Biomedical subjects

L M Anderson

Publications and source records attributed to L M Anderson.

At least 55 records · Page 3Linked to original sources

PubMed1998

Skin tumorigenesis and Ki-ras and Ha-ras mutations in tumors from adult mice exposed in utero to 3'-azido-2',3'-dideoxythymidine.

This study was designed to evaluate the potential initiating effects of transplacental 3'-azido-2',3'-dideoxythymine (AZT) and the role of ras mutational activation in skin tumors induced in a two-stage mouse skin model. In addition, mouse liver and lung tumors from a transplacental AZT tumorigenicity study reported elsewhere (Olivero et al., J Natl Cancer Inst 89:1602-1608, 1997) were examined for evidence of ras activation. For both tumor studies, pregnant CD-1 mice were given either vehicle or 25 mg of AZT daily on days 12-18 of gestation. In the 1997 study, the offspring were given no further exposure and were killed at 1 yr of age. For the skin tumor study, all mice received twice-weekly topical 12-O-tetradecanoyl-phorbol-13-acetate (TPA) treatment from weeks 5-35; half of the mice had been exposed to AZT in utero. At weeks 16-18, 30, 31, and 34-41, the skin tumor incidences in mice given AZT and TPA were significantly higher than in mice given TPA alone (P < or = 0.05). At week 41, the average numbers of tumors per mouse were 1.44+/-0.36 (mean +/- standard error of the mean) and 0.57+/-0.13 for mice given AZT plus TPA and TPA alone, respectively (P = 0.006). Mutagenesis in ras exons I and II was determined by polymerase chain reaction (PCR) and dye-terminator cycling sequencing of PCR products. Ha-ras exon I codons 12 and 13 were mutated in 11 of 19 tumors (58%) from mice given AZT and TPA and in one of 15 tumors (7%) from mice given TPA alone (P= 0.004). The only mutation in Ha-ras codon 12 (four in four tumors examined) was a G-->A transition in the second base, and the major mutation in codon 13 (six in seven tumors examined) was a G-->T transversion in the second base. In skin tumors, AZT exposure did not increase the number of Ha-ras codon 61 mutations, and no Ki-ras mutations were observed. Analysis of ras mutations in liver and lung tumors from mice exposed to AZT in utero (Olivero et al., J Natl Cancer Inst 89:16021608, 1997) with no TPA promotion showed no significant AZT-related increases.

Animals↗

PubMed1997

Transplacental effects of 3'-azido-2',3'-dideoxythymidine (AZT): tumorigenicity in mice and genotoxicity in mice and monkeys.

BACKGROUND: When given during pregnancy, the drug 3'-azido-2',3'-dideoxythymidine (AZT) substantially reduces maternal-fetal transmission of human immunodeficiency virus type 1 (HIV-1). However, AZT has been shown to be carcinogenic in adult mice after lifetime oral administration. In this study, we assessed the transplacental tumorigenic and genotoxic effects of AZT in the offspring of CD-1 mice and Erythrocebus patas monkeys given AZT orally during pregnancy. METHODS: Pregnant mice were given daily doses of either 12.5 or 25.0 mg AZT on days 12 through 18 of gestation (last 37% of gestation period). Pregnant monkeys were given a daily dose of 10.0 mg AZT 5 days a week for the last 9.5-10 weeks of gestation (final 41%-43% of gestation period). AZT incorporation into nuclear and mitochondrial DNA and the length of chromosomal end (telomere) DNA were examined in multiple tissues of newborn mice and fetal monkeys. Additional mice were followed from birth and received no further treatment until subjected to necropsy and complete pathologic examination at 1 year of age. An anti-AZT radioimmunoassay was used to monitor AZT incorporation into DNA. RESULTS: At 1 year of age, the offspring of AZT-treated mice exhibited statistically significant, dose-dependent increases in tumor incidence and tumor multiplicity in the lungs, liver, and female reproductive organs. AZT incorporation into nuclear and mitochondrial DNA was detected in multiple organs of transplacentally exposed mice and monkeys. Shorter chromosomal telomeres were detected in liver and brain tissues from most AZT-exposed newborn mice but not in tissues from fetal monkeys. CONCLUSIONS: AZT is genotoxic in fetal mice and monkeys and is a moderately strong transplacental carcinogen in mice examined at 1 year of age. Careful long-term follow-up of AZT-exposed children would seem to be appropriate.

