These observations are in the line with our previous studies, which verified that [68Ga]DOTA-Siglec-9 is specific for VAP-1 using three different approaches: 1) cell-binding assays using Chinese Hamster Ovary (CHO) cells stably transfected with human VAP-1 and CHO cells transfected with vector only; 2) in vivo biodistribution analysis in human VAP-1 transgenic mice and VAP-1 knockout mice; and 3) in vivo competition with excess of unlabeled Siglec-9 peptide in a mouse model of melanoma expressing VAP-1 in the vasculature. This evidence concerns the gene AOC3 and melanoma.