PGP and plasma cell myeloma: Overexpression of BCRP and P-gp has been related to reduced clinical response and MDR in chronic lymphocytic leukemia, multiple myeloma, ALL, metastatic breast cancer, and AML.5 Furthermore, P-gp was found to have an important role in MDR in malignancy cells, facilitating intracellular chemotherapeutic drug efflux and suppressing tumor necrosis factor (TNF).