Estefania Labanca

Association of HO-1 and BRCA1 Is Critical for the Maintenance of Cellular Homeostasis in Prostate Cancer

Prostate cancer is the second leading cause of cancer-related death in men worldwide. Many factors that participate in the development of prostate cancer promote imbalance in the redox state of the cell. Accumulation of reactive oxygen species causes injury to cell structures, ultimately leading to cancer development. The antioxidant enzyme heme oxygenase 1 (HMOX1/HO-1) is responsible for the maintenance of the cellular homeostasis, playing a critical role in the oxidative stress and the regulation of prostate cancer development and progression. In the present study, the transcriptional regulation of HO-1 was investigated in prostate cancer. Interestingly, the tumor suppressor BRCA1 binds to the HO-1 promoter and modulates HO-1, inducing its protein levels through both the increment of its promoter activity and the induction of its transcriptional activation. In addition, in vitro and in vivo analyses show that BRCA1 also controls HO-1–negative targets: MMP9, uPA, and Cyclin D1. HO-1 transcriptional regulation is also modulated by oxidative and genotoxic agents. Induction of DNA damage by mitoxantrone and etoposide repressed HO-1 transcription, whereas hydrogen peroxide and doxorubicin induced its expression. Xenograft studies showed that HO-1 regulation by doxorubicin also occurs in vivo. Immunofluorescence analysis revealed that BRCA1 overexpression and/or doxorubicin exposure induced the cytoplasmic retention of HO-1. Finally, the transcription factor NRF2 cooperates with BRCA1 protein to activate HO-1 promoter activity. In summary, these results show that the activation of BRCA1–NRF2/HO-1 axis defines a new mechanism for the maintenance of the cellular homeostasis in prostate cancer. Implications: Oxidative and genotoxic stress converge on HO-1 transcriptional activity through the combined actions of BRCA1 and NRF2. Mol Cancer Res; 13(11); 1455–64. ©2015 AACR.

Modeling Cancer Metastasis

Cancer metastases constitute a therapy-resistant stage in most cases; thus, the study of mechanisms underlying the metastatic process is a subject of intense research. With the recognition of patient-derived xenografts (PDXs) as being clinically relevant, in this chapter we describe methods to model specific stages of the metastatic cascade using PDXs. In particular we emphasize the processing of PDXs for in vitro studies to investigate migration, invasion, and cancer cell-stromal cell interaction. In vivo, we describe methods to implant cancer cells into the left ventricle (to study dissemination of cancer cells in the blood stream while bypassing the initial steps of metastases) and the direct implantation of cancer cells in the femur of immunodeficient mice (for cancer cell-bone interaction and preclinical studies). We also describe methods to evaluate these in vivo assays and outline basic concepts and methods of intravital microscopy to study early stages of metastases.

