To evaluate the effect of Brazilian propolis on head and neck cancer stem cells in vitro.
Head and neck squamous cell carcinoma (HNSCC) cell lines (UM-SCC-17B and UM-SCC-74A), human keratinocytes (HK), and primary human dermal microvascular endothelial cells (HDMEC) were treated with 0.5, 5.0, or 50 μg/mL green, brown or red Brazilian propolis or vehicle control for 24, 36, and 72 h. Cell viability was evaluated by Sulforhodamine B assay. Western blots evaluated expression of cancer stem cell (CSC) markers (i.e. ALDH, CD44, Oct-4, Bmi-1) and flow cytometry was performed to determine the impact of propolis in the fraction of CSC, defined as ALDHCD44 cells.
propolis significantly reduced cell viability of HNSCC and HDMEC cells, but not HK. Notably, red propolis caused a significant reduction in the percentage of CSC, reduced the number of orospheres, and downregulated the expression of stem cell markers.
Collectively, our data demonstrate an anti-CSC effect of propolis, and suggest that propolis (i.e. red propolis) might be beneficial for patients with head and neck cancer.

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