In contrast to its inhibitory effects on many cells, IL10 activates CD8+ tumor-infiltrating lymphocytes (TIL) and enhances their antitumor activity. However, CD8+ TILs do not routinely express IL10, as autocrine complement C3 inhibits IL10 production through complement receptors C3aR and C5aR. CD8+ TILs from C3-deficient mice, however, express IL10 and exhibit enhanced effector function. C3-deficient mice are resistant to tumor development in a T-cell– and IL10-dependent manner; human TILs expanded with IL2 plus IL10 increase the killing of primary tumors in vitro compared with IL2-treated TILs. Complement-mediated inhibition of antitumor immunity is independent of the programmed death 1/programmed death ligand 1 (PD-1/PD-L1) immune checkpoint pathway. Our findings suggest that complement receptors C3aR and C5aR expressed on CD8+ TILs represent a novel class of immune checkpoints that could be targeted for tumor immunotherapy. Moreover, incorporation of IL10 in the expansion of TILs and in gene-engineered T cells for adoptive cell therapy enhances their antitumor efficacy.
SIGNIFICANCE: Our data suggest novel strategies to enhance immunotherapies: a combined blockade of complement signaling by antagonists to C3aR, C5aR, and anti–PD-1 to enhance anti–PD-1 efficacy; a targeted IL10 delivery to CD8+ TILs using anti–PD-1–IL10 or anti-CTLA4–IL10 fusion proteins; and the addition of IL10 in TIL expansion for adoptive cellular therapy. Cancer Discov; 6(9); 1–11. ©2016 AACR.
Note: Supplementary data for this article are available at Cancer Discovery Online (http://cancerdiscovery.aacrjournals.org/).
- Received November 30, 2015.
- Revision received June 6, 2016.
- Accepted June 6, 2016.
- ©2016 American Association for Cancer Research.