PKM and metastatic neoplasm: Among the proteins we found significantly elevated only in metastatic tumors (Table 3), cathepsin Z and pyruvate kinase PKM were reported differentially expressed in vitro in UM liver metastases [39] and cathepsin Z, cathepsin B, cathepsin D, macrophage-capping protein, melanocyte protein PMEL were elevated in the secretome of primary UM cell lines [38].