Hepatic lipids promote liver metastasis

Area of Science:

• Hepatology
• Oncology
• Metabolic Diseases

Background:

• Obesity and nonalcoholic fatty liver disease (NAFLD) are widespread, and obesity is a known cancer risk factor.
• The specific role of hepatic steatosis (fatty liver) in the development of liver metastases remains unclear.
• Understanding this link is crucial for developing targeted cancer therapies.

Purpose of the Study:

• To investigate the impact of NAFLD on the development and progression of liver metastases from breast cancer and melanoma.
• To elucidate the molecular mechanisms by which hepatic steatosis promotes liver metastasis.
• To determine if the pro-metastatic effects of NAFLD are linked to metabolic syndrome or are directly due to steatosis.

Main Methods:

• Comparison of liver metastasis incidence in control mice versus lipodystrophic/obese mice with NAFLD.
• Analysis of triglyceride lipolysis, fatty acid transfer (via fatty acid transporter protein 1), and mitochondrial metabolism in cancer cells.
• Histological examination of human liver metastases.
• Assessment of metformin's effect on steatosis-induced metastasis.
• Evaluation of adipose tissue transplantation to reverse NAFLD and its effect on metastasis.

Main Results:

• Mice with NAFLD exhibited a dramatic increase in breast cancer and melanoma liver metastases compared to controls.
• NAFLD promotes metastasis through tumor-induced lipolysis in hepatocytes, with lipid transfer to cancer cells enhancing their growth.
• Human liver metastasis histology confirmed this mechanism.
• Steatotic lipids demonstrated enhanced tumor-stimulating capacity compared to lipids from normal livers.
• Metformin did not reduce metastasis, indicating it's not mediated by metabolic syndrome.
• Adipose tissue transplantation, by eradicating NAFLD, reduced metastasis to control levels.

Conclusions:

• Hepatic steatosis, a hallmark of NAFLD, significantly promotes liver metastasis in obesity.
• The mechanism involves lipid transfer from hepatocytes to cancer cells, fueling tumor growth.
• The predisposition to metastasis induced by NAFLD is reversible upon correction of the fatty liver condition.