Although Li et al. reported that EGCG has no effect on ATP binding to HSP90 [13], several studies have reported that EGCG interacts with the ATPase domain of HSP90 and Grp78 and inhibits their functions by competing with ATP for binding to the ATP binding domain in hepatoma and pancreatic cancer cells [12,14]. This evidence concerns the gene HSPA5 and familial pancreatic carcinoma.