Importantly, strong up-regulation of GADD45A and CDKN1A gene expression was observed in both CBD-treated FaDu and SCC15 cells (Fig. 6B), suggesting that CBD might induce apoptosis and cell cycle arrest by modulating GADD45A and p21 levels in HNSCC cells. This evidence concerns the gene GADD45A and head and neck squamous cell carcinoma.