CDKN1A and head and neck squamous cell carcinoma: Interestingly, p21 levels were upregulated by JQ1 treatment at 24 h in bothHPV-positive – (UM: SCC47 and UD: SCC2) cells and HPV-negative – (Tu-138, D562, and FaDu) HNSCC cell lines (Supplementary Figure S3), suggesting that JQ1 can modulate p21 levels through both p53-dependent and independent mechanisms.