Adaptation to HIF1α deletion in hypoxic cancer cells by upregulation of GLUT14 and creatine metabolism.

Hypoxia-inducible factor 1α is a key regulator of the hypoxia response in normal and cancer tissues. It is well recognised to regulate glycolysis and is a target for therapy. However, how tumour cells adapt to grow in the absence of HIF1α is poorly understood and important to understand for developing targeted therapies and the flexibility of the metabolic response to hypoxia via alternative pathways. We analysed pathways that allow cells to survive hypoxic stress in the absence of HIF1α, using the HCT116 colon cancer cell line with deleted HIF1α versus control. Spheroids were used to provide a 3D model of metabolic gradients. We conducted a metabolomic, transcriptomic and proteomic analysis and integrated the results. These showed surprisingly that in three-dimensional growth a key regulatory step of glycolysis is Aldolase A rather than phosphofructokinase. Furthermore, glucose uptake could be maintained in hypoxia through upregulation of GLUT14, not previously recognised in this role. Finally, there was a marked adaptation and change of phosphocreatine energy pathways, which made the cells susceptible to inhibition of creatine metabolism in hypoxic conditions. Overall, our studies show a complex adaptation to hypoxia that can bypass HIF1α, but is targetable and it provides new insight into the key metabolic pathways involved in cancer growth. Implications: Under hypoxia and HIF1 blockade, cancer cells adapt their energy metabolism via upregulation of the GLUT14 glucose transporter and creatine metabolism providing new avenues for drug targeting.