New medium oxacyclic O,N-acetals and related open analogues: biological activities.

Attention is increasingly being focussed on the cell cycle and apoptosis as potential targets for therapeutic intervention in cancer. Taking 1-[(2-oxepanyl)]-5-fluorouracil previously prepared by us, we committed ourselves to increase the lipophilicity of this upper cyclohomologue of Ftorafur and prepared a series of bioisosteric benzannelated seven-membered 5-FU O,N-acetals to test them against the MCF-7 human breast cancer cell line. Benzo-fused seven-membered O,O-acetals or their acyclic analogues led to the expected 5-FU O,N-acetals (or aminals), in addition to six- and to 14-membered aminal structures and acyclic compounds. All the cyclic aminals provoked a G(o)/G(1)-phase cell cycle arrest, whereas Ftorafur, a known prodrug of 5-FU, and 1-[2-(2-hydroxymethyl-4-nitrophenoxy)-1-methoxyethyl]-5-fluorouracil (51) induced an S-phase cell cycle arrest. Although breast cancer is most often treated with conventional cytotoxic agents it has proved difficult to induce apoptosis in breast cancer cells and, consequently, improved clinical responses may be obtained by identifying therapies that are particularly effective in activating apoptosis. 1-(2,3-Dihydrobenzoxepin-2-yl)-5-fluorouracil (26) may be particularly useful in stimulating apoptosis in breast cancer. This compound is more potent as an apoptotic inductor than paclitaxel (Taxol). Finally, a fact that is worth emphasizing is that the cyclic and acyclic 5-FU O,N-acetals induce neither toxicity nor death in mice after one month's treatment when administered intravenously twice a week, with a 50 mg/kg dose each time. Taken together, the experimental findings provide evidence of specific anti-tumour activity of these new substances and warrant further evaluation in in vivo models of breast cancer to future clinical applications.

Growth inhibition, G(1)-arrest, and apoptosis in MCF-7 human breast cancer cells by novel highly lipophilic 5-fluorouracil derivatives.

In this study we evaluate the antitumour activity, the cell cycle arrest and apoptotic properties of novel lipophilic benzene-fused seven-membered 5-fluorouracil (5-FU) analogs in comparison to 5-FU on MCF-7 human breast cancer cells. The lipophilicities of ESB-786B, ESB-252A and ESB-928A were predicted by using the CDR option of the PALLAS 2.0 program. Cytotoxic assays were evaluated in MCF-7 cells treated with the sulforhodamine B colorimetric method. Cell cycle perturbations were studied by flow cytometry. Apoptosis was determined by both DNA fragmentation and annexin V-FITC and propidium iodide staining. The novel derivatives were more lipophilic than 5-FU and induced a marked growth inhibition, in a dose-dependent manner. After treatment with IC(50) value (ranged from 2.5 to 22 microM) for each compound, light microscopy observation showed modifications in the morphology of MCF-7 cells. In addition, the 5-FU analogs arrest cells in the G(0)/G(1) phase of the cell cycle whereas 5-FU induced arrest in S-phase. Moreover, induction of apoptosis was demonstrated by the annexin-V-based assay and confirmed using DNA fragmentation analysis on MCF-7 cells, a cell line in which the induction of DNA laddering is very difficult. The novel benzannelated seven-membered 5-FU analogs can be considered as specific apoptotic inducers. These experimental findings provide support for the use of these novel compounds as new weapons in the fight against breast cancer.