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We have studied the occurrence and persistence of DNA damage in the hepatic and pulmonary tissues of fetal, newborn and adult CD1 mice exposed to selected doses of benzo[a]pyrene (BP) by utilizing the alkaline elution technique. Firstly 12-, 15- and 18-day pregnant and 1-, 7- and 82 to 85-day-old mice were treated i.p. with 10 mg/kg BP and the DNA fragmentation evaluated 4 h later. This approach indicated that, among the ages considered, 15-day-old fetuses were the most sensitive to BP genotoxicity. Therefore we concentrated on this intrauterine stage and evaluated the role of the maternal and fetal environment on the induction and the kinetics of disappearance of DNA damage by BP. BP at the dose levels of 0, 2 and 10 mg/kg was injected i.p. into pregnant females or directly into single fetuses and the fetal livers and lungs recovered 2, 4, 24 and 48 h later. According to the above protocol other 12-day-pregnant mice were treated i.p. with 500 mg/kg arochlor and their 15-day-old fetuses directly injected with the same doses of BP. The results showed that the maximum DNA damage is present at 4 h following BP treatment and it almost disappeared at 48 h irrespective of the route of BP administration. However, the decrease was not uniform and while at 48 h the lesion reached the control level in the liver, it remained sightly higher in the lung. The effects were markedly magnified in the arochlor-induced groups where the intrafetal injection of BP caused an average 2-fold increase and an earlier appearance of DNA damage in both liver and lung compared with uninduced animals. The amplified BP activity induced by arochlor was particularly evident in the lung where at 48 h there was still a significant amount of DNA damage. Since the lung is a preferential site of transplacental carcinogenic effects in CD1 mice, our results favor the conclusion that a correlation exists between DNA damage and tumor induction in the fetuses of this mouse strain. [ABSTRACT FROM PUBLISHER]

The time course of DNA damaged induced by administration of benzidine, 1- and 2-naphthylamine or dimethylnaphthylamine has been evaluated using an alkaline elution technique. The organs damaged by the active ultimate metabolites, produced in mice treated with aromatic amines, appear to be, in decreasing order of susceptibility, liver, kidney and lung. Single-stranded DNA breaks are still evident 12 h after a single administered dose of the compounds. A direct doseresponse relationship has been obtained using increasing concentrations of aromatic amines. [ABSTRACT FROM PUBLISHER]

Shorter telomere length (TL) in peripheral blood lymphocytes (PBLs) is predictive of lung cancer risk. Polycyclic aromatic hydrocarbons (PAHs) are established lung carcinogens that cause chromosome instability. Whether PAH exposure and its molecular effects are linked with shorter TL has never been evaluated. In the present study, we investigated the effect of chronic exposure to PAHs on TL measured in PBLs of Polish male non-current smoking cokeoven workers and matched controls. PAH exposure and molecular effects were characterized using measures of internal dose (urinary 1-pyrenol), effective dose [anti-benzo[a]pyrene diolepoxide (anti-BPDE)-DNA adduct], genetic instability (micronuclei, MN) and DNA methylation [p53 promoter and Alu and long interspersed nuclear element-1 (LINE-1) repetitive elements, as surrogate measures of global methylation] in PBLs. TL was measured by real-time polymerase chain reaction. Cokeoven workers were heavily exposed to PAHs (79% exceeded the urinary 1-pyrenol biological exposure index) and exhibited lower TL (P = 0.038) than controls, as well as higher levels of genetic and chromosomal alterations [i.e. anti-BPDE-DNA adduct and MN (P < 0.0001)] and epigenetic changes [i.e. p53 gene-specific promoter and global methylation (P

The frequency of micronuclei (MN) in peripheral blood lymphocytes (PBL) is extensively used as a biomarker of chromosomal damage and genome stability in human populations. Much theoretical evidence has been accumulated supporting the causal role of MN induction in cancer development, although prospective cohort studies are needed to validate MN as a cancer risk biomarker. A total of 6718 subjects from of 10 countries, screened in 20 laboratories for MN frequency between 1980 and 2002 in ad hoc studies or routine cytogenetic surveillance, were selected from the database of the HUman MicroNucleus (HUMN) international collaborative project and followed up for cancer incidence or mortality. To standardize for the inter-laboratory variability subjects were classified according to the percentiles of MN distribution within each laboratory as low, medium or high frequency. A significant increase of all cancers incidence was found for subjects in the groups with medium (RR=1.84; 95% CI: 1.28-2.66) and high MN frequency (RR=1.53; 1.04-2.25). The same groups also showed a decreased cancer-free survival, i.e. P=0.001 and P=0.025, respectively. This association was present in all national cohorts and for all major cancer sites, especially urogenital (RR=2.80; 1.17-6.73) and gastro-intestinal cancers (RR=1.74; 1.01-4.71). The results from the present study provide preliminary evidence that MN frequency in PBL is a predictive biomarker of cancer risk within a population of healthy subjects. The current wide-spread use of the MN assay provides a valuable opportunity to apply this assay in the planning and validation of cancer surveillance and prevention programs.

We have compared liver, kidney and colon DNA damage, as single strand breaks, in mice with different strain-dependent susceptibility to the colon-specific carcinogen 1,2-dimethylhydrazine (DMH). The mouse strains studied were: AKR/J, DBA2 totally resistant; CD1, C57BL/6N moderately susceptible; SWR/J very susceptible to DMH-induced carcinogenesis. DNA breaks were estimated from the elution rate constant (K) according to the alkaline elution technique. At 4 h after carcinogen administration a substantial and comparable DNA damage was found in liver and kidney in all the strains examined. The DNA fragmentation index, however, reached a maximum value at 2 h after treatment in the liver of the most susceptible strain (SWR/J). About 50% of the liver DNA damage detected in all five strains 4 h after DMH administration persisted at 24 h after treatment and was totally repaired at 72 h. Kidney DNA damage decreased in 48 h toward the range of control values. In colon epithelial cells (the carcinogen target tissue) 2 and 4 h after DMH administration the amount of DNA single strand breaks was correlatable with the strain sensitivity to the carcinogen. In the time interval studied (2-72 h after DMH administration) the decrease of colon DNA damage was linear in the resistant strains. In contrast, in the more susceptible strain (SWR/J), the amount of DNA breaks remained high up to 24 h after treatment and returned to background level at 72 h.

We have tried to establish a correlation between the carcinogenic potency of four methylating compounds and their specific target sites in chromatin. We have therefore compared the nuclear metabolism of two relatively weak carcinogens radioactively labelled: dimethyl sulphate (DMS) and methyl methanesulphonate (MMS), and two potent carcinogens: N-methyl-N-nitrosourea (MNU) and N-methyl-N'-nitro-N-nitrosoguanosine (MNNG) in cultured primary hepatocytes and the V79 Chinese hamster cell line. Cysteine (when present), and to a lesser extent histidine, were methylated by MMS and DMS not only in the total acid-soluble nuclear protein (H) but also in purified histones H1 and H3. These compounds had the same effect not only on total non-histone nuclear protein (NH) but also on purified HMG1 and HMG2 (nuclear non-histone proteins with high electrophoretic mobility). Traces of methylarginine and methylated lysine could be detected in all samples. MNU and MNNG predominantly methylated lysine and arginine residues, the former being found mostly in acid soluble, the latter in non-histone nuclear protein. Methylated cysteine and histidine were present in trace amounts. Our preliminary data suggest specific amino acid methylation at the nuclear protein level for carcinogens with different potencies, similar to what has been found for DNA bases.