ATP-binding cassette sub-family B member 5 (ABCB5)

ATP-binding cassette sub-family B member 5 (ABCB5) is an integral membrane protein and a member of the ATP-binding cassette (ABC) transporter superfamily. ABCB5 functions as an ATP-dependent efflux transporter, exporting a variety of structurally diverse molecules—including drugs and xenobiotics—across cellular membranes. Its expression in cancer cells, particularly in melanoma and certain carcinomas, confers resistance to multiple chemotherapeutic agents via active drug efflux, contributing to the multidrug resistance phenotype[1][3][4][7]. ABCB5 is also expressed in normal stem cell populations (e.g., limbal stem cells of the cornea, melanocyte progenitors) and plays a functional role in maintaining cell fusion capabilities, stemness, and tissue homeostasis[3][6]. Overexpression of ABCB5 in tumors correlates with tumor progression, invasiveness, and worse prognoses, and its inhibition (e.g., by monoclonal antibodies or genetic knockdown) can reverse drug resistance and reduce tumorigenicity in preclinical models[3][7]. Safety concerns for therapeutic targeting include the risk of disabling endogenous protective transport in normal tissues and potential off-target toxicity, as ABC transporter family members share substrate overlaps[3][6].

Other names

ABCB5ATP-binding cassette subfamily B member 5ABCB5alphaABCB5betaEST422562P-glycoprotein ABCB5ATP-binding cassette protein

Drugs are effluxed out of cells by ABCB5 using ATP hydrolysis, leading to decreased intracellular drug accumulation and resistance to chemotherapy agents[3][4][7]. Antibodies targeting ABCB5 can block its transporter function and reduce tumor cell survival in models[3].