancer death and occurs through multiple, complex processes that involve the concerted action of many genes. A number of studies have indicated that the Fragile Histidine Triad (FHIT) gene product, FHIT, functions as a tumor suppressor in a variety of common human cancers. Although there are suggestions of a role for FHIT loss in progression of various cancers, a role for such loss in metastasis has not been defined. Here, via in vivo and in vitro assays, we reveal that the enforced expression of FHIT significantly suppresses metastasis, accompanied by inhibition of the epithelial-mesenchymal transition (EMT), a process involved in metastasis through coordinate modulation of EMT-related genes. Specifically, miR-30c, a FHIT-upregulated microRNA, contributes to FHIT function in suppression of EMT and metastasis by directly targeting metastasis genes Metadherin (MTDH), High-mobility group AT-hook 2 (HMGA2), and the mesenchymal markers, Vimentin (VIM) and Fibronectin (FN1), in human lung cancer. Finally, we demonstrate that the expression pattern of FHIT and miR-30c is inversely correlated with that of MTDH and HMGA2 in normal tissue, non-metastatic and metastatic tumors, serving as a potential biomarker for metastasis in lung cancer.
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http://dx.doi.org/10.1371/journal.pgen.1004652DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4207614PMC
October 2014

Pluripotent stem cell miRNAs and metastasis in invasive breast cancer.

J Natl Cancer Inst 2014 Dec 11;106(12). Epub 2014 Oct 11.

Department of Molecular Virology, Immunology and Molecular Genetics, Comprehensive Cancer Center, The Ohio State University, Columbus, OH (SV, GN, AD, SC, MiG, RAe, RG, GDL, PG, PD, TW, SEW, FP, NZ, HA, KFH, CMC); Biosystems Analysis, LTTA, Deptartment of Morphology, Surgery and Experimental Medicine, University of Ferrara, Ferrara, Italy, (SV, MES, JM, MaG, MM, CZ, FC, MP, JP, MN); Fate Therapeutics, San Diego, CA (RAb); Department of Chemistry, The Scripps Research Institute, La Jolla, CA (CD); Department of Urology, Thomas Jefferson University, Kimmel Cancer Center, Philadelphia, PA (RB); Comprehensive Cancer Center, The Ohio State University, Columbus, OH (KM); Deptartment of Internal Medicine, James Cancer Hospital and Ohio State University Comprehensive Cancer Center, The Ohio State University (CLS); Division of Pathology, II University of Rome "La Sapienza," Ospedale Santo Andrea, Rome, Italy (AV); Department of Surgery, Thomas Jefferson University Medical College, Philadelphia, PA (ALR).

Background: The purpose of this study is to determine whether microRNA for pluripotent stem cells are also expressed in breast cancer and are associated with metastasis and outcome.

Methods: We studied global microRNA profiles during differentiation of human embryonic stem cells (n =26) and in breast cancer patients (n = 33) and human cell lines (n = 35). Using in situ hybridization, we then investigated MIR302 expression in 318 untreated breast cancer patients (test cohort, n = 22 and validation cohort, n = 296). In parallel, using next-generation sequencing data from breast cancer patients (n = 684), we assessed microRNA association with stem cell markers. All statistical tests were two-sided.

Results: In healthy tissues, the MIR302 (high)/MIR203 (low) asymmetry was exclusive for pluripotent stem cells. MIR302 was expressed in a small population of cancer cells within invasive ductal carcinoma, but not in normal breast (P < .001). Furthermore, MIR302 was expressed in the tumor cells together with stem cell markers, such as CD44 and BMI1. Conversely, MIR203 expression in 684 breast tumors negatively correlated with CD44 (Spearman correlation, Rho = -0.08, P = .04) and BMI1 (Rho = -0.11, P = .004), but positively correlated with differentiation marker CD24 (Rho = 0.15, P < .001). Primary tumors with lymph node metastasis had cancer cells showing scattered expression of MIR302 and widespread repression of MIR203. Finally, overall survival was statistically significantly shorter in patients with MIR302-positive cancer cells (P = .03).

Conclusions: In healthy tissues the MIR302(high)/MIR203(low) asymmetry was characteristic of embryonic and induced pluripotency. In invasive ductal carcinoma, the MIR302/MIR203 asymmetry was associated with stem cell markers, metastasis, and shorter survival.
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http://dx.doi.org/10.1093/jnci/dju324DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4334797PMC
December 2014

The FHIT gene product: tumor suppressor and genome "caretaker".

Cell Mol Life Sci 2014 Dec 5;71(23):4577-87. Epub 2014 Oct 5.

