On the function of hormone receptors in the action of steroidal alkylating agents.

Steroidal alkylating agents are supposed to bind to steroid hormone receptors in target tissues. By this interaction the steroid portion might act as a carrier for the alkylating group. Three steroidal agents (phenesterin, estradiol mustard, dehydroepiandrosterone mustard) were tested for their capacity to combine with estrogen and androgen receptors in normal and malignant target tissues. For measuring steroid receptor complexes ager gel electrophoresis was used. All three compounds (added at a 10(3)-fold excess) revealed in vitro no competition to receptor sites (estrogen and androgen binding). After preincubation of intact tissue estrogen mustard was effective in inhibiting the binding of 3H-estradiol and dehydroepiandrosterone mustard reduced the uptake of 3H-5alpha-DHT. This may be due to liberating of estradiol and dehydroepiandrosterone, respectively, from the intact molecule. From these data it is unlikely that the cytostatic steroidal agents are more effective than other alkylating drugs.