VGB3 Induces Apoptosis by Inhibiting Phosphorylation of NF-κB p65 at Serine 536 in the Human Umbilical Vein Endothelial Cells

Background and objectives: Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) inhibition results in an increase in apoptosis. It has been demonstrated that NF-κB subunit p65 phosphorylation at the IκB kinase phosphorylation site serine 536 (Ser536) is essential for the NF-κB nuclear translocation and activation. Therefore, NF-κB can be downregulated by suppressing its phosphorylation. The vascular endothelial growth factor receptor-2 (VEGFR-2) suppression could result in apoptosis induction. Therefore, targeting these pathways via VEGFR-2 inhibitors might have therapeutic potential for cancer treatment. It has been indicated that an antagonist peptide of VEGF, referred to as VGB3, could neutralize and recognize VEGFR2 in the tumoral and endothelial cells. This study aimed to induce apoptosis in human umbilical vein endothelial cells (HUVEC) cells through the inhibition of these signaling pathways. Methods: Effects of different concentrations of VGB3 (1-200 ng/ml) were evaluated on the viability of HUVEC  cells using MTT assay. In addition, downstream signaling pathways in HUVE cells were evaluated through quantitative assessment of protein expression via western blotting. Results: The results demonstrated that VGB3 treatment inhibited the growth of HUVEC cells. Moreover, Bcl-2 was decreased in the cells treated with the VGB3 compared to the control. Furthermore, VGB3 significantly enhanced the cleaved-caspase7 levels, which is an indicator of apoptosis progression. Altogether, VGB3 enhanced apoptosis in HUVEC cells. Conclusion: Our results indicate that the peptide might be a potential candidate for antitumor therapy via inhibiting the NF-κB pathway.