Objective To investigate the expression level of serine/threonine phosphoprotein phosphatase 4C(PPP4C)in gastric cancer,and analyze its relationship with prognosis and the underlying regulatory mechanism.Methods The clinical data of 104 gastric cancer patients admitted to the First Affiliated Hospital of Bengbu Medical College between January 2012 and August 2016 were collected.Immunohistochemical staining was employed to determine the expression levels of PPP4C and Ki-67 in the gastric cancer tissue.The gastric cancer cell lines BGC823 and HGC27 were cultured and transfected with the vector for PPP4C knockdown,the vector for PPP4C overexpression,and the lentiviral vector(control),respectively.The effects of PPP4C on the cell cycle and proliferation were analyzed and the possible regulatory mechanisms were explored.Results PPP4C was highly expressed in gastric cancer(P<0.001),and its expression promoted malignant progression of the tumor(all P<0.01).Univariate and Cox multivariate analysis clarified that high expression of PPP4C was an independent risk factor affecting the 5-year survival rate of gastric cancer patients(P=0.003).Gene ontology and Kyoto encyclopedia of genes and genomes enrichment analysis suggested that PPP4C may be involved in the cell cycle.The correlation analysis showed that the expression of PPP4C was positively correlated with that of Ki-67 in gastric cancer(P<0.001).The up-regulation of PPP4C expression increased the proportion of tumor cells in the S phase,alleviated the G2/M phase arrest,and promoted the proliferation of gastric cancer cells and the expression of cyclin D1 and cyclin-dependent kinase 6(CDK6)(all P<0.05).The down-regulation of PPP4C decreased the proportion of gastric cancer cells in the S phase,promoted G2/M phase arrest,and inhibited cell proliferation and the expression of cyclin D1,CDK6,and p53(all P<0.05).p53 inhibitors promoted the proliferation of BGC823 and HGC27 cells in the PPP4C knockdown group(P<0.001,P<0.001),while p53 activators inhibited the proliferation of BGC823 and HGC27 cells in the PPP4C overexpression group(P<0.001,P=0.002).Conclusions PPP4C is highly expressed in gastric cancer and affects the prognosis of the patients.It may increase the proportion of gastric cancer cells in the S phase and alleviate the G2/M phase arrest by inhibiting p53 signaling,thereby promoting cell proliferation.
目的 分析丝氨酸/苏氨酸磷酸蛋白磷酸酶4C(PPP4C)在胃癌中的表达水平及与预后的相关性,并探究其可能的作用途径和机制。方法 收集2012年1月至2016年8月蚌埠医学院第一附属医院收治的104例胃癌患者的临床资料,采用免疫组织化学染色技术检测胃癌组织中PPP4C和Ki-67的表达水平。培养BGC823和HGC27胃癌细胞,分别转染PPP4C敲减、过表达和对照慢病毒载体,分析PPP4C对细胞周期和增殖的影响及可能的调控机制。结果 PPP4C在胃癌组织中呈高表达(P<0.001),且与肿瘤的恶性进展呈正相关(P均<0.01)。单因素和Cox回归模型分析显示,PPP4C高表达是影响胃癌患者术后5年生存率的独立危险因素(P=0.003)。基因功能注释和京都基因与基因组组百科全书富集分析提示PPP4C生物学功能可能与细胞周期有关。相关性分析显示胃癌组织中PPP4C与Ki-67的表达量呈正相关(P<0.001)。上调PPP4C增加S期胃癌细胞比例和减缓G2/M期阻滞,并促进细胞增殖以及Cyclin D1和细胞分裂蛋白激酶6(CDK6)、p53的表达(P均<0.05);下调PPP4C减少S期胃癌细胞比例和促进G2/M期阻滞,抑制细胞增殖以及Cyclin D1、CDK6和p53的表达(P均<0.05)。p53抑制剂促进PPP4C敲减组BGC823和HGC27胃癌细胞的增殖(P<0.001,P<0.001),p53激活剂抑制PPP4C过表达组BGC823和HGC27胃癌细胞的增殖(P<0.001,P=0.002)。结论 PPP4C在胃癌中高表达且影响患者预后,其可能通过抑制p53信号通路增加S期胃癌细胞比例和减缓G2/M期阻滞,进而促进细胞增殖。.
Keywords: cell cycle; gastric cancer; p53; prognosis; serine/threonine phosphoprotein phosphatase 4C.