SMYD3 and head and neck squamous cell carcinoma: To assess whether SMYD3 affects cell proliferation in HPV-negative HNSCC cell lines, we conducted CCK8 assays in 4 HPV-negative HNSCC cell lines (HN-6, PE/CA-PJ15, HN13 and YD-10B) after siRNA-mediated knockdown of SMYD3 (Supplementary Fig. 1A).