SPP1 and hepatocellular carcinoma: Intriguingly, EGCG lowered the level of secreted osteopontin, a protein similar to AFP, which also mediated HCC metastasis and invasion.28 Because a previous report demonstrated that secreted AFP could enhance tumor cell proliferation by binding to AFP receptors localized in HCC cell membranes,29 we considered that the diminished AFP secretion by EGCG should be one of the reasons behind the inhibition of HepG2 growth.