H6PD and cancer: Investigating the divergent MTF effects on FDG retention and glucose consumption brought us to discover that tumor FDG uptake is largely independent from overall glucose utilization and tracks a novel monosaccharide metabolism that is triggered by hexose-6-phosphate dehydrogenase (H6PD) within the lumen of endoplasmic reticulum (ER), is fueled by glucose at high rates and is strictly related to cancer growth and aggressiveness.