Targeted intervention of eIF4A1 inhibits EMT and metastasis of pancreatic cancer cells via c-MYC/miR-9 signaling

Background: Owing to the lack of effective treatment options, early metastasis remains the major cause of pancreatic ductal adenocarcinoma (PDAC) recurrence and mortality. However, the molecular mechanism of early metastasis is largely unknown. We characterized the function of eukaryotic translation initiation factors (eIFs) in epithelial-mesenchymal-transition (EMT) and metastasis in pancreatic Cancer cells to investigate whether eIFs and downstream c-Myc affect EMT and metastasis by joint interference.

Methods: We used The Cancer Genome Atlas (TCGA) and Genome Tissue Expression (GTEx) databases to analyze eIF4A1 expression in PDAC tissues and further validated the findings with a microarray containing 53 PDAC samples. Expression regulation and pharmacological inhibition of eIF4A1 and c-Myc were performed to determine their role in migration, invasion, and metastasis in pancreatic Cancer cells in vitro and in vivo.

Results: Elevated eIF4A1 expression was positively correlated with lymph node infiltration, tumor size, and indicated a poor prognosis. eIF4A1 decreased E-cadherin expression through the c-Myc/miR-9 axis. Loss of eIF4A1 and c-Myc decreased the EMT and metastasis capabilities of pancreatic Cancer cells, whereas upregulation of eIF4A1 attenuated the inhibition of EMT and metastasis induced by c-Myc downregulation. Treatment with the eIF4A1 inhibitor rocaglamide (RocA) or the c-Myc Inhibitor Mycro3 either alone or in combination significantly decreased the expression level of EMT markers in pancreatic Cancer cells in vitro. However, the efficiency and safety of RocA alone were not inferior to those of the combination treatment in vivo.

Conclusion: Overexpression of eIF4A1 downregulated E-cadherin expression through the c-Myc/miR-9 axis, which promoted EMT and metastasis of pancreatic Cancer cells. Despite the potential feedback loop between eIF4A1 and c-Myc, RocA monotherapy is a promising treatment inhibiting eIF4A1-induced PDAC metastasis.