Involvement of Stat3 phosphorylation in mild heat shock-induced thermotolerance

Conserved mechanisms of self-renewal and pluripotency in mouse and human ESCs regulated by simulated microgravity using a 3D clinostat

Embryonic stem cells (ESCs) exhibit unique attributes of boundless self-renewal and pluripotency, making them invaluable for fundamental investigations and clinical endeavors. Previous examinations of microgravity effects on ESC self-renewal and differentiation have predominantly maintained a descriptive nature, constrained by limited experimental opportunities and techniques. In this investigation, we present compelling evidence derived from murine and human ESCs, demonstrating that simulated microgravity (SMG)-induced stress significantly impacts self-renewal and pluripotency through a previously unidentified conserved mechanism. Specifically, SMG induces the upregulation of heat shock protein genes, subsequently enhancing the expression of core pluripotency factors and activating the Wnt and/or LIF/STAT3 signaling pathways, thereby fostering ESC self-renewal. Notably, heightened Wnt pathway activity, facilitated by Tbx3 upregulation, prompts mesoendodermal differentiation in both murine and human ESCs under SMG conditions. Recognizing potential disparities between terrestrial SMG simulations and authentic microgravity, forthcoming space flight experiments are imperative to validate the impact of reduced gravity on ESC self-renewal and differentiation mechanisms.

Harnessing Hyperthermia: Molecular, Cellular, and Immunological Insights for Enhanced Anticancer Therapies

Hyperthermia, the raising of tumor temperature (≥39°C), holds great promise as an adjuvant treatment for cancer therapy. This review focuses on 2 key aspects of hyperthermia: its molecular and cellular effects and its impact on the immune system. Hyperthermia has profound effects on critical biological processes. Increased temperatures inhibit DNA repair enzymes, making cancer cells more sensitive to chemotherapy and radiation. Elevated temperatures also induce cell cycle arrest and trigger apoptotic pathways. Furthermore, hyperthermia modifies the expression of heat shock proteins, which play vital roles in cancer therapy, including enhancing immune responses. Hyperthermic treatments also have a significant impact on the body's immune response against tumors, potentially improving the efficacy of immune checkpoint inhibitors. Mild systemic hyperthermia (39°C-41°C) mimics fever, activating immune cells and raising metabolic rates. Intense heat above 50°C can release tumor antigens, enhancing immune reactions. Using photothermal nanoparticles for targeted heating and drug delivery can also modulate the immune response. Hyperthermia emerges as a cost-effective and well-tolerated adjuvant therapy when integrated with immunotherapy. This comprehensive review serves as a valuable resource for the selection of patient-specific treatments and the guidance of future experimental studies.

NFE2L2 and STAT3 Converge on Common Targets to Promote Survival of Primary Lymphoma Cells

NFE2L2 and STAT3 are key pro-survival molecules, and thus, their targeting may represent a promising anti-cancer strategy. In this study, we found that a positive feedback loop occurred between them and provided evidence that their concomitant inhibition efficiently impaired the survival of PEL cells, a rare, aggressive B cell lymphoma associated with the gammaherpesvirus KSHV and often also EBV. At the molecular level, we found that NFE2L2 and STAT3 converged in the regulation of several pro-survival molecules and in the activation of processes essential for the adaption of lymphoma cells to stress. Among those, STAT3 and NFE2L2 promoted the activation of pathways such as MAPK3/1 and MTOR that positively regulate protein synthesis, sustained the antioxidant response, expression of molecules such as MYC, BIRC5, CCND1, and HSP, and allowed DDR execution. The findings of this study suggest that the concomitant inhibition of NFE2L2 and STAT3 may be considered a therapeutic option for the treatment of this lymphoma that poorly responds to chemotherapies.

