ATP-based cell viability assay is superior to trypan blue exclusion and XTT assay in measuring cytotoxicity of anticancer drugs Taxol and Imatinib, and proteasome inhibitor MG-132 on human hepatoma cell line HepG2

BACKGROUND: Drug-induced liver injury (DILI) is the most common reason for withdrawal of anticancer drugs from the market. To prevent adverse side effects of drugs, it is important to investigate potential toxicity in vitro. However, outcome of cytotoxicity screenings can differ remarkably depending on the method used. OBJECTIVE: We aimed to compare XTT, ATP-based CellTiter-Glo (R) 2.0 and trypan blue exclusion (TBE) assays regarding their sensitivity in detecting acute cytotoxicity on HepG2 cells after incubation with the classical anticancer drugs Taxol and Imatinib or with the proteasome inhibitor MG-132. METHODS: HepG2 cells were treated for 48 h and cell viability was analysed by XTT, CellTiter-Glo (R) 2.0 or TBE assay. RESULTS: All tested compounds showed a reduction of viability of HepG2 cells. However, assay results differed significantly: Both ATP-based and TBE assay showed concentration-dependent cytotoxic effects, but outcomes were less pronounced with TBE. In contrast, the widely used XTT assay did not detect any acute cytotoxicity of Taxol and Imatinib. CONCLUSIONS: Acute cytotoxic effects of tested compounds could be revealed. However, results were significantly different from each other with ATP assay being the most sensitive one under the conditions tested. Thus, acute cytotoxicity can be dramatically underestimated if only standard XTT test is used.