The aim of this study is to compare the effects of new fluorinated taxanes SB-T-12851, SB-T-12852, SB-T-12853, and SB-T-12854 with those of the classical taxane paclitaxel and novel non-fluorinated taxane SB-T-1216 on cancer cells. Paclitaxel-sensitive MDA-MB-435 and paclitaxel-resistant NCI/ADR-RES human cancer cell lines were used. Cell growth and survival evaluation, colorimetric assessment of caspases activities, flow cytometric analyses of the cell cycle and the assessment of mitochondrial membrane potential, reactive oxygen species (ROS) and the release of cytochrome c from mitochondria were employed. Fluorinated taxanes have similar effects on cell growth and survival. For MDA-MB-435 cells, the C(50) of SB-T-12851, SB-T-12852, SB-T-12853 and SB-T-12854 was 3 nM, 4 nM, 3 nM and 5 nM, respectively. For NCI/ADR-RES cells, the C(50) of SB-T-12851, SB-T-12852, SB-T-12853, and SB-T-12854 was 20 nM, 20 nM, 10 nM and 10 nM, respectively. Selected fluorinated taxanes, SB-T-12853 and SB-T-12854, at the death-inducing concentrations (30 nM for MDA-MB-435 and 300 nM for NCI/ADR-RES) were shown to activate significantly caspase-3, caspase-9, caspase-2 and also slightly caspase-8. Cell death was associated with significant accumulation of cells in the G(2)/M phase. Cytochrome c was not released from mitochondria and other mitochondrial functions were not significantly impaired. The new fluorinated taxanes appear to use the same or similar mechanisms of cell death induction as compared with SB-T-1216 and paclitaxel. New fluorinated and non-fluorinated taxanes are more effective against drug-resistant cancer cells than paclitaxel. Therefore, new generation of taxanes, either non-fluorinated or fluorinated, are excellent candidates for further and detailed studies.

• MeSH
• Cell Death drug effects   MeSH
• Cell Cycle drug effects   MeSH
• Drug Resistance, Neoplasm drug effects   MeSH
• Cytochromes c metabolism   MeSH
• DNA, Neoplasm metabolism   MeSH
• Caspases metabolism   MeSH
• Humans MeSH
• Mitochondria drug effects   metabolism   MeSH
• Cell Line, Tumor MeSH
• Paclitaxel chemistry   pharmacology   MeSH
• Cell Proliferation drug effects   MeSH
• Reactive Oxygen Species metabolism   MeSH
• Drug Screening Assays, Antitumor MeSH
• Fluorine Compounds chemistry   pharmacology   MeSH
• Taxoids chemistry   pharmacology   MeSH
• Cell Survival drug effects   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, N.I.H., Extramural MeSH
• Names of Substances
• Cytochromes c MeSH
• DNA, Neoplasm MeSH
• Caspases MeSH
• Paclitaxel MeSH
• Reactive Oxygen Species MeSH
• Fluorine Compounds MeSH
• Taxoids MeSH

BACKGROUND: In this study, the effect of novel taxane SB-T-1216 and paclitaxel on sensitive MDA-MB-435 and resistant NCI/ADR-RES human breast cancer cells was compared. MATERIALS AND METHODS: Cell growth and survival were evaluated after 96-hour incubation with tested concentrations of taxanes. The effect on the formation of microtubule bundles was assessed employing fluorescence microscopy and on the cell cycle employing flow cytometric analysis. The activity of caspases was assessed employing commercial colorimetric kits. RESULTS: The IC(50) (concentration resulting in 50% of living cells in comparison with the control) of SB-T-1216 in sensitive cells was 0.6 nM versus 1 nM for paclitaxel. However, the IC(50) of SB-T-1216 in resistant cells was 1.8 nM versus 300 nM for paclitaxel. Both SB-T-1216 and paclitaxel at death-inducing concentrations induced the formation of microtubule bundles in sensitive as well as resistant cells. Cell death induced in sensitive and resistant cells by paclitaxel was associated with the accumulation of cells in the G(2)/M phase. On the contrary, cell death induced by SB-T-1216 took place without the accumulation of cells in the G(2)/M phase but with a decreased number of G(1) cells and the accumulation of hypodiploid cells. Both SB-T-1216 and paclitaxel activated caspase-3, caspase-9, caspase-2 and caspase-8 in sensitive as well as resistant cells. CONCLUSION: Cell death induced by both paclitaxel and novel taxane SB-T-1216 in breast cancer cells is associated with caspase activation and with the formation of interphase microtubule bundles. Novel taxane SB-T-1216, but not paclitaxel, seems to be capable of inducing cell death without the accumulation of cells in the G(2)/M phase.

