阻断HIF-1通路在HIF-2抑制剂抵抗型肾癌中的治疗作用及机制研究

Renal cell carcinoma is the most common malignant tumor of kidney in adults. About 50% of the patients develop metastasis before or after nephrectomy. Today the main targets of treatment for aggressive renal cell carcinoma is vascular endothelial growth factor (VEGF) and platelte-derived growth factor(PDGF ),which are the downstream genes of HIF pathway. Another target is the mammalian target of Rapamycin(mTOR) , which is the upstream of HIF, while the pivotal factor HIF itself has been regarded undruggable. Our previous research has proved that HIF is an effective target for treating RCC.The specific HIF-2 antagonist had a greater activity than Sunitinib which is a oral receptor tyrosine kinase inhibitor(data published in 《Nature》). About 56% RCC was sensitive to the HIF-2 inhibitor therapy, but still there is a considerable proportion of patients showed only slight reaction or even totally resistant to HIF-2 inhibitor.Subsequent research found that those tumors showed resistance demonstrated low expression levels of HIF-2α while HIF-1α were relatively high. This project will focused on the HIF-2 inhibitor resistant kidney cancer, especially with VHLMut-HIF-1αHigh-HIF-2αLow/-phenotype.We will treat these tumors by blocking HIF-1 pathway in vitro with primary cultured RCC cells and and in vivo with RCC xenografts on NOD/SCID mice and evaluate the effectiveness and the mechanism of this therapy. The result of the project will reveal the function of HIF-1 pathway in driving the growth of HIF-2 inhibitor resistant RCC, support the theoretical foundation for design a specific inhibitor of HIF-1α which is very essential to the precision therapy for RCC.

肾细胞癌是成人肾脏最常见的恶性肿瘤，约50%的患者在首诊时或术后发生转移。目前临床的靶向治疗药物主要针对HIF通路的下游基因VEGF、PDGF和其上游的mTOR，而转录因子HIF一直被认为无法作为药物治疗的靶标。申请人的前期研究已证实HIF可以作为治疗的有效靶点，抑制 HIF-2α比舒尼替尼更有效地抑制小鼠肾癌移植瘤的生长（研究结果已发表在《Nature》）。但肾癌对该治疗的敏感率约56%，部分肿瘤不甚敏感甚至抵抗，而这部分肿瘤显示了低水平HIF-2α和高水平的HIF-1α。本研究继续探讨对HIF-2α抑制剂治疗抵抗的肾癌，选择VHLMut-HIF-1αHigh-HIF-2αLow/-的肿瘤，通过体内外实验阻断HIF-1通路，观察对肾癌体内外生长的影响，对于揭示HIF-1α在调控HIF-2α抑制剂抵抗型肾癌生长中的作用，为后续设计特异性的HIF-1α抑制剂，实现肾癌的精准治疗提供实验依据。

肾细胞癌是成人肾脏最常见的恶性肿瘤，对常规放化疗不敏感，手术为主要治疗方式。目前临床的靶向治疗药物主要针对HIF通路的上、下游基因，而转录因子HIF一直被认为无法作为药物治疗的靶标。我们前期研究已证实HIF可以作为治疗的有效靶点，直接抑制 HIF-2α比舒尼替尼更有效地抑制小鼠肾癌移植瘤的生长，但肾癌对该治疗的敏感率约56%，部分肿瘤不甚敏感甚至抵抗，而这部分肿瘤显示了低水平HIF-2α和高水平的HIF-1α，本研究从临床样本、细胞及动物水平对HIF-2α抑制剂治疗抵抗的肾癌进行分子机制及生物学研究，结果可见：肾细胞癌存在 HIF-1α 与 HIF-2α 不同的表达模式，HIF-1α 在较低级别的肾癌内表达略高，与 FBP-1表达呈负相关；在建立 HIF-2 抑制剂抵抗的肾癌细胞后，可见HIF-1α 转录和蛋白表达量均有不同程度升高，单细胞测序分析显示肿瘤细胞耐药前、后转录组表达模式发生质的改变，细胞亚群几乎无重叠，且部分差异基因与 HIF-1α通路相关，提示HIF-1α参与肾癌细胞获得性耐药的过程。抑制耐药细胞HIF-1α或过表达FBP-1后，细胞的增殖活性、侵袭能力均减低，凋亡率升高，且直接抑制 HIF-1α效果更好；动物体内研究可见HIF-2α耐药肿瘤生长速度大于耐药前肿瘤，且抑制 HIF-1α能使耐药肿瘤生长延缓。本研究揭示了HIF-1α在调控HIF-2α抑制剂抵抗型肾癌生长中的作用，抑制HIF-1α或使用 FBP-1结构类似物阻断 HIF-1α通路，可有效抑制耐药肿瘤的生长，以达到精准靶向治疗，并为日后设计特异性的HIF-1α小分子抑制剂提供研究基础。