Lung tumorigenesis promoted by anti-apoptotic effects of cotinine, a nicotine metabolite through activation of PI3K/Akt pathway.
We previously found that genetic polymorphism in cytochrome P450 2A6 (CYP2A6) is one of the potential determinants of tobacco-related lung cancer risk. It has been reported that the plasma concentration of cotinine, a major metabolite of nicotine, in carriers of wild-type alleles of CYP2A6 is considerably higher than that in carriers of null or reduced-function alleles of CYP2A6, raising the possibility that cotinine plays an important role in the development of lung cancer. As a novel mechanism of lung tumorigenesis mediated by CYP2A6, we investigated the effects of cotinine on the suppression of apoptosis and promotion of lung tumor growth. In human lung adenocarcinoma A549 cells, cotinine inhibited doxorubicin-induced cell death by suppressing caspase-mediated apoptosis. Enhanced phosphorylation of Akt, a key factor responsible for cell survival and inhibition of apoptosis, was detected after cotinine treatment. These data suggest that cotinine suppresses caspase-mediated apoptosis induced by doxorubicin through activation of the PI3K/Akt pathway. Furthermore, we clarified that cotinine significantly facilitated tumor growth in the Lewis lung cancer model and accelerated development of lung adenomas induced by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in A/J mice. We herein propose that cotinine induces tumor promotion by inhibiting apoptosis and enhancing cellular proliferation, thus underlining the importance of CYP2A6 in tobacco-related lung tumorigenesis.
Laboratory of Drug Metabolism, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan. nakada.tomohisa@ms.mt-pharm.co.jp
Tomohisa
T
Nakada
Kazuma
K
Kiyotani
Shunsuke
S
Iwano
Takahiko
T
Uno
Masanao
M
Yokohira
Keiko
K
Yamakawa
Masaki
M
Fujieda
Tetsuya
T
Saito
Hiroshi
H
Yamazaki
Katsumi
K
Imaida
Tetsuya
T
Kamataki
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics / Q000378:metabolism; D053148:Caspase 3 / Q000235:genetics / Q000378:metabolism; D053179:Caspase 7 / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism; D003367:Cotinine / Q000633:toxicity*; D065637:Cytochrome P-450 CYP2A6; D005260:Female; D006801:Humans; D008168:Lung / Q000166:cytology / Q000187:drug effects* / Q000473:pathology; D008175:Lung Neoplasms / Q000235:genetics / Q000473:pathology*; D051379:Mice; D008805:Mice, Inbred A; D008810:Mice, Inbred C57BL; D009538:Nicotine / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*
D009538:Nicotine; D001189:Aryl Hydrocarbon Hydroxylases; C585710:CYP2A6 protein, human; D065637:Cytochrome P-450 CYP2A6; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; C505407:CASP3 protein, human; C505520:CASP7 protein, human; D053148:Caspase 3; D053179:Caspase 7; D003367:Cotinine