Activation of PGK1 under hypoxic conditions promotes glycolysis and increases stem cell-like properties and the epithelial-mesenchymal transition in oral squamous cell carcinoma cells via the AKT signalling pathway

Abstract

Although it has been previously documented that a hypoxic environment can promote glycolysis and the malignant progression of oral squamous cell carcinoma (OSCC) cells, the specific underlying mechanism remains unclear. Phosphoglycerate kinase 1 (PGK1) has been previously reported to serve an important role in tumor metabolism. The aim of the present study was to investigate the effects of hypoxia and PGK1 on glycolysis, stem cell-like properties and epithelial-mesenchymal transition (EMT) in OSCC cells. Cell Counting Kit-8 assays were performed to examine tumor cell viability under hypoxic conditions. Sphere formation, immunohistochemistry, western blotting, Transwell assays and mouse xenograft studies were performed to assess the biological effects of PGK1. Under hypoxic conditions, phosphoglycerate PGK1 expression was found to be upregulated, which resulted in the potentiation of stem cell-like properties and enhancement of EMT. However, PGK1 knockdown reversed hypoxia-mediated glycolysis, stem cell-like properties, EMT in addition to inhibiting OSCC cell invasion and migration. PGK1 knockdown also inhibited tumour growth, whilst the overexpression of PGK1 was demonstrated to promote tumour growth in mouse xenograft models in vivo. Downstream, activation of the AKT signalling pathway reversed the series of changes induced by PGK1 knockdown. PGK1 expression was found to be upregulated in human OSCC tissues, which was associated with the pathological differentiation of tumours and lymph node metastasis. To conclude, results from the present study demonstrate that hypoxia can increase PGK1 expression, resulting in the promotion of glycolysis, enhancing stem cell-like properties and EMT by activating AKT signalling in OSCC.