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)

A plasma membrane preparation from human amnion (WISH) cells contained uridine diphosphate sugars and methyl-uridine diphosphate (mUDP) sugars. The synthesis of mUDP-glucose, mUDP-mannose, and mUDP-fucose by the membrane preparation occurred when supplemented with uridine-5'-diphosphate-glucose and S-adenosyl-L-methionine. It is suggested that this newly recognized route for fucose biosynthesis might be employed by certain transformed cells, and may partly account for the methionine dependence of certain human tumors. Additionally, it is suggested that, in colon cancer, a deficiency of folic acid and methionine might affect mUDP-sugar biosynthesis rather than the methylation of DNA.
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PMID:Involvement of methionine in the synthesis of certain membrane-associated nucleotide sugars by human amnion (WISH) cells. 862 Apr 51

To explore the determinants of cytotoxicity during prolonged exposure to pharmacologically relevant concentrations of 5-fluorouracil (FUra), we studied the effects of FUra at concentrations ranging from 0.1 to 1 microM in HCT 116 and HT 29 colon cancer cells grown in the presence of physiologic levels of leucovorin. A 5- and 7-day exposure to 1 microM FUra reduced cell growth to 46% and 20% of control in HT 29 cells and to 74% and 38% of control in HCT 116 cells. Concurrent exposure to thymidine (10 or 20 microM) or uridine (1 mM) provided partial protection against FUra toxicity in HT 29 cells, but did not protect HCT 116 cells. After a 24-h exposure to 1 microM [3H]FUra, free 5-fluoro-2'-deoxyuridine-5' -monophosphate (FdUMP) and FUDP. + FUTP levels were 0.7 and 144 pmol/10(6) cells in HT 29 cells, respectively, and 3.9 and 178 pmol/10(6) cells in HCT 116 cells. FdUMP and FUDP + FUTP pools increased by 5.7- and 2.0-fold in HT 29 cells and by 1.7- and 3.3-fold in HCT 116 cells over the next 48 h, but did not accumulate thereafter. After a 24-h exposure to 1 microM [3H]FUra, FUra-RNA levels were 158 and 280 fmol/microgram in HT 29 and HCT 116 cells, respectively; FUra-RNA levels increased over time, and reached 700 and 1156 fmol/microgram at day 5. Concurrent exposure to 1 mM uridine for 72 h did not diminish [3H]FUra-RNA incorporation. Upon removal of [3H]FUra following a 24-h exposure, FUra-RNA levels remained relatively stable with 57-78% retained at 120 h. A low level of [3H]FUra-DNA incorporation was detected in HT 29 cells. Thymidylate synthase (TS) catalytic activity in control cells was 2-fold higher in HCT 116 cells compared to HT 29 cells (47 vs. 23 pmol/min/mg). Total TS content increased 1.5- to 3-fold over control in both cell lines during FUra exposure, and ternary complex formation was evident for up to 96 h-dTTP pools were not depleted in FUra-treated cells, suggesting that residual TS catalytic activity was sufficient to maintain dTTP pools relative to demand. Surprisingly, the partial inhibition of TS was accompanied by a striking accumulation of immunoreactive "dUMP" pools in both lines; dUTP pools also increased 2-to 3-fold. In summary, the gradual and stable accumulation of FUra in RNA noted in both lines may account for the thymidine-insensitive component of FUra toxicity. Because dTTP pools were not appreciably diminished, the interference with nascent DNA chain elongation and induction of single-strand breaks in newly synthesized DNA in both cell lines may be due to misincorporation of deoxyuridine nucleotides.
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PMID:Determinants of cytotoxicity with prolonged exposure to fluorouracil in human colon cancer cells. 916 89

