Constitutive activation of
phosphoinositide 3-kinase (PI3K)-Akt pathway transmits growth-regulatory signals that play a central role in promoting survival, proliferation, and angiogenesis in human
prostate cancer cells. Here, we assessed the efficacy of
inositol hexaphosphate (IP6) against invasive human
prostate cancer PC-3 and C4-2B cells and regulation of PI3K-Akt pathway. IP6 treatment of cells suppressed proliferation, induced apoptosis along with
caspase-3 and
poly(ADP-ribose) polymerase (PARP) cleavage, and inhibited constitutive activation of Akt and its upstream regulators PI3K,
phosphoinositide-dependent kinase-1 and
integrin-linked kinase-1 (ILK1). Downstream of Akt, IP6 inhibited the phosphorylation of
glycogen synthase kinase-3alpha/beta at Ser(21/9) and consequently reduced
cyclin D1 expression. Efficacy studies employing PC-3
tumor xenograft growth in nude mice showed that 2% (w/v) IP6 feeding in
drinking water inhibits
tumor growth and weight by 52% to 59% (P < 0.001). Immunohistochemical analysis of xenografts showed that IP6 significantly reduces the expression of molecules associated with cell survival/proliferation (ILK1, phosphorylated Akt,
cyclin D1, and
proliferating cell nuclear antigen) and angiogenesis (
platelet endothelial cell adhesion molecule-1 or CD31,
vascular endothelial growth factor,
endothelial nitric oxide synthase, and
hypoxia-inducible factor-1alpha) together with an increase in apoptotic markers (cleaved
caspase-3 and PARP). These findings suggest that, by targeting the PI3K-ILK1-Akt pathway, IP6 suppresses cell survival, proliferation, and angiogenesis but induces death in
prostate cancer cells, which might have translational potential in preventing and controlling the growth of advanced and aggressive
prostate cancer for which conventional
chemotherapy is not effective.