Altered benzo[a]pyrene metabolism in C3H/10T1/2 cells transformed by aflatoxin B1 or 3-methylcholanthrene.
C3H/10T1/2 clone 8 (10T1/2) cells possess Phase I and Phase II xenobiotic metabolizing enzymes associated with the metabolism of polycyclic aromatic hydrocarbons to activated or detoxified species. We compared the metabolism of benzo[a]pyrene (BaP) by these cells to an aflatoxin B1 (AFB1)-transformed line (7SA) and a 3-methylcholanthrene (3-MC)-transformed line (MCA) isolated from carcinogen-treated 10T1/2 cells. Relative to 10T1/2 cells, basal levels of cytochrome P450-mediated aryl hydrocarbon hydroxylase (AHH) were significantly depressed in 7SA cells by about 30%. The inducibility of AHH by BaP treatment was depressed by 30-70% in MCA and 7SA cells over a 36-hr time course. 10T1/2 and MCA cells accumulated similar intracellular amounts of 3-OH-BaP by 12 and 24 hr, respectively; in contrast the accumulation of 3-OH-BaP in 7SA cells was 70% lower. During 36 hr of BaP treatment, total BaP-DNA adduct levels formed in 7SA and MCA cells, determined by 32P-postlabeling analysis, were 90 and 83% lower, respectively, than those found in 10T1/2 cells. These differences in response to BaP treatment were not related to cellular differences in the uptake or efflux of BaP. Relative to 10T1/2 or MCA cells, 7SA cells were found to have at least a twofold increase in UDP-glucuronyltransferase activity, which correlated with the lower intracellular accumulation of 3-OH-BaP and enhanced formation of extracellular polar metabolites. MCA cells had an almost twofold increase in glutathione S-transferase activity relative to parental 10T1/2 cells but produced lower levels of extracellular polar metabolites. These results demonstrate an association between chemical transformation of 10T1/2 cells and altered xenobiotic metabolism. This system may provide an in vitro model for examining the molecular events responsible for the biochemically altered phenotype of the malignantly transformed cell.
Faletto
M B
MB
Grace Cancer Drug Center, Roswell Park Memorial Institute, Buffalo, New York 14263.
Maccubbin
A E
AE
Ersing
N
N
Kouli
F
F
Vangalio
J A
JA
Gurtoo
H L
HL
D016604:Aflatoxin B1; D000348:Aflatoxins / Q000633:toxicity*; D001189:Aryl Hydrocarbon Hydroxylases / Q000378:metabolism; D001564:Benzo(a)pyrene / Q000378:metabolism*; D002453:Cell Cycle / Q000187:drug effects; D002460:Cell Line; D002471:Cell Transformation, Neoplastic / Q000139:chemically induced / Q000235:genetics / Q000378:metabolism*; D004247:DNA / Q000378:metabolism; D018736:DNA Adducts; D014453:Glucuronosyltransferase / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D008658:Inactivation, Metabolic / Q000502:physiology; D008748:Methylcholanthrene / Q000633:toxicity*; D005723:gamma-Glutamyltransferase / Q000378:metabolism
D000348:Aflatoxins; D018736:DNA Adducts; C056612:benzo(a)pyrene-DNA adduct; D001564:Benzo(a)pyrene; D008748:Methylcholanthrene; D004247:DNA; D016604:Aflatoxin B1; D001189:Aryl Hydrocarbon Hydroxylases; D005723:gamma-Glutamyltransferase; D014453:Glucuronosyltransferase; D005982:Glutathione Transferase