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

NB1011, a phosphoramidate derivative of (E)-5-(2-bromovinyl)-2'-deoxyuridine, is a novel small molecule anticancer agent. NB1011 is selectively active against tumor cells expressing high levels of thymidylate synthase (TS), a critical enzyme in DNA biosynthesis. NB1011 is different from the current TS-targeted drugs, which require inhibition of TS to be effective, because NB1011 cytotoxicity depends upon activation by TS. Here we report a dose-dependent, antitumor activity of NB1011 against established Tomudex-resistant breast cancer (MCF7TDX) xenografts in athymic mice. Against 5-fluorouracil-resistant colon carcinoma (H630R10) xenografts, NB1011 was as efficacious as irinotecan, a drug recently approved for the treatment of 5-fluorouracil-resistant colon cancer. To gain insight into the mechanisms NB1011 uses to suppress cellular growth, we analyzed the downstream molecular events in the high TS-expressing MCF7TDX and RKOTDX cell lines upon NB1011 treatment. NB1011 treatment increased the mRNA levels of p21, Bax, and GADD45. Furthermore, NB1011 induced p53, p21, and Bax proteins specifically in high TS-expressing tumor cells, whereas no induction was observed in low TS-expressing tumor cells (MCF7) or normal cells (WI38). Cell cycle analysis demonstrated that NB1011 treatment of MCF7TDX and RKOTDX cells resulted in an accumulation of cells in the G2-M phase of the cell cycle. Altogether, our data indicate that the induction of the p53 target genes p21, bax, and GADD45, with a concomitant deregulation of the cell cycle, may represent one of the mechanisms by which NB1011 exerts its growth-suppressive effects.
 ...
PMID:Inhibition of cell growth by NB1011 requires high thymidylate synthase levels and correlates with p53, p21, bax, and GADD45 induction. 1247 50

This study was designed to explore the possible interaction of 5-fluorouracil (5-FU) and 7-ethyl-10-hydroxycamptothecin (SN-38) in vitro. Human colon cancer LoVo cells were treated in both a dose- and time-dependent manner using clinically relevant concentrations of and exposure to 5-FU and/or SN-38. The expression of thymidylate synthase (TS), topoisomerase I, and cell cycle kinetics were evaluated by Western blot analysis and flow cytometry, respectively. Cytotoxicity was evaluated by MTT (3-[4,5-dimethylthiazol-2yl]-2,5-diphenyl tetrazolium bromide) assay. The cytotoxic effects of combination treatment were determined by median effect analysis. Topoisomerase I expression was downregulated following 12 hours of exposure to treatment, and topoisomerase I expression recovered 8 hours after SN-38 was removed. The TS expression was decreased following 24 hours of 5-FU and it remained at reduced levels for > 24 hours after removal of 5-FU. SN-38 induced an arrest at S/G2/M phase, reaching its maximum effect at 12 hours. This cell cycle arrest was reversed 24 hours after SN-38 was removed. 5-FU induced an arrest at the S phase, and maximum arrest occurred at 12 hours and lasted for > 48 hours. After 12 hours of sequential SN-38, LoVo cells were arrested in S phase, thereby potentiating the effect of 5-FU. Cytotoxicity studies confirmed the synergistic interaction between 5-FU and irinotecan. These findings suggest that the proper sequencing of 5-FU/irinotecan depends on regulation of topoisomerase I, and cell cycle kinetics
 ...
PMID:Combination of 5-fluorouracil and irinotecan on modulation of thymidylate synthase and topoisomerase I expression and cell cycle regulation in human colon cancer LoVo cells: clinical relevance. 1248 36