Biomedical Sciences Graduate Program, Ohio State University Wexner Medical Center, Columbus, OH, USA.

The FHIT gene at FRA3B is one of the earliest and most frequently altered genes in the majority of human cancers. It was recently discovered that the FHIT gene is not the most fragile locus in epithelial cells, the cell of origin for most Fhit-negative cancers, eroding support for past claims that deletions at this locus are simply passenger events that are carried along in expanding cancer clones, due to extreme vulnerability to DNA damage rather than to loss of FHIT function. Indeed, recent reports have reconfirmed FHIT as a tumor suppressor gene with roles in apoptosis and prevention of the epithelial-mesenchymal transition. Other recent works have identified a novel role for the FHIT gene product, Fhit, as a genome "caretaker." Loss of this caretaker function leads to nucleotide imbalance, spontaneous replication stress, and DNA breaks. Because Fhit loss-induced DNA damage is "checkpoint blind," cells accumulate further DNA damage during subsequent cell cycles, accruing global genome instability that could facilitate oncogenic mutation acquisition and expedite clonal expansion. Loss of Fhit activity therefore induces a mutator phenotype. Evidence for FHIT as a mutator gene is discussed in light of these recent investigations of Fhit loss and subsequent genome instability.
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http://dx.doi.org/10.1007/s00018-014-1722-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4233150PMC
December 2014

Replicative Stress and the FHIT Gene: Roles in Tumor Suppression, Genome Stability and Prevention of Carcinogenesis.

Cancers (Basel) 2014 Jun 4;6(2):1208-19. Epub 2014 Jun 4.

Department of Molecular Virology, Immunology and Medical Genetics, The Ohio State University Wexner Medical Center, Columbus, OH 43210, USA.

The fragile FHIT gene, encompassing the chromosomal fragile site FRA3B, is an early target of DNA damage in precancerous cells. While vulnerable to DNA damage itself, FHIT protein expression is essential to protect from DNA damage-induced cancer initiation and progression by modulating genome stability, oxidative stress and levels of accumulating DNA damage. Thus, FHIT, whose expression is lost or reduced in many human cancers, is a tumor suppressor and genome caretaker whose loss initiates genome instability in preneoplastic lesions. Ongoing studies are seeking more detailed understanding of the role of FHIT in the cellular response to oxidative damage. This review discusses the relationship between FHIT, reactive oxygen species production, and DNA damage in the context of cancer initiation and progression.
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http://dx.doi.org/10.3390/cancers6021208DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4074825PMC
June 2014

microRNA expression profiling identifies a four microRNA signature as a novel diagnostic and prognostic biomarker in triple negative breast cancers.

Oncotarget 2014 Mar;5(5):1174-84

Triple Negative Breast Cancers (TNBC) is a heterogeneous disease at the molecular and clinical level with poor outcome. Molecular subclassification of TNBCs is essential for optimal use of current therapies and for development of new drugs. microRNAs (miRNA) are widely recognized as key players in cancer progression and drug resistance; investigation of their involvement in a TNBC cohort may reveal biomarkers for diagnosis and prognosis of TNBC. Here we stratified a large TNBC cohort into Core Basal (CB, EGFR and/or CK5, 6 positive) and five negative (5NP) if all markers are negative. We determined the complete miRNA expression profile and found a subset of miRNAs specifically deregulated in the two subclasses.We identified a 4-miRNA signature given by miR-155, miR-493, miR-30e and miR-27a expression levels, that allowed subdivision of TNBCs not only into CB and 5NP subgroups (sensitivity 0.75 and specificity 0.56; AUC=0.74) but also into high risk and low risk groups. We tested the diagnostic and prognostic performances of both the 5 IHC marker panel and the 4-miRNA expression signatures, which clearly identify worse outcome patients in the treated and untreated subcohorts. Both signatures have diagnostic and prognostic value, predicting outcomes of patient treatment with the two most commonly used chemotherapy regimens in TNBC: anthracycline or anthracycline plus taxanes. Further investigations of the patients’ overall survival treated with these regimens show that regardless of IHC group subdivision, taxanes addition did not benefit patients, possibly due to miRNA driven taxanes resistance. TNBC subclassification based on the 5 IHC markers and on the miR-155, miR-493, miR-30e, miR-27a expression levels are powerful diagnostic tools. Treatment choice and new drug development should consider this new subtyping and miRNA expression signature in planning low toxicity, maximum efficacy therapies.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4012726PMC
http://dx.doi.org/10.18632/oncotarget.1682DOI Listing
March 2014

Protective role of miR-155 in breast cancer through RAD51 targeting impairs homologous recombination after irradiation.

