Search PubMed⌕ Search

Biomedical subjects

B F Trump

Publications and source records attributed to B F Trump.

At least 19 recordsLinked to original sources
PubMed1992

Cytochrome P450IIE1 genetic polymorphisms, racial variation, and lung cancer risk.

Cytochrome P450IIE1 is responsible for the activation of carcinogenic N-nitrosamines, benzene, urethane, and other low-molecular-weight compounds. Restriction fragment length polymorphisms (PstI and RsaI restriction enzymes) have been identified in the cytochrome P450IIE1 transcription regulatory region that may affect expression. This study describes the PstI and RsaI polymorphisms in different racial populations and in a case-control study of lung cancer. The allelic frequencies were markedly different in Japanese, African-Americans, and Caucasians: the PstI rare allele was present at a frequency of 2% in Caucasians, 5% in African-Americans, and 24% in Japanese (P < 0.05). For the RsaI rare allele, frequencies were 2% in Caucasians, 2% in African-Americans, and 27% in Japanese (P < 0.05). The assay was also applied to 128 individuals enrolled in a case-control study of lung cancer. Although limited in statistical power, the data indicate no evidence for an association in the aggregate of cytochrome P450IIE1 PstI [for which the odds ratio was 0.7 (95% confidence interval (C.I.) = 0.2-2.8)] or RsaI [for which the odds ratio was 0.9 (95% C.I. = 0.2-5.4)] restriction fragment length polymorphisms with lung cancer in this U.S. population. When analyzed by race, the lung cancer odds ratio for the PstI mutant allele in African-Americans was 0.19 (95% C.I. = 0.03-1.38), and in Caucasians it was 4.13 (95% C.I. = 0.34-48.8). For the RsaI mutant allele, the odds ratios were 0.20 (95% C.I. = 0.02-2.43) and 4.28 (95% C.I. = 0.35-50.6), respectively. The ethnic differences of these restriction fragment length polymorphisms might be related to genetic susceptibilities for lung cancer among Caucasians and for gastric or esophageal cancer among Japanese.

Alleles↗
PubMed1992

p53 mutation and protein accumulation during multistage human esophageal carcinogenesis.

Preinvasive lesions of squamous cell carcinoma are well defined morphologically and provide a model for multistage carcinogenesis. Since alterations in the p53 tumor suppressor gene occur frequently in invasive esophageal squamous cell carcinoma, we examined a set of preinvasive lesions to investigate the timing of p53 mutation. Surgically resected tissues from nine patients with esophageal squamous cell carcinoma contained precursor lesions which had not yet invaded normal tissues. Immunohistochemistry showed high levels of p53 protein in both preinvasive lesions and invasive carcinomas in six cases; sequence analysis of all invasive tumors identified p53 missense mutations in two cases. Preinvasive lesions from both tumors with mutations plus one wild-type tumor were microdissected and sequenced. In one patient there were different mutations in the invasive carcinoma (codon 282, CGGarg > TGGtrp) and a preinvasive lesion (codon 272, GTGval > T/GTGleu/val). In a second case, an invasive carcinoma had a mutation in codon 175 (CGCarg > CAChis), and adjacent preinvasive lesions contained a wild-type sequence. A carcinoma and preinvasive lesion from the third case contained high levels of protein and a wild-type DNA sequence. Therefore, p53 mutation may precede invasion in esophageal carcinogenesis, and multifocal esophageal neoplasms may arise from independent clones of transformed cells. The timing of p53 protein accumulation is favorable for an intermediate biomarker in multistage esophageal carcinogenesis.

Base Sequence↗
PubMed1992

Role of [Ca2+]i in induction of c-fos, c-jun, and c-myc mRNA in rat PTE after oxidative stress.

