desoxyepothilone-b and Leukemia-Lymphoma--Adult-T-Cell

Epothilones, like paclitaxel, bind to beta-tubulin and stabilize microtubules. We selected a series of four leukemia sublines that display increasing levels of resistance to the epothilone analog desoxyepothilone B (dEpoB). The dEpoB cells selected in 30-140 nM were approximately 15-fold cross-resistant to paclitaxel, while 300 nM selected cells were 467-fold resistant to this agent. The dEpoB-selected cells are hypersensitive to microtubule destabilizing agents, and express increased levels of class III beta-tubulin and MAP4. A novel class I beta-tubulin mutation, A231T, that affects microtubule stability but does not alter paclitaxel binding, was identified. The 300 nM selected cells acquired a second mutation, Q292E, situated near the M loop of class I beta-tubulin. These cells fail to undergo drug-induced tubulin polymerization due to dramatically reduced drug binding. The dEpoB-resistant leukemia cells provide novel insights into microtubule dynamics and, in particular, drug-target interactions.

Topics: Antineoplastic Agents; Binding Sites; Cell Division; Cell Line, Tumor; Chemokines, CC; Drug Delivery Systems; Drug Resistance, Neoplasm; Electrophoresis, Polyacrylamide Gel; Epothilones; Humans; Leukemia-Lymphoma, Adult T-Cell; Microtubule-Associated Proteins; Microtubules; Models, Molecular; Mutation; Paclitaxel; Spectrometry, Mass, Electrospray Ionization; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Tubulin

The epothilones are naturally occurring, cytotoxic macrolides that function through a paclitaxel (Taxol)-like mechanism. Although structurally dissimilar, both classes of molecules lead to the arrest of cell division and eventual cell death by stabilizing cellular microtubule assemblies. The epothilones differ in their ability to retain activity against multidrug-resistant (MDR) cell lines and tumors where paclitaxel fails. In the current account, we focus on the relationship between epothilone and paclitaxel in the context of tumors with multiple drug resistance. The epothilone analogue Z-12,13-desoxyepothilone B (dEpoB) is >35,000-fold more potent than paclitaxel in inhibiting cell growth in the MDR DC-3F/ADX cell line. Various formulations, routes, and schedules of i.v. administration of dEpoB have been tested in nude mice. Slow infusion with a Cremophor-ethanol vehicle proved to be the most beneficial in increasing efficacy and decreasing toxicity. Although dEpoB performed similarly to paclitaxel in sensitive tumors xenografts (MX-1 human mammary and HT-29 colon tumor), its effects were clearly superior against MDR tumors. When dEpoB was administered to nude mice bearing our MDR human lymphoblastic T cell leukemia (CCRF-CEM/paclitaxel), dEpoB demonstrated a full curative effect. For human mammary adenocarcinoma MCF-7/Adr cells refractory to paclitaxel, dEpoB reduced the established tumors, markedly suppressed tumor growth, and surpassed other commonly used chemotherapy drugs such as adriamycin, vinblastine, and etoposide in beneficial effects.

Topics: Animals; Antineoplastic Agents; Breast Neoplasms; Cell Survival; Drug Resistance, Neoplasm; Epothilones; Female; Humans; Lactones; Leukemia P388; Leukemia-Lymphoma, Adult T-Cell; Mice; Mice, Nude; Ovarian Neoplasms; Paclitaxel; Structure-Activity Relationship; Thiazoles; Transplantation, Heterologous; Tumor Cells, Cultured