Angiogenic switching in cerebral cavernous malformations driven by MAP3K3-PIK3CA synergy.

Cerebral cavernous malformations are common vascular anomalies in the central nervous system that predispose individuals to seizures and hemorrhagic stroke. Familial forms are linked to germline loss-of-function mutations in CCM1-3, and sporadic lesions frequently harbor somatic gain-of-function mutations in MAP3K3 and PIK3CA. However, the mechanisms by which these somatic mutations drive lesion development remain incompletely understood, and no medical therapies are currently available. Here, we investigated the cooperative effects of MAP3K3I441M and PIK3CAH1047R mutations using transgenic neonatal and adult mouse model, supported by histology, micro-CT, bulk and single-cell RNA sequencing, and human cerebral cavernous malformations samples. MAP3K3 I441M activated inflammatory and angiogenic transcriptional programs in brain endothelial cells, whereas PIK3CAH1047R enhanced cell cycle and DNA replication pathways. Notably, MAP3K3I441M and PIK3CAH1047R double mutations synergistically amplified PI3K-AKT-mTOR signaling, inducing an "angiogenic switch" reminiscent of tumor neovascularization. This interaction promoted endothelial angiogenesis and lesion development in mouse brains. Transcriptomic analyses of human cerebral cavernous malformations confirmed enrichment of angiogenesis-related gene signatures in double mutations-related lesions. Treatment with the PI3Kα-selective inhibitor alpelisib suppressed lesion formation and reversed pro-angiogenic signaling in both mouse models and patient-derived cerebral cavernous malformations organoids. These findings uncover a convergent mechanism involving MAPK and PI3K pathway activation in cerebral cavernous malformations pathogenesis and demonstrate that PI3Kα inhibition may offer a viable therapeutic strategy for a disease that currently lacks effective pharmacological treatment.