To search for tumor biomarkers that may be used for diagnosis of esophageal squamous cell carcinoma (ESCC) by comparing and analyzing the differentially expressed proteins of plasma exosomes between ESCC patients and healthy individuals.

Plasma exosomes were extracted from 46 plasma samples of ESCC and healty groups respectively, and verified by detecting exosomal specific CD9 using Western blotting, then 4 random exosomal samples of ESCC patients and healthy individuals were dissolved and pooled, afterward, differential in gel electrophoresis (DIGE) was used to isolate the total proteins, and then the differential expressed protein spots raised more than 2-fold were detected by analytical software and picked, subsequently, the picked spots were identified by matrix-assisted laser-desorptionionization time-of-flight/time-of-flight mass spectrometer (MALDI-TOF/TOF MS) , and finally, one of the varied proteins was validated by enzyme linked immunosorbent assay (ELISA).

The plasma exosomes were extracted successfully after Western blotting analyzing, and 12 up-regulated expressed protein spots with more than 2-fold between ESCC and healthy individuals were selected, after identifing by MALDI-TOF/TOF MS, the proteins were serum albumin (ALB), alpha-2-HS-glycoprotein (AHSG), Ig alpha-2 chain C region (IGHA2), leucine-rich alpha-2-glycoprotein (LRG1), haptoglobin (HP) and CD9 antigen. Additionally, ELISA results showed that AHSG expression level in ESCC patients was significantly higher than that in healthy individuals [(107.1±4.9) ng/ml vs, (44.7±2.7) ng/ml, P<0.05].

The differentially expressed plasma exosomal proteins are expected to be specific tumor biomarkers for early diagnosis of ESCC.

Esophageal tumor; Squamous cell carcinoma; Exosome; Tumor biomarker; Proteomics