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Biochem Biophys Res Commun. 2001 May 18;283(4):726-31.

DNA-dependent protein kinase is inhibited by trifluoperazine.

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Division of Medical Radiation Biology, Karolinska Hospital, Stockholm, SE-171 76, Sweden.

Erratum in

  • Biochem Biophys Res Commun 2001 Jun 22;284(4):1091. Nilsso A [corrected to Nilsson A].


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.

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