ABCG2 and neoplasm: P‐glycoprotein is the most studied and important ABC transporter and it was considered responsible for the efflux of chemotherapeutic agents from many cancer cells leading to their drug insensitivity.[7, 8] Recent studies have also shown that P‐gp overexpression was associated with a more aggressive tumour phenotype promoting tumour invasion and metastasis.[9] MRP1 and BCRP were also associated with reduced tumour responses to cytotoxic drugs.