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)

Interferon-alpha (IFN alpha) potentiates the antitumor activity of 5-fluorouracil (FUra) in colon cancer in vitro, in vivo, and clinically. A likely mechanism for this action is the induction by IFN alpha of thymidine phosphorylase (TP), the first enzyme in one pathway for the metabolic activation of FUra to fluorodeoxyribonucleotides. To test this hypothesis, an expression vector containing the TP cDNA was transfected into HT-29 human colon carcinoma cells. Five stable transfectants were selected and analyzed. All showed increased sensitivity to FUra cytotoxicity, ranging from a 2-fold to a 19-fold decrease in the IC50 for FUra, compared to wild-type cells. Levels of TP mRNA, protein, and enzyme activity were elevated in the transfectants, and there was a significant correlation between the relative increase in sensitivity to FUra and both the increase in both TP mRNA levels and TP activity. Transfected cells exhibited increased formation of FdUMP, but not the ribonucleotides FUDP and FUTP, from FUra when compared to wild-type cells. The changes in TP activity, FdUMP formation, and FUra sensitivity in the transfected cells were comparable with those seen after treatment of wild-type cells with IFN alpha. These studies provide direct evidence for the role of TP in mediating the sensitivity of colon carcinoma cells to FUra, and further support the importance of the induction of TP in the biomodulating action of IFN alpha on FUra chemosensitivity.
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PMID:Thymidine phosphorylase mediates the sensitivity of human colon carcinoma cells to 5-fluorouracil. 764 71

The antitumor activity of cytostatic 5'-deoxy-5-fluorouridine (5'-dFUrd) depends on its being converted to 5-fluorouracil (5-FUra) by the enzyme thymidine phosphorylase (dThdPase, EC 2.42.4). We prepared mouse anti-human dThdPase monoclonal antibodies to serve as tools for clinical studies with this drug. Partially purified dThdPase obtained form HCT116 human colon cancer cells grown in athymic mice was used as and antigen for the immunization of mice. Six hybridomas were cloned which produced anti-human dThdPase antibodies, as detected by Western blot analysis with human dThdPase. With these antibodies, we developed an ELISA method sensitive enough to measure dThdPase levels, even in tumor tissue samples weighing as little as 10 mg. In addition, one monoclonal antibody was suitable for immunologically staining the enzyme in tumor tissues. Thus, these anti-human dThdPase monoclonal antibodies could be used to measure levels of the enzyme in tumor cells, which is essential for the activation of 5'-dFUrd.
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PMID:Preparation of anti-human thymidine phosphorylase monoclonal antibodies useful for detecting the enzyme levels in tumor tissues. 895 Nov 54

Capecitabine (N4-pentyloxycarbonyl-5'-deoxy-5-fluorocytidine) is a novel fluoropyrimidine carbamate that is converted to 5-fluorouracil (5-FUra) by three enzymes located in the liver and tumors; the final step is the conversion of 5'-deoxy-5-fluorouridine (5'-dFUrd) to 5-FUra by thymidine phosphorylase in tumors. The present study compared the efficacy of capecitabine and 5-FUra at their maximum tolerated doses in CXF280, HCT116, COLO205, and WiDr human colon cancer xenograft models, and measured subsequent 5-FUra and 5'-dFUrd levels in tumors and in the plasma and muscle. Capecitabine was effective in the first three models, whereas 5-FUra was effective only in CXF280, which is a cell line highly susceptible to fluoropyrimidines. In the three susceptible models, 5-FUra AUCs in tumors after capecitabine administration were 210 to 303 nmol x hr/g, whereas those after 5-FUra administration were 8.54 to 13.1 nmol x hr/g. In addition, capecitabine gave higher levels of 5-FUra AUC in tumors than in plasma (114- to 209-fold higher) and muscle (21.6-fold higher), whereas 5-FUra was not selectively distributed to tumors. In the refractory model, WiDr, 5-FUra AUC in tumors after capecitabine administration was only 62.8 nmol x hr/g, although the level of the intermediate metabolite 5'-dFUrd was high (AUC: 695 nmol x hr/g). The ratio of 5-FUra/5'-dFUrd levels in the WiDr tumors was 0.09, which was 23.8-fold lower than that in the HCT116 tumors. The mechanism of resistance would be the inefficient conversion of 5'-dFUrd to 5-FUra by thymidine phosphorylase in tumors. Thus, capecitabine might show its high efficacy as a result of delivering high levels of 5-FUra selectively to the tumors.
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PMID:Tumor selective delivery of 5-fluorouracil by capecitabine, a new oral fluoropyrimidine carbamate, in human cancer xenografts. 960 32

