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C C Harris

Publications and source records attributed to C C Harris.

At least 181 records · Page 10Linked to original sources
PubMed1992

Detection by 32P-postlabelling of DNA adducts induced by free radicals and unsaturated aldehydes formed during the aerobic decomposition of fecapentaene-12.

Fecapentaene-12 (fec-12), excreted in human faeces, is genotoxic to human cells and a known animal carcinogen. The mechanism of its genotoxicity is unknown but may involve direct alkylation and/or free-radical generation. The formation of reactive species during fec-12 aerobic degradation was thus investigated by electron paramagnetic resonance (EPR) and NMR spectroscopic techniques. Oxy- and alkyl-radicals were detected as the 5,5'-dimethyl-1-pyrroline-N-oxide spin-trap adducts at fec-12 concentrations of between 0.1 and 2.0 mM. Under anaerobic conditions no free-radical generation was observed. NMR spectroscopy indicated that fec-12 degraded at least initially into three unsaturated aldehydes. The co-formation of free-radicals and unsaturated aldehydes suggests that fec-12 decomposed aerobically via a process analogous to lipid peroxidation. As both types of species, thus formed, may subsequently interact with DNA to form adducts, fec-12-induced DNA damage was investigated by 32P-postlabelling techniques. Using procedures that detect alkyl-type adducts, a number of putative adducts were detected in fec-12-treated DNA; two of similar mobility were observed in fec-12-treated 2'-deoxyguanosine-3'-monophosphate. Adducts with similar mobility have been detected in acrolein-treated DNA. One adduct with similar mobility was also observed in DNA obtained from normal human fibroblasts treated with fec-12. Using a C-18 ODS column, these putative adducts were eluted in 60-85% methanol, whereas 8-hydroxydeoxyguanosine-3'-monophosphate (8OHdGp) was eluted with 1% acetonitrile. Also unlike these putative adducts, the detection of 8OHdGp required HPLC fractionation prior to 32P-postlabelling. The formation of adducts, possibly aldehyde-related, and free-radical damage suggests that fec-12 genotoxicity may be the result of several different mechanisms, the relative importance of each is as yet unknown. Hydroxyl radicals were also detected during the aerobic decomposition of deca-2,4,6,8-tetraenal, a possible degradation product of fec-12 and a less potent mutagen, suggesting that free-radical generation may have only a minor role in fec-12-induced genotoxicity.

Autoradiography↗
PubMed1992

Human mesothelioma cells and asbestos-exposed mesothelial cells are selectively resistant to amosite toxicity: a possible mechanism for tumor promotion by asbestos.

To determine if asbestos exposure could contribute to mesothelial cell carcinogenesis by selection and/or expansion of an initiated cell population, we compared normal human pleural mesothelial cells to either human mesothelioma cell lines or mesothelial cells transfected with cancer-related genes for sensitivity to amosite fibers in vitro. Neither normal nor mesothelioma cells were directly stimulated to replicate or increase DNA synthesis by any of the asbestos exposure conditions tested. The potential selective effect of asbestos exposure was demonstrated by a differential sensitivity of normal mesothelial cells and mesothelioma cells to amosite: for example, up to 20-fold higher concentrations of amosite fibers were required to inhibit replication of mesothelioma cell lines than normal mesothelial cells. In addition, a significant resistance (4-fold) to amosite toxicity was observed for SV40 immortalized mesothelial cell lines that had previously been selected in vitro for resistance to asbestos. SV40 immortalized cells that have become tumorigenic after transfection with either Ha-ras or PDGF A-chain genes were not significantly more resistant to the cytotoxic effects of amosite than primary normal cells, and the primary cells were equally sensitive to amosite as mesothelial cells that were only immortalized by SV40. The sensitivity of normal mesothelial cells to asbestos does not appear to be simply a result of general fragility of the mesothelial cells, since similar levels of hydrogen peroxide and silica were cytotoxic for normal mesothelial cells and mesothelioma cell lines. Because mesothelioma cells have a greater resistance to asbestos cytotoxicity than normal mesothelial cells, we hypothesize that a differential resistance to cell killing by asbestos fibers in vivo may result in a selective expansion of an initiated or transformed cell population and thus contribute to the carcinogenesis process. Since tumorigenicity and asbestos resistance occur independently of one another in genetically altered mesothelial cell lines, genotypic and phenotypic alterations that lead to tumorigenic conversion may not be the same changes that provide resistance to cell killing by asbestos.

