MDM2 and head and neck squamous cell carcinoma: Using the isogenic HNSCC cell lines, HN30 and HN31, which endogenously express either wtp53 (HN30) or missense p53 mutations, C176F and A161S, (HN31), HN30 was shown to upregulate expression of downstream p53 targets CDKN1A (p21) and MDM2 following treatment with nutlin-3; which inhibits the interaction between mdm2 and wild type p53, therefore stabilizing and leading to increased levels of the p53 protein.