In Vivo Antitumor Activity of a Recombinant IL7/IL15 Hybrid Cytokine in Mice.

Both IL7 and IL15 have become important candidate immunomodulators for cancer treatment. However, IL7 or IL15 used alone suffers from shortcomings, such as short serum half-life and limited antitumor effect. We have cloned and expressed a recombinant (r) IL7/IL15 fusion protein in which IL7 and IL15 are linked by a flexible linker. We then compared the antitumor effect of rIL7/IL15 with the individual factors rIL7 and/or rIL15. We show here that rIL7/IL15 has a higher antitumor activity than the combination of the individual factors in both murine B16F10 melanoma and CT-26 colon cancer models. This was associated with a significant increase in tumor infiltration of T cells, DCs, and NK cells and a decrease in regulatory T cells (Tregs). In addition, rIL7/IL15-treated DCs had higher expression of costimulatory molecules CD80 and CD86. The higher antitumor activity of rIL7/IL15 is likely due to its longer in vivo half-life and different effects on immune cells. Our results suggest that rIL7/IL15 may offer a new tool to enhance antitumor immunity and treat cancer. Mol Cancer Ther; 15(10); 2413-21. ©2016 AACR. ©2016 American Association for Cancer Research.