Asbestos↗
PubMed1992

Measurement of neutrophil activation and epidermal cell toxicity by palytoxin and 12-O-tetradecanoylphorbol-13-acetate.

Palytoxin is a human and mouse skin irritant and complete mouse skin tumor promoter that differs from the well-studied phorbol ester class of tumor promoters in many respects. In this study, we have found palytoxin to stimulate the production of superoxide by isolated human neutrophils using electron paramagnetic resonance (EPR) spectroscopy with the spin-trap DMPO. This stimulation of oxyradical production by palytoxin is relatively weak, however, when compared to that by 12-O-tetradecanoylphorbol-13-acetate (TPA). The maximal amount of oxyradicals produced by palytoxin-stimulated neutrophils is 10(-4) mumols/10(6) neutrophils, and this stimulation requires nanomolar concentrations of palytoxin, with half maximal stimulation at concentrations of approximately 30 nM. In contrast, the tumor promoter TPA causes human neutrophils to generate in excess of 10(-3) mumols oxyradicals/10(6) neutrophils with concentrations as low as 1 nM. Toxicity to cultured human epidermal cells was observed at very low concentrations of palytoxin, with 50% loss of colony-forming efficiency observed at approximately 3 x 10(-13) M. For TPA, 50% loss of colony-forming efficiency for cultured epidermal cells requires approximately 5 nM. Thus, although palytoxin stimulates superoxide production in isolated neutrophils, epidermal cells are sensitive at much lower concentrations and are likely to be the important target cell in vivo. This is in contrast to TPA, where neutrophils are stimulated at concentrations less than those required to produce pathological effects on epidermal cells, suggesting that neutrophils may be an important target cell for TPA in vivo.

Acrylamides↗
PubMed1992

The debrisoquine metabolic phenotype and DNA-based assays: implications of misclassification for the association of lung cancer and the debrisoquine metabolic phenotype.

Debrisoquine is an antihypertensive drug that is metabolized by cytochrome P4502D6. Deficient metabolism is inherited as an autosomal recessive condition. We previously reported in a case-control study that extensive metabolizers of debrisoquine were at greater risk of lung cancer compared to poor and intermediate metabolizers. Cloning of the gene that encodes P4502D6 (CYP2D6) led to the identification of both wild-type and mutant forms of the gene. Subsequently, a DNA-restriction fragment length polymorphism (RFLP) was identified, and a Southern hybridization-based test was developed in an attempt to define the genotype. When the DNA-RFLP test was applied to stored DNA from our study subjects there was neither a significant association with the metabolic phenotype nor an association with lung cancer. Further work has demonstrated that the wild-type gene, which was characterized by a 29-kb allele, can also contain mutations that result in nonfunctional or absent proteins. When these mutations are present, individuals exhibit the poor or intermediate metabolizer phenotype in spite of the presence of the 29-kb putative wild-type allele. Sequence determination of the mutants led to the development of techniques to exploit the polymerase chain reaction, which, together with Southern analysis, have been reported to detect as many as 95% of poor metabolizers. This technique is being used to examine the association of the extensive metabolizer genotype with lung cancer in the subjects from the case-control study. Preliminary results indicate a weak association between the homozygous wild-type genotype and lung cancer; in contrast, the extensive metabolizer phenotype is strongly associated with lung cancer in this subset.(ABSTRACT TRUNCATED AT 250 WORDS)

Case-Control Studies↗
PubMed1992

Polycyclic aromatic hydrocarbon-DNA adducts and the CYP1A1 restriction fragment length polymorphism.

Human cancer risk assessment at a genetic level involves the investigation of carcinogen metabolism and DNA adduct formation. Wide interindividual differences in metabolism result in different DNA adduct levels. For this and other reasons, many laboratories have considered DNA adducts to be a measure of the biologically effective dose of a carcinogen. Techniques for studying DNA adducts using chemically specific assays are becoming available. A modification of the 32P-postlabeling assay for polycyclic aromatic hydrocarbon DNA adducts described here provides potential improvements in quantification. DNA adducts, however, reflect only recent exposure to carcinogens; in contrast, genetic testing for metabolic capacity indicates the extent to which carcinogens can be activated and exert genotoxic effects. Such studies may reflect both separate and integrated risk factors together with DNA adduct levels. A recently described restriction fragment length polymorphism for the CYP1A1, which codes for the cytochrome P450 enzyme primarily responsible for the metabolic activation of carcinogenic polycyclic aromatic hydrocarbons, has been found to be associated with lung cancer risk in a Japanese population. In a subset of individuals enrolled in a U.S. lung cancer case-control study, no association with lung cancer was found.

