S. Batra et I. Larsson, BINDING OF VINBLASTINE AND ESTRAMUSTINE TO ISOLATED PLASMA-MEMBRANE FRACTIONS FROM HUMAN PROSTATE AND PROSTATIC TUMORS, Cancer letters, 106(2), 1996, pp. 217-220
The binding of vinblastine (VLB) and estramustine (EM) to plasma membr
anes isolated from human prostate, prostatic tumors as well as from Du
nning rat prostatic AT-I tumors was studied. In addition, the uptake o
f these drugs in AT-1 tumor cells in culture was examined. Binding of
VLB was six-fold lower than that of EM in membrane preparations from a
ll three sources. The uptake of VLB in the intact AT-1 cells was nearl
y five-fold lower than that of EM. At concentrations comparable to tho
se achieved clinically the binding of EM was 100-fold higher than that
of VLB. The data suggest that, owing to a very high membrane concentr
ation of EM relative to that of VLB, the active efflux VLB in drug res
istant cells would be impeded. This in turn would lead to a higher acc
umulation of VLB in cells that actively transport cytotoxic drugs.