CLDN5 and neoplasm: Brains from non-tumour-bearing mice not receiving NBPs were compared to non-diseased adult human brain, and both species showed prominent HER3 coinciding with brain vasculature (claudin-5), whereas HER3 was nearly undetectable in the extravascular brain parenchyma (Fig. 3g,h and Supplementary Fig. 24), suggesting that HER3 inherently associates with the brain vasculature.