Lung cancer treatment potential and limits associated with the STAT family of transcription factors

Lung cancer is one of the mortal cancers and the leading cause of cancer-related mortality, with a cancer survival rate of fewer than 5% in developing nations. This low survival rate can be linked to things like late-stage detection, quick postoperative recurrences in patients receiving therapy, and chemoresistance developing against various lung cancer treatments. Signal transducer and activator of transcription (STAT) family of transcription factors are involved in lung cancer cell proliferation, metastasis, immunological control, and treatment resistance. By interacting with specific DNA sequences, STAT proteins trigger the production of particular genes, which in turn result in adaptive and incredibly specific biological responses. In the human genome, seven STAT proteins have been discovered (STAT1 to STAT6, including STAT5a and STAT5b). Many external signaling proteins can activate unphosphorylated STATs (uSTATs), which are found inactively in the cytoplasm. When STAT proteins are activated, they can increase the transcription of several target genes, which leads to unchecked cellular proliferation, anti-apoptotic reactions, and angiogenesis. The effects of STAT transcription factors on lung cancer are variable; some are either pro- or anti-tumorigenic, while others maintain dual, context-dependent activities. Here, we give a succinct summary of the various functions that each member of the STAT family plays in lung cancer and go into more detail about the advantages and disadvantages of pharmacologically targeting STAT proteins and their upstream activators in the context of lung cancer treatment.

HSF1 Can Prevent Inflammation following Heat Shock by Inhibiting the Excessive Activation of the ATF3 and JUN&FOS Genes

Heat Shock Factor 1 (HSF1), a transcription factor frequently overexpressed in cancer, is activated by proteotoxic agents and participates in the regulation of cellular stress response. To investigate how HSF1 level affects the response to proteotoxic stress, we integrated data from functional genomics analyses performed in MCF7 breast adenocarcinoma cells. Although the general transcriptional response to heat shock was impaired due to HSF1 deficiency (mainly chaperone expression was inhibited), a set of genes was identified, including ATF3 and certain FOS and JUN family members, whose stress-induced activation was stronger and persisted longer than in cells with normal HSF1 levels. These genes were direct HSF1 targets, suggesting a dual (activatory/suppressory) role for HSF1. Moreover, we found that heat shock-induced inflammatory response could be stronger in HSF1-deficient cells. Analyses of The Cancer Genome Atlas data indicated that higher ATF3, FOS, and FOSB expression levels correlated with low HSF1 levels in estrogen receptor-positive breast cancer, reflecting higher heat shock-induced expression of these genes in HSF1-deficient MCF7 cells observed in vitro. However, differences between the analyzed cancer types were noted in the regulation of HSF1-dependent genes, indicating the presence of cell-type-specific mechanisms. Nevertheless, our data indicate the existence of the heat shock-induced network of transcription factors (associated with the activation of TNFα signaling) which includes HSF1. Independent of its chaperone-mediated cytoprotective function, HSF1 may be involved in the regulation of this network but prevents its overactivation in some cells during stress.

Impact of heat stress on prolactin-mediated ovarian JAK-STAT signaling in postpubertal gilts

