ABSTRACT: The E3 ubiquitin ligase Siah2 contributes to castration-resistant prostate cancer by regulation of androgen receptor transcriptional activity cancer.
Project description:The E3 ubiquitin ligase Siah2 contributes to castration-resistant prostate cancer by regulation of androgen receptor transcriptional activity
Project description:The androgen receptor (AR) plays a central role in the development of castration resistant prostate cancer (CRPC). Here, we demonstrate that the ubiquitin ligase Siah2 targets a select pool of NCOR1-bound, transcriptionally inactive AR for ubiquitination dependent degradation, thereby promoting the expression of ~13% of AR target genes. The Siah2 binding sites located within the AR ligand-binding domain are mutated in PCa, resulting in attenuation of Siah2-mediated regulation. Siah2 is required for growth of PCa cells under androgen-deprivation conditions in vitro and in vivo. Significantly, inhibition of Siah2 promotes PCa regression upon castration and Siah2 expression is markedly increased in human CRPCs. Collectively our findings identify a key role for Siah2 in CRPC through the selective regulation of AR transcriptional activity.
Project description:The androgen receptor (AR) plays a central role in the development of castration resistant prostate cancer (CRPC). Here, we demonstrate that the ubiquitin ligase Siah2 targets a select pool of NCOR1-bound, transcriptionally inactive AR for ubiquitination dependent degradation, thereby promoting the expression of ~13% of AR target genes. The Siah2 binding sites located within the AR ligand-binding domain are mutated in PCa, resulting in attenuation of Siah2-mediated regulation. Siah2 is required for growth of PCa cells under androgen-deprivation conditions in vitro and in vivo. Significantly, inhibition of Siah2 promotes PCa regression upon castration and Siah2 expression is markedly increased in human CRPCs. Collectively our findings identify a key role for Siah2 in CRPC through the selective regulation of AR transcriptional activity. Tumor Harvest. When tumor size reached approximately 1.5 cm in diameter (6-8 weeks after injection), and the serum PSA was greater than 50 ng/ml, animals were surgically castrated under methoxyfluorane anesthesia and monitored for PSA levels for several weeks. Animals were sacrificed by carbon dioxide asphyxiation when tumors were harvested at several points along the PSA curve (pre-castrate (11), regressing (6), nadir (10), recurring (6) and castration resistant (12). Tumor segments were placed in RNALater (Qiagen) and frozen immediately at -80M-BM-0C.weeks. Tumors were harvested at several points along the PSA curve. The epithelial:stromal ratio is consistent within this tumor model and varies 10% between tumors, as assessed by immunohistochemistry of cytokeratin 14 (epithelium) and vimentin (stroma).
Project description:Analysis of gene expression altered upon knockdown of Siah2 in prosate cancer cells. The objective is to elucidate which signaling pathways or transcription factors are regulated by the E3 ubiquitin ligase Siah2 in human prostate cancer cells.
Project description:Analysis of gene expression altered upon knockdown of Siah2 in prosate cancer cells. The objective is to elucidate which signaling pathways or transcription factors are regulated by the E3 ubiquitin ligase Siah2 in human prostate cancer cells. CWR22Rv1 cells were in fected with pLKO.1 control or Siah2 shRNA, and selected with 1ug/ml of puromycin to get stable transfectants. Total RNA was extracted for micorarray analysis to compare the diffentially expressed genes between pLKO.1 control and Siah2 knockdown cells.
Project description:The androgen receptor (AR) plays a critical role in prostate cancer. We identified an ubiquitin E3 ligase RNF6 as one of AR-associated proteins in a proteomic screening. RNF6 induces AR ubiquitination and promotes AR transcriptional activity. Specific knockdown of the endogenous RNF6 alters expression of a subset of AR target genes and diminishes recruitment of AR and its coactivators to androgen responsive elements (AREs) present in the regulatory region of these genes. Furthermore, RNF6 is overexpressed in human hormone-refractory prostate cancer tissues and required for prostate cancer cell growth under androgen-depleted conditions. Our work has provided a novel mechanism by which AR transcriptional activity and specificity is regulated, and identified RNF6 as a potential new target for prostate cancer treatment.
Project description:Neuroendocrine (NE) carcinoma and NE differentiation (NED) of human prostate tumor are hallmarks of aggressive human prostate cancer. Here we reveal that HIF-1a cooperation with FoxA2, a transcription factor expressed in NE tissue, is required for determining NE phenotype. Reduced HIF-1a expression, as seen in the E3 ubiquitin ligase Siah2 mutant mice, converted NE tumors to atypical hyperplasia when crossed with the TRAMPTg mice. Significantly, HIF-1a cooperation with FoxA2 enables the trans-activation of select HRE-regulated genes such as Hes6, Plod2 and Jmjd1a, whose expression is notably higher in metastatic prostate adenocarcinomas. Our findings disclose the requirement for spatial and timely regulation of FoxA2 and HIF-1a for NE/NED in prostate tumors. 12 prostate tumor samples were analyzed during normoxia and hypoxia, with different FOX/HIF genotypes. The pivotal samples are represented as duplicates.
Project description:To investigate the mechanisms of drug resistance and castration resistance in prostate cancer, we performed proteomic sequencing on androgen-dependent prostate cancer cells (LNCaP) and androgen-independent cells (AI) treated with enzalutamide.
Project description:Neuroendocrine (NE) carcinoma and NE differentiation (NED) of human prostate tumor are hallmarks of aggressive human prostate cancer. Here we reveal that HIF-1a cooperation with FoxA2, a transcription factor expressed in NE tissue, is required for determining NE phenotype. Reduced HIF-1a expression, as seen in the E3 ubiquitin ligase Siah2 mutant mice, converted NE tumors to atypical hyperplasia when crossed with the TRAMPTg mice. Significantly, HIF-1a cooperation with FoxA2 enables the trans-activation of select HRE-regulated genes such as Hes6, Plod2 and Jmjd1a, whose expression is notably higher in metastatic prostate adenocarcinomas. Our findings disclose the requirement for spatial and timely regulation of FoxA2 and HIF-1a for NE/NED in prostate tumors.
Project description:FBXW7 is and E3 ubiquitin ligase and is highly mutated in colorectal cancer. We used human colon organoids with engineered FBXW7 hotspot mutations to investigate novel targets of E3 ligase activity with a combined transcriptomic and proteomic approach uncovering the EGFR-MAPK pathway as highly regulated by the E3 ligase activity.
