Additionally, the upregulation of ATP‐binding cassette (ABC) transporters, including multidrug resistance protein 1 (MDR1), multidrug resistance‐associated protein 1 (MRP1), and breast cancer‐resistant protein (BCRP), in drug‐resistant cancer cells, analogous to their role in placental development, may facilitate chemotherapy efflux, further resulting in treatment resistance. This evidence concerns the gene ABCG2 and cancer.