Combined effect of anti-BAG3 and anti-PD-1 treatment on macrophage infiltrate, CD8+ T cell number and tumour growth in pancreatic cancer

We read with great interest the article by Zhang et al 1 showing that CD8+ cell infiltration in pancreatic tumours can be enhanced by depletion of myeloid cells (CD11b+ macrophages and myeloid-derived suppressor cells) and that the depletion of CD11b+ cells resulted in decreased PD-L1 expression on cancer cells thus impairing the triggering of the inhibitory receptor PD-1 on T cells.1 Recruitment and activation of CD8+ lymphocytes in tumours are suppressed by mechanisms only partially understood and rescuing CD8+ cell infiltrate in tumours is one of the objectives of immunotherapies.1 2 Tumour-associated macrophages (TAMs) play a crucial role in the relation between tumour cells and their environment.3 Here, we confirm the interplay between macrophages and CD8+ cells in pancreatic cancer and identify a potential way to exploit this enhancing effect of anti-PD-1 treatment. Indeed, we show that reduction of macrophage infiltrate, through treatment with an anti-Bcl-2-Associated athanoGene 3 (BAG3) antibody,4 results in increased number of CD8+ cells in pancreatic tumours in a murine model. …