In line with this study, laser choroidal neovascularisation volume was reduced in H4R-KO mice.47 On the other side, other reports demonstrated that H4R may negatively regulate angiogenesis, since H4R agonists attenuate angiogenesis in Leydig tumours48 and melanoma.44 The study of the exact role of H4R in tumour angiogenesis is still unexplored and deserves further investigation. This evidence concerns the gene HRH4 and melanoma.