Animals↗

PubMed1997

Uptake and tissue distribution of chromium(III) in mice after a single intraperitoneal or subcutaneous administration.

The tissue levels of chromium were followed after single intraperitoneal or subcutaneous injection of 1 mmol CrCl3/kg body wt. in Swiss male mice. Blood levels were similar after both treatment modes, with half-lives of 31-41 h. Organs not directly exposed by i.p. treatment contained similar amounts in the two groups, with kidneys > lungs > heart > brain. However, after i.p. treatment peritoneal organs (liver, spleen, pancreas and testis) had 40- to 200-fold more chromium compared with s.c. Assay of subsurface liver tissue and of testes removed via the scrotum indicated infiltration of the organs, rather than surface adsorption, of peritoneal chromium. Relative chromium concentrations after i.p. treatment were liver > pancreas = spleen > testis and after s.c. liver > spleen > testis > pancreas. Thus, s.c. treatment with CrCl3 is as effective as i.p. in terms of absorption into the blood. Treatment i.p., leading to direct uptake into peritoneal organs, is an effective way to deliver high chromium doses to these organs, but does not model likely human exposure.

Animals↗

PubMed1997

CYP2E1 genetic polymorphisms and risk of nasopharyngeal carcinoma in Taiwan.

BACKGROUND: Nasopharyngeal carcinoma occurs disproportionately among individuals of Chinese descent. The cytochrome P450 2E1 enzyme (CYP2E1) is known to activate nitrosamines and other carcinogens that are possibly involved in the development of this disease. Certain alleles of the CYP2E1 gene are thought to be more highly expressed than others, and their distribution varies between Asian and Caucasian populations. We conducted a case-control study to investigate whether such variations affect the risk of developing nasopharyngeal cancer. METHODS: Three hundred sixty-four patients with nasopharyngeal carcinoma (96% of 378 eligible patients) and 320 control subjects (86% of 374 eligible subjects) were studied. A risk factor questionnaire was administered to participants to assess factors postulated to be linked to nasopharyngeal carcinoma. Peripheral blood was obtained from all subjects and DNA was purified from nucleated cells. A polymerase chain reaction-based restriction fragment length polymorphism assay that used the restriction enzymes Rsa I and Dra I was used to detect wild-type and variant forms of the CYP2E1 gene. RESULTS: Individuals homozygous for an allele of the CYP2E1 gene that is detected by Rsa I digestion (c2 allele) were found to have an increased risk of nasopharyngeal carcinoma (relative risk [RR] = 2.6; 95% confidence interval [CI] = 1.2-5.7); this effect was limited to nonsmokers (RR = 9.3; 95% CI = 2.7-32) and was not affected by alcohol consumption. CONCLUSIONS: Our findings suggest that the CYP2E1 genotype is a determinant of nasopharyngeal carcinoma risk.

Adult↗

PubMed1997

Oxidative DNA damage in tissues of pregnant female mice and fetuses caused by the tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK).

The tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), induces the promutagenic oxidative-damage DNA lesion, 8-oxo-2'-deoxyguanosine (8-oxo-dG), in adult animals. To investigate whether this alteration occurs in DNA after transplacental exposure, pregnant Swiss mice were administered single or multiple doses of NNK. The 8-oxo-dG was quantified in placenta, and maternal and fetal tissues. In maternal lungs, single and multiple doses of NNK significantly increased levels of 8-oxo-dG by 23% and 32%, respectively. In maternal liver, a significant 38% increase was observed after multiple dose treatment. In the fetuses, a significant 45% increase in 8-oxo-dG levels was observed in liver after multiple doses of NNK. This is the first demonstration of oxidative DNA damage after transplacental exposure to NNK, and supports the concept of maternal smoking as a contributor to the development of childhood cancer.

Animals↗

PubMed1997

Lack of p53 and ras mutations in Helicobacter hepaticus-induced liver tumors in A/JCr mice.

