BCRP/CD338
BCRP (CD338), the breast cancer resistance protein encoded by ABCG2, is an ATP-binding cassette half-transporter that dimerizes to form an active xenobiotic efflux pump. Its substrates include chemotherapeutics such as mitoxantrone, topotecan, and methotrexate, and its overexpression in tumors confers multidrug resistance, the phenotype from which its name derives. BCRP is highly expressed at pharmacological barriers, including the blood-brain barrier, placenta, intestine, and liver canaliculi, shaping drug absorption and distribution, and it also exports uric acid, with gain-of-function variants predisposing to gout. The Hoechst side-population phenotype used to isolate stem and progenitor cells depends on BCRP, making CD338 a marker of stem-like cell compartments.
