Sphingosine kinase 1: A novel independent prognosis biomarker in hepatocellular carcinoma.

Sphingosine kinase 1 (Sphk1) is an oncogenic kinase that is responsible for the phosphorylation of sphingosine to sphingosine-1-phosphate (S1P). Mounting evidence suggests that Sphk1 serves a crucial role in the proliferation and development of a variety of human cancer cells. However, the role of Sphk1 in hepatocellular carcinoma (HCC) has not been fully elucidated. Therefore, the expression of Sphk1 was examined in 127 formalin-fixed, paraffin-embedded HCC tissues using immunohistochemistry, and its clinical implications and prognostic significance were analyzed. As a result, the expression of Sphk1 in HCC tissue was revealed to be significantly higher than in normal tissue (P<0.01). In addition, Sphk1 expression was significantly associated with tumor size, tumor stage and histological differentiation (all P<0.05). The patients with low Sphk1 expression had higher overall survival and recurrence-free survival rates compared with patients with high Sphk1 expression. Furthermore, Sphk1-specific shRNA was used to downregulate the expression of Sphk1 in HCC cell lines, including hepatoblastoma G2 and HCC-9724. The CRISPR/Cas9 based transcription activation system was used to upregulate Sphk1 expression in the normal live cell, L02. Cell proliferation, mRNA expression and protein expression were measured using Cell Counting Kit-8, reverse transcription polymerase chain reaction and western blot analysis in the transfected cells. To the best of our knowledge, the present study provides the first evidence that Sphk1 promotes HCC cell proliferation and is involved in tumor progression. Notably, the data presented suggest that Sphk1 may be a potential independent prognosis biomarker for the treatment of HCC.