Host determinants of DNA alkylation and DNA repair activity in human colorectal tissue: O-6-methylguanine levels are associated with GSTT1 genotype and O-6-alkylguanine-DNA alkyltransferase activity with CYP2D6 genotype
Ac. Povey et al., Host determinants of DNA alkylation and DNA repair activity in human colorectal tissue: O-6-methylguanine levels are associated with GSTT1 genotype and O-6-alkylguanine-DNA alkyltransferase activity with CYP2D6 genotype, MUT RES-GTE, 495(1-2), 2001, pp. 103-115
Citations number
68
Categorie Soggetti
Molecular Biology & Genetics
Journal title
MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS
There is increasing evidence that alkylating agent exposure may increase la
rge bowel cancer risk and factors which either alter such exposure or its e
ffects may modify risk. Hence, in a cross-sectional study of 78 patients wi
th colorectal. disease, we have examined whether (i) metabolic genotypes (G
STT1, GSTM1, CYP2D6, CYP2E1) are associated with O-6-methyldeoxyguanosine (
O-6-MedG) levels, O-6-alkylguanine-DNA alkyltransferase (ATase) activity or
K-ras mutations, and (ii) there was an association between ATase activity
and O-6-MedG levels. Patients with colon tumours and who were homozygous GS
TT1*2 genotype carriers were more likely than patients who expressed GSTT1
to have their DNA alkylated (83 versus 32%, P = 0.03) and to have higher O(
6)0-MedG levels (0.178 +/- 0.374 versus 0.016 +/- 0.023 mu mol O-6-MedG/mol
dG, P = 0.04) in normal, but not tumour, DNA. No such association was obse
rved between the GSTT1 genotype and the frequency of DNA alkylation or O-6-
MedG levels in patients with benign colon disease or rectal tumours. Patien
ts with colon tumours or benign colon disease who were CYP2D6-poor metaboli
sers had higher ATase activity in normal tissue than patients who were CYP2
D6 extensive metabolisers or CYP2D6 heterozygotes. Patients with the CYP2E1
Dra cd genotype were less likely to have a K-ras mutation: of 55 patients
with the wild-type CYP2E1 genotype (dd), 23 had K-ras mutations, whereas no
ne of the 7 individuals with cd genotype had a K-ras mutation (P = 0.04). N
o other associations were observed between GSTT1, GSTM1, CYP2D6 and CYP2E1
Pst genotypes and adduct levels, ATase activity or mutational status. O-6-M
edG levels were not associated with ATase activity in either normal or tumo
ur tissue. However, in 15 patients for whom both normal and tumour DNA cont
ained detectable O-6-MedG levels, there was a strong positive association b
etween the normal DNA/tumour DNA adduct ratio and the normal tissue/tumour
tissue ATase ratio (r(2) = 0.66, P = 0.001). These results indicate that ho
st factors can affect levels both of the biologically effective dose arisin
g from methylating agent exposure and of a susceptibility factor, the DNA r
epair phenotype. (C) 2001 Elsevier Science B.V. All rights reserved.