Insights into the anticancer mechanisms of interleukin-15 from engineered cytokine therapies.

Innovative approaches in the field of cytokine engineering are revolutionizing the cancer therapeutic landscape. The IL-15 cytokine is particularly enticing as a cancer immunotherapy due to its natural propensity for stimulating the proliferation and activation of NK and CD8+ T cells. In a recent IL-15 engineering approach, the cytokine was conjugated to polyethylene glycol, and the resulting molecule (NKTR-255) exhibited potent antitumor activities. In this issue of the JCI, Robinson et al. mechanistically explored NKTR-255 and compared its immune profile to that of the unconjugated IL-15 cytokine. The authors found that NKTR-255 employs distinct activities on NK compared with CD8+ T cells. NKTR-255 signaling also showed less dependence on the expression of the IL-15 receptor-α (IL-15Rα) chain compared with unconjugated IL-15. Collectively, these findings will advance IL-15-based clinical therapies and, more generally, benefit the field of cancer immunotherapy.