Tumor-derived exosomes differentially modulate the adenosine pathway in human resting vs activated regulatory T cells (Treg) (TUM4P.927)

Abstract

Abstract Tumor-derived exosomes (TEX) suppress functions of human immune cells, while up-regulating functions of others. Here, we show that TEX isolated from supernatants of human cultured tumor cells or plasma of cancer patients differentially modify gene and protein expression of CD39, CD73 and adenosine receptors (ADORs) in Treg, influencing production of suppressive nucleosides. Resting or pre-activated (anti-CD3/CD28 Abs) CD4+CD39+ Treg were co-incubated overnight with TEX. Cellular mRNA was analyzed by qRT-PCR for expression of CD39, CD73, A1R, A2aR, A2bR and A3R genes. Protein expression was studied by flow cytometry and western blots. Nucleoside production by Treg ± TEX in the presence of 20µM ATP was measured by mass spectrometry. In resting Treg + TEX, mRNA expression of CD39/CD73 and ADORs was reduced relative to no TEX baseline (>1 log) except for A1R mRNA expression which was elevated (> 3 logs). CD39 protein expression was up-regulated, suggesting enhanced translation and signaling via A1R. Treg + TEX + ATP produced inosine only (7900ng/mL) and no 5’-AMP or ADO. In activated Treg +TEX, CD39/CD73 mRNA expression and protein levels were elevated (p< 0.05) as was mRNA expression for all ADORs, especially A2aR, and ADO was produced. Thus, TEX differentially regulated gene expression and protein levels of the ADO pathway components in resting vs activated Treg. The TEX-induced shift from inosine to ADO production implies changes in Treg-mediated immunosuppression.