CCND1 and head and neck cancer: Several studies have suggested that downregulation of p53, pRb and cyclin D1 and upregulation of p16INK4A in HPV-positive head and neck cancer patients are the consequence of functional inactivation of two key tumor suppressor proteins, p-p53 and p-Rb, by the HPV E6 and E7 oncoproteins (18,23,28).