Translationally controlled tumor protein (TCTP) in the human prostate and prostate cancer cells: expression, distribution, and calcium binding activity.

Abstract

The translationally controlled tumor protein (TCTP) is an abundantly expressed protein found in a wide range of organisms from both the animal and plant kingdom. Initially described as a growth-related protein, knowledge of the biological actions of TCTP has been recently extended to include calcium binding, regulation of apoptosis, and microtubules stabilization. This report describes expression, distribution, and characterization of TCTP in human prostatic tissues and cell lines. Samples were analyzed by Western blot, RT-PCR, immunohistochemistry, and confocal microscopy. Calcium binding activity of the recombinant human prostatic protein was evaluated on a calcium overlay assay. A public SAGE database was analyzed to determine TCTP expression levels in normal and cancer tissues. TCTP protein and mRNA were detected in all the specimens and cell lines analyzed. The protein was mainly expressed by the secretory luminal epithelial and basal layer cells. A significant amount of protein was present in the prostatic fluids. Subcellular distribution studies in prostate epithelial cells detected the protein in the cytoplasm in interphase and colocalized with tubulin during mitosis. The calcium binding capacity of prostatic TCTP was shown in vitro. Finally, SAGE data indicated TCTP as the calcium binding protein with the highest expression levels among those examined. The results of the present study demonstrate, for the first time, the expression of TCTP in the human prostate and in prostate cancer cells, and suggest the involvement of the protein in key-processes such as apoptosis, cellular differentiation, and in the control of sperm functions.