TGFβ1 treatment enhances cisplatin resistance of HNSCC K3 CSCs. (A) Cell viability subsequent to cisplatin administration at various concentrations of TGFβ1- or control (DMSO)-treated HNSCC CSCs. (B) mRNA levels of ABCG2 in TGFβ1- or control (DMSO)-treated HNSCC CSCs. **P<0.01.TGFβ1, transforming growth factor β; HNSCC, head and neck squamous cell carcinoma; CSCs, cancer stem cells; DMSO, dimethyl sulfoxide; ABCG2, ATP-binding cassette sub-family G member 2