Decreased P-gp expression correlates with an accumulation of the P-gp substrate Rhodamine 123 (Rh123) and promotes the sensitivity of the human T lymphoblastoid leukemia cell line (CEM/VLB(100)) and a mouse fibroblast MDR1 transfected cell line (77.1) towards the P-gp substrate, vinblastine [90]. Here, PGP is linked to leukemia.