Arsenic trioxide induces cell cycle arrest and alters DNA methylation patterns of cell cycle regulatory genes in colorectal cancer cells.

Aims Cell cycle dysregulation is important in tumorigenesis. Transcriptional silencing of cell cycle regulatory genes, due to DNA methylation, is a common epigenetic event in malignancies. As 2 O 3 has been shown to induce cell cycle arrest and also to be a potential hypomethylating agent. Our study aimed to investigate DNA methylation patterns of cell cycle regulatory genes promoters, the effects of Arsenic trioxide (As 2 O 3 ) on the methylated genes and cell cycle distribution in colorectal cancer (CRC) cell lines. Main methods The methylation-specific PCR (MSP) and/or restriction enzyme-based methods were used to study the promoter methylation patterns of 24 cell cycle regulatory genes in CRC cell lines. Gene expression level and cell cycle distribution were determined by Real-time PCR and flow cytometric analyses, respectively. Key findings Our methylation analysis indicated that only promoters of RBL1 (p107), CHFR and p16 genes were aberrantly methylated in three cell lines. As 2 O 3 significantly decreased DNA methylation in promoter regions of these genes and restored their expression. We found that As 2 O 3 significantly reduced the expression of DNA methyltransferase 1 (DNMT1) and increased arsenic methyltransferase (AS3MT). Furthermore, As 2 O 3 altered transcriptional activity of several unmethylated cell cycle regulatory genes including cyclin B 1, E1, D1, GADD45A and p21. Cell cycle flow cytometry analysis showed As 2 O 3 induced G2/M arrest in all three cell lines. Significance These data suggest that demethylation and alteration in the expression level of the cell cycle-related genes may be possible mechanisms in As 2 O 3 -induced cell cycle arrest in colorectal cancer cells. [ABSTRACT FROM AUTHOR]