PURPOSE: Arteriovenous malformation (AVM) is a fast-flow vascular anomaly characterized by abnormal arterial to venous shunts. Extracranial AVMs contain a somatic mutation in MAP2K1. The purpose of this study was to: (1) create a stable MAP2K1 mutant endothelial cell (EC) line, (2) determine how the MAP2K1 mutation affects EC behavior, and (3) create in-vitro and in-vivo models to test pharmacotherapy.
METHODS: Utilizing CRISPR-Cas9, the MAP2K1 p.K57N mutation was introduced into immortalized arterial endothelial cells (teloHAECs). Elevated phosphorylated ERK (P-ERK) was tested using Western Blot. Bulk-RNAseq and differential gene expression analysis was conducted comparing mutant and control cells. Cells were injected into immunodeficient mice and implant phenotype was characterized. Models were treated with a MEK inhibitor and assessed.
RESULTS: Increased P-ERK was detected in mutant cells confirming the activating effects of the MAP2K1 mutation. Differentially expressed vasculogenic, cellular adhesion, and inflammatory genes between mutant and control cell lines were identified, including increased expression of angiopoietin-2. Murine implants with mutant ECs displayed malformed and dilated vasculature. MEK inhibition prevented the transcriptomic and histologic effects of the MAP2K1 mutation, including reduction in angiopoietin-2 production.
CONCLUSION: The MAP2K1 mutation in our model activates RAS/MEK signaling, stimulates vasculogenic gene expression, and forms abnormal vascularized lesions in-vivo. These models provide insight into the pathophysiology of human AVM and support the efficacy of MEK inhibitors for the treatment of AVM.
