Apoptotic Pathways of Epothilone BMS 310705

Objective. BMS 310705 is a novel water-soluble analog of epothilone B currently in phase I clinical evaluation in the treatment of malignancies such as ovarian, renal, bladder, and lung carcinoma. Using an early passage cell culture model derived from the ascites of a patient clinically refractory to platinum/paclitaxel therapy, we evaluated the pathway of caspase-mediated apoptosis.Methods. Cells were treated for I h and subsequently evaluated for apoptosis, survival, and caspase activity. Apoptosis was determined by fluorescent microscopy. Caspase-3, -8, and -9 activities were determined by fluorometry using target tetrapeptide substrates. Mitochondrial release of cytochrome c was determined by immunoblot analysis.Results. After treatment with BMS 310705, apoptosis was confirmed in >25% of cells at 24 h. Survival was significantly lower (P < 0.02) in cells treated with 0.05 muM BMS 310705 vs paclitaxel. Analysis revealed an increase of caspase-9 and -3 activity; no caspase -8 activity was observed. Release of cytochrome c was detected at 12 h following treatment. SN-38 and topotecan failed to induce apoptosis.Conclusions. BMS 310705 induces significant apoptosis, decreases survival, and utilizes the mitochondrial-mediated pathway for apoptosis in this model. (C) 2003 Elsevier Inc. All rights reserved.