Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0596263 (carcinogenesis)
 64,820 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The bcl-2 proto-oncogene is activated by translocation in a variety of B-lymphoid tumours and synergizes with the c-myc oncogene in tumour progression. The mechanism of synergy is unclear but bcl-2 expression inhibits apoptosis, a property presumably pertinent to its proto-oncogenic mode of action. We have shown that the c-myc gene is a potent inducer of apoptosis, in addition to its established role in mitogenesis. Here we show that expression of the bcl-2 protein, Bcl-2, specifically abrogates c-myc-induced apoptosis without affecting the c-myc mitogenic function. This provides a novel mechanism for oncogene cooperation, of potential importance both in carcinogenesis and in the evolution of drug resistance in tumours.
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PMID:Cooperative interaction between c-myc and bcl-2 proto-oncogenes. 140 76

Nonrandom patterns of chromosome abnormality in tumors are providing clues to the location of oncogenes and their activation mechanisms. Studies of translocations in Burkitt's lymphoma cells have shown that the c-myc proto-oncogene is consistently juxtaposed with a rearranged and transcriptionally active immunoglobulin gene locus, with resultant myc gene deregulation. In other B cell tumors, translocations appear to bring previously unrecognized oncogenes (bcl-1, bcl-2) into similar association with the immunoglobulin heavy-chain locus. T cell receptor genes may also "activate" known and unknown oncogenes after chromosome translocation. In chronic myelogenous leukemia, the translocated c-abl oncogene forms a "hybrid" gene in its new location on the Philadelphia chromosome, with altered function. Gene amplification units, seen as cytogenetically homogeneous staining regions in chromosomes or as double-minute bodies in metaphases, can represent multiple copies of oncogenes and be important in late stages of tumor progression. Other significant alterations in gene dosage, recognized as gain or loss of all or part of a specific chromosome, also occur in human neoplasms, but their specific role in carcinogenesis is largely undefined.
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PMID:Chromosomal approaches to the molecular basis of neoplasia. 332 6

To better understand the molecular basis of radiation-induced cell death, we studied the role of the bcl-2 oncogene and the p53 tumor suppressor gene in this process. A temperature-sensitive mutant of murine p53 (p53Val-135) and/or bcl-2 was transfected into murine erythroleukemia cells (MEL, DP16-1, which are null in p53). We demonstrate that radiation-induced cell death occurs by both p53-dependent and -independent pathways and overexpression of bcl-2 modulates both pathways. When viability was measured 24 h post-radiation, cells that had been briefly exposed to wtp53 immediately after X-ray irradiation had decreased survival as compared to unirradiated cells expressing wtp53 or X-ray irradiated DP16-1 cells. However, at later times X-ray irradiated parental DP16-1 cells also had decreased survival compared to the unirradiated control. This decrease in survival began 48 h following radiation. Bcl-2 prevented radiation-induced cell death in DP16-1 cells expressing wtp53 and delayed radiation-induced cell death in DP16-1 cells without wtp53. X-ray irradiated cells expressing wtp53 displayed microscopic and biochemical characteristics consistent with cell death due to apoptosis. DP16-1 cells which were untransfected or co-transfected with wtp53 and bcl-2 displayed characteristics of cells undergoing necrosis. These results suggest that radiation-induced cell death occurs by both p53-dependent and p53-independent pathways. The p53-dependent pathway results in cell death via apoptosis and occurs approximately 24 h following radiation. The p53-independent pathway does not appear to involve apoptosis and occurs at a later time, starting 48 h after X-ray exposure. Thus, bcl-2 protects cells from p53-dependent radiation-induced apoptotic cell death and attenuates p53-independent radiation-induced cell death.
Carcinogenesis 1995 Aug
PMID:Bcl-2 protects murine erythroleukemia cells from p53-dependent and -independent radiation-induced cell death. 763 1

Gastric cancer involves changes in multiple oncogenes and multiple suppressor genes, and it causes genetic instability. Aberrant expression and amplification of the c-met gene, inactivation of the p53 gene, and CD44 abnormal transcripts are common events of both well differentiated and poorly differentiated gastric cancers. Amplification of the cyclin E gene is also observed in gastric cancer regardless of histologic type. Decreased expression of the pic1 (p21) gene occurs independent of the p53 mutations. In addition, K-ras mutations, c-erbB-2 gene amplification, loss of heterozygosity (LOH) and mutations of the APC gene, LOH of the bcl-2 gene, and LOH at the DCC locus are preferentially associated with well differentiated gastric cancer. Moreover, LOH on chromosome 1q is involved in the progression of well differentiated cancer. Precancerous lesions, including hyperplastic polyp, intestinal metaplasia, and adenoma, share genetic changes found in well differentiated cancers. Conversely, genetic instability may be involved in the first step of stomach carcinogenesis of the poorly differentiated type. Reduction or loss of cadherin and catenins, K-sam gene amplification, and c-met gene amplification are necessary for the development and progression of poorly differentiated or scirrhous carcinoma. Interaction between cell-adhesion molecules in the c-met expressed tumor cells and hepatocyte growth factor from stromal cells is implicated in the morphogenesis of two types of gastric cancer.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Molecular biology of gastric cancer. 767 88

