Molecular targets for apigenin-induced cell cycle arrest and apoptosis in prostate cancer cell xenograft

Area of Science:

• Oncology
• Molecular Biology
• Pharmacology

Background:

• Apigenin (4',5,7-trihydroxyflavone) is a natural flavonoid with demonstrated chemopreventive properties.
• It has shown potential in inducing cell cycle arrest and apoptosis in various cancer cell lines.
• Its direct impact on human prostate tumor growth in vivo and its molecular targets remained to be elucidated.

Purpose of the Study:

• To investigate the direct growth inhibitory effects of apigenin on human prostate tumors in an in vivo mouse model.
• To identify specific cell cycle regulatory molecules targeted by apigenin action.
• To explore the correlation between apigenin intake, its levels, and tumor response.

Main Methods:

• Administration of apigenin via oral gavage to athymic nude mice bearing human prostate tumors (22Rv1 and PC-3).
• Analysis of cell cycle regulatory protein expression (WAF1/p21, KIP1/p27, INK4a/p16, INK4c/p18, cyclins D1/D2/E, cdk2/4/6, retinoblastoma, p53).
• Assessment of protein-protein interactions and apoptosis induction, correlated with serum and tumor apigenin levels.

Main Results:

• Apigenin significantly reduced tumor volume and mass in both androgen-sensitive and insensitive prostate cancer models.
• Dose-dependent increases in cell cycle inhibitors (p21, p27, p16, p18) and decreases in cyclins and cdks were observed.
• Apigenin treatment led to decreased retinoblastoma phosphorylation, increased cyclin D1/p21 binding, decreased cyclin E/cdk2 binding, p53 stabilization, and induced apoptosis.

Conclusions:

• Apigenin exhibits direct in vivo growth inhibitory effects on human prostate tumors.
• Apigenin targets cell cycle regulatory proteins, modulating their expression and interactions.
• This study provides the first systematic in vivo evidence of cell cycle proteins as molecular targets for apigenin's anti-cancer activity.