低剂量顺铂通过p38MAPK介导的DNMT1下调降低p21与p16启动子甲基化上调p21与p16表达

Low-dose Cisplatin Upregulates p21 and p16 via Inhibition of Promoter Methylation by p38MAPK-Suppressed DNMT1

低剂量顺铂可通过诱导p21与p16表达而诱导肿瘤细胞早衰,但其机制不明。本研究探讨了低剂量顺铂诱导的He La细胞衰老过程中p21与p16的上调机制。低剂量顺铂(4μmol/L)处理He La细胞后,DNA甲基转移酶DNMT1蛋白水平降低;p21与p16启动子甲基化水平降低,二者mRNA及蛋白质水平升高;顺铂对DNMT1蛋白水平的降低作用与其激活p38MAPK有关,用SB203580抑制p38MAPK可部分逆转顺铂对DNMT1蛋白水平以及p21与p16启动子甲基化的降低作用,从而部分逆转顺铂对p21与p16表达的诱导;抑制p38MAPK也可部分逆转低剂量顺铂诱导的He La细胞早衰。上述结果表明,低剂量顺铂可通过p38MAPK信号通路下调p21与p16启动子甲基化水平,进而上调二者的表达。这些结果为解析低剂量顺铂诱导肿瘤细胞早衰的信号转导机制提供了实验依据。

Low-dose cisplatin induces premature senescence of cancer cells by elevating the expression of p21 and p16. However,the mechanisms underlying cisplatin-induced upregulation of p21 and p16 are not fully elucidated. In the present study,we investigated the mechanisms controlling the expression of p21 and p16 in low-dose cisplatin-induced premature senescence. Our results showed that treatment of He La cells by low-dose cisplatin（ 4 μmol/L） decreased the protein levels of DNMT1 and the promoter methylation of p21 and p16,thereby elevating the mRNA and protein levels of p21 and p16. Activation of p38 MAPK is responsible for the reduction of DNMT1 in response to low-dose cisplatin,since preincubating cells with p38 MAPK inhibitor SB203580 could partly reverse the effect of cisplatin in reducing the protein levels of DNMT1 and the promoter methylation of p21 and p16. Furthermore,inhibition of p38 MAPK by SB203580 reversed cisplatin-induced premature senescence. In sum,cisplatin reduces the promoter methylation of p21 and p16 via activating p38 MAPK,which in turn,increases the expression of p21 and p16 in premature senescence. These studies provide evidence for elucidating the mechanisms underlying low-dose cisplatin-induced premature senescence.