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Biomedical subjects

M Hollstein

Publications and source records attributed to M Hollstein.

At least 55 records · Page 3Linked to original sources
PubMed1994

Absence of p53 mutation at codon 249 in duck hepatocellular carcinomas from the high incidence area of Qidong (China).

Dietary aflatoxin and hepatitis B virus infection may play a role in generating the p53 tumor suppressor gene codon 249 hotspot mutation found in human hepatocellular carcinomas (HCCs) from Qidong (China) and southern Africa. No data are available on the HCC site-specific mutation of the p53 gene in hepadnavirus-infected animals exposed to AFB1. We have searched for the presence of p53 gene codon 249 mutations in both duck hepatitis B virus (DHBV) positive and negative HCCs of domestic ducks from Qidong, where the human p53 hotspot is so prevalent, as well as in duck HCCs experimentally induced by AFB1. Direct sequencing of DNA amplification products encompassing p53 codon 249 did not reveal any mutations in 11 HCCs from Qidong ducks, regardless of the status of DHBV infection. In addition no mutation was detected in four HCCs from AFB1-treated ducks. This contrasts with the human data; however, in humans, the mutation and the preferential binding of AFB1 to codon 249 occurs at the third nucleotide G, while in duck, the codon 249 lacks this G residue. The DNA sequence of adjacent codons is also different in the two species even though the amino acid sequence is identical. This may explain the low frequency of mutation we have observed. In addition, species differences in metabolism and DNA repair could influence the occurrence of codon 249 mutations.

Aflatoxin B1↗
PubMed1994

Database of p53 gene somatic mutations in human tumors and cell lines.

A data base is described in which over 2,500 mutations in the p53 gene of human tumors and tumor cell lines are compiled from a systematic search of reports published before 1 January 1994. Data from 1994 are being added intermittently, with a systematic search and update scheduled for December, 1994. The compilation has been deposited with the EMBL Data Library and is available in electronic form free of charge. This report contains a rationale for the compilation, a brief summary of the major findings and a description of the data base.

DNA Mutational Analysis↗
PubMed1993

Correlation of p53 mutations with epidermal growth factor receptor overexpression and absence of mdm2 amplification in human esophageal carcinomas.

Esophageal carcinomas from 24 patients, most of whom were smokers and consumed alcoholic beverages daily, were analyzed for mutations in exons 5-8 of the p53 tumor suppressor gene. Mutations were identified by polymerase chain reaction amplification and direct sequencing in 12 of 24 (50%) of the samples; almost half of the mutations were at A:T base pairs. Nuclear accumulation of p53 protein, determined by immunohistochemistry with the CM-1 polyclonal antibody, was observed in all cases in which a missense mutation in the p53 gene was detected. None of the 24 carcinomas had amplification of the mdm2 gene, an alternate pathway to p53 loss of function. Alterations involving three other cancer-related genes associated with human esophageal carcinogenesis, c-erbB-1/epidermal growth factor receptor (EGFR), c-myc, and retinoblastoma (Rb), were examined by Southern blot or immunohistochemical analysis in the same sample set to explore the possibility of a link between oncogene activation and loss of tumor suppressor function. While no associations were observed between amplification of the c-myc or EGFR genes and p53 abnormalities, a significant correlation (P < 0.01) was seen between the presence of p53 mutation and EGFR overexpression. Absence of Rb protein, measured immunohistochemically, was observed in four tumors, none of which had aberrations of the p53 gene.

Carcinoma, Squamous Cell↗
PubMed1993

DNA amplification in human gastric carcinomas.

We recently identified a genomic domain at chromosome 10q26 that is highly amplified in the gastric carcinoma cell lines KATO III and SNU-16 and contains the BEK/K-sam gene, which encodes several growth factor receptors. A contiguous segment of 200 kb spanning this gene was amplified in five of 139 (3.6%) primary gastric carcinomas, all of them classified as poorly differentiated tumors. There was no amplification of this genomic region in a variety of other solid tumors. The overall frequency of gene amplification among the gastric carcinomas rose to 19.4% when MYC, ERBB2, and INT2 were included in the analysis, with significant association with advanced tumor stage. Amplification of various genomic regions in solid tumors may be more frequent than previously estimated.

Carcinoma↗
PubMed1992

Chemosensitivity of human MCF-7 breast cancer cells to diastereoisomeric diaqua(1,2-diphenylethylenediamine) platinum(II) sulfates and specific platinum accumulation.

