mTOR is essential for the proteotoxic stress response, HSF1 activation and heat shock protein synthesis

Bag-1-mediated HSF1 phosphorylation regulates expression of heat shock proteins in breast cancer cells

According to the World Health Organization in 2022, 2.3 million women were diagnosed with breast cancer. Investigating the interaction networks between Bcl-2-associated athanogene (Bag)-1 and other chaperone proteins may further the current understanding of the regulation of protein homeostasis in breast cancer cells and contribute to the development of treatment options. The present study aimed to determine the interactions between Bag-1 and heat shock proteins (HSPs); namely, HSP90, HSP70 and HSP27, to elucidate their role in promoting heat shock factor-1 (HSF1)-dependent survival of breast cancer cells. HER2-negative (MCF-7) and HER2-positive (BT-474) cell lines were used to examine the impact of Bag-1 expression on HSF1 and HSPs. We demonstrated that Bag-1 overexpression promoted HER2 expression in breast cancer cells, thereby resulting in the concurrent constitutive activation of the HSF1-HSP axis. The activation of HSP results in the stabilization of several tumor-promoting HSP clients such as AKT, mTOR and HSF1 itself, which substantially accelerates tumor development. Our results suggest that Bag-1 can modulate the chaperone activity of HSPs, such as HSP27, by directly or indirectly regulating the phosphorylation of HSF1. This modulation of chaperone activity can influence the activation of genes involved in cellular homeostasis, thereby protecting cells against stress.

Thermal adaptation in plants: understanding the dynamics of translation factors and condensates

Plants, as sessile organisms, face the crucial challenge of adjusting growth and development with ever-changing environmental conditions. Protein synthesis is the fundamental process that enables growth of all organisms. Since elevated temperature presents a substantial threat to protein stability and function, immediate adjustments of protein synthesis rates are necessary to circumvent accumulation of proteotoxic stress and to ensure survival. This review provides an overview of the mechanisms that control translation under high-temperature stress by the modification of components of the translation machinery in plants, and compares them to yeast and metazoa. Recent research also suggests an important role for cytoplasmic biomolecular condensates, named stress granules, in these processes. Current understanding of the role of stress granules in translational regulation and of the molecular processes associated with translation that might occur within stress granules is also discussed.

Interplay between mTOR and Purine Metabolism Enzymes and Its Relevant Role in Cancer

Tumor cells reprogram their metabolism to meet the increased demand for nucleotides and other molecules necessary for growth and proliferation. In fact, cancer cells are characterized by an increased "de novo" synthesis of purine nucleotides. Therefore, it is not surprising that specific enzymes of purine metabolism are the targets of drugs as antineoplastic agents, and a better knowledge of the mechanisms underlying their regulation would be of great help in finding new therapeutic approaches. The mammalian target of the rapamycin (mTOR) signaling pathway, which is often activated in cancer cells, promotes anabolic processes and is a major regulator of cell growth and division. Among the numerous effects exerted by mTOR, noteworthy is its empowerment of the "de novo" synthesis of nucleotides, accomplished by supporting the formation of purinosomes, and by increasing the availability of necessary precursors, such as one-carbon formyl group, bicarbonate and 5-phosphoribosyl-1-pyrophosphate. In this review, we highlight the connection between purine and mitochondrial metabolism, and the bidirectional relation between mTOR signaling and purine synthesis pathways.

ER Stress-Activated HSF1 Governs Cancer Cell Resistance to USP7 Inhibitor-Based Chemotherapy through the PERK Pathway

Ubiquitin-specific protease 7 inhibitors (USP7i) are considered a novel class of anticancer drugs. Cancer cells occasionally become insensitive to anticancer drugs, known as chemoresistance, by acquiring multidrug resistance, resulting in poor clinical outcomes in patients with cancer. However, the chemoresistance of cancer cells to USP7i (P22077 and P5091) and mechanisms to overcome it have not yet been investigated. In the present study, we generated human cancer cells with acquired resistance to USP7i-induced cell death. Gene expression profiling showed that heat stress response (HSR)- and unfolded protein response (UPR)-related genes were largely upregulated in USP7i-resistant cancer cells. Biochemical studies showed that USP7i induced the phosphorylation and activation of heat shock transcription factor 1 (HSF1), mediated by the endoplasmic reticulum (ER) stress protein kinase R-like ER kinase (PERK) signaling pathway. Inhibition of HSF1 and PERK significantly sensitized cancer cells to USP7i-induced cytotoxicity. Our study demonstrated that the ER stress-PERK axis is responsible for chemoresistance to USP7i, and inhibiting PERK is a potential strategy for improving the anticancer efficacy of USP7i.

