Upon incubating chest and ear skin extracts in pH 5.5 buffer, which measures only cysteinyl cathepsins [30], with fluorogenic elastin and collagen, two common matrix protein substrates for cathepsins S, L, K, and B, we found that tumor tissue extracts from both the chest skin and ear skin from Cstc−/− mice had significantly higher elastase (Figure 6A) and collagenase (Figure 6B) activities than those from Cstc+/+ mice. This evidence concerns the gene ELN and neoplasm.