PARP1 and head and neck squamous cell carcinoma: Given that there is accumulating evidence that HPV-positive HNSCC cells harbour defects in DSB repair efficiency, it is understandable that inhibition of PARP that coordinates BER has been investigated as a mechanism to further radiosensitise cells through synthetic lethality, in a similar context to BRCA-deficient tumours (Refs 68, 69).