• MeSH
• Apoptosis drug effects   MeSH
• Cell Division drug effects   MeSH
• Drug Resistance, Neoplasm MeSH
• Doxorubicin pharmacology   MeSH
• Microscopy, Fluorescence MeSH
• Antineoplastic Agents, Phytogenic pharmacology   MeSH
• G1 Phase drug effects   MeSH
• G2 Phase drug effects   MeSH
• Caspase 2 metabolism   MeSH
• Caspase 3 metabolism   MeSH
• Caspase 8 metabolism   MeSH
• Caspase 9 metabolism   MeSH
• Humans MeSH
• Microtubules drug effects   MeSH
• Cell Line, Tumor MeSH
• Breast Neoplasms drug therapy   metabolism   pathology   MeSH
• Paclitaxel pharmacology   MeSH
• Cell Proliferation drug effects   MeSH
• Antibiotics, Antineoplastic pharmacology   MeSH
• Taxoids pharmacology   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, N.I.H., Extramural MeSH
• Comparative Study MeSH
• Names of Substances
• Doxorubicin MeSH
• Antineoplastic Agents, Phytogenic MeSH
• Caspase 2 MeSH
• Caspase 3 MeSH
• Caspase 8 MeSH
• Caspase 9 MeSH
• Paclitaxel MeSH
• Antibiotics, Antineoplastic MeSH
• Taxoids MeSH

We tested the effect of iron deprivation on cell death induction in human Raji cells pre-adapted to differing availability of extracellular iron. Iron deprivation was achieved by incubation in a defined iron-free medium. Original Raji cells have previously been adapted to long-term culture in a defined medium with 5 microg/ml of iron-saturated human transferrin as a source of iron. Raji/lowFe cells were derived from original Raji cells by subsequent adaptation to culture in the medium with 50 microm ferric citrate as a source of iron. Raji/lowFe-re cells were derived from Raji/lowFe cells by re-adaptation to the transferrin-containing (5 microg/ml) medium. Iron deprivation induced cell death in both Raji cells and Raji/lowFe-re cells; that is, cells pre-adapted to a near optimum source of extracellular iron (5 microg/ml of transferrin). However, Raji/lowFe cells preadapted to a limited source of extracellular iron (50 microm ferric citrate) became resistant to the induction of cell death by iron deprivation. We demonstrated that cell death induction by iron deprivation in Raji cells correlates with the activation of executioner caspase-3 and the cleavage of caspase-3 substrate, poly-ADP ribose polymerase. Two other executioner caspases, caspase-7 and caspase-6, were not activated. Taken together, we suggest that in human Raji cells, iron deprivation induces apoptotic cell death related to caspase-3 activation. However, the sensitivity of the cells to death induction by iron deprivation can be reversibly changed by extracellular iron availability. The cells pre-adapted to a limited source of extracellular iron became resistant.

• MeSH
• Enzyme Activation MeSH
• Apoptosis drug effects   physiology   MeSH
• Cell Division drug effects   physiology   MeSH
• Burkitt Lymphoma MeSH
• Iron Deficiencies * MeSH
• Caspase 3 metabolism   MeSH
• Caspase 6 metabolism   MeSH
• Caspase 7 metabolism   MeSH
• Culture Media MeSH
• Humans MeSH
• Cell Line, Tumor MeSH
• Cell Survival drug effects   physiology   MeSH
• Iron pharmacology   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• CASP6 protein, human MeSH Browser
• Caspase 3 MeSH
• Caspase 6 MeSH
• Caspase 7 MeSH
• Culture Media MeSH
• Iron MeSH

Iron deprivation induces apoptosis in some sensitive cultured tumour cells, while other cells are resistant. In order to elucidate the mechanisms involved in apoptosis induction by iron deprivation, we studied the expression of p53 and the expression of selected p53-regulated genes. To discriminate between changes coupled only with iron deprivation and changes involved in apoptosis induction by iron deprivation, we compared the expression of the genes in sensitive (human Raji, mouse 38C13) versus resistant (human HeLa, mouse EL4) cells under iron deprivation. Iron deprivation was achieved by incubation in a defined iron-free medium. The level of p53 mRNA decreased significantly under iron deprivation in sensitive cells, but it did not change in resistant cells. On the contrary, the level of the p53 protein under iron deprivation was slightly increased in sensitive cells while it was not changed in resistant cells. The activity of p53 was assessed by the expression of selected p53-regulated targets, i.e. p21(WAF1/CIP1) gene, mdm2, bcl-2 and bax. We did not detect any relevant change in mRNA levels as well as in protein levels of these genes under iron deprivation with the exception of p21(WAF1/CIP1). We detected a significant increase in the level of p21 mRNA in both (sensitive and resistant) mouse cell lines tested, however, we did not find any change in both (sensitive and resistant) human cell lines. Moreover, the p21(WAF1/CIP1) protein was accumulated in mouse-sensitive 38C13 cells under iron deprivation while all other cell lines tested, including human-sensitive cell line Raji, did not show any accumulation of p21(WAF1/CIP1) protein. It seems that the p21(WAF1/CIP1) mRNA, as well as protein accumulation, is not specifically coupled with apoptosis induction by iron deprivation and that it is rather cell-line specific. Taken together, we suggest that iron deprivation induces apoptosis at least in some cell types independently of the p53 pathway.

• MeSH
• Apoptosis * MeSH
• Humans MeSH
• Mice MeSH
• Tumor Cells, Cultured MeSH
• Tumor Suppressor Protein p53 physiology   MeSH
• bcl-2-Associated X Protein MeSH
• Proto-Oncogene Proteins c-bcl-2 genetics   MeSH
• Proto-Oncogene Proteins genetics   MeSH
• Gene Expression Regulation MeSH
• Iron physiology   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• BAX protein, human MeSH Browser
• Bax protein, mouse MeSH Browser
• Tumor Suppressor Protein p53 MeSH
• bcl-2-Associated X Protein MeSH
• Proto-Oncogene Proteins c-bcl-2 MeSH
• Proto-Oncogene Proteins MeSH
• Iron MeSH