ALDH1A1 and head and neck squamous cell carcinoma: Furthermore, ALDH1+-derived spheres with regular 10% serum cultivation increased epithelial-attached cells and differentiation marker (CK18)(See Figure 1(a) in supplementary material available online at doi: 10.1155/2011/609259).To evaluate the enhancement of tumorigenicity of HNSCC-ALDH1+ cells, soft agar colony formation assays and Matrigel/Transwell-invasion and were examined.