Compound 5a ([Z]-1, 1-Dichloro-2,3
diphenyl-2-(4-methoxyphenyl)
cyclopropane) is a novel cyclopropyl compound which was shown to be a pure
antiestrogen. In the present study, the antiproliferative activity of 5a was examined on
estrogen receptor (ER)-positive MCF-7 and ER-negative MDA-MB-231 human
breast cancer cells and A-549 human
lung cancer cells using the hemocytometric
trypan blue exclusion method. Compound 5a inhibited the growth of MCF-7 cells in a dose-related manner over a concentration range of 10(-9) to 10(-5) M, but did not alter the growth of MDA-MB-231 or A-549 cells.
Co-administration of
estradiol (10(-8) M) reversed the antiproliferative activity of 5a (10(-7) M) on MCF-7 cells. Further, an ER-dependent mechanism of action is supported by the specific ER binding of 5a in MCF-7 cells observed in this study. The influence of 5a on the cell surface morphology of MCF-7 and MDA-MB-231 cells was studied using scanning electron microscopy (SEM). Compound 5a
at 10(-6) M reduced the length and density of microvilli (MV) on MCF-7 cells, which was reversed by
co-administration of
estradiol (10(-8) M). This compound did not alter the cell surface morphology of ER-negative MDA-MB-231 cells. In conclusion, 5a and
tamoxifen inhibited the growth of ER-prositive MCF-7 cells in an
estradiol-reversible manner, and had no effect on ER-negative MDA-MB-231 cells. The results of this study with human
breast cancer cells suggest that 5a may be highly effective in the treatment of
estrogen-dependent
breast cancer and/or in the prophylactic treatment of women with a high risk of
breast cancer development.