PARP1 and head and neck squamous cell carcinoma: Given these potential S/G2 phase-based mechanisms, it is easily imaginable that the combined inhibition of PARP and the S/G2 cell cycle checkpoints could be an especially effective treatment option for HPV-positive HNSCC cells, and its radiosensitizing effect has already been demonstrated in preclinical studies in a number of other cancer entities (37, 38).