Purpose: Early formation of portal vein tumor thrombosis (PVTT) is a key characteristic of hepatocellular carcinoma (HCC) metastasis, but to date, the aetiology of PVTT in HCC metastasis is largely unknown. We aim to find highly sensitive and specific biomarkers for the prediction of HCC prognosis.
Patients and methods: We used isobaric tags for relative and absolute quantitation (iTRAQ) based quantitative phosphoproteomics approach to investigate the molecular signatures of the HCC with PVTT in primary HCC tissues, surrounding non-cancerous tissues and PVTT tissues. The different proteome profiles in three groups were investigated and might reveal different underlying molecular mechanisms.
Results: In total, we identified 1745 phosphoproteins with 2724 phosphopeptides and 4594 phosphorylation sites in three groups. Among these phosphoproteins, 80 phosphoproteins were dysregulated in PVTT/Pan group, 51 phosphoproteins were dysregulated in HCC/Pan group, and 10 phosphoproteins were dysregulated in PVTT/HCC group. Furthermore, the phosphorylation of 4E-BP1 was elevated in HCC tissues and PVTT tissues in comparison with surrounding non-cancerous tissues,  and the elevated fold change of phosphorylation level was higher than that in expression level of 4E-BP1. The further IHC analysis in acohort of 20 HCC tissues showed that the phosphorylation of 4E-BP1 on Thr46 might be closely related to HCC prognosis.
Conclusion: The high phosphorylation level of 4E-BP1^Thr46 might serve as a biomarker for the diagnosis of early recurrence and metastasis of HCC.
Keywords: hepatocellular carcinoma, portal vein tumor thrombus, quantitative phosphoproteomics, 4E-BP1^Thr46, prognosis