TheProstate69:1109^1118(2009) Identificationof m-Crystallinasan Androgen-RegulatedGeneinHumanProstateCancer Kamilla Malinowska, 1 Ilaria T. Cavarretta, 1 Martin Susani, 2 Oliver A. Wrulich, 3 Florian U ¨ berall, 3 Lukas Kenner, 2,4 and Zoran Culig 1 * 1 Departmentof Urologyand Biocenter,Innsbruck Medical University,Innsbruck, Austria 2 Institute of Clinical Pathology, Medical Universityof Vienna,Vienna, Austria 3 Biocenter,Divisionof Medical Biochemistry,Innsbruck Medical University,Innsbruck, Austria 4 Ludwig Boltzmann Institutefor Cancer Research,Vienna, Austria BACKGROUND. Androgen receptor (AR) signaling is implicated in prostate cancer progression. Therefore, identification of AR downstream genes is potentially important for selection of novel markers and therapy targets in prostate cancer. METHODS. Expression of a thyroid hormone T3-binding protein m-crystallin (CRYM) mRNA and protein in cell lines was evaluated by real-time PCR and Western blot, respectively. CRYM expression in vivo was analyzed in patients’ samples by immunohistochemistry. The effects of androgen and T3 on proliferation of MDA PCa 2b cells were assessed by 3 H-thymidine uptake assay. RESULTS. CRYM expression was detected in AR-positive LNCaP and MDA PCa 2b cells. In MDA PCA 2b cells, CRYM was regulated by androgens. Androgen-induced CRYM expression was diminished by antiandrogens or AR siRNA. Inhibition of transcription by a-amanitin caused a reduction in CRYM mRNA. The lack of CRYM expression was noted in LAPC-4 cells and in AR-negative prostate cancer cell lines PC-3 and DU-145. CRYM protein was increased in cancer tissue and decreased in samples from patients after hormonal therapy. In samples from patients with therapy-refractory cancer CRYM was not detectable. We also found that androgens and T3 have additive effects on stimulation of MDA PCa 2b cells proliferation. CONCLUSION. CRYM is a novel androgen-regulated gene whose expression is elevated in prostate cancer but down-regulated in castration therapy-resistant tumors. Prostate 69: 1109 – 1118, 2009. # 2009 Wiley-Liss, Inc. KEY WORDS: prostate cancer; m-crystallin; androgen receptor INTRODUCTION Prostate cancer is the most common malignancy among men in Europe [1] and in the United States [2]. The growth and development of prostate gland are regulated by androgenic hormones that are also implicated in carcinogenesis. The action of androgens is mediated by androgen receptor (AR) that is the main transcription factor in prostate cells. Upon ligand binding, AR is activated and translocates to the nucleus where AR dimers bind to androgen response elements on promoters of androgen-regulated genes. As a consequence, the transcription of downstream genes occurs. Several mechanisms implicated in prostate cancer progression are AR-related. The main and most successful therapy for non-organ-confined tumors is androgen ablation [3]. This therapy improves quality of life but is still palliative. Despite a favorable initial response, castration-resistant disease develops after 3 – 5 years. These tumors are heterogenous and still Lukas Kenner and Zoran Culig contributed equally to this work. Grant sponsor: European Union; Grant sponsor: Prostate Cancer Integrated Management Approach (PRIMA). *Correspondence to: Zoran Culig, MD, Department of Urology, Innsbruck Medical University, Anichstrasse 35, A-6020 Innsbruck, Austria. E-mail: zoran.culig@i-med.ac.at Received 30 January 2009; Accepted 3 March 2009 DOI 10.1002/pros.20956 Published online 7 April 2009 in Wiley InterScience (www.interscience.wiley.com). ß2009Wiley-Liss,Inc.