PARP1 and head and neck squamous cell carcinoma: In addition, studies have shown that the DNA-PK inhibitors KU57788 and IC87361 are more potent radiosensitizing agents than the PARP-1 inhibitors veliparib and olaparib at non-cytotoxic concentrations in HNSCC cell cultures, and that their activities can be enhanced by SLFN11 and hypoxia (143).