Methylation of the HOXA10 promoter directs miR-196b-5p dependent cell proliferation and invasion of gastric cancer cells
Menée in vitro et in vivo sur des modèles de cancer de l'estomac, cette étude met en évidence des mécanismes par lesquels, en induisant la surexpression du micro-ARN miR-196b-5p, la perte du gène TFF1 favorise la prolifération cellulaire et le processus invasif
The cross-talk between epigenetics and miRNA expression plays an important role in human tumorigenesis. Herein, we investigated the regulation and role of miR-196b-5p in gastric cancer. Using quantitative real-time RT-PCR, we demonstrate that miR-196b-5p is significantly overexpressed in human gastric cancer tissues (P<0.01). In addition, we also found that HOXA10, the host gene for miR-196b-5p, is overexpressed and positively correlated with miR-196b-5p expression levels (P<0.001). Quantitative pyrosequencing methylation analysis of HOXA10 promoter, demonstrated significantly lower levels of promoter DNA methylation of HOXA10 in gastric cancer samples, as compared to normal gastric mucosa samples (non-tumor control). Using 5-Aza-2'-deoxycytidine, we confirmed that demethylation of HOXA10 promoter induces the expression of HOXA10 and miR-196b-5p in gastric cancer cell models. Using the Tff1-KO mouse model of gastric neoplasia, we detected hypo- methylation and overexpression of HOXA10 and miR-196b-5p in gastric tumors, as compared to normal gastric mucosa from Tff1-WT mice. Mechanistically, we also found that reconstitution of TFF1 in human gastric cancer cell models leads to an increase in HOXA10 promoter methylation with reduced expression of HOXA10 and miR-196b-5p. Functionally, we found that miR-196b-5p reconstitution promoted human gastric cancer cell proliferation and invasion in in vitro cell models. In summary, we demonstrate overexpression of miR-196b-5p in gastric cancer. Our results suggest that TFF1 plays an important role in suppressing the expression of miR-196b-5p by mediating DNA methylation of HOXA10 promoter. Loss of TFF1 expression may promote proliferation and invasion of gastric cancer cells through induction of promoter hypo-methylation and expression of the HOXA10-miR-196b-5p axis. Implications These results indicate that the loss of TFF1 could promote the aberrant HOXA10 and miR-196b-5p overexpression by demethylating HOXA10 promoter, which provide a new perspective of TFF1-HOXA10-miR-196b-5p functions in human gastric cancer.