Alkylating Agent–Induced NRF2 Blocks Endoplasmic Reticulum Stress–Mediated Apoptosis via Control of Glutathione Pools and Protein Thiol Homeostasis
Abstract
Alkylating agents are a commonly used cytotoxic class of anticancer drugs. Understanding the mechanisms whereby cells respond to these drugs is key to identify means to improve therapy while reducing toxicity. By integrating genome-wide gene expression profiling, protein analysis, and functional cell validation, we herein demonstrated a direct relationship between NRF2 and Endoplasmic Reticulum (ER) stress pathways in response to alkylating agents, which is coordinated by the availability of glutathione (GSH) pools. GSH is essential for both drug detoxification and protein thiol homeostasis within the ER, thus inhibiting ER stress induction and promoting survival, an effect independent of its antioxidant role. NRF2 accumulation induced by alkylating agents resulted in increased GSH synthesis via GCLC/GCLM enzyme, and interfering with this NRF2 response by either NRF2 knockdown or GCLC/GCLM inhibition with buthionine sulfoximine caused accumulation of damaged proteins within the ER, leading to PERK-dependent apoptosis. Conversely, upregulation of NRF2, through KEAP1 depletion or NRF2-myc overexpression, or increasing GSH levels with N-acetylcysteine or glutathione-ethyl-ester, decreased ER stress and abrogated alkylating agents–induced cell death. Based on these results, we identified a subset of lung and head-and-neck carcinomas with mutations in either KEAP1 or NRF2/NFE2L2 genes that correlate with NRF2 target overexpression and poor survival. In KEAP1-mutant cancer cells, NRF2 knockdown and GSH depletion increased cell sensitivity via ER stress induction in a mechanism specific to alkylating drugs. Overall, we show that the NRF2-GSH influence on ER homeostasis implicates defects in NRF2-GSH or ER stress machineries as affecting alkylating therapy toxicity. Mol Cancer Ther; 15(12); 3000–14. ©2016 AACR.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Dec 01, 2016
- Source ID
- 10.1158/1535-7163.mct-16-0271
Entities
People
- Alexander J.r. Bishop
- Alfeu Zanotto-Filho
- Aparna Gorthi
- Eva Loranc
- José C.f. Moreira
- Rosangela Mayer Gonçalves
- Sonal S. Tonapi
- V. Pragathi Masamsetti
- Xavier Bernard
- Yidong Chen
Organizations
- Cancer Prevention and Research Institute of Texas
- Federal University of Rio Grande do Sul
- Ministry of Science, Technology and Innovation
- National Cancer Institute
- National Institutes of Health
- United States Department of Defense
- Universidade Federal de Santa Catarina
- University of Texas Health Science Center at San Antonio