ABCB1 and renal cell carcinoma: In renal cell carcinoma (RCC) and colon cancer cell lines exhibiting MDR and augmented ABCB1 expression, we have identified PITX2 as a contributor to chemotherapeutic drug resistance through transcriptional upregulation of ABCB1[42] as well as ABCC1, ABCG2, and the drug uptake transporter, SLC22A3[43].