Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: UMLS:C0345904 (liver cancer)
15,188 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Aberrations of the p53 gene were observed in high frequency in HCCs in China, Mozambique and Japan. Most of the mutations were G to T transversions in codon 249 of the p53 gene in HCCs in China and Mozambique, where aflatoxin B1 was a risk factor. These findings strongly suggest that aflatoxin B1 induced this type of mutations. On the other hand, in Japanese HCCs, no mutation was observed in codon 249, indicating a different cause of HCC development. Pathological analyses revealed that p53 mutations were detected only in advanced HCCs and not in early HCCs. In addition, aberrations of the RB gene were observed in only tumors carrying mutated p53 gene. These results indicate the involvement of at least two tumor suppressor genes in a late stage of hepatocarcinogenesis. Possible mechanisms of HCC formation are discussed.
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PMID:[Co-inactivation of the p53 and RB genes in human hepato cellular carcinoma]. 809 51

To examine the significance of mutation of the p53 tumour suppressor gene in the development of human hepatocellular carcinoma in a high-prevalence area for hepatitis B viral infection but a low-exposure area for aflatoxin B1, the spectrum of p53 gene mutations was examined in 21 tumour samples from Hong Kong Chinese patients, all of whom were HBsAg positive. DNA sequencing covering exons 5 to 9 of the p53 gene and Hae III restriction enzyme digestion for preliminary assessment of mutation at codon 249 were performed. Immunohistochemical staining with anti-p53 monoclonal antibodies was done on both tumour and nontumour liver tissues. Six tumours (28.6%) showed a p53 mutation and all were point mutations. Of the six point mutations, two (9.5%) were at codon 249 and both were G to T transversions (AGG-->ATG and AGG-->AGT transversions). The remaining point mutations were transversions scattered at codon 172 (exon 5), 214 (exon 6), 273 (exon 8) and 330 (exon 9). Mutated p53 protein was detected in five of these six cases with demonstrable point mutations by DNA sequencing, in contrast to none detected in all of the 15 cases without demonstrable point mutations. The presence of p53 mutations, including those at codon 249, did not show a significant association with tumour size, sex, age, tumour invasiveness in terms of liver invasion, microsatellites and venous permeation, cirrhosis and encapsulation, but tumours with low cellular differentiation tended to have a higher incidence (71%) of point mutations than those with high cellular differentiation (8%). In conclusion, both the overall p53 mutation rate and that a codon 249 in HCC in Hong Kong Chinese are lower than those reported in tumours from China and sub-Saharan Africa. The low mutation rate at codon 249 is compatible with a low aflatoxin exposure. A special type of p53 mutation has not been found to be associated with hepatitis B viral infection. Mutations of p53 gene tends to occur in tumours with low cellular differentiation, suggesting a late occurrence in the event of tumour progression.
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PMID:p53 gene mutation spectrum in hepatocellular carcinomas in Hong Kong Chinese. 810 45

Hepatocellular carcinoma samples obtained from 59 patients at surgical resection were examined for mutations of the third base at codon 249 of the p53 gene, using the polymerase chain reaction and oligonucleotide hybridization techniques. This point mutation, which is frequently observed in HCC cases from Southern Africa and Quidong in China, was not recognized in either 60 hepatocellular carcinomas or 53 noncancerous liver tissue samples from Japan. Thirty-four of 45 patients (75.6%) were positive for the hepatitis C virus, which was a higher rate than that for hepatitis B virus infection (9 of 55; 16.4%). The exposure to aflatoxin B1 was not considered to be remarkable. These results suggest that the point mutation of the third base at codon 249 is not common in Japanese patients, and it is suggested that numerous other factors affect the mutation of the p53 gene and the development of hepatocellular carcinoma.
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PMID:The mutation of codon 249 in the p53 gene is not specific in Japanese hepatocellular carcinoma. 825 41

The tumor suppressor p53 exerts important protective functions towards DNA-damaging agents. Its inactivation by allelic deletions or point mutations within the P53 gene as well as complex formation of wildtype p53 with cellular or viral proteins is a common and crucial event in carcinogenesis. Mutations increase the half-life of the p53 protein allowing the immunohistochemical detection and anti-p53 antibody formation. Distinct G to T point mutations in codon 249 leading to a substitution of the basic amino acid arginine by the neutral amino acid serine are responsible for the altered functionality of the mutant gene product and were originally identified in 8 of 16 Chinese and 5 of 10 African HCC patients. Both groups are frequently exposed to mycotoxin contaminations of their food. Today an average P53 gene mutation rate of 25% is assumed for high-aflatoxin B1-exposure regions. This is double the rate observed in low-aflatoxin B1-exposure countries. Although many HCC patients displaying P53 mutations also suffer from HBV infection, which itself can lead to rearrangements of P53 coding regions or induce the synthesis of viral proteins possibly interacting with p53, the specific G to T transversion within codon 249 of the P53 gene seems to directly reflect the extent of aflatoxin B1 exposure.
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PMID:Point mutations of the P53 gene, human hepatocellular carcinoma and aflatoxins. 830 Oct 66

