Shan Jinlan, Wang Zhen, Mo Qiuping, Long Jingpei, Fan Yangfan, Cheng Lu, Zhang Tao, Liu Xiyong, Wang Xiaochen
Department of Surgery, Women's Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China; Department of Cancer Institute, Zhejiang University, Hangzhou, Zhejiang, China.
Department of Breast Surgery and Oncology, Key Laboratory of Cancer Prevention and Intervention, Ministry of Education, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China.
Pancreatology. 2022 Apr;22(3):401-413. doi: 10.1016/j.pan.2022.03.002. Epub 2022 Mar 5.
BACKGROUND/OBJECTIVES: Ribonucleotide Reductase M2 subunit (RRM2) is elevated in pancreatic cancer and involved in DNA synthesis and cell proliferation. But its specific mechanism including genetic differences and upstream regulatory pathways remains unclear.
We analyzed RRM2 expression of 178 pancreatic cancer patients in Gene Expression Profiling Interactive Analysis (GEPIA) database. Besides, more pancreatic cancer specimens were collected and detected RRM2 expression by immunohistochemistry. RRM2 knockdown by shRNA was applied for functional and mechanism analysis in vitro. Xenograft tumor growth was significantly slower by RRM2 silencing in vivo.
It showed that high RRM2 expression had a poorer overall survival and disease free survival. RRM2 expression was higher in tumor grade 2 and 3 than grade 1. Immunohistochemistry data validated that high RRM2 expression predicted worse survival. RRM2 knockdown significantly reduced cell proliferation, inhibited colony formation and suppressed cell cycle progress. Further mechanism assay showed silencing RRM2 lead to inactivation of PI3K/AKT/mTOR pathway and inhibition of mutant p53, which induce S phase arrest and/or apoptosis. In panc-1 cells, S-phase arrest mediated by mutant p53 inhibition, p21 increase and cell cycle related proteins change. While in miapaca-2 cells, induction of apoptosis and S-phase arrest mediated by CDK1 played a coordinated role.
Taken together, high RRM2 expression was associated with worse prognosis. Importantly, RRM2 knockdown deactivated PI3K/AKT/mTOR pathway, resulting in cell cycle arrest and/or apoptosis. This study shed light on the molecular mechanism of RRM2 in pancreatic tumor progression and is expected to provide a new theoretical basis for pancreatic cancer treatment.
背景/目的：核糖核苷酸还原酶M2亚基（RRM2）在胰腺癌中表达升高，参与DNA合成和细胞增殖。但其具体机制，包括基因差异和上游调控途径仍不清楚。
我们在基因表达谱交互式分析（GEPIA）数据库中分析了178例胰腺癌患者的RRM2表达。此外，收集了更多胰腺癌标本，通过免疫组织化学检测RRM2表达。应用shRNA敲低RRM2进行体外功能和机制分析。在体内，RRM2沉默显著减缓了异种移植肿瘤的生长。
结果显示，RRM2高表达患者的总生存期和无病生存期较差。RRM2在2级和3级肿瘤中的表达高于1级。免疫组织化学数据证实，RRM2高表达预示着较差的生存率。RRM2敲低显著降低细胞增殖，抑制集落形成并抑制细胞周期进程。进一步的机制分析表明，沉默RRM2导致PI3K/AKT/mTOR通路失活并抑制突变型p53，从而诱导S期阻滞和/或凋亡。在panc-1细胞中，由突变型p53抑制、p21增加和细胞周期相关蛋白变化介导S期阻滞。而在miapaca-2细胞中，由CDK1介导的凋亡诱导和S期阻滞起协同作用。
综上所述，RRM2高表达与较差的预后相关。重要的是，RRM2敲低使PI3K/AKT/mTOR通路失活，导致细胞周期阻滞和/或凋亡。本研究阐明了RRM2在胰腺肿瘤进展中的分子机制，有望为胰腺癌治疗提供新的理论依据。
