CA4P blocks leukemic cell growth, and induces G₂/M arrest, cell death with morphologic evidence of mitotic catastrophe and DNA fragmentation. (A) CA4P inhibits leukemic cell proliferation and causes cell death. A panel of leukemic cells was incubated with CA4P at the different concentrations indicated, and viable cells were counted after 48 hours using trypan blue exclusion. Results of 4 experiments in duplicate are expressed as the ratio of the percentage of viable cells/control plus or minus SEM (*P < .05 compared with CA4P-untreated cells; n = 4). (B) CA4P induces G₂/M arrest and cell death (increase in sub-G₀/G₁ peak). KG1a leukemic cells were treated with CA4P at 0-, 5-, and 10-nM concentrations for 48 hours, and cell-cycle analysis was performed by PI staining and flow cytometry. (C) CA4P induces DNA fragmentation. CA4P-induced DNA damage was assessed by the comet assay. Results of 3 experiments in duplicate are expressed as the mean of the number of cells with a comet tail (percentage) plus or minus SEM (*P < .05 compared with CA4P-untreated cells; n = 3).