Multidrug resistance in the chronic lymphoproliferative disorders

Multidrug resistance (MDR) is a phenomenon in malignancy whereby tumor cells generate mechanisms to resist cytotoxic treatments. Several such mechanisms have been identified. However, to date the most significant research on MDR has involved the adenosine triphosphate binding cassette (ABC) transporter proteins, including P-glycoprotein (P-gp) and multidrug resistance associated protein (MRP). These proteins have natural functions involving substrate transport in normal cells but are detrimental to treatment when expressed in the membrane of tumor cells. It remains unclear whether ABC mediated MDR functions primarily through protein up-regulation or via a relevant signaling mechanism, or is simply due to selective pressure on an already resistant tumor cell subpopulation. Here we present an overview of MDR in the chronic lymphoproliferative disorders (CLPDs), in particular that attributed to the ABC transporter protein family.