Background: Biomarker studies revealed important clinical significance of exosome for cancer patients. However, there is currently no consensus on exosome quantification methods.
Methods: Bicinchoninic acid (BCA) method, acetylcholinesterase (AChE) method and nanoparticle tracking analysis (NTA) were utilized to quantify 20 plasma exosome samples, and interrelations between these three methods were explored. Associations of plasma exosome levels with characteristics and prognosis of 208 non-small-cell lung cancer (NSCLC) patients were investigated.
Results: Results of the three methods for exosome quantification were significantly correlated with each other. Correlation coefficient between AChE and NTA (r= 0.79, P< 0.001) was greater than that between BCA and NTA (r= 0.64, P= 0.003). Plasma exosome levels of 208 NSCLC patients were then quantified with AChE method. Exosome level was significantly associated with tumour stage (P< 0.001) and the history of chronic obstructive pulmonary disease (P= 0.023). Cox proportional hazard analysis demonstrated that higher exosome level was independently associated with poorer overall survival (P= 0.033; hazard ratio = 1.72, 95% confidence interval: 1.05-2.83).
Conclusions: Plasma exosome level correlates with tumor stage and the history of chronic obstructive pulmonary disease, and may serve as a prognostic factor for NSCLC.
Keywords: Non-small-cell lung cancer; biomarker; exosome; prognosis; quantification.