Blotting, Southern↗
PubMed1992

Relationship of H-ras-1, L-myc, and p53 polymorphisms with lung cancer risk and prognosis.

Proto-oncogenes (H-ras-1 and L-myc) and tumor-suppressor gene (p53) loci have been implicated in lung carcinogenesis. DNA restriction fragment length polymorphisms at these gene loci are being evaluated in a case-control study as markers predictive of risk for cancer or of prognosis when cancer is present. The cases and controls had a cigarette-smoking history of 40 or more pack years or other abnormalities in pulmonary function tests, their ages were closely matched (64 years for cases and 61 years for controls) and the ratio of Caucasians to African Americans was close to unity (cases, 0.95:1.00, controls, 1.00:0.88). The H-ras-1 gene contains an insertion deletion polymorphism. Inheritance of rare H-ras-1 alleles, defined by MspI digestion, confers a relative risk for lung cancer of 2.0 (95% confidence interval, 0.5-7.3) for Caucasians and 3.2 (0.9-11.6) for African Americans (74 cases, 67 controls). The L-myc gene sequence has a restriction site (EcoR1) polymorphism between the second and third exons. Inheritance of restriction site-present alleles was reported to confer poor prognosis (presence of lymph node metastases) in Japanese lung cancer patients. This hypothesis was tested in both case-control study subjects (56 cases, 55 controls) and additional surgical cases (40), but no evidence was found to support the hypothesis in the U.S. population. The p53 gene is a tumor-suppressor gene that can encode either a proline or an arginine in the 72nd residue. No associations was found between the minor allele (proline) and diagnosis of lung cancer (76 cases, 68 controls).(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed1991

Immortalization of normal human bronchial epithelial cells by human papillomaviruses 16 or 18.

Human papillomaviruses (HPV) are associated with papillomatosis of the larynx, trachea, and bronchi in decreasing order of frequency, and these papillomatosis lesions may become malignant. When the patients are not selected for a history of papillomatosis, the frequency of HPV in bronchogenic carcinoma tissue is 1-5%. In order to develop a model for investigating the role of HPV in human bronchogenic carcinogenesis, normal human bronchial epithelial cells were transfected with cloned full-length HPV16 or HPV18. Two HPV18-transformed cell lines (BEP1 and BEP2) and one HPV16-transformed cell line (BEP3) were established. These nontumorigenic epithelial cell lines have: (a) attained over 100 population doublings in vitro; (b) mutually exclusive human marker chromosomes; (c) HPV DNA in forms that are consistent with chromosomal integration by Southern analysis; (d) HPV E6, E7, and E6* mRNA transcripts by Northern and reverse transcriptase-polymerase chain reaction analysis; and (e) diminished confluence-induced squamous differentiation. These cell lines should be useful for studying mechanisms involved in proliferation, differentiation, and neoplastic transformation of human bronchial epithelial cells.

Base Sequence↗
PubMed1991

Measurement of 4-aminobiphenyl-hemoglobin adducts in lung cancer cases and controls.

Hemoglobin adducts of the activated carcinogenic aromatic amine 4-aminobiphenyl have been measured in a case-control study of lung cancer. Data obtained for lung cancer cases are compared to those obtained for controls that consisted of patients with either chronic obstructive pulmonary disease or non-pulmonary cancers. Both simple and multivariate analysis found a positive association of 4-aminobiphenyl-hemoglobin adducts with the quantity of tobacco smoked as determined by either urine cotinine or questionnaire data. No association was found between 4-aminobiphenyl-hemoglobin adducts and cancer diagnosis, and adduct levels were not related to remote tobacco use, i.e., total pack years of smoking. There was no association between the levels of adducts detected and the ability of an individual to metabolize debrisoquine (debrisoquine metabolic phenotype, CYP2D6). Whereas 4-aminobiphenyl-hemoglobin adduct levels reflected recent tobacco smoking, they were not correlated with lung cancer risk.

Aminobiphenyl Compounds↗
PubMed1991

Chemical and physical carcinogenesis: advances and perspectives for the 1990s.

