ABCB1 and neoplasm: All tumours studied expressed both MDR-1 P-gp and MRP-1; intensity levels of these transporters did not vary to any great degree, however a higher proportion (76%) of MDR-1 positive tumours exhibited positive staining in 50% or more of tumour cells compared to MRP-1 staining patterns where 61% of MRP-1 positive tumours exhibited staining in 50% or more of tumour cells.