Heat stress (HS) compromises almost every aspect of animal agriculture including reproduction. In pigs, this infecundity is referred to as seasonal infertility (SI), a phenotype including ovarian dysfunction. In multiple species, HS-induced hyperprolactinemia has been described; hence, our study objectives were to characterize and compare HS effects on circulating prolactin (PRL) and ovarian Janus kinase/signal transducer and activator of transcription (JAK-STAT) signaling during the follicular (FOL) or luteal (LUT) phases of the estrous cycle in postpubertal gilts. Gilts were estrus synchronized using altrenogest and environmental treatments began immediately after altrenogest withdrawal. For the FOL study: postpubertal gilts were allocated to constant thermoneutral (TN; n = 6; 20 ± 1.2 °C) or cyclical HS (n = 6; 25 to 32 ± 1.2 °C) conditions for 5 d. In the LUT study: postpubertal gilts were assigned to either TN (n = 7; 20 ± 2.6 °C) or cyclical HS (n = 7; 32 to 35 ± 2.6 °C) conditions from 2 to 12 days postestrus (dpe). Blood was collected by jugular venipuncture for PRL quantification on day 5 in the FOL and on day 0 and day 12 in the LUT gilts. Ovaries and corpora lutea (CL) were obtained from euthanized FOL and LUT gilts on day 5 and day 12, respectively. Western blotting was performed to quantify prolactin receptor (PRLR) and JAK/STAT pathway protein abundance. In the FOL phase, no difference (P = 0.20) in circulating PRL between thermal groups was observed. There was no effect (P ≥ 0.34) of HS on PRLR, signal transducer and activator of transcription 3 (STAT3), signal transducer and activator of transcription 5α (STAT5α), and phosphorylated signal transducer and activator of transcription α/β tyrosine 694/699 (pSTAT5α/β^Tyr694/699) abundance and Janus kinase 2 (JAK2), phosphorylated janus kinase 2 tyrosine 1007/1008 (pJAK2^Tyr1007/1008), STAT1, phosphorylated signal transducer and activator of transcription 1 tyrosine 701 (pSTAT1^Tyr701), phosphorylated signal transducer and activator of transcription 1 serine 727 (pSTAT1^Ser727), and phosphorylated signal transducer and activator of transcription 3 tyrosine 705 (pSTAT3^Tyr705) were undetectable in FOL gilt ovaries. Ovarian pSTAT5α/β^Tyr694/699 abundance tended to moderately increase (4%; P = 0.07) in FOL gilts by HS. In the LUT phase, circulating PRL increased progressively from 2 to 12 dpe, but no thermal treatment-induced difference (P = 0.37) was noted. There was no effect (P ≥ 0.16) of HS on CL abundance of PRLR, pJAK2^Tyr1007/1008, JAK2, STAT1, pSTAT1^Tyr701, pSTAT1^Ser727, pSTAT3^Tyr705, STAT5α, or pSTAT5α/β^Tyr694/699. In LUT phase, CL STAT3 abundance was increased (11%; P < 0.03) by HS. There was no impact of HS (P ≥ 0.76) on levels of pJAK2^Tyr1007/1008 and pSTAT5α/β^Tyr694/699 in LUT gilts; however, the CL pSTAT3^Tyr705:STAT3 ratio tended to be decreased (P = 0.10) due to HS. These results indicate an HS-induced estrous cycle-stage-dependent effect on the ovarian JAK/STAT pathway, establishing a potential role for this signaling pathway as a potential contributor to SI.

HSP70 promotes tumor progression by stabilizing Skp2 expression in gastric cancer cells

Gastric cancer (GC) has one of the highest tumor incidences worldwide. Heat shock protein 70 (HSP70) is highly expressed and plays a critical role in the occurrence, progression, metastasis, poor prognosis, and drug resistance of GC. However, the underlying mechanisms of HSP70 are not clear. To explore the regulatory role of HSP70 in GC, we performed cell counting kit-8 (CCK-8) and EdU staining assays to assess cell proliferation; immunohistochemistry and western blot analyses to assess protein expression; coimmunoprecipitation (Co-IP) assays to assess interactions between two proteins; and immunofluorescence to assess protein expression and localization. HSP70 was highly expressed in clinical samples from patients with GC and indicated a poor prognosis. HSP70 inhibition enhanced the sensitivity of GC cells to thermochemotherapy. Furthermore, we found that S phase kinase-associated protein 2 (Skp2) was highly expressed in GC and correlated with HSP70 in array data from The Cancer Genome Atlas (TCGA). Importantly, HSP70 inhibition promoted Skp2 degradation. Skp2 overexpression abrogated HSP70 inhibition-induced cell cycle arrest, suggesting that the role of HSP70 in GC depends on Skp2 expression. Our results illustrate a possible regulatory mechanism of HSP70 and may provide a therapeutic strategy for overcoming resistance to thermochemotherapy.

Ginger facilitates cell migration and heat tolerance in mouse fibroblast cells

The components of ginger root (Zingiber officinale Roscoe) are widely used for various medicinal purposes. Several bioactive compounds have been identified in ginger, including 6‑, 8‑ and 10‑gingerols, and 6‑shogaol, which are agonists of the thermo‑sensors transient receptor potential (TRP) cation channel subfamily V member 1 and TRP ankyrin 1. Our previous study demonstrated that ginger powder may affect human metabolism in vivo. However, the effects of the bioactive compounds of ginger on cells have not been completely elucidated. The present study investigated whether ginger powder extracts could modify cell functions in mouse fibroblast cells. The active components of ginger powder extracts were characterized using high‑performance liquid chromatography. The activation of protein kinases, actin assembly, cell migration, expression levels of heat shock proteins (HSPs) and cell viability after heat shock were analyzed in NIH3T3 mouse fibroblast cells. Subsequently, 6‑, 8‑, 10‑ and 12‑gingerols, as well as 6‑, 8‑ and 10‑shogaols, were detected in ginger powder extracts. The levels of phosphorylated Akt, mTOR, ERK and p38 MAPK increased after a 10‑min stimulation with ginger powder extracts. In addition, HSP expression levels, lamellipodia formation occurring at cell edges, cell migration and tolerance against heat shock were facilitated following ginger powder extract stimulation. These results suggest that ginger modified cell functions, including actin assembly and heat tolerance, in vitro.

