Abstract: OBJECTIVE: In a cross-sectional, retrospective, non-randomised study to investigate the possibility that some patients treated with luteinizing hormone releasing hormone analogues (LHRH analogues) fail to reach castration levels of serum testosterone. METHODS: 40 patients treated with a 3-monthly formulation of leuprolide acetate and continuous use of an oral antiandrogen ("Leu group") and 25 patients treated with a 3-monthly formulation of goserelin acetate and an oral antiandrogen for one month ("Gos group") were identified from our hospital's registry. Serum testosterone was measured during treatment with the respective LHRH-analogue and compared between the two groups. In the Leu group, serum testosterone was measured during week 11 or 12 of treatment. In the Gos group, serum testosterone was assessed during week 23 or 24. RESULTS: Four patients (10%) treated with leuprolide acetate failed to reach the castration level of serum testosterone after treatment with one injection of a three-monthly formulation of leuprolide acetate. All patients treated with goserelin acetate achieved the castration level. CONCLUSION: Although the overwhelming majority of prostate cancer patients during treatment of LHRH analogue achieve serum testosterone values within the castration range, individual patients may fail to reach this therapeutic goal, probably more often during treatment with leuprolide acetate than with goserelin acetate.

Abstract: Receptor-interacting protein (RIP) 140 interacts with several nuclear receptors, but its function in regulation of nuclear receptor action has been debated. Here we have examined the role of RIP140 in regulation of Steroidogenic factor-1 (SF-1)-dependent transcription. SF-1 interacts with RIP140 through its activation function-2 (AF-2) domain. Several domains of RIP140 interact directly with SF-1, but the carboxyl-terminal region containing 4 of its 9 LXXLL motifs showed the strongest SF-1 interaction. Coexpression of RIP140 and SF-1 in different cell types demonstrated that RIP140 acts as a potent corepressor of transcription from the SF-1 responsive cAMP regulatory sequence 2 (CRS2) element of the CYP17 gene and a variety of SF-1 responsive promoter genes. RIP140 also counteracted the stimulatory action of p160/SRC coactivators. The inhibitory effect of RIP140 was partially reversed by Trichostatin A, suggesting a role of histone deacetylase (HDAC) activity in RIP140-mediated repression of SF-1. Quantitation of endogenous coregulator mRNA levels revealed cell type specific differences that could affect the repressor action by overexpressed RIP140.

Abstract: Several lines of evidence have suggested that the nuclear receptor Steroidogenic Factor-1 (SF-1 or Ad4BP) may be directly involved in the cAMP-dependent regulation of steroid hydroxylase genes in adrenocortical cells. In the bovine CYP17 gene, which encodes the cytochrome P450 17alpha-hydroxylase, an SF-1 site is present within cAMP-responsive sequence 2 (CRS2) and mutations which interfere with SF-1 binding correlate with decreases in cAMP-stimulated transcription of a linked reporter gene. In order to determine whether the cAMP response relies on structures within SF-1 itself, mutations and deletions were introduced. We demonstrate that even a single point mutation (E454A) in the transactivating AF-2 domain drastically reduces the ability of SF-1 to mediate cAMP-dependent transcription. Furthermore, the mutation results in a protein which acts in a dominant negative fashion with respect to cAMP-dependent regulation of the bovine CYP17 gene. Finally, we demonstrate that the coactivators CBP and SRC-1 are limiting with respect to cAMP-induced CRS2-dependent transcription in Y1 adrenocortical tumor cells, suggesting that part of the action of cAMP may be to influence the interaction of SF-1 with other cofactors via the AF-2 domain.