TNF-α-Induced NF-κB Alter the Methylation Status of Some Stemness Genes in HT-29 Human Colon Cancer Cell

Acquisition of stem-like properties requires overcoming the epigenetic barrier of differentiation and re-expression of several genes involved in stemness and the cell cycle. DNA methylation is the classic epigenetic mechanism for de/differentiation. The writers and erasers of DNA methylation are not site-specific enzymes for altering specific gene methylation. Thus, the aim of the present study is investigation of the in vitro interaction of ten eleven translocations (TETs) with nuclear factor kappa B (NF-κB) in hypomethylation of stemness genes.

This experimental study was performed on HT-29 cells as human colorectal cancer cell lines. The interaction between TETs and DNA-methyltransferases 3 beta (DNMT3s) with p65 was achieved by coimmunoprecipitation. TETs were knocked down using siRNA, and the efficacy was analyzed by reverse-transcriptase polymerase chain reaction. The promoter methylation status of the target genes (NANOG, MYC) was determined by the methylation-sensitive high-resolution melting method.

TET3 and DNMT3b functionally interacted with p65 in samples through 25 ng/ml TNF-α treatment for 48 h in HT-29 cells. Transfection with siRNA significantly decreased the expression of TET enzymes after 72 h. Interestingly, treatment with TET siRNAs enhanced methylation of MYC and NANOG genes in samples with 25 ng/ml TNF-α treatment for 72 h in HT-29 cells. Moreover, methylation effects of TET3 were stronger than those of TET1 and TET2.

These results suggest that inflammation may alter the methylation status of genes required for stemness and predispose the cells to neoplastic alterations.