To understand the contribution, if any, of p-glycoprotein associated efflux on the anti-cancer activity of 4e, we examined the interaction of 4e with p-glycoprotein in Adriamycin resistant K562 cells (K562Adr500), previously shown to overexpress ABCB1 protein using rhodamine 6G dye (R6G), a florescent substrate of ABCB1. Here, ABCB1 is linked to cancer.