Abstract A019: Heme-oxygenase 1 drives the metabolic fate in prostate cancer

Prostate cancer (PCa) is the second leading cause of cancer-associated death in men. Energetic metabolism alterations have become a new hallmark of cancer, since variations in a single gene can orchestrate changes in metabolic pathways and confer an adaptive advantage. Heme-oxygenase 1 (HO-1) exerts an antitumoral role in PCa inhibiting cell proliferation, migration, tumor growth, and angiogenesis. The aim of this work was to assess the role of HO-1 in the metabolic signature of PCa. Through RNA-Seq we found a set of metabolic genes deregulated under pharmacologic induction (hemin treatment) or genetic induction of HO-1 in PC3 cells. STAR and ATP5L2 were upregulated, while HMGCS2, PRODH, and ACOT12 were downregulated. These genes encode for steroid hormone metabolism, ATP synthesis, ketogenesis, proline and lipid metabolism. The analysis of the deregulated genes (2-fold) by Gene Ontology revealed alterations in several metabolic pathways such as steroid, proline and lipid metabolism, and ATP synthesis. Functional analysis highlighted a decrease in oxygen consumption rate and ATP production under hemin treatment. Furthermore, HO-1 induction led to a decrease in the extracellular lactate levels. Bone is the only site of PCa progression, and bone cells are able to produce factors that favor progression. However, the molecular nature of this interaction remains elusive. Our results performed on cocultures of PC3 cells (treated or not with hemin) with Raw264.7 (preosteoclastic) or MC3T3 (preosteoblastic) cells demonstrate that HO-1 directs the metabolic fate of bone precursor cells due to the deregulation of glycolytic genes. HO-1 induction in PC3 cells downregulated PKM2 and LDHA expression in cocultured Raw264.7 and MC3T3 cells (p Based on our results, we propose HO-1 as a key regulator of the metabolic status of PCa cells and a powerful mediator capable of redefining the metabolic signature of bone precursor cells, thus favoring the establishment of a less aggressive phenotype. Citation Format: Valeria G. Antico Arciuch, Florencia Cascardo, Florencia Velazquez, Sofia Lage Vickers, Nicolas Anselmino, Estefania Labanca, Javier Cotignola, Geraldine Gueron, Nora Navone, Elba Vazquez. Heme-oxygenase 1 drives the metabolic fate in prostate cancer [abstract]. In: Proceedings of the AACR Special Conference: Prostate Cancer: Advances in Basic, Translational, and Clinical Research; 2017 Dec 2-5; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(16 Suppl):Abstract nr A019.

Abstract A026: Expression of fibroblast growth factor receptor 1 isoforms and activation of different pathways in prostate cancer progression

Bone metastases typically develop in patients with advanced prostate cancer (PCa). Androgen deprivation is commonly used as treatment, but responses are short, and eventually the disease progresses to a castration-resistant form (CRPC). The fibroblast growth factor (FGF) axis is commonly altered during PCa progression. Our group and others have implicated the FGF axis in the pathogenesis of PCa progression in bone, identified it as a candidate target for therapy, and suggested that FGF receptor (FGFR)-1 mediates a positive feedback loop between PCa cells and bone cells. RNA sequencing studies of 183 human PCa samples indicated that the mean expression of FGFR-1 is the highest of all the FGFR family genes studied. Analyses of these FGFR-1 transcripts identified eight different protein-coding transcripts to be the most abundantly expressed with diverse human PCa tissue samples expressing different FGFR-1 isoforms. The overall goal of this project is to investigate implications of FGFR1/FGFR1 isoforms expression in the pathogenesis of PCa bone metastases. When we assessed the expression of the two best-characterized FGFR-1 isoforms (alpha (NM_023110.2) and beta (NM_023105.2), which represent the most abundant protein coding transcripts found in PCa, we observed that all patient-derived xenografts (PDXs) studied express significantly higher levels of FGFR-1 alpha than beta while PCa cell lines mostly express the beta isoform. Mining The Cancer Genome Atlas (TCGA) PCa data, we identified distinct patterns of gene expression associated with each FGFR-1 isoform (alpha and beta). Briefly, FGFR-1 beta (but not alpha) is significantly associated with pathways including the MAP-kinase signaling cascade, signaling by FGFR in disease and pathways in cancer. In vitro studies of FGF signaling activation in PCa cells expressing FGFR-1 isoforms alpha, beta or empty vector, confirmed these results. Male SCID mice injected intracardially with PC3-FGFR-1 alpha exhibited higher death rates compared to animals injected with either PC3-FGFR-1 beta or PC3-empty vector. Furthermore, higher number of metastases per mice as well as higher number of mice with bone metastases were observed in animals injected with PC3-FGFR-1 alpha. The fact that different prostate tumors express different FGFR-1 isoforms suggests that FGFR1 alpha and beta isoforms activate different genes or pathways in PCa cells and this may underlie, at least in part, PCa heterogeneity, pattern of progression, and differences in response to FGFR1 inhibitors. Further studies will warrant the understanding of the implications of FGFR-1 isoforms expression in the pathogenesis of PCa. Citation Format: Estefania Labanca, Jun Yang, Peter Shepherd, Justin Roberts, Michael Starbuck, Bradley Broom, Matthew Iyer, Christopher Logothetis, Arul Chinnaiyan, Nora Navone. Expression of fibroblast growth factor receptor 1 isoforms and activation of different pathways in prostate cancer progression [abstract]. In: Proceedings of the AACR Special Conference: Prostate Cancer: Advances in Basic, Translational, and Clinical Research; 2017 Dec 2-5; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(16 Suppl):Abstract nr A026.

