Sphingosine-1-phosphate Receptor-1 Promotes Vascular Invasion and EMT in Hepatocellular Carcinoma

It remains unknown whether epithelial-mesenchymal transition (EMT)-mediated vascular invasion and cancer stemness are associated with sphingosine-1-phosphate receptor-1 (S1PR1) expression in human hepatocellular carcinoma (HCC). The aim of this study was to investigate the correlation between S1PR1 expression and prognosis of patients with primary HCC and to define the potential of S1PR as a therapeutic target.

We investigated 108 patients who underwent primary surgical resection for HCC treatment. Expression of S1PR1 and EMT markers was analyzed to predict prognosis of patients with HCC. Furthermore, three-dimensional organotypic culture, anoikis assay, and cell invasion were performed to validate the association of S1PR1 with EMT and cancer stemness.

Among patients with HCC, the high S1PR1 expression group had significantly shorter overall survival than the low expression group. Moreover, high S1PR1 expression was significantly associated with shorter recurrence-free survival, increased risk of portal and hepatic vein invasion, and intrahepatic metastasis. Multivariate analyses revealed that S1PR1 overexpression was an independent prognostic factor in patients with HCC. S1PR1 overexpression positively correlated with vimentin and MMP-9 expression and negatively correlated with E-cadherin. In addition, S1PR1 overexpression induced EMT and enhanced tumor invasion and cancer stemness.

S1PR1 overexpression, via EMT-induced vascular invasion and increased cancer stem cell properties, establishes a metastatic niche, enhances the capacity of hematogenous metastasis, and associates with poor outcomes in patients with HCC. Hence, S1PR1 may serve as a therapeutic target for patients with HCC with vascular invasion.