The Natural Compound Cantharidin Induces Cancer Cell Death through Inhibition of Heat Shock Protein 70 (HSP70) and Bcl-2-associated Athanogene Domain 3 (BAG3) Expression by Blocking Heat Shock Factor 1 (HSF1) Binding to Promoters

• Published in: The Journal of biological chemistry Vol. 288; no. 40; pp. 28713 - 28726
• Main Authors: Kim, Joo Ae, Kim, Youngmi, Kwon, Byoung-Mog, Han, Dong Cho
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 04.10.2013; American Society for Biochemistry and Molecular Biology
• Subjects: Acetylation - drug effects; Adaptor Proteins, Signal Transducing - metabolism; Apoptosis; Apoptosis Regulatory Proteins; Bcl-2 Family Proteins; bcl-X Protein - metabolism; Cancer Therapy; Cantharidin - chemistry; Cantharidin - pharmacology; Cantharidin - therapeutic use; Cell Death - drug effects; Cell Line, Tumor; Cell Nucleus - drug effects; Cell Nucleus - metabolism; Cell Proliferation - drug effects; DNA-Binding Proteins - metabolism; Drug Screening; Drug Screening Assays, Antitumor; G2 Phase Cell Cycle Checkpoints - drug effects; G2 Phase Cell Cycle Checkpoints - genetics; Gene Expression Regulation, Neoplastic - drug effects; Heat Shock Protein; Heat Shock Transcription Factors; Heat-Shock Response - drug effects; HSP70 Heat-Shock Proteins - antagonists & inhibitors; HSP70 Heat-Shock Proteins - genetics; HSP70 Heat-Shock Proteins - metabolism; Humans; Mitosis - drug effects; Mitosis - genetics; Models, Biological; Myeloid Cell Leukemia Sequence 1 Protein - metabolism; Neoplasms - drug therapy; Neoplasms - genetics; Neoplasms - pathology; Positive Transcriptional Elongation Factor B; PP2A; Promoter Regions, Genetic - genetics; Protease Inhibitors - pharmacology; Protein Binding - drug effects; Protein Phosphatase 2 - antagonists & inhibitors; Protein Phosphatase 2 - metabolism; Protein Transport - drug effects; Proto-Oncogene Proteins c-bcl-2 - metabolism; Signal Transduction; Transcription Factors - metabolism; Cancer Therapy; Drug Screening; PP2A; Apoptosis; Bcl-2 Family Proteins; Heat Shock Protein
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M113.488346

HSF1 is a transcription factor that enhances cancer formation and progression. Results: Cantharidin inhibited the binding of HSF1 to the HSP70 promoter and subsequently blocked HSF1-dependent HSP70 expression. Conclusion: The HSF1-dependent expression of HSP70 and BAG3 is inhibited by cantharidin, causing the down-regulation of antiapoptotic BCL-2 family proteins, especially MCL-1. Significance: This information provides a new target molecule and pathway of cantharidin. Heat shock factor 1 (HSF1) enhances the survival of cancer cells under various stresses. The knock-out of HSF1 impairs cancer formation and progression, suggesting that HSF1 is a promising therapeutic target. To identify inhibitors of HSF1 activity, we performed cell-based screening with a library of marketed and experimental drugs and identified cantharidin as an HSF1 inhibitor. Cantharidin is a potent antitumor agent from traditional Chinese medicine. Cantharidin inhibited heat shock-induced luciferase activity with an IC50 of 4.2 μm. In contrast, cantharidin did not inhibit NF-κB luciferase reporter activity, demonstrating that cantharidin is not a general transcription inhibitor. When the HCT-116 colorectal cancer cells were exposed to heat shock in the presence of cantharidin, the induction of HSF1 downstream target proteins, such as HSP70 and BAG3 (Bcl-2-associated athanogene domain 3), was suppressed. HSP70 and its co-chaperone BAG3 have been reported to protect cells from apoptosis by stabilizing anti-apoptotic Bcl-2 family proteins. As expected, treating HCT-116 cancer cells with cantharidin significantly decreased the amounts of BCL-2, BCL-xL, and MCL-1 protein and induced apoptotic cell death. Chromatin immunoprecipitation analysis showed that cantharidin inhibited the binding of HSF1 to the HSP70 promoter and subsequently blocked HSF1-dependent p-TEFb recruitment. Therefore, the p-TEFb-dependent phosphorylation of the C-terminal domain of RNA polymerase II was blocked, arresting transcription at the elongation step. Protein phosphatase 2A inhibition with PP2CA siRNA or okadaic acid did not block HSF1 activity, suggesting that cantharidin inhibits HSF1 in a protein phosphatase 2A-independent manner. We show for the first time that cantharidin inhibits HSF1 transcriptional activity.