Intratumoral TIGIT blockade augments antitumor responses and bypasses increased functionality of peripheral TIGIT+ NK cells in mouse and human models of bone and soft tissue sarcoma.

backgroundTIGIT (T cell immunoreceptor with Ig and ITIM domains) has emerged as a key exhaustion marker of intratumoral natural killer (NK) cells, but results from clinical trials with TIGIT blockade have been largely negative. Recent data have suggested that a subset of TIGIT-expressing NK cells can show increased functionality. We hypothesized that there are differences in function between peripheral and intratumoral TIGIT-expressing NK cells in patients with sarcoma and preclinical sarcoma models, which undermine the efficacy of systemic TIGIT blockade. We sought to investigate differences in TIGIT+ NK cells using systemic versus intratumoral TIGIT-blocking strategies.

methodsPeripheral and intratumoral NK cells were analyzed from human patients and mice with osteosarcoma (OSA) and soft tissue sarcoma (STS). NK phenotype and function were evaluated using flow cytometry, immunohistochemistry, live-cell imaging, and RNA sequencing. Mouse antimouse-IgG1 TIGIT blockade was delivered systemically or intratumorally in flank models of OSA (K7M2) and STS (MCA-205). Clinical and genomic data were evaluated using Caris CODEai. Expression of the TIGIT ligand CD155 on myeloid and tumor cells was evaluated as a marker of TIGIT function.

resultsUsing multiple readouts, TIGIT+ NK cells from the spleen of tumor-bearing mice or peripheral blood of patients with STS and OSA showed increased functionality compared with TIGIT- NK, while TIGIT+ NK cells from the sarcoma tumor microenvironment (TME) of mice and humans were dysfunctional, with upregulated senescence and inhibitory gene pathways. Systemic TIGIT blockade reinvigorated intratumoral NK cell function but inhibited peripheral NK cells, while intratumoral administration of TIGIT blockade significantly delayed tumor growth and prolonged survival with partial reversal of NK dysfunction in the TME. Clinical and genomic data demonstrated that more NK cell infiltration in human STS was prognostic of improved overall survival only when intratumoral CD155 expression was low, indicating that elevated CD155 expression is correlated with greater NK cell dysfunction.

conclusionsWe identified a cross-species role of TIGIT expression dependent on location, where peripheral TIGIT+ NK cells showed evidence of enhanced functionality, while intratumoral TIGIT+ NK cells were dysfunctional. These differences impacted antitumor effects of TIGIT blockade, suggesting that intratumoral delivery of TIGIT blockade may be a novel translational strategy in high-risk bone and soft tissue sarcomas.