Tumor Necrosis Factor Superfamily-15 Facilitates Lymphangiogenesis via Upregulation of VEGFR3 Gene Expression in Lymphatic Endothelial Cells

Lymphangiogenesis is essential in embryonic development but is rare in adults. It occurs, however, in many disease conditions including cancers. Vascular endothelial growth factor-C/D (VEGF-C/D) and VEGF receptor-3 (VEGFR3) play a critical role in the regulation of lymphangiogenesis. We investigated how the VEGF-C/VEGFR3 signaling system is regulated by tumor necrosis factor superfamily-15 (TNFSF15), an endothelium-derived cytokine. We report here that TNFSF15, which is known to induce apoptosis in vascular endothelial cells, can promote lymphatic endothelial cell (LEC) growth and migration, stimulate lymphangiogenesis, and facilitate lymphatic circulation. Treatment of mouse LEC with TNFSF15 results in upregulation of VEGFR3 expression; this can be inhibited by gene-silencing of death domain–containing receptor-3 (DR3; TNFRSF25), a cell surface receptor for TNFSF15, with siRNA, or by blocking TNFSF15-DR3 interaction with a TNFSF15 neutralizing antibody 4-3H. Additionally, TNFSF15/DR3 signaling pathways in LEC include activation of NF-κB. TNFSF15-overexpressing transgenic mice exhibit a marked enhancement of lymph drainage; this is confirmed by treatment of wild type mice with intraperitoneal injection of recombinant TNFSF15. Moreover, systemic treatment of pregnant TNFSF15 transgenic mice with 4-3H leads to inhibition of embryonic lymphangiogenesis. Our data indicate that TNFSF15, a cytokine produced largely by endothelial cells, facilitates lymphangiogenesis by upregulating VEGFR3 gene expression in LEC, contributing to the maintenance of the homeostasis of the circulatory system. This finding also suggests that TNFSF15 be of potential value as a therapeutic tool for the treatment of lymphedema.