研究透明细胞肾细胞癌 (ccRCC)（肾癌最常见的亚型）的机制可能会解决 ccRCC 靶向药物研究中未满足的需求。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表征了 ccRCC 中 PP4 核心成分 SMEK1 的上调，并揭示其高表达与患者生存率降低密切相关。随后我们进行了细胞功能实验和动物实验来证明SMEK1的促肿瘤作用。接下来，我们进行了RNA-seq来探索其潜在机制，结果表明SMEK1调控的基因广泛参与细胞运动，而经典酪氨酸激酶受体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，证明SMEK1依赖于EGFR的酪氨酸激酶活性来介导其作用。 EGFR。从机制上讲，SMEK1 与 PRMT5 结合，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证明转录因子E2F1可以直接与SMEK1启动子结合。从功能上讲，E2F1 还可以通过操纵 SMEK1 的表达来诱导 ccRCC 进展。总的来说，我们的研究结果证明了 SMEK1 在 ccRCC 中过度表达，并揭示了 ccRCC 进展的一种新的 E2F1/SMEK1/PRMT5/EGFR 酪氨酸激酶依赖性途径。版权所有 © 2024。由 Elsevier B.V. 出版。

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.Copyright © 2024. Published by Elsevier B.V.