In hepatocellular carcinoma, mutation within the p53 gene occurs mainly at codon 249 and its frequency has been associated with exposure to aflatoxin. As Senegal is a country where liver cancer incidence is one of the highest in the world and where people are highly exposed to aflatoxin, we screened 15 liver cancer samples from this country for mutation at codon 249 of the p53 gene. Non-tumoral DNA from the patients showed a wild type genotype. Mutation at codon 249 of the p53 gene was detected in 10 of the 15 tumour tissues tested (67%). This frequency of mutation in codon 249 of the p53 gene is the highest described. These results confirmed that there is an association between countries of high aflatoxin intake and a high frequency of mutation in codon 249 of p53 gene, and that HBV alone does not contribute to these base changes.
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PMID:High prevalence of mutations at codon 249 of the p53 gene in hepatocellular carcinomas from Senegal. 839 Feb 89

Loss of heterozygosity (LOH) on chromosomes 1p, 4q, 5q, 8p, 13q, 16q, 17p, and 22q, and mutation of the p53 gene were simultaneously analyzed in 63 hepatocellular carcinomas (HCCs) with distinct histopathological grades, 80% of the tumors being from patients who had been exposed to hepatitis B virus (HBV) or hepatitis C virus (HCV). The frequencies of LOH on 8 chromosomes were 0-25% in 10 well differentiated HCCs, LOH being observed on 4q, 5q and 17p, 21-53% in 26 moderately differentiated HCCs, LOH on 8p and 17p being high, and 29-75% in 27 poorly differentiated HCCs, LOH on 17p, 4q and 8p being the most frequent. p53 gene mutation was detected in moderately and poorly differentiated HCCs at 15% and 52%, respectively, but not at all in well differentiated HCCs. Of the mutations detected, 42% were transition mutation and only 5% were CpG transition, in contrast to the high frequencies of these types of mutations in colon tumors (78% and 54%, respectively). LOH on every chromosome and p53 mutation were more frequent in more advanced tumors, and accumulation of genetic changes increased with increase of the histopathological grade. Frequency of genetic changes in HCCs from HBV-positive patients was comparable to that from HCV-positive patients. The present results suggest that accumulation of genetic changes in multiple tumor suppressor genes, especially LOH on 17p, 4q and 8p, and mutation in p53 gene, are involved in the progression of liver cancer, and LOH on 17p and 4q precedes other genetic changes. Differences in the direction of p53 mutation between HCC and colon carcinoma suggest that liver carcinogens are distinct from colon carcinogens. Furthermore, mechanisms affecting the frequency of LOH in HCCs in HBV-infected patients may be similar to those in HCV-infected patients.
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PMID:Genetic changes and histopathological grades in human hepatocellular carcinomas. 840 53

The molecular role of hepatitis C virus (HCV) in liver disease has yet to be clarified. In this study, we analyzed the relationship of HCV replication with mRNA expression of growth factors and mutation of tumor suppressor gene, ie, transforming growth factor-beta 1 (TGF-beta 1), which promotes cirrhotic changes; TGF-alpha, insulin-like growth factor-II (IGF-II), which are both related to hepatocyte transformation; and tumor suppressor gene p53, which is associated with HCC progression. A semiquantitative RNA polymerase chain reaction (RNA-PCR) was used to analyze genetic expression in 31 cirrhotic liver specimens from patients with HCV. In order to detect HCV replication, the minus-strand RNA of HCV, which serves as a template for the synthesis of genomic plus-strand RNA, was examined. The expression of the growth factors was semiquantified by RNA-PCR, and the mutation of p53 was detected using PCR-single-strand conformation polymorphism. According to the semiquantitative analysis, HCV replication was not associated with the expression of TGF-beta 1 but was significantly so with the overexpression of TGF-alpha (r = 0.74) and IGF-II (r = 0.65) in the HCV-positive cirrhotic livers. No mutation of p53 was recognized in any of the samples. Our investigation thus suggested that the replication of HCV might mediate the coexpression of TGF-alpha and IGF-II and act as a possible initiating factor for hepatocarcinogenesis.
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PMID:Hepatitis C virus replication is associated with expression of transforming growth factor-alpha and insulin-like growth factor-II in cirrhotic livers. 856 58

