肾透明细胞癌BAP1突变/缺失下调SETD7导致CpG岛高甲基化表型的分子机制研究

Clear cell renal cell carcinoma is the most common histology with poor prognosis in renal cancers. Clear cell renal cell carcinoma with BRCA1 associated protein 1 (BAP1, a deubiquitinating enzyme) gene mutation/deletion has the most aggressive feature. Moreover, current therapeutic strategies are not good enough in treating advanced BAP1 mutant/deleterious patients. Hence, identifying biological characteristics and discovering new therapeutic targets of BAP1 mutant/deleterious renal carcinoma patients are in urgent need..In our previous studies, we found that the proportion of BAP1 germline/somatic mutation/deletion was higher in Chinese kidney cancer patients, and more than 60% BAP1 mutant/deleterious patients had CpG island methylator phenotype (CIMP). Our previous experiments showed that silencing BAP1 could up-regulate the DNA methylation level and DNMT1 protein level, and down-regulate SETD7 (a negative regulator of DNMT1 protein) protein level, in renal carcinoma cells. However, silencing BAP1 could not alter transcription level of DNMT1 and SETD7. In addition, we found that BAP1 could interact with SETD7. Therefore, we hypothesized that “BAP1mutation/deletion→deubiquitination inactivation→SETD7 degradation→stabilizing DNMT1→CIMP” could be the mechanism of BAP1 mutation/deletion leading to CIMP. .In the future, this project will focus on confirming the hypothesis above, elucidating the specific mechanism of BAP1 mutation/deletion leading to CIMP and exploring the therapeutic value of methylation inhibitors in BAP1 mutant clear cell renal cell carcinoma. This study will help explain the new mechanism of BAP1 mutation in renal cell carcinoma and will propose new therapeutic modalities.

肾透明细胞癌是最常见且预后最差的肾癌亚型。BAP1基因（编码一种去泛素化酶）突变的透明细胞癌恶性程度最高，且现行治疗方案效果不佳。.申请人在前期研究中发现：中国肾癌患者中BAP1基因胚系/体系突变/缺失的比例较高，60%的BAP1突变患者具有CpG岛高甲基化表型（CIMP）。前期实验显示沉默BAP1可上调肾癌细胞DNA甲基化水平和DNMT1蛋白水平、下调DNMT1负性调节因子SETD7的蛋白水平（均不影响转录）。另外，我们发现BAP1可与SETD7相互作用。因此，我们提出“BAP1突变/缺失→去泛素化受损→SETD7降解→稳定DNMT1→CIMP”可能是BAP1突变/缺失致CIMP的机制。.本项目后续聚焦于验证上述假说，阐明BAP1突变/缺失致CIMP的具体机制，探索甲基化抑制剂对BAP1突变型肾癌的治疗价值。本研究有助于明确BAP1突变肾癌进展的新机制并提出新的治疗模式。

肾透明细胞癌是最常见且预后最差的肾癌亚型。BAP1基因（编码一种去泛素化酶）突变的透明细胞癌恶性程度最高，且现行治疗方案效果不佳。前期研究结果提示：BAP1突变/缺失的肾透明细胞癌往往呈现CpG岛高甲基化表型（CIMP）。..项目负责人依托此研究项目围绕BAP1突变/缺失驱动CIMP表型的具体机制进行了一系列研究。我们在临床样本和体内外实验中证实BAP1突变/缺失可驱动肾透明细胞癌产生CIMP表型，且促进DNMT1甲基转移酶的关键负性调节分子SETD7的降解。我们的研究结果提示SETD7可能是BAP突变型肾癌产生CIMP表型的关键中间分子，而DNA甲基化抑制剂可能在治疗BAP1突变/缺失型肾癌中存在潜在优势。在此项目中，我们也在体外试验明确长效甲基化抑制剂SGI-110联合靶向药舒尼替尼对比舒尼替尼单药，能更好地杀伤BAP1突变/缺失型肾癌细胞。该项目明确了BAP1突变/缺失致CIMP的具体机制，探索甲基化抑制剂对BAP1突变型肾癌的治疗价值，有助于明确BAP1突变肾癌进展的新机制并提出新的治疗模式。..此外，在完成既定研究计划的基础上，负责人在多种泌尿系统肿瘤中围绕与本项目相关的“肿瘤易感基因突变”（包括BAP1）和“表观遗传修饰”（包括甲基化、泛素化）这两个关键领域进行研究，也有重要成果发表，具有良好的转化应用价值。

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