Reappraisal of the anticancer efficacy of quercetin in oral cancer cells.

Background: Despite increased experience in therapy, the overall outcome of oral squamous cell carcinoma (OSCC) has not improved because of the relative resistance to chemotherapeutic drugs in addition to local invasion and frequent regional lymph node metastases. Quercetin (Qu) is a principal flavonoid compound and an excellent free-radical-scavenging antioxidant that promotes apoptosis. Limited reports regarding the molecular or cellular role of Qu in anticancer properties on OSCC have been presented. This study was conducted to clarify the efficacy of Qu on OSCC in vitro and further to evaluate the possible mechanism(s).

Methods: Cultured OSCC cells (SCC-25) and human gingival fibroblasts (HGFs) were treated with different concentrations of Qu. Cell viability and cell colony-forming potential were detected with the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) and colony growth assays. Cell-cycle analysis and apoptosis were measured by flow cytometry. Cell migration and invasion were tested using the micropore chamber assay.

Results: Cell viability and colony-forming potential were decreased in a dose-dependent manner following Qu treatment. Qu also dose-dependently inhibited the proliferation of SCC-25 cells via both G1 phase cell cycle arrest and mitochondria-mediated apoptosis. In addition, Qu also decreased the abilities of migration and invasion of SCC-25 cells in a dose-dependent manner.

Conclusion: Qu effectively inhibits cell growth and invasion/migration of SCC-25 cells in vitro. The cellular and molecular mechanisms are via cell cycle arrest accompanied by mitochondria-mediated apoptosis. Our findings suggest that Qu may have potential as a new chemopreventive agent or serve as a therapeutic adjuvant for OSCC.