Helicobacter hepaticus is a recently discovered bacterium that invades mouse liver causing chronic active hepatitis followed by development of preneoplastic hepatocellular foci, hepatocellular adenomas and carcinomas. This establishes a unique animal model for study of the mechanisms of cancer development due to a chronic bacterial infection. A possible mechanism of bacteria-associated tumorigenesis is mutation of oncogenes or tumor suppressor genes. Since mutations in ras oncogenes have been widely detected in a variety of chemically induced and spontaneous mouse liver tumors and specific mutations in the p53 tumor suppressor gene have been associated with human bladder cancers attributed to chronic schistosomal infection, we studied exons 1 and 2 of the N-, K- and H-ras genes and exons 5-8 of the p53 gene for the presence of point mutations in 25 liver tumors from 10 naturally infected A/JCr mice, ranging in age from 16 to 24 months. The 20 adenomas and five carcinomas varied in size from 0.1 to 2.3 cm and arose in livers characterized by a wide assortment of pathological profiles, including hepatitis, inflammation, hyperplasia, hypertrophy, leukocyte infiltration, necrosis and focal phenotypic alteration. DNA samples extracted from formalin-fixed paraffin-embedded tissues were screened by PCR/SSCP analysis and showed no mutations in the analyzed genes. Complete absence of mutations in ras genes in 25 mouse liver tumors is unusual. Other genes may be targeted or H. hepaticus infection causes liver cancer through other pathways than direct damage to DNA.

Adenoma↗

PubMed1997

Elevated mitochondrial cisplatin-DNA adduct levels in rat tissues after transplacental cisplatin exposure.

Although there is evidence that the toxic effects of cis-diamminedichloroplatinum(II) (cisplatin) include morphologically abnormal mitochondria, direct demonstrations of mitochondrial DNA damage by this chemotherapeutic agent have rarely been reported. Here we show that, in rats exposed to a single dose of cisplatin during gestation, cisplatin-DNA binding levels in both maternal and fetal liver and brain mitochondrial DNA are higher than those observed in genomic DNA. Pregnant F344/NCr rats were injected i.p. with either 5 or 15 mg cisplatin/kg body wt at 18 days of gestation and killed 24 h later. Cisplatin-DNA adducts were determined by dissociation-enhanced lanthanide fluoroimmunoassay using a cisplatin-DNA standard modified in the same range as the biological samples. Values for genomic cisplatin-DNA adducts in multiple maternal and fetal tissues have been presented elsewhere. Here, genomic DNA adduct levels for liver, brain, kidney and placenta are reported again for comparison with mitochondrial DNA adduct levels in the same tissues. In maternal and fetal brain, mitochondrial DNA adduct levels were approximately 7- to 50-fold higher than genomic DNA adduct levels, and in fetal liver they were approximately 2- to 16-fold higher than genomic DNA adduct levels. These studies demonstrate extensive cisplatin-DNA adduct formation in brain and liver mitochondria of fetal rats exposed transplacentally and suggest that mitochondrial DNA in some organs may be a particular target for cisplatin genotoxicity.

Animals↗

PubMed1997

Proliferative lesions of oviduct and uterus in CD-1 mice exposed prenatally to tamoxifen.

Tamoxifen (TAM) is widely used as adjuvant breast cancer therapy after surgery and as a chemopreventive agent in women of child-bearing age. However, TAM therapy has been shown to result in an increased incidence of endometrial carcinoma in women. The present study was designed to investigate the effects of TAM (5 mg/kg and 7.5 mg/kg body wt) given i.g. to pregnant CD-1 mice (1x/day, days 12 through 18 of gestation) on their female offspring. Progressive proliferative hyperplasia of the oviduct was frequently seen in TAM-exposed offspring, reaching 100% incidence by 52 weeks in both treatment groups. These females also developed progressive proliferative uterine lesions, including moderate/severe cystic endometrial hyperplasia (34-50%) and polypoid adenomas (27-30%) between 53 and 78 weeks. Deciduomas (15%) occurred at young ages (12 and 24 weeks) while leiomyomas (14%), a malignant leiomyosarcoma, and ovarian granulosa cell tumors (14%), were found between 72 and 78 weeks. Our findings thus suggest a strong association between transplacental TAM and reproductive tract abnormalities in female CD-1 mice.

Animals↗

PubMed1997

Distinct time courses of increase in cytochromes P450 1A2, 2A5 and glutathione S-transferases during the progressive hepatitis associated with Helicobacter hepaticus.

