Pancreatic cancer (PaCa) is one of the most aggressive, apoptosis-resistant and currently incurable
cancers with a poor survival rate.
Eukaryotic elongation factor-2 kinase (eEF-2K) is an atypical
kinase, whose role in PaCa survival is not yet known. Here, we show that eEF-2K is overexpressed in PaCa cells and its down-regulation induces apoptotic cell death.
Rottlerin (ROT), a polyphenolic compound initially identified as a PKC-δ inhibitor, induces apoptosis and autophagy in a variety of
cancer cells including PaCa cells. We demonstrated that ROT induces intrinsic apoptosis, with dissipation of mitochondrial membrane potential (ΔΨm), and stimulates extrinsic apoptosis with concomitant induction of
TNF-related apoptosis inducing ligand (
TRAIL) receptors, DR4 and DR5, with
caspase-8 activation, in PANC-1 and MIAPaCa-2 cells. Notably, while none of these effects were dependent on PKC-δ inhibition, ROT down-regulates eEF-2K at
mRNA level, and induce eEF-2K protein degradation through
ubiquitin-
proteasome pathway. Down-regulation of eEF-2K recapitulates the events observed after ROT treatment, while its over-expression suppressed the ROT-induced apoptosis. Furthermore, eEF-2K regulates the expression of
tissue transglutaminase (TG2), an
enzyme previously implicated in proliferation, drug resistance and survival of
cancer cells. Inhibition of eEF-2K/TG2 axis leads to
caspase-independent apoptosis which is associated with induction of
apoptosis-inducing factor (AIF). Collectively, these results indicate, for the first time, that the down-regulation of eEF-2K leads to induction of intrinsic, extrinsic as well as AIF-dependent apoptosis in PaCa cells, suggesting that eEF-2K may represent an attractive therapeutic target for the future
anticancer agents in PaCa.