Carcinogenesis is a multistage process driven by carcinogen-induced genetic and epigenetic damage in susceptible cells that gain a selective growth advantage and undergo clonal expansion as the result of activation of protooncogenes and/or inactivation of tumor suppressor genes. Therefore, the mutational spectra of chemical and physical carcinogens in these critical genes are of interest to define endogenous and exogenous mutational mechanisms. The p53 tumor suppressor gene is ideally suited for analysis of the mutational spectrum. Such an analysis has revealed evidence for both exogenous and endogenous molecular mechanisms of carcinogenesis. For example, an informative p53 mutational spectrum of frequent G----T transversions in codon 249 is found in hepatocellular carcinomas from either Qidong, People's Republic of China, or southern Africa. This observation links exposure to aflatoxin B1, a known cancer risk factor in these geographic regions, with a specific mutation in a cancer-related gene. Other studies indicate that abnormalities in genes controlling the cell cycle may cause genomic instability and increase the probability of neoplastic transformation. Finally, mechanistic understanding of carcinogenesis is leading to improved cancer risk assessment and to the identification of individuals at high cancer risk.

Animals↗
PubMed1991

Molecular epidemiology and the genetics of environmental cancer.

Environmental, occupational, and recreational exposures to carcinogens contribute to cancer risk in humans. Cancer formation is a multistage process involving tumor initiation, promotion, conversion, and progression. Carcinogens can affect any of these stages through genetic and epigenetic mechanisms. The association of a suspected carcinogenic exposure and cancer risk can be studied in populations with classic epidemiologic techniques. However, these techniques are not applicable to the assessment of risk in individuals. Molecular epidemiology, in contrast, is a field that integrates molecular biology, in vitro and in vivo laboratory models, biochemistry, and epidemiology to infer individual cancer risk. Carcinogen-macromolecular adduct levels, and somatic cell mutations can be measured to determine the biologically effective dose of a carcinogen. Molecular epidemiology also explores host cancer susceptibilities, such as carcinogen metabolic activation, DNA repair, endogenous mutation rates, and inheritance of mutated tumor suppressor genes. Substantial interindividual variation for each of these biologic end points has been shown and, therefore, highlights the need for assessing cancer risk on an individual basis. Given the pace of the last decade, it is feasible that the next 10 years will allow molecular epidemiologists to develop a cancer-risk profile for an individual that includes assessment of a number of factors. This will help focus preventive strategies and strengthen quantitative risk assessments.

Carcinogens, Environmental↗
PubMed1991

Genetic analysis of human esophageal tumors from two high incidence geographic areas: frequent p53 base substitutions and absence of ras mutations.

Esophageal squamous cell carcinoma (ESC) samples from patients residing in Uruguay and in Normandy, France, where alcoholic beverages and tobacco smoke are major risk factors, were analyzed for point mutations in the p53 tumor suppressor gene. Among 34 tumors (15 from Normandy and 19 from Uruguay) 15 point mutations in the p53 gene that result in amino acid substitutions or chain termination were identified by polymerase chain reaction amplification of exons 5-8 and direct DNA sequencing. Base substitutions in ESC from these high-incidence areas are dispersed over the midregion of the p53 gene. There are differences between ESC and other types of gastrointestinal cancer in the nature of frequent base substitutions. CpG to TpG transitions were far less prevalent in these ESC than in colorectal tumors, whereas G to T transversions, rarely found in colon cancers, were found in one-fourth of the ESC samples. Base substitutions at A:T pairs constitute an important fraction of ESC p53 mutations, in contrast to mutation patterns in most other types of solid tumors. In contrast to the frequent mutation of the p53 gene in these samples, no mutations in the H-, K-, or N-ras genes were found in 16 tumors from Uruguay by direct sequencing of exons in which transforming mutations are known to occur. A previous study on ras mutations in ESC from France was also negative (M. C. Hollstein et al., Cancer Res., 48: 5119-5123, 1988). The role of distinct etiological factors in generating these differences and the potential for linking patient exposure histories with patterns of p53 mutations in high risk populations are considered.

Adult↗
PubMed1991

Human bronchial epithelial cells transformed by the c-raf-1 and c-myc protooncogenes induce multidifferentiated carcinomas in nude mice: a model for lung carcinogenesis.

