Vitamin C promotes apoptosis in breast cancer cells by increasing TRAIL expression

David W. Sant,Gaofeng Wang,Sushmita Mustafi,Joshua Chen,Christopher B. Gustafson,Joyce M. Slingerland

doi:10.1038/s41598-018-23714-7

Abstract

Genomic loss of 5-hydroxymethylcytosine (5hmC) accompanies malignant cellular transformation in breast cancer. Vitamin C serves as a cofactor for TET methylcytosine dioxygenases to increase 5hmC generation. Here we show that the transcription of SVCT2, a major vitamin C transporter, was decreased in human breast cancers (113 cases) compared to normal breast tissues from the same patients. A decreased SVCT2 expression was also observed in breast cancer cell lines. Treatment with vitamin C (100 μM) increased the 5hmC content in MDA-MB-231 breast cancer cells and markedly altered the transcriptome. The vitamin C treatment induced apoptosis in MDA-MB-231 cells, which was verified in two additional breast cancer cell lines. This pro-apoptotic effect of vitamin C appeared to be mediated by TRAIL, a known apoptosis inducer. Vitamin C upregulated TRAIL transcripts (2.3-fold increase) and increased TRAIL protein levels. The upregulation of TRAIL by vitamin C was largely abolished by siRNAs targeting TETs and anti-TRAIL antibody abrogated the induction of apoptosis. Furthermore, the apoptosis promoted by vitamin C was associated with Bax and caspases activation, Bcl-xL sequestration, and cytochrome c release. Taken together, these results suggest a potential role of physiological doses of vitamin C in breast cancer prevention and treatment.

Highlights

Aberrant epigenetic alterations, which reflect the interface of a dynamic microenvironment and the genome are involved in malignant cellular transformation[1]
Intracellular vitamin C deficiency would fail to maintain the catalytic activity of ten-eleven translocation (TET), resulting in the loss of 5hmC as observed in breast cancer[3,4,5,6]
Of the 113 breast cancer samples, the sodium-dependent vitamin C transporter 2 (SVCT2) expression was decreased in 72.5% (n = 82) by at least 1.5 fold compared to the matched normal breast tissues

Summary

Introduction

Aberrant epigenetic alterations, which reflect the interface of a dynamic microenvironment and the genome are involved in malignant cellular transformation[1]. The global loss of 5hmC could change DNA methylation-demethylation dynamics and gene transcription, further leading to a cascade that drives phenotypic transformation from normal breast epithelial cells to breast cancer cells. We and others recently showed that vitamin C, which has the capacity of reducing catalytic inactive Fe(III) to catalytic active Fe(II), upregulates the generation of 5hmC by acting as a cofactor for TET to hydroxylate 5mC11–15. This novel function of vitamin C to modulate DNA demethylation prompted us to test whether vitamin C treatment might upregulate TET action and have effects similar to TET overexpression in breast cancer cells. Treatment with vitamin C increases 5hmC content in breast cancer cells, changes the transcriptome, and induces apoptosis by increasing expression of the apoptosis inducer gene, TNF-related apoptosis-inducing ligand (TRAIL)

Methods

Results

Conclusion