Regulatory role of KEAP1 and NRF2 in PPARγ expression and chemoresistance in human non-small-cell lung carcinoma cells.
The nuclear factor-E2-related factor 2 (NRF2) serves as a master regulator in cellular defense against oxidative stress and chemical detoxification. However, persistent activation of NRF2 resulting from mutations in NRF2 and/or downregulation of or mutations in its suppressor, Kelch-like ECH-associated protein 1 (KEAP1), is associated with tumorigenicity and chemoresistance of non-small-cell lung carcinomas (NSCLCs). Thus, inhibiting the NRF2-mediated adaptive antioxidant response is widely considered a promising strategy to prevent tumor growth and reverse chemoresistance in NSCLCs. Unexpectedly, stable knockdown of KEAP1 by lentiviral shRNA sensitized three independent NSCLC cell lines (A549, HTB-178, and HTB-182) to multiple chemotherapeutic agents, including arsenic trioxide (As(2)O(3)), etoposide, and doxorubicin, despite moderately increased NRF2 levels. In lung adenocarcinoma epithelial A549 cells, silencing of KEAP1 augmented the expression of peroxisome proliferator-activated receptor γ (PPARγ) and genes associated with cell differentiation, including E-cadherin and gelsolin. In addition, KEAP1-knockdown A549 cells displayed attenuated expression of the proto-oncogene cyclin D1 and markers for cancer stem cells (CSCs) and reduced nonadherent sphere formation. Moreover, deficiency of KEAP1 led to elevated induction of PPARγ in response to As(2)O(3). Pretreatment of A549 cells with PPARγ agonists activated PPARγ and augmented the cytotoxicity of As(2)O(3). A mathematical model was formulated to advance a hypothesis that differential regulation of PPARγ and detoxification enzymes by KEAP1 and NRF2 may underpin the observed landscape changes in chemosensitivity. Collectively, suppression of KEAP1 expression in human NSCLC cells resulted in sensitization to chemotherapeutic agents, which may be attributed to activation of PPARγ and subsequent alterations in cell differentiation and CSC abundance.
Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.
Lijuan
L
Zhan
Hao
H
Zhang
Qiang
Q
Zhang
Courtney G
CG
Woods
Yanyan
Y
Chen
Peng
P
Xue
Jian
J
Dong
Erik J
EJ
Tokar
Yuanyuan
Y
Xu
Yongyong
Y
Hou
Jingqi
J
Fu
Kathy
K
Yarborough
Aiping
A
Wang
Weidong
W
Qu
Michael P
MP
Waalkes
Melvin E
ME
Andersen
Jingbo
J
Pi
D000970:Antineoplastic Agents / Q000494:pharmacology; D061745:Antioxidant Response Elements; D000077237:Arsenic Trioxide; D001152:Arsenicals / Q000494:pharmacology; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy* / Q000473:pathology; D002454:Cell Differentiation; D045744:Cell Line, Tumor / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004317:Doxorubicin / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D005047:Etoposide / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D055785:Gene Knockdown Techniques; D005721:Glutamate-Cysteine Ligase / Q000235:genetics / Q000378:metabolism; D051547:Heme Oxygenase-1 / Q000235:genetics / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D000072019:Kelch-Like ECH-Associated Protein 1; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000473:pathology; D008954:Models, Biological; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000235:genetics / Q000378:metabolism; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism*; D014411:Neoplastic Stem Cells / Q000378:metabolism; D010087:Oxides / Q000494:pharmacology; D047495:PPAR gamma / Q000819:agonists / Q000235:genetics / Q000378:metabolism*; D000090063:Proto-Oncogene Mas; D034622:RNA Interference; D000077154:Rosiglitazone; D045162:Thiazolidinediones / Q000494:pharmacology
D000970:Antineoplastic Agents; D001152:Arsenicals; D047908:Intracellular Signaling Peptides and Proteins; C431364:KEAP1 protein, human; D000072019:Kelch-Like ECH-Associated Protein 1; C000715470:MAS1 protein, human; D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; D010087:Oxides; D047495:PPAR gamma; D000090063:Proto-Oncogene Mas; D045162:Thiazolidinediones; D000077154:Rosiglitazone; D005047:Etoposide; D004317:Doxorubicin; C496541:HMOX1 protein, human; D051547:Heme Oxygenase-1; D016660:NAD(P)H Dehydrogenase (Quinone); C447479:NQO1 protein, human; C546365:GCLM protein, human; D005721:Glutamate-Cysteine Ligase; D000077237:Arsenic Trioxide