In order to study whether or not the classical MDR mechanisms impede the cytotoxic activity of BetA toward cancer cells, we investigated multidrug-resistant P-glycoprotein (MDR1/ABCB1)-overexpressing CEM/ADR5000 cells and drug-sensitive parental CCRF-CEM cells using a resazurin assay. The gene discussed is ABCB1; the disease is cancer.