UMLS:C0596263 - FACTA Search

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Query: UMLS:C0596263 (carcinogenesis)
64,820 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

HNPCC is an autosomal dominantly inherited disorder with proclivity to early onset colorectal cancer in the absence of multiple polyps of the colon. There is a predilection for proximal colonic location (70 per cent) and an excess of synchronous and metachronous colorectal cancers. HNPCC is subdivided into Lynch syndrome I, which is restricted to site-specific colon cancer susceptibility, and Lynch syndrome II, which shows all of the features of Lynch syndrome I, but in addition, patients are at inordinately increased risk for carcinoma of the endometrium, ovary, and other anatomic sites. The frequency of HNPCC is conservatively estimated to be 4 to 6 per cent of the total colorectal cancer burden. Because of the fact that the family history is underreported almost uniformly in medical practice, we believe that the true frequency of this disease may be much greater. Heterogeneity may be extant with respect to tumor association, in that in certain Lynch syndrome II kindreds, carcinoma of the pancreas, kidney, breast, and other anatomic sites may predominate. Knowledge of the natural history of HNPCC predicates surveillance and management strategies. Thus, because of the early onset of and proximal predilection for colorectal cancer, we recommend initiation of colonscopy at age 25 and annually thereafter. We also recommend guaiac testing of the stool at least twice a year. In the case of Lynch syndrome II, in addition to colonscopy, we recommend intensive surveillance for the endometrium, including aspiration biopsies. Other targeted organs, depending on the tumor spectrum in the family, should be given priority attention. Because of an excess of synchronous and metachronous colorectal cancer in HNPCC, subtotal colectomy with ileorectal anastomosis is the treatment of choice for initial colorectal cancer. In women presenting with initial colorectal cancer who have completed their families, consideration should be given to prophylactic hysterectomy and bilateral salpingo-oophorectomy at the time of surgery for colorectal cancer. Needed are biomarkers of acceptable sensitivity and specificity for the genotype, because HNPCC lacks premonitory physical signs. We believe that increased knowledge about colorectal cancer etiology and carcinogenesis can be attained through the study of families prone to the Lynch syndromes.
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PMID:Hereditary nonpolyposis colorectal cancer--Lynch syndromes I and II. 306 37

Mucinous carcinomas are defined on the basis of the amount of the mucus component in the tumour mass. Apart from this quantitative criterion, a number of clinicopathological parameters (such as localisation, prevalence in different countries and age groups, association with HNPCC and inflammatory processes) and genetic alterations (e.g. frequency of mutation in Ki-ras and p53 genes, level of MUC2 expression) differentiate these tumours from the non-mucinous ones. Since a different set of genetic lesions implies different inducing agents, these observations suggest that there may be a 'mucinous pathway of carcinogenesis'. Further identification of genetic changes characteristic of the mucinous phenotype will help to understand the aetiology of these tumours and possibly establish markers for detection of the high-risk group.
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PMID:Is mucinous carcinoma of the colorectum a distinct genetic entity? 851 44

Mismatch repair defects are carcinogenic. This conclusion comes some 80 years after the original description of a type of familial colorectal cancer in which mismatch repair defects are involved, and from decades of dedicated basic science research into fundamental mechanisms cells use to repair their DNA. Mismatch repair (MMR) was described first in bacteria, later in yeast and finally in higher eukaryotes. In bacteria, one of its roles is the rapid repair of replicative errors thereby providing the genome with a 100-1000-fold level of protection against mutation. It also guards the genome by preventing recombination between non-homologous regions of DNA. The information gained from bacteria suddenly became relevant to human neoplasia in 1993 when the RER phenotype of microsatellite instability was discovered in human cancers and was rapidly shown to be due to defects in mismatch repair. Evidence supporting the role of MMR defects in carcinogenesis comes from a variety of independent sources including: (i) theoretical considerations of the requirement for a mutator phenotype as a step in multistage carcinogenesis; (ii) discovering that MMR defects cause a 'mutator phenotype' destabilizing endogenous expressed genes including those integral to carcinogenesis; (iii) finding MMR defects in the germline of HNPCC kindred members; (iv) finding that such defects behave as classic tumor suppressor genes in both familial and sporadic colorectal cancers; (v) discovering that MMR 'knockout' mice have an increased incidence of tumors; and (vi) discovering that genetic complementation of MMR defective cells stabilizes the MMR deficiency-associated microsatellite instability. Models of carcinogenesis now must integrate the concepts of a MMR defect induced mutator phenotype (Loeb) with the concepts of multistep colon carcinogenesis (Fearon and Vogelstein) and clonal heterogeneity/selection (Nowell).
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PMID:Mismatch repair defects in human carcinogenesis. 887 55

