TRIM28 fuels prostate cancer growth through SETDB1-mediated epigenetic silencing of androgen metabolic genes UGT2B15 and UGT2B17

前列腺癌（PCa）是男性癌症相关死亡的第二大原因。转移性前列腺癌的主要治疗方法是雄激素剥夺疗法（ADT）。然而，这种疾病将不可避免地以一种无法治愈的形式复发，称为去势抵抗性前列腺癌（CRPC）。重要的是，低雄激素环境下异常的雄激素受体（AR）激活是CRPC的主要驱动因素。CRPC的分子表征为发现新的治疗靶点铺平了道路，我之前的研究表明TRIM28在晚期PCa中异常上调。高TRIM28水平与较差的临床结果相关，这表明TRIM28可以作为PCa治疗的有希望的靶点。已知TRIM28与三甲基组蛋白H3赖氨酸9 （H3K9me3）特异性甲基转移酶（SETDB1）复合物具有转录共抑制活性，但其基因组靶点在PCa中仍未被发现。此外，TRIM28下游的致癌途径在PCa中尚未得到全面的研究。通过分子基因特征分析，我发现类固醇激素代谢途径是由TRIM28调控的。特别是，我发现雄激素消除酶UGT2B15和UGT2B17是trim28的关键抑制基因。已知TRIM28复合物的基因组靶向是由结合特定DNA识别基序的转录因子促进的。我的数据显示TRIM28与AR相互作用。此外，我的初步结果表明TRIM28、AR和H3K9me3在UGT2B15和UGT2B17基因位点上共存。基于这些发现，我假设TRIM28与AR一起通过setdb1介导的H3K9me3通过表观遗传沉默雄激素代谢酶的表达。我建议在目标1中验证这一假设。已知UGT2B15和UGT2B17使用UDPGlucA作为糖供体通过葡萄糖醛酸化使雄激素失活。鉴于UGT2B15和UGT2B17的过表达与更多的UDP-GlucA消耗相关，我假设在TRIM28敲低细胞或在CRPC细胞中使用SETDB1抑制剂Mit治疗后，UDP-GlucA水平会降低。我建议在目标2中验证这一假设。本研究结果不仅揭示了雄激素糖醛酸化调控的新表观遗传机制，而且对开发setdb1靶向治疗CRPC具有重要意义。

Prostate cancer (PCa) is the second-leading cause of cancer-related death in men. The mainstay treatment for metastatic PCa is androgen deprivation therapy (ADT). However, the disease will inevitably return in an incurable form termed castration-resistant prostate cancer (CRPC). Importantly, aberrant androgen receptor (AR) activation in the milieu of low androgen is the main driver of CRPC. Molecular characterization of CRPC paves the way for discovery of novel therapeutic targets, and my previous studies showed that TRIM28 is aberrantly upregulated in advanced PCa. High TRIM28 levels are associated with worse clinical outcomes, which suggests that TRIM28 could serve as a promising target for PCa therapy. It is known that TRIM28 in a complex with trimethyl-histone H3 lysine 9 (H3K9me3)-specific methyltransferase (SETDB1) possesses transcriptional co-repressor activity but its genomic targets remain largely unexplored in PCa. Moreover, the TRIM28 downstream oncogenic pathway has not been comprehensively investigated in PCa. By molecular gene signature analysis, I found that the steroid hormone metabolic pathway is regulated by TRIM28. In particular, I found that the androgen eliminating enzymes UGT2B15 and UGT2B17 are the key TRIM28-repressed genes. It is known that genomic targeting of the TRIM28 complex is facilitated by transcription factors that bind to specific DNA recognition motifs. My data revealed that TRIM28 interacts with AR. In addition, my preliminary results indicated there is co-occupancy of TRIM28, AR and H3K9me3 deposition at UGT2B15 and UGT2B17 gene loci. Based on these findings, I hypothesize that TRIM28 acts together with AR to epigenetically silence the expression of androgen metabolic enzymes through SETDB1-mediated H3K9me3. I propose to test this hypothesis in Aim1. UGT2B15 and UGT2B17 are known to inactivate androgen through glucuronidation using UDPGlucA as the sugar-donor. Given that the overexpression of UGT2B15 and UGT2B17 correlate to more UDP-GlucA consumption, I hypothesize that levels of UDP-GlucA will decrease in TRIM28 knockdown cells or with treatment of the SETDB1 inhibitor, Mit, in CRPC cells. I propose to test this hypothesis in Aim2. The results from this proposal will not only reveal a novel epigenetic mechanism for regulating androgen glucuronidation, but also have significant implications for the development of SETDB1-targeted therapy for CRPC treatment.