Semaphorin 3A causes immune suppression by inducing cytoskeletal paralysis in tumour-specific CD8+ T cells

Abstract

Semaphorin-3A (SEMA3A) functions as a chemorepulsive signal during development and can affect T cells by altering their filamentous actin (F-actin) cytoskeleton. The exact extent of these effects on tumour-specific T cells are not completely understood. Here we demonstrate that Neuropilin-1 (NRP1) and Plexin-A1 and Plexin-A4 are upregulated on stimulated CD8⁺ T cells, allowing tumour-derived SEMA3A to inhibit T cell migration and assembly of the immunological synapse. Deletion of NRP1 in both CD4⁺ and CD8⁺ T cells enhance CD8⁺ T-cell infiltration into tumours and restricted tumour growth in animal models. Conversely, over-expression of SEMA3A inhibit CD8⁺ T-cell infiltration. We further show that SEMA3A affects CD8⁺ T cell F-actin, leading to inhibition of immune synapse formation and motility. Examining a clear cell renal cell carcinoma patient cohort, we find that SEMA3A expression is associated with reduced survival, and that T-cells appear trapped in SEMA3A rich regions. Our study establishes SEMA3A as an inhibitor of effector CD8⁺ T cell tumour infiltration, suggesting that blocking NRP1 could improve T cell function in tumours.

Interactions between Semaphorin-3A (SEMA3A) and Neuropilin-1 (NRP1) and Plexin-A1 and Plexin-A4 have been shown to affect T cell development. Here the authors investigate how these interactions affect CD8⁺ T cells in tumour immunity, showing that NRP-1, Plexin-A1 and Plexin-A4 are upregulated on T cells allowing tumour derived SEMA3A to inhibit CD8⁺ T cell migration and function.