Impaired breast cancer resistance protein mediated drug transport in plasma cells in multiple myeloma.

The breast cancer resistance protein (BCRP/ABCG2) is an ATP-binding-cassette transporter involved in the transport of drugs used in the treatment of multiple myeloma (MM). Its expression, function and clinical significance in MM, however, are unknown. We report that BCRP is preferentially expressed and functionally active in normal plasma cells but that its function is significantly impaired in plasma cells in newly diagnosed MM. The data presented argue against a role for BCRP in primary drug resistance in MM and the utilisation as a molecular target as such but warrant research into its (patho)physiological role in normal and malignant plasma cells.