Variants in ABC transporter genes, including ABCB1, ABCC4, and ABCC3, as well as solute carrier (SLC) genes such as SLC28A3, are known to influence the pharmacokinetics of numerous anti-cancer agents, including fluoropyrimidines, methotrexate, anthracyclines, and irinotecan. The gene discussed is SLC28A3; the disease is cancer.