SMYD2 overexpression is associated with tumor cell proliferation and a worse outcome in human papillomavirus-unrelated nonmultiple head and neck carcinomas

Human papillomavirus (HPV)-unrelated head and neck squamous cell carcinoma (HNSCC) is a heterogeneous disease, and there are no suitable prognostic or predictive markers. The SET and MYND domain-containing protein 2 (SMYD2), a lysine methyltransferase for histone H3K36 and p53K370, that regulates transcription was previously found to be a cancer-promoting gene in esophageal squamous cell carcinoma. In this study, we investigated whether SMYD2 is a possible oncogene and a prognostic indicator in HPV-unrelated, multiple and nonmultiple HNSCC. Among 197 HPV-unrelated HNSCC cases, overexpression of SMYD2 protein was detected in 75 (60%) of 126 nonmultiple cases and 51 (70%) of 71 multiple cases. In nonmultiple cases, patients with SMYD2-overexpressing tumors had a worse overall survival rate than did those with nonexpressing tumors (P =.017, log-rank test), and SMYD2 positivity was independently associated with overall survival in the multivariate analysis (P =.003). In both nonmultiple and multiple groups, the combination of SMYD2 and p53 immunopositivity was a significant prognostic indicator (P =.027 and.015). In 5 HNSCC cell lines, overexpression of SMYD2 messenger RNA and protein was observed, but there was no notable amplification at 1q32-41.1. The proliferation of UM-SCC-17B HPV-unrelated HNSCC cell line was inhibited by knockdown of SMYD2 gene expression. These findings suggest that SMYD2 plays a role in tumor progression and might be a useful prognosticator in HPV-unrelated, nonmultiple HNSCC.