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)

To date, the best treatment modality for colorectal cancer is a surgical excision of the primary tumour. Adjuvant therapy can be added to the surgical treatment and can consist of adjuvant chemo-, immuno- or radiotherapy. In the U.S.A., adjuvant chemotherapy with 5-fluorouracil (5FU) and levamisole is advocated as standard treatment for patients with localised poor risk (Dukes stage C) colon cancer. Not every clinician is convinced of the usefulness of adjuvant chemotherapy. Therefore, confirmatory clinical trials are still ongoing to compare no adjuvant treatment with 5FU/levamisole adjuvant treatment. Treatment with 5FU/leucovorin has been shown to be effective as adjuvant therapy. In rectal cancer, radiotherapy can be added to the primary surgical treatment. It is still unproven whether radiotherapy should be given pre-, peri, or postoperatively, and whether chemotherapy should be added to this multimodality regimen. If chemotherapy is applied as a radio-sensitiser, a continuous infusion is preferable to daily bolus injection. Much effort has been put into the improvement of the response rate of 10-15% 5FU, used as a single agent in the treatment of advanced colorectal cancer. Biochemical modulation of 5FU with leucovorin and interferon, different schedules of 5FU administration and hepatic arterial therapy have all been attempted. Higher response rates have been reported with these treatment modalities, unfortunately without improvement of survival, except for the intra-arterial approach. Recently, two new drugs have shown efficacy in the treatment of advanced colorectal cancer. A phase II trial with Tomudex (ZD1694), a new antifolate thymidiylate synthase inhibitor, produced a response rate of 25% in patients with advanced colorectal cancer.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Current chemotherapeutic possibilities in the treatment of colorectal cancer. 757 20

Inhibition of thymidylate synthase (TS) may increase incorporation of thymidine analogues into DNA, leading to increased inhibition of colony formation in tumor cells. We have reported previously that TS inhibition by N-(5-[N-(3,4-dihydro-2-methyl-4-oxoquinazolin-6,-ylmethyl)-N -methylamino]-2 - thenoyl)-L-glutamic acid (ICI D1694 or Tomudex), a folate-based TS inhibitor, increases the cytotoxicity of iododeoxyuridine (IdUrd), a thymidine analogue, in MGH-U1 human bladder and HCT-8 human colon cancer cells. N6-[4-(Morpholinosulfonyl)benzyl]-N6-methyl-2,6-diaminobenz[ cd]-indole glucuronate (AG-331) differs from ICI D1694 in that it is a de novo designed lipophilic TS inhibitor, it does not require a specific carrier for cellular uptake, and it does not undergo intracellular polyglutamation. Exposure of MGH-U1 cells to 5 microM AG-331 for 24 hr decreased clonogenic survival by 30%, but almost completely inhibited TS activity. IdUrd is a cytotoxic thymidine analogue, with IC50 and IC90 values after 24-hr exposures in MGH-U1 cells of 13 and 81 microM, respectively. The combination of IdUrd and AG-331 resulted in an enhanced antitumor effect, as compared with the effect of either agent alone. The cytotoxic IC50 of IdUrd decreased from 13 to 1.5 microM, and the IC90 decreased from 81 to 5 microM with the addition of 5 microM AG-331. Biochemical studies of the combination revealed that pretreating MGH-U1 cells with 5 microM AG-331 increased IdUrd incorporation into cellular DNA by 3.8-fold. This increased incorporation was associated with a greater proportion of DNA single-strand breaks than observed with either agent alone, and the combination of 5 microM AG-331 plus IdUrd produced up to a 2.5-fold increase in DNA single-strand breaks as compared with IdUrd alone. The effects of AG-331, IdUrd, and the combination of IdUrd and AG-331 on the colony-forming ability of normal human bone marrow CFU-GM cells was determined as a measure of myelosuppression. The combination of IdUrd and AG-331, at the same concentrations as those used in the MGH-U1 cells, produced a wider therapeutic index relative to that of IdUrd alone, and the therapeutic index for the combination was 6.5, as compared with 4.0 for IdUrd plus ICI D1694 in previous studies from this laboratory. These observations suggest that the combination of IdUrd and AG-331 may enhance antitumor effects with minimal myelosuppression in vivo.
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PMID:Biochemical modulation of iododeoxyuridine by N6-[4-(morpholinosulfonyl)benzyl]-N6-methyl-2,6-diaminobenz[cd]indole glucuronate (AG-331) leading to enhanced cytotoxicity. 760 45

