Cytotoxicity test of DMAQ-B1, compound 2 and D-410639 on CHO cells. CHO cells were treated with various concentrations of test compounds and their viability was measured with the use of MTT. LC50 for DMAQ-B1, compound 2, and D-410639 are 2.3 μM, 66.5 μM, and 295.9 μM, respectively. Error bars indicate standard error of the mean (SEM). See Materials and Methods for detail.