Oxidative stress plays an important role in various types of cell injury and tumor promotion. Cells respond to oxidative stress in many ways including changes in membrane organization, ion movements, and altered gene expression, all of which contribute to the subsequent fate of affected cells. In this study, we investigated the expression of the proto-oncogenes c-fos, c-myc, and c-jun, which play a key role in proliferation and differentiation, using primary cultures of rat proximal tubular epithelium exposed to oxidative stress generated by the xanthine/xanthine oxidase system. This system generates superoxide and H2O2 in the extracellular space stimulating the release of active oxygen species from inflammatory cells. c-fos mRNA was expressed within 15 min, peaked at 30 min, and returned to constitutive levels by 3 h. c-jun mRNA began to rise after 30 min, peaked at 120 min, and remained above the constitutive levels up to 180 min. c-myc mRNA expression was less affected by the treatment, with levels increasing gradually over the 180 min period. The expression of c-fos was inhibited by superoxide dismutase but not by catalase and was super-induced by cycloheximide. H2O2 alone did not induce any c-fos mRNA in this system. Chelation of extracellular ionized calcium by EGTA or of intracellular ionized calcium by Quin 2/AM resulted in a marked decrease of c-fos expression. Two protein kinase C inhibitors, H-7 and staurosporine, partly diminished the expression of c-fos, whereas a third, 2-aminopurine, which has a broader spectrum of inhibiting protein kinases, almost completely abolished it. A poly ADP-ribosylation inhibitor, 3-aminobenzamide, had no effect on c-fos expression in this system. Our results show that oxidative stress provokes sequential expression of c-fos, c-jun, and c-myc, mRNA in this order. This c-fos expression appears to be largely controlled by calcium ion movement, which could include protein kinase C activation. Another protein kinase or kinases also appear to play an important role.

Alkaloids↗
PubMed1992

The role of cytosolic Ca2+ in cell injury, necrosis and apoptosis.

Increases in cytosolic Ca2+ are believed to be a pivotal signal in the regulation of cell injury, cell death, cell proliferation, cellular differentiation and cellular aging. Changes in the concentration of cytosolic Ca2+ are involved in both acute and chronic cell injury, as well as in accidental or programmed cell death. Signalling in all of these phenomena is dependent on mediated activities of a number of intracellular factors, including phospholipases, proteases and endonucleases. The coordinate regulation of these factors, as well as of oncogene activation, seems to play a role both in the processes of cell injury and cell death, and in the recovery from injury in sublethally injured cells.

Animals↗
PubMed1992

Injury-induced changes in cytosolic Ca2+ in individual rabbit proximal tubule cells.

Cell injury was studied in cultured rabbit proximal tubular epithelial cells using digital-imaging fluorescent microscopy to relate changes in cytosolic Ca2+ ([Ca2+]i) to bleb formation and cell death. Fura-2-loaded cells were treated in normal (1.37 mM) and low (less than 5 microM) extracellular Ca2+ ([Ca2+]e) with 1) inhibitors of glycolysis (iodoacetate) and/or mitochondrial oxidation (KCN), 2) thiol-modifying reagents (N-ethylmaleimide, p-chloromercuribenzene, and p-chloromercuribenzene sulfonate), and 3) Ca2+ ionophore (ionomycin). All three types of injury produced both [Ca2+]e-independent and [Ca2+]e-dependent increases in [Ca2+]i. KCN + iodoacetate +/- [Ca2+]e did not produce blebbing or death within 60-90 min. Thiol modifiers and ionomycin produced blebbing, which correlated with sustained threefold or greater elevations of [Ca2+]i and loss of viability only after [Ca2+]i had risen severalfold. Blebbing and cell death could be prevented or delayed by treatment in low [Ca2+]e. Trypsin (x0.5) caused a transient (less than 5 min) elevation in [Ca2+]i as well as increases in intracellular Ca2+ pools.

Animals↗
PubMed1992

Studies of skin toxicity in vitro: dose-response studies on JB6 cells.

There are many reasons for developing in vitro tests of toxicity including cost, speed, studies of mechanisms, and studies utilizing human cells and tissues. The present study focuses on the development of in vitro tests to predict in vivo toxicity by comparing them to data from the literature. A broad spectrum of model toxic compounds was evaluated for toxicity on mouse skin JB6 cells in culture. These included mercuric chloride, sodium lauryl sulfate, formaldehyde, dimethyl sulfoxide, benzoyl peroxide, and ionomycin, all of which have been proven to be positive in the Draize test or in cutaneous toxicity studies. Cell viability was evaluated every 15 min for up to 1 hr, and then after 24 hr of treatment using the Trypan Blue exclusion method; morphological changes were evaluated using phase-contrast and transmission electron microscopy. Dose- and time-dependent cell death and morphological changes were observed at concentrations ranging from 10(-14) to 10(-2) M. Arbitrary rankings were assigned based on 1) IC50 value estimated from the present data, and 2) in vivo toxicity reported in the Registry of Toxic Effects of Chemical Substances. Good correlation between in vitro and in vivo toxicity based on arbitrary rankings was observed. Thus, these findings suggest that the JB6 cell culture model can be used for predicting in vivo toxicity. In the future, it may be possible to utilize this system for the study of intracellular ionized calcium ([Ca2+]i), and the expression of oncogenes as early indicators of toxicity.

