Abstract
INTRODUCTION: High levels of extracellular adenosine, highly abundant in the tumor microenvironment, promote immune suppression mainly through the A2AR expressed by tumor-infiltrating immune cells. Given the importance of tumor-infiltrating B and plasma cells (PCs) in antitumor responses, we investigated the effect of A2AR on human B cells. METHODS: We performed quantitative mass spectrometry imaging followed by GeoMx analysis on 10 tumor samples. Immunohistochemistry, multiplex immunofluorescence and scRNA-seq were used to assess A2AR expression on tumor and tonsillar B cells. In vitro differentiated B cells and sorted tonsillar B cells were stimulated in the presence of the A2AR agonist CGS-21680 with or without the A2AR antagonist inupadenant, and analysed by flow cytometry, LegendPLEX and scRNA-seq. The in vivo effect of inupadenant was assessed using Visium on tumor biopsies from five cancer patients. RESULTS: The frequency of PCs was the most negatively affected by adenosine among the immune cells present in the tumor microenvironment. Furthermore, both tonsillar and tumor-associated B cells, including germinal center (GC)-like B cells, PCs and plasma blasts, collectively referred to as antibody-secreting cells (ASCs), expressed high levels of A2AR. Triggering of A2AR inhibited B cell maturation into ASCs and immunoglobulin production in vitro, and impaired upregulation of PC genes upon stimulation. These effects were restored by inupadenant (EOS100850), a potent and highly selective small molecule A2AR antagonist. Spatial transcriptomics analysis of tumor biopsies from patients treated with inupadenant revealed that ASCs specifically increased in tertiary lymphoid structures. DISCUSSION: Altogether, these data demonstrate that A2AR plays a key role in adenosine-mediated inhibition of B cell maturation toward ASCs through a B cell-intrinsic mechanism, and that this effect is fully reverted by inupadenant.