Mice naturally infected by Helicobacter hepaticus develop a chronic active hepatitis leading to hepatocellular carcinoma. This mouse model of liver cancer was used to examine the impact of bacterial infection on the hepatic expression and activity of enzymes involved in carcinogen bioactivation (phase I enzymes) and detoxification (phase II enzymes). No major differences in total cytochrome P450 (CYP) content were found between control and infected mice during the course of the study. The most striking modulations of individual isoenzymes were the increases in immunohistochemical staining observed for CYP1A and CYP2A5 in relation to increasing age and liver lesions. The increase in CYP2A5 in mice aged over 12 months was confirmed by the observed increases in coumarin 7-hydroxylation (CYP2A5 substrate) in vitro and CYP2A5 mRNA levels by Northern blot analysis. Immunoblotting confirmed the specific induction of CYP1A2 in infected mice 12 and 18 months of age. Perfusion of liver with nitroblue tetrazolium, an indicator for superoxide formation, demonstrated that in livers of infected mice, hepatocytes often co-expressed CYP2A5 and formazan deposition. Concerning phase II enzymes, an enhancement of glutathione S-transferase (GST) activities, related to the disease process, was observed in infected mice. An age-specific increase of GSTpi and A4.4 (early stage of disease) and GST YaYa (>9 months) expression was also demonstrated by immunohistochemical staining. In contrast, catalase and glutathione-peroxidase activities, as well as reduced glutathione content were decreased in the early stages of disease (3-9 months) in infected mice compared to age-matched control mice. Overall, these results suggest that alterations in CYP and GST expression may contribute to the aetiology of tumour incidence due to H. hepaticus infection via production of reactive oxygen species.

Age Factors↗

PubMed1997

Enzymes involved in the bioactivation of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in patas monkey lung and liver microsomes.

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is a potent tobacco-specific carcinogen in animals. Our previous studies indicated that there are differences between rodents and humans for the enzymes involved in the activation of NNK. To determine if the patas monkey is a better animal model for the activation of NNK in humans, we investigated the metabolism of NNK in patas monkey lung and liver microsomes and characterized the enzymes involved in the activation. In lung microsomes, the formation of 4-oxo-1-(3-pyridyl)-1-butanone (keto aldehyde), 4-(methylnitrosamino)-1-(3-pyridyl-N-oxide)-1-butanone (NNK-N-oxide), 4-hydroxy-1-(3-pyridyl)-1-butanone (keto alcohol), and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) was observed, displaying apparent Km values of 10.3, 5.4, 4.9, and 902 microM, respectively. NNK metabolism in liver microsomes resulted in the formation of keto aldehyde, keto alcohol, and NNAL, displaying apparent Km values of 8.1, 8.2, and 474 microM, respectively. The low Km values for NNK oxidation in the patas monkey lung and liver microsomes are different from those in human lung and liver microsomes showing Km values of 400-653 microM, although loss of low Km forms from human tissue as a result of disease, surgery or anesthesia cannot be ruled out. Carbon monoxide (90%) significantly inhibited NNK metabolism in the patas monkey lung and liver microsomes by 38-66% and 82-91%, respectively. Nordihydroguaiaretic acid (a lipoxygenase inhibitor) and aspirin (a cyclooxygenase inhibitor) decreased the rate of formation of keto aldehyde and keto alcohol by 10-20 % in the monkey lung microsomes. Alpha-Napthoflavone and coumarin markedly decreased the oxidation of NNK in monkey lung and liver microsomes, suggesting the involvement of P450s 1A and 2A6. An antibody against human P450 2A6 decreased the oxidation of NNK by 12-16% and 22-24% in the patas monkey lung and liver microsomes, respectively. These results are comparable to that obtained with human lung and liver microsomes. Coumarin hydroxylation was observed in the patas monkey lung and liver microsomes at a rate of 16 and 4000 pmol/min/mg protein, respectively, which was 5-fold higher than human lung and liver microsomes, respectively. Immunoblot analysis demonstrated that the P450 2A level in the individual patas monkey liver microsomal sample was 6-fold greater than in an individual human liver microsomal sample. Phenethyl isothiocyanate, an inhibitor of NNK activation in rodents and humans, decreased NNK oxidation in the monkey lung and liver microsomes displaying inhibitor concentration resulting in 50% inhibition of the activity (IC50) values of 0.28-0.8 microM and 4.2-6.8 microM, respectively. The results demonstrate the similarities and differences between species in the metabolic activation of NNK. The patas monkey microsomes appear to more closely resemble human microsomes than mouse or rat enzymes and may better reflect the activation of NNK in humans.

