BRCA2 and head and neck squamous cell carcinoma: Preclinical testing of the PARP inhibitor veliparib (ABT-888) in HNC cell lines and an HPV(+) patient xenograft has produced encouraging results; HPV(+) HNSCC cell lines that were deficient for BRCA2 and DNA-PK proteins, both key molecules of HR and NHEJ, exhibited sensitivity to the PARP inhibitor, as evidenced by a decreased survival rate in vitro and a delay in tumor growth in vivo [206].