跨损伤合成特异性聚合酶Polκ在脑胶质瘤发生发展中的作用及机制研究

Translesion DNA synthesis (TLS) is a DNA damage tolerance process mediated by specialized low-fidelity DNA polymerases to replicate damaged genomic DNA. Recently, accumulating evidence has shown that deregulation of TLS polymerases play significant roles in cancer development and progression. In our previous study, we demonstrated that Polκ, an important component of TLS, was overexpressed in gliomas and was found to be highly correlated with pathological stage and poor prognosis in glioma patients. However,the underlying molecular mechanisms remain to be elucidated. Here, we hypothesized that Polκ might function to promote glioma development and progression. To examine whether Polκ executed these functions, we overexpressed or knockdowned Polκ in normal human astrocytes and a series of glioma cells, established in vitro and in vivo glioma models, and investigated the effects of Polκ expression on cell cycle, cell proliferation, genomic stability. Collectively, this project might pave the way for novel, promising roles of Polκ as oncogenic factor and provide a potential therapeutic strategy for glioma patients.

跨损伤DNA 合成（translesion DNA synthesis，TLS）是细胞通过特异性低保真聚合酶修复DNA 损伤的一种自我保护机制，近些年研究表明此通路可能在肿瘤发生、发展中起到重要作用。申请人在国际上首次发现TLS聚合酶Polκ在脑胶质瘤中异常高表达，且证实该聚合酶与胶质瘤恶性程度和患者临床预后密切相关，但其深入机制还有待进一步探讨。为此，我们提出以下设想：Polκ可能通过影响细胞周期、增殖、基因组稳定性等功能促进胶质瘤发生、发展。为验证这一假说，我们在正常星形胶质细胞和多种胶质瘤细胞株中过表达或沉默Polκ，通过建立体内、外模型，从分子、细胞、组织以及动物整体水平等多方面探讨Polκ在胶质瘤发生、发展中的作用，本研究为胶质瘤的发生发展机制提供新的理论依据。

跨损伤DNA 合成（translesion DNA synthesis，TLS）属于一种复制后修复过程，通过启用特异性的DNA聚合酶在损伤处进行延伸来实现修复。我们前期报道TLS聚合酶Polκ在胶质瘤中异常表达，与胶质瘤病人预后密切相关，但Polκ在脑胶质瘤的生物学作用仍不清楚。本项目通过对脑胶质瘤细胞株、原代细胞及NOD-SCID小鼠颅内移植模型的体内外实验研究，阐明TLS聚合酶Polκ在胶质瘤中的生物学作用。我们的研究发现，Polκ在经替莫唑胺(TMZ)处理后的胶质瘤细胞株和原代胶质瘤细胞中显著升高。应用体外及颅内肿瘤原位模型实验证实，阻断Polκ表达可有效地逆转胶质瘤细胞对TMZ的耐药。进一步的机制研究发现Polκ执行此功能并不依赖于MGMT、MMR等已知的TMZ耐药诱导机制，而是通过影响ATR-Rad17-Chk1信号通路，阻滞细胞周期，抑制同源重组修复来发挥作用。通过进一步的临床样本验证，发现Polκ低表达的胶质瘤患者接受TMZ治疗后预后良好。综上所述，我们的研究揭示了Polκ在胶质瘤TMZ耐药中的重要作用，为胶质瘤靶向治疗提供了理论基础和新的思路。