RNA-seq studies in dabrafenib treated endothelial cells

Cerebral Cavernous Malformations (CCM) constitute the second most common type of intracranial vascular malformations. Cavernomas arise due to somatic or autosomal dominant inherited loss-of-function mutations in KRIT1 (CCM1), CCM2, or PDCD10 (CCM3), forming fragile mulberry-like malformed blood vessel structures, which are prone to leak and break. Treatment is limited to surgical removal of solitary cavernomas. As patients often present with multiple lesions, there is an urgent need to develop non-invasive therapeutic strategies. We performed a high throughput screen of 5200 bioactive molecules followed by image analysis on Ccm3-knockout endothelial cells and discovered that the FDA-EMA-approved BRAF inhibitor dabrafenib, effectively restored cell-cell junctions and vascular barrier properties of CCM-deficient endothelial cells. The potential translatability of dabrafenib was tested in vivo, where it reduced cerebral lesion burden and suppressed lesion permeability, reducing perivascular plasma protein depositions. Dabrafenib also rescued abnormal structural defects present in the developing retina vasculature. Mechanistically, dabrafenib targeted extracellular regulated kinase (ERK)5-Krüppel like factor (KLF)2/4 signaling pathway and suppressed F-actin stress fiber formation, two potentially independent and central molecular processes involved in CCM pathology. Dabrafenib is a kinase inhibitor indicated for the treatment of tumors with BRAF V600E mutations. However, silencing of BRAF did not interfere with dabrafenib-induced KLF2/4 inhibition and restoration of cell-cell junctions, suggesting that its dual therapeutic outcome is independent of BRAF pathway inhibition. In conclusion, dabrafenib is a small molecular weight compound with marked inhibitory effects on cavernoma pathogenesis suggesting that CCMs could be treated with dabrafenib to block cavernoma growth and vascular leakage.