Transcriptional modulation of heat shock proteins and adipogenic regulators in bovine adipocytes following heat exposure

This research endeavored to elucidate the transcriptional modulation of heat shock proteins and adipogenic regulators in bovine subcutaneous adipocytes following thermal exposure. Post-differentiation, mature adipocytes were subjected to three treatments of control (CON), moderate (MHS), and extreme (EHS) heat stress. These treatments consist of thermal conditions at temperatures of 38 °C (CON), 39.5 °C (MHS), or 41 °C (EHS) along with of 3 or 12 h. There was no statistically significant variations observed in the gene expressions of HSP27 and HSP70 when comparing CON with MHS across both exposures. Contrastingly, when comparing CON with EHS, an upregulation (P < 0.01) in HSP27 gene expression was evident for both 3 and 12 h of incubation, while HSP70 gene expression exhibited elevation (P < 0.01) at the 3-h mark, with no change observed at 12 h. Protein quantification, however, revealed an elevation (P < 0.01) in HSP27 and HSP70 for both CON vs. MHS and CON vs. EHS at the 12-h exposure. This trend in protein level mirrored (P < 0.05) that of proliferator-activated receptor-gamma (PPARγ). Elevated (P < 0.05) protein levels of fatty acid synthase (FAS) were exclusively discernible in the CON vs. MHS. Increased (P < 0.01) transcriptional activity of PPARγ, CCAAT/enhancer-binding protein alpha (C/EBPα), stearoyl-CoA desaturase (SCD), and FAS was evident in the CON vs. EHS comparison. Complementary to these molecular findings, an augmented lipid droplet accumulation was observed (P < 0.01) in EHS-exposed adipocytes progressively from day 6 through day 9. Our current study highlights how different levels and lengths of heat stress can impact the activity of important heat-related proteins and factors that play a role in fat development in beef cattle. These findings can help guide strategies to manage how beef cattle are exposed to heat, which can affect fat storage and ultimately the quality of the meat's marbling.

Heat Shock Factor 1 Inhibition: A Novel Anti-Cancer Strategy with Promise for Precision Oncology

Heat shock factor 1 (HSF1) is a transcription factor crucial for regulating heat shock response (HSR), one of the significant cellular protective mechanisms. When cells are exposed to proteotoxic stress, HSF1 induces the expression of heat shock proteins (HSPs) to act as chaperones, correcting the protein-folding process and maintaining proteostasis. In addition to its role in HSR, HSF1 is overexpressed in multiple cancer cells, where its activation promotes malignancy and leads to poor prognosis. The mechanisms of HSF1-induced tumorigenesis are complex and involve diverse signaling pathways, dependent on cancer type. With its important roles in tumorigenesis and tumor progression, targeting HSF1 offers a novel cancer treatment strategy. In this article, we examine the basic function of HSF1 and its regulatory mechanisms, focus on the mechanisms involved in HSF1's roles in different cancer types, and examine current HSF1 inhibitors as novel therapeutics to treat cancers.

Mechanically sensitive HSF1 is a key regulator of left-right symmetry breaking in zebrafish embryos

The left-right symmetry breaking of vertebrate embryos requires nodal flow. However, the molecular mechanisms that mediate the asymmetric gene expression regulation under nodal flow remain elusive. Here, we report that heat shock factor 1 (HSF1) is asymmetrically activated in the Kupffer's vesicle of zebrafish embryos in the presence of nodal flow. Deficiency in HSF1 expression caused a significant situs inversus and disrupted gene expression asymmetry of nodal signaling proteins in zebrafish embryos. Further studies demonstrated that HSF1 is a mechanosensitive protein. The mechanical sensation ability of HSF1 is conserved in a variety of mechanical stimuli in different cell types. Moreover, cilia and Ca2+-Akt signaling axis are essential for the activation of HSF1 under mechanical stress in vitro and in vivo. Considering the conserved expression of HSF1 in organisms, these findings unveil a fundamental mechanism of gene expression regulation by mechanical clues during embryonic development and other physiological and pathological transformations.