Abstract A03: Analyses of a prostate cancer patient-derived xenografts series, a resource for translational research

Patients with metastatic prostate cancer (PCa) have effective therapy options, but none of them are curative. Thus, their mortality rates are persistently high. Essential to furthering our progress in PCa research and therapy development is a spectrum of models that reflect the heterogeneity of the disease at each tumor site as well as the different histological variants of PCa (e.g., adenocarcinoma, small cell carcinoma). To address this challenge, we developed a strategy to establish PCa patient-derived xenografts (PDXs), using PCa tissue specimens taken from PCa sites demonstrating clinical progression. This approach provided a diverse repository of PDXs that can be linked prospectively with clinical progression and led to the identification of clinically relevant therapy targets and have proven valuable for testing drugs. We studied the first 50 PDXs developed under our program to a) define the histopathological features of paired human PCa and corresponding PDXs applying the clinically defined morphological characterization groupings of human cancer to the PDX tumors; b) assess the expression of genes known to play roles in PCa pathogenesis (e.g., androgen receptor, PTEN, ETS gene fusions) in PDXs and the human tumors of origin using immunohistochemistry and fluorescence in situ hybridization and c) perform array comparative genomic hybridization to 42 PDXs. We found that the histopathological and molecular pattern of these PDXs maintain the fidelity with the human tumor of origin. Furthermore, of the 50 cases studied, 32 (64%) were adenocarcinomas, and 16 (32%) were small cell carcinomas, poorly differentiated neuroendocrine carcinomas or mixed adenocarcinoma/ small cell carcinomas. In our cohort, we also have one sarcomatoid tumor and one ductal adenocarcinoma. Of the 32 adenocarcinomas in this cohort, 26 were AR-positive (81%), and 11 of the 27 AR-positive adenocarcinomas (41%) had aberrant expression of genes frequently involved in recurrent rearrangement (e.g., ERG, ETV1, ETV5). Also, SCCs and poorly differentiated neuroendocrine carcinomas did not express AR and were negative for ERG. This distribution recapitulates that of human PCa in the general population. Comparative genomic hybridization demonstrated gains and losses previously reported in PCa with a defined cluster of genomic aberrations. Significant differences in oncogenic pathways activation in pairs of PDXs derived from different areas of the same tumor suggesting divergent cellular progression. Finally, using this platform, we identified a focal deletion of speckle-type POZ protein-like (SPOPL) gene in 7/28 PDX. SPOPL is a MATH-BTB protein that shares an overall 85% sequence identity with SPOP (a SPOPL paralog). SPOP was recently reported to be mutated in about 8% of PCa and to define a molecular subclass of PCa. No mutations were found in SPOP in our cohort. In support of our findings, deletions on SPOPL were also found in about 7% of the PCa in TCGA data suggesting that our cohort is a reliable platform for discovery. In conclusion, we have developed a dynamic repository of clinically annotated samples that can be used as a discovery platform. Furthermore, these clinically annotated samples can be linked prospectively to clinical progression/response to therapy and thus will help define therapeutic targets for subpopulations of men and to identify likely responders to previous and upcoming therapies. Citation Format: Nallasivam Palanisamy, Jun Yang, Xinhai Wan, Elsa M. li Ning Tapia, John C. Araujo, Eleni Efstathiou, Estefania Labanca, Louis Pisters, Ana Aparicio, Ritu Bhalla, Scott Tomlins, Lakshmi P. Kunju, Arul Chinnaiyan, Christopher J. Logothetis, Patricia Troncoso, Nora M. Navone. Analyses of a prostate cancer patient-derived xenografts series, a resource for translational research. [abstract]. In: Proceedings of the AACR Special Conference: Patient-Derived Cancer Models: Present and Future Applications from Basic Science to the Clinic; Feb 11-14, 2016; New Orleans, LA. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(16_Suppl):Abstract nr A03.

