Effects of folylpolyglutamate synthase modulation on CpG promoter DNA methylation and gene expression in human colon cancer cells

Abstract

Folylpolyglutamate synthase (FPGS) facilitates intracellular retention of folate by polyglutamylation, thereby playing a critical role in folate homeostasis. We investigated whether FPGS modulation would affect CpG promoter methylation and gene expression profiles in human HCT116 colon cancer cells. Illumina HT‐12 and Infinium Methylation assay were used, and functional analysis was performed by Ingenuity Pathway Analysis. We validated mRNA expression of selected genes by qRT‐PCR. 2897 genes (most involved pathways: cell cycle and DNA replication, recombination, and repair) were differentially expressed in the FPGS‐overexpressed cells, while 359 genes (most involved pathways: cell death and cell cycle) were differentially expressed in the FPGS‐inhibited cells. 864 and 626 genes showed altered CpG promoter methylation associated with FPGS overexpression and inhibition, respectively. An integrated analysis revealed 65 and 6 differentially expressed genes involved in cell cycle, cell death, and cell‐to‐cell signaling and interaction, expression of which was regulated by CpG promoter methylation changes associated with FPGS overexpression and inhibition, respectively. FPGS modulation can affect differential gene expression and CpG promoter methylation involved in important biological pathways, and some of the observed differential gene expression appear to be epigenetically regulated.Grant Funding Source: CIHR Fund 14126