TIMELESS promotes reprogramming of glucose metabolism in oral squamous cell carcinomas

Background Oral squamous cell carcinoma (OSCC) is the most common malignant of the oral cavity, with a high prevalence and a poor survival rate. There have been studies that indicate circadian disruption has been related to many biological processes within the body and contributes to different diseases, including cancer. Circadian gene TIMELESS is strongly expression-specific in various tumors, but there are very few studies on TIMELESS and OSCC in the literature. The goal of this research is to inquire the impact of TIMELESS on cell growth and glucose metabolism in OSCC. Methods Expression of TIMELESS in OSCC cell lines and tissues was analyzed by western blot, immunohistochemical (IHC) staining, quantitative real-time PCR (qRT-PCR), TCGA (The Cancer Genome Atlas) and CCLE (Cancer Cell Line Encyclopedia) databases. To evaluate the role of TIMELESS in OSCC, the clone formation experiment, MTS assay, cell cycle assay, EdU experiment and subcutaneous tumor formation experiment in nude mice were employed to detect the cell proliferation. Changes in glucose metabolism phenotype were evaluated by glucose uptake, lactate production, oxygen consumption and medium pH to determine if the phenotypes were linked to TIMELESS, the effect of TIMELESS on SIRT1, HK2, PKM2, GLUT1 and LDHA was also examined. Results Our results demonstrated that the obvious elevation of TIMELESS in OSCC tissues and cell lines, high expression of TIMELESS was conferred shorter overall survival of patients. TIMELESS overexpression promoted OSCC cells proliferation, increased glucose uptake and lactate production, decreased oxygen consumption rate and pH. Whereas the knockdown of TIMELESS remarkably inhibited OSCC cell proliferation both in vitro and in vivo, reduced glucose uptake and lactate production, increased oxygen consumption rate and pH, while overexpression of SIRT1 showed a reversed trend. Correlation analysis demonstrated that expression of SIRT1 was positively associated with TIMELESS expression, and the expression of SIRT1, HK2, PKM2, GLUT1 and LDHA could change with the variation of TIMELESS in OSCC cells. Conclusion TIMELESS promotes OSCC cell growth by promoting glycolysis and inhibiting oxidative phosphorylation through SIRT1.