The flavonoid eupatorin inactivates the mitotic checkpoint leading to polyploidy and apoptosis

Area of Science:

• Cell Biology
• Molecular Biology
• Pharmacology

Background:

• The spindle assembly checkpoint (SAC) is crucial for accurate chromosome segregation during mitosis, preventing aneuploidy and potential tumorigenesis.
• Dysfunction of the SAC can lead to genomic instability, but its complete disruption can induce cell death, presenting a therapeutic opportunity.
• Novel inhibitors of the SAC are sought for their potential in cancer therapy.

Purpose of the Study:

• To identify novel inhibitors of the spindle assembly checkpoint (SAC) from a library of bioactive compounds.
• To investigate the mechanism of action of a newly identified SAC inhibitor, eupatorin.
• To evaluate the anti-cancer potential of eupatorin in various cancer cell models.

Main Methods:

• A high-throughput cell-based screen of 2000 bioactives was conducted to identify SAC inhibitors.
• Eupatorin's effect on mitotic arrest, microtubule-kinetochore attachments, and interkinetochore tension was assessed.
• Aurora B kinase activity was measured in cells and in vitro following eupatorin treatment.
• The impact of eupatorin on spindle formation, cytokinesis, and polyploidy was examined in pre-mitotic cells.
• Apoptosis induction and proliferation suppression by eupatorin were evaluated in cancer cell lines and 3D organotypic models.

Main Results:

• Eupatorin, a plant-derived flavonoid, was identified as a novel inhibitor of the spindle assembly checkpoint (SAC).
• Eupatorin causes premature override of mitotic arrest, dependent on microtubule-kinetochore attachments but not tension, by diminishing Aurora B kinase activity.
• Eupatorin induces spindle anomalies, impaired cytokinesis, and polyploidy in pre-mitotic cells, suggesting additional cellular targets.
• Eupatorin demonstrates potent induction of apoptosis and suppression of proliferation in multiple cancer cell lines and a 3D culture model.

Conclusions:

• Eupatorin acts as an anti-mitotic flavonoid by inhibiting the SAC through reduced Aurora B kinase activity, leading to forced mitotic exit.
• Eupatorin exhibits pleiotropic effects beyond SAC inhibition, impacting spindle integrity and cell division, contributing to its anti-cancer properties.
• Eupatorin shows significant therapeutic potential as an anti-cancer agent, effectively inducing apoptosis and inhibiting cancer cell proliferation.