The assessed melanoma lines showed an expression of various proteases including MMP-2, Cathepsin B and Cathepsin D. MMPs -3 and -9, which are commonly correlated with melanoma metastases, were not detected in melanoma conditioned media, though these have conflicting roles in melanoma progression, with data that suggest both pro and anti-tumour activity [30,59,60,61]. Here, CTSB is linked to melanoma.