FoxM1调控端粒稳态介导人乳腺癌细胞放射抗拒的机制研究

The radioresistance is the main cause of recurrence of breast cancer after comprehensive therapy, while the telomere homeostasis is a determining factor of radiosensitviity. Therefor, to clarify the molecular mechanism of telomere homeostasis is the key point to reverse the radioresistance. Our previous studies have confirmed that: 1) overexpression of FoxM1 is revealed in radioresistant cell line than radiosensitive one; 2) FoxM1 is a crucial element in regulating cell cycle and DNA repair after damage; 3) the telomeric DNA repair is a principle mechanism for the maintenance of telomere homeostasis. We hypothesize that FoxM1 should regulate the radiosensitivity of breast cancer cells through its effects on telomere homeostasis. In this study, we will further establish the radiosensitive/radioresistant breast cancer cell model, then we will evaluate the levels of telomere binding protein TRF2, proteins involved in DNA repair (Ku80,.MRE11), telomerase activity and the variation of telomeric length following knock-down of FoxM1, thereafter we will assess the relation among the level of FoxM1, the telomere homeostasis and the intrinsic radiosensitivity of breast cancer cells, illustrate the molecular mechanism of FoxM1 regulating the radiosensitivity and confirm it through nude rat model. Our study is for the objective of developing clinical strategies to reverse the radioresistance of breat cancer.

乳腺癌细胞放射诱导抗拒是导致乳腺癌综合治疗后复发的主要原因之一，而端粒稳态是决定肿瘤细胞放射敏感性的重要因素，明确其分子机制是逆转肿瘤细胞放射诱导抗拒的关键。前期研究证实：1）与肿瘤细胞放射敏感株相比，FoxM1在放射抗拒株中高表达；2）FoxM1是参与DNA损伤修复和细胞周期调控的关键因子；3）端粒DNA损伤修复是维持端粒稳态的重要机制。由此推测：FoxM1可能通过调控端粒稳态介导乳腺癌细胞放射抗拒。本课题拟进一步构建乳腺癌细胞放射敏感/抗拒模型，检测抑制FoxM1表达后端粒结合蛋白TRF2、DNA损伤修复蛋白（Ku80、MRE11）、端粒酶活性及端粒长度的变化，分析FoxM1与乳腺癌细胞端粒稳态及内在放射敏感性的相关性，明确FoxM1调控乳腺癌放射敏感性的分子机制，并通过荷瘤裸鼠模型加以验证，为临床上发展逆转乳腺癌放疗抗拒的策略提供理论基础。

FOXM1介导肿瘤细胞周期阻滞和DNA损伤修复等多个信号通路，可能成为肿瘤诊断和预后评估的重要标记物，以及评估肿瘤细胞放射敏感性的重要标志。本研究在明确了FOXM1与肿瘤放射敏感性相关的基础上，进一步研究了二者的相互作用机制，研究发现FOXM1在肿瘤细胞放射敏感/抗拒株模型中存在表达差异，FOXM1在宫颈癌抗拒株中高表达。与癌旁组织相比，组织中的FOXM1表达增高。细胞核表达的FOXM1含量是宫颈癌的独立预后因素。运用慢病毒感染技术，建立了FOXM1低表达的稳定转染株。FOXM1低表达会导致DNA损伤增多，细胞周期阻滞，端粒长度缩短，细胞增殖减缓，端粒稳态失衡，端粒酶活性降低等。本研究将为临床上发展逆转宫颈癌放疗抗拒的策略提供新靶点和理论基础。