Carboplatin is a better-tolerated alternative to cisplatin. JM216, the first p.o.-administrable platinum complex possesses toxicities comparable to carboplatin in Phase I studies. Together with the trans-platinum complex JM335, it provides new chemical guidelines for the development of compounds that may circumvent cisplatin resistance in tumors. Systematic structure-activity investigations have led to the discovery and development of ZD1694 (Tomudex), an inhibitor of thymidylate synthase that exploits both the reduced folate carrier and folylpolyglutamate synthetase as major determinants of its growth-inhibitory activity. Phase II studies have revealed encouraging activity against colon cancer, and Phase III studies are nearing completion. An associated structure-activity investigation has led to the development of ZD9331, a potent thymidylate synthase inhibitor which exploits the reduced folate carrier for cell entry, but which is independent of polyglutamation for its thymidylate synthase-inhibitory activity. This compound possesses antitumor activity in vivo and has been selected for full development.
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PMID:Initiatives with platinum- and quinazoline-based antitumor molecules--Fourteenth Bruce F. Cain Memorial Award Lecture. 779 1

The cytotoxicity of idoxuridine (IdUrd), a thymidine analogue, and ICI D1694 (D1694), a folate-based thymidylate synthase (TS) inhibitor, were examined individually and in combination in two human tumor cell lines. MGH-U1 bladder cancer and HCT-8 colon cancer cells were grown as monolayer cultures with and without thymidine. The cytotoxicity of these agents alone and in combination were determined using normal human bone marrow colony-forming unit, granulocyte-macrophage (CFU-GM) as a surrogate for myelosuppression in vivo. Thymidylate synthase inhibition, IdUrd incorporation into DNA, and DNA single-strand breaks were measured in each cell line and related to cytotoxicity. The cytotoxicity of a 24-h exposure to IdUrd or D1694 increased with drug concentration in each cell line. The drug concentrations producing 50% and 10% clonogenic survival in MGH-U1 cells, respectively, were 0.006 and 0.009 microM for D1694 and 13.0 and 81.0 microM for IdUrd. Those for HCT-8 cells, respectively, were 0.009 and 0.018 microM for D1694 and 7.5 and 20.5 microM for IdUrd. The cytotoxicity of IdUrd combined with D1694 was synergistic in both MGH-U1 and HCT-8 cells as determined by median-effect analysis. The addition of thymidine at concentrations of 0.1, 0.3, and 1.0 microM to the culture medium did not decrease the cytotoxicity of D1694 in either tumor cell line. TS inhibition using the whole cell assay was observed with only D1694, producing 50% inhibition of TS activity at 0.002 microM for MGH-U1 and 0.007 microM for HCT-8 cells. IdUrd did not inhibit TS activity, nor did it enhance the TS inhibitory effects of D1694. The incorporation of IdUrd into DNA increased with increasing concentrations of D1694. This increased DNA incorporation correlated with the increase in DNA single-strand breaks. DNA single-strand breaks paralleled cytotoxicity. CFU-GM survival, exposed to the same drug concentrations as those used in the tumor cell lines, revealed that the therapeutic index was greater for the combination than for either agent alone. These findings suggest that IdUrd plus D1694 is a promising new drug combination, which may have a favorable therapeutic index in vivo.
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PMID:ICI D1694 and idoxuridine: a synergistic antitumor combination. 803 97