Animals↗
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

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

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

Quantitative analysis of adenine nucleotides during the prelytic phase of cell death mediated by C5b-9.

The nucleated cell death mediated by C5b-9 depends on the extent of C fixation and parameters that affect the ability of the cell to eliminate C5b-9. When C5b-9 formation exceeds elimination, cell death can be initiated. High Ca2+ in the medium accelerates Ehrlich ascites cell death induced by a large number of C5b-9, whereas osmotic prevention of cell swelling has little effect in protecting Ehrlich cells from killing by C5b-9. In the present study, we investigated the interrelationship between intracellular Ca2+, intra- and extracellular adenine nucleotides, and mitochondrial membrane potential, to understand the mechanism of acute cell death induced by C5b-9. When Ehrlich cells carrying C5b-8 were exposed to C9, rapid and profound ATP depletion in the cell was observed before cell death. Leakage of the adenine nucleotides ATP, ADP, and AMP also began during the prelytic phase. Studies using digital imaging fluorescence microscopy showed that loss of mitochondrial membrane potential was noted immediately after C9 addition but before nuclear staining with propidium iodide. These findings suggest that an increase in intracellular Ca2+ through C5b-9 channels and loss of mitochondrial membrane potential may initiate rapid cell death. The prelytic leakage of ATP precursors may also contribute to cell death by decreasing nucleotide pools, because recovery of ATP production was observed after a similar degree of ATP loss in cells exposed to sublethal doses of KCN, in which ADP and AMP leakage was not present.

Adenine Nucleotides↗
PubMed1991

Cytosolic Ca2+ deregulation and blebbing after HgCl2 injury to cultured rabbit proximal tubule cells as determined by digital imaging microscopy.

Acute injury to renal proximal tubule cells has previously been shown to result in elevated cytosolic Ca2+ ([Ca2+]i), blebbing, and eventual cell death. In this study, digital imaging fluorescence microscopy was used to evaluate these changes in response to HgCl2 treatment of cultured rabbit proximal tubular cells. Monolayer cells loaded with fura-2 were treated with 10, 50, or 100 microM HgCl2 in both 1.37 mM CaCl2-containing and nominally Ca(2+)-free (less than 5 microM) Hanks' balanced salt solution. [Ca2+]i was estimated by measuring the ratio of fluorescent image pairs (collected at 340- and 380-nm excitation), morphological changes were observed by phase-contrast microscopy, and viability was assessed by trypan blue exclusion. After exposure of cells to 10 microM HgCl2, [Ca2+]i initially increased about 2-fold by 5 min; after 50 or 100 microM HgCl2, [Ca2+]i rapidly rose 2- to 3-fold, peaked at 1-3 min, and then generally decreased slightly. In nominally Ca(2+)-free (less than 5 microM) medium, [Ca2+]i stabilized, but in 1.37 mM Ca(2+)-containing medium, [Ca2+]i continued to slowly rise, often reaching levels of fura-2 saturation. The rate and extent of blebbing and the rate of cell death were increased in the presence of 1.37 mM Ca2+. These results show that sustained elevations of [Ca2+]i precede both cell blebbing and cell death and that when these elevations are limited by removing extracellular Ca2+ the amount of blebbing is reduced and cell viability is prolonged.

Animals↗
PubMed1991

HgCl2-induced alteration of actin filaments in cultured primary rat proximal tubule epithelial cells labelled with fluorescein phalloidin.

