To test this hypothesis, we investigated a synthetic, nontoxic taxane-based reversal agent (tRA), a compound initially developed as an inhibitor of multi-drug-resistant ABC transporter families in mammalian cancer cells, including P-glycoprotein (Pgp), MDR protein (MRP-1), and breast cancer resistance protein (BCRP) [19]. This evidence concerns the gene ABCG2 and cancer.