Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0699790 (colon cancer)
 28,837 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Activation of c-Ki-ras by point mutation within exon 1 was studied in 33 specimens of dysplastic gastrointestinal lesions or of cancers presumed to arise from dysplasia. Samples were obtained from patients with underlying ulcerative colitis or Barrett's esophagus, two diseases associated with dysplasia and increased rates of colonic or esophageal adenocarcinoma, respectively. Genomic DNA was amplified using primers bounding this exon in the polymerase chain reaction. Polymerase chain reaction products were analyzed by direct dideoxy sequencing. Three point mutations in codon 13 of c-Ki-ras were found, all in colonic specimens (two high-grade dysplasias and one adenocarcinoma arising in ulcerative colitis). No point mutations were observed in the second exon of c-Ki-ras or in and around codons 12, 13, and 61 of c-N-ras and C-Ha-ras in a partial sampling of the specimens. These data indicate that ras family protooncogene activation is an uncommon event at this level of malignant progression in these disease states. Carcinogenesis in ulcerative colitis and Barrett's esophagus may proceed via different pathways than in sporadic colon cancer, perhaps involving loss or inactivation of suppressor genes.
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PMID:Activation of c-Ki-ras in human gastrointestinal dysplasias determined by direct sequencing of polymerase chain reaction products. 218 99

Flow cytometric DNA content analysis is a rapid, quantitative method of determining the DNA ploidy status and proliferative index of a given tumor. Abnormal DNA content, or aneuploidy, has been recognized as a marker of malignancy and is present in about 70 per cent of solid tumors. In the majority of solid tumors, the consensus is that the presence of an aneuploid tumor predicts a poorer over-all survival rate and a shorter disease-free interval, indicating that patients with diploid tumors have a more favorable prognosis than those with aneuploid tumors. The prognostic implications of an abnormal DNA content, therefore, suggest either a higher risk of relapse, a worsening of survival rate or a risk for progression of disease in stages I and II carcinoma of the breast, carcinoma of the colon and rectum, superficial carcinoma of the bladder and malignant melanoma. Thus, the assessment of cellular DNA content should be regarded as an additional prognostic determinant and should play an ancillary role in the decisions regarding the management of patients with malignant disease. With the introduction of more sophisticated technology, it will be possible to simultaneously assay for DNA ploidy and cell cycle distribution in addition to a series of tumor markers, such as CEA, and various products of oncogenes, thus providing further understanding of the heterogeneity of solid tumor cells.
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PMID:Flow cytometry and prognostic implications in patients with solid tumors. 220 Oct 96

Lymphocytes from lymph nodes draining the tumor region in patients with colorectal cancer were fused with two different human B-lymphoblastoid cell lines, LICR-LON-HMy-2 (HMy-2) and WI-L2-729-HF2 (729-HF2), to generate hybridomas synthesizing antibodies reacting with tumor-associated antigens. In this way 220 hybridomas were obtained which produce antibody reacting with colon cancer cells. All established clones produced IgM. Four human monoclonal antibodies have been further analyzed. The cell lines producing these antibodies are all hybrids based on DNA analysis. Three of the antibodies (G4146, B9165 and D4213) showed binding to differentiation antigens by immunocytochemical analysis on different cancer cell lines and normal human leucocytes and by immunohistochemical analysis on sections of frozen malignant and normal tissues, while the fourth (F11348) showed a reaction with all cells and tissues tested. Western blots of tumor extracts showed binding of G4146 to two components from colon cancer cells with Mr of 59 K and 61 K, while B9165 bound to a 43 K component and F11348 to several components with Mr from 30 to 200K. D4213 showed no binding in this analysis. The results obtained demonstrate the successful application of hybridoma technology to produce human monoclonals with reactivity to differentiation antigens.
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PMID:Human-human hybridoma producing monoclonal antibodies against colorectal cancer-associated antigens. 220 14

