TRANSPLACENTAL TRANSFER OF GENOTOXINS AND TRANSPLACENTAL CARCINOGENESIS

A number of chemical compounds induce cancer in the offspring of animals treated with these compounds. The fetus is sensitive to the toxic and teratogenic effects of chemicals in the early embryonic stages, whereas it is sensitive to carcinogenic effects during late fetal stages. Carcinogens may be direct acting or may require metabolic oxidation such as those in tobacco smoke. Activation can occur in utero. Animal experiments indicate that tumors can be initiated in utero, commonly by activation of cellular proto-oncogenes, and that promotion can occur after birth by postnatal treatment with tumor promoters. This may have important implications for humans. The initial peak of cancer incidence during the first 5 years of life may be due to prenatal exposure of either parent to mutagens, but the role of paternal exposure in relation to childhood cancer is controversial. There is an increased risk of cancer in children whose fathers work in, heavy industry or whose mothers work in medical or dental services. The exact etiological agents have not been unequivocally identified. Information on human transplacental exposure to carcinogens and genotoxins is limited and based on measurement of maternal plasma concentrations or analysis of cord blood. Transplacental transfer of carcinogens in smoke and smoke-related damage to fetal tissue have been demonstrated. The mycotoxin aflatoxin B1 or its metabolites have been detected in cord blood, as have metabolites of pesticides and polychlorinated biphenyls. New biomarkers may provide important information on the transplacental transfer of genotoxic compounds. Recent developments in the field of molecular biology such as polymerase chain reaction may disclose relevant biological changes occurring in utero as a consequence of exposure to environmental compounds.