Capecitabine (N4-pentyloxycarbonyl-5'-deoxy-5-fluorocytidine) is a novel oral fluoropyrimidine carbamate, which is converted to 5-fluorouracil (5-FU) selectively in tumours through a cascade of three enzymes. The present study investigated tissue localisation of the three enzymes in humans, which was helpful for us to design the compound. Carboxylesterase was almost exclusively located in the liver and hepatoma, but not in other tumours and normal tissue adjacent to the tumours. Cytidine (Cyd) deaminase was located in high concentrations in the liver and various types of solid tumours. Finally, thymidine phosphorylase (dThdPase) was also more concentrated in various types of tumour tissues than in normal tissues. These unique tissue localisation patterns enabled us to design capecitabine. Oral capecitabine would pass intact through the intestinal tract, but would be converted first by carboxylesterase to 5'-deoxy-5-fluorocytidine (5'-dFCyd) in the liver, then by Cyd deaminase to 5'-deoxy-5-fluorouridine (5'-dFUrd) in the liver and tumour tissues and finally by dThdPase to 5-FU in tumours. In cultures of human cancer cell lines, the highest level of cytotoxicity was shown by 5-FU itself, followed by 5'-dFUrd. Capecitabine and 5'-dFCyd had weak cytotoxic activity only at high concentrations. The cytotoxicity of the intermediate metabolites 5'-dFCyd and 5'-dFCyd was suppressed by inhibitors of Cyd deaminase and dThdPase, respectively, indicating that these metabolites become effective only after their conversion to 5-FU. Capecitabine, which is finally converted to 5-FU by dThdPase in tumours, should be much safer and more effective than 5-FU, and this was indeed the case in the HCT116 human colon cancer and the MX-1 breast cancer xenograft models.
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PMID:Design of a novel oral fluoropyrimidine carbamate, capecitabine, which generates 5-fluorouracil selectively in tumours by enzymes concentrated in human liver and cancer tissue. 984 91

Orotate phosphoribosyl transferase (OPRT), thymidine phosphorylase (TP), uridine phosphorylase (UP), dihydropyrimidine dehydrogenase (DPD), and thymidylate synthetase (TS) are enzymes which analyze the salvage synthesis within the biosynthesis of the nucleic acid route of colon cancer. These enzymes were measured in carcinoma and normal tissue. OPRT was 0.065 +/- 0.041 nmol/min/mg protein, TP 4.04 +/- 2.81 nmol/min/mg protein, UP 1.79 +/- 1.19 nmol/min/mg protein, DPD 23.8 +/- 12.0 pmol/min/mg protein, and TS 6.1 +/- 4.4 pmol/g tissue in the normal tissue, and OPRT was 0.199 +/- 0.146 nmol/min/mg protein, TP 13.63 +/- 6.04 nmol/min/mg protein, UP 5.84 +/- 2.37 nmol/min/mg protein, DPD 22.0 +/- 13.4 pmol/min/mg protein, TS 16.9 +/- 7.8 pmol/g tissue in the carcinoma. OPRT, TP, and UP in the carcinoma mainly existed about 3.06-3.37 times that in normal tissue and TS at about 2.77 times. No significant difference was seen in DPD. A correlation was found between OPRT in normal tissue and carcinoma. Biosynthesis of nucleic acid via salvage synthesis is actively stimulated. Enzymatic activity related to uracil was high, and was thought to be closely connected to the growth of the cancer.
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PMID:[Analysis of the salvage synthesis within biosynthesis of nucleic acid route in colon cancer]. 1096 98

