SPHK1 and neoplasm: To investigate the role of HULC in tumor angiogenesis, we screened the expression of several tumor angiogenesis-associated factors, such as VEGF, SPHK2, transforming growth factor-beta receptor 2 (TGF-βR2), monocyte chemoattractant protein 1 (MCP1) and SPHK1 [22, 23], in HULC over-expressed HepG2 cells.