Carcinogenesis, Vol 18, 1701-1707, Copyright © 1997 by Oxford University Press
KL Dobo, DA Eastmond and AJ Grosovsky
The induction of loss of heterozygosity (LOH) by the environmental
carcinogen N-nitrosodimethylamine (NDMA), and the factors that influence
the recovery of LOH mutations were studied in two directly related human
lymphoblastoid cell lines, AHH-1 (h2E1.v2) and MCL-5. Initially, the
NDMA-induced mutation frequency at the heterozygous tk locus in AHH-1 cells
was observed to be 5-fold higher in AHH-1 compared with MCL-5. Molecular
analysis of NDMA-induced TK- mutants indicated that the induced mutant
fraction attributable to small intragenic mutations was similar in both
cell lines. However, the induced mutant fraction, because of LOH, was
18-fold greater in AHH-1. In addition, LOH mutations were more extensive
among TK- mutants derived from AHH-1 cells. We hypothesized that the
increased recovery of large LOH mutations in AHH-1 cells could be
attributable to reduced apoptotic capacity, as it has been reported that
AHH-1 cells carry a heterozygous mutation in the p53 locus, whereas MCL-5
cells are homozygous wild- type. Analysis of the kinetics of apoptosis
showed that the apoptotic response of the AHH-1 cell line was diminished
and delayed compared with MCL-5. Based on the analyses presented here, and
several recent reports, it is suggested that the recovery of LOH mutations
in p53 deficient cell lines is affected not only by abnormalities in
cellular apoptotic response, but also involves a number of p53-mediated
responses to DNA damage.
ARTICLES
The influence of cellular apoptotic capacity on N-nitrosodimethylamine- induced loss of heterozygosity mutations in human cells
Environmental Toxicology Graduate Program, University of California, Riverside 92521, USA.
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