Tumor-producing phorbol esters [e.g., 12-O-tetradecanoylphorbol-13-acetate (TPA)] induce changes in a human colon cancer cell line, VACO 10MS, that mimic terminal differentiation: a rapid blockade of DNA replication and cell division, a marked increase in cell adhesion properties with striking changes in morphology, and the acquisition of ion-transporting activities. The present report shows that the triggering of this terminal differentiation sequence by TPA is associated with a rapid release of heparan sulfate proteoglycans from the cell surface that is soon followed by an acceleration of proteoglycan synthesis. The activation of the release mechanism is independent of ongoing protein synthesis, whereas the resynthesis of the proteoglycans requires the production of new proteins. A persistent high rate of proteoglycan synthesis and release appears correlated with the progression of the colon cell into the terminal differentiation state. Bryostatin 1, an agent which has been shown previously to block the TPA-induced terminal differentiation of this cell line, also largely prevents the TPA effects on proteoglycan metabolism. Since both TPA and bryostatin 1 produce their effects through the activation of members of the protein kinase C class of enzymes, it is proposed that the differentiation state of these colon cancer cells may be regulated by a differential activation of isozymes or a ligand-directed phosphorylation of proteins that are involved in proteoglycan metabolism.
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PMID:Phorbol esters activate proteoglycan metabolism in human colon cancer cells en route to terminal differentiation. 227 82

Heritable and genetic factors pertinent to colon cancer can be divided into three categories: inherited syndromes, genetic epidemiology, and molecular genetics. Familial adenomatous polyposis (FAP) and Gardner syndrome (GS) are rare dominantly inherited syndromes characterized by hundreds to thousands of colonic adenomatous polyps. Colon cancer occurs at a young age in both diseases unless the colon is removed. Peutz-Jeghers syndrome and familial juvenile polyposis are inherited hamartomatous polyposis conditions with a less dramatic, but definite, increased risk for colon cancer. These four polyposis syndromes together account for less than 1% of cases of colon malignancy. Hereditary nonpolyposis colorectal cancer is a dominantly inherited form of colon cancer characterized by an early age of onset and a predilection for proximal colonic tumours. Multiple primary malignancies are frequently observed and one or several adenomatous polyps are often present in affected individuals; 4-6% of colon cancer cases occur in relationship to this syndrome. Genetic epidemiological studies have consistently shown that first-degree relatives of persons with colon cancer have a twofold to threefold increased risk of having colon malignancy. More recent studies have found a similar risk among relatives of those with adenomatous polyps. Studies of colon cancer and adenomatous polyps in pedigrees have further demonstrated that this familial clustering probably occurs on the basis of partially penetrant inherited susceptibilities. These inherited susceptibilities probably interact with environmental factors to give rise to polyp growth and finally colon cancer. Molecular studies have begun to elucidate the genetic mechanisms of colon cancer at the DNA level. The germinal mutation of FAP and GS has been localized to the long arm of chromosome 5. Tissue samples from "random" adenomatous polyps and colon cancers have shown frequent and specific acquired DNA sequence deletions on chromosomes 5, 17, and 18. Mutations and over-expression of the ras oncogene likewise have been observed in such tissues. The chromosome 5 defect in polyp and cancer tissues is probably at the same locus as the germinal mutation of FAP. There is evidence that this locus normally regulates expression of the c-myc oncogene, which in turn probably has a regulatory function in DNA replication. The chromosome 17 deletion is a mutation of the gene for the transformation-associated protein, p53. Appropriate screening starting at a relatively young age is necessary to prevent cancer in the inherited syndromes. Screening is also indicated in close relatives of those with nonsyndromic or common colon cancer in view of the moderately increased risk for colon cancer in this group.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Risk and surveillance of individuals with heritable factors for colorectal cancer. WHO Collaborating Centre for the Prevention of Colorectal Cancer. 228 1

We have isolated a set of complementary DNA (cDNA) clones that together encode the alkaline phosphatase of human colon cancer LS174T cells. These clones include two cDNAs isolated from a conventionally prepared oligodeoxythymidylate-primed lambda ZAP cDNA library and three cDNA clones prepared by using the polymerase chain reaction. The deduced amino acid sequence of the alkaline phosphatase primary transcript contains 532 amino acids. This enzyme is similar to, but not identical with, placental alkaline phosphatase (PLAP); it exhibits 12-19 amino acid substitutions when compared to the various alleles of PLAP. Also, it is similar to PLAP in that it is apparently attached to the cell membrane by a phosphatidylinositol-containing anchor as judged by the ability of phosphatidylinositol-specific phospholipase C to release it from membranes. It is different from PLAP however, in terms of its signal sequence which only contains 19 amino acids as compared to 22 for PLAP. Moreover, the 3'-untranslated region of the LS174T cell alkaline phosphatase message diverges considerably from the PLAP message. The LS174T cell alkaline phosphatase cDNAs are actually much more similar to the "germ cell" alkaline phosphatase gene than they are to PLAP. Only 7 amino acid substitutions exist between the LS174T cell enzyme and the alkaline phosphatase encoded by the germ cell alkaline phosphatase genomic DNA clone isolated by Millan and Manes (Proc. Natl. Acad. Sci. USA, 85: 3024-3028, 1988). Furthermore, the 3'-untranslated region of the LS174T cell alkaline phosphatase message is very similar to the sequence immediately downstream of the coding region of the germ cell alkaline phosphatase genomic DNA clone. Thus, these results indicate that this colon cancer cell alkaline phosphatase is likely to represent an allelic variant encoded at the germ cell alkaline phosphatase locus.
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PMID:Molecular cloning of complementary DNAs encoding alkaline phosphatase in human colon cancer cells. 229 57

