Reversal of Multidrug Resistance with a New Calcium/Calmodulin Antagonist

One of the major problems limiting optimal chemotherapy is the development of tumor cells with multidrug resistance (MDR) during treatment.These cells are cross-resistant to structurally different natural occurring drugs. One form of MDR is related to a reduction of drug accumulation in the resistant cells [7]. The drug efflux mechanism seems to be mediated by a 170 kDa plasma membrane glycoprotein which acts as an ATP-dependent drug efflux pump [4]. The MDR1 gene encodes for this protein, termed P-glycoprotein [2, 3].