Effect of DNA repeat silencing on efficacy of ATRi in prostate cancer treatment

项目总结 抑制DNA复制检查点调节因子ATR是一种新的、有前途的癌症治疗方法。ATR 抑制物(ATRI)通过在有问题的部位引起双链断裂(DSB)而起到癌症治疗的作用 DNA复制。事实上，我们最近已经证明，形成结构的重复DNA序列 强烈影响ATRI驱动的破裂。然而，我们最近的初步研究表明，异常DNA 构造形成并不是这些地点脆弱性的唯一决定因素。我们现在已经证明了ATRI- 反向逆转录重复序列的驱动断裂强烈地被促进其 抄写。此外，由于逆转录元件的转录在大多数基因组位置都是沉默的，它们的 减压大大增加了ATRI造成的破碎度。 我们假设，促进转录的癌症相关改变和沉默抑制物 逆转录元件将增加对ATRI治疗的敏感性。重要的是，晚期前列腺癌，大多数 值得注意的是，耐去势前列腺癌(CRPC)表现出许多特征，预计会导致 反向逆转录元件的转录。这些改变包括逆转录元素的低甲基化，丢失 RNaseH2引起的RNA1和P53介导的重复沉默和RNA-DNA杂交体的异常处理 缺乏症。在这里，我们建议确定这些前列腺癌相关变化中的每一个如何影响 ATRI诱导的DNA断裂的定位和数量。此外，我们还将探讨其分子机制。 通过这种反向逆转录元件转录增加ATRI驱动的特定位点的断裂，并确定 临床批准药物进一步抑制逆转录元件沉默与ATRI协同抑制 CRPC小鼠模型中肿瘤的生长情况。最后，我们将确定这种联合治疗是否比 在前列腺癌相关ATM、BRCA2和RB1突变的背景下有效。总而言之，这些 研究将表征癌细胞对ATRI增敏的新机制，并确定新的 慢性前列腺癌的联合治疗。

PROJECT SUMMARY Inhibition of the DNA replication checkpoint regulator ATR is a new and promising cancer treatment. ATR inhibitors (ATRi) function as cancer treatments by causing double-stranded breaks (DSBs) at sites of problematic DNA replication. Indeed, we have recently demonstrated that structure-forming repetitive DNA sequences strongly influence on ATRi-driven breakage. However, our recent preliminary studies indicate that abnormal DNA structure formation is not the sole determinant of vulnerability at these sites. We have now shown that ATRi- driven breakage at inverted retroelement repeats is strongly stimulated by treatments that promote their transcription. Moreover, because the transcription of retroelements is silenced at most genomic locations, their derepression substantially increases breakage caused by ATRi. We hypothesize that cancer-associated alterations and silencing inhibitors that foster the transcription of inverted retroelements will increase sensitivity to ATRi treatment. Importantly, advanced prostate cancer, most notably castration-resistant prostate cancer (CRPC), exhibits many features expected to cause increased transcription of inverted retroelements. These alterations include the hypomethylation of retroelements, the loss of RB1 and p53-mediated repeat silencing, and the abnormal processing of RNA-DNA hybrids due to RNASEH2 deficiency. Herein, we propose to determine how each of these prostate cancer-associated changes affect the localization and number of DNA breaks induced by ATRi. Furthermore, we will explore the molecular mechanism by which inverted retroelement transcription increases ATRi-driven breakage at select sites and determine if further inhibition of retroelement silencing by clinically approved drugs synergizes with ATRi to suppress the growth of tumors in mouse models of CRPC. Finally, we will determine if this combination treatment is more effective in the context of prostate cancer-associated mutation of ATM, BRCA2 and RB1. Collectively, these studies will characterize new mechanisms by which cancer cells are sensitized to ATRi as well as identify novel combination treatments for CRPC.