PGP and leukemia: In a previous study [27], we showed that 3β-acetyl tormentic acid (3ATA, Figure 1), a triterpene isolated from Cecropia lyratiloba, is able to induce apoptosis in an MDR leukemia cell line overexpressing P-gp/ABCB1 without interfering with P-gp/ABCB1 expression or activity.