MULTIDRUG-RESISTANCE PHENOTYPE - A POTENTIAL MARKER OF CHEMOTHERAPY RESISTANCE IN BREAST-CANCER

Laboratory markers help medical oncologists predict chemotherapy resis tance. The multidrug resistance gene (MDR1) and its P-glycoprotein pro duct (MDR1) bold the promise of being such a marker. The only studies that have correlated the expression of MDR with clinical response to c hemotherapy have used immunohistochemical reactions on tissue sections with monoclonal antibodies to MDR1. We have conducted such a study wi th a polyclonal antibody. The presence of MDR1 in our study did not de fine a population of chemotherapy-resistant patients. Correlative labo ratory and clinical studies need to be performed to define the role of MDR in human breast cancer.