FOXP3 inhibits MYC expression via regulating miR-198 and influences cell viability, proliferation and cell apoptosis in HepG2.

OBJECTIVE: Our study aimed to explore the effects of FOXP3 expression on liver neoplasms cells and to further investigate the relationship between FOXP3 and proto-oncogene MYC.

METHODS: QRT-PCR was used for assessment of FOXP3 expression in liver neoplasms tissues and para-carcinoma tissues. The effects of FOXP3 on cell viability were determined by CCK8 assay, clone formation experiment, and flow cytometry. For miRNA selection, chips were used to figure out the differentially expressed miRNAs in FOXP3-overexpressing HepG2 cells. The result was followed by bioinformatics prediction to screen the possible MYC-targeted miRNAs, and it was examined by dual luciferase assay and ChIP assay. The expression levels of MYC protein and apoptosis-associated proteins (bcl2 and bax) were measured by Western blot assay.

RESULTS: It showed an under-regulated expression of FOXP3 in liver neoplasm tissues from qRT-PCR results. Overexpression of FOXP3 contributed to cell apoptosis as well as suppressed tumor cells' proliferation. MiR-198 was detected to be highly expressed in FOXP3-overexpressing HepG2 cells. FOXP3 regulated the transcription level of miR-198 by binding to its promoter sequence and overexpressed miR-198 could suppress tumor cells' proliferation and promote cell apoptosis. There existed targeted relationship between miR-198 and MYC gene. MiR-198 inhibited cancer by suppressing the expression of MYC in liver neoplasm.

CONCLUSION: FOXP3 up-regulated miR-198 expression by binding to its promoter sequence specifically, while miR-198 inhibited proto-oncogene MYC via targeted relationship. High level of miR-198 contributed to the apoptosis of tumor cells and suppressed cell viability meanwhile.