TAXOL INHIBITS OPIOID BINDING ON T47D HUMAN BREAST-CANCER CELLS

In the T47D human breast cancer cell line, Taxol was found to compete for ethylketocyclazocine opioid binding (IC50 3.3 pM). In contrast, no interaction of the drug with [H-3]diprenorphine binding occurred. Bin ding was multiphasic, in the absence of colchicine (10(-6) M), but mon ophasic in its presence, indicating an involvement of the cytoskeleton in this process. Alignment of Taxol binding domains on alpha and beta tubulin with the kappa opioid site revealed homology of these sites w ith the first extracellular loop of the receptor. These results indica te a possible new action of Taxol, indicating for the first time a mem brane action of the agent. (C) 1997 Academic Press.