Abstract 5058: Hitting the brakes on the migratory capacity of tumoral cells: Targeting key regulators of actin dynamics in prostate cancer

Prostate Cancer (PCa) is the second leading cause of cancer in men. PCa cells display abnormal expression of cytoskeletal proteins resulting in an augmented capacity to resist chemotherapy and colonize other organs. We have previously shown that heme-oxygenase 1 (HO-1) has a strong anti-tumoral effect in prostate cancer (PCa) and regulates the adhesive properties of PCa cells. Innovative high-throughput proteomic platforms are now identifying and quantifying new specific and sensitive biomarkers for PCa detection, stratification and treatment. Towards this end, we undertook an in-depth mass spectrometry-based proteomics study to build the Heme-oxygenase 1 (HO-1) interactome in PCa, in an effort to identify HO-1 molecular partners associated to the integrity of the cellular architecture and assess actin dynamics of PCa cells under HO-1 modulation. The proteomics analysis of HO-1 interacting proteins yielded several cytoskeletal-associated proteins regulating actin filament dynamics, such as gelsolin, lasp1, SIPA1L1, testin, moesin, tropomodulin and vinculin. The bioinformatics screening across the Oncomine platform revealed that the RNA expression profiles of the cytoskeletal HO-1 interacting proteins, lie within the 10 percent of the most consistently low-expressed genes in prostate adenocarcinoma compared to normal tissue. Motility changes were assessed on fiber-like 2D migration scenarios displaying a reduced frequency in migration events and in migration speed under hemin exposure, a specific pharmacological inducer of HO-1. A significant higher proportion of filopodia-like protrusions among neighboring cells and cellular contacts were observed when HO-1 was induced; effects reversed under HO-1 silencing. Altogether, our experimental findings demonstrate that HO-1 modulation in PCa induces the remodeling of the actin filament architecture at filopodia, alters the migratory patterns and cellular morphology, showcasing the relevance of the cytoskeletal proteins as potential therapeutic targets against the aggressive and metastatic disease. Citation Format: Alejandra V. Paez, Carla Pallavicini, Federico Schuster, Jimena Giudice, Pia Valacco, Estefania Labanca, Nicolas Anselmino, Emiliano Ortiz, Maria Binaghi, Javier Cotignola, Marcelo Marti, Luciana Bruno, Valeria Levi, Nora Navone, Elba Vazquez, Geraldine Gueron. Hitting the brakes on the migratory capacity of tumoral cells: Targeting key regulators of actin dynamics in prostate cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5058.

Abstract 4717: Clinical implications for m-tyrosine, an isomer of p-tyrosine, for the treatment of aggressive prostate tumors

