Elongation factor‐2 kinase regulates TG2/β1 integrin/Src/uPAR pathway and epithelial–mesenchymal transition mediating pancreatic cancer cells invasion

Abstract

Pancreatic ductal adenocarcinoma is one of the lethal cancers with extensive local tumour invasion, metastasis, early systemic dissemination and poorest prognosis. Thus, understanding the mechanisms regulating invasion/metastasis and epithelial–mesenchymal transition (EMT), is the key for developing effective therapeutic strategies for pancreatic cancer (PaCa). Eukaryotic elongation factor-2 kinase (eEF-2K) is an atypical kinase that we found to be highly up-regulated in PaCa cells. However, its role in PaCa invasion/progression remains unknown. Here, we investigated the role of eEF-2K in cellular invasion, and we found that down-regulation of eEF-2K, by siRNA or rottlerin, displays impairment of PaCa cells invasion/migration, with significant decreases in the expression of tissue transglutaminase (TG2), the multifunctional enzyme implicated in regulation of cell attachment, motility and survival. These events were associated with reductions in β1 integrin/uPAR/MMP-2 expressions as well as decrease in Src activity. Furthermore, inhibition of eEF-2K/TG2 axis suppresses the EMT, as demonstrated by the modulation of the zinc finger transcription factors, ZEB1/Snail, and the tight junction proteins, claudins. Importantly, while eEF-2K silencing recapitulates the rottlerin-induced inhibition of invasion and correlated events, eEF-2K overexpression, by lentivirus-based expression system, suppresses such rottlerin effects and potentiates PaCa cells invasion/migration capability. Collectively, our results show, for the first time, that eEF-2K is involved in regulation of the invasive phenotype of PaCa cells through promoting a new signalling pathway, which is mediated by TG2/β1 integrin/Src/uPAR/MMP-2, and the induction of EMT biomarkers which enhance cancer cell motility and metastatic potential. Thus, eEF-2K could represent a novel potential therapeutic target in pancreatic cancer.

Transglutaminase is a tumor cell and cancer stem cell survival factor

“…Eukaryotic elongation factor‐2 kinase (eEF‐2K), an atypical kinase, is increased in pancreatic cancer cells. Recent studies show that suppression of eEF‐2K with siRNA impairs pancreatic cancer cell migration/invasion and that this is associated with reduced TG2 level and reduced EMT . Thus, as described for other cancer cell types, loss of TG2 is associated with reduced EMT .…”

Transglutaminase 2 takes center stage as a cancer cell survival factor and therapy target

“…Moreover, knockdown of eEF2K reduces cell invasion and migration, and reduces TG2 mRNA and protein level. TG2 appears to have a role in regulating downstream signaling events, as knockdown of either eEF2K, or TG2, reduces Snail and ZEB1 level leading to reduced EMT (Figure A) Thus, eukaryotic elongation factor‐2 kinase appears to utilize TG2 to enhance pancreatic cancer cell migration, invasion and EMT. TG2 also regulates pancreatic cell morphology, since TG2 silencing reduces the 2‐O‐tetradecanoylphorbol‐13‐acetate dependent phosphorylation of keratin 8, and suppresses 2‐O‐tetradecanoylphorbol‐13‐acetate dependent keratin filament reorganization in PANC‐1 cells .…”

“…Eukaryotic elongation factor‐2 kinase (eEF2K) is a negative regulator of protein elongation that acts via phosphorylation of eukaryotic elongation factor 2 (eEF2), and is a key component of the translation machinery . eEF2K is overexpressed in pancreatic cancer cells and is associated with elevated TG2 level (Figure A). Moreover, knockdown of eEF2K reduces cell invasion and migration, and reduces TG2 mRNA and protein level.…”

β1 and β3 integrins in breast, prostate and pancreatic cancer: A novel implication (Review)

“…However, this metastasis induced by β1 integrin depends on the expression of EGFR and the phosphorylation of AKT, which is a downstream signaling protein of EGFR (20). Furthermore, in certain types of cancer, the data demonstrated that β1 integrin may activate Src or phosphorylate p38 and AKT to affect urokinase-type plasminogen activator (uPA), and matrix metalloprotease (MMP)-2, promoting the metastasis of cancer cells (21,22). Additionally, due to the lack of vasculature, cancer cells enhance β1 integrin activity to induce vessel cooption by adhering to the vascular basement membrane, thus providing immediate vasculature structures for newly metastatic or locally invasive of cancer cells (23).…”