Two distinct Notch signals, Delta-like 4/Notch1 and Jagged-1/Notch2, antagonistically regulate chemical...

Area of Science:

• Oncology
• Molecular Biology
• Hepatology

Background:

• Notch signaling is a key regulator in cancer, including hepatocellular carcinoma (HCC).
• The specific roles of different Notch ligands and receptors in HCC development remain largely unclear.
• Notch signaling can either promote or suppress tumor progression depending on the context.

Purpose of the Study:

• To investigate the distinct roles of Notch ligands Delta-like 4 (Dll4) and Jagged-1 (Jag1) in hepatocellular carcinoma (HCC) development.
• To elucidate how Dll4/Notch1 and Jag1/Notch2 signaling pathways differentially regulate HCC progression.
• To understand the interplay between these distinct Notch signaling pathways in hepatocarcinogenesis.

Main Methods:

• Utilized a diethylnitrosamine-induced hepatocarcinogenesis model in mice.
• Analyzed the expression patterns of Notch ligands Dll4 and Jag1 in preneoplastic and cancerous liver tissues.
• Generated hepatocyte-specific knockout models for Dll4 and Jag1 to assess their functional impact on HCC progression and Notch signaling.
• Examined Notch1 and Notch2 signaling activation in response to ligand manipulation.

Main Results:

• Dll4 expression was upregulated in preneoplastic hepatocytes and HCC cells, while Jag1 was found in mesenchymal cells.
• Hepatocyte-specific knockout of Dll4 abolished Notch1 signaling and suppressed tumor progression.
• Jag1 deletion led to ectopic Dll4 expression in hepatocytes, loss of Notch2 signaling, and promoted tumor progression.
• These findings indicate antagonistic roles for Dll4/Notch1 and Jag1/Notch2 signaling in HCC.

Conclusions:

• Dll4/Notch1 signaling acts as a tumor suppressor in HCC.
• Jag1/Notch2 signaling promotes HCC progression through mechanisms involving Dll4 regulation.
• The opposing functions of Dll4/Notch1 and Jag1/Notch2 pathways highlight their critical and distinct roles in liver cancer development.