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Early Age at Smoking Initiation and Tobacco Carcinogen DNA Damage in the Lung

Authors:
John Wiencke at UCSF University of California, San Francisco
John Wiencke
Sally W Thurston
Sally W Thurston
Sally W Thurston
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Karl T Kelsey at Brown University
Karl T Kelsey
Andrea Varkonyi
Andrea Varkonyi
Andrea Varkonyi
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Abstract

Background: DNA adducts formed as a consequence of exposure to tobacco smoke may be involved in carcinogenesis, and their presence may indicate a high risk of lung cancer. To determine whether DNA adducts can be used as a "dosimeter" for cancer risk, we measured the adduct levels in nontumorous lung tissue and blood mononuclear cells from patients with lung cancer, and we collected data from the patients on their history of smoking. Methods: We used the 32P-postlabeling assay to measure aromatic hydrophobic DNA adducts in nontumorous lung tissue from 143 patients and in blood mononuclear cells from 54 of these patients. From the smoking histories, we identified exposure variables associated with increased DNA adduct levels by use of multivariate analyses with negative binomial regression models. RESULTS/ CONCLUSIONS: We found statistically significant interactions for variables of current and former smoking and for other smoking variables (e.g., pack-years [number of packs smoked per day x years of smoking] or years smoked), indicating that the impact of smoking variables on DNA adduct levels may be different in current and former smokers. Consequently, our analyses indicate that models for current and former smokers should be considered separately. In current smokers, recent smoking intensity (cigarettes smoked per day) was the most important variable. In former smokers, age at smoking initiation was inversely associated with DNA adduct levels. A highly statistically significant correlation (r=.77 [Spearman's correlation]; two sided P<.001) was observed between DNA adduct levels in blood mononuclear cells and lung tissue. Implications: Our results in former smokers suggest that smoking during adolescence may produce physiologic changes that lead to increased DNA adduct persistence or that young smokers may be markedly susceptible to DNA adduct formation and have higher adduct burdens after they quit smoking than those who started smoking later in life.
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Re: Early Age at Smoking
Initiation and Tobacco
Carcinogen DNA Damage in
the Lung
It is clear from the analysis by
Wiencke et al. (1) that an earlier age at
smoking initiation is associated with a
greater frequency of DNA damage. It
should also be clear that children of par-
ents who smoke are more likely to begin
smoking at a younger age than are chil-
dren of nonsmoking parents. This con-
clusion suggests the possibility that a
portion of the susceptibility to DNA ad-
duct formation observed in those with
the youngest age at initiation of smoking
might have been inherited from their
parents’ damaged DNA. Should not the
parents’ smoking history be included as
one of the factors in the multivariate
analysis?
JOHN H. GLASER
REFERENCE
(1) Wiencke JK, Thurston SW, Kelsey KT,
Varkonyi A, Wain JC, Mark EJ, et al. Early
age at smoking initiation and tobacco carcino-
gen DNA damage in the lung. J Natl Cancer
Inst 1999;91:614–9.
NOTE
Correspondence to: John H. Glaser, 4 Wood-
park Circle, Lexington, MA 02421 (e-mail:
GlaserJ@polaroid.com).
RESPONSE
Dr. Glaser raises the complex and
thorny issue of the role of parental
smoking in lung cancer risk among their
offspring and suggests the possibility
that genetic transmission of “tobacco-
damaged DNA” through the germline
may play a part in this risk. It is clear
that children whose parents smoke are
more likely to become regular smokers
themselves. Recent studies show that the
negative impact of parental smoking
may operate long before the teen years,
so that preventing experimentation and
initiation of smoking requires interven-
tion throughout childhood.
Leaving aside the possible infrequent
occurrence of constitutional (germline)
lung cancer genes, the association be-
tween smoking and lung cancer within
families is likely due to acquired smok-
ing behaviors that are shared by family
members rather than to germline
DNA damage. The strong evidence link-
ing maternal smoking with low birth
weight and respiratory problems, includ-
ing SIDs (sudden infant deaths), is
evidence of in utero toxicity from expo-
sure to tobacco smoke constituents that
is not heritable. In addition, transplacen-
tal transmission of potent tobacco
carcinogens has been documented.
