Article

HSP70 Inhibition by the Small-Molecule 2-Phenylethynesulfonamide Impairs Protein Clearance Pathways in Tumor Cells

Department of Genetics, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
Molecular Cancer Research (Impact Factor: 4.5). 06/2011; 9(7):936-47. DOI: 10.1158/1541-7786.MCR-11-0019
Source: PubMed

ABSTRACT The evolutionarily conserved stress-inducible HSP70 molecular chaperone plays a central role in maintaining protein quality control in response to various forms of stress. Constitutively elevated HSP70 expression is a characteristic of many tumor cells and contributes to their survival. We recently identified the small-molecule 2-phenylethyenesulfonamide (PES) as a novel HSP70 inhibitor. Here, we present evidence that PES-mediated inhibition of HSP70 family proteins in tumor cells results in an impairment of the two major protein degradation systems, namely, the autophagy-lysosome system and the proteasome pathway. HSP70 family proteins work closely with the HSP90 molecular chaperone to maintain the stability and activities of their many client proteins, and PES causes a disruption in the HSP70/HSP90 chaperone system. As a consequence, many cellular proteins, including known HSP70/HSP90 substrates, accumulate in detergent-insoluble cell fractions, indicative of aggregation and functional inactivation. Overall, PES simultaneously disrupts several cancer critical survival pathways, supporting the idea of targeting HSP70 as a potential approach for cancer therapeutics.

0 Followers
 · 
169 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Aerobic metabolism of mammalian cells leads to the generation of reactive oxygen species (ROS). To cope with this toxicity, evolution provided cells with effective antioxidant systems like glutathione. Current anticancer therapies focus on the cancer dependence on oncogenes and non-oncogenes. Tumours trigger mechanisms to circumvent the oncogenic stress and to escape cell death. In this context we have studied 2-phenylethinesulfoxamine (PES), which disables the cell protective mechanisms to confront the proteotoxicity of damaged and unfolded proteins. Proteotoxic stress is increased in tumour cells, thus providing an explanation for the anticancer selectivity of PES. In addition, we have found that PES induces a severe oxidative stress and the activation of p53. The cell content reduction of glutathione by means of L-buthionine-sulfoximine (BSO) synergizes with PES. In conclusion, we have found that ROS constitutes a central element in a series of positive feed-backs in the cell. ROS, p53, proteotoxicity, autophagy, mitochondrial dynamics are interconnected with the mechanisms leading to cell death, either apoptotic or necrotic. This network of interactions provides multiple targets for drug discovery and development in cancer.
    Current Drug Targets 11/2014; 16(1). DOI:10.2174/1389450115666141114153536
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The effect of 2-phenylethynesulfonamide (PES), which is a p53 and HSP70 inhibitor in mammalian cells, was studied on the rainbow trout (Oncorhynchus mykiss) gill epithelial cell line, RTgill-W1, in order to evaluate PES as a tool for understanding the cellular survival pathways operating in fish. As judged by three viability assays, fish cells were killed by 24h exposures to PES, but cell death was blocked by the anti-oxidant N-acetylcysteine (NAC). Cell death had several hallmarks of apoptosis: DNA laddering, nuclear fragmentation, Annexin V staining, mitochondrial membrane potential decline, and caspases activation. Reactive oxygen species (ROS) production peaked in several hours after the addition of PES and before cell death. HSP70 and BiP levels were higher in cultures treated with PES for 24h, but this was blocked by NAC. As well, PES treatment caused HSP70, BiP and p53 to accumulate in the detergent-insoluble fraction, and this too was prevented by NAC. Of several possible scenarios to explain the results, the following one is the simplest. PES enhances the generation of ROS, possibly by inhibiting the anti-oxidant actions of p53 and HSP70. ER stress arises from the ROS and from PES inhibiting the chaperone activities of HSP70. The ER stress in turn initiates the unfolded protein response (UPR), but this fails to restore ER homeostasis so proteins aggregate and cells die. Despite these multiple actions, PES should be useful for studying fish cellular survival pathways.
    Aquatic toxicology (Amsterdam, Netherlands) 11/2013; 146C:45-51. DOI:10.1016/j.aquatox.2013.10.026
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Heat shock proteins (HSP) are a subset of the molecular chaperones, best known for their rapid and abundant induction by stress. HSP genes are activated at the transcriptional level by heat shock transcription factor 1 (HSF1). During the progression of many types of cancer, this heat shock transcriptional regulon becomes co-opted by mechanisms that are currently unclear, although evidently triggered in the emerging tumor cell. Concerted activation of HSF1 and the accumulation of HSPs then participate in many of the traits that permit the malignant phenotype. Thus, cancers of many histologies exhibit activated HSF1 and increased HSP levels that may help to deter tumor suppression and evade therapy in the clinic. We review here the extensive work that has been carried out and is still in progress aimed at (1) understanding the oncogenic mechanisms by which HSP genes are switched on, (2) determining the roles of HSF1/HSP in malignant transformation and (3) discovering approaches to therapy based on disrupting the influence of the HSF1-controlled transcriptome in cancer.
    Archives of Toxicology 08/2012; 87(1). DOI:10.1007/s00204-012-0918-z

Preview

Download
0 Downloads
Available from