Multidrug resistance (MDR) is a phenomenon where
cancer cells become simultaneously resistant to anticancer drugs with different structures and mechanisms of action. MDR has been shown to be associated with overexpression of
ATP-binding cassette (
ABC) transporters. Here, we report that
telatinib, a small molecule
tyrosine kinase inhibitor, enhances the anticancer activity of ABCG2 substrate anticancer drugs by inhibiting ABCG2 efflux transporter activity. Co-incubation of ABCG2-overexpressing
drug resistant cell lines with
telatinib and ABCG2 substrate anticancer drugs significantly reduced cellular viability, whereas
telatinib alone did not significantly affect
drug sensitive and
drug resistant cell lines.
Telatinib at 1 μM did not significantly alter the expression of ABCG2 in ABCG2-overexpressing cell lines.
Telatinib at 1 μM significantly enhanced the intracellular accumulation of [(3)H]-
mitoxantrone (MX) in ABCG2-overexpressing cell lines. In addition,
telatinib at 1 μM significantly reduced the rate of [(3)H]-MX efflux from ABCG2-overexpressing cells. Furthermore,
telatinib significantly inhibited ABCG2-mediated transport of [(3)H]-E₂17βG in ABCG2 overexpressing membrane vesicles.
Telatinib stimulated the
ATPase activity of ABCG2 in a concentration-dependent manner, indicating that
telatinib might be a substrate of ABCG2. Binding interactions of
telatinib were found to be in transmembrane region of homology modeled human ABCG2. In addition,
telatinib (15 mg/kg) with
doxorubicin (1.8 mg/kg) significantly decreased the growth rate and
tumor size of ABCG2 overexpressing
tumors in a xenograft nude mouse model. These results, provided that they can be translated to humans, suggesting that
telatinib, in combination with specific ABCG2 substrate drugs may be useful in treating
tumors that overexpress ABCG2.