ABCB1 and cancer: These results suggest that uPA and CD44 may functionally regulate MDR1 or MRP2 expression and confer drug resistance to ovarian cells during cancer progression, further confirming the close link between invasive and metastatic markers (uPA and CD44) with MDR proteins (MDR1 and MRP2), and may have clinical significance for future therapy to target late-stage and drug-resistance ovarian cancer cells.