The cytotoxicity of 3'-azido-3'-deoxythymidine (AZT), a thymidine analogue, and ICI D1694, a folate-based thymidylate synthase (TS) inhibitor, was examined individually and in combination in two human tumor cell lines, MGH-U1 bladder cancer and HCT-8 colon cancer cells, grown as a monolayer culture with and without thymidine (TdR). In addition, TS inhibition, [3H]AZT incorporation into DNA, [3H]AZT-MP (monophosphate) production, and DNA double-strand breaks were measured. Twenty-four hour exposure of AZT at 0.5, 5, 50 and 500 microM was not cytotoxic to MGH-U1 or HCT-8 cells in a colony-forming assay. ICI D1694 cytotoxicity increased with drug concentration, and the IC50 and IC90, respectively, were 0.0064 and 0.01 microM in MGH-U1 cells and 0.009 and 0.018 microM in HCT-8 cells. TdR in concentrations of 0.1 to 1.0 microM did not affect ICI D1694 cytotoxicity in either cell line. AZT at 5, 50 or 500 microM increased ICI D1694 cell kill. The IC50 and IC90 for MGH-U1 were 0.0037 and 0.0075 microM for 50 microM AZT combined with ICI D1694. The IC50 and IC90 for HCT-8 were 0.0075 and 0.015 microM for 50 microM AZT plus ICI D1694. The incorporation of [3H]AZT into DNA increased with increasing concentrations of ICI D1694. Concentrations producing an IC50 and IC90 of ICI D1694, respectively, increased incorporation of [3H]AZT into DNA by 319 and 569% in MHG-U1, and 243 and 400% in HCT-8 cells. The formation of [3H]AZT-MP paralleled the increase in [3H]AZT incorporated into DNA. AZT, ICI D1694 and the combination of AZT and ICI D1694 caused DNA double-strand breaks, with the combination of these agents being additive. CFU-GM survival, exposed to drug concentrations, as those used in the tumor cell lines, revealed that the therapeutic index was greater for AZT plus ICI D1694 than for ICI D1694 alone. These findings suggest that AZT plus ICI D1694 may increase antitumor effect with minimal myelosuppression. We conclude that AZT increases the cytotoxicity of ICI D1694 with increasing AZT incorporation into DNA.
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PMID:Combination studies with 3'-azido-3'-deoxythymidine (AZT) plus ICI D1694. Cytotoxic and biochemical effects. 826 49

After many years, during which the assumption prevailed that adjuvant chemotherapy was of no benefit in patients with resectable adenocarcinoma of the colon, findings of several large USA studies published from the late 1980s have caused a marked shift in surgical and medical opinion. Although results in patients with Dukes' B disease have not shown any clear benefit, the efficacy of adjuvant chemotherapy has nevertheless been shown in those with Dukes' C colon cancer. As a result, the Mayo regimen of 5-fluorouracil (5-FU) with low-dose leucovorin (LV) has become accepted as standard adjuvant therapy in these patients. However, the disadvantages associated with standard 5-FU-based treatment, particularly those relating to its toxicity and inconvenience of administration, have generated interest in other regimens and agents. The novel direct and specific thymidylate synthase inhibitor raltitrexed ('Tomudex') has been associated with similar objective response rates to standard therapy with 5-FU plus LV in patients with advanced colorectal cancer. In addition, raltitrexed has an attractive tolerability profile compared with that of 5-FU plus LV (specifically with respect to lower incidences of mucositis and leucopenia), and the simple 3-weekly administration schedule may be considered more convenient by many patients and may reduce healthcare resource consumption. To investigate alternatives to the Mayo regimen in the adjuvant treatment of Dukes' C adenocarcinoma of the colon, two large European trials have been set up: (1) PETACC-1 (first Pan-European Trial for Adjuvant Treatment of Colon Cancer), to compare raltitrexed with the Mayo regimen of 5-FU and low-dose LV; (2) PETACC-2 (second Pan-European Trial), to compare the Mayo regimen with three regimens in which 5-FU is given by prolonged infusion. These trials will provide valuable international data to add to those from the USA and will assess the place of raltitrexed in the adjuvant treatment of Dukes' C colon cancer. They will also compare directly for the first time infusional and bolus 5-FU regimens in the adjuvant setting.
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PMID:The establishment of a large collaborative trial programme in the adjuvant treatment of colon cancer. 957 52