Animals↗

PubMed1997

Promotion of dimethylbenz[a]anthracene-initiated mammary carcinogenesis by iron in female Sprague-Dawley rats.

Iron body-stores and iron dietary intake have been sporadically reported to increase the risk of cancer in humans. To investigate the effect of iron on the development of mammary tumors, female Sprague-Dawley rats were given dimethylbenz[a]anthracene (DMBA) (5 mg/kg, i.g., 1x) at 55 days of age. Eight days later, rats received iron(II) sulfate s.c. (50 micromol/kg, 2x/week) for 53 weeks. Mammary tumors started to appear 6-8 weeks after DMBA initiation. At 20 weeks after DMBA treatment, iron(II) increased mammary tumor frequency twofold (11/30 versus 5/30 with DMBA alone). Tumor frequency increased with time and was significantly higher in iron-promoted rats after 40 weeks of treatment (24/30 versus 11/30, P = 0.001). Also, mammary tumors in iron-promoted rats were significantly larger than in DMBA-only rats at 20 weeks after initiation (P = 0.04) and this difference remained significant through the observation time point at 40 weeks. Iron could be detected histochemically in the stromal connective tissue, but not in the epithelial cells of mammary carcinomas. Mammary tumors in the DMBA-only group were mostly adenomas and adenocarcinomas, while those promoted by iron sulfate included fibroadenomas, adenomas and adenocarcinomas. Thus, iron(II) administered s.c. subsequent to DMBA initiation, greatly accelerated mammary carcinogenesis, implying its promoting activity for mammary tissue of female rats.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed1997

Maternal acculturation and childhood immunization levels among children in Latino families in Los Angeles.

OBJECTIVES: This study examined the relationship between acculturation levels of poor Latina women in Los Angeles and their children's immunization status. Receipt of three doses of diphtheriatetanus-pertussis vaccine and two doses of oral polio vaccine by the age of 12 months was considered adequate immunization. METHODS: Household interviews were conducted in East Los Angeles and South Central Los Angeles with mothers (n = 688) about one randomly selected child aged 12 to 36 months. RESULTS: One fourth of the children were inadequately immunized. Less-acculturated mothers were more likely to have adequately immunized children. Inadequate prenatal care, absence of close family members, the child's birth position as other than firstborn, and more than one family relocation during the child's lifetime were associated with inadequate immunization. CONCLUSIONS: The findings challenge the notion that children of recent immigrants bear a higher risk of underimmunization.

Acculturation↗

PubMed1997

DNA adducts and the mechanism of carcinogenesis and cytotoxicity of methylating agents of environmental and clinical significance.

DNA adducts are covalent complexes formed between genotoxic carcinogens and DNA bases, and constitute a critical early intermediate on the pathway of chemical carcinogenesis. Their accumulation in different tissues reflects the amount of activated carcinogen reaching DNA, and can therefore serve as an index of the biologically relevant dose reaching the target tissues or cells. Methylating agents are of interest in view of their occurrence in the environment and their use as cytotoxic drugs in cancer chemotherapy. Current evidence indicates that O6-methylguanine plays a particularly important role in the mutagenic, carcinogenic, and cytotoxic activities of methylating agents. O6-Methylguanine is repaired efficiently by the enzyme O6-alkylguanine-DNA alkyltransferase (AGT). Lack of this enzyme results in excessive accumulation of O6-methylguanine and recent evidence suggests that significant quantitative effects on adduct accumulation may be linked to conditions of very low AGT levels. This would be important from the point of view of clinical practice, since modulation of AGT is under investigation as a means of enhancing the therapeutic efficacy of clinical agents acting via the production of O6-methylguanine and related adducts, such as, for example, procarbazine, dacarbazine, and some nitrosoureas. The measurement of O6-methylguanine in human DNA has been employed as a tool to investigate the role of environmental methylating agents in human carcinogenesis. While the nature and origin of the methylating agents responsible for these adducts is currently unknown, recent studies in patas monkeys have shown that N-nitrosodimethylamine, a methylating carcinogen to which human exposure is well documented, is capable of efficiently generating O6-methylguanine in most tissues, including fetal tissues. Furthermore, it has been found that this damage is substantially enhanced by the coadministration of ethyl alcohol which acts by inhibiting the liver first-pass metabolism of the carcinogen, an observation which supports the hypothesis that alcohol consumption may act as a risk factor in human carcinogenesis by augmenting the action of nitrosamines.

