KLRC2基因胚系突变介导乳腺癌抗HER2靶向治疗原发耐药分子机制研究

In clinical the response rate of initial therapy only 60% in the patients with HER2-positive breast cancer who receiving the targeted therapy,then,the other 40% patients have the intrinsic(primary) resistance.How to identify these patients and reveal the molecular mechanisms of primary resistance is a key issue in targeted therapy of breast cancer. It is reported the germline mutations can directly modulate the responses of cancers to targeted therapies,so it is worth exploring the role of germline mutations in the targeted therapy primary resistance. Our prior study found that germline KLRC2 gene mutations rate in peripheral blood from the patients who have primary resistance is significantly higher then the rate from the patients who are sensitive to the targeted therapy(P=0.0047).KLRC2(NKG2C) is one member of the transmembrane protein family in natural killer cell.In this study we plan to explore the molecular mechanisms of KLRC2 gene mutation which inducing the primary resistance of targeted therapy.We expect to clarify if the KLRC2 mutation lead to the impairment of the killing effect from nature killer cells(NK) to the breast cancer cells which in trastuzumab therapy,consequently the therapy resistance occur.We also verify the prediction function of the KLRC2 gene mutation for the primary resistance of clinical patients who have the trastuzumab therapy.We expect to develop the biomarker in peripheral blood which can be used to predict the primary resistance and can direct the clinical treatment adjustment to overcome the resistance, consequently, can advance the accuracy of the targeted therapy in breast cancer.

在临床中HER2阳性乳腺癌患者接受靶向药物治疗初始有效率仅为60%， 40%患者呈现原发耐药，如何识别这部分患者并揭示原发耐药分子机制是乳腺癌靶向治疗领域的关键问题之一。文献报道胚系突变能够直接调节肿瘤对靶向治疗的反应，因此其在靶向治疗原发耐药中的作用值得探索。在前期研究中，我们发现原发耐药患者外周血胚系KLRC2基因突变率显著高于敏感患者（P=0.0047）。KLRC2(NKG2C)属于自然杀伤(NK)细胞跨膜蛋白家族，在本课题中拟进行KLRC2突变介导靶向治疗原发耐药的分子机制研究，阐明KLRC2突变是否导致NK细胞对曲妥珠单抗治疗的乳腺癌杀伤功能减弱，从而产生原发耐药，并验证KLRC2基因突变对临床患者曲妥珠单抗治疗原发耐药的预测作用，以期开发预测原发耐药的外周血生物标记物，指导临床进行治疗干预克服耐药，推进乳腺癌靶向治疗的精准程度。

课题执行过程中预试验构建KLRC2突变体外和体内模型结果不理想，对研究内容进行调整：在临床多线靶向治疗耐药的HER2阳性晚期乳腺癌患者中进行免疫检查点抑制剂治疗，同时进行疗效相关标记物探索研究。对于靶向治疗敏感、靶向治疗耐药的HER2阳性转移性乳腺癌患者，进行肿瘤组织基因测序和外周血ctDNA基因测序，寻找相关生物标记物。结果显示多线抗HER2靶向治疗耐药的患者应用帕博利珠单抗(pembrolizumab)治疗后肿瘤明显退缩，临床疗效评价为部分缓解(PR)，同时外周血HER2胞外段（HER2 ECD）检测结果表明HER2 ECD表达水平也显著降低，较基线水平降低60% -75%。应用免疫组化方法检测患者肿瘤组织PD-L1和PD-1表达均＜1%。本研究证实对于多线靶向治疗耐药的晚期乳腺癌患者，应用肿瘤免疫治疗仍有一定的疗效，为临床治疗提供更多依据。

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