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

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.

Autophagy as a mediator of chemotherapy-induced cell death in cancer

“…The first examples are for DNA-damaging agents in cell models in which autophagy is inhibited either by pharmacological inhibitors like 3-methyladenine or by the use of siRNA targeting Beclin-1, Atg5 or Atg7: hepatoma cells [42] or cervical carcinoma cells [43] exposed to etoposide, papillary thyroid cancer cells [44] or different sarcoma cell lines [45] incubated with doxorubin, cervical cancer SiHa cells exposed to carboplatin [46] or pancreatic cancer cells treated with gemcitabine [47]. Autophagy also contributes to cell death induced by microtubule targeting agents like paclitaxel [48,49] as well as by the new "smart" drugs. The cytotoxicity induced by imatinib, an inhibitor of the tyrosine kinase activity of growth factor receptors, is decreased if autophagy is inhibited in human early stage malignant glioma cells [50].…”

Breast cancer cells are arrested at different phases of the cell cycle following the re-expression of ARHI

“…ARHI is a member of the Ras superfamily, yet it exhibits unique tumor suppressor activity (16). In addition, ARHI contains a unique 34 amino acid extension at its N-terminus and exhibits high affinity for GTP despite having low intrinsic GTPase activity (6).…”

“…Recently, the transfection of the eukaryotic expression vector, pcDNA3.1-ARHI, into a human lung cancer cell line and HER2-positive breast cancer cells (SK-BR-3 and JIMT-1) was shown to affect cell proliferation, apoptosis and cell invasion in both models (4). The treatment of various cancer cell lines with trichostatin A (TSA) and 5-aza-2'-deoxycytidine (DAC) has also been reported to induce the expression of ARHI (16,17). However, exogenous ARHI expression vs. drug-induced ARHI expression are associated with different antitumor effects.…”

Histone deacetylase modulators provided by Mother Nature

“…Suberoyanilide hydroxamic acid (SAHA) is a synthetic derivative of TSA, which was approved by FDA (Food and Drug Administration) for the treatment of cutaneous T-cell lymphoma in 2006 (Wagner et al 2010). Interestingly, cells treated by these two related molecules enter in autophagy to protect themself from the stress induced by these drugs (Shao et al 2004;Zou et al 2011). Moreover, regarding the involvement of HDAC6 in the formation of aggresomes, tubacin, a synthetic hydroxamic acid that inhibits specifically HDAC6, should be able to impair autophagy (Hideshima et al 2005).…”