Mp66-17 expression of glucocorticoid receptors, androgen receptors and its splice variants in prostate cancer: comparison between hormone dependent and castrate-resistant prostate cancer

protein 4 (Reg IV) as a biomarker of castration-resistant prostate cancer (CRPC). METHODS: The serum Reg IV level in 39 prostate cancer (PC) patients, 36 renal cell cancer (RCC) patients, 12 urothelial cancer (UC) patients, and 14 non-cancerous subjects was measured using an enzyme-linked immunosorbent (ELISA) assay. The cell viability of PC3 and LNCaP stably transfected with Reg IV cDNA (PC3-reg and LN-reg, respectively) was examined using an MTT assay. The expression of molecules related to epithelial-mesenchymal transition (EMT), neuroendocrine differentiation, and apoptosis in these cells was examined using western immunoblot analysis. RESULTS: Serum concentration levels of Reg IV in patients with PC, RCC, or UC were significantly higher than those in noncancerous subjects (p1⁄40.0131, p1⁄40.0122 and p1⁄40.0002, respectively). The levels with metastatic PC and metastatic RCC were significantly higher than those with early stages in each of the diseases (p1⁄40.0051 and p1⁄40.0006, respectively). A significant correlation was found between the serum Reg IV and PSA level in androgen-naive prostate cancer patients (p1⁄40.0059, R1⁄40.519). The level in CRPC patients was significantly higher than that in the androgen-naive prostate cancer patients (p1⁄40.0202) and in the non-cancerous subjects (p1⁄40.001). In all CRPC patients, it was higher than 2 ng/ml, which has been defined as the cut-off value in gastrointestinal cancer in previous studies. An EMT was induced in LN-reg. The expression of synaptophysin, NSE, and chromogranin A was upregulated in both LN-reg and PC3-reg compared with in vector control cells. The cell viability under androgen deprivation was enhanced in both LN-reg and PC3-reg, and the resistance of 5-fluorouracil and docetaxel was shown in PC3-reg. CONCLUSIONS: Reg IV is a candidate for a novel biomarker of CRPC, and it might represent the effect of therapeutic agents.