IL15RA and neoplasm: Therefore, the role of intratumoral and circulating IL-15 is complex and depends on several factors, such as the type of IL-15 produced, the IL-15-Rα chain isoforms involved in sIL-15/IL-15Rα, the presence of functional IL-15 receptors on tumor cells, as well as their response to stromal and endogenous IL-15.