Identification of the molecular determinants of 5-fluorouracil (5-FU) and irinotecan (CPT-11) efficacy and toxicity is critically important for the development of more efficient and less toxic treatment strategies for patients with colon cancer. We have identified molecular predictors of response to chemotherapy with 5-FU and survival in patients with advanced colorectal cancer. Low gene expression levels of thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD), and thymidine phosphorylase (TP) are associated with response and survival. Preliminary data suggest that gene expression levels of topoisomerase I, p21, bcl-2, and ICE may be predictive of response to therapy with CPT-11. Increased toxicity seen in patients treated with CPT-11 may be explained by polymorphism in the UGT1A1 gene, which is responsible for glucuronidation of the active metabolite of CPT-11.
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PMID:Determinants of prognosis and response to therapy in colorectal cancer. 1117 41

Docetaxel and capecitabine are being prescribed for the treatment of breast cancer. In this study, we tried to identify the optimal administration schedule in combination therapy with these anticancer drugs in human cancer xenograft models. Capecitabine was given p.o. daily for 2 weeks (days 1-14), whereas docetaxel was given i.v. on day 1, day 8, or day 15 in a 3-week regimen to the mice bearing MX-1 human breast cancer xenograft. The combination showed better antitumor efficacy than the monotherapy of either agent in either dosing regimen. However, the most potent and synergistic activity was observed when docetaxel was given on day 8. This potent effect appears to be characteristic of the combination of docetaxel with capecitabine or its intermediate metabolite 5'-deoxy-5-fluorouridine (doxifluridine; 5'-dFUrd). Docetaxel given on day 8 showed a potent effect in combination with 5'-dFUrd, but a much weaker effect was observed in combination with 5-fluorouracil or UFT, a fixed combination of tegafur and uracil. Better efficacy was also observed in the MAXF401 human breast cancer xenograft and in the mouse A755 mammary tumor when docetaxel was given at the middle of the capecitabine or 5'-dFUrd treatment rather than other dosing regimens. In contrast, the efficacy in WiDr human colon cancer xenograft was somewhat better when docetaxel was given on day 1. One possible explanation for the synergy is that docetaxel up-regulates tumor levels of thymidine phosphorylase, the enzyme essential for the activation of capecitabine and 5'-dFUrd to 5-fluorouracil. In fact, docetaxel up-regulated the thymidine phosphorylase levels 4.8- and 1.9-fold in the WiDr and MX-1 models, respectively. However, it did not significantly up-regulate in the MAXF401 and A755 models in which a potent combination effect was observed as well. Other mechanisms, particularly those for the synergy with docetaxel given at the middle during capecitabine/5'-dFUrd administration, would also exist. Based on these observations, clinical studies on the day 8 combination regimen with docetaxel and capecitabine/5'-dFUrd are warranted.
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PMID:Schedule dependency of antitumor activity in combination therapy with capecitabine/5'-deoxy-5-fluorouridine and docetaxel in breast cancer models. 1130 60

