Changes in the Expression of miR-381 and miR-495 Are Inversely Associated with the Expression of the MDR1 Gene and Development of Multi-Drug Resistance

Yan Xu,Zhiyong Mao,Guangming Gong,Zhen Li,Jun Y Fan,M Frances Shannon,Qiao Wang,Stephen J Ohms,Yiqiao Hu,Partha Mukhopadhyay

doi:10.1371/journal.pone.0082062

Abstract

Multidrug resistance (MDR) frequently develops in cancer patients exposed to chemotherapeutic agents and is usually brought about by over-expression of P-glycoprotein (P-gp) which acts as a drug efflux pump to reduce the intracellular concentration of the drug(s). Thus, inhibiting P-gp expression might assist in overcoming MDR in cancer chemotherapy. MiRNAome profiling using next-generation sequencing identified differentially expressed microRNAs (miRs) between parental K562 cells and MDR K562 cells (K562/ADM) induced by adriamycin treatment. Two miRs, miR-381 and miR-495, that were strongly down-regulated in K562/ADM cells, are validated to target the 3’-UTR of the MDR1 gene. These miRs are located within a miR cluster located at chromosome region 14q32.31, and all miRs in this cluster appear to be down-regulated in K562/ADM cells. Functional analysis indicated that restoring expression of miR-381 or miR-495 in K562/ADM cells was correlated with reduced expression of the MDR1 gene and its protein product, P-gp, and increased drug uptake by the cells. Thus, we have demonstrated that changing the levels of certain miR species modulates the MDR phenotype in leukemia cells, and propose further exploration of the use of miR-based therapies to overcome MDR.

Highlights

Multidrug resistance (MDR) is one of the main obstacles to the successful treatment of cancer patients with chemotherapeutic agents
An approximate 5000-fold increase in MDR1 mRNA expression was stably achieved in K562/ADM cells compared to the parental K562 cells after prolonged induction with ADM (Figure 1A)
We obtained a genome-wide profile of drug-induced miRs in human leukemia K562 cells using next-generation sequencing and identified and validated two miRs, miR-381 and miR-495, that may play a role in regulating the MDR1 gene in leukemia cells

Summary

Introduction

Multidrug resistance (MDR) is one of the main obstacles to the successful treatment of cancer patients with chemotherapeutic agents. As a prevalent clinical phenotype, cancer cells from patients who have been exposed to one chemotherapeutic agent, become resistant to that agent and develop cross-resistance to a wide range of other chemotherapeutic agents [1]. In addition to its physiologic expression in normal tissues, it is expressed and, mostly, over-expressed, in certain human tumors [6]. Tumors derived from tissues expressing P-gp are normally resistant to chemotherapy. Some other tumors, such as breast tumors and leukemia, with low or no expression of P-gp, develop MDR only after treatment with anti-cancer drugs when the over-expression of P-gp is induced [7]

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Results

Conclusion