TXN and cancer: Although we have not been able to find in the published literature an experimental value for the in vivo lifetime of E. coli thioredoxin, a lifetime of a few days or so seems entirely plausible, as many proteins show lifetimes in this range [51–54] and, in fact, for some “thioredoxin-like” proteins, in vivo lifetimes of about one day have been reported [52] and a somewhat smaller lifetime (~7 hours) has been reported for a thioredoxin in human cancer cells [70].