Abstract:

AIM: To study the expression level of miRNA-222 and methylated CpG binding structural protein 2 (MBD2) in gastric cancer and its effect on proliferation and apoptosis of human gastric cancer cells. METHODS:Seventy-five patients with primary gastric cancer who were admitted to our hospital from February 2016 to May 2017 were selected as subjects. The expression levels of miR-222 and MBD2 in cancer tissues and adjacent tissues were detected. The correlation between miR-222 and MBD2 levels and clinicopathological parameters of gastric cancer were analyzed. The miR-222 inhibitor was transfected into gastric cancer SGC-7901 cells. The expression levels of miR-222 and MBD2 were detected by RT-PCR and Western blot, respectively. MTT assay and flow cytometry were used to detect. The effects of transfected cells on proliferation and apoptosis. RESULTS:The positive expression rate of miR-222 in gastric cancer tissues was significantly higher than that in adjacent tissues (P<0.05). The relative expression of miR-222 in gastric cancer tissues was significantly higher than that in adjacent tissues (P<0.05). The positive expression rate of MBD2 in gastric cancer tissues was significantly lower than that in adjacent tissues (P<0.05). The expression levels of miR-222 and MBD2 were significantly correlated with the degree of differentiation and TNM stage (P<0.05). The expression level of miR-222 in SGC-7901 cells transfected with miR-222 inhibitor was significantly lower than that in control group and NC group (P<0.05). The expression levels of MBD2 mRNA and protein in the cells transfected with miR-222 inhibitor were significantly higher than those in control group and NC group (P<0.05). The proliferation rate of cells transfected with miR-222 inhibitor was significantly lower than that of Control group and NC group (P<0.05), and the cell proliferation rate of miR-222 inhibitor+CDDP group was significantly lower than that of miR-222 inhibitor group and CDDP group. The apoptosis rate was significantly higher than that of miR-222 inhibitor group and CDDP group (P<0.05), and combined with CDDP could inhibit the proliferation rate of tumor cells and promote cell apoptosis. CONCLUSION: The expression of miR-222 in gastric cancer tissues is up-regulated in advanced gastric cancer tissues, and MBD2 is down-regulated significantly. The expression level of miR-222 is significantly correlated with the differentiation degree of gastric cancer and TNM stage. miR-222 can enhance the chemosensitivity of CDDP to gastric cancer，which may play a role in inhibiting the target gene MBD2 in gastric cancer.

Key words: gastric cancer, miR-222, MBD2, apoptosis