KIT抗体-DM1偶联靶向治疗伊马替尼耐药胃肠间质瘤的研究

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal neoplasm in the gastrointestinal tract and is characterized by expression of the receptor tyrosine kinase KIT (CD117). In more than 90% of GIST cases, oncogenic mutations in KIT are present, leading to constitutive activation of the receptor, which drives the proliferation of these tumors. Treatment of GIST with imatinib, a small-molecule tyrosine kinase inhibitor, inhibits KIT-mediated signaling and initially results in disease control in 70-85% of patients with KIT-positive GIST. However, the vast majority of patients eventually develop resistance to imatinib treatment, leading to disease progression and posing a significant challenge in the clinical management of these tumors.Antibody-drug conjugates (ADC) combines the unique targeting capabilities of monoclonal antibodies with the cancer-killing ability of cytotoxic drugs, and is the new direction of targeted therapy for tumor.In previous study, we identified an anti-KIT monoclonal antibody (mAb) (4D2), which is able to slow the growth of three human GIST cell lines in vitro and internalized into the KIT positive GIST cells. In this project, we plan to construct a new targeted bioconjugates by coupling of KIT antibody and microtubule inhibitor DM4 with potent anti-tumor activity, so as to achieve the targeted killing of tumor cells. What`s more, cell experiment and animal experiment will be performed to assess the anticancer activity and its anti-tumor mechanism. This helps to make better foundation for the development of targeted therapy for imatinib-resistant GIST.

胃肠间质瘤（GIST）是胃肠道最常见的间叶源性肿瘤，其发病机制关键在于酪氨酸激酶受体KIT高表达及异常活化，传统放化疗基本无效，手术治疗复发率高。90%以上的GIST 高表达KIT，分子靶向药物伊马替尼是目前治疗GIST的首选药物，疗效优异。然而，随着治疗时间的延长，几乎所有患者都将产生耐药而致疾病进展。因此，亟需不断研发新的靶向药物。抗体-化学药物偶联物充分发挥了抗体的靶向性与化学药物的高效性，对复发和耐药肿瘤仍有较好的治疗效果，是肿瘤靶向药物的最新发展方向。前期研究中，我们筛选到1株高亲合力抗KIT胞外段抗体（KD≈0.17 nM），能特异靶向KIT阳性肿瘤细胞并快速内化入细胞内。在此基础上，本项目拟将KIT抗体和强效的微管抑制剂DM4通过Linker定向偶联，构建一种新型的靶向药物，利用抗体介导的内化将DM4靶向运送至GIST细胞内而杀伤之，为耐药GIST新型靶向药物的研发提供依据。

胃肠间质瘤（GIST）的发病与KIT/PDGFRA的异常活化相关。伊马替尼（imatinib）作为一种选择性KIT/PDGFRA酪氨酸激酶受体抑制剂，其对初治的GIST疗效显著，然而随着治疗时间的延长，最终大部分患者会发生继发性耐药而导致疾病进展，继发性耐药成为了临床的一大难点。.抗体-化学药物偶联物可以充分发挥抗体的靶向性和化疗药物的有效性，对复发和耐药肿瘤具有很好的治疗效果。KIT高表达于90%以上的GIST，其胞外段可作为GIST免疫治疗的靶点。因此，本课题组将KIT抗体与强效的微管抑制剂DM4通过linker定向偶联，构建了一种新型的靶向药物。利用抗体介导的内化将DM4靶向运送至GIST细胞内，从而发挥抗肿瘤作用。KIT抗体-DM4偶联物可有效克服伊马替尼耐药，对耐药GIST具有显著的杀伤作用，而且无明显毒副作用。项目的实施有望为GIST耐药患者提供新的治疗思路。.我们还建立了华西医院胃肠间质瘤数据库，对患者的基因突变类型进行了系统分析，发现GIST患者中最常见的基因突变类型为c-KIT，其次为PDGFRA，野生型。c-KIT突变中，外显子11以缺失突变、缺失+插入突变为主，提示GIST基因突变率高且突变类型多样，患者需要精确的个体化治疗。.GIST从良性到恶性生物学行为的分子机制尚不明确。我们利用高通量细胞芯片分别对不同恶性潜能组GIST蛋白表达差异进行分析，筛选出了一系列在高低恶性潜能GIST中差异性表达的蛋白。进一步实验发现，SPACRL1蛋白在GIST恶性化过程中发挥着重要的作用，SPARCL1下调表达可促进GIST细胞迁移和侵袭能力，有望成为GIST预后判断的另一可靠指标。