Proc Natl Acad Sci U S A 2014 Mar 10;111(12):4536-41. Epub 2014 Mar 10.

Department of Molecular Virology, Immunology and Medical Genetics, Wexner Medical Center and Comprehensive Cancer Center, The Ohio State University, Columbus, OH 43210.

Cell survival after DNA damage relies on DNA repair, the abrogation of which causes genomic instability and development of cancer. However, defective DNA repair in cancer cells can be exploited for cancer therapy using DNA-damaging agents. DNA double-strand breaks are the major lethal lesions induced by ionizing radiation (IR) and can be efficiently repaired by DNA homologous recombination, a system that requires numerous factors including the recombinase RAD51 (RAD51). Therapies combined with adjuvant radiotherapy have been demonstrated to improve the survival of triple-negative breast cancer patients; however, such therapy is challenged by the emergence of resistance in tumor cells. It is, therefore, essential to develop novel therapeutic strategies to overcome radioresistance and improve radiosensitivity. In this study we show that overexpression of microRNA 155 (miR-155) in human breast cancer cells reduces the levels of RAD51 and affects the cellular response to IR. miR-155 directly targets the 3'-untranslated region of RAD51. Overexpression of miR-155 decreased the efficiency of homologous recombination repair and enhanced sensitivity to IR in vitro and in vivo. High miR-155 levels were associated with lower RAD51 expression and with better overall survival of patients in a large series of triple-negative breast cancers. Taken together, our findings indicate that miR-155 regulates DNA repair activity and sensitivity to IR by repressing RAD51 in breast cancer. Testing for expression levels of miR-155 may be useful in the identification of breast cancer patients who will benefit from an IR-based therapeutic approach.
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http://dx.doi.org/10.1073/pnas.1402604111DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3970505PMC
March 2014

Histone H1 phosphorylation in breast cancer.

J Proteome Res 2014 May 7;13(5):2453-67. Epub 2014 Apr 7.

Department of Molecular Virology, Immunology and Medical Genetics, ‡Comprehensive Cancer Center, §Department of Chemistry & Biochemistry, ⊥Veterinary Biosciences, College of Veterinary Medicine, and ∥Department of Internal Medicine, Division of Hematology, The Ohio State University , Columbus, Ohio 43210, United States.

Breast cancer is the second leading cause of cancer-related deaths in women. The need for new clinical biomarkers in breast cancer is necessary to further predict prognosis and therapeutic response. In this article, the LC-MS histone H1 phosphorylation profiles were established for three distinct breast cancer cell lines. The results show that the extent of H1 phosphorylation can distinguish between the different cell lines. The histone H1 from the metastatic cell line, MDA-MB-231, was subjected to chemical derivitization and LC-MS/MS analysis. The results suggest that the phosphorylation at threonine 146 is found on both histone H1.2 and histone H1.4. Cell lines were then treated with an extracellular stimulus, estradiol or kinase inhibitor LY294002, to monitor changes in histone H1 phosphorylation. The data show that histone H1 phosphorylation can increase and decrease in response to extracellular stimuli. Finally, primary breast tissues were stained for the histone H1 phosphorylation at threonine 146. Variable staining patterns across tumor grades and subtypes were observed with pT146 labeling correlating with tumor grade. These results establish the potential for histone H1 phosphorylation at threonine 146 as a clinical biomarker in breast cancer.
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http://dx.doi.org/10.1021/pr401248fDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4012839PMC
May 2014

Androgen receptor status is a prognostic marker in non-basal triple negative breast cancers and determines novel therapeutic options.

PLoS One 2014 5;9(2):e88525. Epub 2014 Feb 5.

Department of Molecular Virology, Immunology and Medical Genetics, Ohio State University Wexner Medical Center and Comprehensive Cancer Center, Columbus, Ohio, United States of America.

