Neuropilin-1, an immune checkpoint for controlling tumor-specific CD8 T-cell functions whose blockade improves anti-PD-1 immunotherapy

Abstract

Abstract Neuropilin-1 (Nrp-1) has been defined as a marker of murine CD4+Foxp3+ regulatory T (Treg) cells and a subset of human CD4+ Treg cells. It is also expressed by a subpopulation of CD8+ T cells infiltrating some human solid tumors. However, little is known about its contribution to regulation of tumor-specific CD8 T-cell functions. We show that Nrp-1 defines a subset of CD8+ T cells displaying PD-1high (PD-1hi) status and infiltrating human non-small cell lung cancer (NSCLC). Using a human cytotoxic T lymphocyte (CTL) clone model, we show that the interaction of Nrp-1 with its ligand semaphorin-3A (Sema-3A), secreted by autologous NSCLC cells, inhibits both CTL migration and tumor-specific lytic function. In vivo experiments revealed that this Nrp-1+PD-1hi CD8+ tumor-infiltrating T lymphocyte (TIL) subset is also found in engrafted B16F10 mouse melanoma, and is enriched with tumor-specific T cells exhibiting an exhausted state, with co-expression of Tim-3, LAG-3 and CTLA-4 inhibitory receptors. Functionally, anti-Nrp-1 neutralizing antibodies increase the migratory capacity of Nrp+PD-1hi CD8+ TIL toward autologous cancer cells and enhance their specific cytotoxic activity ex vivo. Remarkably, in vivo immunotherapeutic blockade of Nrp-1 results in control of tumor growth, with a parallel increase in tumor infiltration by CD8+ TIL and enhanced proliferative and cytotoxic potential. This blockade is cumulative with anti-PD-1 treatment in improving tumor regression. Thus, Nrp-1 appears to be a novel immune checkpoint target on CD8+ tumor-specific T cells for combined antibody-based cancer immunotherapies. More recent advances on Nrp-1 expression regulation and functions in CD4+ and CD8+ T cells will be presented.