Alejandra Paez

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.

Abstract B18: Metabolic signature characterization in prostate cancer mediated by Heme-oxygenase 1

Prostate cancer (PCa) is the second leading cause of cancer-associated death in men, with bone metastases being the main cause of mortality. 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 found 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) under HO-1 modulation by Gene Ontology revealed alterations in several metabolic pathways such as steroid, tyrosine and lipid metabolism, and ion transport. Bone is the only site of PCa progression, and bone cells are able to produce factors that increase the growth and survival of tumor cells favoring progression. However, the molecular nature of this interaction remains to be elucidated. Our preliminary results performed on cocultures of PC3 cells (treated or not with hemin) with Raw264.7 (pre-osteoclastic) or MC3T3 (preosteoblastic) cells demonstrate that HO-1 is able to direct the metabolic fate of bone precursor cells due to the deregulation of glycolytic genes. HO-1 induction in PC3 cells downregulated the expression of PKM2 and LDHA 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, Nicolas Anselmino, Alejandra Paez, Florencia Cascardo, Javier Cotignola, Geraldine Gueron, Elba Vazquez. Metabolic signature characterization in prostate cancer mediated by Heme-oxygenase 1 [abstract]. In: Proceedings of the AACR International Conference held in cooperation with the Latin American Cooperative Oncology Group (LACOG) on Translational Cancer Medicine; May 4-6, 2017; Sao Paulo, Brazil. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(1_Suppl):Abstract nr B18.

Game-changing restraint of Ros-damaged phenylalanine, upon tumor metastasis article

An abrupt increase in metastatic growth as a consequence of the removal of primary tumors suggests that the concomitant resistance (CR) phenomenon might occur in human cancer. CR occurs in murine tumors and ROS-damaged phenylalanine, meta-tyrosine (m-Tyr), was proposed as the serum anti-tumor factor primarily responsible for CR. Herein, we demonstrate for the first time that CR happens in different experimental human solid tumors (prostate, lung anaplastic, and nasopharyngeal carcinoma). Moreover, m-Tyr was detected in the serum of mice bearing prostate cancer (PCa) xenografts. Primary tumor growth was inhibited in animals injected with m-Tyr. Further, the CR phenomenon was reversed when secondary implants were injected into mice with phenylalanine (Phe), a protective amino acid highly present in primary tumors. PCa cells exposed to m-Tyr in vitro showed reduced cell viability, downregulated NFκB/STAT3/Notch axis, and induced autophagy; effects reversed by Phe. Strikingly, m-Tyr administration also impaired both, spontaneous metastasis derived from murine mammary carcinomas (4T1, C7HI, and LMM3) and PCa experimental metastases. Altogether, our findings propose m-Tyr delivery as a novel approach to boost the therapeutic efficacy of the current treatment for metastasis preventing the escape from tumor dormancy.

Abstract A064: Mass spectrometry-based proteomics study makes apolipoprotein E a potential risk factor for prostate cancer

Proteomics represents an important tool for the identification of new molecular targets for prostate cancer (PCa) tailored therapy. Innovative high-throughput proteomic platforms are now identifying and quantifying new specific and sensitive biomarkers for PCa detection, stratification, and treatment. Formalin-fixed and paraffin-embedded (FF-PE) sections mounted on microscope slides are hard to achieve given the low peptide yield obtained from the slides. Here we performed an innovative protocol for an in-depth quantitative mass spectrometry-based proteomics analysis of FF-PE PCa and benign prostate hyperplasia (BPH) sections, using phase-transfer surfactant-aided extraction/tryptic digestion of FF-PE proteins. Results yielded a list of 50 differential proteins only expressed in PCa samples. Of note, apolipoprotein E (APOE) was highly present in carcinoma samples. Furthermore, to evaluate the clinical significance of APOE in PCa we performed a bioinformatics analysis using the Oncomine database. We identified 16 publicly available gene expression microarray datasets comparing prostate adenocarcinoma versus normal prostate, which met our eligibility criteria. We carried out meta-analysis combining the data from the independent datasets. APOE was ranked by its P-value for every analysis scoring a gene rank and then we obtained a median rank (median P-value rank across datasets). APOE showed a significant upregulation (fold change >1.5, P Citation Format: Juan Bizzotto, Sofia Lage Vickers, Alejandra Paez, Carlos Scorticati, Javier Cotignola, Pia Valacco, Osvaldo Mazza, Elba Vazquez, Geraldine Gueron. Mass spectrometry-based proteomics study makes apolipoprotein E a potential risk factor for 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 A064.

