CD137 Costimulation Counteracts TGFβ Inhibition of NK-cell Antitumor Function

Enhancing natural killer (NK) cell-based cancer immunotherapy by overcoming immunosuppression is an area of intensive research. Here, we have demonstrated that the anti-CD137 agonist urelumab can overcome TGFb-mediated inhibition of human NK-cell proliferation and antitumor function. Transcriptomic, immunophenotypic, and functional analyses showed that CD137 costimulation modified the transcriptional program induced by TGFb on human NK cells by rescuing their proliferation in response to IL2, preserving their expression of activating receptors (NKG2D) and effector molecules (granzyme B, IFN gamma) while allowing the acquisition of tumor-homing/retention features (CXCR3, CD103). Activated NK cells cultured in the presence of TGFb1 and CD137 agonist recovered CCL5 and IFN gamma secretion and showed enhanced direct and antibody-dependent cytotoxicity upon restimulation with cancer cells. Trastuzumab treatment of fresh breast carcinoma-derived multicellular cultures induced CD137 expression on tumor-infiltrating CD16(+) NK cells, enabling the action of urelumab, which fostered tumor-infiltrating NK cells and recapitulated the enhancement of CCL5 and IFN gamma production. Bioinformatic analysis pointed to IFNG as the driver of the association between NK cells and clinical response to trastuzumab in patients withHER2-positive primary breast cancer, highlighting the translational relevance of the CD137 costimulatory axis for enhancing IFN gamma production. Our data reveals CD137 as a targetable checkpoint for overturning TGF beta constraints on NK-cell antitumor responses.

Automated summary

This study demonstrates that CD137 costimulation can overcome TGFβ-mediated inhibition of NK cell antitumor responses, promoting NK cell proliferation and function, as well as enhancing direct and antibody-dependent cytotoxicity against tumors.