To test its potential role in the regulation of cellular radioresponse, we employed 2D and 3D radiobiological clonogenic survival assays, as for the IR and parental sublines, to analyze the in vitro radioresistance of the cells with a high versus low ALDH activity (ALDH+ and ALDH− cell populations, respectively) isolated from Cal33 and FaDu HNSCC cell lines (Figure S4B and S4C). This evidence concerns the gene LDHA and head and neck squamous cell carcinoma.