Stage-Dependent Exosomal Protein Expression of PD-L1 and FasL in Head and Neck Cancer (HNC) Patients

Introduction Early diagnosis of primary and recurrent disease is still a challenging factor in head and neck oncology. Stage-dependent differences could assist identifying valid biomarkers. Here, we analyzed exosomes from head and neck cancer (HNC) patients and normal donors (ND) for stage-dependent differences.

Methods Plasma exosomes were isolated from 41 HNC patients of different tumor stages and 13 ND on Sepharose columns. Exosomes were examined for their shape in electron microscope (TEM), size and concentration by Nanoparticle-Tracking Analyzer (NTA), protein content (BCA), protein profiles by CD63 bead-based flow cytometry and functional impact on CD8⁺Jurkat cells.

Results UICC stage had no impact on the particle concentration (p>0.05). Exosomal protein content was significantly higher in advanced UICC stages III/IV compared to early stages I/II and ND (p<0.001). Stage dependent differences were observed for PD-L1 and FasL expression levels (p< 0.05), whereas Fas, PD-1 and CD44 didn’t show stage dependency (p >0.05). TGFß showed significant overexpression in early stages I/II (p<0.05), however normalized at advanced stages III/IV. Apoptosis induction in CD8⁺lymphocytes by HNC exosomes was stage independent higher than by ND (p<0.05).

Conclusion Exosomal protein content and expression of PD-L1 and FasL on exosomes are promising biomarkers for tumor progression, while the grade of apoptosis induction in lymphocytes by exosomes indicates disease activity. Thus, exosomes could be favourable liquid biomarkers for disease activity and progression.

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Publication History

Article published online:
10 June 2020