tems. In cancer, most immunotherapeutical approaches based on extracellular HSPs exploit their carrier function for immunogenic peptides. This review will focus on the roles of HSP70 and HSP90 in apoptosis and in innate immunity and how these functions are being exploited in cancer therapy.

No abstract

Heat shock proteins (HSPs) are chaperones that catalyze the proper folding of nascent proteins and the refolding of denatured proteins. The ubiquitin-proteasome system is an error-checking system that directs improperly folded proteins for destruction. A coordinated interaction between the HSPs (renaturation) and the proteasome (degradation) must exist to assure protein quality control mechanisms. Although it still remains unknown how the decision of folding vs. degradation is taken, many pieces of evidence demonstrate that HSPs interact directly or indirectly with the proteasome, assuring quite selectively the proteasomal degradation of certain proteins under stress conditions. In this review, we will describe the different data that demonstrate a role for HSP90, HSP70, HSP27, and alpha-B-crystallin in the partitioning of proteins to either one of these pathways, referred as protein triage.

No abstract

Idiopathic pulmonary fibrosis (IPF) is a devastating disease characterized by myofibroblast proliferation. Transition of epithelial/mesothelial cells into myofibroblasts [epithelial-to-mesenchymal transition (EMT)] occurs under the influence of transforming growth factor (TGF)-β1, with Snail being a major transcription factor. We study here the role of the heat-shock protein HSP27 in fibrogenesis and EMT. In vitro, we have up- and down-modulated HSP27 expression in mesothelial and epithelial cell lines and studied the expression of different EMT markers induced by TGF-β1. In vivo, we inhibited HSP27 with the antisense oligonucleotide OGX-427 (in phase II clinical trials as anticancer agent) in our rat subpleural/pulmonary fibrosis models. We demonstrate that HSP27 is strongly expressed during the fibrotic process in patients with IPF and in different in vivo models. We showed that HSP27 binds to and stabilizes Snail and consequently induces EMT. Conversely, HSP27 knockdown leads to Snail proteasomal degradation, thus inhibiting TGF-β1-induced EMT. Inhibition of HSP27 with OGX-427 efficiently blocks EMT and fibrosis development. Controls in vivo were an empty adenovirus that did not induce fibrosis and a control antisense oligonucleotide. The present work opens the possibility of a new therapeutic use for HSP27 inhibitors against IPF, for which there is no conclusively effective treatment.

The heat-shock protein 27 (HSP27) is up-regulated in tumor cells and released in their microenvironment. Here, we show that extracellular HSP27 has a proangiogenic effect evidenced on chick chorioallantoic membrane. To explore this effect, we test the recombinant human protein (rhHSP27) at physiopathological doses (0.1-10 μg/ml) onto human microvascular endothelial cells (HMECs) grown as monolayers or spheroids. When added onto HMECs, rhHSP27 dose-dependently accelerates cell migration (with a peak at 5 μg/ml) and favors spheroid sprouting within 12-24 h. rhHSP27 increases VEGF gene transcription and promotes secretion of VEGF-activating VEGF receptor type 2. Increased VEGF transcription is related to NF-κB activation in 30 min. All of these effects are initiated by rhHSP27 interaction with Toll-like receptor 3 (TLR3). Such an interaction can be detected by immunoprecipitation but does not seem to be direct, as we failed to detect an interaction between rhHSP27 and monomeric TLR3 by SPR analysis. rhHSP27 is rapidly internalized with a pool of TLR3 to the endosomal compartment (within 15-30 min), which is required for NF-κB activation in a cytosolic Ca(2+)-dependent manner. The HSP27/TLR3 interaction induces NF-κB activation, leading to VEGF-mediated cell migration and angiogenesis. Such a pathway provides alternative targets for antiangiogenic cancer therapy.

