The Anti-tumor Effects of Androstene Steroids Exhibit a Strict Structure-Activity Relationship Dependent upon the Orientation of the Hydroxyl Group on Carbon-17

Androstene steroids are metabolites of dehydroepiandrosterone and exist as androstene-diols or -triols in alpha- and beta-epimeric forms based upon the placement of the hydroxyl groups relative to the plane of the Delta 5cycloperhydrophenanthrene ring. 5-Androstene-3 beta,17 beta-diol (3 beta,17 beta-AED) functions to upregulate immunity and the addition of a third hydroxyl group at C-7 in the alpha- or beta-orientation (3 beta,7 alpha,17 beta-AET and 3 beta,7 beta,17 beta-AET, respectively) enhances the immunological activity of the molecule. In contrast, 5-androstene-3 beta,17 alpha-diol (3 beta,17 alpha-AED) possesses potent anti-tumor activity. We synthesized a new androstene by adding a third hydroxyl group at C-7 to make 5-androstene-3 beta,7 alpha,17 alpha-triol (3 beta,7 alpha,17 alpha-AET) and compared the anti-tumor activity of this steroid to the four existing androstenes. The results showed that this modification reduced the activity of 3 beta,17 alpha-AED. The ranking of the anti-tumor activities of these steroids and their IC50 on human glioblastoma and lymphoma cells was: 3 beta,17 alpha-AED (similar to 10 mu m) > 3 beta,7 alpha,17 alpha-AET (similar to 30 mu m) >> 3 beta,7 alpha,17 beta-AET (similar to 150 mu m)> 3 beta,7 beta,17 beta-AET (not achievable) >= 3 beta,17 beta-AED (not achievable). 3 beta,17 alpha-AED and 3 beta,7 alpha,17 alpha-AET induced autophagy in T98G glioblastoma cells and apoptosis in U937 lymphoma cells. These results indicate that the position of the hydroxyl group on C-17 dictates the anti-tumor activity of the androstenes and must be in the alpha-configuration, demonstrating a strict structure-activity relationship.