Oct1 regulates cell growth of LNCaP cells and is a prognostic factor for prostate cancer

The androgen receptor (AR) plays a critical role in the development and the progression of prostate cancer. Alterations in theexpression of AR coregulators lead to AR hypersensitivity, which is one of the mechanisms underlying the progression ofprostate cancer into a castrate-resistant state. Octamer transcription factor 1 (Oct1) is a ubiquitous member of the POUhomeodomainfamily that functions as a coregulator of AR. In our study, the contribution of Oct1 to prostate cancerdevelopment was examined. Immunocytochemistry analysis showed that Oct1 is expressed in the nuclei of LNCaP cells.siRNA-mediated silencing of Oct1 expression inhibited LNCaP cell proliferation. Immunohistochemical analysis of Oct1expression in tumor specimens obtained from 102 patients with prostate cancer showed a positive correlation of Oct1immunoreactivity with a high Gleason score and AR immunoreactivity (p 5 0.0042 and p < 0.0001, respectively). Moreover,patients with high immunoreactivity of Oct1 showed a low cancer-specific survival rate, and those patients with highimmunoreactivities of both Oct1 and AR exhibited poorer cancer-specific prognosis. Multivariate hazard analysis revealed asignificant correlation between high Oct1 immunoreactivity and poor cancer-specific survival (p 5 0.012). These resultsdemonstrate that Oct1 can be a prognostic factor in prostate cancer as a coregulator of AR and may lead to the developmentof a new therapeutic intervention for prostate cancer.