Adenovirus-mediated eukaryotic initiation factor 4E binding protein-1 in combination with rapamycin inhibits tumor growth of pancreatic ductal adenocarcinoma in vivo

Abstract

Over-expression of eIF4E indicates a poor prognosis in different tumors. In the present study, we investigated the frequency of eIF4E, 4E-BP1 and phosphorylated 4E-BP1 expression in PDAC cell lines, gastric carcinoma (GC) cell lines and human embryonic pancreatic cells, as well as gene therapy using translation repressor gene 4E-BP1 in combination with the mTOR inhibitor rapamycin. We also assessed the significance of eIF4E expression in 80 PDAC cases. Combination therapy of adenovirus vector-delivered 4E-BP1 gene and rapamycin was administered to determine their growth inhibition effect in vitro and in vivo in mice. Our study revealed that all PDAC cell lines, GC cell lines and human embryonic pancreas-derived cells expressed the 25-kDa eIF4E protein (MIAPaca-2 cells also expressed the 13-kDa protein 4E-BP1). The 80 PDAC specimens showed a heterogeneous pattern of eIF4E staining. No significant correlation between eIF4E expression and TNM classification was found. Adenovirus vectors Ad-4E-BP1 and Ad-GFP efficiently showed transgenic expression with hyperphosphorylation of 4E-BP1; however, insignificant growth inhibition of the PDAC and GC cell lines was observed. Combination therapy with rapamycin significantly inhibited proliferation and tumor growth in vitro as well as in vivo. Therefore, combination of Ad 4E-BP1 and rapamycin may be a more effective adjuvant therapy.