Tumor cell-derived exosomes (TEX) suppress functions of immune cells. Here, changes in the gene profiles of primary human T lymphocytes exposed in vitro to exosomes were evaluated. CD4(+) Tconv, CD8(+) T or CD4(+) CD39(+) Treg were isolated from normal donors’ peripheral blood and co-incubated with TEX or exosomes isolated from supernatants of cultured dendritic cells (DEX). Expression levels of 24-27 immune response-related genes in these T cells were quantified by qRT-PCR. In activated T cells, TEX and DEX up-regulated mRNA expression levels of multiple genes. Multifactorial data analysis of ΔCt values identified T cell activation and the immune cell type, but not exosome source, as factors regulating gene expression by exosomes. Treg were more sensitive to TEX-mediated effects than other T cell subsets. In Treg, TEX-mediated down-regulation of genes regulating the adenosine pathway translated into high expression of CD39 and increased adenosine production. TEX also induced up-regulation of inhibitory genes in CD4(+) Tconv, which translated into a loss of CD69 on their surface and a functional decline. Exosomes are not internalized by T cells, but signals they carry and deliver to cell surface receptors modulate gene expression and functions of human T lymphocytes.
Unsupervised analysis (a) and supervised analysis (b) of the combined data obtained with different resting and activated T cell subsets of 3 normal donors co-incubated with TEX or DEX.
The data are mean Ct values calculated for mRNA expression levels of each of the 24 genes examined. In (a) note higher Ct values (i.e., lower mRNA expression levels) for a number of immunoregulatory genes in activated T cell subsets. The asterisks indicate differences in gene expression of activated Treg co-incubated with TEX or DEX. In (b) the same data for resting and activated T cell subsets are compared in a supervised analysis to indicate mean Ct values for genes regulating inhibitory, stimulatory, apoptotic or adenosine-related pathways.