Liver carcinogenesis: from naughty chemicals to soothing fat and the surprising role of NRF2

In this review, we summarize studies that describe the molecular mechanisms of HCC development, primarily focusing on the work from our laboratory.The liver is a key metabolic organ that is essential for production of blood proteins, lipid and sugar metabolism and detoxification of naturally occurring and foreign harmful chemicals. To maintain its mass and many essential functions, the liver possesses remarkable regenerative capacity, but the latter also renders it highly susceptible to carcinogenesis. In fact, liver cancer often develops in the context of chronic liver injury. Currently, primary liver cancer is the second leading cause of cancer-related deaths, and as the rates of other cancers have been declining, the incidence of liver cancer continues to rise with an alarming rate. Although much remains to be accomplished in regards to liver cancer therapy, we have learned a great deal about the molecular etiology of the most common form of primary liver cancer, hepatocellular carcinoma (HCC). Much of this knowledge has been obtained from studies of mouse models, using either toxic chemicals, a combination of fatty foods and endoplasmic reticulum stress or chronic activation of specific metabolic pathways. Surprisingly, NRF2, a transcription factor that was initially thought to protect the liver from oxidative stress, was found to play a key role in promoting HCC pathogenesis.