Although the inhibitory effect of caloric restriction on tumorigenesis is substantial and well known, the pertinent mechanisms remain to be determined. We recently suggested that the risk of cancer may be directly related to the total number of dividing cells within an affected organ. This study evaluates the effects of early caloric restriction on the cellular growth of the colon. The experiment began one day postpartum and ended six weeks later with the killing of all animals. It consisted of two consecutive periods: a) three weeks of suckling and b) three weeks postweaning. Animals whose food was restricted only during the suckling period showed normal colons when killed at six weeks. Caloric restriction (40%) for three weeks postweaning resulted in colons of lower weight with fewer cells (less total DNA) and reduced total DNA synthesis [( 3H]thymidine uptake, dpm/colon) when compared with animals fed ad libitum postweaning. Conversely, only rats fed ad libitum from birth through the first three weeks after weaning demonstrated an increase (21%) in the rate of DNA synthesis (dpm/mg DNA) compared with other animals. In addition, the colonic crypts showed no differences in the number of cells or the number of dividing cells, as determined by autoradiography. By contrast, the total number of crypts (and/or the number of mucosal cells between crypts) are reduced, and hence the total number of colonic mucosal cells dividing at any given time are similarly decreased. The reduced number of dividing cells in the colons of these animals (i.e., those restricted postweaning) could explain previous data suggesting that they are resistant to the induction of colon cancer.
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PMID:The effect of early caloric restriction on colonic cellular growth in rats. 230 Apr 96

Bile acids have been implicated as promoters and cocarcinogens in the etiology of colon cancer and as comutagens and mutagens in bacteria. These observations suggest the hypothesis that bile acids may interact directly with DNA. We treated the single stranded circular DNA of phage M13 with bile acids and found that the transfection efficiency of this DNA declined up to a 1000-fold. This result suggests that bile acids can damage DNA and thus may play an important role in the etiology of colon cancer.
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PMID:Modification of DNA by bile acids: a possible factor in the etiology of colon cancer. 231 81

Alterations in gene expression associated with colorectal cancer have been difficult to study because mucosal cell progenitors are not available in culture. We therefore examined specific genes in approximately 100 human colon cancer cell lines using complementary DNA probes and found profound alterations and heterogenity of gene expression in human colorectal carcinoma. Our data imply that understanding human colorectal cancer will not be accomplished by studying one or two oncogenes in a limited number of cell lines or fresh human tissue. More appropriate postulates of transformation to dictate experimental design may include the investigation of proposed three-dimensional structural changes of interface chromatin or other generalized structural relationships that could predispose to an aberrant gene expression program during transformation. Furthermore, focusing on mechanisms of initiation and defining the molecular genetic markers of gastrointestinal mucosal initiation should lead to a more focused set of genetic, rather than epigenetic, mechanisms that underlie oncogenic transformation.
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PMID:Alterations of gene expression in human colorectal cancer. Biological implications. 232 16

In HT29 cells 5-fluorouracil (5FU) cytotoxicity is enhanced by subsequent incubation of cells in medium containing 1% N-methylformamide (NMF). This enhancement does not appear to be related to differences in the repair of 5FU-induced DNA damage. It is proposed that the inhibition of DNA synthesis by NMF (that is reversible and does not result in any detectable toxicity) becomes a lethal event in a cell in which DNA synthesis has already been altered by 5FU exposure. The synergism is sequence dependent (i.e. it does not occur when NMF is given before 5FU) and specific for some cell types as shown by the fact that no synergism was found in L1210 mouse leukaemia cells. In nude mice transplanted s.c. with HT29 cells daily 5FU treatment (for 5 days) followed by daily NMF treatment (for 10 days) caused much greater inhibition of tumour growth than either drug alone or the same combination given in the opposite order (NMF then 5FU). These results, if confirmed on other human colon tumours, could be of clinical interest as a means of increasing the therapeutic efficacy of 5FU in patients with colon cancer.
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PMID:Synergism between 5-fluorouracil and N-methylformamide in HT29 human colon cancer line. 232 1


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