CHEK2缺陷诱导三阴性乳腺癌对PARP1抑制剂耐药及其相关机制

Triple negative breast cancer (TNBC) patients tend to have a quite poor prognosis. In addition, nowadays there have not been found effective targeted drugs for them. TNBCs should be sensitive to Poly(ADP-ribose) polymerase 1 (PARP1) inhibitors, however, several large clinical trials showed that the PARP inhibitors in the advance TNBC didn’t significantly improve the poor prognosis as they were originally expected. Our previous research found that expression of CHEK2 (cell-cycle checkpoint kinase 2) was associated with poor prognosis of TNBC patients. And a missense mutation CHEK2 Y390C (found in Chinese high-risk breast cancer patients by us) was related to drug resistance to PARP1 inhibitor in TNBC cell lines. The reason and molecular mechanism of relationship between CHEK2 expression and efficacy of PARP1 inhibitors in TNBC are unclear. In addition, we found knockdown of CHEK2 was related to increased mRNA and protein levels of GADD45a and decreased levels of DUSP6，TGFBR2 and CASP3 by the Affymetric GeneChip Array. Therefore, we hypothesize that CHEK2 deficiency could regulate GADD45a, DUSP6，TGFBR2 and CASP3, which are the important molecules in the MAPK pathway, thereby resulting in drug resistance of PARP1 inhibitors in TNBC. In this study we will further demonstrate the molecular mechanism of drug resistance of PARP1 inhibitors regulated by CHEK2 deficiency. We will also provide a new insight to the clinical application or PARP1 inhibitors in TNBC patients.

三阴性乳腺癌恶性程度高，临床中缺乏有效的靶向药物改变预后。DNA损伤修复关键酶PARP1抑制剂一度是三阴性乳腺癌最有前景的靶向药物，然而临床研究发现其效果欠佳。我们前期研究发现细胞周期检验点激酶2(CHEK2)磷酸化蛋白不仅与三阴性乳腺预后相关，而且通过体外实验证明CHEK2表达与PARP1抑制剂耐药有关，但具体机制不明。我们利用基因表达芯片发现CHEK2沉默后，MAPK信号转导通路的相关分子GADD45a表达上调，DUSP6，TGFBR2和CASP3表达下调。从而我们推断CHEK2可能通过调节上述基因的表达和相关的信号转导，进而参与PARP1抑制剂耐药。基于该假设，我们选用三阴性乳腺癌细胞做为研究对象，利用分子生物学实验及动物实验等技术，研究PARP1抑制剂应用后，CHEK2如何调控MAPK信号转导通路从而影响耐药，通过上述研究力图阐述三阴性乳腺癌对PARP1抑制剂耐药的可能机制。

DNA损伤修复关键酶PARP1抑制剂是三阴性乳腺癌最有前景的靶向药物之一，基于前期本课题组的研究发现CHEK2表达与PARP1抑制剂耐药可能有关，揭示其耐药机制是本研究的目的。本课题基于CHEK2功能从体外细胞到动物实验中探讨PARP1在三阴性乳腺癌中的耐药机制。.研究发现，在CHEK2-WT细胞中，PARP抑制剂处理后，三阴性乳腺癌细胞的活性显著下降，而CHEK2-KD或CHEK2 Y390C回补的三阴性乳腺癌细胞PARP抑制剂处理后，细胞活性未有显著变化；在体动物模型中进一步证实上述结果。生化实验分析发现相较于野生型，CHEK2敲低或CHEK2 Y390C突变后P38和SMAD2/3通路存在激活现象。.三阴性乳腺癌是临床预后较差的乳腺癌亚型，该研究的结果在分子水平揭示 PARP1 抑制剂耐药的可能机制，对PARP1抑制剂在三阴性乳腺癌中的临床疗效预测有一定的价值。

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