Apigenin inhibited hypoxia induced stem cell marker expression in a head and neck squamous cell carcinoma cell line.

OBJECTIVE: Cancer stem cells contribute to tumor recurrence, and a hypoxic environment is critical for maintaining cancer stem cells. Apigenin is a natural product with anticancer activity. However, the effect of apigenin on cancer stem cells remains unclear. Our aim was to investigate the effect of apigenin on cancer stem cell marker expression in head and neck squamous cell carcinoma cells under hypoxia. DESIGN: We used three head and neck squamous cell carcinoma cell lines; HN-8, HN-30, and HSC-3. The mRNA expression of cancer stem cell markers was determined by semiquantitative RT-PCR and Real-time PCR. The cytotoxic effect of apigenin was determined by MTT colorimetric assay. Flow cytometry was used to reveal the number of cells expressing cancer stem cell surface markers. RESULTS: HN-30 cells, a cancer cell line from the pharynx, showed the greatest response to hypoxia by increasing their expression of CD44, CD105, NANOG, OCT-4, REX-1, and VEGF. Apigenin significantly decreased HN-30 cell viability in dose- and time-dependent manners. In addition, 40µM apigenin significantly down-regulated the mRNA expression of CD44, NANOG, and CD105. Consistent with these results, the hypoxia-induced increase in CD44+ cells, CD105+ cells, and STRO-1+ cells was significantly abolished by apigenin. CONCLUSION: Apigenin suppresses cancer stem cell marker expression and the number of cells expressing cell surface markers under hypoxia.