Abstract B080: Heme-oxygenase 1 negatively regulates interferon inducible antiviral (mx1) in prostate cancer

Prostate cancer (PCa) is a complex and progressive disease. Under the selective pressure of medical and drug treatment, PCa cells are able to acquire molecular changes that allow them to survive in androgen-deprived conditions and finally cause their host’s death. Inflammation fosters multiple hallmarks of cancer. However, the molecular mechanisms that prime the pathogenesis of cancer-related inflammation are yet to be deciphered. In this context, heme-oxygenase 1 (HO-1), the rate-limiting enzyme in heme degradation, emerges as a potential target in PCa, maintaining homeostasis and counteracting oxidative and inflammatory damage. We have previously documented HO-1 nuclear expression in human primary prostate carcinomas. In PCa cell lines we confirmed that HO-1 overexpression inhibits cell proliferation, migration, and invasion. It also impairs tumor growth in vivo and downregulates the expression of target genes associated with inflammation. Considering the crosstalk between inflammation and cancer progression, our next step sought to identify signaling pathways by which HO-1 could be operating. Towards this end we performed and analyzed RNAseq data on PCa cells overexpressing HO-1 pharmacologically or genetically. Of note, HO-1 significantly upregulated the human myxovirus resistant protein A (Mx1). The clear association between Mx1 expression and cancer remains unknown. In vitro studies revealed that forced expression of HO-1 in PCa cells significantly upregulated MX1 mRNA and protein levels and shifted its localization towards the perinuclear area. To address the relevance of MX1 in PCa we searched the public cancer microarray database, Oncomine. MX1 was ranked by its P-value for every analysis scoring a gene rank. We then obtained a median rank (median P-value rank across datasets) for MX1. The expression profile for MX1 showed a significant downregulation (fold change 1.5, P We extended the bioinformatics analysis, using cBioportal, assessing whole-exome and RNAseq data. The most frequent genetic alteration found for MX1 was deletion. RNASeq data also confirmed a significant downregulation for MX1 (P Overall, HO-1 potentially operates through Mx1, whose expression inversely correlates with PCa, depicting its critical role in prostate carcinogenesis. Citation Format: Emiliano Ortiz, Alejandra Paez, Nicolas Anselmino, Javier Cotignola, Pia Valacco, Elba Vazquez, Geraldine Gueron. Heme-oxygenase 1 negatively regulates interferon inducible antiviral (mx1) 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 B080.

Abstract A058: Integrative prostate cancer tissue proteomics dissects clear and distinct proteomes for human prostate cancer and benign prostatic hyperplasia

Current approaches in proteomics techniques and MS systems have revived the quest for novel biomarkers in prostate cancer (PCa) boosting the molecular characterization of the disease. To reveal fundamental differences between benign and malignant growth of prostate cells, we combined a new protein extraction procedure that disrupts the crosslinked proteins from the previously formaldehyde-fixed, paraffin-embedded tissue samples with in-depth proteomic analysis (ESI-MS/MS). Human PCa and benign prostatic hyperplasia (BPH) tissue samples were obtained using phase-transfer surfactant-aided extraction/tryptic digestion of formalin-fixed and paraffin-embedded sections mounted on microscope slides. Data analysis was based on label-free spectral counting, identifying with a minimum of two peptides, 1331 and 1239 proteins in PCa and BPH tissue proteomes, respectively. 71 proteins were exclusively present in PCa samples, while 122 proteins where exclusively present in BPH samples. In order to prioritize candidate markers for PCa, we compared protein expression based on normalized spectral counts between tissue samples. We set as cut-offs proteins that were found with a minimum of three peptides within the PCa and BPH proteomes. This filter resulted in the selection of two clusters of 11 and 16 proteins, respectively. The data sets highlighted distinct proteins that were previously studied in the context of prostate cancer progression, including SSBP1, GDF15, NDRG1, C4A, and APOE for PCa and DUSP3, MME, SRI, and DSG1 for BPH, thus providing further confirmation for the robustness of our quantification method. We next subjected our candidate list to bioinformatics analysis (Oncomine). Accordingly, the 5 proteins mentioned for PCa were significantly upregulated (fold change >1.5, P≤0.05) in prostate adenocarcinoma vs. normal prostate gland. Whole-exome analysis (cBioportal) revealed amplification as the most frequent genetic alteration and RNASeq data also confirmed a significant upregulation for these proteins (P≤0.05). Strikingly, proteins associated with BPH were significantly downregulated (fold change >1.5, P≤0.05) across the same comparison and RNA-seq data also confirmed a significant downregulation for these proteins (P≤0.05). This report showcases significant and extensive differences in protein expression patterns between BPH and prostate carcinoma. Proteome analysis of prostate tissues should help to disclose the molecular mechanisms underlying prostate malignant growth, resulting in new sets of biomarkers for diagnostic, prognostic, and therapeutic use. Citation Format: Sofia Lage Vickers, Juan Antonio Bizzotto, Alejandra Paez, Javier Cotignola, Carlos Scorticati, Osvaldo Mazza, Pia Valacco, Geraldine Gueron, Elba Vazquez. Integrative prostate cancer tissue proteomics dissects clear and distinct proteomes for human prostate cancer and benign prostatic hyperplasia [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 A058.

