In the present study, the level of OPN expression was found to correlate with the SOX9 expression in all four HCC cell lines tested, and qRT-PCR assays revealed that sorted EGFP+ cells, that is, SOX9+ cells, showed significantly higher OPN expression than EGFP−/SOX9− cells in the HLF and PLC/PRF/5 cell lines (Fig. 5A). Here, SPP1 is linked to hepatocellular carcinoma.