RB1 and head and neck squamous cell carcinoma: Together with well-known oncogenic events induced by the E6/E7 oncoproteins, such as the inactivation of TP53 and the persistent stimulation of E2F transcription factors due to RB1 inhibition [38], the specific HPV+ gene expression profiles suggest that other less studied mechanisms might also contribute to HPV-driven HNSCC development.