Extracellular heat shock protein HSP90␣ was reported to participate in tumor cell growth, invasion, and metastasis formation through poorly understood signaling pathways. Herein, we show that extracellular HSP90␣ favors cell migration of glioblastoma U87 cells. More specifically, externally applied HSP90␣ rapidly induced endocytosis of EGFR. This response was accompanied by a transient increase in cytosolic Ca 2؉ appearing after 1-3 min of treatment. In the presence of EGF, U87 cells showed HSP90␣-induced Ca 2؉ oscillations, which were reduced by the ATP/ADPase, apyrase, and inhibited by the purinergic P 2 inhibitor, suramin, suggesting that ATP release is requested. Disruption of lipid rafts with methyl ␤-cyclodextrin impaired the Ca 2؉ rise induced by extracellular HSP90␣ combined with EGF. Specific inhibition of TLR4 expression by blocking antibodies suppressed extracellular HSP90␣-induced Ca 2؉ signaling and the associated cell migration. HSPs are known to bind lipopolysaccharides (LPSs). Preincubating cells with Polymyxin B, a potent LPS inhibitor, partially abrogated the effects of HSP90␣ without affecting Ca 2؉ oscillations observed with EGF. Extracellular HSP90␣ induced EGFR phosphorylation at Tyr-1068, and this event was prevented by both the protein kinase C␦ inhibitor, rottlerin, and the c-Src inhibitor, PP2. Altogether, our results suggest that extracellular HSP90␣ transactivates EGFR/ErbB1 through TLR4 and a PKC␦/c-Src pathway, which induces ATP release and cytosolic Ca 2؉ increase and finally favors cell migration. This mechanism could account for the deleterious effects of HSPs on high grade glioma when released into the tumor cell microenvironment.Glioma ranges from slowly growing low grade tumors to rapidly growing high grade tumors, including anaplastic astrocytoma and glioblastoma (1, 2). High grade gliomas include anaplastic tumor cells, necrotic foci, and rich vascularity, due largely to the aberrant expression of angiogenic factors by tumor cells (3). Tumor cells are highly proliferative and invasive within the brain. Despite the development of various treatments, the life expectancy of patients remains poor (4).One of the molecules that could contribute to invasion is the stress or heat shock protein 90 (HSP90). In several tumor types, cell surface expression of HSP90 correlates with metastatic potential (5), and its inhibition with antibodies (6, 7) or with cell-impermeable inhibitors (8) reduces cell migration in vitro. Of the two HSP90 isoforms, only HSP90␣ has been described extracellularly, which argues against cell lysis as the source of extracellular HSP90 (8). The metalloprotease MMP-2 can be associated with extracellular HSP90␣ (8), which is favored by acetylation of the stress protein (9). Surface HSP90␣ also participates in extracellular matrix proteininduced c-Src/integrin association and reorganization of the actin cytoskeleton (10). The cell-impermeable inhibitor of HSP90, 17-dimethylaminoethylamino-17-demethoxygeldanamycin (DMAG)-N-oxide, displays anti-invasive and anti-meta...

IVA337 is a pan‐peroxisome proliferator‐activated receptor (PPAR) agonist with moderate and well‐balanced activity on the three PPAR isoforms (α, γ, δ). PPARs are regulators of lipid metabolism, inflammation, insulin resistance, and fibrogenesis. Different single or dual PPAR agonists have been investigated for their therapeutic potential in nonalcoholic steatohepatitis (NASH), a chronic liver condition in which steatosis coexists with necroinflammation, potentially leading to liver fibrosis and cirrhosis. Clinical results have demonstrated variable improvements of histologically assessed hepatic lesions depending on the profile of the tested drug, suggesting that concomitant activation of the three PPAR isoforms would translate into a more substantial therapeutic outcome in patients with NASH. We investigated the effects of IVA337 on several preclinical models reproducing the main metabolic and hepatic features associated with NASH. These models comprised a diet‐induced obesity model (high‐fat/high‐sucrose diet); a methionine‐ and choline‐deficient diet; the foz/foz model; the CCl4‐induced liver fibrosis model (prophylactic and therapeutic) and human primary hepatic stellate cells. IVA337 normalized insulin sensitivity while controlling body weight gain, adiposity index, and serum triglyceride increases; it decreased liver steatosis, inflammation, and ballooning. IVA337 demonstrated preventive and curative effects on fibrosis in the CCl4 model and inhibited proliferation and activation of human hepatic stellate cells, the key cells driving liver fibrogenesis in NASH. Moreover, IVA337 inhibited the expression of (pro)fibrotic and inflammasome genes while increasing the expression of β‐oxidation‐related and fatty acid desaturation‐related genes in both the methionine‐ and choline‐deficient diet and the foz/foz model. For all models, IVA337 displayed an antifibrotic efficacy superior to selective PPARα, PPARδ, or PPARγ agonists. Conclusion: The therapeutic potential of IVA337 for the treatment of patients with NASH is supported by our data. (Hepatology Communications 2017;1:524–537)