Heat Shock Protein 27 Injection Leads to Caspase Activation in the Visual Pathway and Retinal T-Cell Response

Heat shock protein 27 (HSP27) is one of the small molecular chaperones and is involved in many cell mechanisms. Besides the known protective and helpful functions of intracellular HSP27, very little is known about the mode of action of extracellular HSP27. In a previous study, we showed that intravitreal injection of HSP27 led to neuronal damage in the retina and optic nerve after 21 days. However, it was not clear which degenerative signaling pathways were induced by the injection. For this reason, the pathological mechanisms of intravitreal HSP27 injection after 14 days were investigated. Histological and RT-qPCR analyses revealed an increase in endogenous HSP27 in the retina and an activation of components of the intrinsic and extrinsic apoptosis pathway. In addition, an increase in nucleus factor-kappa-light-chain-enhancer of activated B cells (NFκB), as well as of microglia/macrophages and T-cells could be observed. In the optic nerve, however, only an increased apoptosis rate was detectable. Therefore, the activation of caspases and the induction of an incipient immune response seem to be the main triggers for retinal degeneration in this intravitreal HSP27 model.

Heat Shock Alters Mesenchymal Stem Cell Identity and Induces Premature Senescence

Heat stress can have a serious impact on the health of both humans and animals. A major question is how heat stress affects normal development and differentiation at both the cellular and the organism levels. Here we use an in vitro experimental system to address how heat shock treatment influences the properties of bovine mesenchymal stem cells (MSCs)—multipotent progenitor cells—which are found in most tissues. Because cattle are sensitive to harsh external temperatures, studying the effects of heat shock on MSCs provides a unique platform to address cellular stress in a physiologically relevant model organism. Following isolation and characterization of MSCs from the cow’s umbilical cord, heat shock was induced either as a pulse (1 h) or continuously (3 days), and consequent effects on MSCs were characterized. Heat shock induced extensive phenotypic changes in MSCs and dramatically curtailed their capacity to proliferate and differentiate. These changes were associated with a partial arrest in the G1/S or G2/M checkpoints. Furthermore, MSCs lost their ability to resolve the inflammatory response of RAW macrophages in coculture. A possible explanation for this loss of function is the accumulation of reactive oxygen species and malfunction of the mitochondria in the treated cells. Heat shock treatments resulted in stress-induced premature senescence, affecting the MSCs’ ability to proliferate properly for many cell passages to follow. Exposure to elevated external temperatures leads to mitochondrial damage and oxidative stress, which in turn conveys critical changes in the proliferation, differentiation, and immunomodulatory phenotype of heat-stressed MSCs. A better understanding of the effect of heat shock on humans and animals may result in important health and economic benefits.

Heat Shock Proteins and PD-1/PD-L1 as Potential Therapeutic Targets in Myeloproliferative Neoplasms

Simple Summary

Myeloproliferative neoplasms (MPN), which are a heterogeneous group of rare disorders that affect blood cell production in bone marrow, present many significant challenges for clinicians. Though considerable progress has been made, in particular with the JAK1/2 inhibitor ruxolitinib, more effective alternative therapeutic approaches are needed. In the search for new and more efficient therapies, heat shock proteins, also known as stress proteins, and the programmed cell death 1 (PD-1)/programmed death ligand 1 (PD-L1) immune checkpoint axis have been found to be of great interest in hematologic malignancies. Here, we review the therapeutic potential of stress protein inhibitors in the management of patients diagnosed with MPN and summarize the accumulating evidence of the role of the PD-1/PD-L1 axis in MPN in order to provide perspectives on future therapeutic opportunities relative to the inhibition of these targets.

