PER2 and head and neck squamous cell carcinoma: Next, the basal mRNA expression level of PER2, DUSP1 and NF1 was evaluated in the HNSCC cell lines (FaDu, UTSCC42a and UTSCC8) compared to the NOE cells, demonstrating that PER2 and NF1 were indeed significantly lower in these cell lines (<0.75 fold), thus were selected for further validation (Fig. 3B).