The quinazoline folate analogue raltitrexed (ZD1694; Tomudex) and the camptothecin derivative irinotecan are two new agents showing clinical activity against colorectal cancer. To identify the optimal conditions to achieve synergistic cytotoxicity before the clinical development of their combination, we explored the interactions between ZD1694 and the active metabolite of irinotecan, 7-ethyl-10-hydroxycamptothecin (SN-38), in vitro. Cytotoxicity was evaluated with a clonogenic assay using the human colon cancer cell line HCT-8. Different schedules of administration and different dose ratios of the two agents were compared and evaluated for synergism, additivity, or antagonism with a quantitative method based on the median-effect principle of Chou and Talalay (T. C. Chou and P. Talalay, Adv. Enzyme Regul., 22: 27-55, 1984). Sequential short-term (1 and 4-h) exposures to SN-38 followed by ZD1694 resulted in synergistic cytotoxicity at broad dose-effect ranges. At a high level of cell kill, the synergism was greater when either equiactive doses of the two agents or higher relative doses of ZD1694 were used. A 24-h interval between exposure to SN-38 and ZD1694 significantly enhanced the magnitude of the synergy (P = 0.001). The opposite sequence or simultaneous exposures produced significantly less potentiation or nearly additive interactions (P = 0.0006 and P < 0.0001). The synergism was completely lost under conditions of more prolonged drug exposure (24-h continuous exposure). In conclusion, in this in vitro model of human colon cancer, ZD1694 and SN-38 produced synergistic cytotoxicity. Our findings support the clinical use of this combination and provide a rationale for a clinical trial using sequential short-term exposures to equiactive doses of SN-38 and ZD1694 administered sequentially with a 24-h interval.
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PMID:Schedule-dependent synergism between raltitrexed and irinotecan in human colon cancer cells in vitro. 960 93

Thymidylate synthase (TS), a critical enzyme in the de novo synthesis of thymidylate, is an important target for fluoropyrimidines and folate-based TS inhibitors. In a panel of 13 nonselected human colon cancer cell lines, we evaluated the role of TS levels in sensitivity to 5-fluorouracil (5FU) and four folate-based TS inhibitors that have been introduced recently into the clinic: ZD1694 (Tomudex, Raltitrexed, TDX), GW1843U89 (GW), LY231514 (LY), and AG337 (Thymitaq, AG). Because the latter compounds have different transport and polyglutamylation characteristics, we also related these parameters with drug sensitivity, measured by the sulforhodamine B assay after 72 h of drug exposure. For 5FU, the IC50s varied from 0.8 to 43.0 microM. Leucovorin (LV) potentiated the activity of 5FU in only 4 of 13 cell lines. Sensitivity to folate-based TS inhibitors was variable; IC50s were in the range of: 5.3-59.0 nM TDX; 11.0-1570 nM LY; and 0.5-8.9 nM GW. Eleven of 13 cell lines had an IC50 for AG between 1.3 and 5.3 microM. Two cell lines were resistant to AG, Colo201 and SW1116, with IC50s of 27 and 29 microM, respectively. TS catalytic activity (conversion of dUMP to dTMP) varied from 62 to 777 pmol/h/10(6) cells. The number of FdUMP binding sites varied from 32 to 231 fmol/10(6) cells. Regression analysis showed a significant relation between TS catalytic activity and IC50s for 5FU and 5FU/LV. Kis for FdUMP showed a significant Spearman rank correlation with the IC50s of AG and GW. The role of antifolate transport, accumulation, and polyglutamylation was determined with [3H]methotrexate (MTX) as a reference compound. [3H]MTX influx via the reduced folate carrier varied from 18.6 to 150 fmol/10(6) cells/min. Folylpolyglutamate synthetase (FPGS) activity showed a range from 47 to 429 pmol/10(6) cells/h. A total of 24 h of [3H]MTX accumulation showed a 20-fold variation, from 1.2 to 21.8 pmol/10(6) cells. FPGS levels showed a Spearman rank positive correlation with cytotoxicity to TDX. In conclusion, in a heterogeneous nonselected human colon cancer cell line panel, the best predictor for sensitivity to 5FU and 5FU/LV was TS activity. Multiple sensitivity determinants were of importance for antifolate TS inhibitors, including FPGS activity and TS enzyme kinetics.
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PMID:Thymidylate synthase level as the main predictive parameter for sensitivity to 5-fluorouracil, but not for folate-based thymidylate synthase inhibitors, in 13 nonselected colon cancer cell lines. 1010 Jul 18

