MP62-10 TMPRSS2-ERG GENE FUSION IS AN UNCOMMON SOMATIC ALTERATION IN HYPOGONADAL MEN WITH PROSTATE CANCER

Abstract

INTRODUCTION AND OBJECTIVES: Despite advances in diagnosis and treatment of prostate cancer, development of metastases remains a major clinical challenge. Maspin (SERPINB5), a unique member of the serpin (serine protease inhibitor) family, is a secreted protein encoded by a class II tumor suppressor gene, shown to regulate cell motility, invasion and regulates tumor metastasis. Loss of maspin has been frequently identified in clinical prostate cancer specimens and prostate cancer cell lines, therefore mechanistic understanding of its loss will provide new perspectives to develop novel therapeutics. METHODS: Maspin expression was examined in human prostate cancer specimens of various Gleason grades, and in various human prostate cancer cell lines. Preparation of class I histone deacetylase (HDAC 1, 2, 3 and 8) knockout was achieved by infecting human prostate cancer LNCaP cells with shV and shHDAC1-8 in PLK0.1 plasmids. Human prostate cancer cells were treated with various doses of HDAC inhibitors in timeand dose-dependent manner. Migration assays were performed along with expression of maspin, and class I HDACs activity was determined by immunoblotting and ELISA assay. Immunoprecipitation and ChIP was performed in LNCaP and HDAC silenced cells to study the association between maspin and p53. RESULTS: Studies performed on benign and prostate cancer specimens demonstrate progressive loss of maspin expression which correlated with increasing Gleason score. Maspin promoter methylation and deletion analysis on tissue specimens did not contribute to the loss of maspin. Treatment of human prostate cancer DU145 and LNCaP cells with sodium butyrate and trichostatin A, inhibitors of HDACs, resulted in marked increase in maspin expression and acetylation of H3/ H4 histone proteins, as a consequence of downregulation of Class I HDACs. Individual knockdown of HDAC 1, 2, 3 and 8 in LNCaP cells caused an increase in maspin expression which was more pronounced in HDAC 1, 3 and 8 knockdown cells followed by increase in p53 expression. HDAC 1-8 knockout cells exhibited slow migration ability, compared to LNCaPshV cells. ChIP assay further confirmed silencing of class I HDACs in LNCaP cells facilitated the association between maspin and p53. CONCLUSIONS: Our results demonstrate that loss of maspin is due to upregulation of class I HDACs and HDAC inhibitors led to increase in maspin expression and activity, in part, mediated by p53 activation in prostate cancer.