CTSD and melanoma: In the previous work, we used the native proteins extracted by a dual-lectin column from the melanoma cell line as bait to detect the presence of autoantibodies in the sera of melanoma patients, identifying 5 antigens including 75 kD glucose-regulated protein (GRP75), 94 kD glucose-regulated protein (GRP94), acid ceramidase (ASAH1), cathepsin D (CTSD), and lactate dehydrogenase B (LDHB), and we investigated the humoral response against the recombinant proteins using a larger sample set of 79 melanoma patients (Figure 1).