Recent advances in molecular biology have revealed that the alteration of multiple genes, eg., APC, K-ras, p53, DCC, are involved in multistep colorectal carcinogenesis. Some of these alterations can be used as molecular markers in genetic diagnosis. Genetic diagnoses for colorectal cancer are classified into three categories, eg., 1. identification of the career in the family of patient with hereditary disease such as FPC (Familial Polyposis Coli) or HNPCC (Hereditary Non-Polyposis Colorectal Cancer), 2. early diagnosis of colorectal cancer by identifying gene mutations in the stool, 3. assist for histopathological diagnosis, or risk assessment of the metastasis, recurrence or secondary cancer by molecular means. However, there are several problems in these genetic diagnoses. These consist of two categories, eg., 1. problems in the method of gene analyses or assay system and 2. problems in performing genetic diagnoses itself. The former includes the problem of contamination of different tissue, false positive or negative result in PCR-based analyses, heterogeneity of gene mutation in tumor tissue, and the latter includes the social, ethical or economical problems mainly related to the genetic diagnosis for hereditary colorectal cancers. In this paper, we describe the possibility of genetic diagnosis for colorectal cancers and the current problems, especially from the molecular pathological aspect, in genetic diagnosis.
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PMID:[Molecular-pathological problems of genetic diagnosis for colorectal cancer]. 910 43

Mutations of tumor suppressor genes, of the mismatch DNA repair system, and of the TGF-beta-II-receptor are the main causes for a higher risk of colorectal cancer. Among mutations of the Ape gene, which characterize the clinical manifestation of the familial polyposis (FAP), point mutations are dominating which create new stop codons or arise from deletions or insertions of nucleotides causing frame shifts. Because the binding site of beta-catenin is localized in the C-terminus of the Ape protein, disturbances result in the cellular signal transfer from its loss. Consequently, the interactions of the usually formed Ape-beta-catenin complex with the cytoskeleton and the cadherin system in the plasma membrane as well as the translocation of beta-catenin into the nucleus cannot be realized. Mutations in the genes of the mismatch DNA repair system and of the TGF-beta-II-receptor, the main defects of the HNPCC (hereditary nonpolyposis colorectal cancer), are exclusively identified in sequences of microsatellites. Because the majority of Apc gene mutations is also localized in repetitive motifs even in CpG islands primary disturbances are to postulate in the methylation pattern of the genes producing germline and somatic mutations. Generally, complexly connected reactions are involved in this cascade of colorectal cancer genesis. This fact explains the relatively late clinical manifestation of the disease and offers the possibility to identify carriers with an increased risk of colorectal cancer development in order to integrate them into a programme of control and preventive medicine. Beside the known treatment by surgery and cytostatics, inhibitors of prostaglandin synthesis gain therapeutic significance. Cancerogenesis can be efficiently suppressed by inhibition of the COX-2-induction (cyclo-oxygenase-2). There is a lack of clinical experience for a decision whether a high intraluminal level of butyrate in the large intestine can delay colorectal carcinogenesis.
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PMID:[Molecular etiology of colorectal carcinogenesis, clinical manifestations and therapy]. 924 53

Turcot syndrome is characterized by an association of malignant brain tumors and colon cancer developing in the patient's teens. Since the mechanism of carcinogenesis in Turcot syndrome is still unclear, we analysed genetic changes in tumors from a Turcot patient with no family history of the condition. All tumors, including one astrocytoma, three colon carcinomas, and two colon adenomas, exhibited severe replication error (RER), and all colon tumors showed somatic mutations at repeated regions of TGFbetaRII, E2F-4, hMSH3, and/or hMSH6 genes. Somatic APC mutations were detected in three of three colon carcinomas, and somatic p53 mutations were detected in the astrocytoma and two of three colon carcinomas, both of which showed two mutations without allele loss. We also found that normal colon mucosa, normal skin fibroblasts and normal brain tissue from this patient showed respective high frequencies of RER, in contrast to usual HNPCC patients in which RER was very rare in normal tissues. These results suggest that extreme DNA instability in normal tissues causes the early development of multiple cancer in Turcot syndrome. A missense mutation (GAG to AAG) at codon 705 of hPMS2 gene was detected in one allele of this patient, which was inherited from his mother without tumors. Additional unknown germline mutation may contribute to the genetic instability in normal tissues.
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PMID:Drastic genetic instability of tumors and normal tissues in Turcot syndrome. 941 79

8-oxo-deoxyguanosine triphosphate (8-oxo-dGTP) is a major oxidation product in the nucleotide pool of the cell and is a potent mutagen, because it can be incorporated into DNA with equal frequency opposite either template C or A. The human MTH1 gene (hMTH1) is a homologue of the E. coli mutator gene mutT, which encodes 8-oxo-dGTPase. hMTH1 protein reduces spontaneous mutations by removing 8-oxo-dGTP from the triphosphate pool. To determine whether this gene is associated with carcinogenesis of human ovarian cancer, the present study examined, for the first time, the hMTH1 sequence in 49 ovarian cancers and 9 ovarian cancer cell lines by means of polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) and sequencing analyses. A Gright curved arrow A transition at codon 83 was detected in one patient and one cell line (3.4%), followed by an amino acid change (valineright curved arrow methionine) which was known to cause the protein to be less active in vitro. This one base substitution was found in normal and corresponding tumor DNA, and its allele type was heterozygous. The same change has been detected in HNPCC (hereditary non-polyposis colorectal cancer) and gastric cancer patients, and thus it may not represent a mutation specific for ovarian cancer. A silent Tright curved arrow C transition at codon 119 was detected in 12 patients and 2 cell lines (24.1%). No specific mutations in hMTH1 were found in either ovarian cancer patients or cell lines. Thus, it appears that hMTH1 is not directly associated with ovarian cancer.
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PMID:Mutation analysis of the hMTH1 gene in sporadic human ovarian cancer. 1093 85

