H6PD and neoplasm: Fortunately, G6PDH is an informative exception as its enzyme activity in tumours is well studied and was increased in various human cancer types when compared to the respective benign control tissue, e.g. cervix, uteri, prostate and breast (Pedersen, 1975; Zampella, Bradley & Pretlow, 1982; Bezwoda et al., 1985).