Differential camptothecin-induced apoptosis in HTLV-1 immortalized cell lines. A) ACH.1 and ACH.30.1 cell lines were exposed to various apoptosis inducing agents and assayed for percentage of cells induced into apoptosis via Annexin V flow cytometry. Data represents the results of at least three independent experiments. Jurkat T-cells were used as a positive control. Representative result of Annexin V flow cytometry following apoptosis induction with camptothecin. Apoptotic fraction is seen in the lower right quadrant by FACS analysis. B) Following treatment with camptothecin, a greater percentage of ACH.30.1 cells were induced into apoptosis compared to ACH.1 cells (nonparametric Wilcoxon rank sum test, p-value 0.03). ACH.30.1 cells and ACH.1 cells were induced into apoptosis to an equal degree following treatment with etoposide (nonparametric Wilcoxon rank sum test, p-value 0.25). Neither ACH.1 nor ACH.30.1 cells were induced into apoptosis following treatment with TRAIL (nonparametric Wilcoxon rank sum test, p-value 0.59 and 0.41, respectively). C) As a positive control, apoptosis was induced in Jurkat T-cells with all apoptosis inducing agents. * Statistically significant apoptosis induction; ** Statistically more apoptosis induction in ACH.30.1 cells compared to ACH.1 cells following treatment with camptothecin. Standard error bars are indicated.