Indanocine, a microtubule-binding indanone and a selective inducer of apoptosis in multidrug-resistant cancer cells.
BACKGROUND
Certain antimitotic drugs have antitumor activities that apparently result from interactions with nontubulin components involved in cell growth and/or apoptotic cell death. Indanocine is a synthetic indanone that has been identified by the National Cancer Institute's Developmental Therapeutics Program as having antiproliferative activity. In this study, we characterized the activity of this new antimitotic drug toward malignant cells.


METHODS
We tested antiproliferative activity with an MTT [i.e., 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay, mitochondrial damage and cell cycle perturbations with flow cytometry, caspase-3 activation with fluorometry, alterations of the cytoskeletal components with immunofluorescence, and antimicrotubule activity with a tubulin polymerization assay.


CONCLUSIONS
Indanocine is a cytostatic and cytotoxic indanone that blocks tubulin polymerization but, unlike other antimitotic agents, induces apoptotic cell death in stationary-phase multidrug-resistant cancer cells at concentrations that do not impair the viability of normal nonproliferating cells. Of the seven multidrug-resistant cell lines tested, three (i.e., MCF-7/ADR, MES-SA/DX5, and HL-60/ADR) were more sensitive to growth inhibition by indanocine than were their corresponding parental cells. Confluent multidrug-resistant cells (MCF-7/ADR), but not drug-sensitive cancer cells (MCF-7) or normal peripheral blood lymphocytes, underwent apoptotic cell death 8-24 hours after exposure to indanocine, as measured by sequential changes in mitochondrial membrane potential, caspase activity, and DNA fragmentation. Indanocine interacts with tubulin at the colchicine-binding site, potently inhibits tubulin polymerization in vitro, and disrupts the mitotic apparatus in dividing cells.


CONCLUSIONS
The sensitivity of stationary multidrug-resistant cancer cells to indanocine suggests that indanocine and related indanones be considered as lead compounds for the development of chemotherapeutic strategies for drug-resistant malignancies.
Leoni
L M
LM
Department of Medicine and The Sam and Rose Stein Institute for Research on Aging, University of California San Diego, La Jolla 92093, USA. lleoni@ucsd.edu
Hamel
E
E
Genini
D
D
Shih
H
H
Carrera
C J
CJ
Cottam
H B
HB
Carson
D A
DA
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3; D020169:Caspases / Q000187:drug effects; D004396:Coloring Agents; D053938:DNA Fragmentation; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D004789:Enzyme Activation / Q000187:drug effects; D004792:Enzyme Precursors / Q000187:drug effects; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D005470:Fluorometry; D006801:Humans; D007189:Indans / Q000494:pharmacology*; D008870:Microtubules / Q000187:drug effects* / Q000378:metabolism; D009369:Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D011108:Polymers; D011485:Protein Binding / Q000187:drug effects; D013778:Tetrazolium Salts; D013844:Thiazoles; D014404:Tubulin / Q000187:drug effects* / Q000378:metabolism; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D004396:Coloring Agents; D004792:Enzyme Precursors; D007189:Indans; D011108:Polymers; D013778:Tetrazolium Salts; D013844:Thiazoles; D014404:Tubulin; C404326:indanocine; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; C022616:thiazolyl blue