Prostate-specific antigen (PSA) has emerged as the most useful marker for management of patients with prostate cancer. The regulation of this glycoprotein in vivo has important clinical implications. Indirect evidence indicates that the PSA glycoprotein might be regulated by androgens, and previous studies in this laboratory have demonstrated that PSA mRNA is upregulated by androgens. The current work reports a detailed study of PSA glycoprotein expression as influenced by steroid hormones in a human prostatic adenocarcinoma cell line, LNCaP. First, we have examined the steroid binding specificity of the androgen receptor in this cell line. In comparison with wild-type rat androgen receptor in prostate, the receptor in LNCaP cells has altered affinity for a number of steroids or analogs such as progesterone (R5020), antiprogesterone (RU486), two antiandrogens (cyperoterone acetate and hydroxyflutamide), and an androgen metabolite (epitestosterone). However, its affinity for androgens (mibolerone, dihydrotestosterone, and testosterone) is not changed. The receptor does not bind to the synthetic glucocorticoids (triaminolone acetonide and dexamethasone) nor to a synthetic estrogen DES (diethylstilbestrol). The change of the steroid binding specificity of the receptor is correlated with a single mutation (A----G at nucleotide #876 relative to the initiation codon) of the steroid binding domain of the receptor. The mutation and alteration of steroid-binding specificity of the androgen receptor is also correlated with PSA glycoprotein expression affected by different ligands tested. We have demonstrated that the PSA glycoprotein is upregulated by androgens and is affected by neither epidermal growth factor nor basic fibroblast growth factor. Moreover, PSA glycoprotein could be induced by R5020, estradiol, and epitestosterone; but neither glucocorticoids nor DES had any effect on PSA induction. Interestingly, although the antiandrogen, cyperotone acetate, had the ability to induce PSA, both RU486 and hydroxyflutamide could block androgen and progesterone induction of PSA glycoprotein. Therefore, we conclude that the PSA glycoprotein expression is influenced predominantly by androgens via its receptor, and the mutation of the receptor can affect the expression of this cellular gene by the steroids other than androgens.