Childhood cancer has been increasing significantly over the past two decades in the United States, suggesting that environmental exposures may be playing a causative role. One such cause may be maternal smoking during pregnancy. Suspected carcinogens in cigarette smoke and environmental pollution include N-nitrosamines and polycyclic aromatic hydrocarbons, which may be several micrograms per exposure. Previously, we have shown that mouse progeny of mothers exposed to benzo[a]pyrene (B[a]P) during midpregnancy had abnormalities in their humoral and cell-mediated immune response. Immunodeficiency was detectable during gestation, at one week after birth and persisted for 18 months. Tumor incidences in progeny were eight to 10-fold higher than in controls. The present study compared frequencies of CD4+, CD8+, V gamma 2+, and V beta 8+ T cells in progeny following in utero exposure to B[a]P. The significant reduction in newborn CD4+CD8+, CD4+CD8+V beta 8+ thymocytes and CD4+ splenocytes from 1-week-old progeny, suggests that B[a]P induces abnormal changes in developing T cells. These early alterations may lead to postnatal T cell suppression, thus providing a more suitable environment for the growth of tumors later in life. These results suggest that developmental immunosuppression mediated by B[a]P may play a critical role in the relationship between maternal exposures and childhood carcinogenesis.

Pregnant mice were exposed to 150 micrograms benzo[a]pyrene (BaP) per gram of body weight during fetogenesis (d 11-17 of gestation) and the progeny were assayed for humoral and cell mediated immune responses at different time intervals after birth. Immature offspring (1-4 wk) were severely suppressed in their ability to produce antibody-(plaque-) forming cells (PFC) against sheep red blood cells (SRBC) and in the ability of their lymphocytes to undergo a mixed lymphocyte response (MLR). Lymphocytes from these progeny showed a moderate to weak capacity to inhabit production of colony-forming units (CFU) in host spleens following transfer with semiallogeneic bone marrow (BM) cells into lethally X-irradiated recipients syngeneic to the BM (in vivo graft-versus-host response, GVHR). A severe and sustained suppression in the MLR and the PFC response occurred from the fifth month up to 18 mo. The in vivo GVHR, also subnormal later in life, was not as severely suppressed as the other two parameters. Tumor incidence in the BP-exposed progeny was 8- to 10-fold higher than in those encountering corn oil alone from 18 to 24 mo of age. These data show that in utero exposure to the chemical carcinogen BaP alters development of components needed for establishing competent humoral and cell-mediated functions of the immune apparatus and leads to severe and sustained postnatal suppression of the defense mechanism. The immunodeficiency exhibited, particularly in the T-cell compartment (MLR, GVHR), before and during the increase in tumor frequency, may provide a favorable environment for the growth of nascent neoplasms induced by BaP.

Polymorphic expression of arylamine N-acetyltransferase (EC 2.3.1.5) may be a differential risk factor in metabolic activation of arylamine carcinogens and susceptibility to cancers related to arylamine exposures. Human epidemiological studies suggest that rapid acetylator phenotype may be associated with higher incidences of colorectal cancer. We used restriction fragment length polymorphism analysis to determine acetylator genotypes of 44 subjects with colorectal cancer and 28 non-cancer subjects of similar ethnic background (i.e., approximately 25% Black and 75% White). The polymorphic N-acetyltransferase gene (NAT2) was amplified by the polymerase chain reaction from DNA templates derived from human colons of colorectal and non-cancer subjects. No significant differences in NAT2 allelic frequencies (i.e., WT, M1, M2, M3 alleles) or in acetylator genotypes were found between the colorectal cancer and non-cancer groups. No significant differences in NAT2 allelic frequencies were observed between Whites and Blacks or between males and females. Cytosolic preparations from the human colons were tested for expression of arylamine N-acetyltransferase activity. Although N-acetyltransferase activity was expressed for each of the arylamines tested (i. e., p-aminobenzoic acid, 4-aminobiphenyl, 2-aminofluorene, beta-naphthylamine), no correlation was observed between acetylator genotype and expression of human colon arylamine N-acetyltransferase activity. Similarly, no correlation was observed between subject age and expression of human colon arylamine N-acetyltransferase activity. These results suggest that arylamine N-acetyltransferase activity expressed in human colon is catalyzed predominantly by NAT1, an arylamine N-acetyltransferase that is not regulated by NAT2 acetylator genotype.(ABSTRACT TRUNCATED AT 250 WORDS)

The relation between the amount of isologous bone marrow injected into a lethally irradiated mouse and its 30 day survival, its bone marrow response, the histology of the bone marrow in its left femur, its peripheral blood leukocyte count, the weight of its thymus, spleen, and body, and its appearance showed that quicker recovery of these end points occurred with increasing amounts of bone marrow administered. The bone marrow parameter was the quickest to respond to the varying amounts of bone marrow injected. In addition, no optimum dose of bone marrow was found in these experiments for this end point. This indicates that the bone marrow of an irradiated mouse could be made to show even quicker return to normal by injection of greater amounts of cells. The peripheral blood leukocyte count and the spleen weight also showed very quick recovery with the massive doses of bone marrow injected. For both end points, however, an optimum response was reached, which in the leukocytes, was 64.4 x 106 -237.9 x 106 cells injected, and in the spleen weight, 12.8 x 106 -237.9 x 106. An optimum response for thymus weight was also found with bone marrow doses of 64.4 x 106 - 237.9 x 106 cells. The cell dose for the optimum response in recovery of body weight was 12.8 x 106 - 237.9 x 106. Optimum 30 day survival was reached with injection of 64.4 x 106 bone marrow cells in these experiments. However, doses from 12.8 x 106 to 64.4 x 106 cells were not tested. The dose of bone marrow cells that was calculated to give 50 per cent 30-day survival was 0.42 x 106 (0.17 x 106, 1.92 x 106) cells for the males and 1.06 x 106 (0.42 x 106, 2.51 x 106) cells for the females. The calculated dose of bone marrow cells that would give 1 per cent 30-day survival of the males was 0.008 x 106 (0.0008 x 106, 0.0284 x 106) and for the females 0.0102 x 106 (0.001 x 106, 0.040 x 106) cells. These point estimates seem to be unreliable in view of the extremely large 95% confidence intervals. However, in experiments done by other workers at the National Cancer Institute similar to those reported in this paper, M. Schneiderman determined a threshold dose ranging from 0.0026 to 0.0320 x 106 cells by a somewhat different analysis of the data.7 Jacobson et al. cite a figure of 3-5 x 106 bone marrow cells from young donor mice as causing 53% 28-day survival in CF No. 1 mice exposed to 900 r.2 In using bone marrow from older mice, they found that 5-9.9 x 106 cells caused 54.9% 28-day survival. They also estimate that 50,000 cells are necessary to produce significant recovery of mice after an LD99 exposure. This figure is similar to that determined from the results of the present experiments. The results obtained from mice injected intravenously with a massive dose of bone marrow 3 days after irradiation indicated that the number of cells in the bone marrow of the right femur can be elevated within a few hours after injection. However, this could be observed only in an irradiated animal where the number of cells in the right femoral bone marrow was already low. A similar observation was made by Graevsky.8 This finding gives further support to the hypothesis that intravenously injected bone marrow transplants to bone marrow sites in the irradiated host.9