Effects of As₄S₄ and/or imatinib on various human leukemic cell lines and CD34⁺ cells from patients with CML and from nonleukemic donors. (A) Median-effect plot, dose-effect curve, and Fa-CI plot of K562 and primary CD34⁺ cells treated with imatinib and/or As₄S₄ for 48 hours. (B) IC₅₀ values in various human leukemic cell lines and CD34⁺ cells from patients with CML and nonleukemic donors treated with imatinib and/or As₄S₄ for 48 hours. K562, HL60, and U937, results from 3 separate experiments; CML-CP, results of CD34⁺ cells from 9 CP patients; CML-AP, results of CD34⁺ cells from 7 AP patients; CON, results of CD34⁺ cells from 4 nonleukemic donors. Data analysis was performed for the mutual nonexclusive assumption. The black broken line in the Fa-CI plots represents CI equal to 1. Fa values of 0.2, 0.4, or 0.6 correspond to 20%, 40%, or 60% growth inhibition. The concentration ratio of imatinib in combination with As₄S₄ was 1:10. Statistical analysis using a one-side paired t test. ^*, P < .01 versus primary nonleukemic cells; ▴, P < .01 versus HL60 or U937 cells.