The cytotoxicity and metabolic effects of two thymidylate synthase (TS) inhibitors, Tomudex (Raltitrexed, ZD1694) and GW1843U89, were studied in WiDr colon cancer cells under four different growth conditions: as standard monolayers and as postconfluent multilayers grown under either high (WiDr, 8.8 microM folic acid) or low (WiDr/F, 1 nM leucovorin) folate conditions. Both GW1843U89 and ZD1694 were 13-15-fold more active against WiDr/F than WiDr cells when cultured as monolayers (IC50s in WiDr/F cells were 0.22 and 0.39 nM, respectively). WiDr cells were markedly less sensitive to the drugs when grown as multilayers (4-15-fold), in contrast to the WiDr/F cells, which were equally sensitive. However, total growth inhibition could not be achieved in WiDr multilayers (concentration causing total growth inhibition > 10,000 nM), whereas in WiDr/F multilayers, it could be achieved at 0.42 nM ZD1694 and 150 nM GW1843U89. Growth conditions markedly affected the TS levels when using different enzyme assays. At nonsaturating substrate concentrations, the catalytic activity of TS was similar in mono- and multilayers grown under high folate conditions but lower in multilayers at saturating concentrations. In cells grown under low folate conditions, TS catalytic activity was 3-6-fold lower in multilayers than in monolayers. This was consistent with a decrease in the number of S-phase cells in multilayers. Western blotting revealed less pronounced (2-3-fold) differences in the TS protein content. Exposure of the cells for 24 h to the drugs increased the TS levels by 4-fold. Because this increase in TS levels might explain the decrease in sensitivity to the TS inhibitors, we measured TS inhibition (TSI) by the drugs in intact cells using the TS in situ assay. GW1843U89 was more active than ZD1694. However, after 4 h of exposure in WiDr/F mono- and multilayers, TSI was in the same range for both drugs [50% TSI (TSI50), 0.5-1.7 nM]. In WiDr cells, the TSI50 for ZD1694, but not GW1843U89, was 10 times higher in the multilayers as compared to the monolayers. Despite the increase in TS protein levels, the extent of TSI was similar or even more pronounced in both cell lines grown as either multi- or monolayers. Because the cells were grown under depleted and folate-rich conditions that may affect folate uptake, we measured folate transport using methotrexate (MTX) as the reference drug for the activity of the reduced folate carrier. MTX uptake was 4-fold lower in multilayers compared to monolayers in both WiDr and WiDr/F cells. Uptake of MTX was 5-fold more effective in WiDr/F cells than in WiDr cells in both mono-and multilayers. In conclusion, the resistance of WiDr multilayers to the novel antifolates ZD1694 and GW1843U89 may be due to the high folate medium concentrations, which may be responsible for impaired drug uptake along with less effective TSI. In contrast, WiDr/F monolayers and multilayers were very sensitive to these antifolates. These effects of folate homeostasis may explain some of the variable results seen in treatment of solid tumors with new antifolate TS inhibitors.
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PMID:Determinants of activity of the antifolate thymidylate synthase inhibitors Tomudex (ZD1694) and GW1843U89 against mono- and multilayered colon cancer cell lines under folate-restricted conditions. 1055 30

Raltitrexed (Tomudex), a novel folate-based inhibitor of thymidylate synthase, has demonstrated anti-tumour efficacy comparable with 5-fluorouracil and leucovorin in patients with advanced colorectal cancer (CRC). This phase II study was conducted to evaluate the anti-timor efficacy and tolerability of raltitrexed in patients with advanced CRC who had received one previous chemotherapy regimen. Raltitrexed was administered at a dose of 3.0 mg/m2 i.v. over 15 min once every 3 weeks. Of 43 eligible patients, 53% had colon cancer and 47% rectal cancer. Objective responses were observed in 16% of patients [95% confidence interval (CI): 7-31%; seven partial responses). The median duration of response was 101 days (range: 45-239 days), the median overall duration of response was 145 days (range: 104-302 days) and the median survival was 11.6 months (95% CI: 9.4-14.7 months). Liver metastases showed a 17% (three of 18) response rate and lung metastases a 12% (three of 25) response rate. Adverse events of grade 3 or 4 reported for more than 5% of patients were neutropenia (23%), leukopenia (9%), reversible SGPT increase (7%) nausea/vomiting (19%), anorexia (14%), asthenia (9%) and hypotension (7%). Grade 3 or 4 diarrhea, stomatitis and alopecia were not observed. In summary, raltitrexed had an acceptable toxicity profile and promising anti-tumor activity against advanced CRC in patients who had received prior chemotherapy. Further clinical trials of combination chemotherapy using raltitrexed are warranted.
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PMID:Phase II study of raltitrexed (Tomudex) in chemotherapy-pretreated patients with advanced colorectal cancer. Tomudex Cooperative Study Group. 1057 7


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