Key Laboratory for Experimental Teratology of the Ministry of Education and Department of Medical Genetics, School of Basic Medical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, Shandong, 250012, China; Institute of Medical Sciences, The Second Hospital of Shandong University, Cheeloo College of Medicine, Shandong University, Jinan, Shandong, 250033, China.
Department of Urology, Qilu Hospital of Shandong University, Cheeloo College of Medicine, Shandong University, Jinan, Shandong, 250012, China; Department of Urology, Zibo 148 Hospital, Zibo, Shandong, 255300, China.
Cancer Lett. 2024 Oct 1;601:217148. doi: 10.1016/j.canlet.2024.217148. Epub 2024 Aug 3.
Studying the mechanisms underlying clear cell renal cell carcinoma (ccRCC), the most common subtype of kidney cancer, may address an unmet need in ccRCC-targeted drug research. Growing evidences indicate that protein phosphatase 4 (PP4) plays an important role in cancer biology. Here, we characterized the upregulation of PP4 core component SMEK1 in ccRCC using tissue microarrays and revealed that its high expression is closely associated with reduced patient survival. We then conducted cell function experiments and animal experiments to prove the tumor-promoting effect of SMEK1. Next, RNA-seq was performed to explore its underlying mechanism, and the results revealed that SMEK1-regulated genes were extensively involved in cell motility, and the canonical tyrosine kinase receptor EGFR was one of its targets. Moreover, we verified the regulatory effect of SMEK1 on EGFR and its downstream MAPK and AKT pathway through molecular experiments, in which erlotinib, a tyrosine kinase inhibitor, can partially block this regulation, demonstrating that SMEK1 mediates its effects dependent on the tyrosine kinase activity of EGFR. Mechanistically, SMEK1 bond to PRMT5 and facilitated PRMT5-mediated histone methylation to promote the transcription of EGFR. Furthermore, we studied the upstream regulators of SMEK1 and demonstrated that the transcription factor E2F1 could directly bind to the SMEK1 promoter by chromatin immunoprecipitation. Functionally, E2F1 could also induce ccRCC progression by manipulating the expression of SMEK1. Collectively, our findings demonstrate the overexpression of SMEK1 in ccRCC, and reveal a novel E2F1/SMEK1/PRMT5/EGFR-tyrosine-kinase-dependent pathway for ccRCC progression.
研究透明细胞肾细胞癌（ccRCC）的发病机制，即最常见的肾癌亚型，可能会满足 ccRCC 靶向药物研究的未满足需求。越来越多的证据表明，蛋白磷酸酶 4（PP4）在癌症生物学中发挥着重要作用。在这里，我们使用组织微阵列对 ccRCC 中 PP4 核心成分 SMEK1 的上调进行了特征描述，并揭示其高表达与患者生存时间缩短密切相关。然后，我们进行了细胞功能实验和动物实验，以证明 SMEK1 的促肿瘤作用。接下来，进行了 RNA-seq 以探索其潜在机制，结果表明 SMEK1 调节的基因广泛参与细胞运动，而经典的酪氨酸激酶受体 EGFR 是其靶标之一。此外，我们通过分子实验验证了 SMEK1 对 EGFR 及其下游 MAPK 和 AKT 通路的调节作用，其中酪氨酸激酶抑制剂厄洛替尼可以部分阻断这种调节，表明 SMEK1 通过 EGFR 的酪氨酸激酶活性介导其作用。从机制上讲，SMEK1 与 PRMT5 结合并促进 PRMT5 介导的组蛋白甲基化，从而促进 EGFR 的转录。此外，我们研究了 SMEK1 的上游调节因子，并通过染色质免疫沉淀实验证明转录因子 E2F1 可以直接结合 SMEK1 启动子。在功能上，E2F1 还可以通过操纵 SMEK1 的表达来诱导 ccRCC 的进展。总之，我们的研究结果表明 SMEK1 在 ccRCC 中过表达，并揭示了一种新的 E2F1/SMEK1/PRMT5/EGFR-酪氨酸激酶依赖的 ccRCC 进展途径。
