The results showed that 104 ALDH1− did not induce tumor formation but 3,000 ALDH1+ from the HNSCC tissues of six patients in xenotransplanted mice all resulted in the generation of visible tumors 6 weeks after injection (Table 1).The results of xenotransplanted analysis further showed that ALDH1+ demonstrated higher abilities to induce tumor growth (Figure 1(e)). Here, ALDH1A1 is linked to head and neck squamous cell carcinoma.