Cbl家族调控c-Met介导的非小细胞肺癌放疗抵抗机制的研究

Radioresistance is a difficult problem in non-small cell lung cancer (NSCLC) treatment. Radio-induced activations of survival signals contribute to the repair of damaged DNA, which is the most common cause of radioresistance. Recently, it is reported that c-Met is associated with radioresistance. Radiation could activate c-Met. Previous studies showed that radiation could also activation several survival signals, such as ERK/MAP kinases, AKT, and NF-κB. It is known that c-Src is the upstream of ERK, AKT and NF-κB. C-Met could activate c-Src. lipid raft clustering plays an essential role in the activation of c-Met.So we speculate that radiation activates c-met. The activation of c-met leads to the activation of ERK, AKT and NF-κB. c-Src was the tie between c-Met and the downstream survival signals. Casitas B-lineage lymphoma-b family proteins, an E3 ubiquitin ligase, could promote the degradation of c-Src and inhibit the clustering of lipid raft. Consequently, we speculate that Cbl family proteins might control the radioresistance through regulating the activity of c-Src and the clustering of lipid raft.The present project aims to illustrate the mechanism of c-Met-mediated radioresistance, and explore the new targets to overcome radioresistance. The results will be of great significance in the development of radiation sensitizer.

放疗抵抗是非小细胞肺癌治疗领域的难题，放射线诱导细胞存活通路的活化进而影响损伤DNA的修复是放疗抵抗的关键。研究显示：肝细胞生长因子受体（c-Met）与放疗抵抗密切相关。放射线可诱导c-Met的活化。放射线尚可诱导ERK、AKT、NF-κB等细胞存活通路活化，c-Src是这些存活通路上游的重要分子，其可被c-Met激活，c-Met活化与脂筏的聚集密切相关。因此我们认为放射线诱导c-Met在脂筏内的聚集及活化，进而激活ERK、AKT、NF-κB，而c-Src是c-Met激活这些信号的"纽带"。泛素连接酶Cbl家族蛋白不但可促进c-Src泛素化降解，而且可抑制脂筏的聚集，因此我们推测Cbl家族蛋白可能通过调节脂筏的聚集及c-Src的表达与活性，调控放射线诱导的c-Met的活化及损伤DNA的修复。本研究旨在明确c-Met介导放疗抵抗的机制，探索逆转放疗抵抗的新靶点，对放疗增敏药物研发具有重大意义

放疗抵抗是导致非小细胞肺癌放疗后局部复发、远处转移及放射治疗失败的重要原因。我们在88例非小细胞肺癌患者中发现，c-Met与c-Src在肿瘤组织中均呈阳性表达，且二者表达呈正相关，与预后相关。同时，我们研究表明：放射线可诱导肿瘤细胞c-Met及c-Src的活化，且c-Src可能位于c-Met信号通路下游，共同参与放射抵抗；应用c-Met抑制剂或c-Src抑制剂能够增加肿瘤细胞对凋亡的敏感性。进一步研究发现：放射线可诱导脂筏的聚集，进而促进c-Met及c-Src在脂筏内聚集及活化；经脂筏抑制剂处理后c-Met及c-Src活化水平明显下降，提示c-Met的活化与脂筏的聚集密切相关。泛素连接酶Cbl家族能够抑制c-Src功能和脂筏聚集，我们通过过表达和敲除c-Cbl及Cbl-b，发现过表达c-Cbl的A549细胞（c-Met高表达），c-Met及c-Src蛋白及磷酸化水平均大大降低，增加了肿瘤细胞对凋亡的敏感性，敲除时则相反；而过表达和敲除Cbl-b则无明显影响。提示c-Cbl可通过调控c-Met增加非小细胞肺癌细胞的放射敏感性。本研究旨在明确 c-Met 介导放疗抵抗的机制，探索逆转放疗抵抗的新靶点，对放疗增敏药物研发具有重大意义。