PinX1调控XRCC3表达对食管鳞癌细胞放疗敏感性的影响及其分子机制研究

Clinically, definitive chemoradiotherapy (CRT) is a standard treatment for esophageal squamous cell carcinoma (ESCC) in its advanced stages. However, reliable molecular markers that could serve as predictors for ESCC CRT response and/or the patient’s outcome are greatly deficient. The telomere interacting protein PinX1 contributes to telomere maintenance and influences the therapeutic response of cancer cells to DNA damage agents and ionizing radiation (IR), but the underlying mechanism remains unclear. Our previous studies demonstrated that PinX1 knockdown substantially sensitized ESCC cells to radiation and down-regulated the expression of XRCC3 which participates homologous recombination process. Furthermore, the resisitance to IR was significantly recovered by replenishment of XRCC3 expression in PinX1-silenced ESCC cells. Meanwhile, we found that PinX1 protein interacted with hINO80 which serves as a transcription factor of XRCC3. Based on these findings, this project will investigate the roles and mechanisms of PinX1 regulating XRCC3 expression in ESCC cells radiotherapy response by using techniques and methods including molecular cellular biology and experimental zoology. Also, we will study the potential connection between XRCC3-mediated homologous recombination process and PinX1-mediated radiation resistance of ESCC cells. Our study would dissect the underlying mechanism of how PinX1 affects ESCC cells radiotherapy response by regulating XRCC3 expression, enrich our knowledge of the oncology radiobiology and provide new therapeutic strategy for improving the radiotherapy outcome of ESCC patients.

针对性放化疗是局部进展期食管鳞癌病人的标准治疗方式，但目前缺乏预测其治疗反应及病人预后的分子标志物。我们前期研究表明端粒结合蛋白PinX1参与了肿瘤细胞端粒稳定性的调节并影响细胞的放化疗反应，但作用机制尚不十分明确。我们最近的研究发现干扰PinX1的表达介导了食管鳞癌细胞的放疗增敏并导致细胞中同源重组相关基因XRCC3表达的下调，而在稳定干扰PinX1的细胞中恢复XRCC3的表达后，细胞也恢复了对放疗的相对抵抗，此外，我们还发现PinX1和XRCC3的促转录因子hINO80存在蛋白间相互作用。本研究将在此基础上进一步通过分子细胞生物学技术和动物模型等探讨PinX1调控XRCC3表达的分子机理及其在食管鳞癌细胞放疗敏感性调节中的意义。对PinX1和XRCC3在食管鳞癌细胞放疗反应中作用和机制的探讨将丰富我们对肿瘤细胞放射生物学的认识，为食管鳞癌病人的放射治疗提供新靶点、新思路。

多数肿瘤细胞通过激活端粒酶途径维持端粒稳定从而获得永生化。我们前期研究表明PinX1通过维持端粒稳定介导了食管鳞癌对放疗的抵抗,但机制不清.在国家自然科学基金（批号：81401948）的资助下，我们充分阐明了PinX1下游基因XRCC3对食管癌放疗敏感性的影响及机制，并探讨了其临床意义。这部分内容是本项目的基石部分。我们在一系列体内体外研究及临床数据的归纳总结的基础上，首次发现XRCC3可以增加DNA双链损伤的同源重组修复能力及端粒稳定，从而保护电离辐射诱导的细胞损伤，介导了食管鳞癌细胞的放疗抵抗。此外，我们还发现，发现了PinX1新的相互作用蛋白RBM10。RBM10可以定位Cajal小体，端粒酶的Cajal小体定位是其移动到端粒的关键步骤。这些提示PinX1与RBM10相互作用可能通过参与端粒酶运输的调控来影响肿瘤细胞的端粒稳定，从而调节其放疗敏感性。我们的研究结果研究揭示了PinX1/XRCC3及PinX1/RBM10 介导影响食管鳞癌细胞放疗效应抵抗的分子机制并丰富了端粒酶/端粒的调控通路，为食管鳞癌病人的治疗提供新靶点、新思路。