Perifosine as a Potential Novel Anti-Cancer Agent Inhibits EGFR/MET-AKT Axis in Malignant Pleural Mesothelioma

PI3K/AKT signalling pathway is aberrantly active and plays a critical role for cell cycle progression of human malignant pleural mesothelioma (MMe) cells. AKT is one of the important cellular targets of perifosine, a novel bio-available alkylphospholipid that has displayed significant anti-proliferative activity in vitro and in vivo in several human tumour model systems and is currently being tested in clinical trials.We tested Perifosine activity on human mesothelial cells and different mesothelioma cell lines, in order to provide evidence of its efficacy as single agent and combined therapy.We demonstrate here that perifosine, currently being evaluated as an anti-cancer agent in phase 1 and 2 clinical trials, caused a dose-dependent reduction of AKT activation, at concentrations causing MMe cell growth arrest. In this study we firstly describe that MMe cells express aside from AKT1 also AKT3 and that either the myristoylated, constitutively active, forms of the two proteins, abrogated perifosine-mediated cell growth inhibition. Moreover, we describe here a novel mechanism of perifosine that interferes, upstream of AKT, affecting EGFR and MET phosphorylation. Finally, we demonstrate a significant increase in cell toxicity when MMe cells were treated with perifosine in combination with cisplatin.This study provides a novel mechanism of action of perifosine, directly inhibiting EGFR/MET-AKT1/3 axis, providing a rationale for a novel translational approach to the treatment of MMe

Targeting Signal Transduction Pathways in Metastatic Breast Cancer: A Comprehensive Review

This review summarizes some of the key signaling pathways involved in tumor progression and some of the novel therapies that are in development for the treatment of metastatic breast cancer patients

Dysregulation of Cell Polarity Proteins Synergize with Oncogenes or the Microenvironment to Induce Invasive Behavior in Epithelial Cells

Changes in expression and localization of proteins that regulate cell and tissue polarity are frequently observed in carcinoma. However, the mechanisms by which changes in cell polarity proteins regulate carcinoma progression are not well understood. Here, we report that loss of polarity protein expression in epithelial cells primes them for cooperation with oncogenes or changes in tissue microenvironment to promote invasive behavior. Activation of ErbB2 in cells lacking the polarity regulators Scribble, Dlg1 or AF-6, induced invasive properties. This cooperation required the ability of ErbB2 to regulate the Par6/aPKC polarity complex. Inhibition of the ErbB2-Par6 pathway was sufficient to block ErbB2-induced invasion suggesting that two polarity hits may be needed for ErbB2 to promote invasion. Interestingly, in the absence of ErbB2 activation, either a combined loss of two polarity proteins, or exposure of cells lacking one polarity protein to cytokines IL-6 or TNFα induced invasive behavior in epithelial cells. We observed the invasive behavior only when cells were plated on a stiff matrix (Matrigel/Collagen-1) and not when plated on a soft matrix (Matrigel alone). Cells lacking two polarity proteins upregulated expression of EGFR and activated Akt. Inhibition of Akt activity blocked the invasive behavior identifying a mechanism by which loss of polarity promotes invasion of epithelial cells. Thus, we demonstrate that loss of polarity proteins confers phenotypic plasticity to epithelial cells such that they display normal behavior under normal culture conditions but display aggressive behavior in response to activation of oncogenes or exposure to cytokines

A novel inhibitor of the PI3K/Akt pathway based on the structure of inositol 1,3,4,5,6-pentakisphosphate

Background: Owing to its role in cancer, the phosphoinositide 3-kinase (PI3K)/Akt pathway is an attractive target for therapeutic intervention. We previously reported that the inhibition of Akt by inositol 1,3,4,5,6- pentakisphosphate (InsP5) results in anti-tumour properties. To further develop this compound we modified its structure to obtain more potent inhibitors of the PI3K/Akt pathway.Methods: Cell proliferation/survival was determined by cell counting, sulphorhodamine or acridine orange/ethidium bromide assay; Akt activation was determined by western blot analysis. In vivo effect of compounds was tested on PC3 xenografts, whereas in vitro activity on kinases was determined by SelectScreen Kinase Profiling Service.Results: The derivative 2-O-benzyl-myo-inositol 1,3,4,5,6-pentakisphosphate (2-O-Bn-InsP5) is active towards cancer types resistant to InsP5 in vitro and in vivo. 2-O-Bn-InsP5 possesses higher pro-apoptotic activity than InsP 5 in sensitive cells and enhances the effect of anti-cancer compounds. 2-O-Bn-InsP5 specifically inhibits 3-phosphoinositide- dependent protein kinase 1 (PDK1) in vitro (IC 50 in the low nanomolar range) and the PDK1-dependent phosphorylation of Akt in cell lines and excised tumours. It is interesting to note that 2-O-Bn-InsP5 also inhibits the mammalian target of rapamycin (mTOR) in vitro.Conclusions: InsP5 and 2-O-Bn-InsP5 may represent lead compounds to develop novel inhibitors of the PI3K/Akt pathway (including potential dual PDK1/mTOR inhibitors) and novel potential anti-cancer drugs