Characterisation of mesenchymal stem cells conditioned media obtained at different conditioning times: their effect on glial cells in in vitro scratch model

In this study, the bone marrow mesenchymal stem cells conditioned media (BMMSC-CM) obtained by conditioning for 24(CM24), 48(CM48) and 72(CM72) hours was characterised. In vitro, the impact of BMMSC-CM on the astrocyte migratory response and oligodendrocyte density was evaluated using the scratch model. The proteomic profiles of individual secretomes were analysed by mass spectrometry and the concentrations of four selected neurotrophins (BDNF, NGF, GDNF and VEGF) were determined by ELISA. Our results revealed an increased number of proteins at CM72, many of which are involved in neuroregenerative processes. ELISA documented a gradual increase in the concentration of two neurotrophins (NGF, VEGF), peaking at CM72. In vitro, the different effect of individual BMMSC-CM on astrocyte migration response and oligodendrocyte density was observed, most pronounced with CM72. The outcomes demonstrate that the prolonged conditioning results in increased release of detectable proteins, neurotrophic factors concentration and stronger effect on reparative processes in neural cell cultures.

Repression motif in HSF1 regulated by phosphorylation

The heat shock factor 1 (HSF1) is a transcription factor that itself is a sensor for stress and integrates various intrinsic or environmental stress sensing pathways. Thus HSF1 orchestrates the heat shock response (HSR) by translating these pathways into a distinct transcriptional program that aids the cells to cope with and adapt to proteotoxic stress. Although heavily researched the regulation of HSF1 activation is still not completely understood. A conserved reaction to stress is the hyperphosphorylation of the otherwise confined constitutive phosphorylated HSF1. Therefore, this stress specific phosphorylation is believed to be involved in the regulatory mechanism and hence, was and is focus of many studies, ascribing various effects to single phosphorylation sites. To gain additional insight into effects of phosphorylation, HSF1 carrying amino acid substitutions on up to 18 amino acids were tested for their transactivation potential on an HSR reporter plasmid. A pattern of eleven phosphor-mimicking and diminishing amino acid substitutions on well-known phosphorylation sites of HSF1 were introduced to produce transcriptional active [11 M(+)] or repressed [11 M(-)] phenotypes. It could be confirmed that heat activates HSF1 regardless of phosphorylation. Distinct cellular stress, obtained by chemical HSR inducers or mimicked by a constitutively active HSF1, showed clear differences in the activation potential of HSF1-11 M(+) and 11 M(-). Further refinement to the single amino acid level identified the S303/307 double-phosphorylation motif, wherein phosphorylation of S303 was sole responsible for the repressing effect. The effect could be reproduced in different cell lines and is not entirely based on degradation. A small repression motif could be dissociated from the HSF1 context, which is still capable of repressing the background transcription of a specifically designed reporter plasmid. Taken together these results indicate, that besides already described mechanisms of pS303/307 mediated repression of HSF1 activation, an additional mechanism repressing the transcriptional output of the entire HSE containing promoter is mediated by this small repressive motif.

Stress-Inducible SCAND Factors Suppress the Stress Response and Are Biomarkers for Enhanced Prognosis in Cancers

