Apoptosis induced by droloxifene and c-myc, bax and bcl-2 mRNA expression in cultured luteal cells of rats

Droloxifene is a tamoxifen derivative whose effects in the therapy of human breast cancer and postmenopausal osteoporosis have been studied widely. We had found that droloxifene could induce apoptosis of luteal cells of rat in vitro, but its mechanisms were unknown. In the present study, the expression of c-myc, bax and bcl-2 mRNA in cultured rat luteal cells during apoptosis induced by droloxifene was investigated and possible associations between these genes and apoptosis were analyzed. Cultured luteal cells of rats were incubated with droloxifene at various concentrations and with treatment durations. Occurrence of apoptosis was detected by terminal deoxyribonucleotidyl tranferase-mediated deoxyuridine triphosphate-biotin nick end labeling (TUNEL), DNA staining and DNA electrophoresis. Expression of these genes' mRNA was determined by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR). The results showed that the c-myc and bax mRNA levels increased as concentrations or treatment durations of droloxifene increased, while the bcl-2 mRNA level exhibited no changes. A marked increase of c-myc and bax mRNA appeared respectively with 12 and 24 h of treatment, while a clear increase of apoptosis of luteal cells was found at 18 h. These results suggested that droloxifene could induce apoptosis of luteal cells of rat in vitro. The increase of c-myc mRNA expression might be one of the initiating factors and the elevated ratio of bax/bcl-2 mRNA was also probably involved in this effect. (C) 2000 Elsevier Science B.V. All rights reserved.