DLEU2 promotes proliferation and glycolysis of oral squamous cell carcinoma by regulating SIX1

Abstract

Abstract Objective To look into the physiological functions of the lncRNA DLEU2 in the tumorigenesis of oral squamous cell carcinoma (OSCC), as well as whether it plays a role in the emergence and advancement of OSCC by governing SIX1. Methods The inhibitory role of DLEU2 on the proliferation of SCC-15 cells was examined by CCK8. Flow cytometry was used to study the influence of DLEU2 inhibitory activity on SCC-15 apoptotic cell death. In addition, trans-well assays were used to analyze the influence of DLEU2 suppression on SCC-15 cell differentiation and proliferation. Results The DLEU2 expression in OSCC cancerous specimens was considerably stronger than the corresponding healthy tissues; and DLEU2 was elevated in all four OSCC cells. The immunohistochemistry data also showed the level of DLEU2 was also greatly elevated in OSCC tissues than healthy specimens. After transfection of si-DLEU2, the viability of SCC-15 cells decreased significantly. Additionally, the number of apoptosis cells transfected with si-DLEU2 was significantly higher than controls. Using trans-well invasion assay, the data suggested the number of invasive cells formed by blocking DLEU2 of SCC-15 and SCC-25 cells was markerly lower than the controls. The results of ECAE and OCR also showed that DLEU2 could promote the glycolysis of OSCC cells while inhibit the oxidative phosphorylation progress of OSCC cells. Our subsequent analysis of the main enzymes affecting glycolysis, GLUT1 and HK2, showed that blocking expression of DLEU2 is able to obviously reduce the GLUT1 level, but not HK2. Subsequent ChIP experiments confirmed that SIX1 could bind to the promoter of GLUT1, and knocking down DLEU2 could reduce the binding ability of SIX1 to the promoter of GLUT1. Finally, we utilized luciferase assays to confirm that knockdown of DLEU2 expression could directly reduce GLUT1 transcript levels. The results of ECAR and OCR experiments also showed that overexpression of SIX1 could reverse the decreased glycolysis of OSCC cells brought down by knockdown of DLEU2. Conclusion DLEU2 is essential for OSCC tumorigenesis, migratory and glycogenolysis. The DLEU2/SIX1 role is implicated in OSCC cell invasion and aerobic glycolysis.