Impact of phospho-Akt expression on the clinical outcome and activity of gemcitabine and Akt inhibitors in pancreatic ductal adenocarcinoma

Abstract

Background: Pancreatic ductal adenocarcinoma (PDAC) is among the most lethal solid tumors. Despite extensive preclinical and clinical research, the prognosis of this disease has not significantly improved, with a 5-year survival rate around 7%. There is an urgent need to better understand the molecular pathology of PDAC in order to improve patient selection for current treatment options and to develop novel therapeutic strategies. The PI3K/AKT/mTOR pathway plays a crucial role in PDAC: activation of Akt is a frequent event and has been correlated to poor prognosis and resistance to chemotherapy. Against this background, effective blockage of Akt signaling can lead to programmed cell death and inhibition of tumor growth. Several inhibitors of Akt under investigation include perifosine, which prevents Akt translocation to the cell membrane, MK-2206 which is an Akt allosteric inhibitor and BEZ-235 which is a dual PI3K/ mTOR inhibitor. The aims of this study were to investigate 1) the prognostic role of Akt in PDAC tissues and 2) the molecular mechanisms underlying the interaction of Akt inhibitors with gemcitabine in PDAC cells and primary cultures. Materials and methods: Immunohistochemistry of tissue microarrays with specimens from radically-resected patients (n ¼ 100) revealed a correlation between high phospho-Akt1 expression and worse outcome. Patients with low expression had a median overall survival (OS) of 16.2 months (95%CI, 14.8-20.1), while patients with high expression had a median OS of 12.0 months (95%CI, 9.0-14.9, P ¼ 0.03). Results: Akt inhibitors synergistically enhanced the antiproliferative activity of gemcitabine in the LPC028 primary cells, characterized by high expression levels, while this combination was antagonistic in LPC006 cells, characterized by low expression levels. Inhibition of Akt decreased cell migration and invasion, which was additionally reduced by the combination with gemcitabine. However, the combination of Akt inhibitors with gemcitabine significantly increased apoptosis, associated with induction of caspase-3/6/8/9, PARP and BAD, and inhibition of Bcl-2 and NF-kB in LPC028, but not in LPC006 cells. Conclusions: Our results support the analysis of phospho-Akt as a new biomarker both for PDAC prognosis and for the development of new therapeutic approaches. In particular, perifosine interact synergistically with gemcitabine in cells with phosphoAkt overexpression