Both are Hepatocellular carcinoma (HCC). HepG2 was derived from a liver hepatocellular carcinoma of a 15 year old Caucasian male. The cells express 3-hydroxy-3-methylglutaryl-CoA reductase and hepatic triglyceride lipase activities.
The cells demonstrate decreased expression of apoA-I mRNA and increased expression of catalase mRNA in response to gramoxone (oxidative stress). There is no evidence of a Hepatitis B virus genome in this cell line.
The HuH-7 cell line was established in 1982 from a well differentiated hepatocyte derived cellular carcinoma cell line that was originally taken from a liver tumor in a 57-year-old Japanese male. Huh-7 is highly susceptible to the hepatitis C virus (HCV), and it is often used as a model to investigate hepatoma and HCV. This cell line can be used for an HCV replicon system, which allows for an in vitro production of infectious HCV particles and development of drugs that combat HCV. Huh-7 is an immortal cell line composed of epithelial-like, tumorigenic cells.
For more information, I suggest consulting ATCC Cell lines:
It is very important to known the differences on p53 expresion. In this way, HepG2 cells carry wild-type p53, whereas Hep3B and Huh7 cells have null and point mutations at p53 codon 220 respectively.