CTSB and melanoma: By treating A-07, D-12, and T-22 human melanoma cells with media buffered to pH 6.8, several proteins such as MMP-2, MMP-9, cathepsin B, cathepsin L, VEGF-A, and IL-8 are upregulated and contribute to increased experimental lung metastasis post tail vein injections in athymic nude mice (Rofstad et al., 2006).