Metformin regulates expression of DNA methyltransferases through the miR-148/-152 family in non-small lung cancer cells

Abstract

Background To understand the molecular mechanisms involved in regulation of DNA methyltransferases (DNMTs) by metformin in non-small cell lung cancer (NSCLC) cells. Methods Expression levels of DNMTs in response to metformin were analyzed in NSCLC cells. MicroRNAs regulating expression of DNMTs at the post-transcriptional level were searched using miRNA-target databases (miRDB and miRTarBase), TCGA RNASeqV2 lung cancer data, and miRNA-seq. Results Metformin dose-dependently downregulated expression of DNMT1 and DNMT3a at the post-transcriptional level and expression of DNMT3b at the transcriptional level in A549 lung cancer cells. Activity of DNMTs was reduced by about 2.6-fold in A549 cells treated with 10 mM metformin for 72 h. miR-148/-152 family members (miR-148a, miR-148b, and miR-152) targeting the 3′UTR of DNMTs were associated with post-transcriptional regulation of DNMTs by metformin. Metformin upregulated expression of miR-148a, miR-148b, and miR-152 in A549 and H1650 cells. Transfection with an miR-148b plasmid or a mimic suppressed expression of DNMT1 and DNMT3b in A549 cells. Transfection with the miR-148a mimic in A549 and H1650 cells decreased the luciferase activity of DNMT1 3′UTR. A combination of metformin and cisplatin synergistically increased expression levels of miR-148/-152 family members but decreased expression of DNMTs in A549 cells. Low expression of miR-148b was associated with poor overall survival (HR = 2.56, 95% CI 1.09—6.47; P = 0.04) but not with recurrence-free survival. Conclusions The present study suggests that metformin inhibits expression of DNMTs by upregulating miR-148/-152 family members in NSCLC cells.

DNMT1/miR-152-3p/SOS1 signaling axis promotes self-renewal and tumor growth of cancer stem-like cells derived from non-small cell lung cancer

“…The results indicated that miR-152-3p exhibited lower expression levels in LCSLCs corresponding to A549 and H460 cells (Fig. 1 C and 1D).Additionally, within the DNMT family, comprising DNMT1, DNMT3a, and DNMT3b [ 29 ], we determined the transcript levels of the DNMT family members in A549, H460 cell lines and their corresponding LCSLCs and BEP2D cell lines. The results indicated that DNMT1 exhibited higher levels in the corresponding LCSLCs (Fig.…”

“…Emerging evidence has already unveiled a link between DNMT1 and miR-152-3p in previous studies [ 29 , 52 ]. However, the intricate mechanisms underlying the interplay between miR-152-3p and SOS1 in tumors remained largely unexplored.…”

“…By contrast, the low expression of miR-152 upregulates the expression level of DNMT1, resulting in DNMT1-mediated DNA promoter methylation and the development of a negative DNMT1/miR-152 loop [ 26 – 28 ]. Recently, biguanides have been shown to modulate DNMT1/miR-152 expression in lung cancer [ 29 ]. However, the precise mechanism governing the self-renewal and tumor growth of LCSLCs through the interaction of DNMT1 and miR-152 remains unclear.…”

“…The guanine nucleotide exchange factor SOS1 plays a critical role in modulating drug sensitivity in gastroesophageal cancer [ 30 ]. Additionally, miR-152 and miR-148, being part of the same gene family [ 29 ], have been shown to disrupt various signaling pathways involving SOS1 and SOS2 proteins in B cells [ 31 ]. The potential for enhancing the efficacy of multiple tumors lies in the modulation of SOS1 expression [ 32 – 34 ].…”

Mechanisms of Regulation of the Expression of miRNAs and lncRNAs by Metformin in Ovarian Cancer

“…Metformin has been shown to decrease intracellular S-adenosylhomocysteine (SAH), a strong feedback inhibitor of SAM-dependent DNMTs, by promoting the enzymatic activity of SAH hydrolase (SAHH) in non-cancerous cells and breast, endometrial, and hypopharyngeal cancer cells [74,81,82]. Metformin can also modulate the expression of DNMTs, downregulating their expression in lung cancer cells [83] and, conversely, upregulating their expression in hypopharyngeal cancer cells [74]. Therefore, the influence of metformin on DNMTs and its effects on the methylation status of ncRNAs appear to be tumor-dependent.…”