Ryan Watkins, Univeristy of Utah
The lymphatic system is responsible for controlling systemic fluid buildup. Lymphangiogenesis is a dynamic process involving sprouting and maintaining new lymphatic vasculature. Vascular endothelial growth factor C (VEGF-C) is known as a key growth factor through VEGF receptor 2 and 3 (VEGFR2 and VEGFR3). Interestingly, the cornea expresses VEGF-C but is alymphatic. We found that the soluble isoform of VEGFR3, which lacks tyrosine kinase domains, is responsible for the alymphatic nature of the cornea by sequestering endogenous VEGF-C. Although soluble VEGFR3 or soluble VEGFR2 can be useful for inhibition of VEGF-C derived lymphangiogenesis, they also bind VEGF-A. Inhibition of VEGF-A suppresses blood vessel formation, damaging tissue and creating additional side effects. The development of a new anti-lymphangiogenic drug, that only blocks VEGF-C, has many implications: preventing tumor metastasis and reducing rejection rates of tissue and organ transplants. VEGF-C mainly binds to VEGFR3 domain 2 and VEGFR2 domain 3. To develop an anti-lymphangiogenic drug that specifically binds VEGF-C the binding domains were inserted into a vector that produces a recombinant protein (VEGF-C trap) that sequesters VEGF-C, suppressing lymphangiogenesis. Mice in a cornea transplantation model were treated with VEGF-C trap. After 8 weeks, 60% of the treated cornea survived (no rejection) compared to 10% in the empty vector control group. A 60% transplant survival rate is one of the highest rates compared to other single treatment methods. Blood and lymph vessel area was calculated and showed a decrease in lymph vasculature but not blood vessel. Suggesting only VEGF-C activity was affected. In a tumor metastasis model, nude mice will be injected subcutaneously with cultured MCF-7 cells which have been transfected with VEGF-C trap or an empty vector. We expect to see a decrease of lymphatic vasculature in the mice injected with MCF-7 cells containing the VEGF-C trap and ultimately less metastasis.