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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Cancer chemotherapy and pharmacology 35 (1995), S. 387-390 
    ISSN: 1432-0843
    Keywords: Key words: AZT ; AG-331 ; Thymidylate synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We have reported that noncytotoxic concentrations of 3′-azido-3′-deoxythymidine (AZT) increase the cytotoxicity of ICI D1694, a folate-based thymidylate synthase (TS) inhibitor, with increasing AZT incorporation into DNA. We postulated that the inhibition of TS by ICI D1694 would decrease 5’-deoxythymidine triphosphate (dTTP) pools, which compete with AZT triphosphate (AZT-TP) as a substrate for DNA polymerase. Furthermore, the inhibition of TS would increase the activity of both thymidine kinase (TK) and thymidylate kinase (TdK). Each of these consequences of TS inhibition would favor more incorporation of AZT into DNA. Thus, we reasoned that other TS inhibitors should also result in increased AZT incorporation into DNA and, perhaps, in increased cytotoxicity. N 6-[4-(Morpholinosulfonyl)benzyl]-N 6-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. This potent TS inhibitor causes minimal cytotoxicity in MGH-U1 human bladder cancer cells. A 24-h exposure to 5 μM AG-331 causes almost complete TS inhibition but only 35% cell kill. The combination of AZT and AG-331 in MGH-U1 cells resulted in an enhanced antitumor effect relative to that of each agent alone; 50 μM AZT, noncytotoxic alone, increased the cell kill of induced by AG-331 from 35% to 50%. Biochemical studies of this combination revealed that simultaneous treatment with 5 μM AG-331 plus 1.8 μM [3H]-AZT produced as much as a 68%±7% increase in AZT incorporation into DNA. This observation was associated with an increase in DNA single-strand breaks, measured as comet tail moment, of up to 6.6-fold. These studies support our original premise that TS inhibition favors increased incorporation of AZT into DNA and that the combination causes more cell kill than either drug alone in MGH-U1 cells.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0843
    Keywords: 5-Fluorouracil ; Interferon ; Colorectal cancer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Modulation of 5-fluorouracil (FUra) using leucovorin (LV) is a standard treatment approach in patients with metastatic colorectal cancer. Modulation of FUra with interferon alfa has also shown some promise. Laboratory data have demonstrated increased cytotoxicity when FUra is combined with both LV and interferon. The current study examined the effects of double modulation of FUra using LV and interferon. Patients with measurable advanced colorectal cancer received bolus FUra 375 mg/m2 plus LV 20 mg/m2 daily for 5 days, repeated every 28 days. Recombinant human interferon alfa-2a, 3 million IU/m2 subcutaneously, was given daily on the days of chemotherapy then three times weekly. There was one complete response and nine partial responses (10/41) seen for an overall response rate of 24% (95% CI 12.0–40.0%). Overall, 70% of patients experienced one or more episodes of nonhematologic toxicity of grade 3 or more. Weight loss was common, with a mean decrease of 2.9 kg over the first two months (P〈0.0001). Improvements in tumor-related symptoms were balanced by increased fatigue and a deterioration in body weight and performance status. There was no evidence of progressive changes in FUra metabolism from interferon usage.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0843
    Keywords: Key words Irinotecan ; Deoxynucleotide pools ; Thymidylate synthase ; Fluoropyrimidines ; Colon cancer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Purpose: To determine the effect of combined treatment with 7-ethyl-10-hydroxycamptothecin (SN-38, the active metabolite of irinotecan) and 5-fluorouracil/folinic acid (5FU/FA) in vitro using HCT-8 human intestinal adenocarcinoma cells. Methods: Cell survival was examined using colony forming assays. Cell cycle distribution before and after treatment was assessed by flow microfluorimetry. Levels of thymidylate synthase (TS) and topoisomerase I (topo I) in untreated and treated cells were determined by immunoblotting. Changes in deoxynucleotide pools were examined by high-performance liquid chromatography. Results: Clonogenic assays revealed that colony formation was decreased by 50% after a 24-h exposure to 8 ± 2 nM SN-38 or 12 ± 3 μM 5FU, the latter being assayed in the presence of 2 μM FA. When treatment with 5FU/FA was followed by SN-38, the cytotoxicity was similar to that observed with 5FU/FA alone. In contrast, when HCT-8 cells were exposed to both agents simultaneously or to SN-38 followed by 5FU/FA, the cytotoxicity was greater than that of SN-38 or 5FU/FA treatment alone. Investigation of the mechanistic basis for this sequence dependence revealed that SN-38 treatment was associated with a dose- and time-dependent decrease in conversion of [5-3H]-2′-deoxyuridine to [3H]-H2O and thymidylate in intact cells. Immunoblotting failed to reveal any decrease in TS protein that could account for the decreased activity. High-performance liquid chromatography revealed that SN-38 treatment was associated with increased levels of the deoxynucleotide dTTP and decreased levels of dUTP. Flow microfluorimetry revealed that a 24-h treatment with 10 nM SN-38 resulted in accumulation of HCT-8 cells in late S and G2 phases of the cell cycle, with a further increase in the G2 fraction during the 24 h after SN-38 removal. Conclusions: These observations are consistent with a model in which SN-38 sequentially induces diminished DNA synthesis, elevated dTTP pools, inhibition of dUMP synthesis and enhanced toxicity of 5FU/FA. Accordingly, sequencing of irinotecan and 5FU/FA might be important in combining these agents into an effective treatment for colorectal cancer.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0843
    Keywords: Key words 5-Fluorouracil ; Interferon ; Colorectal cancer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Modulation of 5-fluorouracil (FUra) using leucovorin (LV) is a standard treatment approach in patients with metastatic colorectal cancer. Modulation of FUra with interferon alfa has also shown some promise. Laboratory data have demonstrated increased cytotoxicity when FUra is combined with both LV and interferon. The current study examined the effects of double modulation of FUra using LV and interferon.Patients with measurable advanced colorectal cancer received bolus FUra 375 mg/m2 plus LV 20 mg/m2 daily for 5 days, repeated every 28 days. Recombinant human interferon alfa-2a, 3 million IU/m2 subcutaneously, was given daily on the days of chemotherapy then three times weekly. There was one complete response and nine partial responses (10/41) seen for an overall response rate of 24% (95% CI 12.0–40.0%). Overall, 70% of patients experienced one or more episodes of nonhematologic toxicity of grade 3 or more. Weight loss was common, with a mean decrease of 2.9 kg over the first two months (P〈0.0001). Improvements in tumor-related symptoms were balanced by increased fatigue and a deterioration in body weight and performance status. There was no evidence of progressive changes in FUra metabolism from interferon usage.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Breast cancer research and treatment 40 (1996), S. 225-230 
    ISSN: 1573-7217
    Keywords: breast cancer ; male ; case series
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A review was conducted of 66 men with carcinoma of the breast seen at this institution between 1981 and 1992. The results of the study suggest that there are many similarities between breast cancer in men and women. The most common clinical presentation was a lump in the breast. The majority of tumors were T1 or T2, and infiltrating ductal carcinoma was the predominant histological type. Axillary nodal status and histological grade were predictive of survival. The pattern of recurrence and survival rates were similar to those seen in women. Some differences, however, were evident. Tumors were centrally located in the majority of patients and there was a high frequency of nipple involvement. The hormone receptor positivity rate was high and the median age at presentation was older. In comparison to a previous report of the same disease from this institution 10 years ago, fewer patients underwent radical surgical procedures and more patients received adjuvant systemic therapy. These approaches are justified since there are many biological similarities between breast cancer in men and women.
    Type of Medium: Electronic Resource
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