UBQLN1通过稳定USP7蛋白表达促进乳腺癌辐射抵抗的机制研究

Radioresistance is a major challenge during the treatment of the breast cancer. A further understanding of the mechanisms of radioresistance could provide strategies to address this challenge. We have demonstrated that UBQLN1 could increase radioresistance of breast cancer cells by regulating radiation-induced autophagy. The expression level of UBQLN1 in breast cancer is higher than that in the adjacent normal tissues. Our preliminary data have been proved that UBQLN1 could bind to USP7 protein and decrease its degradation, which further prolong the half-life of CHK1 protein, a key factor involved in the radiation induced damage repair. Based on these data, we first present that UBQLN1 could promote radioresistance not only through modulating radiation-induced autophagy, but also through regulating the process of radiation-induced DNA damage repair. To test the hypothesis, firstly, we constructed subline of breast cancer cells and test the role of UBQLN1 in radioresistance of breast cancer both in vitro and in vivo. Next we will demonstrate the molecular mechanism of UBQLN1 in radiation-induced damage repair using immunoprecipitation and mass spectrometry. Furthermore, the effect of UBQLN1 and its related proteins will be analyzed by clinical samples in breast cancer. Our study will provide new insight into the mechanism of UBQLN1 in radioresistance of breast cancer and provide new theoretical and experimental basis for the treatment of breast cancer.

乳腺癌对辐射的生物学抵抗可严重降低患者的治愈率，我们的前期研究证实，UBQLN1可通过调节辐射诱导的自噬反应参与调节乳腺癌的辐射抵抗，且UBQLN1在乳腺癌组织中的表达水平高于邻近正常组织。本项目预实验发现，UBQLN1可与USP7蛋白结合从而降低USP7的降解，并进而延长CHK1蛋白的半衰期，而CHK1是参与调节辐射损伤修复的关键因子。据此我们首次提出：UBQLN1可通过调节辐射损伤修复过程，从而导致乳腺癌细胞的辐射抵抗。本项目拟构建乳腺癌辐射抵抗细胞株，通过体内外实验证实UBQLN1在乳腺癌辐射抵抗中的生物学功能；其次利用免疫共沉淀、质谱等技术探讨UBQLN1参与调节乳腺癌细胞辐射损伤修复的分子机制；最后通过临床大样本检测UBQLN1及其相关蛋白在乳腺癌预后判断中的作用。本课题完成有望揭示UBQLN1在乳腺癌辐射抵抗中的作用机制，为乳腺癌的治疗提供新的理论及实验依据。

乳腺癌对辐射的生物学抵抗可严重降低患者的治愈率，是导致肿瘤残留及复发的根本原因。本研究中，通过构建乳腺癌辐射抵抗细胞株，我们发现，辐射抵抗的细胞亚株中UBQLN1的mRNA表达水平与亲代细胞相比无明显变化，而蛋白表达水平显著增高；在辐射抵抗的细胞亚株中敲除UBQLN1的表达后，细胞的辐射敏感性增强，而在亲代细胞中过表达UBQLN1后，细胞的辐射敏感性减弱。深入研究发现，敲除UBQLN1的表达后，细胞辐射后的凋亡水平增高，DNA损伤相关蛋白γ-H2AX表达增高，而过表达UBQLN1后，辐射后的γ-H2AX表达水平降低；动物实验发现敲除UBQLN1的表达后，裸鼠皮下移植瘤的生长速度显著降低；进一步的研究发现，UBQLN1可与USP7蛋白结合，敲除UBQLN1的表达后，USP7的降解速度加快，提示UBQLN1可稳定USP7蛋白的表达；与亲代细胞相比，辐射抵抗细胞亚株中P-ATM表达水平偏高，敲除ATM的表达后，细胞辐射后UBQLN1的表达水平较空转组显著降低，提示UBQLN1的表达水平可能受ATM的调控。本研究的完成揭示了UBQLN1在乳腺癌辐射抵抗中的作用及相关分子机制，为探寻乳腺癌治疗的新靶点提供充分的理论依据和实验基础。