DESCRIPTION

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.

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