Bcl-2 protein expression has been found to block apoptosis and its overexpression has been implicated in lymphoid malignancies where the chromosomal translocation t(14;18) is present. In this study we investigated bcl-2 transcription and protein expression in cultured cervical carcinoma cell lines and keratinocytes. Western blotting and immunofluorescence microscopy demonstrated bcl-2 expression in the cytoplasm of 4 out of 5 cervical carcinoma cell lines examined (HeLa, CaSki, C-33A, and HT-3, but not SiHa). Bcl-2 protein expression was undetectable in normal keratinocytes. None of the cell lines examined demonstrated chromosomal translocation or rearrangement at the major breakpoint-cluster region (MBR) of the bcl-2 gene using either Southern blot or polymerase chain reaction (PCR) analyses. Northern blot analysis demonstrated low levels of bcl-2 transcription in HeLa, CaSki, and C-33A cell lines while reverse transcriptase (RT)-PCR demonstrated bcl-2 transcription in all cervical carcinoma cell lines which had bcl-2 protein expression. Thus, these data suggest that bcl-2 expression occurs in cervical carcinoma cell lines in the absence of chromosomal translocation or rearrangement of the bcl-2 gene. However, each of these cervical carcinoma cell lines contains inactive p53, either due to mutation (C-33A and HT-3) or via complexation and degradation with human papillomavirus (HPV) 16/18 E6 protein (HeLa and CaSki). Thus, functional p53, which can induce apoptosis in certain cells, is not present in these cervical cells which have increased bcl-2 expression. Increased bcl-2 expression under conditions of p53 inactivation may provide cells with a selective advantage for survival and consequently play a role in the development of cervical carcinogenesis.
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PMID:Bcl-2 protooncogene expression in cervical carcinoma cell lines containing inactive p53. 776 85

A proto-oncogene, bcl-2, encodes a protein that inhibits programmed cell death (apoptosis) and may play a role in cell and tissue differentiation. As bcl-2 appears to be involved in the turn-over of stem or precursor cells, it is thought to be operational in carcinogenesis pathways. However, apart from certain lymphomas, only limited data are available on the frequency of its expression in solid tumors. Immunohistochemical analysis with an antibody specific for bcl-2 protein was used to detect the protein in hepatocellular carcinomas and in one of the putative precursor lesions, liver cell dysplasia. We detected bcl-2 protein in 5 of 37 hepatocellular carcinomas. Immunoreactivity was not related to type, grade, or extent of PCNA staining of the tumours. No bcl-2 protein staining was observed in three types of liver cell dysplasia. Thus, bcl-2 is abnormally expressed in some hepatocellular carcinomas but not in potential tumour precursor cells.
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PMID:Immunohistochemical detection of bcl-2 protein in liver lesions: bcl-2 protein is expressed in hepatocellular carcinomas but not in liver cell dysplasia. 782 91

The bcl-2 gene provides a window on the basic cellular machinery of apoptosis or programmed cell death, a process involved in virtually all biologic events in multicellular organisms, but particularly relevant to neoplasia and development. bcl-2 gene function supports cell survival and appears to lie at a nodal point in pathways leading to activation or execution of apoptosis. Carcinogenesis may involve several steps at which cell death programs are normally activated and are bypassed in cancer cells, including apoptotic pathways activated by several oncogenes. Functional redundancy and the complexity of the regulation of cell survival are demonstrated by the less than expected phenotype of bcl-2 knockout mice and the cloning of several bcl-2 related genes, some of which promote cell death. The molecular function for bcl-2 is unknown, but several lines of evidence support a role in protection from oxidative stress. These studies suggest that many environmental perturbations and genetic pathways converge to disrupt a metabolic balance between oxidant generation and anti-oxidant defenses.
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PMID:bcl-2 in cancer, development and apoptosis. 788 92

Apoptosis is a kind of programmed cell death, that is, intrinsically programmed "cell suicide process". Mammalian thymic lymphocytes, thymocytes, show a typical apoptosis immediately after a low dose irradiation. Apoptosis appears also during radiotherapy of tumor, especially of thymoma. Tumor suppressor gene such as p53 and oncogene such as bcl-2 are found to be closely related to apoptotic processes in a cell. Possible mechanisms underlying interrelationship between expression of these genes, apoptosis and carcinogenesis were discussed.
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PMID:[Radiation and apoptosis]. 815 85

Several recent studies have implicated oncogenes and tumour suppressor genes in the regulation of programmed cell death (apoptosis). Lesions in the cell death pathway appear to be important in both carcinogenesis and the evolution of drug resistance in tumours. They include deregulated expression of genes such as bcl-2, loss of p53, and autocrine activation of anti-apoptotic signal transduction pathways. Paradoxically, a number of dominant oncogenes appear to act as potent inducers of apoptosis. This suggests that the pathways of cell proliferation and cell death may be tightly coupled, an idea that may have dramatic implications for models of oncogene co-operation and carcinogenesis.
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PMID:Oncogenes and cell death. 819 31

Cloning of the t(14;18) translocation breakpoint resulted in the identification of a new putative oncogene, which mapped to 18q21, termed bcl-2. The t(14;18) resulted in inappropriately high levels of bcl-2 expression in follicular lymphoma. Prospective studies using mice transgenic for a human bcl-2-immunoglobulin minigene, intended to recreate the molecular features of the t(14;18), demonstrated that bcl-2 gene deregulation was oncogenic. Interestingly, overexpression of bcl-2 showed no demonstrable influence on rates of cellular proliferation. Rather, bcl-2 was found to extend cellular viability by blocking apoptosis. Recent studies with other oncogenes and tumor suppressor genes, such as c-myc and p53, have demonstrated that the deregulation of apoptosis may be of general significance in the development of multiple types of cancer and appears to be a critical event during multistep carcinogenesis. The selective induction of apoptosis in tumor cell populations is now being considered in the design of novel therapeutic interventions.
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PMID:The bcl-2 oncogene: apoptosis and neoplasia. 827 71


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