RPIA and cancer: The PI3K/AKT and mTORC1 signaling pathways can upregulate the expression of key rate-limiting enzymes, glucose-6-phosphate dehydrogenase (G6PD) and ribose-5-phosphate isomerase A (RPIA), by inducing the activation of SREBP1, thereby fulfilling the metabolic demands of cancer cells for nucleotides and redox homeostasis (Simcox and Lamming, 2022).