DNA-dependent protein kinase is inhibited by trifluoperazine

Biochem Biophys Res Commun. 2001 May 18;283(4):726-31. doi: 10.1006/bbrc.2001.4830.


The DNA-dependent protein kinase (DNA-PK) is a serine/threonine nuclear kinase, important for the repair of DNA double strand breaks (DSB). Cells defective in DNA-PK show increased sensitivity to ionising radiation and different DNA-damaging drugs, such as cisplatinum. Increased sensitivity to cisplatinum has previously been noted in the presence of phenothiazines. We tested a panel of phenothiazines and one thioxanthen for any influence upon the activity and expression of DNA-PK in a nonsmall cell lung cancer cell line, U-1810. The activity of DNA-PK was completely inhibited in cell lysate and in purified enzyme by 200 microM TFP. DNA-PKcs and Ku86 cleavage were evident in U-1810 cells after 30 min incubation with 100 microM TFP, along with changes in the cells consistent with apoptosis. Our study suggests that phenothiazines and thioxanthens, acting through DNA-PK, have the potential to enhance the effects of DNA damaging agents.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Blotting, Western
  • Cell Extracts
  • DNA-Activated Protein Kinase
  • DNA-Binding Proteins*
  • Enzyme Inhibitors / pharmacology*
  • Humans
  • Lung Neoplasms / enzymology
  • Lung Neoplasms / pathology
  • Nuclear Proteins
  • Protein-Serine-Threonine Kinases / antagonists & inhibitors*
  • Trifluoperazine / pharmacology*
  • Tumor Cells, Cultured


  • Cell Extracts
  • DNA-Binding Proteins
  • Enzyme Inhibitors
  • Nuclear Proteins
  • Trifluoperazine
  • DNA-Activated Protein Kinase
  • PRKDC protein, human
  • Protein-Serine-Threonine Kinases