DNA mismatch repair (MMR) is an efficient system for the detection and repair of mismatched and unpaired bases in DNA. Deficiencies in MMR are commonly found in both hereditary and sporadic colorectal cancers, as well as in cancers of other tissues. Because fluorinated thymidine analogues (which through their actions might generate lesions recognizable by MMR) are widely used in the treatment of colorectal cancer, we investigated the role of MMR in cellular responses to 5-fluorouracil and 5-fluoro-2'-deoxyuridine (FdUrd). Human MLH1(-) and MMR-deficient HCT116 colon cancer cells were 18-fold more resistant to 7.5 microM 5-fluorouracil (continuous treatment) and 17-fold more resistant to 7.5 microM FdUrd in clonogenic survival assays compared with genetically matched, MLH1(+) and MMR-proficient HCT116 3-6 cells. Likewise, murine MLH1(-) and MMR-deficient CT-5 cells were 3-fold more resistant to a 2-h pulse of 10 microM FdUrd than their MLH1(+) and MMR-proficient ME-10 counterparts. Decreased cytotoxicity in MMR-deficient cells after treatment with various methylating agents and other base analogues has been well reported and is believed to reflect a tolerance to DNA damage. Synchronized HCT116 3-6 cells treated with a low dose of FdUrd had a 2-fold greater G(2) cell cycle arrest compared with MMR-deficient HCT116 cells, and asynchronous ME-10 cells demonstrated a 4-fold greater G(2) arrest after FdUrd treatment compared with CT-5 cells. Enhanced G(2) arrest in MMR-proficient cells in response to other agents has been reported and is believed to allow time for DNA repair. G(2) cell cycle arrest as determined by propidium iodide staining was not a result of mitotic arrest, but rather a true G(2) arrest, as indicated by elevated cyclin B1 levels and a lack of staining with mitotic protein monoclonal antibody 2. Additionally, p53 and GADD45 levels were induced in FdUrd-treated HCT116 3-6 cells. DNA double-strand break (DSB) formation was 2-fold higher in MMR-proficient HCT116 3-6 cells after FdUrd treatment, as determined by pulsed-field gel electrophoresis. The formation of DSBs was not the result of enhanced apoptosis in MMR-proficient cells. FdUrd-mediated cytotoxicity was caused by DNA-directed and not RNA-directed effects, because administration of excess thymidine (and not uridine) prevented cytotoxicity, cell cycle arrest, and DSB formation. hMLH1-dependent responses to fluoropyrimidine treatment, which may involve the action of p53 and the formation of DSBs, clearly have clinical relevance for the use of this class of drugs in the treatment of tumors with MMR deficiencies.
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PMID:Role of the hMLH1 DNA mismatch repair protein in fluoropyrimidine-mediated cell death and cell cycle responses. 1143 59

We investigated how agonists at purinoceptors may affect tumour cell metabolism. This was investigated in vitro in tumour cell lines by microphysiometry, which method monitors extracellular acidification rate (ECAR), on-line. The cell lines investigated were the murine sarcoma, MCG 101, and the human colon cancer, HT-29. In MCG 101, adenosine-5'-triphosphate (ATP) or uridine-5'-triphosphate (UTP) caused a concentration-dependent increase in ECAR, most likely due to the ligation of P2Y(2) receptors, which response was blocked by suramin. In HT-29, ATP or UTP elicited a concentration-dependent, biphasic change in ECAR (increase/decrease). The pharmacological analysis suggests the involvement of P2Y(2) receptors, although other P2 receptor subtypes cannot be entirely excluded. This biphasic response to UTP or ATP was resistant to suramin. The expression of P2Y(2) receptors was demonstrated in both cell lines by immunocytochemistry and Western blot. The current study, thus, shows the functional and morphological expression of a purinoceptor subtype with partly different effects on metabolism in two different tumour cell lines.
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PMID:Expression of P2Y2 purinoceptors in MCG 101 murine sarcoma cells, and HT-29 human colon carcinoma cells. 1523 32

c-Yes is a member of the c-Src family of tyrosine kinases and has been implicated in intracellular signaling, cell morphology, and adhesion. Changes in its expression have also been associated with the aggressiveness of human breast and colon cancer cells. In MDA-MB-231 human breast cancer cells, overexpression of the small heat shock protein 27 (hsp27) results in a downregulation of c-Yes levels, concomitant with increased in vitro invasiveness and in vivo metastatic behavior. Very little is known, however, about the mechanisms regulating c-Yes expression. Here, we demonstrate that hsp27-induced c-Yes downregulation is not due to a reduction in transcriptional activity. However, the 3'-untranslated region (3'-UTR) of the c-Yes gene may be involved in its own regulation, since this region affects heterologous reporter gene activity in transactivation assays. This down-regulatory effect maps to three adenine/uridine-rich elements (AREs) that bind to cellular HuR and AUF1 (hnRNP D), two ARE-binding proteins (ARE-BPs) implicated in accelerated mRNA degradation. Our results suggest that the c-Yes 3'-UTR contains at least three newly identified AREs which are bound specifically by ARE-BPs, and provide a structural basis for post-transcriptional regulation of c-Yes expression.
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PMID:The c-Yes 3'-UTR contains adenine/uridine-rich elements that bind AUF1 and HuR involved in mRNA decay in breast cancer cells. 1628 64

