Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P43146 (tumour suppressor)
 5,935 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In comparison with primary cell cultures, SV40-transformed human skin fibroblasts, either from healthy donors or from patients suffering from ataxia-telangiectasia (AT) or xeroderma pigmentosum, are more resistant to the cytotoxic action of low LET 60cobalt gamma-rays as well as to high LET alpha-particles. Resistance factors calculated from D10's lie between 1.4 and 2.0. Northern blot analysis reveals spontaneous overexpression of the oncogenes c-myc, Ki-ras and c-raf and of the tumour suppressor gene p53 as a consequence of SV40 transformation. For c-myc, the increased expression is due to gene amplification and gene rearrangement. An even further increase in the expression of c-myc has been found for AT cells (AT5BI-VA) after moderate doses of 60cobalt gamma-irradiation. A possible correlation between SV40-induced changes in gene expression and cellular radioresistance is discussed.
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PMID:Alterations in oncogene expression and radiosensitivity in the most frequently used SV40-transformed human skin fibroblasts. 791 16

Lysyl oxidase (EC 1.4.3.13), a copper-dependent enzyme which catalyses the formation of aldehyde cross-links, and acts primarily on collagen and elastin, is known to be increased during wound healing and in fibrotic disorders including liver cirrhosis and atherosclerosis, and to be decreased in some hereditary connective tissue diseases and in malignant cell lines. A recent study showed that lysyl oxidase might possess tumour suppressor activity as an antioncogene for ras. Little is known about the localization of this enzyme in human skin. In this study, we determined immunohistochemically the localization of lysyl oxidase in normal skin of young and elderly subjects obtained from sun-exposed and unexposed regions of the body. All skin samples tested had similar distributions of lysyl oxidase. The enzyme was present both extracellularly and intracellularly. Extracellularly, a few granular aggregates of immunoreactants were observed along collagen and elastic fibres. These granules were more common in the adventitial portion of the dermis than in the reticular portion. Of all sun-exposed and unexposed regions studied, the skin of the face displayed the greatest amount of extracellular immunoreactants. Immunopositive granules were observed intracellularly in fibroblasts, vascular endothelial cells, sweat glands, sebaceous glands, arrector pili muscles and some keratinocytes. These findings provide evidence that, as suggested in recent reports, lysyl oxidase may have a variety of intracellular functions.
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PMID:Immunohistochemical localization of lysyl oxidase in normal human skin. 791 5

Mutations in oncogenes and tumour suppressor genes may have an important oncogenic role. Although flat type tumours have been frequently detected in recent years, ras and p53 expressions have not been studied in these tumours. Using a monoclonal and polyclonal antibody to the ras p21 and p53 product, paraffin wax embedded sections of 98 colorectal tumours (43 cases of the flat type colorectal tumour and 55 cases of polypoid type tumour) were stained using the immunoperoxidase technique. Staining was evaluated by light microscopic examination. Positive staining rate of ras p21 for the flat type was 0%; for the polypoid type, it was 60% in cancer with submucosal invasion, 82% in adenoma with high grade dysplasia, and 0% in adenoma with low grade dysplasia. The positive staining rate of p53 for the flat type was 50% in submucosal cancer, 9% in adenoma with high grade dysplasia, and 0% in adenoma with low grade dysplasia. For the polypoid type, it was 40% in submucosal cancer, 12% in adenoma with high grade dysplasia, and 0% in adenoma with low grade dysplasia. The intermediate staining rate of p53 in the polypoid type was 20% in submucosal cancer and 41% in adenoma with high grade dysplasia. It was seen that p53 was commonly expressed in both flat and polypoid lesions, p21 was not expressed in flat lesions, whereas it was commonly expressed in polypoid neoplasms. In the flat type cancer, a genetic change different from that of the polypoid type cancer is suggested.
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PMID:Comparative clinicopathological and immunohistochemical study of ras and p53 in flat and polypoid type colorectal tumours. 795 33

