Expression and Function of ATIP/MTUSI in Human Prostate Cancer Cell Lines

BACKGROUND. We have previously demonstrated Ang II type 2 (AT(2)-) receptor-mediated inhibition of EGF-induced prostate cancer cell growth in androgen-dependent (LNCaP) and independent (PC3) prostate cancer cell lines. METHODS. To explore the signaling pathways involved in this inhibitory effect, we examined the interaction of the AT(2)-receptor with its novel regulatory partner ATIP using real time PCR, over-expression, siRNA and [(3)H] thymidine incorporation assays. RESULTS. The results in human prostate cancer cell lines demonstrate the presence of ATIP in both cell lines examined, and suggest that (i) the AT(2)-receptor through an interaction with ATIP mediates an anti-growth factor effect in both androgen-dependent and androgen-independent cell lines; (ii) ATIP expression decreases as the rate of cell growth and androgen-independence increase; and (iii) EGF may act on cell growth in part by reducing the content of ATIP present in the cells. CONCLUSIONS. The results support our earlier proposal in normal cell lines that ATIP is an important component of the cellular response to AT(2)-receptor activation. The results further suggest that a critical level of ATIP is required to mediate the effect of AT(2)-receptor activation to inhibit EGF mediated increases in cell growth. They also suggest that EGF may in part induce cell growth by suppressing the level of ATIP expression. Prostate 70: 1563-1574, 2010. (C) 2010 Wiley-Liss, Inc.