Abstract

Myeloproliferative neoplasms (MPN) are a group of clonal disorders that affect hematopoietic stem/progenitor cells. These disorders are often caused by oncogenic driver mutations associated with persistent Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling. While JAK inhibitors, such as ruxolitinib, reduce MPN-related symptoms in myelofibrosis, they do not influence the underlying cause of the disease and are not curative. Due to these limitations, there is a need for alternative therapeutic strategies and targets. Heat shock proteins (HSPs) are cytoprotective stress-response chaperones involved in protein homeostasis and in many critical pathways, including inflammation. Over the last decade, several research teams have unraveled the mechanistic connection between STAT signaling and several HSPs, showing that HSPs are potential therapeutic targets for MPN. These HSPs include HSP70, HSP90 (chaperoning JAK2) and both HSP110 and HSP27, which are key factors modulating STAT3 phosphorylation status. Like the HSPs, the PD-1/PD-L1 signaling pathway has been widely studied in cancer, but the importance of PD-L1-mediated immune escape in MPN was only recently reported. In this review, we summarize the role of HSPs and PD-1/PD-L1 signaling, the modalities of their experimental blockade, and the effect in MPN. Finally, we discuss the potential of these emerging targeted approaches in MPN therapy.

HIKESHI silencing can enhance mild hyperthermia sensitivity in human oral squamous cell carcinoma HSC‑3 cells

Hyperthermia (HT) is considered to be of value as a treatment modality in various cancers. However, the acquisition of thermotolerance in cancer cells due to the induction of heat shock proteins (HSPs) makes HT less effective. Recent findings have indicated that heat shock protein nuclear import factor hikeshi (HIKESHI), also referred to as C11orf73, acts as a nuclear import carrier of Hsp70 under heat stress conditions. The aim of the present study was to determine whether knockdown (KD) of HIKESHI by small interfering RNA (siRNA) can potentiate mild HT (MHT) sensitivity in human oral squamous cell carcinoma (OSCC) HSC‑3 cells. The mRNA and protein expression of HIKESHI was found to be markedly suppressed in HSC‑3 cells treated with siRNA for HIKESHI (siHIKE). Silencing HIKESHI significantly decreased the cell viability under MHT conditions (42˚C for 90 min). Immunocytochemical and western blot analyses clearly demonstrated that Hsp70 protein translocated from the cytoplasm to the nucleus under MHT conditions, and this translocation was significantly inhibited in cells treated with siHIKE. Treatment of the cells with MHT transiently increased the phosphorylation level of extracellular signal‑regulated kinase (ERK)2. Furthermore, the phosphorylation was sustained in HIKESHI‑KD cells under MHT conditions, and this sustained phosphorylation was abolished by pretreatment with U0126, an inhibitor of mitogen‑activated protein kinase/ERK. In addition, U0126 significantly decreased the viability of cells treated with the combination of HIKESHI‑KD and MHT. The data of the present study suggest that HIKESHI silencing enhanced the sensitivity of human OSCC HSC‑3 cells to MHT.

Chaperoning STAT3/5 by Heat Shock Proteins: Interest of Their Targeting in Cancer Therapy

While cells from multicellular organisms are dependent upon exogenous signals for their survival, growth, and proliferation, commitment to a specific cell fate requires the correct folding and maturation of proteins, as well as the degradation of misfolded or aggregated proteins within the cell. This general control of protein quality involves the expression and the activity of molecular chaperones such as heat shock proteins (HSPs). HSPs, through their interaction with the STAT3/STAT5 transcription factor pathway, can be crucial both for the tumorigenic properties of cancer cells (cell proliferation, survival) and for the microenvironmental immune cell compartment (differentiation, activation, cytokine secretion) that contributes to immunosuppression, which, in turn, potentially promotes tumor progression. Understanding the contribution of chaperones such as HSP27, HSP70, HSP90, and HSP110 to the STAT3/5 signaling pathway has raised the possibility of targeting such HSPs to specifically restrain STAT3/5 oncogenic functions. In this review, we present how HSPs control STAT3 and STAT5 activation, and vice versa, how the STAT signaling pathways modulate HSP expression. We also discuss whether targeting HSPs is a valid therapeutic option and which HSP would be the best candidate for such a strategy.