Abstract 110: Inhibition Of VEGF Signaling Prevents KRAS ^G12V -induced Brain Arteriovenous Malformations

Introduction: Brain arteriovenous malformations (bAVMs) are a major risk factor of cerebral hemorrhages in young patients. Recently, somatic KRAS mutation has identified ~60% of human bAVMs, and we confirmed the causal role of endothelial KRAS G12V mutation in bAVM development using a mouse model. Excessive uncontrolled angiogenesis is associated with the abnormal vascular outgrowth in bAVMs. While abnormal VEGF signaling is involved in pathologic angiogenesis, the role in mutant KRAS-induced bAVMs has not been studied. Here, we hypothesized that KRAS mutation induces bAVMs via activation of VEGF signaling, and tested if VEGF inhibition prevents KRAS G12V -induced bAVM development. Methods: We induced bAVMs in mice by systemic injection of AAV-BR1 carrying KRAS G12V mutation (KRAS G12V mice). To determine the effect of KRAS mutation on VEGF signaling, we tested the expression of VEGF-A and VEGFR2 in KRAS G12V -induced bAVMs in vivo and cultured mouse endothelial cells (ECs) overexpressing KRAS G12V in vitro . Furthermore, we performed the tube formation assay to test angiogenesis by KRAS G12V mutation in the cultured EC. Finally, we treated VEGFR2 inhibitor (SU5416) in the KRAS G12V mice and measured the bAVM size and numbers in the latex-casted brains. Results: We found that the expression of VEGF-A, VEGFR2, and phospho(p)-VEGFR2 were significantly increased in KRAS G12V -induced bAVMs in mice. We also found that KRAS G12V transfection up-regulates expression of VEGF-A, VEGFR2, and p-VEGFR2, and increased tube formation in cultured ECs. Finally, we confirmed that SU5416 treatment significantly reduced the numbers and size of bAVMs in KRAS G12V mice. Conclusions: Our data show that endogenous VEGF signaling is activated by KRAS mutation. The VEGF inhibition study suggests that the endogenously activated VEGF signaling would be essential to mediate the mutant KRAS-induced bAVM development.