When proximal tubule epithelial cells are exposed to HgCl2, cytoplasmic blebs are formed. These represent an early, potentially reversible response to injury. These blebs are accompanied by reorganization of cytoskeletal proteins, and presumably by alternations in cytoskeletal-plasma membrane interactions. Ca(2+)-activated proteinases, such as calpain, are known to affect cytoskeletal proteins and to be involved in diverse cellular processes. However, the role of calpains in cytotoxicity due to HgCl2 is unknown. To determine the relationship between F-actin, calpain, and HgCl2 toxicity, cells were stained with fluorescein phalloidin before and after treatment with HgCl2. Cells were grown on coverslips and exposed to HgCl2 (10 or 25 microM) in the presence or absence of the calpain inhibitor, leupeptin. Untreated cells were flat, polygonal, and contained many fluorescent-stained cables of actin filaments. Generally, cells exposed to HgCl2 became pleomorphic and contracted as the blebs formed. These cells showed fewer actin cables and fluorescence was seen mostly as either compact areas of dense stain or as peripheral rings. In many cells, actin cables and filaments were completely absent. Disappearance of F-actin was initially seen by 2 min after exposure to HgCl2. Thus, disruption of the actin cytoskeleton and blebbing were found to be early events in HgCl2 toxicity. When leupeptin was used with HgCl2 treatment, the actin staining appeared similar to that of untreated cells.

Actins↗
PubMed1991

Primary cultures of normal rat kidney proximal tubule epithelial cells for studies of renal cell injury.

Normal rat kidney proximal tubule epithelial cell cultures were obtained by collagenase digestion of cortex and studied for 10 days. To assess the purity of the seeding suspension, we histochemically demonstrated gamma-glutamyltranspeptidase in greater than 95% of the starting material. To identify cell types in cultures, we investigated several markers. Cells stained positively for lectin Arachis hypogaea (rat proximal tubule) and negatively for Lotus tetragonolobus (rat distal tubule). Intermediate filament expression of cytokeratin confirmed the epithelial differentiation of the cultured cells. Using indirect immunofluorescence, we found that cultures were negative for vimentin and Factor VIII. Cells exhibited activities of two brush border enzymes, gamma-glutamyltranspeptidase and leucine aminopeptidase, and Na(+)-dependent glucose transport activity. Multicellular domes were evident in the Week 2 of culture. Proliferation was studied by comparing growth factor-supplemented serum-free medium to cells grown in serum; growth enhancers included insulin, hydrocortisone, transferrin, glucose, bovine albumin, and epidermal growth factor. Cells proliferate best in medium with 5 or 10% serum and in serum-free medium supplemented with insulin, hydrocortisone, transferrin, glucose, and bovine albumin. Proliferation was assessed by determining cell number (population doublings). By light microscopy, the cells were squamous with numerous mitochondria, a central nucleus, and a rather well-defined homogeneous ectoplasm. By electron microscopy, the cells were polarized with microvilli and cell junctions at the upper surface and a thin basal lamina toward the culture dish. These data show that the proximal tubule epithelial cells retain a number of functional characteristics and that they represent an excellent model for studies of normal and abnormal biology of the renal proximal tubule epithelium.

Animals↗
PubMed1991

Oxidative injury induces influx-dependent changes in intracellular calcium homeostasis.

Understanding of the mechanisms of cell injury and cell death is fundamental to the understanding of both protection against and initiation of cell injury and cell death. We subjected primary cultures of proximal tubular epithelium (PTE) from adult rats to an exogenous oxidative stress, generated by xanthine/xanthine oxidase (X/XOD), and studied its effect on the concentration of cytosolic ionized calcium ([Ca2+]i) by means of digital imaging fluorescence microscopy (DIFM) using a cytosolic calcium probe, fura-2. Exposure to 25 mU/ml X/XOD caused notable increases in [Ca2+]i detectable within 15 sec and increasing to micromolar levels with time. Experiments with Ca(2+)-free medium containing ethylene glycol-bis(beta-aminoethyl ether)N,N,N',N'-tetraacetic acid (EGTA) showed that the increase of [Ca2+]i was due to influx from the extracellular space. Smaller and slower increases in [Ca2+]i were seen after exposure to lower concentrations of X/XOD (5 and 10 mU/ml). PTE injury and killing were assessed by measuring the release of cytosolic lactate dehydrogenase (LDH), exclusion of trypan blue, and observation of morphologic changes. Exposures to the 25 mU/ml concentration of X/XOD caused significant LDH release after 2 hr and correlated with trypan blue staining of exposed cells. Again, lesser concentrations of X/XOD resulted in a slower release of smaller amounts of LDH, and thus delayed trypan blue staining. Cytoplasmic bleb formation was seen by phase microscopy within minutes of exposure to 25 mU/ml, followed by cell rounding, retraction, and disintegration. Transmission electron microscopy revealed a progression of changes characteristic of lethal cell injury, beginning with dilatation of the endoplasmic reticulum, detachment of ribosomes, condensation of mitochondria, and chromatin clumping and terminating with mitochondrial swelling and formation of intramitochondrial flocculent densities. These studies clearly show that notable increases of [Ca2+]i precede both sub-lethal and lethal changes in rat PTE. These results indicate that interventions designed to minimize or to accelerate calcium entry could be of importance in cell preservation or cell killing, respectively, and therefore to therapeutic strategies for myocardial infarction, stroke, or shock in the former instance and for cancers in the latter.

