title: NOS2 enhances KRAS-induced lung carcinogenesis, inflammation and microRNA-21 expression.
abstract: Mutant KRAS in lung cancers induces molecular pathways that regulate cellular proliferation, survival and inflammation, which enhance tumorigenesis. Inducible nitric oxide synthase (NOS2) upregulation and sustained nitric oxide generation are induced during the inflammatory response and correlate positively with lung tumorigenesis. To explore the mechanistic contribution of NOS2 to KRAS-induced lung tumorigenesis and inflammation, we used a genetic strategy of crossing NOS2 knockout (NOS2KO) C57BL6 inbred mice with a KRAS(G12D)-driven mouse lung cancer model. KRAS(G12D);NOS2KO mice exhibited delayed lung tumorigenesis and a longer overall survival time compared to that of KRAS(G12D);NOS2WT (wild-type) controls. Correspondingly, tumors in KRAS(G12D);NOS2KO mice had reduced tumor cell proliferation in adenomas and carcinomas. NOS2 deficiency also led to markedly suppressed inflammatory response by attenuation of macrophage recruitment into alveoli and within tumor foci. In contrast, FOXP3+ regulatory T cells were increased in tumors from KRAS(G12D) ;NOS2KO mice. We further analyzed the expression of microRNA-21 (miR-21), an oncogenic noncoding RNA involved in oncogenic Ras signaling, by quantitative reverse-transcription polymerase chain reaction and in situ hybridization. Lung carcinomas dissected from KRAS(G12D);NOS2KO mice showed a significantly reduced miR-21 expression along with decreased tumor cell proliferation, suggesting that NOS2 deficiency could attenuate RAS signaling pathways that transactivate miR-21 expression. Therefore, deletion of NOS2 decreases lung tumor growth as well as inflammatory responses initiated by oncogenic KRAS, suggesting that both KRAS and NOS2 cooperate in driving lung tumorigenesis and inflammation. Inhibition of NOS2 may have a therapeutic value in lung cancers with oncogenic KRAS mutations.
authors.affiliation: Laboratory of Human Carcinogenesis, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Okayama
authors.forename: Motonobu
authors.initials: M
authors.lastname: Saito
authors.forename: Naohide
authors.initials: N
authors.lastname: Oue
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Weiss
authors.forename: Jimmy
authors.initials: J
authors.lastname: Stauffer
authors.forename: Seiichi
authors.initials: S
authors.lastname: Takenoshita
authors.forename: Robert H
authors.initials: RH
authors.lastname: Wiltrout
authors.forename: S Perwez
authors.initials: SP
authors.lastname: Hussain
authors.forename: Curtis C
authors.initials: CC
authors.lastname: Harris
mesh_terms: D000818:Animals; D048708:Cell Growth Processes / Q000502:physiology; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000378:metabolism; D007249:Inflammation / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D008264:Macrophages / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D035683:MicroRNAs / Q000096:biosynthesis* / Q000235:genetics; D009154:Mutation / Q000235:genetics; D052247:Nitric Oxide Synthase Type II / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics / Q000378:metabolism*; D011650:Pulmonary Alveoli / Q000378:metabolism / Q000473:pathology; D050378:T-Lymphocytes, Regulatory / Q000378:metabolism
chemical_list: D051858:Forkhead Transcription Factors; C498833:Foxp3 protein, mouse; C531950:MIRN21 microRNA, mouse; D035683:MicroRNAs; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; C495971:Hras protein, mouse; D016283:Proto-Oncogene Proteins p21(ras)