The down-regulation of SLC7A11 enhances ROS induced P-gp over-expression and drug resistance in MCF-7 breast cancer cells

Chun Ge,Siqi Feng,Dong Feng,Guangji Wang,Bei Cao,Jiye Aa,Fang Zhou,Jingwei Zhang,Na Yang

doi:10.1038/s41598-017-03881-9

Chun Ge, Siqi Feng + Show 7 more

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https://doi.org/10.1038/s41598-017-03881-9

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Abstract

Adriamycin (ADR) induces the over-expression of P-glycoprotein (P-gp) and multiple drug resistance in breast cancer cells. However, the biochemical process and underlying mechanisms are not clear. Our previous study revealed that ADR increased reactive oxygen species (ROS) generation and decreased glutathione (GSH) biosynthesis, while N-acetylcysteine, the ROS scavenger, reversed the over-expression of P-gp. The present study showed that ADR inhibited the influx of cystine (the source material of GSH) and the activity of the SLC7A11 transporter (in charge of cystine uptake) in MCF-7 cells. For the first time, we showed that the down-regulation/silence of SLC7A11, or cystine deprivation, or enhanced ROS exposure significantly increased P-gp expression in MCF-7 cells. The down-regulation of SLC7A11 markedly enhanced ROS induced P-gp over-expression and drug resistance in MCF-7 cells; a combination of either an inhibited/silenced SLC7A11 or cystine deprivation and increased ROS dramatically promoted P-gp expression, which could be reversed by N-acetylcysteine. In contrast, the over-expression of SLC7A11, or supplementation with sufficiently cystine, or treatment with N-acetylcysteine significantly decreased P-gp expression and activity. It was suggested that ROS and SLC7A11/cystine were the two relevant factors responsible for the expression and function of P-gp, and that SLC7A11 might be a potential target modulating ADR resistance.

Highlights

Chemotherapy is one of the most effective treatments in current breast cancer therapy
We found that the level of reactive oxygen species (ROS) in ADR-induced MCF-7R cells was approximately 4 times that in MCF-7S cells (Fig. 1A), and the baseline GSH/GSSG ratio of MCF-7R cells was lower than that of MCF-7S cells, indicating a poor capacity for the removal of ROS28, 29, in concordance with previous results (Fig. 1B)
It is commonly recognized that redox signals modulate the transporters of membrane proteins at genetic and proteomic levels[7,8,9,10,11,12,13,14], the underlying mechanism that contributes to P-gp over-expression remain unclear

Summary

Introduction

Chemotherapy is one of the most effective treatments in current breast cancer therapy. Cancer cell line MCF-7 can be induced by fairly low exposure to ADR in vitro to become the stable ADR-resistance cell line MCF-7R, with the distinct biological characteristic of hundreds of times higher P-gp expression. To date, it remains elusive which factor plays a crucial role in initiating the over-expression of P-gp, genomic and proteomic studies have suggested that potential factors such as cyclin, apoptin, microRNA-451, and Anxa[2] are involved at the transcriptional and posttranscriptional levels[7,8,9,10,11,12,13,14]. Our goal was to examine the specific role of elevated ROS coupled with a decreased anti-oxidative capacity in the ADR-induced over-expression of P-gp

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