SUMMARY:Mechanisms of prostate cancer (CaP) recurrence during a combined androgen blockade (CAB) are poorly understood. Previously, the role of androgen receptor (AR) gene mutations underlying the CAB therapy relapse has been raised. To investigate the hypothesis that AR gene aberrations are involved in CAB relapse, 11 locally recurrent CaP samples from patients treated with orchiectomy and bicalutamide were analyzed for copy number changes and DNA sequence alterations of the AR gene by fluorescence in situ hybridization and single-strand conformation polymorphism, respectively. Altogether, base changes were detected in four tumors (36%). Three of them were missense mutations (G166S, W741C, M749I) and two were silent polymorphisms. Interestingly, none of the tumors had AR amplification. These data suggest that different AR variants are developed and selected for during various types of hormonal treatments, and also, that CAB achieved by orchiectomy and bicalutamide does not act as a selective force for AR amplification. (Lab Invest 2001, 81:1647-1651.

SUMMARY:Progression to hormone-refractory growth of prostate cancer has been suggested to be mediated by androgen receptor (AR) gene alterations. We analyzed AR for mutations and amplifications in 21 locally recurrent prostate carcinomas treated with orchiectomy, estrogens, or a combination of orchiectomy and estramustine phosphate using fluorescence in situ hybridization, single-strand conformation polymorphism, and DNA sequence analyses. Amplification was observed in 4 of 16 (25%) and amino acid changing mutations was observed in 7 of 21 (33%) of the tumors, respectively. Two (50%) tumors with AR amplification also had missense mutation of the gene. Four of five (80%) cancers that were treated with a combination of orchiectomy and estramustine phosphate had a mutation clustered at codons 514 to 533 in the N-terminal domain of AR. In functional studies, these mutations did not render AR more sensitive to testosterone, dihydrotestosterone, androstenedione, or ␤-estradiol. Tumors treated by orchiectomy had mutations predominantly in the ligand-binding domain. In summary, we found molecular alterations of AR in more than half of the prostate carcinomas that recurred locally. Some tumors developed both aberrations, possibly enhancing the cancer cell to respond efficiently to low levels of androgens. Furthermore, localization of point mutations in AR seems to be influenced by the type of treatment. (Lab Invest 2002, 82:1591-1598. P rostate cancer (CaP) is the most common male malignancy in the Western world, and its prognosis greatly depends on at which stage the disease is diagnosed. Even in the era of prostate specific antigen (PSA) screening, advanced disease is diagnosed in 20 to 40% of patients with CaP when cure by radical prostatectomy or radiotherapy is not considered possible anymore. In addition, recurrence rates of CaP after radical surgery or radiotherapy approach 25 to 50% (Dennis and Griffiths, 2000;Määttänen et al, 1999;Scardino et al, 1994). For these patients, androgen deprivation therapy (ADT) remains the only effective palliative treatment. ADT is generally achieved by either surgical or chemical castration, but for patients with widespread, metastasized disease, the cytotoxic drug estramustine phosphate (EMP) is occasionally combined with ADT (Kuhn et al, 1994;Murphy et al, 1986). Although all ADTs are initially effective, in most patients, CaP progresses within months or a few years (Dennis and Griffiths, 2000;Scardino et al, 1994). Molecular mechanisms of ADT failure are not comprehensively known. Previous studies have suggested a link between androgen receptor (AR) gene and ADT failure (Culig et al, 1993;Elo et al, 1995;Koivisto et al, 1997;Schoenberg et al, 1994;Suzuki et al, 1993Suzuki et al, , 1996Taplin et al, 1995Taplin et al, , 1999Visakorpi et al, 1995;Wallen et al, 1999), and two main mechanisms by which CaP cells could adapt and sensitize AR signaling pathway for growth in low levels of androgens have been proposed. First, AR gene amplification has been shown to lead to increased expr...

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SUMMARY:Androgen action is mediated through androgen receptor (AR), which appears to undergo structural and functional alterations during prostate cancer (CaP) progression. AR mutations have been infrequently reported in CaP before hormonal therapy, but in untreated, advanced tumors AR mutations are suggested to be more common. To investigate the frequency of AR mutations in aggressive CaP before hormonal therapy, we have analyzed AR coding region for aberrations in 21 paraffin-embedded prostate carcinoma samples (14 primary tumors, 7 metastases) of poor histologic differentiation. Singlestranded conformational polymorphism and sequencing analyses revealed AR missense mutations in 29% (4/14) of the primary tumors and in one (14%) metastasis. Mutations resided in the transactivation domain and in the hinge region. One of the hinge region mutants, Ser646Phe, that was identified in a patient with short endocrine therapy response, exhibited a markedly increased transcriptional activity on single androgen response element-containing promoters. In conclusion, AR mutations are frequent in high-grade CaP before initiation of hormonal therapy, and these mutations may play a role in poor therapy response and emergence of hormone-refractory CaP in some cases. (Lab Invest 2003, 83:1709 -1713.