Hepassocin, also known as hepatocyte-derived fibrinogen-related protein 1 (HFREP-1), is a liver-specific secreted protein belonging to the fibronogen superfamily, whose members share a fibrinogen domain at their C-termini. It is secreted by the liver and functions as a mitogen for hepatocytes. Hepassocin may play a role in the development of hepatocellular carcinomas. Hepassocin is a disulfide-linked homodimeric protein with a C-terminal fibrinogen domain. It is reported that it is a major immune inhibitory ligand of LAG-3 .