The Tumour-Suppressive Role of Myosin Heavy Chain 9 (MYH9) in Oral Squamous Cell Carcinoma

Introduction and aims Myosin heavy chain-9 (MYH9) has been implicated in cancer progression, but whether it functions as an oncogene or a tumour suppressor gene remains obscure and somewhat paradoxical. This study aimed to determine the precise role of MYH9 in oral squamous cell carcinoma (OSCC) and explore its relationship with cancer stemness characteristics. Methods MTT, colony formation and transwell migration and invasion assays were used to examine the effect of MYH9 expression on the proliferation and motility of OSCC cells, respectively. Sphere formation, real-time PCR and immunoblot were performed to assess the impact of MYH9 on the stem cell-like properties (stemness) of the cells. The tumour-suppressive role of MYH9 was verified using mouse xenograft model and immunohistochemistry. Results MYH9 expression could inhibit in vitro proliferation, colony formation, motility and chemotherapy resistance in OSCC cells. Besides, MYH9 could negatively regulate the stemness of the cells, potentially contributing to the markedly enhanced in vivo tumourigenesis when being knocked down. Furthermore, we showed that MYH9 was significantly downregulated in tumour tissues compared to the corresponding adjacent non-tumour tissues in 24 OSCC patients ( P < .05). Conclusion Using models of cell lines, mouse xenograft and clinical samples, we have comprehensively demonstrated for the first time that MYH9 plays a tumour-suppressive role in OSCC presumably via modulating cancer stemness. The present results warrant further mechanistic investigation. Clinical relevance Our findings highlight a novel tumour-suppressive biomarker and translational implications for OSCC.