Quinone toxicity in DT-diaphorase-efficient and -deficient colon carcinoma cell lines

Biochem Pharmacol. 1999 Jan 1;57(1):27-37. doi: 10.1016/s0006-2952(98)00288-3.


The human colon carcinoma cell lines Caco-2 and HT-29 were exposed to three structurally related naphthoquinones. Menadione (MEN), 1,4-naphthoquinone (NQ), and 2,3-dimethoxy-1,4-naphthoquinone (DIM) redoxcycle at similar rates, NQ is a stronger arylator than MEN, and DIM does not arylate thiols. The Caco-2 cell line was particularly vulnerable to NQ and MEN and displayed moderate toxic effects of DIM. The HT-29 cell line was only vulnerable to NQ and MEN after inhibition of DT-diaphorase (DTD) with dicoumarol, whereas dicoumarol did not affect the toxicity of quinones to Caco-2 cells. DTD activity in the HT-29 and Caco-2 cell lines, as estimated by the dicoumarol-sensitive reduction of 2,6-dichlorophenolindophenol, was 393.7 +/- 46.9 and 6.4 +/- 2.2 nmol NADPH x min(-1) x mg protein(-1), respectively. MEN depleted glutathione to a small extent in the HT-29 cell line, but a rapid depletion similar to Caco-2 cells was achieved when dicoumarol was added. The data demonstrated that the DTD-deficient Caco-2 cell line was more vulnerable to arylating or redoxcycling quinones than DTD-expressing cell lines. Exposure of the Caco-2 cell line to quinones produced a rapid rise in protein disulphides and oxidised glutathione. In contrast to NQ and DIM, no intracellular GSSG was observed with MEN. The relatively higher levels of ATP in MEN-exposed cells may account for the efficient extrusion of intracellular GSSG. The reductive potential of the cell as measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide reduction was only increased by MEN and not with NQ and DIM. We conclude that arylation is a major contributing factor in the toxicity of quinones. For this reason, NQ was the most toxic quinone, followed by MEN, and the pure redoxcycler DIM elicited modest toxicity in Caco-2 cells.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Cell Survival / radiation effects*
  • Colonic Neoplasms
  • Dicumarol / pharmacology
  • Glutathione / metabolism
  • Glutathione Disulfide / metabolism
  • Humans
  • Kinetics
  • NAD(P)H Dehydrogenase (Quinone) / deficiency
  • NAD(P)H Dehydrogenase (Quinone) / metabolism*
  • Naphthoquinones / toxicity*
  • Neoplasm Proteins / metabolism
  • Sulfhydryl Compounds / metabolism
  • Tumor Cells, Cultured
  • Vitamin K / toxicity


  • Naphthoquinones
  • Neoplasm Proteins
  • Sulfhydryl Compounds
  • Vitamin K
  • 2,3-dimethoxy-1,4-naphthoquinone
  • Dicumarol
  • Adenosine Triphosphate
  • NAD(P)H Dehydrogenase (Quinone)
  • Glutathione
  • 1,4-naphthoquinone
  • Glutathione Disulfide