Protective effects of folic acid on DNA damage and DNA methylation levels induced by N-methyl-N'-nitro-N-nitrosoguanidine in Kazakh esophageal epithelial cells.

The protective effects of folic acid on DNA damage and DNA methylation induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in Kazakh esophageal epithelial cells were investigated using a 3 × 3 factorial design trial. The cells were cultured in vitro and exposed to media containing different concentrations of folic acid and MNNG, after which growth indices were detected. DNA damage levels were measured using comet assays, and genome-wide DNA methylation levels (MLs) were measured using high-performance liquid chromatography. The DNA methylation of methylenetetrahydrofolate reductase (MTHFR) and folate receptor-α (FRα) genes was detected by bisulfite sequencing polymerase chain reaction (PCR). The results showed significant increases in tail DNA concentration, tail length, and Olive tail moment (p < 0.01); a significant reduction of genome-wide DNA MLs (p < 0.01); and an increase in the methylation frequencies of MTHFR and FRα genes. In particular, significant differences were observed in the promoter regions of both genes (p < 0.01). Our study indicated that a reduction in folic acid concentration promotes DNA damage and DNA methylation in Kazakh esophageal epithelial cells upon MNNG exposure. Thus, sufficient folic acid levels could play a protective role against the damage induced by this compound.

MiR-940 inhibits the progression of NSCLC by targeting FAM83F.

OBJECTIVE: We investigate whether miR-940 could target family sequence similarity 83 member F (FAM83F) and further inhibit the progression of non-small cell lung cancer (NSCLC). PATIENTS AND METHODS: The expression levels of miR-940 and FAM83F in tumor tissues and paracancerous tissues of 72 NSCLC patients were detected through quantitative real time-polymerase chain reaction (qRT-PCR). The relationship between their expression levels, tumor size, and prognosis of NSCLC was analyzed. Transfection plasmids were constructed to knockdown or overexpress miR-940 in H1299 cells (inhibitor group) and SK-MES-1 cells (mimic group). The viability of H1299 cells and SK-MES-1 cells was evaluated using cell counting kit-8 (CCK-8) assay after transfection. The combination of miR-940 and Ago2 was confirmed by RNA immunoprecipitation (RIP) experiment. The binding condition of miR-940 in FAM83F-WT and FAM83F-MUT groups was verified by luciferase reporter gene assay. RESULTS: MiR-940 expression was noticeably decreased, while FAM83F expression was distinctly upregulated in NSCLC tissues than that of paracancerous tissues. The overall survival rate of NSCLC patients with highly-expressed miR-940 was significantly higher than those with lowly-expressed miR-940. Besides, miR-940 level was negatively correlated with tumor stage and size of NSCLC patients. Knockdown of miR-940 evidently enhanced the activity of H1299 cells, while overexpression of miR-940 decreased the viability of SK-MES-1 cells. In addition, miR-940 was confirmed to combine with FAM83F. Luciferase activity of cells co-transfected with FAM83F-WT and miR-940 mimic was significantly decreased. CONCLUSIONS: MiR-940 inhibited the proliferation of cancer cells by targeting FAM83F and further restrained the progression of NSCLC.