Department of Pathology and Pathophysiology, and Cancer Institute of the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China; Department of Pharmacy, Sanmen People's Hospital of Zhejiang, Sanmen, Zhejiang, China.
Department of Pathology and Pathophysiology, and Cancer Institute of the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China; Key Laboratory of Disease Proteomics of Zhejiang Province, Key Laboratory of Cancer Prevention and Intervention of China National Ministry of Education, School of Medicine, Zhejiang University, Hangzhou, China.
Biochem Pharmacol. 2023 Dec;218:115854. doi: 10.1016/j.bcp.2023.115854. Epub 2023 Oct 19.
Ribonucleotide reductase (RR) is a rate-limiting enzyme that facilitates DNA replication and repair by reducing nucleotide diphosphates (NDPs) to deoxyribonucleotide diphosphates (dNDPs) and is thereby crucial for cell proliferation and cancer development. The E2F family of transcription factors includes key regulators of gene expression involved in cell cycle control. In this study, E2F8 expression was significantly increased in most cancer tissues of lung adenocarcinoma (LUAD) patients and was correlated with the expression of RRM2 through database and clinical samples analysis. The protein expression of E2F8 and RRM2 were positively correlated with tumor-node-metastasis (TNM) pathological stage, and high expression of E2F8 and RRM2 predicted a low 5-year overall survival rate in LUAD patients. Overexpression and knockdown experiments showed that E2F8 was essential for LUAD cell proliferation, DNA synthesis, and cell cycle progression, which were RRM2-dependent. Reporter gene, ChIP-qPCR, and DNA pulldown-Western blot assays indicated that E2F8 activated the transcription of the RRM2 gene by directly binding with the RRM2 promoter in LUAD cells. Previous studies indicated that inhibition of WEE1 kinase can suppress the phosphorylation of CDK1/2 and promote the degradation of RRM2. We further showed here that the combination of E2F8 knockdown with MK-1775, an inhibitor of WEE1 being evaluated in clinical trials, synergistically suppressed proliferation and promoted apoptosis of LUAD cells in vitro and in vivo. Thus, this study reveals a novel role of E2F8 as a proto-oncogenic transcription activator by activating RRM2 expression in LUAD, and targeting both the transcription and degradation mechanisms of RRM2 could produce a synergistic inhibitory effect for LUAD treatment in addition to conventional inhibition of RR enzyme activity.
核苷酸还原酶（RR）是一种限速酶，通过将核苷酸二磷酸（NDPs）还原为脱氧核苷酸二磷酸（dNDPs），促进 DNA 复制和修复，从而对细胞增殖和癌症发展至关重要。E2F 转录因子家族包括参与细胞周期调控的关键基因表达调节剂。在这项研究中，E2F8 在大多数肺腺癌（LUAD）患者的癌症组织中表达显著增加，并通过数据库和临床样本分析与 RRM2 的表达相关。E2F8 和 RRM2 的蛋白表达与肿瘤-淋巴结-转移（TNM）病理分期呈正相关，E2F8 和 RRM2 高表达预测 LUAD 患者的 5 年总生存率低。过表达和敲低实验表明，E2F8 是 LUAD 细胞增殖、DNA 合成和细胞周期进程所必需的，而这一过程依赖于 RRM2。报告基因、ChIP-qPCR 和 DNA 下拉-Western blot 分析表明，E2F8 通过直接与 LUAD 细胞中 RRM2 启动子结合，激活 RRM2 基因的转录。先前的研究表明，抑制 WEE1 激酶可以抑制 CDK1/2 的磷酸化并促进 RRM2 的降解。我们在这里进一步表明，E2F8 敲低与正在临床试验中评估的 WEE1 抑制剂 MK-1775 的联合使用，可协同抑制 LUAD 细胞的体外和体内增殖，并促进其凋亡。因此，这项研究揭示了 E2F8 通过激活 LUAD 中 RRM2 的表达作为原癌基因转录激活因子的新作用，靶向 RRM2 的转录和降解机制除了常规抑制 RR 酶活性外，还可能产生协同抑制 LUAD 治疗的效果。