Clinical and experimental evidence suggest that primary tumors may exert a controlling action on its metastases. The phenomenon, by which a tumor-bearing host is resistant to the growth of secondary tumor implants and metastasis, is known as concomitant tumor resistance (CR). We have previously showed in murine T-lymphoma (LB) tumors, that meta-tyrosine (m-Tyr) an isomer of tyrosine not present in normal proteins, is the main serum anti-tumoral factor responsible for CR. In this work, we assess for the first time the CR phenomenon in human prostate cancer (PCa). Athymic nude mice were inoculated with PC3 cells (primary implant) and after 14 days the animals received a second inoculation (secondary implant). Strikingly, the growth of the secondary implant was significantly reduced after 27 days, in animals carrying the primary xenograft. When phenylalanine (Phe), a protective amino acid highly present in primary tumors, and precursor of p-tyrosine, was periodically inoculated at the site of a secondary tumor implant (otherwise inhibited by CR), this secondary implant grew similarly to controls. On the contrary, when m-Tyr was inoculated at the site of a primary tumor implant or systemically, this implant did not grow. Tumor inhibition was associated with low expression of Ki-67 and STAT3. In vitro analyses demonstrate the higher inhibitory activity of the serum from tumor-bearing mice on PC3 cell proliferation, compared to serum from control animals. m-Tyr could account for most of the growth-inhibitory activity present in the serum. Furthermore, we observed an increase in the frequency of Gr1+ CD11b+ MDSCs in bone marrow, spleen and lymph nodes from tumor-bearing mice compared to control mice. This expansion correlated with a significantly higher production of reactive oxygen species and enhanced suppressor function upon CD8+ T cell proliferation. Further, in vitro studies also showed that exposure of PC3 cells to m-Tyr inhibited cell growth, induced G0/G1 cell cycle arrest, altered the expression levels of survivin, Ki67 and Hes1; impaired the NFκB/STAT3 pathway and induced autophagy; effects reversed by Phe treatment. Strikingly, m-Tyr periodic intravenous administration provoked a dramatic reduction of experimental lung metastases generated in mice bearing PC3 human tumors. Altogether, we demonstrate for the first time that RC occurs in experimental human solid tumors, that this effect is mediated by m-Tyr, a non-cytotoxic metabolite with high potential clinical implications for metastatic PCa. Citation Format: Geraldine Gueron, Nicolas Anselmino, Paula Chiarella, Emiliano Ortiz, Alejandra Paez, Jimena Giudice, Federico Schuster, Daiana Leonardi, Felipe Jaworski, Estefania Labanca, Veronica Manzano, Javier Cotignola, Roberto Meiss, Norma D′Accorso, Nora Navone, Raul Ruggiero, Elba Vazquez. Clinical implications for m-tyrosine, an isomer of p-tyrosine, for the treatment of aggressive prostate tumors. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4717.

Abstract 1871: Alpha and beta isoforms of fibroblast growth factor receptor 1 in prostate cancer

Castrate-resistant progression and bone metastases are hallmarks of advanced prostate cancer (PCa). The fibroblast growth factor (FGF)/FGF receptor (FGFR) complex mediates tumor-stromal interactions and is commonly altered in PCa. FGFR1, FGFR2, FGFR3, and FGFR4 genes encode alternatively spliced variants of FGFRs that vary in the extracellular ligand-binding and intracellular kinase domains. A published study from our group implicated FGFR1 as a therapy target for PCa bone metastases (STM 2014; 6:252ra122). Further, our studies of FGFR1 transcripts by RNA sequencing of 183 human PCas identified eight different protein coding transcripts as the most abundantly expressed with different human PCas expressing different FGFR1 isoforms (Abstract #3913 AACR 2015). These results suggest that different FGFR1 isoforms in PCa cells may partially underlie the biological heterogeneity of PCa. The studies presented here focus in two of the best-characterized isoforms: FGFR1alpha (R1alpha), with 3 Ig-like domains, and 822 aa in length; and FGFR1beta (R1beta), with only 2 Ig-like domains and 733 aa in length. We assessed whether these isoforms induce activation of the same pathways using PC3 cells transiently transfected with empty vector (EV), R1alpha (NM_023110.2) or R1beta (NM_023105.2) and treated with vehicle, FGF2 or FGF9. By Western blot analysis we found that total FGFR1 expression (relative to a loading control) was similar in cells transfected with R1beta or R1alpha. Levels of p-FGFR1 were high in untreated cells transfected with R1alpha, but no further induction was observed after treatment with FGF2 or FGF9. However, p-FGFR1 expression was almost undetectable in untreated cells expressing R1beta and was slightly induced by FGF2 but not by FGF9. p-PLCγ expression was found only in cells expressing R1alpha. We subsequently stably transfected these isoforms in PC3 cells and discovered that while no significant difference in R1alpha and R1beta transcript levels was detected, the levels of R1alpha protein were higher than those of R1beta suggesting that these isoforms may undergo different translational regulation, We also performed in vivo studies by subcutaneous injection of R1alpha or R1beta expressing PC3 cells in immunocompromised mice and weekly monitored tumor volume. We found that PC3 cells expressing R1alpha developed significantly larger tumors than PC3 cells expressing R1beta. We are now in the process of analyzing at the molecular level these tissue specimens. In conclusion, R1alpha and R1beta isoforms trigger different biological effects in PCa cells. Because different isoforms are expressed in different prostate tumors, the expression of these isoforms could be associated with the typical PCa heterogeneity and could explain differences in therapy responses to FGFR1 blockade. These results warrant further studies to fully understand the biological implications of FGFR1 isoforms in the pathogenesis of PCa. Citation Format: Estefania Labanca, Xinhai Wan, Jun Yang, Matthew Iyer, Christopher Logothetis, Arul Chinnaiyan, Nora Navone. Alpha and beta isoforms of fibroblast growth factor receptor 1 in prostate cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1871.