In this study we investigated the relationship between thymidylate synthase (TS) protein expression, evaluated by Western blotting analysis and by immunohistochemistry (IHC), and growth rate in human colon xenograft tumors in nude mice. Human colon cancer cell lines were used to induce xenograft tumors and the tumor mass growth rate was calculated by measuring tumor size variations over time. TS 106 monoclonal antibody was used for both Western blotting and IHC TS detection. Tumor cell growth fraction was measured by Ki67/MIB1 immunolabeling and tumor cell growth rate by evaluating the mean nucleolar size in silver-stained sections. TS Western blotting values were related to tumor mass growth rate (p<0.001) and cell growth rate (p=0.002) but not to cell growth fraction (p=0.676). The degree of the IHC staining showed only a trend to be associated with TS protein expression measured on Western blotting, and was not related either to tumor mass growth or cell proliferation rate. Tumor xenografts were also characterized for TS promoter tandem repeat and p53 status. No relationship was observed between these variables and TS expression evaluated by both Western blotting and IHC analysis. Our results demonstrate that TS expression evaluated by Western blotting analysis is directly related to the tumor mass growth rate and question the use of the IHC approach to obtain precise quantitative information on TS expression in tumor samples.
 ...
PMID:Evaluation of thymidylate synthase protein expression by Western blotting and immunohistochemistry on human colon carcinoma xenografts in nude mice. 1248 85

5-Fluorouracil (5-FU) is the most routinely administered drug in the treatment of colon cancer. The main mechanism of the drug is not completely understood and its method of administration has been strongly disputed. A 24-hour infusion of 5-FU has clinically yielded better response rates and lower toxicities in comparison to bolus administration, but an exploration into possible mechanisms needs to be performed. Experiments were conducted with two 5-FU resistant cell lines where cytotoxicity, thymidylate synthase (T.S.) activity, thymidine kinase (T.K.) activity, DNA and RNA incorporation, and T.S. expression were contrasted between a 10 microM/24 hour administration of 5-FU (simulating continuous exposure) and a 100 microM/1 hour schedule (simulating bolus administration). After 6 days from the initial exposure, the 10 microM/24 hour schedule (schedule A) inhibited more cell growth than the 100 microM/1 hour regimen (schedule B) by more than 38% and 17% in the two cell lines. After the 6-day observation, schedule A inhibited twice as much T.S. activity as schedule B. Incorporation of [14C]-5-FU into DNA and total RNA was higher in cells exposed to schedule A in comparison to schedule B over the 6 days. T.S. expression and T.K. activity patterns were variable over time. Thus, the exposure of 10 microM/24 hour 5-FU results in superior cytotoxicity when compared to a 100 microM/1 hour regimen and its effectiveness may be explained mechanistically by T.S. activity and DNA and RNA incorporation.
 ...
PMID:Cytotoxic effects and mechanisms of an alteration in the dose and duration of 5-fluorouracil. 1268 Feb 47

Gene transfer-based myeloprotection strategies against chemotherapy require the development of effective drug resistance genes or gene combinations. Our laboratory has previously generated drug-resistant mutants of dihydrofolate reductase (DHFR F/S) and thymidylate synthase (TS G52S) for myeloprotection against methotrexate (MTX) and 5-fluorouracil (5-FU), respectively. For the purpose of conferring dual myeloprotection against both MTX and 5-FU, we have generated two retroviral constructs encoding both DHFR F/S and TS G52S as a fusion protein (DHFR F/S-TS G52S) or as individual proteins from a bicistronic gene. The DHFR F/S-TS G52S fusion protein is functional and exhibits kinetic properties similar to that of the individual mutant enzymes. NIH 3T3 cells and mouse bone marrow progenitors retrovirally transduced with the fusion DHFR F/S-TS G52S cDNA provided similar levels of resistance to MTX and 5-FU as cells expressing the individual mutant enzymes and higher levels of resistance to MTX than cells expressing DHFR F/S from the 3' end of a bicistronic gene. As MTX and 5-FU are used in combination therapy for diseases such as breast and colon cancer, this fusion gene may be useful in the clinic to reduce myelosuppressive toxicity associated with this drug combination.
 ...
PMID:Retroviral transduction of a mutant dihydrofolate reductase-thymidylate synthase fusion gene into murine marrow cells confers resistance to both methotrexate and 5-fluorouracil. 1269 9

