Ubiquitous Mitochondrial Creatine Kinase Is Overexpressed in the Conditioned Medium and the Extract of LNCaP Lineaged Androgen Independent Cell Lines and Facilitates Prostate Cancer Progression

BACKGROUND. Androgen independent prostate cancer (AIPC) is not responsive to androgen ablation therapy. The biomarkers of AIPC are lack. Numerous proteomics studies have focused on finding new markers of AIPC and exploring their possible functions, but little is known about the difference between conditioned medium (CM) from AIPC and androgen dependent prostate cancer (ADPC) cells. METHODS. We performed a proteome analysis of CM from LNCaP, C4-2, and C4-2B cells by a two dimensional electrophoresis based technology. Western blots and immunohistochemical studies were employed to explore the expression pattern of the identified protein in prostate cancer cell lines and clinical specimens, respectively. Then we examined the possible roles and mechanisms of the ubiquitous mitochondrial creatine kinase (uMtCK) in vitro. RESULTS. Besides prostate specific antigen (PSA) and insulin-like growth factor binding protein-2 (IGFBP2), uMtCK was identified in the CM of ATPC cells. uMtCK was up-regulated in AIPC cells and in human prostate cancer tissues at WHO grade III. Stably transfected exogenous uMtCK showed a growth promoting effect rather than mock vector in LNCaP cells, with or without bicalutamide in culture medium. Further assays showed that higher degrees of ROS generation and Akt signaling pathway activation in LNCaP-uMtCK than in LNCaP-neo cells. CONCLUSIONS. We showed that uMtCK could be easily detected in CM of LNCaP lineaged AIPC cells. Exogenous uMtCK in LNCaP cells surprisingly contributed to overproduction of ROS, activation of Akt signaling pathway and more aggressive phenotypes including androgen independence development. Prostate 69:1176-1187, 2009. (C) 2009 Wiley-Liss, Inc.