Effects of Tumor-specific Exosomes (TEX) on B Cell Populations in Head and Neck Squamous Carcinoma (HNSCC)

Background:

HNSCCs induce a highly immunosuppressive tumor microenvironment (TME). The complex interactions between tumor cells and the TME yet remain unclear. Tumor cells manipulate the immune system, among other things, by secretion of immunosuppressive exosomes, which might have effects on the function and frequency of immunosuppressive cell populations such as regulatory T or B cells. Activation of B cells via the B cell receptor (BCR) involves phosphorylation of Bruton's Tyrosine Kinase (BTK). Here, we show that exosomes can reduce the expression of phosphorylated BTK (p-BTK) in B cells in vitro.

Material and Methods:

Exosomes were isolated both from plasma of HNSCC patients and supernatants of HNSCC cell cultures by mini size exclusion chromatography. B cells were purified from peripheral blood of healthy donors by LeukoSep and CD19-negative selection and incubated with HNSCC exosomes. Activity of the BCR pathway was assessed by antibody-mediated stimulation of µ-BCR and subsequent staining for phosphorylated BTK (p-BTK) via flow cytometry.

Results:

Incubation with exosomes reduced the expression of p-BTK in stimulated B cells from healthy donors. This effect was observed both with exosomes obtained from HNSCC plasma and tumor cell culture supernatants. Furthermore, the effect was dependent on dose and duration of exosome incubation.

Conclusions:

We provide evidence of a direct effect of tumor-derived exosomes on B cells in vitro. The reduction in BTK phosphorylation suggests that tumor-specific exosomes can affect not only T cells but also B cells.

Publikationsverlauf

Publikationsdatum:
23. April 2019 (online)