Cisplatin, raceme-diaqua[1,2-bis(4-fluorophenyl)ethylenediamine]platinu m(II) sulfate (compound I), meso-diaqua[1,2-bis(4-fluorophenyl)ethylenediamine]-platinum(II) sulfate (compound II), and meso-diaqua[1,2-bis(2,6-dichloro-4- hydroxyphenyl)ethylenediamine]platinum(II) sulfate (compound III) were compared with regard to their effect on the MCF-7 breast cancer cell line in vitro. At equimolar concentrations (5 microM), cisplatin, compound I, and compound II were equiactive after 231 h drug exposure, whereas compound III was ineffective. Although compounds I and II showed markedly greater inactivation than did cisplatin after 6 h incubation with culture medium, compound I (but not compound II) exhibited antitumor activity equivalent to that of cisplatin when cells were exposed to the drugs for 6 h. Platinum measurements by neutron-activation analysis revealed that compound I was selectively and rapidly accumulated by MCF-7 cells, resulting in a high degree of DNA platination within the first few hours of drug exposure. However, when the drug-exposure period was long enough, platinum enrichment was not reflected in an overall difference in the cytotoxicity of compound I vs cisplatin. Nevertheless, compound I should be superior to cisplatin in vivo, provided that effective plasma levels can be maintained for about 6 h.

Breast Neoplasms↗
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

[Activation of the Ha-ras oncogene in tumors induced in mice by transplacental exposure to 7,12-dimethylbenz(a)anthracene].

A study of tumors induced in mice by transplacental exposure to 7,12-dimethylbenz(a)anthracene (DMBA) alone or in combination with postnatal tissue-specific promotion showed skin and liver tumor development to be associated with cellular Ha-ras oncogene activation in a large percentage of cases. As shown by Xba I RFLP, oncogene activation was caused by T for A substitution at the second position of codon 61. The said mutation was traced in DMBA-induced tumors of the liver alone but not in spontaneous hepatomas. The results of the study showed the role of oncogene activation in cancer development to be tissue-specific.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1990

Tissue-specific activating mutations of Ha- and Ki-ras oncogenes in skin, lung, and liver tumors induced in mice following transplacental exposure to DMBA.

Transplacental carcinogenesis represents a good model in which to study the involvement of tissue-specific oncogene activation in carcinogenesis because a single exposure to a carcinogen induces tumors at various sites. We tested tumors of the skin, liver, and lung produced in mice after transplacental 7,12-dimethylbenz[a]-anthracene (DMBA) exposure for possible activation of ras genes. XbaI restriction fragment-length polymorphism analysis has shown that exposure to DMBA in utero may result in appearance of A----T transversion at the second position of codon 61 of Ha-ras oncogene in skin and liver tumors but not in lung tumors. Moreover, DNA samples isolated from spontaneous and DMBA-induced lung and liver tumors were analyzed for mutations at the same position of Ki-ras oncogene using differential hybridization with specific oligonucleotides. Among five spontaneous lung tumors, three cases of A----G transition, and one case of A----T transversion were found, whereas four of ten lung tumors of DMBA-treated animals were positive for A----T mutation. No Ki-ras mutation was detected in one spontaneous and four DMBA-induced hepatomas. In two cases, we revealed Ki-ras A----T mutation in the lung tumor and Ha-ras mutation in the liver tumor taken from the same animal. These results indicate first that DMBA treatment may induce A----T mutation at the second position of codon 61 both in Ha-ras and in Ki-ras and, second, that the role of different activated oncogenes in carcinogenesis may differ, depending on the tissue in which the tumor develops.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1989

Role of oncogene activation during prenatal (transplacental) initiation and postnatal promotion of mouse skin tumours.

The transplacental initiation-postnatal promotion model of mouse skin carcinogenesis is useful in studying the molecular and cellular mechanisms of perinatal carcinogenesis. Offspring transplacentally exposed to an initiating dose of a carcinogen typically do not produce any skin tumours in the absence of postnatal treatment; many skin tumours appear only when they are treated with tumour-promoting agents postnatally. Tumour-promoting agents alone produce no skin tumours or only a few. Thus, two stages of carcinogenesis, initiation and promotion, can be conveniently separated. Our results indicate that fetal c-Ha-ras can be transplacentally activated through a specific point mutation by a carcinogen. However, since postnatal promotion was essential for the production of tumours, they also suggest that a cell harbouring such a mutation may remain dormant until it encounters a tumour-promoting stimulus. Since a higher fraction of carcinomas than papillomas contained the specific mutation in Ha-ras, it is postulated that those papillomas with the point mutation have a selective advantage to progress towards carcinomas.