Animals↗

PubMed1997

Increased oxidative DNA damage and hepatocyte overexpression of specific cytochrome P450 isoforms in hepatitis of mice infected with Helicobacter hepaticus.

A recently discovered bacterium, Helicobacter hepaticus, infects the intrahepatic bile canaliculi of mice, causing a severe chronic hepatitis culminating in liver cancer. Thus, it affords an animal model for study of bacteria-associated tumorigenesis including H. pylori-related gastric cancer. Reactive oxygen species are often postulated to contribute to this process. We now report that hepatitis of male mice infected with H. hepaticus show significant increases in the oxidatively damaged DNA deoxynucleoside 8-hydroxydeoxyguanosine, with the degree of damage increasing with progression of the disease. Perfusion of infected livers with nitro blue tetrazolium revealed that superoxide was produced in the cytoplasm of hepatocytes, especially in association with plasmacytic infiltrates near portal triads. Contrary to expectations, Kupffer cells, macrophages, and neutrophils were rarely involved. However, levels of cytochrome P450 (CYP) isoforms 1A2 and 2A5 in hepatocytes appeared to be greatly increased, as indicated by the number of cells positive in immunohistochemistry and the intensity of staining in many cells, concomitant with severe hepatitis. The CYP2A5 immunohistochemical staining co-localized with formazan deposits resulting from nitro blue tetrazolium reduction and occurred in nuclei as well as cytoplasm. These findings suggest that CYP2A5 contributes to the superoxide production and 8-hydroxydeoxyguanosine formation, although reactive oxygen species from an unknown source in the hepatocytes leading to CYP2A5 induction or coincidental occurrence of these events are also possibilities. Three glutathione S-transferase isoforms, mGSTP1-1 (pi), mGSTA1-1 (YaYa), and mGSTA4-4, also showed striking increases evidencing major oxidative stress in these livers.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed1996

N-nitrosodimethylamine-derived O(6)-methylguanine in DNA of monkey gastrointestinal and urogenital organs and enhancement by ethanol.

N-nitrosodimethylamine (NDMA) is a human cancer initiator suspect. Ethanol, a cancer risk factor, may synergize with nitrosamines by suppressing hepatic clearance, to increase internal exposure. A limitation to these hypotheses is lack of activation of NDMA by many rodent tissues. However, systemtic primate studies are lacking. Patas monkeys were utilized to investigate NDMA activation by primate tissues in vivo, generating the promutagenic DNA lesion 0(6)-methylguanine (0(6)-meG). Adult monkeys received 0. 1 mg/kg NDMA by gavage, in some cases preceded by ethanol. Four hours after NDMA only, 0(6)-meG was detected in DNA from all tissues. Levels were highest in gastric mucosa and liver and were only about 50% lower in DNA from white blood cells, esophagus, ovary, pancreas, urinary bladder and uterus. With ethanol co-exposure, amounts of 0(6)-meG increased at least 2-fold in all tissues except liver. The largest effect was in esophagus (17-fold increase), followed by ovary, large intestine, urinary bladder, spleen and cerebellum (9- to 13-fold increases), and uterus, cerebrum and brain stem (7- to 8-fold increases). Alkylguanine alkyltransferase activities varied over a 30-fold range and were highest in liver and stomach. Thus primate tissues, especially those of the gastrointestinal and urogenital organs, are sensitive targets for DNA adduct damage due to NDMA, and ethanol co-exposure leads to striking increases in adducts. Our data support epidemiology implicating nitrosamines in causation of cancers of stomach and other organs, and alcohol as enhancing internal exposure to nitrosamines.

Alkylation↗

PubMed1996

Induction of hepatic and renal P4502E1 of neonatal rats exposed translactationally to ethanol.

