Trinath P. Das, Suman Suman, A.M. Sashi Papu John, Deeksha Pal, Angelena Edwards, Houda Alatassi, Murali K. Ankem, Chendil Damodaran

The activation of AKT governs many signaling pathways and promotes cell growth and inhibits apoptosis in human malignancies including prostate cancer (CaP). Here, we investigated the molecular association between AKT activation and the function of death-associated protein kinase 3 (DAPK3) in CaP. An inverse correlation of pAKT and DAPK3 expression were seen in a panel of CaP cell lines. Inhibition of AKT by wortmannin/LY294002 or overexpression of DAPK3 reverts the growth inhibitory function AKT in CaP cells. On the other hand, ectopic expression of AKT inhibited DAPK3 function and induced proliferation of Cap cells. In addition, AKT over-expressed tumors exhibit aggressive growth versus control vector-induced prostate tumors in xenograft models. The immunohistochemistry results revealed a down-regulation of DAPK3 expression in AKT over-expressed tumors. This was evident versus control tumors. Finally, we examined expression pattern of AKT and DAPK3 in human CaP specimens-the expected gradual increase and nuclear localization of pAKT was seen in higher Gleason score samples versus benign hyperplasia (BPH). On the contrary, reduced expression of DAPK3 was seen in higher Gleason stages versus BPH. This suggests that inhibition of DAPK3 may be a contributing factor to the carcinogenesis of the prostate. Understanding the mechanism by which AKT negatively regulates DAPK3 function may suggest whether DAPK3 can be therapeutic target for CaP.