Triple negative breast cancers are a heterogeneous group of tumors characterized by poor patient survival and lack of targeted therapeutics. Androgen receptor has been associated with triple negative breast cancer pathogenesis, but its role in the different subtypes has not been clearly defined. We examined androgen receptor protein expression by immunohistochemical analysis in 678 breast cancers, including 396 triple negative cancers. Fifty matched lymph node metastases were also examined. Association of expression status with clinical (race, survival) and pathological (basal, non-basal subtype, stage, grade) features was also evaluated. In 160 triple negative breast cancers, mRNA microarray expression profiling was performed, and differences according to androgen receptor status were analyzed. In triple negative cancers the percentage of androgen receptor positive cases was lower (24.8% vs 81.6% of non-triple negative cases), especially in African American women (16.7% vs 25.5% of cancers of white women). No significant difference in androgen receptor expression was observed in primary tumors vs matched metastatic lesions. Positive androgen receptor immunoreactivity was inversely correlated with tumor grade (p<0.01) and associated with better overall patient survival (p = 0.032) in the non-basal triple negative cancer group. In the microarray study, expression of three genes (HER4, TNFSF10, CDK6) showed significant deregulation in association with androgen receptor status; eg CDK6, a novel therapeutic target in triple negative cancers, showed significantly higher expression level in androgen receptor negative cases (p<0.01). These findings confirm the prognostic impact of androgen receptor expression in non-basal triple negative breast cancers, and suggest targeting of new androgen receptor-related molecular pathways in patients with these cancers.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0088525PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3914993PMC
September 2014

Fhit deficiency-induced global genome instability promotes mutation and clonal expansion.

PLoS One 2013 14;8(11):e80730. Epub 2013 Nov 14.

Department of Molecular Virology, Immunology and Medical Genetics, Ohio State University Wexner Medical Center, Columbus, Ohio, United States of America.

Loss of Fhit expression, encoded at chromosome fragile site FRA3B, leads to increased replication stress, genome instability and accumulation of genetic alterations. We have proposed that Fhit is a genome 'caretaker' whose loss initiates genome instability in preneoplastic lesions. We have characterized allele copy number alterations and expression changes observed in Fhit-deficient cells in conjunction with alterations in cellular proliferation and exome mutations, using cells from mouse embryo fibroblasts (MEFs), mouse kidney, early and late after establishment in culture, and in response to carcinogen treatment. Fhit (-/-) MEFs escape senescence to become immortal more rapidly than Fhit (+/+) MEFs; -/- MEFs and kidney cultures show allele losses and gains, while +/+ derived cells show few genomic alterations. Striking alterations in expression of p53, p21, Mcl1 and active caspase 3 occurred in mouse kidney -/- cells during progressive tissue culture passage. To define genomic changes associated with preneoplastic changes in vivo, exome DNAs were sequenced for +/+ and -/- liver tissue after treatment of mice with the carcinogen, 7,12-dimethylbenz[a]anthracene, and for +/+ and -/- kidney cells treated in vitro with this carcinogen. The -/- exome DNAs, in comparison with +/+ DNA, showed small insertions, deletions and point mutations in more genes, some likely related to preneoplastic changes. Thus, Fhit loss provides a 'mutator' phenotype, a cellular environment in which mild genome instability permits clonal expansion, through proliferative advantage and escape from apoptosis, in response to pressures to survive.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0080730PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3828255PMC
February 2015

Common chromosome fragile sites in human and murine epithelial cells and FHIT/FRA3B loss-induced global genome instability.

Genes Chromosomes Cancer 2013 Nov 9;52(11):1017-29. Epub 2013 Aug 9.

Department of Molecular Virology, Immunology and Medical Genetics, The Ohio State University Wexner Medical Center, Columbus, OH.

Chromosomal positions of common fragile sites differ in lymphoblasts and fibroblasts, with positions dependent on the epigenetically determined density of replication origins at these loci. Because rearrangement of fragile loci and associated loss of fragile gene products are hallmarks of cancers, we aimed to map common fragile sites in epithelial cells, from which most cancers derive. Among the five most frequently activated sites in human epithelial cells were chromosome bands 2q33 and Xq22.1, which are not among top fragile sites identified in lymphoblasts or fibroblasts. FRA16D at 16q23 was among the top three fragile sites in the human epithelial cells examined, as it is in lymphoblasts and fibroblasts, while FRA3B at 3p14.2, the top fragile locus in lymphoblasts, was not fragile in most epithelial cell lines tested. Epithelial cells exhibited varying hierarchies of fragile sites; some frequent epithelial cell fragile sites are apparently not frequently altered in epithelial cancers and sites that are frequently deleted in epithelial cancers are not necessarily among the most fragile. Since we have reported that loss of expression of the FRA3B-encoded FHIT protein causes increased replication stress-induced DNA damage, we also examined the effect of FHIT-deficiency on markers of genome instability in epithelial cells. FHIT-deficient cells exhibited increases in fragile breaks and in γH2AX and 53BP1 foci in G1 phase cells, confirming in epithelial cells that the FHIT gene and encompassing FRA3B, is a "caretaker gene" necessary for maintenance of genome stability.
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http://dx.doi.org/10.1002/gcc.22097DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4293015PMC
November 2013
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