Transcriptional down-regulation of c-myc in human prostate carcinoma cells by the synthetic androgen mibolerone.

Da Wolf,F Fittler,F Kohlhuber,P Schulz,D Eick

doi:10.1038/bjc.1992.76

Abstract

The mechanism of down-regulation of c-myc RNA associated with androgen-induced suppression of the transformed phenotype in the human prostate carcinoma cell line LNCaP was investigated. The synthetic androgen mibolerone (7 alpha-17 alpha-Dimethyl-19-nortestosterone) reversibly inhibits the proliferation of LNCaP cells and, from 12-72 h after hormone addition reduces the level of c-myc transcripts to a few per cent of controls. P1, P2, and P0 c-myc transcripts decline at the same rate, whereas P3 transcripts are much less hormone sensitive. Nuclear run-on analysis revealed that c-myc is down-regulated at the level of transcription initiation in LNCaP cells. The level of c-myc transcripts prevailing in untreated control cells can be restored in androgen-induced cells by excess antiandrogen, indicating the involvement of the androgen receptor in c-myc down-regulation.

Highlights

Summanr The mechanism of dow n-regulation of c-mvc RNA associated With androgen-induced suppression of the transformed phenotype in the human prostate carcinoma cell line LNCaP was investigated
C-mvc RNA is markedly induced upon stimulation of resting cells by mitogens to pass from Go to G1 (Kelly et al.. 1983: Campisi et al.. 1984)
When LNCaP cells are maintained in the presence of mibolerone a decline in c-mvc RNA levels becomes clearly visible after 12-48 h (Figure 2a)

Summary

Cell culture and hormones

The prostate carcinoma cell line LNCaP (HoroszeWicz et al.. 1980) was from the Human Tumor Cell Laboratory. 1980) was from the Human Tumor Cell Laboratory. LNCaP cells between passages 75 and 90 were used for the experiments described. Cells were maintained in RPMI medium as monolayers in the presence of 10% FCS and phenol red. For the preparation of seed stocks, cells were c-mvc SU-PPRESSION BY SYNTHETIC ANDROGEN 377 grown to 50 to 75% confluency before use. Hormones were added 48 h after seeding as ethanol solutions to give a final concentration as indicated in the figures. 7a- 1 7x-Dimethyl- 1 9-nortestosterone (mibolerone; Upjohn).

SI mapping

Results

GAPDH b la za

CN z x t