This quantification was made, e.g., using residual γH2A.X foci analysis (for example, more efficient foci resolution was shown for lung cancer CD133+ cells [12], murine cancer CD29+CD24high cells [13], head and neck squamous cell carcinoma (HNSCC) ALDH+ cells [14], glioblastoma CSC populations in patient-derived cell lines [15]) or by comet assay (for example the lower amount of DNA damage was found in glioblastoma patient-derived CD133+ cells [16], CD133+CD44+ colon cancer cells [17] and murine cancer CD29+CD24high cells [13]). Here, CD44 is linked to head and neck squamous cell carcinoma.