Exosomes from HPV-positive and HPV-negative HNC cell lines: novel option as liquid biomarker?

Introduction:

Exosomes, virus-sized vesicles, carry protein cargos resembling those of their parent cells and modify immune cell functions. Here, we address the query whether exosomes derived from Human Papilloma Virus-positive (HPV+) or HPV-negative (HPV-) HNC cell lines differ in molecular and immunoregulatory profiles.

Methods:

Concentrated supernatants of 3 HPV+ (SCC-2, SCC-47, SCC-90) and 2 HPV- (PCI-13, PCI-30) HNC cell lines were added to Sepharose-based size exclusion chromatography columns. Exosomes in fraction #4 were assessed for morphology and size by electron microscopy (TEM) and for protein content by BCA. Protein profiles were determined by Western blots and mass spectrometry. The impact of exosomes on immune functions were measured in co-culture assays with human T cells.

Results:

Exosomes from all cell lines were similar in size (30 – 150nm) and protein levels (2 – 10ug/mL). HPV+ cell line and exosomes carried E6, E7 and p16. Immunomodulating molecules (TGFß, FasL, HSP70) were equally expressed on all exosomes. Mass spectrometry and gene ontology analysis revealed that driving energy pathways were twice frequent in HPV+ exosomes (p < 0.0001), whereas cell growth/maintenance and immune response were higher expressed in HPV- exosomes. No differences were observed in the ability of HPV+ vs. HPV- exosomes to induce apoptosis in activated T cells or suppress their activation and proliferation.

Conclusions:

Exosomes derived from HPV+ HNCs carried viral antigens and had proteomic profiles that were distinct from that of HPV- exosomes. Immunosuppression mediated by HPV+ and HPV- exosomes were comparable. Exosomes reflect the HPV status of their parent cells and thus might serve as future plasma biomarkers of HPV infection in HNC.

Publication History

Publication Date:
18 April 2018 (online)