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Updated: Jul 24, 2026
Intracellular Refolding Assay
Published on: January 24, 2012
Inhibitory effect of a naphthazarin derivative, S64, on heat shock factor (Hsf) activation and glutathione status
1Division of Chemistry and Biology, University of Incheon, Korea. young-mee.park@roswellpark.org
Abstract:
The presence of hypoxic cells in solid tumors has long been considered a problem in cancer treatment. Resistance of hypoxic cells to ionizing radiation and anticancer drugs has in part been attributed to changes in altered gene expression by hypoxia. We previously reported an activation of heat shock factor (Hsf) in murine tumor RIF cells following hypoxia and suggested that a subsequent accumulation of heat shock protein(s) (Hsp) is likely to contribute to the malignant progression of hypoxic tumor cells (Baek et al., 2001). In this study, we showed that hypoxia induced a DNA-binding activity of Hsf and activation of hsp70 gene expression in colon cancer Clone A cells, and that a naphthazarin derivative, S64, significantly inhibited the hypoxia-inducible hsp70 gene expression in Clone A cells. We also showed that S64 significantly reduced the cellular glutathione levels in this cell line. Considering the proposed effects of Hsp and glutathione on radiation and chemotherapy sensitivity, we suggest that the inhibitory effects of S64 on Hsf activation and cellular glutathione levels have potentially important clinical implications. We believe that the previously reported in vitro and in vivo anti-tumor effect of S64 (Song et al., 2000a, 2001) might be attributed, at least in part, to its effect on Hsf activation and/or glutathione depletion. We also believe that the detailed molecular mechanisms underlying the effects of S64 on Hsf and glutathione level following hypoxia deserve a more rigorous future study, the results of which could offer novel strategy to manipulate the resistance mechanisms of solid tumors.
Insights
Hypoxia in tumors triggers heat shock factor (Hsf) activation and heat shock protein (Hsp) expression, contributing to cancer resistance. A compound, S64, inhibits this Hsf activation and reduces glutathione, potentially improving cancer treatment efficacy.
Area of Science:
- Oncology
- Molecular Biology
- Biochemistry
Background:
- Hypoxic cells in solid tumors pose a significant challenge to cancer treatment due to resistance to radiation and chemotherapy.
- Hypoxia-induced alterations in gene expression, including heat shock factor (Hsf) activation and subsequent heat shock protein (Hsp) accumulation, are implicated in malignant progression.
- Previous research indicated Hsf activation in hypoxic murine tumor cells.
Purpose of the Study:
- To investigate the effect of hypoxia on Hsf activation and hsp70 gene expression in colon cancer Clone A cells.
- To evaluate the inhibitory potential of a naphthazarin derivative, S64, on hypoxia-induced hsp70 expression and its effect on cellular glutathione levels.
- To explore the potential clinical implications of S64's effects on Hsf activation and glutathione in the context of cancer therapy.
Main Methods:
- Exposure of colon cancer Clone A cells to hypoxic conditions.
- Assessment of hypoxia-inducible heat shock factor (Hsf) DNA-binding activity.
- Measurement of hsp70 gene expression levels.
- Treatment with the naphthazarin derivative S64.
- Quantification of cellular glutathione levels.
Main Results:
- Hypoxia induced Hsf DNA-binding activity and hsp70 gene expression in colon cancer Clone A cells.
- S64 significantly inhibited hypoxia-inducible hsp70 gene expression in these cells.
- S64 treatment led to a significant reduction in cellular glutathione levels.
- These findings suggest a link between S64's effects on Hsf and glutathione and its previously reported anti-tumor activity.
Conclusions:
- S64 effectively inhibits hypoxia-induced Hsf activation and hsp70 gene expression in colon cancer cells.
- S64 reduces cellular glutathione levels, a factor potentially influencing chemo- and radio-sensitivity.
- The dual action of S64 on Hsf and glutathione suggests a promising therapeutic strategy for overcoming solid tumor resistance mechanisms.
- Further research into the molecular mechanisms of S64 is warranted to optimize its clinical application in cancer treatment.
