Introduction:
Proteomics technology platforms offer an extremely useful tool for the discovery of new cancer biomarkers. Secreted proteins play important roles in signal transduction, cellular growth, proliferation, differentiation, and apoptosis. This study aimed to investigate the molecular signatures of the hepatocellular carcinoma (HCC) by quantitative proteomics using isobaric tags for relative and absolute quantification (iTRAQ) with liquid chromatography-tandem mass spectrometry (LC-MS/MS).

Material and methods:
In this study, we used an iTRAQ-based quantitative proteomic approach to analyse the secretome of HCC tissues to identify plasma biomarkers. Serum-free conditioned media (CM) were collected from the primary cultures of cancerous tissues, the surrounding noncancerous tissues, and distal noncancerous tissues.

Results:
A proteomic analysis of the CM proteins allowed for a total of 5214 identified proteins, of which 190 and 44 proteins were dysregulated in the HCC tissues/distal noncancerous tissues (HCC/DN group) and the adjacent noncancerous tissues/distal noncancerous tissues (AN/DN group) compared with the distal noncancerous tissues. The dysregulated proteins in the HCC/DN group were concentrated in mitogen-activated protein kinase (MAPK) signalling and Janus kinase-signal transducer and activator of the transcription (JAK-STAT) signalling, but the dysregulated proteins in the AN/DN group were more concentrated in the basal material metabolism.

Conclusions:
The secretome profile alternations and signalling pathways were associated with HCC incidence and development. The dysregulated proteins in the HCC/DN group were concentrated in the MAPK signalling and JAK-STAT signalling, but the dysregulated proteins in the AN/DN group were more concentrated in the basal material metabolism.