RAD50基因胚系突变导致乳腺癌不良预后的分子机制探索

RAD50 gene, as part of a sensor of DNA double strand break (DSB), plays a key role in relocalizing the damage foci and activating the downstream signal pathways. RAD50 germline mutations could lead to genomic instability and breast cancer susceptibility. However, the prognosis of breast cancer with RAD50 pathogenic mutation is unknown. We previously screened RAD50 germline mutations in 7657 consecutive unselected breast cancer patients without BRCA1/2 mutations using next-generation sequencing. Combined with the clinicopathological data, multivariate analysis revealed that RAD50 pathogenic mutations were an independent unfavorable predictor for recurrence-free survival [adjusted hazard ratio (HR) 2.66; 95% CI, 1.18–5.98; P=0.018] and disease-specific survival (adjusted HR 4.36; 95% CI, 1.58–12.03; P=0.004). We further intend to evaluate the influence of RAD50 pathogenic mutations on the DSB pathway, cellular biological behavior and drug sensitivity of the PARP inhibitor in vivo and in vitro to clarify the molecular mechanism underlying the association between RAD50 germline mutation and poor prognosis in breast cancer, so as to provide a new target and theoretical basis for the improvement of breast cancer prognosis.

RAD50基因是DNA双链断裂通路早期的重要基因，起到识别损伤位点、激活下游信号通路的关键作用。其胚系突变可以导致基因组不稳定和乳腺癌易感。但是，携带RAD50致病突变的乳腺癌的临床预后未知。本项目在前期工作中采用二代基因测序技术完成了7657例中国非BRCA1/2突变的连续随机乳腺癌患者RAD50基因全编码序列的检测，共检测到26例乳腺癌患者携带有13种RAD50的致病性突变。我们结合临床病理资料进行生存分析，多因素分析显示RAD50突变携带者的无复发生存期和疾病相关生存期显著差于非携带者，提示RAD50致病突变是乳腺癌预后不良的独立因素。进一步我们拟通过体内外试验检测RAD50致病胚系突变对DNA双链断裂通路的影响、突变细胞系的侵袭转移能力以及对靶向药物PARP抑制剂敏感性的情况，阐明RAD50致病胚系突变导致乳腺癌不良预后的分子机制，为改善乳腺癌预后提供新的靶点和理论依据。

乳腺癌是全球及我国女性最常见的恶性肿瘤。同源重组通路相关基因的胚系突变可以增加乳腺癌易感性，但是与乳腺癌临床预后的关系未知。而RAD50是同源重组通路中重要的关键基因之一。我们前期采用二代基因测序技术检测了7657中国非BRCA1/2突变的乳腺癌患者RAD50基因全编码序列，发现RAD50的致病性胚系突变率为0.38%。生存分析显示，经过多因素校正后RAD50突变携带者的无复发生存和疾病相关生存显著差于非携带者（p<0.05）。本研究在中国乳腺癌大样本连续病例中证实RAD50基因的致病胚系突变是乳腺癌不良预后的独立因素，但是体外试验未能验证RAD50功能下调会影响乳腺癌细胞系的增殖以及对铂类药物的敏感性，需要更多的证据解释RAD50在乳腺癌发生发展中的分子机制。