Abstract
Squamous cell carcinoma of the head and neck (SCCHN) is a relatively common malignancy with suboptimal long-term prognosis, thus new treatment strategies are urgently needed. Over the last decade, histone methyltransferases (HMT) have been recognized as promising targets for cancer therapy, but their mechanism of action in most solid tumors, including SCCHN, remains to be elucidated. This study investigated the role of Wolf-Hirschhorn syndrome candidate 1 (WHSC1), an NSD family HMT, in SCCHN. Immunohistochemical analysis of locoregionally advanced SCCHN, dysplastic, and normal epithelial tissue specimens revealed that WHSC1 expression and dimethylation of histone H3 lysine 36 (H3K36me2) were significantly higher in SCCHN tissues than in normal epithelium. Both WHSC1 expression and H3K36me2 levels were significantly correlated with histologic grade. WHSC1 knockdown in multiple SCCHN cell lines resulted in significant growth suppression, induction of apoptosis, and delay of the cell-cycle progression. Immunoblot and immunocytochemical analyses in SCCHN cells demonstrated that WHSC1 induced H3K36me2 and H3K36me3. Microarray expression profile analysis revealed NIMA-related kinase-7 (NEK7) to be a downstream target gene of WHSC1, and chromatin immunoprecipitation (ChIP) assays showed that NEK7 was directly regulated by WHSC1 through H3K36me2. Furthermore, similar to WHSC1, NEK7 knockdown significantly reduced cell-cycle progression, indicating that NEK7 is a key player in the molecular pathway regulated by WHSC1. Implications: WHSC1 possesses oncogenic functions in SCCHN and represents a potential molecular target for the treatment of SCCHN.