For example, the urine of infants born
to smoking mothers has been shown
to contain metabolites of tobacco-
specific nitrosamines (1). Consequently,
among the most sensitive indicators
of the possible influence of parental
smoking in familial cancer is the occur-
rence of cancers in children whose
parents smoke. Despite intensive
study, maternal smoking has not been
established as a risk factor for childhood
cancers (2–4). On the other hand,
chromosomal abnormalities (5) and
DNA damage in sperm have been docu-
mented among smokers, and increased
risks for certain childhood cancers have
been associated with paternal smoking
(6). Further study is needed, however,
and it will remain a very difficult prob-
lem to determine whether associations
are due to germline transmission of
smoking-induced mutations rather than
to in utero or postnatal exposures to to-
bacco smoke. The question of lung can-
cer and parental exposure, because of
the later age of onset, is even more com-
plicated.
In our study of ex-smokers with lung
cancer (7), we reported that the DNA
damage levels in lungs were greater in
patients who reported an early age of
smoking initiation. We did not attempt
to factor in parental smoking, nor do we
think it would be informative, in part for
the reasons cited above, but also for the
practical reason that our patients, whose
mean age was 66 years, would not be
able to consistently provide their par-
ents’ smoking habits before their own
birth. Most of the parents of our case
subjects were deceased or unable to pro-
vide first-hand histories. The studies al-
luded to above on childhood cancers do
not suffer from these limitations. Hence,
although more research is needed on the
mechanisms of tobacco damage in germ
cells, we recognize that the dominant in-
fluence of parental smoking on lung
cancer occurrence is in the uptake of the
smoking habit. In addressing the respon-
sibility of parents, the potential for
blame and guilt must be minimized and
each of us should be reminded of the
strong addictive properties of nicotine.
JOHN K. WIENCKE
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(7) Wiencke JK, Thurston SW, Kelsey KT,
Varkonyi A, Wain JC, Mark EJ, et al. Early
age at smoking initiation and tobacco carcino-
gen DNA damage in the lung. J Natl Cancer
Inst 1999;91:614–9.
NOTE
Correspondence to: John K. Wiencke, Ph.D.,
Department of Epidemiology and Biostatistics,
School of Medicine, University of California San
Francisco, 500 Parnassus Ave., MU-W 420, San
Francisco, CA 94143-0560 (e-mail: wiencke@
itsa.ucsf.edu).
Journal of the National Cancer Institute, Vol. 91, No. 16, August 18, 1999 CORRESPONDENCE 1423
by guest on April 13, 2012http://jnci.oxfordjournals.org/Downloaded from
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  • MECH AGEING DEV
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32P-Postlabelling analysis of DNA from human tissues
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  • Aug 1992
  • MUTAT RES-FUND MOL M
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Article
  • Sep 1992
The quantitation of adducts of genotoxins with DNA is probably one of the best indicators of genetic damage due to exposure to toxins or carcinogens. It is generally believed that such adducts can lead to mutations, which in turn can trigger the initiation of the carcinogenic process. DNA adducts have been quantitated in white blood cells and in various tissues of smokers, persons in certain high-exposure occupations, and persons consuming foods contaminated with certain carcinogens. The feasibility of this approach for biochemical epidemiologic studies has been demonstrated using methods such as 32P-postlabeling, enzyme-linked immunosorbent assay, and synchronous fluorescence spectrophotometry. Relatively large interindividual differences in DNA adducts have been observed in both exposed and nonexposed persons. As a result, there are only a few studies in which clear quantitative and qualitative differences between these two groups have been observed. In addition, it appears that in some studies the 32P-postlabeling method does not detect the presence of the polycyclic aromatic hydrocarbon DNA adducts that are detectable by immunoassays. More extensive studies in additional populations at risk should shed further light on the utility of DNA adduct analysis in biochemical monitoring, especially if further refinements in methodology would result in increased sensitivity and specificity.
