TIMP1诱导c-Met信号激活促进乳腺癌对CDK4/6抑制剂耐药的机制研究

细胞周期依赖性激酶4/6(CDK4/6)抑制剂近年被证明能有效治疗ER+乳腺癌，但乳腺癌患者最终仍会产生耐药，且耐药机制尚不明确。申请人前期通过激酶芯片与深度测序筛选，发现CDK4/6抑制剂诱导乳腺癌细胞特异性TIMP1（金属蛋白酶组织抑制因子1）蛋白分泌增多，而且药物诱导的耐药细胞中TIMP1基因也持续性高表达。功能缺失实验证明TIMP1表达的确与CDK4/6抑制剂耐药相关。为明确TIMP1介导的促生存机制，与多种RTK靶向药物联合用药发现c-Met抑制剂表现出良好的协同性效应，并验证了c-Met表达增多与TIMP1上调有关。根据TIMP1的生物学功能我们提出以下科学假说：TIMP1降低膜表面蛋白脱落作用从而使c-Met积聚，这种特殊的转录后调控机制导致c-Met信号异常激活从而诱导CDK4/6抑制剂耐药。本项目力求探索乳腺癌对CDK4/6抑制剂耐药的机制，为联合治疗方案提供临床前依据。

Pharmacologic inhibitors of cyclin-dependent kinases 4 and 6 (CDK4/6) have shown promising clinical activities in estrogen receptor (ER)-positive breast cancer. However, patients eventually develop clinical resistance with progression and the mechanism of drug resistance remains to be determined. Previously, through a screening from a phosphokinase array and deep sequencing, we found that the protein level of the tumor inhibitor of metalloproteinase 1 (TIMP1) was upregulated following abemaciclib treatment in ER-positive breast cancer cells. TIMP1 was also overexressed in abemaciclib-resistant cells. Loss-of-function study suggested that the expression of TIMP1 is associated with the resistance of abemaciclib in breast cancer. To further investigate the pro-survive mechanism of TIMP1, we selected six drugs that target key receptor tyrosine kinases (RTKs) to screen for effective combination therapies. Abemaciclib had a synergistic effect with c-Met inhibition with the small molecule SGX-523, whereas other drug combinations were less effective or antagonistic. The overexpression of c-Met is associated with the upregulation of TIMP1. Thus, according to the above-mentioned results, we propose the following hypotheses: TIMP1 reduces the shedding activity of c-Met and leads to the accumulation of c-Met, which leads to the abnormal activition of c-Met signaling and drives the resistance of CDK4/6 inhibitors. This applicant aims to explore the precise mechanism of CDK4/6 inhibitor resistance, and provide a pre-clinical basis for a combination therapy rationale for treating breast cancer.