EMILIN1 suppresses cell proliferation by inactivating Aurora Kinase and cell cycle regulator in head and neck squamous cell carcinoma

The extracellular matrix (ECM) proteins play an important role in the physiological and pathological processes of tumor development and progression. EMILIN1 (Elastic Microfibril Interface Located ProteIN-1), a homotrimeric ECM glycoprotein, has been reported to be associated with cell adhesion and migration. We previously identified downregulated-EMILIN1 as a prognostic biomarker for secondary primary malignancy in head and neck squamous cell carcinoma (HNSCC). We hypothesized that EMILIN1 functions as a tumor suppressor in HNSCC. In this study, we overexpressed exogenous EMILIN1 expression in the FaDu and CAL27 cell lines and knockdown EMILIN1 expression in both HNSCC Cancer-Associated Fibroblast (CAF) and normal fibroblast cells. Our results showed that EMILIN1 overexpression decreased cell proliferation, cell migration, and cell invasion in FaDu and CAL27 cells. Knockdown EMILIN1 in CAFs also induced cell proliferation and migration. RNA-sequencing analysis revealed the cell cycle and Aurora kinase signaling as the most significant enrichment pathways, and we then confirmed this finding at the protein level. Furthermore, we studied the effect of EMILIN1 on tumor development in vivo using chick chorioallantoic membrane (CAM) assay. EMILIN1overexpression reduced tumor area, Ki67-positive cells, and increased cleaved caspase-3 apoptotic cells. These findings suggest the tumor suppressing role of EMILIN1 in HNSCC through the inactivation of cell cycle pathway and Aurora kinase signaling. To the best of our knowledge, this is the first study to show that Aurora kinases are the key players in EMILIN1 tumor suppressive functions in head and neck cancer cells.