RBM24 Mediates Lymph Node Metastasis and Epithelial-Mesenchymal-Transition in Human Hypopharyngeal Squamous Cell Carcinoma Via Regulating Twist1

Background: Hypopharyngeal squamous cell carcinoma (HSCC) has the worst prognosis among head and neck tumours, and Lymph node (LN) metastasis mainly accounts for the poor prognosis. RBM24 (RNA Binding Motif Protein 24) regulates target RNA as an RNA binding protein involved in several cancers. However, its role in HSCC remains completely unknown. Here we attempt to explore the effects of RBM24 on HSCC. Methods: : RNA sequencing was conducted to find the differentially expressed genes in tumour tissues from HSCC patients with LN metastasis and without LN metastasis in our previous study. Expression of RBM24 in HSCC tissues was analyzed by qRT-PCR, western blot and immunohistochemistry. Cell proliferation was tested by CCK8 assay as well as Colony formation analysis. Cell migration and invasion capacity were estimated by transwell assay. The wound healing assay was also carried out to evaluate the motility of FaDu cells. QRT-PCR, western blot and immunofluorescence assays were conducted to detect the process of EMT. A popliteal lymph node metastasis model was constructed to explore the effect of RBM24 on HSCC in vivo. Results: : RBM24 was remarkably down-regulated in HSCC patients with LN metastasis, and low expression of RBM24 was inextricably linked to the poor prognosis. Knockdown of RBM24 facilitated the proliferation, migration and invasion of RBM24, whereas overexpression of RBM24 showed the opposite effects and suppressed the epithelial-mesenchymal-transition (EMT) process. Overexpression of Twist1 could reverse the inhibitory effects of RBM24 on motility and invasion of FaDu cells. The inhibitory effects of RBM24 on tumour growth and lymphatic metastasis in HSCC were demonstrated by the in vivo experiment as well. Conclusions: : These results indicated RBM24 was a suppressor gene and might inhibit EMT and LN metastasis in HSCC via regulating Twist1.