In particular, metastatic renal cell carcinoma (RCC) is frequently associated with elevated levels of IL-6, which have been reported to correlate with metastatic progression, poor prognosis, shorter survival (Blay et al, 1992; Negrier et al, 2004), as well as poor response (Fumagalli et al, 1999) and high toxicity (Capuron et al, 2001) to IL-2 therapy. This evidence concerns the gene IL6 and renal cell carcinoma.