H6PD and cancer: Nevertheless, this classical model has been challenged by a series of studies documenting a strict link between FDG accumulation and H6PD catalytic function in cancer [6,8], in nervous tissue [7], in the skeletal muscle [5], and in the myocardium [11] that configured tracer accumulation as an index of ER-PPP activity and, thus, of the regeneration rate of NADPH reductive power within the reticular lumen.