Our study was undertaken to determine the prognostic significance of several common genetic alterations observed in colorectal carcinomas. We have previously analysed loss of heterozygosity of the MCC, APC, p53 and DCC tumour suppressor gene loci as well as p53 gene mutations and protein over-expression in a series of 100 Dukes' stage B and C colorectal tumours obtained at surgery. To extend our observations of alterations that may occur in these tumours, mutations to the c-Ki-ras oncogene and APC tumour suppressor gene were detected by PCR single-strand conformation polymorphism analysis. Short-term follow-up revealed no significant association between overall patient survival and any single, or combination of, genetic alteration(s). Surprisingly, patients whose tumours showed evidence of p53 protein over-expression/accumulation by immunocytochemistry (ICC) had a significantly better prognosis (p = 0.039) than those whose tumours had no p53 ICC reactivity.
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PMID:The common molecular genetic alterations in Dukes' B and C colorectal carcinomas are not short-term prognostic indicators of survival. 798 12

Very frequent loss of heterozygosity (LOH) on chromosome 3p has been found in human renal cell carcinoma (RCC). In the present study, we examined LOH at the retinoblastoma (RB), mutated in colorectal cancer (MCC) and adenomatous polyposis coli (APC) tumour suppressor genes loci, and mutations of the H-, K-, and N-ras oncogenes. We performed these studies using the polymerase chain reaction (PCR) method followed by restriction fragment length polymorphism (RFLP) and single-strand conformation polymorphism (SSCP) analyses. LOH was detected in 2 of 11 (18.2%), and 2 of 14 (14.3%) informative cases at the MCC and APC loci, respectively, and in none of 15 informative cases at the RB locus in 25 RCCs. LOH at the MCC was accompanied by LOH at the APC locus in two RCCs. No mutation was detected in H-, K-, and N-ras genes in 39 RCCs. Thus, alterations of the known tumour suppressor genes and the ras oncogenes were infrequent events in RCC. The results suggest that the genetic pathway in the genesis of RCC differs considerably from that of other common human carcinomas.
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PMID:Analysis of genetic alterations in renal cell carcinoma using the polymerase chain reaction. 781 22

Two distinct gene classes have been implicated in colorectal carcinogenesis. Tumour promoter genes (oncogenes, dominant oncogenes) produce an excessive positive stimulus to cell proliferation. The ras family of oncogenes are an example. Acquired mutations of the c-k-ras gene are commonly found in colonic adenomas and carcinomas. Tumour suppressor genes (anti-oncogenes, recessive oncogenes) normally constrain or regulate cell proliferation. Loss of this function through gene deletion or mutation is oncogenic. Inherited tumour suppressor gene mutations have now been identified in several of the familial cancer syndromes. Acquired tumour suppressor gene mutations are found in both sporadic and hereditary cancers. Together with the tumour promoter genes they provide the genetic basis for the cellular changes occurring during carcinogenesis. The retinoblastoma gene was the first human tumour suppressor gene to be characterized and exemplifies the class. More recently, linkage studies in the hereditary cancer syndromes and the detection of specific deletions in sporadic tumours have helped to identify several new tumour suppressor genes. At least four of these (MCC, APC, p53 and DCC) apparently contribute to sporadic colorectal carcinogenesis. Germ line APC mutations produce the inherited colorectal cancer syndrome familial adenomatous polyposis (FAP). Detection of these mutations using linked markers has already found clinical application in the screening of families with this disease. In the future, genetic diagnosis of hereditary non-polyposis colorectal cancer (HNPCC) and the recognition of those genetically susceptible to sporadic colorectal cancer may become possible. At the same time, as our understanding of the genes involved improves, new avenues for treatment and prevention of colorectal cancer may emerge.
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PMID:Tumour suppressor genes and colorectal neoplasia. 847 56

Most studies of the clonal origin of the underlying lesion(s) and all investigations using X-inactivation, have concluded that the myelodysplastic syndromes arise from a multipotent stem cell. Non-random chromosomal abnormalities, particularly deletions of 5q and 7q, are common, most notably in therapy related MDS. Progression to AML is also frequently accompanied by increased genomic instability as evidenced by the emergence of multiple karyotypic abnormalities. While some evidence hints at the presence of tumour suppressor genes on chromosomes 5, 7, 20 and 12, no such genes have yet been identified. The search for point mutations in known oncogenes has concentrated on two oncogenes RAS and c-FMS. Point mutation frequency generating active forms of RAS oncogenes is approximately 40% in MDS overall, up to 80% in studies of CMML. 60% of all MDS RAS mutation involves a G to A transition, producing a substitution of aspartate for glycine at a frequency of 50% (of total ras mutants). RAS mutation is associated with progression to AML, although the presence of a RAS point mutation alone is neither necessary nor sufficient for leukaemic transformation. Mutation of c-FMS is also more common in CMML in comparison to other MDS subtypes and, as yet, point mutation potentiating the response of the receptor to CSF-1 (codon 969) has been found more frequently than point mutation resulting in permanently activated receptor (codon 301). However, recent work has identified additional mutations which produce transforming proteins, and mutation rates at these sites may be relevant in MDS.
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PMID:Myelodysplastic syndromes: from morphology to molecular biology. Part II. The molecular genetics of myelodysplasia. 849 99

