Antiangiogenic Activity of rTRAIL is Potentiated by Sflt-1, a VEGF Trap

Objective: Anti-angiogenesis and pro-apoptosis are the two processes which are strategically used to target tumors. The soluble form of VEGF receptor 1 (Flt-1) is a modulator of VEGF activity and could be useful as a trap to intrinsically sequester VEGF in tumor cells. In the present study, we have investigated the role of rTRAIL in inhibiting VEGF-mediated angiogenesis and its synergistic potentiation by sFlt-1.

Methods: We have expressed human recombinant TRAIL, to study its role in anti-angiogenesis and a 2-domain active variant of sFlt-1 by bacterial expression to be used as a trap for VEGF. 3[H] thymidine incorporation assay was used to confirm the inhibitory activity of sFlt-1 and/or rTRAIL on cell proliferation. The synergistic anti-migratory and anti-angiogenic activity of sFlt-1 and rTRAIL were assessed using endothelial cell wound healing and tube formation assay in-vitro and by rat corneal micropocket assay in-vivo.

Results: Inhibition of cell proliferation was evident in sFlt-1 and rTRAIL treated cells in a dose -dependent manner with more than 60% reduction in proliferation rate as compared to the tumor cells treated with sFlt-1 and rTRAIL alone. Furthermore, the anti-metastatic and anti-angiogenic activity of sFlt-1 and rTRAIL in combination was evident in endothelial wound healing and tube formation with a significant reduction in the number of cells migrated into the wounded area and the number of honey comb-like structures with the length of the tubes formed to mimic blood vessel formation in-vitro respectively. The in-vivo corneal micropocket assay confirmed the anti-angiogenic effect of sFlt-1 and rTRAIL in combination.

Conclusion: The synergistic role of sFlt-1 and rTRAIL as the potential inhibitors of VEGF- mediated angiogenesis could be therapeutically exploited.