# Anticancer effects of zinc ion-mediated DNA demethylation in oesophageal squamous cell carcinoma

## TL;DR

Zinc ions reduce DNA methylation and cancer cell aggression in esophageal cancer, suggesting a potential new treatment approach.

## Contribution

Zn2+ was shown to inhibit ESCC malignancy via DNA demethylation and enhance cisplatin efficacy.

## Key findings

- Zn2+ treatment reduced CpG methylation in promoter regions of ESCC and control cells.
- Zn2+ increased RNA expression of MT1E, MT1H, and MT1X genes by decreasing their DNA methylation.
- Zn2+ combined with cisplatin showed greater inhibition of ESCC cells than cisplatin alone.

## Abstract

Abnormalities in trace elements and the incidence of oesophageal squamous cell carcinoma (ESCC) have been reported in China. Zinc ions (Zn2+) are known to regulate DNA methylation by stabilizing methylase activity. However, the relationship between DNA methylation and Zn2+ dysregulation in ESCC cells remains unclear. In this study, we examined changes in the biological behavior of ESCC cells treated with or without Zn2+.

Biological behaviour changes in ESCC cells treated with or without Zn2+ were analysed. Differences in the methylome and transcriptome of Zn2+-treated cells were determined by reduced representation bisulfite sequencing and RNA sequencing. An MTT cell viability assay was used to evaluate the cytotoxicity of cisplatin combined with Zn2+.

Zn2+ can inhibit the malignant biological behaviour of ESCC cells. CpG methylation levels of promoter regions were decreased after Zn2+ treatment in both ESCC and control cells. The degree of DNA methylation of genes encoding the metal ion-binding factors MT1E, MT1H and MT1X was significantly decreased, but their RNA expression levels were significantly increased after Zn2+ treatment. Zn2+ may enhance the expression of metallothioneins (MTs) via positive feedback through methylation regulation mechanisms. In vitro assays showed that the IC50 of Zn2+ in ESCC cells was significantly lower than that in cells treated with cisplatin alone. In addition, ECa patients with high MT1E expression had a better prognosis.

Zn2+ can reduce the methylation level and malignant biological behaviour of ESCC cells. The combination of Zn2+ and cisplatin increases ESCC inhibition. Further study of MTs as biomarkers and targets in ESCC is warranted.