Dynamic regulation and involvement of the heat shock transcriptional response in arsenic carcinogenesis.
The objective of this study is to better define induction of the heat shock response by arsenite, and to evaluation if induction of heat shock proteins (HSPs) contributes to the carcinogenic activity of arsenite. We show here that arsenite is a ubiquitous inducer of the heat shock response in mammalian cells: that it activated heat shock transcription factor 1 (HSF1) DNA-binding activity, enhanced hsp 70 promoter, and induced hsp70mRNA and synthesis of HSP chaperones. Using a high throughput hsp70 promoter-luciferase reporter assay, we observed a hormetic dose response where low concentrations of arsenite stimulated and high concentrations inhibited. Further, the response was time-dependent such that with longer times of incubation, the dose response shifted to the left. The effect of arsenite in inducing the hsp 70-luciferase reporter absolutely required a functional HSF1 as it was not observed in HSF1 minus cells but re-instated by expression of HSF1. Consistent with the suggestion that arsenic targets vicinal cysteine-SH, we showed that dithiothreitol blocked the effect of arsenite. Assays of cell viability and caspase showed that arsenite caused a dose-dependent increase in cell death by activation of caspase 3/7 and pre-induction of HSPs blunted these effects. Using anchorage independent cell growth as a late stage tumor promotion assay, we showed that low concentrations of arsenite had a growth promoting effect, which was enhanced by moderate heat shock. Our study provides evidence that induction of the heat shock response is a sensitive biomarker of arsenic exposure and that induction of HSPs likely contributes to the tumor promotion effect of arsenic.
Khalil
Sara
S
Rutgers College, Rutgers State University of New Jersey, Piscataway, New Jersey 08854, USA.
Luciano
Jason
J
Chen
Wenjun
W
Liu
Alice Y-C
AY
D000818:Animals; D018053:Arsenites / Q000633:toxicity*; D053148:Caspase 3; D053179:Caspase 7; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D002461:Cell Line, Transformed; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D004229:Dithiothreitol / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D000076249:Heat Shock Transcription Factors; D018869:Heat-Shock Response / Q000187:drug effects*; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D041681:NIH 3T3 Cells; D009369:Neoplasms / Q000139:chemically induced* / Q000235:genetics / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000494:pharmacology; D014157:Transcription Factors / Q000172:deficiency / Q000235:genetics / Q000378:metabolism
D018053:Arsenites; D004268:DNA-Binding Proteins; D018840:HSP70 Heat-Shock Proteins; D000076249:Heat Shock Transcription Factors; C490017:Hsf1 protein, mouse; D013438:Sulfhydryl Compounds; D014157:Transcription Factors; C505407:CASP3 protein, human; C505520:CASP7 protein, human; C505409:Casp3 protein, mouse; C505524:Casp7 protein, mouse; D053148:Caspase 3; D053179:Caspase 7; D020169:Caspases; C015001:arsenite; D004229:Dithiothreitol