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A heterochromatin gene signature unveils HP1α mediating neuroendocrine prostate cancer development and aggressiveness

ABSTRACT: Neuroendocrine prostate cancer (NEPC) is a lethal subtype of prostate cancer (PCa) with hyperchromatic nuclei being a distinguishing histopathological feature. Here we show that, underlying this distinct nuclear structure, heterochromatin related genes are significantly enriched in NEPC. Among them, heterochromatin protein 1α (HP1α) expression is increased early in NE transdifferentiation and is consistently elevated in clinical NEPC samples. Functional studies showed that HP1α knockdown attenuates NEPC tumor growth by inhibiting proliferation and survival. Its ectopic expression significantly promotes NE transdifferentiation in adenocarcinoma cells subjected to androgen deprivation treatment. To identify mechanisms underlying the function of HP1α involved in NEPC cell proliferation and adenocarcinoma cell NE transdifferentiation, we analyzed gene expression profiles from stable NEPC cell lines with control or HP1α knockdown, and adenocarcinoma cell lines with control or HP1α overexpression, respectively.

ORGANISM(S): Homo sapiens

PROVIDER: GSE105033 | GEO | 2018/01/22

REPOSITORIES: GEO

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Project description:Introduction: Neuroendocrine prostate cancer (NEPC) is an aggressive subtype of prostate cancer, exhibiting rapid progression and is unresponsive to hormone therapy. Reliable prognostic assays and more effective treatments are critically required. However, the research of NEPC has been hampered by a lack of clinically relevant in vivo models. Recently, we successfully developed a first-in-field patient tissue-derived xenograft model of complete neuroendocrine transdifferentiation from prostate adenocarcinoma. By comparing gene expression profiles of the parental adenocarcinoma line (LTL331) and the NEPC subline (LTL331R), we identified DEK, a gene not previously reported in prostate cancer, as a potential biomarker and target for NEPC. Methods: DEK protein expression in patient tissue-derived xenograft models and clinical samples was assessed by immunohistochemistry. The function of DEK was determined by siRNA-induced reduction of DEK expression in PC-3 cells, a cell line with NEPC characteristics, followed by functional assays and gene expression profiling analysis. Results: Elevated DEK protein expression was observed in all clinical NEPC cases, which is distinct from their benign counterparts (0%), hormonal naïve prostate cancer (2.45%) and castration resistant prostate cancer (29.55%). Increased DEK expression is an independent clinical risk factor and is associated with shorter disease free survival in hormonal naïve prostate cancer patients. Reduction of DEK expression in PC-3 cells led to a marked reduction in cell proliferation, cell migration and invasion. Conclusions: The results suggest that DEK may play an important role in the progression of prostate cancer, especially NEPC and provide a potential biomarker to aid risk stratification of prostate cancer and a novel therapeutic target for treating NEPC. The function of DEK was determined by siRNA-induced reduction of DEK expression in PC-3 cells, a cell line with NEPC characteristics, followed by functional assays and gene expression profiling analysis.

Project description:Histone deacetylation is crucial for the regulation of chromatin structure, gene transcription and the epigenetic state of the cell. With the emergence of the neuroendocrine (NE) phenotype in castration-resistant prostate cancer (CRPC), we hypothesized that the inhibition of HDAC1/2 would disrupt the epigenetic events involved in the conversion of prostate adenocarcinoma to a NE prostate cancer (NEPC) phenotype. Additionally, monotherapies tend to have limited efficacy in cancer treatment and combination treatments show more promise. Since the PI3K/AKT/mTOR pathway is a well-established tumor growth-promoting pathway and a promising target in CRPC and NEPC, we investigated the tumor suppressing activities of fimepinostat, a dual HDAC and PI3K inhibitor, on both prostate adenocarcinoma and NEPC. We evaluated multiple cell lines and patient-derived xenograft (PDX) models of prostate adenocarcinoma and NEPC to determine the roles of HDAC1/2 and AKT inhibition, both individually and in combination, in suppressing CRPC and NEPC tumor growth in vitro and in vivo. HDAC1/2 inhibition in combination with PI3K/AKT inhibition was more efficacious than targeting each pathway alone, induced growth inhibitory effects (in some cases synergistic) through cell cycle inhibition and apoptosis across an array of prostate adenocarcinoma and NEPC patient-derived xenografts (PDX) and cell lines in vitro and in vivo. Molecular profiling revealed on-target effects of combined HDAC1/2 and PI3K/AKT inhibition as well as a common downregulation of Myc, E2F, DNA repair, and G2M checkpoint targets, independent of prostate cancer phenotype. Fimepinostat therapy was also associated with the suppression of lineage transcription factor expression including androgen receptor (AR) in prostate adenocarcinoma and Achaete-scute homolog 1 (ASCL1) in NEPC. Our findings demonstrate that dual HDAC1/2 and PI3K/AKT pathway inhibition leads to robust tumor growth inhibition in both adenocarcinoma and NEPC, suggesting that fimepinostat may represent a novel therapeutic for both prostate adenocarcinoma and NEPC phenotypes of CRPC.

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A heterochromatin gene signature unveils HP1α mediating neuroendocrine prostate cancer development and aggressiveness

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