P-glycoprotein (P-gp), also known as ABCB1, is a membrane-associated protein that functions as an ATP-dependent drug efflux pump. This protein is part of the ATP-binding cassette (ABC) transporter family and plays a crucial role in the transport of various substances across cellular membranes. In the context of cancer, P-gp is particularly noteworthy for its role in multidrug resistance (MDR).