Prolyl hydroxylase 2 inhibits glycolytic activity in colorectal cancer via the NF-B signaling pathway

A variety of malignancies preferentially meet energy demands through the glycolytic pathway. Hypoxia-induced cancer cell adaptations are essential for tumor development. However, in cancerous glycolysis, the functional importance and underlying molecular mechanism of prolyl hydroxylase domain protein 2 (PHD2) have not been fully elucidated. Gain- and loss-of-function assays were conducted to evaluate PHD2 functions in colon cancer cells. Glucose uptake, lactate production and intracellular adenosine-5'-triphosphate/adenosine diphosphate ratio were measured to determine glycolytic activities. Protein and gene expression levels were measured by western blot analysis and reverse transcription-quantitative PCR, respectively. The human colon cancer xenograft model was used to confirm the role of PHD2 in tumor progression in vivo. Functionally, the data demonstrated that PHD2 knockdown leads to increased glycolysis, while PHD2 overexpression resulted in suppressed glycolysis in colorectal cancer cells. In addition, the glycolytic activity was enhanced without PHD2 and normalized after PHD2 reconstitution. PHD2 was shown to inhibit colorectal tumor growth, suppress cancer cell proliferation and improve tumor-bearing mice survival in vivo. Mechanically, it was found that PHD2 inhibits the expression of critical glycolytic enzymes (glucose transporter 1, hexokinase 2 and phosphoinositide-dependent protein kinase 1). In addition, PHD2 inhibited Ikk beta-mediated NF-kappa B activation in a hypoxia-inducible factor-1 alpha-independent manner. In conclusion, the data demonstrated that PHD2/Ikk beta/NF-kappa B signaling has critical roles in regulating glycolysis and suggests that PHD2 potentially suppresses colorectal cancer.