Cooperativity of TMPRSS2-ERG fusion with p53 inactivation in prostate cancer pathogenesis

项目总结 前列腺癌(PCA)是美国男性癌症死亡的第二大原因。TMPRSS2-ETS 相关基因融合(称为T2-ERG)，与雄激素反应强烈的TMPRSS2基因并列 带有可能的癌基因ERG编码区的启动子出现在大约50%的前列腺癌中 病人。推测过表达的截短T2-ERG在前列腺癌的发病机制中起着关键作用。值得注意的是， 多项研究表明，仅过表达T2-ERG蛋白不足以引发前列腺癌的形成 在小鼠中，除非在非常高龄(24个月)，这意味着T2-ERG需要额外的损害 过度表达诱导的PCa发病机制。1500例前列腺癌患者的NGS数据分析 标本中，我们发现T2-ERG融合和P53失活(由于P53肿瘤抑制功能的丧失 TP53基因缺失和/或突变)在原发和转移性前列腺癌中共同发生，支持这一概念 T2-ERG融合和TP53失活共同推动了前列腺癌的发生和发展。我们演示了 前列腺特异性T2-ERG转基因和Trp53基因敲除(T2-ERG+/P53-)不仅大大增强了ERG 靶基因表达，还可诱导高级别前列腺上皮内瘤变(HGPIN)和癌变 12-15个月龄小鼠的病变。从机制上讲，我们确定LSD1是ERG的直接结合伙伴 蛋白，发现细胞周期蛋白依赖的蛋白-2(CDK2)使LSD1在苏氨酸59(T59-p)处磷酸化。 干扰Lsd1与Hp1γ的相互作用，hp1是H3K9me2/3的表观遗传“阅读器”，并诱导这些DNA去甲基化 ERG靶基因座的转录抑制染色质标记。基于这些新颖的初步数据，我们 假设在精通p53的细胞中，T2-ERG的致癌潜力受转录的限制 通过与Lsd1-hp1γ复合体结合而抑制染色质状态。然而，P53失活会导致 P21WAF1表达缺失或下调，CDKs异常激活，细胞周期进程加快， 进而触发Lsd1T59-p介导的hp1γ与lsd1的解离，hp1γ从染色质中驱逐 由于加速细胞周期进程相关的H3S10磷酸化(H3S10-p)，从而促进 ERG靶基因H3K9me去甲基化、ERG转录组的致癌重编程和PCa 发病机制和进展。为了验证这个假说，我们将确定分子基础和调节 LSD1磷酸化抑制T2-ERG+/P53-Pca细胞中LSD1-HP1ERG相互作用(AIM 1)，定义 LSD1酶活性和T59磷酸化调节ERG的机制和程度 在T2-ERG+/P53-Pca细胞中的转录程序(目标2)，并确定其相互作用的临床意义 T2-ERG+/P53-ERG信号通路与靶向LSD1和ERG通路的抗癌效应 PCA(目标3)。拟议的研究结果将为揭示前列腺癌的分子机制提供新的线索。 并可能导致开发治疗T2-ERG+/P53-Pca的新疗法。

PROJECT SUMMARY Prostate cancer (PCa) is the second leading cause of cancer death in American men. The TMPRSS2-ETS related gene (ERG) fusion (termed T2-ERG), juxtaposing the strong androgen-responsive TMPRSS2 gene promoter with the coding region of the putative oncogene ERG, occurs in approximately 50% of all PCa in patients. It has been inferred that overexpressed truncated T2-ERG is a key player in PCa pathogenesis. Notably, a number of studies show that overexpression of T2-ERG protein alone is insufficient to trigger formation of PCa in mice unless at very advanced age (> 24 months), implying the requirement of additional lesions in T2-ERG overexpression-induced PCa pathogenesis. By analyzing the NGS data from > 1500 cases of PCa patient specimens, we showed that T2-ERG fusion and p53 inactivation (loss of p53 tumor suppressor function due to TP53 gene deletion and/or mutation) co-occurred in both primary and metastatic PCa, supporting the notion that T2-ERG fusion and TP53 inactivation cooperate to drive PCa pathogenesis and progression. We demonstrated that prostate-specific T2-ERG transgene and Trp53 knockout (T2-ERG+/p53-) not only largely enhanced ERG target gene expression, but also induced high-grade prostatic intraepithelial neoplasia (HGPIN) and cancerous lesions in mice at 12-15 months of age. Mechanistically, we identified LSD1 as a direct binding partner of ERG protein and showed that cyclin-dependent kinase-2 (CDK2) phosphorylates LSD1 at threonine 59 (T59-p), which disrupts LSD1 interaction with HP1γ, an epigenetic `reader' of H3K9me2/3 and induces demethylation of these transcription repressive chromatin marks at ERG target gene loci. Based on these novel preliminary data, we hypothesize that in p53-proficient cells the oncogenic potential of T2-ERG is constrained under a transcription repressive chromatin state through association with the LSD1-HP1γ complex. However, p53 inactivation induces loss or downregulated expression of p21WAF1, aberrant activation of CDKs and accelerated cell cycle progression, which in turn triggers LSD1 T59-p-mediated disassociation of HP1γ from LSD1, HP1γ eviction from chromatin due to accelerated cell cycle progression-associated H3S10 phosphorylation (H3S10-p), thereby promoting H3K9me demethylation at ERG target gene loci, oncogenic reprogramming of ERG transcriptome, and PCa pathogenesis and progression. To test this hypothesis, we will determine the molecular basis and regulation of LSD1 phosphorylation-mediated inhibition of LSD1-HP1γ interaction in T2-ERG+/p53- PCa cells (Aim 1), define the mechanism and extent to which LSD1 enzymatic activity and T59 phosphorylation regulates ERG transcriptional program in T2-ERG+/p53- PCa cells (Aim 2), and determine the clinical significance of the interplay between ERG and p53 signaling and anti-cancer efficacy of targeting LSD1 and ERG pathways in T2-ERG+/p53- PCa (Aim 3). Findings from the proposed studies will shed new light on molecular mechanisms of PCa pathogenesis and could lead to development of novel therapeutics for the treatment of T2-ERG+/p53- PCa.