Intrahepatic cholangiocarcinoma (ICC) is the second most common malignant primary tumor of the liver in Japan. Despite progress in operative techniques and adjuvant therapy, the prognosis of ICC remains very poor. Therefore, it is important to investigate the mechanism of carcinogenesis and progression of ICC. We screened allelic losses at 6 loci, including that of novel tumor-suppressor gene FEZ1 on chromosome 8p, and at 5 microsatellite loci to define the association with tumor-suppressor genes (HNPCC, APC, RB1, p53, DCC) in tumors from 18 unrelated ICC patients by PCR-loss of heterozygosity (LOH) assay and correlated the alterations with clinicopathological parameters. As a result, 61.1% (11 of 18) of patients showed LOH at 1 of the loci at least, and microsatellite instability was observed in 16.7% (3 of 18). At locus D8S258, relatively frequent LOH was detected (17.6%) compared with other loci on chromosome 8p. Among the other 5 chromosomal arms tested, the highest frequency of LOH (23.5%) was observed at D17S153. Fifty percent of cases with the mass-forming + periductal infiltrating type were frequently detected by LOH at D8S258 compared to cases of the mass-forming or intraductal growth type. In conclusion, we show that 1 putative tumor-suppressor gene on 8p22 may relate to progression of ICC and suggest that the p53 tumor-suppressor gene may be associated with carcinogenesis of ICC.
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PMID:Allelic loss in human intrahepatic cholangiocarcinoma: correlation between chromosome 8p22 and tumor progression. 1100 73

To evaluate the malignant potential of synchronous multiple colorectal cancers, we studied clinicopathologically 31 synchronous multiple colorectal cancers resected at our hospital. We also compared the p53 gene mutation rate, replication error (RER) rate, and Ki-67 antigen positivity rate between these cancers and 90 sporadic colorectal cancers. There was no significant difference in lymphoid and venous invasion, hepatic metastasis, or stage of colon cancer between the two types of cancers. The p53 gene mutation rate was lower in synchronous multiple colorectal cancers (p < 0.05). The RER rate and positivity rate for Ki-67 antigen was significantly higher in these cancers (p < 0.05). These results suggest that some synchronous multiple colorectal cancers result from carcinogenesis in which RER genes are involved, as HNPCC does. In the patients with synchronous multiple colorectal cancers, it is clinically important to follow them carefully focusing on multiple metachronous colorectal cancers and multiple organ cancers.
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PMID:[Alternations of p53 gene, microsatellite instability and proliferation associated antigen Ki-67 in the synchronous multiple colorectal cancers]. 1172 53

COX-2, the isoform of cyclooxygenase inducible by cytokines, mitogens, and growth factors, appears to play an important role in inflammation and carcinogenesis. In the colon, COX-2 overexpression results in cell cycle alterations, and NSAIDs have proven effective in cancer chemoprevention. HNPCC (hereditary nonpolyposis colon cancer) is a clinically defined cancer susceptibility syndrome in which women are also at significantly increased risk for the development of endometrial carcinoma. The purpose of this study was to evaluate expression of COX-2 in benign and malignant endometrium in the context of other cell cycle and proliferation markers, including Ki-67, cyclin D1, and the cyclin-dependent kinase inhibitor, p21. Immunostains with COX-2, Ki-67, cyclin D1, and p21 antibodies were performed on formalin-fixed and paraffin-embedded tissue sections from 40 cases: 10 benign (5 atrophic and 5 proliferative) endometria, 6 hyperplasias (complex without atypia), and 24 endometrioid carcinomas (9 well, 4 moderately, and 11 poorly differentiated). Ki-67 was positive in all proliferative and neoplastic endometria. Cyclin D1 and p21 were both overexpressed in endometrial hyperplasia and endometrioid carcinomas. COX-2 was negative in the nonneoplastic endometrium, stained minimally in the well-differentiated endometrioid carcinomas, and stained most strongly in the moderately and poorly differentiated endometrioid carcinomas. Because cyclin D1 may function as an oncogene, its effects may dominate the usual inhibitory effect of a rising p21. Alternatively, it has been shown that p21 can promote cell cycle function by stabilizing cell cycle complexes. The overexpression of COX-2 in poorly differentiated endometrioid carcinoma and lack of expression in hyperplasia and well-differentiated carcinoma suggests that in this form of cancer, COX-2 may play a role in tumor progression rather than tumor initiation.
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PMID:Expression of COX-2, Ki-67, cyclin D1, and P21 in endometrial endometrioid carcinomas. 1191 24

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