EGCG treatment of the HNSCC cell lines, YCU-N861 and YCU-H891, was found to result in induction of apoptosis, which was associated with an increase in arrest of the cell cycle at the G1 phase, a decrease in the levels of cyclin D1 protein, and an increase in the levels of the tumor suppressor proteins Cip1/p21 and Kip1/p27 (Figure 2 and Figure 3) [67]. This evidence concerns the gene CCND1 and head and neck squamous cell carcinoma.