Mechanism of action of ixabepilone and its interactions with the βIII-tubulin isotype

Abstract

Ixabepilone (Ixempra, BMS-247550), a semisynthetic analog of epothilone B, is a microtubule-targeted drug in clinical use for treatment of metastatic or locally advanced breast cancer. Ixabepilone's binding and mechanism of action on microtubules and their dynamics, as well as its interactions with isotypically altered microtubules, both in vitro and in tumor cells, have not been described. Microtubules are dynamic polymers of the protein tubulin that function in mitosis, intracellular transport, cell proliferation, and migration. They continually undergo dynamic instability, periods of slow growth and rapid shortening that are crucial to these cell functions. We determined ixabepilone's microtubule binding and polymerization effects in vitro and also determined its effects on inhibition of dynamic instability in vitro and in cells, both with and without removal of the βIII isotype of tubulin. The βIII isotype of tubulin is associated with drug resistance and tumor aggressivity. We found that removal (in vitro) and knockdown (in cells) of βIII-tubulin led to increased inhibition of microtubule dynamic instability by ixabepilone. Depletion of βIII-tubulin from MCF7 human breast cancer cells also induced increased mitotic arrest by ixabepilone. Thus, βIII-tubulin expression suppresses the antitumor effects of ixabepilone, indicating that increased βIII-tubulin may be an important contributor to the development of resistance to ixabepilone.

Safranal Inhibits HeLa Cell Viability by Perturbing the Reassembly Potential of Microtubules

“…Human cervical cancer cells (HeLa) were cultured in Dulbecco's Modified Eagle's Medium with 10% ( v / v ) fetal bovine serum and penicillin (100 U/mL)/streptomycin (0.1 mg/mL) (Himedia, Mumbai, India) at 37°C and 5% CO 2 . Effect of safranal (0–200 μM) on HeLa cell viability after 48 h of exposure was determined by using a sulforhodamine B (SRB) assay, as described by Lopus et al, .…”

“…Human cervical cancer cells (HeLa) were cultured in Dulbecco's Modified Eagle's Medium with 10% (v/v) fetal bovine serum and penicillin (100 U/mL)/streptomycin (0.1 mg/ mL) (Himedia, Mumbai, India) at 37°C and 5% CO 2 . Effect of safranal (0-200 μM) on HeLa cell viability after 48 h of exposure was determined by using a sulforhodamine B (SRB) assay, as described by Lopus et al, 2015. Visualization of microtubules and tubulin acetylation. For immunofluorescence imaging, the cells, grown on surface-treated coverslips, were treated with safranal (100 μM or 200 μM) for 24 h. Afterwards, they were washed with 1× phosphate-buffered saline, fixed with 4% formaldehyde, and permeabilized with chilled methanol.…”

Chemotherapy reaction induced by ixabepilone, a microtubule stabilizing agent, mimicking extramammary Paget's disease in a patient with breast carcinoma

“…In this report, we present the histopathologic features of a chemotherapy reaction secondary to ixabepilone, a microtubule stabilizer, approved for the treatment of metastatic and locally advanced treatment‐resistant breast cancer . We emphasize the importance of considering a chemotherapy reaction in the histologic differential when evaluating a skin biopsy from a cancer patient receiving chemotherapy.…”

Structural Basis for Induction of Peripheral Neuropathy by Microtubule-Targeting Cancer Drugs

“…Paclitaxel binds along the length of the microtubule, as does ixabepilone (32)(33)(34)(35). Although paclitaxel ultimately resides on the inside surface of the microtubule, it significantly alters the overall conformation of the tubulin to which it is bound, enhancing pi-pi interactions, increasing hydrogen bonds, stiffening the protofilaments, and even affecting the conformation of a-tubulin and changing the number of protofilaments in the microtubule from 13 to 12 (6).…”