CTSK and neoplasm: mRNA analysis demonstrated high levels of expression of the melanocyte genes Pmel, Tyrp1, Ctsk (encoding CATHEPSIN K) and Mlana (also known as Mart1, encoding the MART-1 antigen) in allografts compared to normal kidney (Supplementary Fig. 3g) and western blotting confirmed that allograft tumours expressed both PMEL and CATHEPSIN K (Supplementary Fig. 3h, i).