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PCa的主要治疗是雄激素剥夺治疗（ADT）。然而，这种疾病将不可避免地在 不可治愈的形式称为去势抵抗性前列腺癌（CRPC）。重要的是，在低雄激素环境中异常雄激素受体（AR）激活是CRPC的主要驱动因素。CRPC的分子特征为发现新的治疗靶点铺平了道路，我以前的研究表明，TRIM 28在晚期PCa中异常上调。高TRIM 28水平与更差的临床结果相关，这表明TRIM 28可以作为PCa治疗的有希望的靶点。已知TRIM 28与三甲基组蛋白H3赖氨酸9（H3 K9 me 3）特异性甲基转移酶（SETDB 1）的复合物具有转录共阻遏物活性，但其基因组靶点在PCa中仍基本未被探索。此外，TRIM 28下游致癌通路尚未在PCa中进行全面研究。通过分子基因签名分析，发现TRIM 28调控类固醇激素代谢途径。特别是，我发现雄激素消除酶UGT 2B 15和UGT 2B 17是TRIM 28抑制的关键基因。已知TRIM 28复合物的基因组靶向通过结合至特异性DNA识别基序的转录因子来促进。我的数据显示TRIM 28与AR相互作用。此外，我的初步结果表明，在UGT 2B 15和UGT 2B 17基因位点存在TRIM 28、AR和H3 K9 me 3共占据沉积。基于这些发现，我假设TRIM 28与AR一起作用，表观遗传学上沉默了 雄激素代谢酶通过SETDB 1介导的H3 K9 me 3。我建议在AIM 1中测试这个假设。已知UGT 2B 15和UGT 2B 17使用UDP GlucA作为糖供体通过葡萄糖醛酸化抑制雄激素。鉴于UGT 2B 15和UGT 2B 17的过表达与更多的UDP-GlucA消耗相关，我假设在TRIM 28敲减细胞中或在CRPC细胞中使用SETDB 1抑制剂Mit治疗时，UDP-GlucA水平将降低。我建议在AIM 2中测试这个假设。该提案的结果不仅揭示了调节雄激素葡萄糖醛酸化的新表观遗传机制，而且对开发针对CRPC治疗的SETDB 1靶向治疗具有重要意义。

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.