Comparison of growth inhibitory activities of apogossypol and gossypol using NCI 60 tumor cell line panel. Tumor cell lines were cultured for 48 hours with various concentrations of apogossypol or gossypol, and relative cell number was determined by a protein staining method, calculating the concentration required to inhibit growth by 50% (GI₅₀) (A) and to reduce cells by 50% (LD50) (B). The thick line represents the best-fit line, using Spearmen correlation analysis, while thin lines represent 95% confidence intervals. The axis breaks in panel B indicate cell lines (gray circles) where LD50 is more than 100 μM. Spearman correlation analysis for panel B excluded the LD50 data.