Pemetrexed (Alimta); Eli Lilly and Co., Indianapolis, IN, USA) is a unique multitargeted antifolate that inhibits at least three enzymes, thymidylate synthase, dihydrofolate reductase and glycinamide ribonucleotide formyltransferase. This novel drug is being evaluated in a comprehensive clinical programme for use in both front-line and second-line therapies. It has shown broad activity in a number of solid tumours, including colon cancer, breast cancer, lung cancer, head and neck, cervical cancer and others. While a number of antifolates have been evaluated in clinical trials, further development has been stopped or delayed by the occurrence of life-threatening toxicities. Similar trends were also initially observed with pemetrexed as well, but investigators later showed that these toxicities could be minimised with folic acid and vitamin B(12) supplementation included in the treatment regimen. Preliminary data indicate that this supplementation does not hamper drug efficacy in most tumour types and in many cases, supplemented patients exhibit improved clinical outcome. Here, the current data for pemetrexed in treating thoracic malignancies are reviewed, with special focus on malignant pleural mesothelioma and non-small cell lung cancer.
 ...
PMID:Pemetrexed and its emerging role in the treatment of thoracic malignancies. 1272 Apr 95

Analysis of thymidine phosphorylase (TP), thymidylate synthase (TS) and dihydropyrimidine dehydrogenase (DPD) or their mRNA are now being applied before-the start of chemotherapy to predict the therapeutic efficacy. Although these key enzymes were reported to be basically independent, we found the differences in TS between cancer and adjacent mucosa was reversely correlated with the difference in DPD. We found a significant relationship between TP and DPD in 52 patients with colon cancer. TP and DPD were measured by EIA. Statistical analysis was made non-parametrically using Statview 5.0. TP was significantly higher in cancer (78 +/- 58 U/mg protein) than in the adjacent mucosa (43 +/- 24 U/mg protein). Conversely, DPD was significantly lower in cancer(43 +/- 32 U/mg protein) than in the adjacent mucosa (55 +/- 18 U/mg protein). The amount of TP and DPD in cancer were not correlated with the clinicopathological parameters. TP was significantly (r = 0.70) correlated with DPD in cancer but not in adjacent mucosa. The difference in TP between cancer and adjacent mucosa was significantly (r = 0.69) correlated with the difference in DPD as well. In the colon cancer with low TP, DPD in cancer is lower than in the adjacent mucosa, however, the more TP in cancer increased, the higher the DPD in cancer increased over that in the adjacent mucosa. Modulation of DPD as well as TP may be necessary when high levels of TP or DPD are measured in the cancer tissue. The understanding of the basic relationship among these key enzymes will improve the 5-FU-based chemotherapeutic prediction.
 ...
PMID:[Thymidine phosphorylase is correlated with DPD in colon cancer]. 1272 80

The expression levels of thymidylate synthase (TS) affect the sensitivity of tumor cells to fluorinated pyrimidine cytotoxic agents and determine the response of patients with colorectal cancer to fluorinated-pyrimidine-based chemotherapy. The correlation between the expression of TS and the prognosis of patients with colorectal cancer was examined in a prospective study. Evaluation of biomarkers including TS expression was performed using tumor specimens from 229 colorectal cancer patients. Immunohistochemical analysis of TS expression was performed using an antibody raised against a C-terminal epitope (D186-V313) of the human TS. The intensity of TS staining and the expression of other biomarkers were blindly scored. The five-year survival rates were 63.4% and 85.6% among patients with high and low intratumoral TS expressions, respectively (p=0.0007). Similarly, the disease-free survival (DFS) rate was 51.2% and 80.3% in the high and low TS expression groups, respectively (p=0.0004). In a subset analysis of Dukes' stage C patients, the survival and DFS rates were 44.0% and 40.0% in the high TS expression group, and 73.5% and 67.4% in the low TS expression group, respectively. Significant differences were observed in both survival (p=0.0048) and DFS (p=0.0054) rates. No significant correlation was observed between the expression of other biomarkers and prognosis. Significantly poorer prognosis of curatively resected colon cancer in patients with high TS expression levels in tumor tissue was confirmed by a double-blind prospective study conducted on samples obtained from patients enrolled in an adjuvant immunochemotherapy randomized clinical trial.
 ...
PMID:Thymidylate synthase expression as a predictor of the prognosis of curatively resected colon carcinoma in patients registered in an adjuvant immunochemotherapy clinical trial. 1288 62

