title: Cytochrome P450 2A13 mediates the neoplastic transformation of human bronchial epithelial cells at a low concentration of aflatoxin B1.
abstract: Cytochrome P450 2A13 (CYP2A13), mainly expressed in human respiratory tract, is highly efficient in the metabolic activation of aflatoxin (AF) B1 (AFB1) and is assumed to play a role in human lung tumorigenesis in airborne AFB1 exposure. To validate the assumption, we exposed human bronchial epithelial (BEAS-2B) cells stably expressing CYP2A13 (B-2A13), CYP1A2 (B-1A2) and CYP2A6 (B-2A6) to 0.1-10 nM AFB1 for 30-50 passages. B-2A13 cells showed increased sensitivity to 0.1 nM AFB1-induced neoplastic transformation and the formation of tumors in nude mice were observed at passage 30 (P30) while it occurred at P50 B-1A2 cells. B-2A6, similar to vector control, showed no neoplastic transformation in this condition. Additionally, AFB1-DNA adducts and 8-OHdG significantly increased in transformed P40 B-2A13, in parallel with the upregulation of p-ATR, p-BRCA1, Mre11, Rad50 and Rad51. However, the apoptosis of P40 cells was near normal, while the expression of Bax, C-Caspase 3 and C-PARP increased passage-dependently. Inhibition of ATR (ATR siRNA or NU6027) reversely increased the apoptosis of P40 B-2A13 cells in parallel with the upregulation of Bax, C-Caspase 3 and C-PARP, suggesting that ATR plays an important role in maintaining cell survival via antiapoptosis. Additionally, activation of ATR was necessary to neoplastic transformation since blockage of ATR in P40 cells inhibited DNA damage repair response and anchorage-independent growth. Our data demonstrated that CYP2A13 played a critical role in AFB1-induced neoplastic transformation. ATR-mediated the dysfunction of apoptosis and DNA damage repair might be involved. These results help establish a linkage between airborne AFB1 and human respiratory carcinoma.
authors.affiliation: Key Lab of Modern Toxicology of Ministry of Education, School of Public Health, Nanjing Medical University, Nanjing, People's Republic of China; State Key Lab of Reproductive Medicine, Institute of Toxicology, Nanjing Medical University, Nanjing, People's Republic of China.
authors.forename: Zhan
authors.initials: Z
authors.lastname: Zhang
authors.forename: Huiyuan
authors.initials: H
authors.lastname: Lu
authors.forename: Fei
authors.initials: F
authors.lastname: Huan
authors.forename: Cromie
authors.initials: C
authors.lastname: Meghan
authors.forename: Xuejiao
authors.initials: X
authors.lastname: Yang
authors.forename: Yun
authors.initials: Y
authors.lastname: Wang
authors.forename: Xichen
authors.initials: X
authors.lastname: Wang
authors.forename: Xinru
authors.initials: X
authors.lastname: Wang
authors.forename: Shou-Lin
authors.initials: SL
authors.lastname: Wang
mesh_terms: D016604:Aflatoxin B1 / Q000493:pharmacokinetics / Q000633:toxicity*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics* / Q000378:metabolism; D064007:Ataxia Telangiectasia Mutated Proteins / Q000235:genetics; D001980:Bronchi / Q000187:drug effects* / Q000201:enzymology* / Q000473:pathology; D053148:Caspase 3 / Q000235:genetics; D002460:Cell Line; D002465:Cell Movement / Q000187:drug effects / Q000235:genetics; D002471:Cell Transformation, Neoplastic / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics; D018736:DNA Adducts / Q000187:drug effects; D004260:DNA Repair; D004847:Epithelial Cells / Q000187:drug effects / Q000201:enzymology / Q000473:pathology; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D011065:Poly(ADP-ribose) Polymerases / Q000235:genetics; D015854:Up-Regulation / Q000187:drug effects; D051028:bcl-2-Associated X Protein / Q000235:genetics
chemical_list: D018736:DNA Adducts; D051028:bcl-2-Associated X Protein; D003577:Cytochrome P-450 Enzyme System; D016604:Aflatoxin B1; D001189:Aryl Hydrocarbon Hydroxylases; C414206:CYP2A13 protein, human; D011065:Poly(ADP-ribose) Polymerases; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D053148:Caspase 3
keywords: BEAS-2B cells; aflatoxin B1; ataxia telangiectasia and Rad3-related pathway; cytochrome P450 2A13; neoplastic transformation