To further investigate the inherent molecular mechanisms mediating the inhibition effect of EEA on HNSCC cell proliferation, western blot analysis was conducted to determine the cellular levels of cleaved caspase-9 and cleaved PARP, which were markedly increased in cells treated with EEA in a dose-dependent manner (Figure 1B). This evidence concerns the gene CASP9 and head and neck squamous cell carcinoma.