In a study comparing response to 2–10 μM Veliparib in two HPV-positive vs one HPV-negative HNSCC cell-lines (UMSCC47, UPCISCC154 and UMSCC1 respectively), the HPV-negative line appeared approximately 1.5 fold less sensitive, and, contrary to our study, slower resolution of γ-H2AX foci in the HPV-positive cell-lines was observed [16]. The gene discussed is H2AX; the disease is head and neck squamous cell carcinoma.