miR-212 as potential biomarker suppresses the proliferation of gastric cancer via targeting SOX4.

BACKGROUND: Circulating microRNAs that post-transcriptionally regulate gene expressions have been reported as promising biomarkers in cancer monitoring. This study was to identify the potential role of circulating miR-212 in gastric cancer and whether it could serve as a novel biomarker for gastric cancer. METHODS: We detected the serum levels of miR-212 in 100 health people and 110 gastric cancer patients and analyzed the relationships of the serum level of miR-212 with gastric cancer. We detected the expression of miR-212 in human gastric mucosal epithelial cell line (GES-1) and human gastric cancer cell lines (NCI-N87 and SNU-16) using qRT-PCR. Then, we detected the role of 5-aza-deoxycytidine on the epigenetic regulation of miR-212 in human gastric cancer cell lines. Furthermore, luciferase reporter assay was used to detect binding activity of miR-212 on SOX4 mRNA, and their functions on the cell proliferation and apoptosis. RESULTS: The expression of miR-212 was higher in health people than that in gastric cancer patients, higher in gastric mucosal epithelial cell line than that in gastric cancer cells. miR-212 can be a circulating biomarker and an independent prognostic factor of gastric cancer. Moreover, miR-212 can directly regulate the 3'UTR of SOX4 mRNA to suppress p53 and Bax, resulting gastric cancer cells proliferation inhibition and apoptosis induction. CONCLUSION: Our study demonstrated that miR-212 was epigenetically downregulated in gastric cancer, and resulting low level of miR-212 can be a potential circulating biomarker and poor prognosis predicator of gastric cancer.

[Effect of 5-aza-2'-deoxycytidine on growth and methylation of RUNX3 gene in human pancreatic cancer cell line MiaPaca2].

OBJECTIVE: To investigate the effect of demethylating agent 5-aza-2'-deoxycytidine (5-Aza-CdR) on the growth of human pancreatic cancer cell line MiaPaca2 and the expression and methylation of tumor suppressor gene RUNX3. METHODS: Human pancreatic cancer cell line MiaPaca2 cells were treated with different concentrations of 5-Aza-CdR. Morphological changes of MiaPaca2 cells were observed by light microscopy. The activity of cell proliferation was analyzed by MTT assay. The changes of RUNX3 mRNA expression were detected by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR). Changes of RUNX3 gene methylation was detected by methylation-specific polymerase chain reaction. RESULTS: MiaPaca2 cells were treated with 2.5, 5, 10 and 20 µmo1/L 5-Aza-CdR, respectively. The inhibition rates of MiaPaca2 cells treated for 24 h were (9.17 ± 2.15)%, (10.75 ± 2.04)%, (12.57 ± 1.64)% and (18.70 ± 1.51)%, respectively. The inhibition rates were (14.94 ± 1.68)%, (18.60 ± 1.57)%, (22.84 ± 1.58)% and (33.24 ± 1.53)%, respectively, after 48 h treatment; (21.46 ± 1.60)%, (28.62 ± 1.72)%, (35.14 ± 1.64)% and (45.06 ± 1.47)%, respectively, after 72 h treatment; and (26.35 ± 1.71)%, (34.48 ± 1.69)%, (40.05 ± 1.60)% and (49.99 ± 1.61)%, respectively, after 96 h treatment. The differences between inhibition rates of each experimental and control groups (0.00 ± 0.00)% were statistically significant (P < 0.05). At the same time, the inhibition rates of different concentration groups showed significant differences (P < 0.05). At 48 h, 72 h and 96 h, the inhibition rates of each pair concentration groups showed significant differences (P < 0.05). 5-Aza- CdR inhibited the growth of MiaPaca2 cells, and the higher the concentration, the stronger the inhibition after 24 h. 5-Aza-CdR also reversed the methylation status of RUNX3 gene, and restored the expression of RUNX3 mRNA with a dose-effect relationship. CONCLUSIONS: The methylation of RUNX3 gene is significantly related with the occurrence and development of pancreatic cancer, and abnormal methylation of RUNX3 gene may contribute to the loss of RUNX3 mRNA expression. 5-Aza-CdR may effectively cause reversion of RUNX3 methylation, and treatment with 5-Aza-CdR can reactivate the gene expression and inhibit the cell growth. This may provide a new way for diagnosis and treatment of pancreatic cancer.