Abstract 3913: Fibroblast growth factor receptor 1 isoforms in prostate cancer bone metastases

Bone metastases dominate the clinical picture of men with advanced prostate cancer (PCa). The fibroblast growth factor (FGF)/FGF receptor (FGFR) complex is commonly altered during PCa progression. Four highly conserved genes (FGFR1, FGFR2, FGFR3, and FGFR4) encode a repertoire of alternatively spliced variants of FGFRs that vary in the extracellular ligand-binding and intracellular kinase domains. A previous study from our group implicated FGFR1 as a therapy target for PCa bone metastases (Sci Transl Med 2014; 6:252ra122). One of the most important mechanisms by which FGFRs determine specificity for different FGFs is by alternative exon usage of the immunoglobulin-like (Ig-like) motif of the extracellular domain. We analyzed FGFR1 transcripts in 183 human PCa samples and in PCa patient-derived xenografts (PDXs) assessed by RNA sequencing. We identified eight different protein coding transcript to be the most abundantly expressed, namely ENST00000326324; ENST00000356207; ENST00000397103 (with a predicted protein length of 731 to 733 aa) and ENST00000397091; ENST00000397108; ENST00000397113; ENST00000425967; ENST00000532791 (with a predicted protein length of 820 to 853aa). Probably reflecting FGFR1alpha/beta isoforms: FGFR1alpha, containing three Ig-like domains and FGFR1beta, containing only two Ig-like domains. Interestingly, different PCa tissue samples expressed different isoforms. We subsequently assessed, by real-time reverse transcription polymerase chain reaction, the expression of FGFR1alpha and beta in three PCa cell lines (PC3, DU145 and C4-2B) and seven PCa PDXs (MDA PCa 2b, MDA PCa 118b, MDA PCa 155-12; MDA PCa 146-10; MDA PCa 146-12; MDA PCa 150-3 and MDA PCa 183) derived from primary PCa, bone metastases and brain metastases and reflecting the typical adenocarcinoma as well as, adenocarcinomas with neuroendrocrine differentiation and small cell carcinomas of PCa. We found that all PDXs express primarily FGFR1alpha isoform while PCa cell lines express FGFR1beta. We stably transfected PC3 cells with FGFR1alpha (NM_023110.2) and FGFR1beta (NM_023105.2) isoforms. After clones were established, we placed the cells for 10 days in culture and found that tissue culture plates containing PC3 expressing FGFR1alpha had significantly more cells compared with dishes containing PC3 expressing FGF1beta isoform as assessed by direct cell counting in a phase contrast microscope. Furthermore, PC3 cells transfected with FGFR1 alpha display a more adhesive phenotype than cells transfected with FGFR1beta or empty vector as assessed by cell attachment in a 24-well plate. We conclude that FGFR1 isoforms are involved in the pathogenesis of PCa and can be used to develop markers of response to FGFR1 blockade. These results warrant further studies to fully understand the biological implications of FGFR1 isoforms in the pathogenesis of PCa. Citation Format: Estefania Labanca, Xinhai Wan, Jun Yang, Matthew Iyer, Christopher Logothetis, Arul Chinnaiyan, Nora Navone. Fibroblast growth factor receptor 1 isoforms in prostate cancer bone metastases. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3913. doi:10.1158/1538-7445.AM2015-3913