Malignant transformation is often accompanied by an aberrant glycosylation profile of the cell surface-in particular, the production of GlcNAcbeta1-6Manalpha1 branches in N-linked glycoproteins. To identify the target glycoproteins, we show a method using recombinant chicken N-acetylglucosaminyltransferase VI (GnT VI) and radiolabeled uridine (5'-)diphosphate-GlcNAc. The assay exploits the fact that GnT VI has a strict requirement for the GlcNAcbeta1-6Manalpha1 structure for activity, when a pyridylaminated free N-glycan is used as the acceptor substrate. Human asialo-agalacto alpha1-acid glycoprotein (AGP), which is known to contain GlcNAcbeta1-6Manalpha1 branches in its N-linked glycan chains, was radiolabeled when reacted with GnT VI, whereas human asialo-agalacto transferrin and bovine fetuin, neither of which contains a GlcNAcbeta1-6Manalpha1 structure were not, thus corroborating the specificity of the assay. Several proteins from human serum after pretreatment with sialidase and beta-galactosidase could be detected using the assay. One was identified as AGP from its mobility on SDS-PAGE, demonstrating the potential of this assay even with crude materials. Furthermore, this method could detect a protein that was also positively stained with leukoagglutinating phytohemagglutinin (L(4)-PHA) using glycoproteins prepared from WiDr human colon cancer cells. This method should provide a useful complement to the current method, which relies on the specificity of L(4)-PHA.
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PMID:A specific detection of GlcNAcbeta1-6Manalpha1 branches in N-linked glycoproteins based on the specificity of N-acetylglucosaminyltransferase VI. 1642 2

Thymidine phosphorylase (TP) and uridine phosphorylase (UP) are often upregulated in solid tumors and catalyze the phosphorolysis of natural (deoxy)nucleosides and a wide variety of fluorinated pyrimidine nucleosides. Because the relative contribution of each of the two enzymes to these reactions is still largely unknown, we investigated the substrate specificity of TP and UP in colon cancer cells for the (fluoro)pyrimidine nucleosides thymidine (TdR), uridine (Urd), 5'-deoxy-5-fluorouridine (5'DFUR), and 5FU. Specific inhibitors of TP (TPI) and UP (BAU) were used to determine the contribution of each enzyme in relation to their cytotoxic effect. The high TP expressing Colo320TP1 cells were most sensitive to 5'DFUR and 5FU, with IC50 values of 1.4 and 0.2 microM, respectively, while SW948 and SW1398 were insensitive to 5'DFUR (IC50>150 microM for 5'DFUR). TPI and BAU only moderately affected sensitivity of Colo320, SW948, and SW1398, whereas TPI significantly increased IC(50) for 5'DFUR (50-fold) and 5FU (11-fold) in Colo320TP1 and BAU that in C26A (9-fold for 5'DFUR; p<0.01). In the epithelial skin cell line HaCaT both inhibitors were able to decrease sensitivity to 5'DFUR and 5FU separately. HaCaT might be a model for 5'DFUR toxicity. In the colon cancer cells 5'DFUR degradation varied from 0.4 to 50 nmol 5FU/h/10(6)cells, that of TdR from 0.3 to 103 nmol thymine/h/10(6)cells, that of Urd from 0.8 to 79 nmol uracil/h/10(6)cells, while conversion of 5FU to FUrd was from 0.3 to 46 nmol/h/10(6)cells. SW948 and SW1398 were about equally sensitive to 5'DFUR and 5FU, but SW1398 had higher phosphorylase activity (>65-fold) compared to SW948. In SW948 and HaCaT TPI and BAU inhibited TdR and Urd phosphorolysis (>80%), respectively. Both TP and UP contributed to the phosphorolysis of 5'DFUR and 5FU. In the presence of both inhibitors, still phosphorolysis of 5FU (>40%) was detected in the tumor and HaCaT cell lines, and remarkably, that of all four substrates in SW1398 cells. 5'DFUR phosphorolysis was also measured in situ, where Colo320TP1, SW1398, and HaCaT cells produced significant amounts 5FU from 5'DFUR (>10 nmol/24h/10(6)cells). In Colo320TP1 and in HaCaT cells TPI completely prevented 5FU production, but not in SW1398 cells, where BAU decreased this by 67% (p<0.01). High uracil and dUrd levels were detected in the medium. Uracil accumulation was heavily reduced in the presence of TPI for Colo320TP1 and HaCaT cells, whereas 5FU-induced dUrd production by these cell lines increased (p<0.01). In contrast, for SW1398 cells only BAU was able to reduce uracil levels, and dUrd production remained unchanged. In conclusion, overlapping substrate specificity was found for TP and UP in the cell lines, in which both enzymes were responsible for converting TdR and Urd, and 5'DFUR. 5'DFUR and 5FU were converted to their products in both the colon cancer cells and keratinocytes.
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PMID:Activity and substrate specificity of pyrimidine phosphorylases and their role in fluoropyrimidine sensitivity in colon cancer cell lines. 1709 63

