Overexpression of the
multidrug resistance proteins P-glycoprotein (Pgp) and
breast cancer resistance
protein (BCRP) results in treatment failure of many
malignancies including
ovarian cancer. Dual inhibition of Pgp and BCRP may restore the sensitivity of resistant cells to anticancer drugs. We report the synthesis and characterization of a novel
anthranilic-acid based Pgp and BCRP modulator,
WK-X-34. In vitro inhibition of Pgp activity was evaluated using
99mTc-Sestamibi and
daunorubicin accumulation in Pgp overexpressing human
ovarian cancer cells (A2780/Adr) and its sensitive counterpart (A2780/wt). Interaction with BCRP was examined with a
mitoxantrone-efflux assay in BCRP-overexpressing MCF7/mx cells, with flow cytometry. Interactions with the
multidrug resistance associated proteins (MRP) were evaluated in transfected
MRP1, MRP2 and MRP3 cell lines, using a 5-CFDA efflux assay. In vivo
99mTc-Sestamibi imaging of human
ovarian cancer xenografts was used to evaluate the in vivo efficacy of
WK-X-34 in mice.
Daunorubicin accumulation in A2780/Adr cells was inhibited by
WK-X-34 at nanomolar concentrations (IC50: 82.1 +/- 6 nM).
WK-X-34 inhibited
mitoxantrone accumulation in BCRP-overexpressing cells at micromolar concentrations (IC50 = 26.5 +/- 4.6 microM), whereas
WK-X-34 did not significantly alter 5-CFDA accumulation in MRP transfected cells. In vivo, uptake of
99mTc-Sestamibi was significantly increased in A2780/Adr xenograft
tumors, brain and intestine (AUCs(0-4h) 136%, 147% and 138%; p < 0.05) in mice dosed with
WK-X-34 (20 mg/kg i.p.).
WK-X-34 selectively modulates Pgp and BCRP in vitro and in vivo in multidrug resistant
ovarian cancer cells, and thus may have potential utility in the treatment of multidrug resistant
tumors.