Re-expression of ARHI (DIRAS3) induces autophagy in breast cancer cells and enhances the inhibitory effect of paclitaxel

Chun-Fang Zou,Yinhua Yu,Hongyan Jin,Ming Yao,Luoqi Jia,Naiqing Zhao,Zhen Lu,Youji Feng,Robert C Bast,Jin Huan

doi:10.1186/1471-2407-11-22

Abstract

BackgroundARHI is a Ras-related imprinted gene that inhibits cancer cell growth and motility. ARHI is downregulated in the majority of breast cancers, and loss of its expression is associated with its progression from ductal carcinoma in situ (DCIS) to invasive disease. In ovarian cancer, re-expression of ARHI induces autophagy and leads to autophagic death in cell culture; however, ARHI re-expression enables ovarian cancer cells to remain dormant when they are grown in mice as xenografts. The purpose of this study is to examine whether ARHI induces autophagy in breast cancer cells and to evaluate the effects of ARHI gene re-expression in combination with paclitaxel.MethodsRe-expression of ARHI was achieved by transfection, by treatment with trichostatin A (TSA) or by a combination of TSA and 5-aza-2'-deoxycytidine (DAC) in breast cancer cell cultures and by liposomal delivery of ARHI in breast tumor xenografts.ResultsARHI re-expression induces autophagy in breast cancer cells, and ARHI is essential for the induction of autophagy. When ARHI was re-expressed in breast cancer cells treated with paclitaxel, the growth inhibitory effect of paclitaxel was enhanced in both the cell culture and the xenografts. Although paclitaxel alone did not induce autophagy in breast cancer cells, it enhanced ARHI-induced autophagy. Conversely, ARHI re-expression promoted paclitaxel-induced apoptosis and G2/M cell cycle arrest.ConclusionsARHI re-expression induces autophagic cell death in breast cancer cells and enhances the inhibitory effects of paclitaxel by promoting autophagy, apoptosis, and G2/M cell cycle arrest.

Highlights

ARHI is a Ras-related imprinted gene that inhibits cancer cell growth and motility
Paclitaxel was used at concentrations of 2 nM-4 nM, demethylating agent 5-aza-2’deoxycytidine (DAC) was used at a concentration of 800 nM, and trichostatin A (TSA) was used at concentrations of 40 nM-200 nM, depending on the particular cell lines and experiments
In MDA-MB231 cells, in which ARHI was hypermethylated, neither DAC nor TSA alone affected the expression of ARHI; robust re-expression of ARHI was detected when cells were treated with a combination of DAC and TSA, demonstrating that these two reagents have synergistic effects (P < 0.001) (Figure 1B)

Summary

Introduction

ARHI is a Ras-related imprinted gene that inhibits cancer cell growth and motility. ARHI is downregulated in the majority of breast cancers, and loss of its expression is associated with its progression from ductal carcinoma in situ (DCIS) to invasive disease. The purpose of this study is to examine whether ARHI induces autophagy in breast cancer cells and to evaluate the effects of ARHI gene re-expression in combination with paclitaxel. Breast cancer remains a leading cause of morbidity and mortality in women [1]. Paclitaxel significantly improved the rates of those who became disease-free and the overall survival rate in breast cancer patients [3,4,5,6]. It has become an integral component of first-line adjuvant chemotherapy [7]. New approaches are needed to improve the efficacy of paclitaxel

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