The oral fluoropyrimidine, capecitabine is attracting great interest in the context of tumour-selective therapy and rationally designed combination regimens. Agents such as taxanes upregulate thymidine phosphorylase (TP), and there is therefore a clear rationale for their combination with capecitabine. Preclinical studies of capecitabine/taxane combination therapy demonstrated synergistic antitumour activity and phase I studies showed encouraging efficacy. Therefore, a randomised, phase III trial (docetaxel versus docetaxel/capecitabine) has been initiated in anthracycline-refractory metastatic breast cancer patients. Recruitment is complete. In colorectal cancer, capecitabine/oxaliplatin combination therapy is promising and a phase I, dose-finding trial has been conducted in patients with refractory metastatic solid tumours. A similar trial has evaluated capecitabine/irinotecan combination treatment. Capecitabine is also being investigated as adjuvant therapy for colorectal and breast cancers. The primary objective of the ongoing X-ACT trial in almost 2000 Dukes' C colon cancer patients is to demonstrate at least equivalent disease-free survival between capecitabine and the Mayo Clinic regimen. In addition, the CALGB is planning a randomised, phase III trial of capecitabine versus doxorubicin/cyclophosphamide or cyclophosphamide/methotrexate/5-fluorouracil (CMF) as adjuvant treatment in high-risk, node-negative breast cancer patients aged >65 years.
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PMID:Future treatment options with capecitabine in solid tumours. 1184 32

Thymidine phosphorylase (TP; also known as platelet-derived endothelial cell growth factor, PD-ECGF) is an angiogenic factor that is chemotactic for endothelial cells and has been found to induce neovascularization in vivo. TP is frequently overexpressed in human solid tumors, where its expression has been correlated with increased tumor microvessel density, invasion, and metastasis, and shorter patient survival. In this report, TP activity in the WiDr colon carcinoma cell line was found to be induced 100-fold by tumor necrosis factor (TNFalpha), a secretory product of activated macrophages that has indirect angiogenic activities. Increased TP activity was accompanied by increased TP mRNA levels and without an increase in mRNA stability. TNFalpha-induced TP mRNA levels were reduced by mithramycin, a DNA-binding transcription inhibitor specific for GC-rich sequences. Transcriptional regulation by TNFalpha was confirmed by transient transfection of WiDr with upstream TP sequences in a luciferase reporter construct. Deletion analysis of the reporter pinpointed two regions of the TP promoter with regulatory elements for both TNFalpha-inducible and basal expression, and they contained, respectively, three and one consensus binding sites for the Sp1-family of transcription factors. One additional region contributed only to basal TP expression, and it contained three Sp1 sites. TNFalpha-induced TP expression decreased when point mutations were made in three of the four Sp1 sites postulated to contribute to both basal and TNFalpha-inducible expression. Electrophoretic mobility shift assays further demonstrated binding of nuclear Sp1 to these three sites. Sp1-binding activity was also increased in cells treated with TNFalpha. These studies establish a role for Sp1 in the regulation of expression of the angiogenic factor TP in colon cancer WiDr cells.
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PMID:The Sp1 transcription factor contributes to the tumor necrosis factor-induced expression of the angiogenic factor thymidine phosphorylase in human colon carcinoma cells. 1246 67

Platelet derived endothelial cell growth factor/thymidine phosphorylase (PD-ECGF/TP) catalyzes the phosphorolysis of thymidine (TdR) to thymine and deoxyribose-1-phosphate (dR-1-P) and has a pro-angiogenic effect for which dR-1-P may be responsible. Using a purine nucleoside phosphorylase based assay it was found that TdR incubation did not increase dR-1-P accumulation in colon cancer cell line Colo320 and its PD-ECGF/TP transfected variant Colo320TP1. The assay was linear up to 25,000pmol dR-1-P with complete recovery of dR-1-P from cellular extracts. There was a huge discrepancy between thymine production and the measured dR-1-P level, 0.05% of the expected value for dR-1-P was found, indicating that there was a rapid disappearance of dR-1-P. However, in cellular extracts, TdR incubation increased dR-1-P, measurable by trapping, which was inhibited by a thymidine phosphorylase inhibitor. dR-1-P directly added to cellular extracts disappeared within 5-10min. In conclusion, large amounts of dR-1-P are produced by Colo320TP1 cells, which rapidly disappear thus not resulting in a net accumulation of dR-1-P in these cells.
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PMID:Rapid disappearance of deoxyribose-1-phosphate in platelet derived endothelial cell growth factor/thymidine phosphorylase overexpressing cells. 1256 33


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