CTSD and renal cell carcinoma: In this pilot study, we have shown that proteomic analysis of CM from renal cancer cell lines, as described in other diseases (Xue et al, 2008), may result in the identification of potential biomarkers such as cathepsin D. Furthermore, although samples from 149 patients with RCC were included, this represents a relatively small validation study with only moderate statistical power for a potential marker with this magnitude of HR, and yet we were able to show the novel finding of an association between urinary cathepsin D in RCC and survival, which has potential clinical application.