MMP9 and hepatocellular carcinoma: MMP‐2, another important MMP with a molecular weight of 72 kD, was not expressed in these HCC cells (HepG2 and MHCC97H), as no 72 kD band could be seen from the zymography gel treated with or without TPA treatment (data not shown), suggesting that MMP‐9 may be the main functional MMP in these HCC cells.