APEX1 and head and neck squamous cell carcinoma: We initially investigated the expression patterns of the BRCA2, XPD and APE1 genes in the matched tumour tissue, NAT and blood samples of 12 out of the 106 HNSCC patients enrolled for this study by quantitative real time-PCR, normalising them against the levels of expression of the genes in the blood samples of 8 age- and gender-matched controls.