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National Institute of Environmental Health Sciences

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Publication Detail

Title: Glutathione S-transferase P1-1 expression modulates sensitivity of human kidney 293 cells to photodynamic therapy with hypericin.

Authors: Dabrowski, Michael J; Maeda, Dean; Zebala, John; Lu, Weiya Doug; Mahajan, Sumit; Kavanagh, Terrance J; Atkins, William M

Published In Arch Biochem Biophys, (2006 May 15)

Abstract: Photodynamic therapy (PDT) relies on light-dependent, tissue-targeted, oxidative stress in tumors that have accumulated a photosensitizing drug. Glutathione S-transferases (GSTs) are often up-regulated in tumors and they modulate oxidative stress by several isoform-dependent mechanisms. GSTs, therefore, are potential confounding factors in PDT. Therefore, we examined this possibility in human kidney 293 cells transfected with a plasmid encoding either green fluorescent protein alone (pIRES-GFP) or both GFP and GSTP1-1 (pIRES-GFP-GSTP). Cells were cultured and treated with light alone, the sensitizer hypericin (HYP) alone, or light and HYP. Cells harboring pIRES-GFP-GSTP exhibited a modest 2-fold increase in GSTP1-1 expression over control cells. On the basis of flow cytometry and microscopy, the light-dependent toxicity of HYP was reduced in cells over-expressing GSTP1-1. Paradoxically, the decreased toxicity in the cells with GSTP1-1 over-expression occurred concomitantly with a modest approximately 2-fold increase in cellular uptake of the drug. Immunoprecipitation of HYP and Western analysis indicated that GSTP1-1 is a major intracellular-binding site for HYP. These results are the first to demonstrate GST expression as a confounding variable of photodynamic therapy. Further, a high-affinity GST inhibitor reversed the GSTP1-1-dependent resistance, suggesting the possible utility of pharmacological strategies to optimize PDT.

PubMed ID: 16546115 Exiting the NIEHS site

MeSH Terms: Apoptosis/drug effects*; Apoptosis/radiation effects*; Cell Line; Glutathione Transferase/genetics; Glutathione Transferase/metabolism*; Humans; Kidney/cytology; Kidney/drug effects*; Kidney/enzymology*; Kidney/radiation effects; Light; Perylene/administration & dosage; Perylene/analogs & derivatives*; Photochemotherapy/methods*; Treatment Outcome

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