Lucena cells cross-resistance to IM is due Pgp efflux. Apoptotic cells (A), cell cycle (B) and Rho 123 (C-D) were measured by flow cytometry after 3 different treatments conditions: 1 μM IM, 50 μM VP and co-treatment with 1 μM IM and 50 μM VP. (D) Representative histograms of Rho 123 extrusion under conditions described above. (1): K562 ctrl and IM treatment; (2): Lucena ctrl and (3) Lucena under: IM, VP and IM + VP treatments. K562 cells were used as positive control for Rho 123 retention, and K562 treated with 1 μM IM was used as positive control for apoptosis induction and cell cycle arrest. Values represent the means of three independent determinations ± s.d. (*p < 0.05; **p < 0.01). AF = auto fluorescence; K5 = K562; LU = Lucena.