Neurofibromatosis type 1 (NF1) is a common autosomal dominant disorder characterized by progressive and variable involvement of tissues predominantly derived from the neural crest and a predisposition toward malignancies. The NF1 gene encodes neurofibromin, a GTPase-activating protein containing a GAP-related domain (NF1-GRD) that is capable of down-regulating ras by stimulating its intrinsic GTPase activity. We report a homozygous deletion of most of NF1 in one of eight malignant melanoma cell lines leading to loss of detectable mRNA and protein, as well as the apparent absence of protein and mRNA in another melanoma. This data suggests that NF1 can function as a tumour suppressor gene in the development or progression of malignant melanoma.
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PMID:Mutations in the neurofibromatosis 1 gene in sporadic malignant melanoma cell lines. 849 44

The transformation of the normal fully differentiated thyroid follicular cell to the rapidly growing undifferentiated anaplastic thyroid carcinoma cell involves a number of stages which have been defined morphologically and are now being related to various growth pathways and to molecular biological defects. The two main factors involved in this transformation are growth stimulation and mutagenesis. Growth stimulation alone, through elevated TSH, can lead to the development of thyroid tumours, usually benign, and retaining TSH dependency in some cases. Mutagens alone, if growth is suppressed, do not produce tumours, the combination of mutagens and increased growth is a potent carcinogenic regime. Non-genotoxic carcinogenesis in the thyroid involves growth, without mutagenesis the agent often causes this through affecting one component of thyroid hormone synthesis or metabolism, leading to a fall in thyroid hormone levels and a rise in TSH. Growth stimulation increases the rate of cell division, and therefore increases the chance of a mutation. Continued growth increases the change of subsequent events, in particular loss of heterozygosity in a tumour suppressor gene. The main oncogenes involved in human thyroid carcinogens are ras in the follicular tumour pathway, and ret in the papillary carcinoma pathway. p53 is involved in the progression of either papillary or follicular adenoma to an undifferentiated carcinoma. In experimental thyroid carcinogenesis, ras is again involved, with a link between the mutagenic agent used and the type of ras gene showing mutation. Analysis of the involvement of different growth factors and oncogenes in thyroid carcinogenesis suggests that genes related to the two receptors concerned with normal TSH stimulated growth, TSH receptor and the IGF1 receptor may be involved in the progression of thyroid tumours of follicular pathology. Several tyrosine kinase receptors with unknown ligands or of uncertain physiological function are linked to papillary carcinoma. The recent large increase in papillary carcinoma of the thyroid in children exposed to fallout from the Chernobyl nuclear accident underlines the importance of understanding the pathobiology of thyroid neoplasia.
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PMID:Mechanisms and pathogenesis of thyroid cancer in animals and man. 853 19

Proto-oncogenes, growth factors/receptors, and tumour suppressor genes were analysed in malignant metastatic insulinomas. Normal pancreas showed only a moderate immunoreaction for c-myc proto-oncogene and a strong reaction for insulin. Benign insulinomas were slightly or moderately positive for transforming growth factor alpha (TGF alpha), weakly positive for epidermal growth factor receptor (EGF-R), and strongly positive for c-myc and insulin. In malignant insulinomas, besides a strong immunoreaction for c-myc and TGF alpha, activation of c-K-ras and overexpression of p53 protein were found. Insulin reaction was moderate or strong. Three out of six malignant insulinomas displayed a c-K-ras point mutation at codon 12. All mutations were guanine to cytosine transversion, resulting in amino acid substitution, glycine to arginine. Mutations were present in metastatic insulinomas only. Patients with mutated c-K-ras oncogene had overexpression of p53 protein as well as c-myc and TGF alpha overexpression. Our results support the view that malignant progression is a consequence of more than one genetic lesion and suggest that activation of myc, TGF alpha an ras genes plays a role in a multistep process of tumour progression, perhaps serving as an initiating event.
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PMID:Multiple genetic alterations in malignant metastatic insulinomas. 856 94


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