Chemoprotection against cancer by phase 2 enzyme induction

Toxicol Lett. 1995 Dec;82-83:173-9. doi: 10.1016/0378-4274(95)03553-2.


Mammalian cells have evolved elaborate mechanisms for protection against the toxic and neoplastic effects of electrophilic metabolites of carcinogens and reactive oxygen species. Phase 2 enzymes (e.g. glutathione transferase, NAD(P)H:quinone reductase, UDP-glucuronosyltransferases) and high intracellular levels of glutathione play a prominent role in providing such protection. Phase 2 enzymes are transcriptionally induced by low concentrations of a wide variety of chemical agents and such induction blocks chemical carcinogenesis. The inducers belong to many chemical classes including phenolic antioxidants. Michael reaction acceptors, isothiocyanates, 1,2-dithiole-3-thiones, trivalent arsenicals, HgCl2 and organomercurials, hydroperoxides, and vicinal dimercaptans. Induction by all classes of inducers involves the antioxidant/electrophile response element (ARE/EpRE). Inducers are widely, but unequally, distributed among edible plants. Search for such inducer activity in broccoli led to the isolation of sulforaphane, an isothiocyanate that is a very potent Phase 2 enzyme inducer and blocks mammary tumor formation in rats.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.
  • Review

MeSH terms

  • Animals
  • Anticarcinogenic Agents / pharmacology*
  • Enzyme Induction / drug effects*
  • Glutathione Transferase / biosynthesis
  • NAD(P)H Dehydrogenase (Quinone) / biosynthesis
  • Neoplasms / prevention & control*
  • Plants / chemistry
  • Rats


  • Anticarcinogenic Agents
  • NAD(P)H Dehydrogenase (Quinone)
  • Glutathione Transferase