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Secretion of Extracellular Matrix (Fibronectin), Growth Factor (Transforming Growth Factor β) and Protease (Cathepsin D) by Hepatoma Cells

We investigated facilitation of invasion by growth factors and chemotactic factors in tumor cell lines, particularly hepatocellular carcinoma. Hepatoma cells (PLC/PRF/5 and Hep G2) showed strong chemotaxis toward their respective conditioned media while metastatic pancreatic cancer cells (SU.86.86) and colon cancer cells (LS 174T) did not migrate toward their respective conditioned media. Based on immunoblotting, PLC/PRF/5 cells secrete fibronectin (an extracellular matrix constituent), transforming growth factor-β (TGFβ; a growth factor), and cathepsin D (a protease). Fibronectin induced a migratory response in PLC/PRF/5 cells, and anti-fibronectin antibody abolished the migratory response of these cells to their conditioned medium. Anti-integrin-β1 antibody also impeded migration of these cells toward conditioned medium. Polyclonal anti-TGFβ antibody and protease inhibitors (α2-macroglobulin and leupeptin) added to culture media-modulated secretion of fibronectin by PLC/PRF/5 cells. Although exogenous TGFβ suppressed SU.86.86 cells, it enhanced PLC/PRF/5 cell adhesion to substrate, increasing viable cell numbers. These actions indicate that hepatocellular carcinoma may possess a forceful autocrine mechanism enabling cells to survive and proliferate under cirrhotic conditions.