PGD and hepatocellular carcinoma: PPP is an alternative pathway of glucose catabolism, which is mainly regulated by glucose-6-phosphate dehydrogenase(G6PD), 6-phosphogluconate dehydrogenase(6PGD), transketolase (TKT), and transaldolase 1(TAL), etc. Metabolomic analysis suggested that PPP may be the most relevant pathway regulating regorafenib resistance in HCC, but its alteration was not validated.