Epigallocatechin gallate (EGCG), a key active ingredient in green tea, has many anti-carcinogenic activities. The aim of the present study was to investigate whether EGCG could prevent the occurrence or metastases of orthotopic colon cancer and probe the underlined mechanisms. We observed the inhibition of EGCG on growth and metastases of colon tumor implanted orthotopically in the cecum of nude mice. Immunohistochemistry and Western-blotting analysis were used to detect NF-E2-related factor 2 (Nrf2) protein expressions. RT-PCR was also applied to detect the mRNA levels of Nrf2, uridine 5'-diphosphate-glucuronosyltransferase (UGT) 1A, UGT1A8 and UGT1A10 in colon tumors. As a result, the inhibition rates on tumor growth in the 3 EGCG groups were significantly different (all p < 0.001) compared with the control group. In addition, different doses of EGCG were able to inhibit liver and pulmonary metastases to varying degrees. The protein level of Nrf2 and the mRNA levels of Nrf2, UGT1A, UGT1A8 and UGT1A10 significantly increased in EGCG-treated mice in comparison with the control group (all p < 0.01). The results demonstrated that EGCG has a preventive effect on the growth and liver and pulmonary metastases of orthotopic colon cancer in nude mice, and this anticancer effect could be partly caused by activating the Nrf2-UGT1A signal pathway.
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PMID:Inhibition of epigallocatechin gallate on orthotopic colon cancer by upregulating the Nrf2-UGT1A signal pathway in nude mice. 1765 75

Fluorouracil (5FU) acts by RNA-incorporation and inhibition of thymidylate synthase; the first action is counteracted by uridine, and the second is enhanced by leucovorin (LV). Growth inhibition of C26-10 colon cancer cells by 5FU was enhanced by LV and rescued by uridine, but 5FU-LV was only partially rescued by uridine. In WiDr cells, 5FU sensitivity was not enhanced by LV, while both 5FU and 5FU-LV were rescued by uridine. Intermediate trends were found in SW948 and HT29 cells. Uridine rescue in mice allowed 1.5-fold increase in 5FU dose, leading to 2-fold increase in the antitumor effect and thymidylate synthase inhibition in resistant Colon-26 tumors. In the sensitive Colon-26-10 tumor, uridine rescue decreased 5FU-RNA incorporation > 10-fold, without affecting the antitumor activity. The use of LV and uridine can differentiate between two mechanisms of action of 5FU.
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PMID:Selective protection by uridine of growth inhibition by 5-fluorouracil (5FU) mediated by 5FU incorporation into RNA, but not the thymidylate synthase mediated growth inhibition by 5FU-leucovorin. 1860 May 33

The major determinants of 5-flurouracil (5-FU) response would seem, based on accumulated literature, to be thymidylate synthase (TYMS, TS) expression levels, TS gene modifications, and TP53 status. We tested 5-FU sensitivity in yeast and human cancer cell models in which TS or TP53 alleles and expression were varied. Polymorphic TS tandem repeat status, TS expression levels reported, TS intragenic mutations, and TP53 status in outbred and experimental cancer cell lines did not predict 5-FU sensitivity or resistance. Novel observations included a dose-resistant persistence of unbound TS protein in many cancers and, upon 5-FU treatment of the colon cancer cell line, HCT116, evidence of allelic switching favoring transcripts of the mutant TS allele. The reported alleles having an intragenic mutation could not be causally associated with major degrees of 5-FU sensitivity. In yeast, TS protein was altered upon treatment with FdUMP, but 5-FU toxicity seemed to be largely RNA-based, being rescued by uridine rather than by thymidine. Cancer cell lines were also rescued from 5-FU toxicity with uridine rather than thymidine. Additionally, a TS (CDC21) knockout yeast strain, obviating any potential role for TS protein as a target, was hypersensitive to 5-FU. When denatured proteins from cancer cells treated with radiolabeled 5-FU were labeled, species with alternative molecular weights other than TS were visualized, providing further evidence for alternative 5-FU protein targets. These data emphasize that TS and TP53 status do not consistently explain the variance in responses of fluoropyrimidine-treated cancer cells, in part due to RNA-based toxicity.
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PMID:Limits to thymidylate synthase and TP53 genes as predictive determinants for fluoropyrimidine sensitivity and further evidence for RNA-based toxicity as a major influence. 1915 91


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