N-myristoyltransferase 1-mediated Src Myristoylation Promotes Non-receptor Tyrosine Kinase Pathways in Oral Squamous Cell Carcinoma

Background Aim: N-myristoyltransferase 1 (NMT1), which myristoylates Src, is highly expressed in oral squamous cell carcinoma (OSCC). Although targeted therapies against epidermal growth factor receptor exist, their use is limited by resistance and toxicity, and NMT1-Src interactions remain unexplored. Herein, we aimed to evaluate the role of NMT1-mediated Src myristoylation in the malignant potential of OSCC. Materials and Methods: Myristoylation and the expression of NMT1 in OSCC were assessed using click chemistry and immunocytochemistry. RNA-seq and enrichment analyses were performed to compare OSCC cells with or without NMT1-siRNA treatment. Src activity was determined by measuring Src phosphorylation via western blotting. Expression and binding of NMT1 and Src were analyzed via immunoprecipitation using specific antibodies. HSC-2, HSC-3, WK2, and WK3F derived from human OSCC in vitro were also used to confirm malignancy by siRNA of siNMT1 in OSCC cell lines. Results: NMT1 and Src expression was detected in all OSCC cell lines. RNA-seq analysis of SAS cells transfected with NMT1-siRNA revealed decreased expression of genes related to cell adhesion and angiogenesis. WK3F cells, which exhibit high malignancy, showed markedly higher NMT1 expression than other cell lines. Immunocytochemistry showed that Src membrane localization was reduced in all of the OSCC cell lines with NMT1 knockdown. Co-immunoprecipitation analysis confirmed that NMT1 was bound to Src during myristoylation. Conclusion: NMT1 promotes OSCC malignancy by mediating Src myristoylation.