Western blot analysis of the ALDH1A3 protein level in xenograft tumors derived from ALDH+ and ALDH− cells of both tumor models, Cal33 and FaDu, revealed high ALDH1A3 protein level in the xenografts grown from ALDH+ cells, which kept their tumorigenicity in vivo, in contrast to the tumors established from ALDH− cells, which lost their tumorigenic potential upon radiation (Figure 4A). This evidence concerns the gene ALDH1A3 and neoplasm.