Animals↗
PubMed1991

Role of oncogenes and tumour suppressor genes in human lung carcinogenesis.

Six families of activated protooncogenes, ras, raf, fur, neu, jun and myc have so far been associated with human lung cancer. Human bronchial epithelial cells in vitro are being used to investigate the functional role of these specific oncogenes and growth regulatory genes in carcinogenesis and tumour progression. When transferred into normal human bronchial epithelial cells by the highly efficient protoplast fusion method, the v-Ha-ras oncogene initiates a cascade of events leading to decreased responsiveness of these cells to inducers of squamous differentiation, aneuploidy and, less frequently, 'immortality' and tumorigenicity with metastasis in athymic nude mice. Transfection of the SV40 T antigen gene results in nontumorigenic cell lines that have a nearly normal pathway of terminal squamous differentiation and can be transformed into malignant cells by transfected Ha-ras, N-ras or Ki-ras. The combination of transfected c-myc and c-raf-1 also transforms human bronchial epithelial cells into neoplastic cells that exhibit some phenotypic traits found in small-cell carcinomas. These and other results indicate that proto-oncogenes dysregulate the pathways of growth and differentiation of human bronchial epithelial cells and play an important role in human carcinogenesis. Analyses of allelic deletion and somatic cell hybrids are being used to identify the chromosomal localization of tumour suppressor genes. We have examined 54 non-small-cell bronchogenic carcinomas with 13 polymorphic markers. Loss of heterozygosity was more frequent than among 23 squamous-cell carcinomas than among 23 adenocarcinomas or eight large-cell carcinomas. Loss of heterozygosity for chromosome 17p was found in 89% of cases of squamous-cell carcinoma and 18% of adenocarcinomas. Analysis of chromosome 11 for allelic deletions revealed two commonly deleted regions (11p13 and 11p15.5). Somatic cell hybrids between normal human bronchial epithelial cells and Hut292DM, a lung carcinoma cell line, had a finite lifespan in vitro and were nontumorigenic in athymic nude mice. Tumour suppressive effects of individual or combinations of specific human chromosomes on Hut292DM are being examined by formation of microcell-cell hybrids. Chromosome 11 has tumour suppressor activity in these hybrids. Both of these studies suggest that tumour suppressor genes play a dominant role in lung carcinogenesis and provide in-vitro model systems for isolating these genes by subtraction library and insertional mutagenesis techniques.

Bronchi↗
PubMed1991

Archival analysis of p53 genetic and protein alterations in Chinese esophageal cancer.

A strategy and methods for archival analysis of genetic and protein alterations in the p53 tumor-suppressor gene are presented. The tumor series includes 43 paraffin-embedded esophageal carcinomas from two high-incidence regions in the People's Republic of China. More than half contained elevated p53 protein levels which were detected by a high-titer polyclonal antiserum and a sensitive immunohistochemical method. To estimate the frequency of underlying mutations, DNA was isolated from conventional paraffin sections, amplified by the polymerase chain reaction, and examined by dideoxy termination sequencing. Analysis of exons 5-8 in a subset of 10 tumors revealed mis-sense point mutations in 4 out of 5 immunostain-positive tumors and a mutation encoding a stop codon in 1 of 5 immunostain-negative tumors. In this report of archival material, we conclude that detectable levels of p53 protein correlate closely with the occurrence of mis-sense mutations. Furthermore, these methods render large repositories of paraffin-embedded tumor and non-tumor tissues accessible to analysis. Immunohistochemical screening for elevated protein levels followed by sequence analysis represents an efficient strategy for the evaluation of the p53 mutational spectrum.

Adenocarcinoma↗