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Formation and persistence of benzo[a]pyrene-DNA adducts in different tissues of C57BL/10 and DBA/2 mice
Article
  • Oct 1991
Synchronous fluorescence spectrophotometry (SFS) developed to study benzo[a]pyrene-7,8-diol-9,10-epoxide (BPDE)--DNA adducts was used to measure the formation and disappearance of DNA adducts in the lung, liver, kidney, spleen and small intestine of genetically responsive C57BL/10 (B10) and nonresponsive DBA/2 (D2) mice. After single stomach intubation of 100 mg/kg of benzo[a]pyrene (B[a]P) in both strains, binding of BPDE to DNA reached a peak 48 h after treatment. However, the levels of binding in the lung, liver, kidney and spleen were higher in D2 than in B10 mice. In contrast to this, in the small intestine the higher level of BPDE binding was found in B10 mice and reached its maximum 24 h earlier. Thereafter a very rapid drop in the level of BPDE--DNA adducts to a value of approximately 50% after 48 h was observed in this tissue. In the other tissues of the B10 mice the rate of adducts removal was slower, but by 14 days after treatment 90-100% of adducts were removed. In the D2 mice up to the 4th day after treatment the rates of removal of the BPDE--DNA adducts were similar to that of the B10 mice. Thereafter the level of bound hydrocarbon decreased at a slower rate. During the whole period after B[a]P treatment distinct differences between organs in the amount of BPDE--DNA adducts were observed. In D2 mice the highest level of binding was found in the spleen followed by the lung, kidney, liver and small intestine. In B10 mice the highest level of binding was observed in the DNA of small intestine. The data suggest that the decreased rate of B[a]P metabolism in D2 mice may be at least in some tissues the reason of higher binding of BPDE--DNA adducts in comparison with B10 mice.
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Polycyclic aromatic hydrocarbon-DNA adducts in lung tissue from lung cancer patients
Article
  • Oct 1990
In an attempt to probe for polycyclic aromatic hydrocarbon (PAH)-DNA adducts in human subjects resulting from smoking (or other chronic environmental exposure), lung tissue and lung tumours were obtained from patients hospitalized for lung cancer. DNA was isolated from the tissue samples and examined both in an ELISA using a polyclonal antibody against (+/-)trans-7,8-dihydroxy-anti-9,10-epoxy-7,8,9,10- tetrahydrobenzo[a]pyrene (BPDE)-DNA as well as by the nuclease P1-mediated modification of the 32P-post-labelling technique. The ELISA results showed BPDE-DNA antigenicity in lung DNA from 6 out of 21 patients, and adduct levels ranged from 2 to 134 adducts per 10(8) nucleotides. For all 21 patients, the autoradiographs of chromatograms of 32P-postlabelled digests of DNA from non-tumorous lung tissue showed a strong diagonal radioactive zone (DRZ). This DRZ was generally absent in tumorous tissue. DNA samples that were positive in the ELISA contained a dominant spot within the DRZ that co-chromatographed with the major BPDE-DNA adduct (BPDE-dG). The quantities of the BPDE-dG spots ranged from 2.1 to 42 adducts in 10(9) nucleotides. These values were lower than the levels found in the ELISA but correlated well with the ELISA results (Kendall W = 0.97; P = 0.00). The levels of the DRZ adducts ranged from 1.9 to 34 adducts in 10(8) nucleotides. Correlations between smoking and DNA adduct levels were poor because of the small number of current smokers (n = 13). However, smokers of filter cigarettes had significantly lower DNA adduct levels compared with smokers of cigarettes without a filter (P = 0.02 by Fischer's exact test).
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Linear relationship between DNA adducts in human lung and cigarette smoking
Article
  • Feb 1990
Human lung and bladder DNA has been isolated and purified from either surgical or autopsy specimens. Smoking history details were obtained from patients or their close relatives. Each DNA sample was investigated using the nuclease P1 digestion modification of the 32P-postlabelling procedure. Data are presented for 48 lung and 19 bladder specimens. The samples were subdivided into three groups for data analysis, viz. smokers, former smokers and nonsmokers. The mean adduct levels (adducts per 10(8) nucleotides) in lung samples were: [see text] The chromatographic pattern of bladder DNA adducts for smokers was similar to that for smokers' lung DNA, although less intense. Adduct levels in former smokers tended to be lower than in smokers, although loss of adducts appeared to require several years after cessation of smoking. These findings support a link between DNA adduct levels and cigarette smoking, for both the lung and the bladder. For the former tissue there was a strong linear correlation between adduct levels and the number of cigarettes smoked.
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