A series of 60 cases of oxyphilic (Hurthle cell) carcinomas (HCC) of the thyroid were reviewed to determine whether it is possible to correlate morphologic and clinical features as a means of assessing prognosis. Twenty cases showing predominant solid or trabecular patterns (as described in poorly differentiated carcinomas with a follicular pattern) were selected and the clinicopathological features were investigated. Based on cell size, two groups of solid or trabecular HCCs were identified: The first group (17 cases) was made up of typical large granular oxyphilic cells, and the second (three cases) had small oxyphilic cells. All tumors were reactive for thyroglobulin and for a mitochondrial antigen, selectively marking oxyphilic, mitochondrial-rich cells. Nuclear pleomorphism in individual cells was a common feature, but foci of anaplastic carcinoma were never found. Four cases overexpressed p53 protein and 10 expressed bcl-2 gene product. At follow-up, among the high-stage (pT3-pT4) tumors, seven patients had recurrences or metastases, six of whom were alive with disease or died of disease. In the control group of HCC with predominant follicular patterns, only one of 40 cases had a fatal outcome. The difference was statistically significant. Small-cell patterns and a p53 protein-positive/bcl-2 gene product negative phenotype were features of clinically aggressive HCC cases. We suggest that within the spectrum of oxyphilic (Hurthle cell) tumors, poorly differentiated HCC showing solid or trabecular patterns are a distinct group, based on both morphological and clinical features.
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PMID:Poorly differentiated oxyphilic (Hurthle cell) carcinomas of the thyroid. 865 47

Immunohistochemistry (ABC method) and in situ hybridization (DNA-RNA) were used to detect c-myc and p53 gene expression in tissues of human HCC and nearby non-tumorous liver (NT) from 23 patients. The results showed that the positive rates of P62c-myc were 87% (20/23) in HCC and 91% (21/23) in NT. The positive rates of P53 protein were 39% (9/23) in HCC as well as in NT. The positive rates of c-myc and p53 mRNA were 70% (16/23) and 56% (13/23) in HCC and NT respectively. The expression of c-myc and p53 at protein level was significantly correlated with that at mRNA level. These observations suggest a close association of c-myc and p53 gene overexpression with hepatocarcinogenesis. Immunohistochemistry (ABC method) on section of paraffin embedded tissue is a reliable method for detecting c-myc and p53 gene expression in HCC.
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PMID:[Overexpression of c-myc and p53 gene in human hepato-cellular carcinoma--a study with immunohistochemistry and in situ hybridization]. 869 90

Carcinogenesis is a multistage process involving the inappropriate activation of normal cellular genes to become oncogenes, e.g., ras, and the inactivation of other cellular genes called tumor suppressor genes. p53 is the prototypic tumor suppressor gene that is well suited as a molecular link between the causes of cancer, i.e., carcinogenic chemical and physical agents and certain viruses, and the development of clinical cancer. The p53 tumor suppressor gene is mutated in the majority of human cancers. Genetic analysis of human cancer is providing clues to the etiology of these diverse tumors and to the functions of the p53 gene. Some of the mutations in the p53 gene reflect endogenous causes of cancer, whereas others are characteristic of carcinogens found in our environment. In geographic areas where hepatitis B virus and a dietary chemical carcinogen, aflatoxin B1, are risk factors of liver cancer, a molecular signature of the chemical carcinogen is found in the mutated p53 gene. A different molecular signature in the p53 gene is found in skin cancer caused by sunlight. Because mutations in the p53 gene can occur in precancerous lesions in the lung, breast, esophagus, and colon, molecular analysis of the p53 gene in exfoliated cells found in either body fluids or tissue biopsies may identify individuals at increased cancer risk. p53 mutations in tumors generally indicate a poorer prognosis. In summary, the recent history of p53 investigations is a paradigm in cancer research, illustrating both the convergence of previously parallel lines of basic, clinical, and epidemiologic investigation and the rapid translation of research findings from the laboratory to the clinic.
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PMID:p53 tumor suppressor gene: at the crossroads of molecular carcinogenesis, molecular epidemiology, and cancer risk assessment. 878 59


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