Liver cancer development driven by the AP-1/c-Jun~Fra-2 dimer through c-Myc

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• Hepatocellular carcinoma (HCC) is a significant cause of cancer mortality with limited treatment options.
• Understanding HCC molecular pathways is crucial for developing new therapies.
• The role of Fos-related antigens (Fra-1 and Fra-2) in HCC pathogenesis is largely unknown.

Purpose of the Study:

• To investigate the role of Fos-related antigens (Fra-1 and Fra-2) in hepatocellular carcinoma (HCC) development.
• To establish a mouse model for studying HCC driven by AP-1 transcription factors.
• To identify molecular targets for HCC therapy.

Main Methods:

• Generated hepatocyte-restricted c-Jun~Fra-2 transgenic mice (c-Jun~Fra-2^hep).
• Analyzed tumor formation, molecular pathways, and gene expression in the mouse model.
• Investigated the role of c-Myc and c-Fos in tumorigenesis and therapeutic interventions.

Main Results:

• Hepatocyte-specific expression of c-Jun~Fra-2 induced spontaneous HCC formation in mice.
• Tumors exhibited hallmarks of human HCC, including cell cycle dysregulation and altered gene expression.
• c-Jun~Fra-2 directly upregulated c-Myc expression via a distal enhancer.
• Tumor growth was dependent on c-Jun~Fra-2, with reversion observed upon transgene withdrawal.
• In established tumors, c-Myc and c-Fos maintained expression, and inhibition of c-Myc reduced tumor growth.

Conclusions:

• The c-Jun/Fra-2 AP-1 dimer is oncogenic in the liver and drives HCC development.
• The c-Jun/Fra-2-c-Myc signaling axis is critical for HCC initiation and maintenance.
• c-Jun~Fra-2^hep mice serve as a valuable model for liver cancer research.
• Targeting the c-Jun/Fra-2-c-Myc interaction holds potential for HCC therapy and patient stratification.