Methylation levels of P16 and TP53 that are involved in DNA strand breakage of 16HBE cells treated by hexavalent chromium

• Thehypermethylation of CpG1, CpG31 and CpG32 of p16 were observed in Cr(VI) treated groups.
• The methylation level of CpG1 of p16 can enhance cell damage by regulating its expression or affecting some transcription factors to combine with their DNA strand sites.
• The CpG1methylation level of p16 could be used as a biomarker of epigenetic effect caused by Cr(VI) treatment.

The correlations between methylation levels of p16 and TP53 with DNA strand breakage treated by hexavalent chromium [Cr(VI)] remain unknown. In this research, Human bronchial epithelial cells (16HBE cells) in vitro and bioinformatics analysis were used to analyze the epigenetic role in DNA damage and potential biomarkers. CCK-8 and single cell gel electrophoresis assay were chosen to detect the cellular biological damage. MALDI-TOF-MS was used to detect the methylation levels of p16 and TP53. qRT-PCR was used to measure their expression levels in different Cr(VI) treatment groups. The transcription factors with target sequences of p16 and TP53 were predicted using various bioinformatics software. The findings showed that the cellular toxicity and DNA strand damage were Cr(VI) concentration dependent. The hypermethylation of CpG1, CpG31 and CpG32 of p16 was observed in Cr(VI) treated groups. There was significant positive correlation between the CpG1 methylation level of p16 and cell damage. In Cr(VI) treated groups, the expression level of p16 was lower than that in control group. The expression level of TP53 increased when the Cr(VI)concentration above 5 μM. About p16, there was significant negative correlation between the CpG1 methylation levels with its expression level. A lot of binding sites for transcription factors existed in our focused CpG islands of p16. All the results suggested that the CpG1 methylation level of p16 could be used as a biomarker of epigenetic effect caused by Cr(VI) treatment, which can enhance cell damage by regulating its expression or affecting some transcription factors to combine with their DNA strand sites.