MTT assays cannot be utilized to study the effects of STI571/Gleevec on the viability of solid tumor cell lines.
OBJECTIVE
This study will determine whether MTT assays accurately assess the effect of STI571 (Gleevec; Abl kinase inhibitor) on the viability of cancer cells containing highly active Abl kinases.


METHODS
Growth kinetics, tritiated thymidine, fluorescent caspase, MTT, and Cell Titer Glo (CTG) assays were used to determine the effect of STI571 on growth, proliferation, apoptosis, and viability of melanoma and breast cancer cells.


RESULTS
STI571 inhibited growth and proliferation, and increased apoptosis. However, MTT assays indicated that STI571 increased cell viability. In contrast, STI571 induced a dose-dependent decrease in viability using CTG assays.


CONCLUSIONS
Doses of STI571 (1-10 microM) required to inhibit endogenous Abl kinases interfere with the MTT assay, and therefore MTT cannot be used to determine the effect of STI571 on viability using these doses. Additionally, caution should be utilized when interpreting the results of MTT assays used to screen kinase inhibitors for anti-cancer activity, as drug effectiveness may be minimized.
Sims
Jonathan T
JT
Department of Molecular and Biomedical Pharmacology, University of Kentucky School of Medicine, Lexington, KY 40536, USA.
Plattner
Rina
R
D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D001549:Benzamides; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004354:Drug Screening Assays, Antitumor / Q000379:methods; D016044:Fusion Proteins, bcr-abl; D006801:Humans; D000068877:Imatinib Mesylate; D008545:Melanoma / Q000188:drug therapy* / Q000473:pathology; D010879:Piperazines / Q000008:administration & dosage / Q000494:pharmacology*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D011743:Pyrimidines / Q000008:administration & dosage / Q000494:pharmacology*; D013778:Tetrazolium Salts; D013844:Thiazoles
D000970:Antineoplastic Agents; D001549:Benzamides; D010879:Piperazines; D011743:Pyrimidines; D013778:Tetrazolium Salts; D013844:Thiazoles; D000068877:Imatinib Mesylate; D011505:Protein-Tyrosine Kinases; D016044:Fusion Proteins, bcr-abl; C022616:thiazolyl blue