RASSF1 and head and neck squamous cell carcinoma: RASSF1α, PCQAP 5′ and PCQAP 3′ were significantly (p < 0.0001, p < 0.0001 and p < 0.005 respectively) hypermethylated in saliva collected from HPV-negative HNSCC patients whilst p16INK4a, PCQAP 5′and PCQAP 3′ were significantly (p < 0.005, p < 0.05 and p < 0.005 respectively) hypomethylated in the saliva collected from HPV-positive HNSCC patients compared with normal healthy controls (Fig. 2).