Comprehensive analyses of HOXB13-regulated transcriptional programs critical for prostate cancer progression

摘要 前列腺癌(PCA)是美国男性最常见的非皮肤癌。早期PCA 可以通过手术和/或放射治疗有效地消融。然而，转移性前列腺癌仍然是一种 标准的治疗方法是雄激素剥夺疗法(ADT)。然而，大多数PCA 患者对ADT的抵抗力会持续数月至数年，最终导致对去势的抵抗力。 PCa(CRPC)和广泛的侵袭性肿瘤。这种抗性的机制尚不完全清楚， 但已有研究表明，侵袭性的PCa肿瘤会积聚脂滴，以促进转移进展。 因此，克服ADT的关键是确定肿瘤转移的驱动基因，如脂肪生成基因， 这可能是治疗干预和长期治愈的有希望的靶点。在初步研究中，我们 发现含有前列腺特异性同源结构域的转录因子HOXB13在 CRPC与原发PCa的比较，我们发现HOXB13在 脂肪生成的转录抑制。我们发现了一种新的HOXB13相互作用蛋白--组蛋白 脱乙酰酶3(HDAC3)，关闭目标染色质以进行基因抑制。值得注意的是，这种交互是 被HOXB13 G84E突变破坏，该突变已在家族性前列腺癌中被报道并与早发性相关 PCA。此外，我们的数据显示，HDAC3调控的基因与HOXB13调控的基因显著重叠 基因。与HOXB13一样，HDAC3抑制脂肪生成基因，如脂肪酸合成酶(FASN)，这是 伴随着靶基因上关键组蛋白上乙酰化的去除。因此，我们的中心假设是 HOXB13招募HDAC3通过表观遗传重塑抑制成脂基因表达 FASN抑制剂(FASNi)将有效地治疗伴有低水平或G84E突变HOXB13的CRPC。为了测试这些 假设，目标1将检验HOXB13相互作用和招募HDAC3的分子机制 靶向染色质的蛋白质催化组蛋白去乙酰化并抑制成脂基因的表达。我们会 还要研究HOXB13/HDAC3介导的致脂程序与AR之间的相互作用，AR发挥着 在诱导脂代谢方面发挥主要作用，并确定除FASN外的关键下游调节因子。目标2将 检测人类CRPC标本中HOXB13及其关键靶基因的蛋白水平，确定如何 HOXB13及其G84E突变体通过不同的PCA模型调节前列腺癌的发生，并评估 HOXB13低、高剂量移植瘤联合顺铂治疗前列腺癌生长和转移的实验研究 模特们。

Summary Prostate cancer (PCa) is the most commonly diagnosed non-skin cancer in American men. Early-stage PCa can be effectively ablated with surgery and/or radiation treatments. However, metastatic PCa remains a challenge, and the standard treatment is androgen-deprivation therapy (ADT). However, a majority of PCa patients develop resistance to ADT over a period of months to years, ultimately resulting in castration-resistant PCa (CRPC) and widespread aggressive tumors. The mechanisms for this resistance are not fully understood, but it has been shown that aggressive PCa tumors accumulate lipid droplets for fueling metastatic progression. Thus, a key to overcoming ADT is to identify the driver genes of tumor metastasis, such as lipogenesis genes, which may be promising targets for therapeutic intervention and a long-term cure. In preliminary studies, we found that HOXB13, a prostate-specific homeodomain-containing transcription factor, is down-regulated in CRPC as compared to primary PCa, and we found a previously uncharacterized role of HOXB13 in transcriptional repression of lipogenesis. We identify a novel HOXB13-interacting protein, the histone deacetylase 3 (HDAC3), which closes target chromatin for gene repression. Of note, this interaction is disrupted by HOXB13 G84E mutation that has been reported in familial PCa and associated with early-onset PCa. Moreover, our data showed that HDAC3-regulated genes remarkably overlapped with HOXB13-regulated genes. Like HOXB13, HDAC3 inhibits lipogenic genes, such as fatty acid synthase (FASN), and this is accompanied by the removal of acetylation on key histones at target genes. Hence, our central hypothesis is that HOXB13 recruits HDAC3 to repress lipogenic gene expression through epigenetic remodeling and that FASN inhibitors (FASNi) will be effective in treating CRPC with low or G84E-mutant HOXB13. To test these hypotheses, Aim 1 will examine the molecular mechanisms by which HOXB13 interacts and recruits HDAC3 protein to target chromatin to catalyze histone de-acetylation and repress lipogenic gene expression. We will also investigate how this HOXB13/HDAC3-mediated lipogenic program cross talks with AR, which plays a major role in inducing lipid metabolism, and identify key downstream mediators in addition to FASN. Aim 2 will examine the protein levels of HOXB13 and its key target genes in human CRPC specimens, determine how HOXB13 and its G84E mutant regulate prostate tumorigenesis using diverse PCa models, and evaluate the efficacy of FASNi on prostate tumor growth and metastasis using HOXB13-low or -high xenograft and PDX models.