An effective strategy for increasing the radiosensitivity of Human lung Cancer cells by blocking Nrf2-dependent antioxidant responses.
Radiotherapy and chemotherapeutic agents can effectively induce apoptosis through generation of reactive oxygen species (ROS). Cancer cells frequently express high levels of ROS-scavenging enzymes, which confer resistance to ROS-mediated cell death. Keap1 (Kelch-like ECH-associated protein 1) sequesters and promotes the degradation of the antioxidant response element-binding transcription factor Nrf2 (nuclear factor erythroid-2-related factor 2). In non-small-cell lung cancer (NSCLC) cell lines and NSCLC patients, Keap1 is often present as a biallelic mutant that results in constitutive activation of Nrf2 function, which contributes to cytoprotection against oxidative stress and xenobiotics. To identify small molecules that inhibit antioxidant responses and increase apoptotic death after radiotherapy, we screened a chemical library containing 8000 synthetic compounds using a cell-based luciferase assay system. 4-(2-Cyclohexylethoxy)aniline (IM3829) inhibited the increase in Nrf2-binding activity and expression of the Nrf2 target genes induced by treatment with tertiary butylhydroquinone or radiation. Combined treatment with IM3829 and radiation significantly inhibited clonogenic survival of H1299, A549, and H460 lung cancer cells. IM3829 significantly increased ROS accumulation in irradiated cells compared with cells exposed to radiation alone and led to apoptotic cell death, as confirmed by caspase-3 and PARP cleavage. In mice bearing H1299 or A549 lung cancer xenografts, IM3829 together with radiation inhibited tumor growth more effectively than radiation alone. Our findings suggest that IM3829 could be a promising radiosensitizer in lung cancer patients, particularly those with high expression of Nrf2.
Department of Radiation Cancer Research, Korea Institute of Radiological & Medical Sciences, Seoul 139-706, Korea.
Saelooom
S
Lee
Min-Jin
MJ
Lim
Mi-Hyoung
MH
Kim
Chi-Ho
CH
Yu
Yeon-Sook
YS
Yun
Jiyeon
J
Ahn
Jie-Young
JY
Song
D000814:Aniline Compounds / Q000008:administration & dosage*; D000818:Animals; D061745:Antioxidant Response Elements / Q000187:drug effects*; D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis; D045744:Cell Line, Tumor / Q000528:radiation effects; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D005260:Female; D015870:Gene Expression; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D017930:Genes, Reporter; D051547:Heme Oxygenase-1 / Q000235:genetics / Q000378:metabolism; D006801:Humans; D006873:Hydroquinones / Q000494:pharmacology; D007274:Injections, Intraperitoneal; D049410:Luciferases, Renilla / Q000096:biosynthesis / Q000235:genetics; D008175:Lung Neoplasms / Q000532:radiotherapy*; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism*; D011836:Radiation Tolerance; D011838:Radiation-Sensitizing Agents / Q000008:administration & dosage*; D017382:Reactive Oxygen Species / Q000378:metabolism; D054852:Small Molecule Libraries; D023041:Xenograft Model Antitumor Assays
C576912:4-(2-cyclohexylethoxy)aniline; D000814:Aniline Compounds; D000975:Antioxidants; D006873:Hydroquinones; D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; D011838:Radiation-Sensitizing Agents; D017382:Reactive Oxygen Species; D054852:Small Molecule Libraries; C018855:2-tert-butylhydroquinone; D049410:Luciferases, Renilla; C496541:HMOX1 protein, human; D051547:Heme Oxygenase-1