Pemetrexed (ALIMTA, MTA) is a novel thymidylate synthase (TS) inhibitor and has shown activity against colon cancer, mesothelioma and nonsmall-cell lung cancer. We induced resistance to Pemetrexed in the human colon cancer cell line WiDr by using a continuous exposure to stepwise increasing Pemetrexed concentrations (up to 20 microM) as well as a more clinically relevant schedule with intermittent exposure (up to 50 microM) for 4 hr every 7 days, resulting in WiDr variants WiDr-cPEM and WiDr-4PEM, respectively. However, using the same conditions, it was not possible to induce resistance in the WiDr/F cell line, a variant adapted to growth under low folate conditions. Mechanisms of resistance to Pemetrexed were determined at the level of TS, folylpolyglutamate synthetase (FPGS) and reduced folate carrier (RFC). WiDr-4PEM and WiDr-cPEM showed cross-resistance to the polyglutamatable TS inhibitor Raltitrexed (6- and 19-fold, respectively) and the nonpolyglutamatable TS-inhibitor Thymitaq (6- and 42-fold, respectively) but not to 5-fluorouracil. The ratios of TS mRNA:beta actin mRNA in WiDr-4PEM and WiDr-cPEM were 5-fold (P=0.01) and 18-fold (P=0.04) higher, respectively, compared to WiDr (ratio: 0.012). In addition, TS protein expression in the resistant WiDr variants was elevated 3-fold compared to WiDr, while the catalytic activity of TS with 1 microM dUMP increased from 30 pmol/hr/10(6) cells in WiDr cells to 2201 and 7663 pmol/hr/10(6) cells in WiDr-4PEM and WiDr-cPEM, respectively. The activity of FPGS was moderately decreased, but not significantly different in all WiDr variants. Finally, no evidence was found that decreased catalytic activity of RFC was responsible for the obtained Pemetrexed resistance. Altogether, these results indicate that resistance to Pemetrexed in the colon cancer cell line WiDr was solely due to upregulation of TS of which all related parameters (mRNA and protein expression and TS activity) were increased, rather than alterations in FPGS or RFC activity.
 ...
PMID:Induction of resistance to the multitargeted antifolate Pemetrexed (ALIMTA) in WiDr human colon cancer cells is associated with thymidylate synthase overexpression. 1290 42

The role of cysteine sulfhydryl residues on the RNA binding activity of human thymidylate synthase (TS) was investigated by mutating each cysteine residue on human TS to a corresponding alanine residue. Enzymatic activities of TS:C43A and TS:C210A mutant proteins were nearly identical to wild-type TS, while TS:C180A and TS:C199A mutants expressed >80% of wild-type enzyme activity. In contrast, TS:C195A was completely inactive. Mutant proteins, TS:C195A, TS:C199A and TS:C210A, retained RNA binding activity to nearly the same degree as wild-type human TS. RNA binding activity of TS:C43A was reduced by 30% when compared to wild-type TS, while TS:C180A was completely devoid of RNA binding activity. In vitro translation studies confirmed that mutant proteins TS:C43A, TS:C195A, TS:C199A and TS:C210A, significantly repressed human TS mRNA translation, while TS:C180A was unable to do so. To confirm the in vivo significance of the cysteine sulfhydryl residue, mutant proteins TS:C180A and TS:C195A were each expressed in human colon cancer HCT-C18:TS(-) cells that expressed a functionally inactive TS. A recombinant luciferase reporter gene under the control of a TS-response element was co-transfected into these same cells, and luciferase activity increased in the presence of the TS:C195A mutant TS protein to a level similar to that observed upon expression of wild-type TS protein. In contrast, luciferase activity remained unchanged in cells expressing the TS:C180A mutant protein. Taken together, these findings identify Cys-180 as a critical residue for the in vitro and in vivo translational regulatory effects of human TS.
 ...
PMID:Role of cysteine amino acid residues on the RNA binding activity of human thymidylate synthase. 1290 31


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>