IL-15Ralpha may be secreted as a functional soluble molecule (s-IL-15Ralpha) and could behave as antagonist or agonist by forming a complex with IL-15 [19-21], also, it has been described that soluble IL-15Ralpha could bind to membrane bound IL-15 to induce a reverse signaling mechanism up-regulating the production of IL-6, IL-8, and TNFalpha by human monocytes and in the cancer cell line PC-3 [22,23]. This evidence concerns the gene IL15 and cancer.