Animals↗
PubMed1988

Cellular-oncogene expression in Friend erythroleukemia cells: relationship to differentiation, commitment and TPA effects.

Induced differentiation of Friend erythroleukemia cells can be continuously and reversibly inhibited by phorbol ester tumor promoters, e.g. 12-O-tetradecanoylphorbol-13-acetate (TPA), for many years, allowing us to study the mechanisms of differentiation and its inhibition by TPA. We previously identified two steps in the differentiation process, which can be inhibited by TPA, before and after commitment to differentiation. Using permanently committed cells and TPA-resistant variants we examined the role of cellular oncogenes in Friend cell differentiation control, and their possible modulation by tumor-promoting phorbol esters. We report here characteristic changes in myc, myb and fos mRNA levels upon induction of differentiation by hexamethylene bisacetamide treatment, and present evidence that c-myb mRNA decline is one feature of Friend cell commitment to differentiation. In addition, using our TPA-sensitive and resistant cell lines, we observed that the hexamethylene bis-acetamide induced pattern of oncogene expression is unperturbed by TPA, regardless of whether the cells are differentiating or not.

Cell Differentiation↗
PubMed1987

Transplacental induction of a specific mutation in fetal Ha-ras and its critical role in post-natal carcinogenesis.

Mouse skin tumors were produced after transplacental initiation [with 7,12-dimethylbenz(a)anthracene], only when the skin was treated post-natally with a tumor-promoting agent (12-O-tetradecanoyl phorbol 13-acetate). DNA analysis of tumors showed that all carcinomas analyzed contained a specific mutation (A to T transversion) at the 61st codon of c-Ha-ras. Fifty per cent of the papillomas analyzed also had this same mutation. The A to T transversion at the 61st codon of Ha-ras was heterozygous in all positive papillomas and carcinomas. No such mutation was found when benzo(a)pyrene was used as an initiating agent. These results indicate that fetal c-Ha-ras can be transplacentally activated through a specific point mutation by a carcinogen, but a cell harboring such a mutation may remain dormant until it encounters a tumor-promoting stimulus.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1987

Selective lack of intercellular communication between transformed and nontransformed cells as a common property of chemical and oncogene transformation of BALB/c 3T3 cells.

BALB/c 3T3 cells can be transformed by transfection of an activated cellular oncogene as well as by chemicals. When the cells were transformed by pEJ-ras transfection, a marked increase in Mr 21,000 protein expression was found by Western blotting and immunohistochemical staining, whereas no such increase was detected in cells transformed by methylcholanthrene, suggesting two different molecular mechanisms. By directly microinjecting a fluorescent dye (Lucifer Yellow CH) into individual cells, we measured junctional intercellular communication among and between transformed and surrounding nontransformed cells. In both chemical and oncogene transformation studies, transformed cells and surrounding normal cells have similar capacities for gap-junctional communication, but there was complete lack of communication between transformed and nontransformed cells. When BALB/c 3T3 cells were transformed by methylcholanthrene initiation followed by phorbol ester promotion, again we saw no intercellular communication between transformed and nontransformed cells, suggesting that the observed selective communication block between transformed and nontransformed cells may be a general phenomenon in BALB/c 3T3 cells. These results indicate that selective lack of intercellular communication between transformed and surrounding normal cells may be an important phenomenon that separates transformed cells and nontransformed cells, permitting transformed cells to maintain autonomous growth.

Cell Communication↗
PubMed1986

Detection of DNA base damage by 32P-postlabelling: TLC separation of 5'-deoxynucleoside monophosphates.

Traces of damaged bases in DNA can be detected without the use of radioactive chemical agent or radiolabelled DNA substrate by incorporation of radiolabel into DNA after exposure to the chemical. This postlabelling approach to carcinogen adduct analysis is potentially useful for adduct detection in the DNA of humans exposed to carcinogens. We describe here the postlabelling analysis of DNA by chromatography of deoxynucleoside monophosphates. Separation and characterization of modified residues in nucleotide digests of DNA treated in vitro with chloroacetaldehyde is demonstrated.

Acetaldehyde↗