Abstract 3697: Molecular link that associates high fat diet and prostate tumor growth.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Prostate Cancer (PCa) is one of the most common invasive tumors in men. Epidemiological studies indicate that diet and overweight are important factors implicated in prostate carcinogenesis. Obesity is associated with PCa aggressiveness, poorer prognosis and increased mortality. Breast cancer susceptibility gene 1 (BRCA1) interacts with several transcriptional regulators to modulate the androgen receptor (AR) signaling in PCa cell lines. Germline mutations in this gene increase breast cancer risk and are associated with high grade PCa. Previously, it had been reported that C-terminal Binding Protein 1 (CtBP1) acts as a switch to control BRCA1 transcription in response to the metabolic status of the cells. The release of CtBP1 from BRCA1 promoter through estrogen induction and high NAD+/NADH ratio (similar to high caloric intake) increases BRCA1 transcription in breast cancer cells. The aim of this work was to assess the effect of androgens and/or high fat diet over the BRCA1/CtBP1 axis and PCa tumor growth. We found that BRCA1 and CtBP1 proteins associate to BRCA1 proximal promoter region in PC3 cells and suppress BRCA1 transcription. Testosterone stimulation released these factors from BRCA1 promoter increasing its transcription. To assess whether this activation is mediated by testosterone or the estrogen, synthesized from testosterone by the aromatase (CYP19A1), we investigated this mechanism in the presence of letrozol (LTZ), an aromatase inhibitor. We found that LTZ abolished BRCA1 induction by testosterone, suggesting that BRCA1 activation is mediated by estrogen in these cells. Furthermore, we generated PC3 cell lines transfected with pcDNA3-CtBP1 (PC3-CtBP1) or shRNA-CtBP1 (PC3-shCtBP1) plasmids, to overexpress or knock down CtBP1 expression, respectively. CtBP1 induction decreased BRCA1 expression in these cells and this effect was reverted by CtBP1 depletion. In addition, PC3-CtBP1 cells showed increased clonogenic capacity and proliferation compared to PC3-shCtBP1 cells. Moreover, we developed an in vivo model to investigate the effect of high caloric diet on PCa growth after CtBP1 modulated-expression. High fat or control diet fed male nude mice were inoculated with PC3-CtBP1 and PC3-shCtBP1 stable cells. We found that CtBP1 depleted cells growing as xenografts in high fat diet fed mice dramatically decreased prostate tumor growth. Molecular analysis of tumors by RT-qPCR showed that CtBP1 depletion correlated with high BRCA1 expression. In addition, serum from high fat fed mice significantly induced PC3-CtBP1 cell proliferation in vitro. These results strongly suggest that the potential oncogenic role of CtBP1 is dependent on the caloric diet intake. Hence, BRCA1 regulation by CtBP1 provides an important molecular link between caloric intake and tumor suppressor expression. Citation Format: Cristian P. Moiola, Paola De Luca, Florencia Zalazar, Javier Cotignola, Estefania Labanca, Roberto Meiss, Elba S. Vazquez, Kevin Gardner, Adriana De Siervi. Molecular link that associates high fat diet and prostate tumor growth. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3697. doi:10.1158/1538-7445.AM2013-3697