ABCG1 and ABCG2 are ATP-bindingcassette (ABC) transporter proteins responsible for pumping chemotherapeuticdrugs out of cancer cells, thereby contributing to chemotherapy resistance. ABCG2 reduces the concentration and efficacyof chemotherapeutic agents, such as mitoxantrone and doxorubicin,by scavenging them from the cell. The gene discussed is ABCG1; the disease is cancer.