We have previously described the neoplastic transformation of immortalized human bronchial epithelial cells (BEAS-2B) by the combination of the c-raf-1 and c-myc protooncogenes and the concomitant induction of neuron-specific enolase mRNA expression (A. Pfeifer et al., Proc. Natl. Acad. Sci. USA, 86: 10075-10079, 1989). In this paper we describe the morphological, biochemical, and immunohistochemical characteristics of the primary c-raf-1/c-myc tumors, xenografts of these tumors, and tumors that originated from cell lines of the primary neoplasm. The tumors were morphologically characterized by the appearance of desmosomes and tonofilaments, microvilli, and dense core granules representing markers of squamous, glandular, and neuroendocrine differentiation, respectively. A total of 11 of 13 tumors were positive by immunohistochemical techniques for neuron-specific enolase, serotonin (nine of 13), and calcitonin (six of 13). Keratins were expressed in 11 of 13 tumors, and while specific keratins (K5, K7, K16/K17) decreased, there was an increase of vimentin in the tumor cells. Gastrin-releasing peptide immunoreactivity was detectable in a small number of tumors (five of 13). BEAS-2B cells transfected with the c-raf-1 and c-myc protooncogenes and cell lines established from the primary tumors expressed major histocompatibility Class II antigen which has been found on small cell lung carcinoma cells. The tumors induced by the c-raf-1 and c-myc protooncogenes resemble the multidifferentiated phenotype of small cell lung cancer frequently detected in vivo and present a defined model to study the relation between molecular markers, phenotypical appearance, and response to chemotherapeutic agents and radiation.

Adenocarcinoma↗
PubMed1991

A human bronchial epithelial cell strain with unusual in vitro growth potential which undergoes neoplastic transformation after SV40 T antigen gene transfection.

Bronchial epithelial cells were cultured from an individual with no evidence of malignant disease. These cells, designated HB56B, had a greatly extended in vitro life-span, being able to undergo 50 passages and 200 population doublings in contrast to the usual 3 to 4 passages and 20 to 30 population doublings characteristic of normal human bronchial epithelial cells. HB56B cells had karyotypic evidence of an amplified region on the short arm of chromosome II. Unlike normal bronchial epithelial cells, which undergo terminal squamous differentiation in vitro in response to fetal bovine serum, HB56B cells were only minimally affected by serum. These cells were readily established as an immortalized cell line, HB56B/5T, following transfection with a plasmid containing SV40 early region DNA. HB56B cells were non-tumorigenic in athymic nude mice, but HB56B/5T cells within a few passages of transfection with the SV40 plasmid formed tumors of which 28/37 regressed. HB56B cells may offer an experimental system for the study of proliferation, differentiation, and senescence control in human bronchial epithelial cells.

Adult↗
PubMed1991

p53 mutations in human cancers.

Mutations in the evolutionarily conserved codons of the p53 tumor suppressor gene are common in diverse types of human cancer. The p53 mutational spectrum differs among cancers of the colon, lung, esophagus, breast, liver, brain, reticuloendothelial tissues, and hemopoietic tissues. Analysis of these mutations can provide clues to the etiology of these diverse tumors and to the function of specific regions of p53. Transitions predominate in colon, brain, and lymphoid malignancies, whereas G:C to T:A transversions are the most frequent substitutions observed in cancers of the lung and liver. Mutations at A:T base pairs are seen more frequently in esophageal carcinomas than in other solid tumors. Most transitions in colorectal carcinomas, brain tumors, leukemias, and lymphomas are at CpG dinucleotide mutational hot spots. G to T transversions in lung, breast, and esophageal carcinomas are dispersed among numerous codons. In liver tumors in persons from geographic areas in which both aflatoxin B1 and hepatitis B virus are cancer risk factors, most mutations are at one nucleotide pair of codon 249. These differences may reflect the etiological contributions of both exogenous and endogenous factors to human carcinogenesis.

Amino Acid Sequence↗
PubMed1991

Mutational hotspot in the p53 gene in human hepatocellular carcinomas.

Human hepatocellular carcinomas (HCC) from patients in Qidong, an area of high incidence in China, in which both hepatitis B virus and aflatoxin B1 are risk factors, were analysed for mutations in p53, a putative tumour-suppressor gene. Eight of the 16 HCC had a point mutation at the third base position of codon 249. The G----T transversion in seven HCC DNA samples and the G----C transversion in the other HCC are consistent with mutations caused by aflatoxin B1 in mutagenesis experiments. No mutations were found in exons 5,6,8 or the remainder of exon 7. These results contrast with p53 mutations previously reported in carcinomas and sarcomas of human lung, colon, oesophagus and breast; these are primarily scattered over four of the five evolutionarily conserved domains, which include codon 249 (refs 4-9). We suggest that the mutant p53 protein may be responsible for a selective clonal expansion of hepatocytes during carcinogenesis.

Base Sequence↗