The effect of maternal ethanol intake during lactation on neonatal cytochrome P4502E1 was investigated in Sprague-Dawley rats. Dams were exposed to 15% (v/v) ethanol in drinking water from day 1 of lactation to 4, 7 or 14 days postpartum. Significant (P < 0.01) enhancement of both hepatic and renal N-nitrosodimethylamine (NDMA) demethylase, an activity of P4502E1, was observed in lactating mothers given ethanol in drinking water. Demethylase activity also significantly increased (P < 0.01) in the 7- and 14-day livers of both female and male pups and in the 7- and 14-day female and 14-day male kidneys exposed to ethanol through the transmammary route. Cytochrome P4502E1 protein content, assayed by immunoblotting, increased in the maternal liver and kidney of all groups consuming ethanol. Neonatal P4502E1 protein content increased in the 7- and 14-day livers of both sexes and 14-day female kidneys exposed translactationally to ethanol. No effect of ethanol on enzyme activity or protein content of P4502E1 was observed in the liver or kidney of 4-day-old neonates. These results demonstrate the translactational effect of ethanol on neonatal P4502E1 enzyme, which is involved in the metabolism of many low molecular weight xenobiotics, and indicate the possibility of alterations occurring in the kinetics of neonatal drug and xenobiotic metabolism and also in processes connected with perinatal carcinogenesis.

Alcohol Drinking↗

PubMed1996

Variant mutational activation of the K-ras oncogene in renal mesenchymal tumors induced in newborn F344 rats by methyl(methoxymethyl)nitrosamine.

Renal mesenchymal tumors were induced at high incidence in F344 rats by a single intraperitoneal injection of methyl(methoxymethyl)nitrosamine (DMN-OMe) within 48 h after birth. DNAs from 18 of 35 mesenchymal tumors contained transforming ras sequences in NIH3T3 transfection assays: K-ras (17/18) or N-ras (1/18). Single-stranded conformational polymorphism analysis or dideoxy sequencing of polymerase chain reaction-amplified K-ras gene fragments revealed that these neoplasms contained a variety of activating mutations in the K-ras oncogene. Alterations in codon 12 predominated and included GGT --> GAT transitions, GGT --> GTT or TGT transversions, and previously reported insertion mutations, although some tumors expressed more than one mutation and the pattern of mutations even varied within tumors. Mutations were also found in exons 2 and 3. In addition, tumor transplantability into syngeneic hosts correlated positively and significantly with K-ras activation. Renal mesenchymal tumors with transforming mutations in exon 1 were often successfully passaged (10/12) while tumors which lacked mutations in exon 1 were infrequently transplantable (2/14). While the observed base substitutions in K-ras are consistent with adduct formation, the presence of insertion mutations and intratumor heterogeneity of alterations suggest that ras activation in DMN-OMe-induced tumors is not necessarily an early event in tumorigenesis.

Animals↗

PubMed1996

Cisplatin-DNA adduct formation in maternal and fetal rat tissues after transplacental cisplatin exposure.

Cis-diamminedichloroplatinum (II) (cisplatin), given to pregnant rats at 5 mg/kg body weight (bw) is a trans placental carcinogen for fetal liver, kidney, nervous system and lung, resulting in tumor incidences of 22.5, 10.5, 6.1 and 7.5% respectively, in offspring grown to adulthood (B.A. Diwan et al., 1995, Toxicol. Appl. Pharm., 132, 115). In this study, the capacity of cisplatin to pass through the placental barrier and bind covalently to DNA in maternal and fetal tissues was evaluated. Pregnant F344/NCr rats were injected i.p. with single doses of 5, 10 or 15 mg cisplatin/kg bw at 18 days of gestation and sacrificed 24 h later. Cisplatin-DNA adducts were determined by dissociation-enhanced lanthanide fluoroimmunoassay (DELFIA) using both High (90 pmol/micrograms DNA) and Low (0.50 pmol/ microgram DNA) Modified cisplatin-DNA standards and atomic absorbance spectrometry (AAS). The adduct quantities determined by the two DELFIAs varied in concert, but the DELFIA with Low Modified standard gave actual values similar to those observed with AAS. In maternal and fetal tissues, with the exception of placenta in one experiment and maternal kidney in another experiment, the extent of cisplatin-DNA adduct formation increased with dose. In maternal kidney, the low adduct levels observed at the 15 mg/kg dose may reflect kidney toxicity. Fetal kidney, liver and lung contained fewer cisplatin-DNA adducts than the corresponding maternal tissues. In contrast, at 5 and 15 mg/kg, fetal brain DNA contained higher adduct levels than maternal brain DNA. This study demonstrates the presence of DNA damage induced by cisplatin in multiple maternal and fetal rat tissues at tumorigenic doses of drug; the results are therefore consistent with the hypothesis that genotoxic mechanisms play an important role in the drug-induced tumor incidence.

Animals↗