NAD(P)H:Quinone Oxidoreductase-1 Expression Sensitizes Malignant Melanoma Cells to the HSP90 Inhibitor 17-AAG

Shuya Kasai,Toshihide Akasaka,Wataru Shigeeda,Shinji Yasuhira,Ayaka Okubo,Nobuyuki Arakawa,Masahiko Shibazaki,Chihaya Maesawa,Tomoyuki Masuda,Andrzej T Slominski

doi:10.1371/journal.pone.0153181

Abstract

The KEAP1-NRF2 pathway regulates cellular redox homeostasis by transcriptional induction of genes associated with antioxidant synthesis and detoxification in response to oxidative stress. Previously, we reported that KEAP1 mutation elicits constitutive NRF2 activation and resistance to cisplatin (CDDP) and dacarbazine (DTIC) in human melanomas. The present study was conducted to clarify whether an HSP90 inhibitor, 17-AAG, efficiently eliminates melanoma with KEAP1 mutation, as the NRF2 target gene, NQO1, is a key enzyme in 17-AAG bioactivation. In melanoma and non-small cell lung carcinoma cell lines with or without KEAP1 mutations, NQO1 expression and 17-AAG sensitivity are inversely correlated. NQO1 is highly expressed in normal melanocytes and in several melanoma cell lines despite the presence of wild-type KEAP1, and the NQO1 expression is dependent on NRF2 activation. Because either CDDP or DTIC produces reactive oxygen species that activate NRF2, we determined whether these agents would sensitize NQO1-low melanoma cells to 17-AAG. Synergistic cytotoxicity of the 17-AAG and CDDP combination was detected in four out of five NQO1-low cell lines, but not in the cell line with KEAP1 mutation. These data indicate that 17-AAG could be a potential chemotherapeutic agent for melanoma with KEAP1 mutation or NQO1 expression.

Highlights

NRF2 is an oxidative stress-activated transcription factor that regulates transcription of a subset of genes including those encoding enzymes involved in antioxidant synthesis and detoxification [1,2]
The present study has clarified that melanoma and non-small cell lung carcinoma (NSCLC) cell lines showing NQO1 overexpression are sensitive to 17-AAG in comparison with cell lines showing low NQO1 expression
As observed in the present study, KEAP1 mutationindependent NRF2 activation may be evident in a high proportion of NQO1-high melanomas

Summary

Introduction

NRF2 is an oxidative stress-activated transcription factor that regulates transcription of a subset of genes including those encoding enzymes involved in antioxidant synthesis and detoxification [1,2]. We reported the presence of frame shift mutations in the KEAP1 gene and accumulation of NRF2 in melanoma tissues and melanoma cell lines [10]. NRF2 activation induces the expression of NQO1, which is a key enzyme for bioactivation of quinone-containing chemotherapeutic agents, such as geldanamycin, mitomycin C and β-lapachone [11]. These antitumor drugs are potential candidates for the treatment of melanoma that is resistant to dacarbazine or radiotherapy. Phase I/II clinical trials have reported that 17-AAG was partially effective against malignant melanoma after single administration or in combination with sorafenib or docetaxel, and that the effectiveness was independent of the oncogenic mutation status of patients [15,16,17,18,19,20]

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Results

Conclusion