Heme oxygenase 1 governs the cytoskeleton at filopodia: pulling the brakes on the migratory capacity of prostate tumoral cells

This paper refers to Paez et al. Prostate cancer (PCa) is the second leading cause of cancer death in men in the United States. Incidence increases with patient age and represents the most important risk factor. Localized PCa can be cured in most cases, but when the disease escapes the confines of the gland, the prospects for cure decrease drastically. Androgen ablation is the most effective way of halting PCa progression, but given sufficient time, growth of the cancer resumes in most cases and the disease becomes castration resistant (castration-resistant PCa (CRPC)). No therapy is curative for patients with CRPC, thus emerging a critical need to identify new therapy targets. Advanced PCa has been associated to the loss of cell adhesion molecules at adherens junctions. The delicate equilibrium between the cell pushing and pulling forces drive leading edge dynamics and cell migration. Interdigitating filopodia are vital for the proper alignment and establishment of the initial cell–cell adhesions, known as adhesion zippering, an event that contributes significantly to reduce the metastatic phenotype of tumor cells. Heme oxygenase 1 (HO-1) is as a stress response protein and a critical mediator of cellular homeostasis. HO-1 is also implicated in the modulation of cellular adhesion in PCa, upregulating E-cadherin and β-catenin expression, and relocating them to the cell membrane, favoring a more epithelial phenotype. However, it is yet unclear which are the HO-1 interactors and how they cooperate in the regulation of the cytoskeleton organization. Paez et al. undertook an in-depth mass spectrometry-based proteomics study to build the HO-1 interactome in PCa. Fifty-six HO-1 differentially associated proteins were identified including a subset of proteins responsible for the regulation of the cytoskeleton dynamics with potential clinical relevance in PCa, such as Heat shock 27 kDa protein (HSPB1), Gelsolin (GSN), LIM and SH3 Protein 1 (LASP1) protein, Muskelin (MKLN1) and Tropomodulin 3 (TMOD3). It was also demonstrated that HO-1 modulation impacts directly in the morphology of PCa cells, modulating the actin stress fibers, cell protrusions, cell contacts and cell migration, reflecting a less invasive and less motile phenotype (Figure 1). Further, through a multi ‘omics’ approach, new aspects regarding the mechanistic strategy that HO-1 uses to alter protrusive forces and adhesive behavior of tumor cells were identified. Authors integrated RNA-seq data of PCa cells overexpressing HO-1 both genetically and pharmacologically, together with the HO-1 interactome unveiling significant alterations of four molecular pathways related to cell adhesion and cell–cell communication: ANXA2/HMGA1/POU3F1; NFRSF13/GSN; TMOD3/ RAI14/VWF; PLAT/PLAU. Of note, HO-1 downmodulates the uPA/ uPAR directly impacting on Rho GTPases through the alpha V-Beta 3 integrin receptor, which in turn affects filopodia formation. HO-1 also binds Gelsolin, STAT3 and HSPB1, potentially supporting its implication in filopodia regulation and gives ground to HO-1 involvement at the molecular level in the modulation of the cytoskeleton pathways. Overall, this work breaks down two paradigms: first, filopodia structures increase the potentiality of tumor cells to adhere to each other rather than to increase the migratory and invasive potential of cells, demonstrating that the augmented number of filopodia per cell is not associated with a more motile phenotype; second, HO-1 actively participates in the regulation of actin dynamics at cellular protrusions rather than to be confined to its microsomal function (heme degradation). Further, new aspects of the mechanistic strategy by which HO-1 alters protrusive forces and the adhesive behavior of tumor cells are revealed, showcasing its relevance as a key homeostatic factor against PCa.

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 5199: A second round for concomitant resistance in human cancer: A restraint upon metastasis

Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA Concomitant tumor resistance (CR) is the phenomenon according to which a tumor-bearing host inhibits the growth of secondary tumor implants. Ehrlich first described it in 1906, but this phenomenon remained forgotten for about 60 years. After its renascence, some groups have demonstrated that both immunogenic and non-immunogenic tumors can induce CR in different animal models. Metastases could be considered as secondary tumor implants developed spontaneously during the primary tumor growth, thus CR could be relevant for cancer progression. Clinical and experimental evidence suggest that the removal of human and murine tumors might be followed by an abrupt increase in metastatic growth, hence the primary tumor could exert a controlling action on its metastases. In previous papers we demonstrated that, in mice, two temporally separate peaks of CR can be detected during murine T-lymphoma (LB) primary tumor growth. The second peak of CR is mediated by most large-sized immunogenic and non-immunogenic tumors and is associated with the anti-tumor and anti-metastatic serum factor meta-tyrosine (m-tyr), an isomer of tyrosine not present in normal proteins. Based on this background, in this work we assessed whether CR was also occurring in human tumor experimental models. Athymic nude mice were inoculated s.c. in the right flank, with the human prostate cancer cell line PC3 (1 × 106, primary implant). After 14 days the animals received a second inoculation of PC3 cells in the left flank (1 × 106, secondary implant). The control group only received the secondary implant. The growth of the secondary implant was significantly reduced (92%; P<0.05) at 27 days, in animals carrying the primary implant. Moreover, m-tyr was detected in the serum of mice bearing the RC phenomenon. The tumor growth inhibition was recapitulated in animals inoculated with the primary tumors and injected with m-tyr. Strikingly the RC phenomenon was reversed when secondary implants were injected with phenylalanine, a protective amino acid highly present in primary tumors. In vitro results also showed that exposure of PC3 cells to m-tyr inhibited cell growth and a G0/G1 cell cycle arrest, which was concomitant with alterations in the mRNA expression levels of survivin (apoptosis inhibitor), Ki67 (proliferation marker), Hes1 (transcription factor involved in Notch pathway) and STAT3 (prostate cancer survival factor) (P<0.01). We have further validated the RC phenomenon in two other human cancer models: anaplastic carcinoma of the lung (CALU-6), and nasopharyngeal carcinoma (KB), exhibiting also high levels of m-tyr in serum from nu/nu mice bearing CALU-6 or KB tumors. Altogether, we showcase for the first time that CR is triggered in human solid tumors, that this phenomenon is mediated by m-tyr and provide the molecular mechanisms that drive this process. These results offer an alternative therapeutic avenue in the management of metastatic cancers. Citation Format: Geraldine Gueron, Nicolas Anselmino, Damian Manchuca, Emiliano G. Ortiz, Maria Noelia Carabelos, Federico Schuster, Paula Chiarella, Alejandra Paez, Felipe M. Jaworski, Javier Cotignola, Roberto Meiss, Raul Ruggiero, Elba S. Vazquez. A second round for concomitant resistance in human cancer: A restraint upon metastasis. [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 5199. doi:10.1158/1538-7445.AM2015-5199

Abstract LB-43: Unveiling the molecular significance of HO-1 and muskelin interaction: two masterminds behind the morphology and the adhesive behavior of prostate cancer cells

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Prostate Cancer (PCa) is the second leading cause of cancer death in American men. The inflammatory tumor microenvironment is a fertile niche that releases reactive oxygen species, which accelerates the malignant transformation and appears as a fine tuner of the adhesive behavior of cells. Heme oxygenase 1 (HO-1), the rate-limiting enzyme in heme degradation, represents an essential event in cellular responses to pro-oxidative and pro-inflammatory insults. As we previously reported that HO-1 over-expression impaired tumor growth and angiogenesis in vivo we sought to assess whether HO-1 could regulate the adhesive properties and the morphology of PCa cells. A bioinformatics enrichment analysis using Metacore, GeneMANIA and DAVID was performed; rendering a significant association of the HO-1 regulated genes with several proteins located in the extracellular space and cell membrane; compartments highly correlated with the adhesive behavior of cells. In an effort to understand the molecular mechanisms underlying HO-1s role in cell morphology regulation we used a proteomics approach to identify HO-1 partners. We performed GST-pull-down assays using lysates from PC3 cells transfected with either GST-tagged HO-1 or the empty vector, and the isolated proteins were subjected to MALDI-TOF/TOF analyses. Our results showed that HO-1 interacts with Muskelin, a nucleocytoplasmic mediator of cellular morphology and adhesiveness. Up-regulation of Muskelin under HO-1 induction in PCa cells was confirmed by confocal microscopy. A high degree of nuclear overlay between HO-1 and Muskelin signals was observed when cells were exposed to hemin, a potent specific inducer of HO-1 or genetically manipulated to over-express HO-1, compared to controls. Interestingly after HO-1 induction, both protein exhibit similar sub-cellular dynamics, relocating from the cell membrane, towards the cell nuclei. Altogether, we have shown for the first time that HO-1 binds and up-regulates Muskelin, a specific factor involved in shaping cellular morphology and adhesive properties, favoring a less aggressive phenotype and further supporting the anti-tumoral function of HO-1in PCa. Citation Format: Geraldine Gueron, Jimena Giudice, Alejandra Paez, Pia Valacco, Noelia Carabelos, Federico Schuster, Javier Cotignola, Felipe Jaworski, Daiana Leonardi, Maria Binaghi, Marcelo Marti, Nora Navone, Elba Vazquez. Unveiling the molecular significance of HO-1 and muskelin interaction: two masterminds behind the morphology and the adhesive behavior of prostate cancer cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-43. doi:10.1158/1538-7445.AM2014-LB-43