TKT and neoplasm: Furthermore, several natural products have been reported to inhibit transketolase enzyme activity in vitro, and also to inhibit cell proliferation or suppress tumour growth in mouse models or cancer patients as a result of reduction of transketolase activity (Hidvegi et al, 1999; Boros et al, 2001a, 2001b; Comin-Anduix et al, 2002; Jakab et al, 2003).