HIF-2α selective inhibitor showed successful efficacy in sensitive clear cell renal cell carcinoma (ccRCC) presenting higher levels of HIF-2α compared to resistant tumors with low level of HIF-2α (negative HIF-2α ccRCC). Currently, negative HIF-2α ccRCC lacks truly effective therapeutic agents to improve the outcomes. Bromodomain-containing protein 9 (BRD9) plays a critical role in human hepatocellular carcinoma, squamous cell lung cancer, acute myeloid leukemia, and so on. However, expression and biological role of BRD9 in negative HIF-2α ccRCC is poorly understood. Clinically, we demonstrated that expression of BRD9 in negative HIF-2α ccRCC tissues was higher than that in positive HIF-2α ccRCC. Moreover, high BRD9 expression was correlated with unfavorable clinicopathological features and predicted the poor overall survival of negative HIF-2α ccRCC patients. Functionally, BRD9 knockout resulted in reduced proliferation, migration and invasion of negative HIF-2α ccRCC cells (Caki-2). In addition, BRD9 was related to the TIIC infiltration level in negative HIF-2α ccRCC tissues. Mechanistically, Gene set enrichment analysis (GSEA) showed that BRD9 was closely related to Notch signaling pathway. BRD9 knockout resulted in reduced mRNA level of Hes1 and Notch1 in negative HIF-2α ccRCC in vitro. The overexpression of NICD (Notch intracellular domain) enhanced malignant behaviors of Caki-2 cells with BRD9 knockout. And Notch inhibition led to attenuation of cell growth and reduced migration and invasion in Caki-2 cells. Overall, our results identified that BRD9 promotes the proliferation, migration and invasion of negative HIF-2α ccRCC cells by targeting Notch signaling pathway and serve as a promising biomarker for negative HIF-2α ccRCC.

中文翻译：

---

含溴结构域蛋白 9 是一种与免疫浸润相关的预后生物标志物，并通过激活阴性 HIF-2α 透明细胞肾细胞癌中的 Notch 信号通路促进肿瘤恶性发展

与具有低水平 HIF-2α 的耐药肿瘤（阴性 HIF-2α ccRCC）相比，HIF-2α 选择性抑制剂在表现出更高水平 HIF-2α 的敏感透明细胞肾细胞癌 (ccRCC) 中显示出成功的疗效。目前，阴性 HIF-2α ccRCC 缺乏真正有效的治疗药物来改善结果。含溴结构域蛋白 9 (BRD9) 在人肝细胞癌、鳞状细胞肺癌、急性髓性白血病等中起关键作用。然而，对 BRD9 在阴性 HIF-2α ccRCC 中的表达和生物学作用知之甚少。临床上，我们证明 BRD9 在 HIF-2α ccRCC 阴性组织中的表达高于 HIF-2α ccRCC 阳性组织中的表达。而且，BRD9 高表达与不利的临床病理特征相关，并预测 HIF-2α ccRCC 阴性患者的总体生存率较差。在功能上，BRD9 敲除导致阴性 HIF-2α ccRCC 细胞 (Caki-2) 的增殖、迁移和侵袭减少。此外，BRD9 与阴性 HIF-2α ccRCC 组织中的 TIIC 浸润水平有关。机制上，基因集富集分析（GSEA）表明BRD9与Notch信号通路密切相关。BRD9 敲除导致体外负 HIF-2α ccRCC 中 Hes1 和 Notch1 的 mRNA 水平降低。NICD（Notch 胞内结构域）的过表达增强了 BRD9 敲除的 Caki-2 细胞的恶性行为。Notch抑制导致细胞生长减弱，Caki-2细胞迁移和侵袭减少。全面的，