Berberine Suppresses Cyclin D1 Expression through Proteasomal Degradation in Human Hepatoma Cells

Area of Science:

• Molecular Biology
• Oncology
• Pharmacology

Background:

• Cyclin D1 is a crucial regulator of cell cycle progression.
• Dysregulation of Cyclin D1 is implicated in the development of various cancers, including hepatocellular carcinoma.
• Berberine, a natural compound, has demonstrated anti-cancer properties, but its precise mechanisms are not fully understood.

Purpose of the Study:

• To elucidate the molecular mechanism by which berberine induces the degradation of Cyclin D1 in human liver cancer cells.
• To investigate the role of post-translational modifications and protein degradation pathways in berberine's anti-cancer effects.

Main Methods:

• In vitro and in vivo studies using human hepatoma cells (HepG2).
• Assessment of Cyclin D1 expression, phosphorylation, and subcellular localization.
• Investigation of the ubiquitin-proteasome system and the involvement of the SCFβ-TrCP complex.
• Gene knockdown experiments targeting β-TrCP.

Main Results:

• Berberine significantly suppressed Cyclin D1 expression in a dose- and time-dependent manner in HepG2 cells.
• Berberine promoted Cyclin D1 phosphorylation at Thr286, leading to its nuclear export and subsequent proteasomal degradation.
• Berberine facilitated the recruitment of the SCFβ-TrCP E3 ubiquitin ligase complex for Cyclin D1 degradation.
• Knockdown of β-TrCP abrogated berberine-induced Cyclin D1 degradation and increased cancer cell resistance to berberine.

Conclusions:

• Berberine induces Cyclin D1 degradation through the ubiquitin-proteasome pathway, involving phosphorylation and nuclear export.
• The SCFβ-TrCP complex plays a critical role in mediating berberine's effect on Cyclin D1.
• These findings highlight berberine's potential as a therapeutic agent for hepatocellular carcinoma by targeting Cyclin D1 degradation.