MRPs contribute to cancer drug resistance by actively transporting chemotherapy drugs out of cancer cells, reducing the intracellular concentration of these drugs, and thereby diminishing their cytotoxic effects. This efflux mechanism is a crucial factor in the failure of chemotherapy treatments. For example, MRP1 (ABCC1) and MRP2 (ABCC2) are often overexpressed in various cancers, including breast cancer, lung cancer, and leukemia, leading to resistance against drugs like doxorubicin, vincristine, and methotrexate.
