Induction of apoptosis in MCF‐7 and NCI/ADR‐RES cells by triazole‐containing estradiol analogs

Abstract

A series of triazole‐containing estradiol analogs (A‐D) was designed and synthesized in an attempt to generate compounds with increased D‐ring bulk. We hypothesized that these compounds would function as estrogen receptor (ER) antagonists and reduce proliferation of ER dependent cells. These compounds possessing varying degrees of lipophilicity and sterics were screened for anti‐proliferative activity in ER‐positive MCF‐7 cells and ER‐negative NCI/ADR‐RES cells. Visual examination of cells following increasing concentrations of C and D revealed gross morphology suggestive of apoptosis, whereas A and B elicited no apparent effects. Treatment with 50 μM of C and D reduced cell number by 41% and 58% respectively compared to control in MCF‐7 cells. Interestingly, NCI/ADR‐RES cell number was reduced by 61% and 69% with 50 μM of C and D respectively, suggesting that C and D function in an ER independent mechanism. Western blotting analysis demonstrated that C and D increased expression of cleaved caspases‐3 and ‐7 in NCI/ADR‐RES cells and cleaved caspase‐7 in MCF‐7 cells. C and D also increased expression of cleaved caspase‐9, but not caspase‐8, demonstrating induction of an intrinsic apoptotic pathway. These results suggest structural modifications affording increased bulk and lipophilicity to the D‐ring of estradiol generate compounds that function to induce intrinsic apoptosis in an ER independent mechanism.