Impairments in the androgen-signaling transduction cascade have been described in prostatic tumor cell lines and in tumor specimens [for review see ref. 1], These alterations are quantitative [absence of the androgen receptor (AR) transcript] and qualitative (AR point muta tions). The two mutant prostatic ARs, AR Met715 and AR Ala877, are activated not only by androgens, but also by a wide spectrum of steroid hormones and nonsteroidal anti hormones [2, 3]. Another type of aberrant stimulation is reported for the estrogen and progesterone receptor. These receptors mediate gene transcription not only in response to estradiol and progesterone, but also in re sponse to growth factors, second messenger cyclic adeno sine monophosphate, protein kinase activators and dopa mine [4-6], Cross-talk between a growth factor and the AR may be of importance for the pathophysiology of pros tatic carcinoma. Therefore, this study was designed to investigate a possible interaction of growth factors with the androgen-signal transduction cascade in prostate tu mor cell lines, which represent advanced stage of the dis ease. the promoter of the prostate-specific antigen (PSA) gene. About 20 h after transfection, either synthetic androgen methyltrienolone or one of growth factors were added. CAT activity was measured in cell extracts after incuba tion for about 32 h. In control experiments DU-145 cells were cotransfected with a reporter plasmid and the empty expression vector. The control portion of cells was treated in the same way as described above. Initially, the effects of methyltrienolone and growth factors on AR-mediated transactivation of the promoter containing two AREs were evaluated (fig. 1). Maximal stimulation of the AR by androgen was achieved with 5 irM of methyltrienolone. Insulin-like growth factor-I (IGF-I), at a concentration of 50 ng/ml, stimulated recep tor-mediated CAT activity to the same extent as synthetic androgen. In this reporter system, CAT activity increased to a level of about two thirds of the maximum after treat ment with 50 ng/ml of kératinocyte growth factor (KGF). Epidermal growth factor displayed minor stimulatory effects, whereas IGF-II and basic fibroblast growth factor did not stimulate increase in CAT activity. The nonsteroi dal antiandrogen casodex, at a concentration of 5 pM, completely suppressed increase in CAT activity induced either by methyltrienolone or growth factors. When DU-145 cells were cotransfected with a reporter gene and an empty expression vector and treated with methyltrieno lone or growth factors, CAT activity remained at the basal level.

DU-145 cells, which do not contain endogenous ste roid receptors, were cotransfected by means of the lipo some-mediated transfection with an androgen-inducible chloramphenicol acetyltransferase (CAT) gene and an AR expression vector. The reporter gene was driven either by artificial promoters consisting of one or two androgenresponsive elements (AREs) in front of a TATA box or by