Kulsum et al. [104] found that head and neck squamous cell carcinoma cells resistant to cisplatin, 5-FU or docetaxel showed the hyperexpression of stem cell marker proteins (CD44, CD133, ALDH1A1, NOTCH1, Oct4 and SOX2) and displayed an increase in migration and invasion, spheroid, colony and tumorigenic formation, which was reversed by ALDH1A1 knockdown. The gene discussed is ALDH1A1; the disease is head and neck squamous cell carcinoma.