They are involved in the exportation of endogenous substances, e.g., metabolites, vitamins and lipids, in addition to exogenous products such as toxins and drugs [18] Part of these transporters play a key role in acquiring multidrug resistance (MDR) characteristics to cancer chemotherapies, such as ABCB1, ABCC1, and ABCG2 [17]. The gene discussed is ABCG2; the disease is cancer.