CDKN1A and head and neck squamous cell carcinoma: Upstream analyses of CDKN2A associated pathways using the Ingenuity Pathway Analysis tool support our hypothesis that in HNSCC patients CDKN2A pathways are inactivated which is attended by silencing of the negative cell cycle regulator RB1, the CDK inhibitor CDKN1A, and the tumour suppressor TP53 (Supplementary Fig. S2A).