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Regulatory mechanism of extracellular signal-regulated kinase signal pathway for DNA methylation in lung carcinoma cells

Yu Sun, Wen-Zhou Liu, Tao Liu, Xu Feng, Nuo Yang, Hua-Fu Zhou

Objective: This study aimed to discuss the regulatory mechanism of Extracellular Signal-Regulated Kinase (ERK) signal pathway for DNA methylation in lung carcinoma cells.

Methodology: Human lung carcinoma cells were cultured, and the cells in logarithmic phase were inoculated in 96-hole plates and divided into three groups A-C. Six complex holes were present in each group. Phosphoric buffer salt solution, agonist epidermal growth factor, and blocker U1026 solution of ERK pathway were added into groups A-C, with a total amount of 25 μmol/L. Then, they were continuously treated for 48 h. Methyl thiazol tetrazolium method was used to determine cell proliferation rate. Fluorescent quantitative Polymerase Chain Reaction (qPCR) method was used to test the expression quantities of DNA transmethylase 1 (Dnmt1), DNA transmethylase 3a (Dnmt3a), DNA transmethylase 3b (Dnmt3b), tumor suppressor gene (p16), and Ras association domain family gene (RASSF1A) mRNA.

Results: Significant differences exist among groups A-C in cell proliferation rate, as well as in Dnmt1, Dnmt3a, Dnmt3b, p16, and RASSF1A mRNA, and their protein expression levels (P<0.05). Cell proliferation rate and the expression quantities of Dnmt1, Dnmt3a, and Dnmt3b mRNA and their protein expression levels in group B were significantly higher than those in groups A and C (P<0.05). By contrast, the expression quantities of p16 and RASSF1A mRNA and their protein expression levels were significantly lower than those in groups A and C (P<0.05). Cell proliferation rate and the expression quantities of Dnmt1, Dnmt3a, and Dnmt3bmRNA and their protein expression levels in group A were significantly higher than those in group C (P<0.05).

Conclusion: ERK signal pathway blocked both proliferation rate of lung carcinoma cells and DNA methylation level because of the down-regulation of Dnmts mRNA and their protein expression levels and the up-regulation of cancer suppressor genes p16 and RASSF1A mRNA and their protein expression levels.