TP53BP1 and head and neck squamous cell carcinoma: By comparing five HPV-positive and five HPV-negative HNSCC cell lines (Table 1), although it was demonstrated that there was a high variability in radiosensitivity, in general the HPV-positive cells were more radiosensitive and that the three most sensitive (UPCI-SCC154, UMSCC47 and UDSCC2) showed high residual levels of DSBs 24 h post-IR via detection of γH2AX/53BP1 foci (Ref.