The cell stress response is an essential system present in every cell for responding and adapting to environmental stimulations. A major program for stress response is the heat shock factor (HSF)–heat shock protein (HSP) system that maintains proteostasis in cells and promotes cancer progression. However, less is known about how the cell stress response is regulated by alternative transcription factors. Here, we show that the SCAN domain (SCAND)-containing transcription factors (SCAN-TFs) are involved in repressing the stress response in cancer. SCAND1 and SCAND2 are SCAND-only proteins that can hetero-oligomerize with SCAN-zinc finger transcription factors, such as MZF1(ZSCAN6), for accessing DNA and transcriptionally co-repressing target genes. We found that heat stress induced the expression of SCAND1, SCAND2, and MZF1 bound to HSP90 gene promoter regions in prostate cancer cells. Moreover, heat stress switched the transcript variants’ expression from long noncoding RNA (lncRNA-SCAND2P) to protein-coding mRNA of SCAND2, potentially by regulating alternative splicing. High expression of HSP90AA1 correlated with poorer prognoses in several cancer types, although SCAND1 and MZF1 blocked the heat shock responsiveness of HSP90AA1 in prostate cancer cells. Consistent with this, gene expression of SCAND2, SCAND1, and MZF1 was negatively correlated with HSP90 gene expression in prostate adenocarcinoma. By searching databases of patient-derived tumor samples, we found that MZF1 and SCAND2 RNA were more highly expressed in normal tissues than in tumor tissues in several cancer types. Of note, high RNA expression of SCAND2, SCAND1, and MZF1 correlated with enhanced prognoses of pancreatic cancer and head and neck cancers. Additionally, high expression of SCAND2 RNA was correlated with better prognoses of lung adenocarcinoma and sarcoma. These data suggest that the stress-inducible SCAN-TFs can function as a feedback system, suppressing excessive stress response and inhibiting cancers.

N-butyrate increases heat shock protein 70 through heat shock factor 1 and AMP-activated protein kinase pathways in human intestinal Caco-2 cells

Impaired integrity of the intestinal epithelium is a cause of intestinal and extraintestinal diseases. Heat shock protein 70 (HSP70), a cytoprotective protein, plays an important role in maintaining intestinal homeostasis. The intestinal expression of HSP70 is linked with the local microbiota. The present study investigated the molecular mechanisms underlying the upregulation of HSP70 by n-butyrate, a major metabolite of the intestinal microbiota in human intestinal Caco-2 cells. Treatment of Caco-2 cells with n-butyrate upregulated HSP70 protein and mRNA levels in a dose-dependent manner. Using luciferase reporter assay, it was found that n-butyrate enhanced the transcriptional activity of HSP70. These effects were sensitive to the inhibition of heat shock factor 1 (HSF1), a transcription factor, and AMP-activated protein kinase (AMPK). N-butyrate increased the phosphorylation (activity) of HSF1 and AMPK. Taken together, this study shows that n-butyrate is partly involved in the microbiota-dependent intestinal expression of HSP70, and the effect is exerted through the HSF1 and AMPK pathways.

Maternal nutritional status modifies heat-associated growth restriction in women with chronic malnutrition

Rapid changes in the global climate are deepening existing health disparities from resource scarcity and malnutrition. Rising ambient temperatures represent an imminent risk to pregnant women and infants. Both maternal malnutrition and heat stress during pregnancy contribute to poor fetal growth, the leading cause of diminished child development in low-resource settings. However, studies explicitly examining interactions between these two important environmental factors are lacking. We leveraged maternal and neonatal anthropometry data from a randomized controlled trial focused on improving preconception maternal nutrition (Women First Preconception Nutrition trial) conducted in Thatta, Pakistan, where both nutritional deficits and heat stress are prevalent. Multiple linear regression of ambient temperature and neonatal anthropometry at birth (n = 459) showed a negative association between daily maximal temperatures in the first trimester and Z-scores of birth length and head circumference. Placental mRNA-sequencing and protein analysis showed transcriptomic changes in protein translation, ribosomal proteins, and mTORC1 signaling components in term placenta exposed to excessive heat in the first trimester. Targeted metabolomic analysis indicated ambient temperature associated alterations in maternal circulation with decreases in choline concentrations. Notably, negative impacts of heat on birth length were in part mitigated in women randomized to comprehensive maternal nutritional supplementation before pregnancy suggesting potential interactions between heat stress and nutritional status of the mother. Collectively, the findings bridge critical gaps in our current understanding of how maternal nutrition may provide resilience against adverse effects of heat stress in pregnancy.

Targeting HSF1 for cancer treatment: mechanisms and inhibitor development

Heat Shock Factor 1 (HSF1) is a master regulator of heat shock responsive signaling. In addition to playing critical roles in cellular heat shock response, emerging evidence suggests that HSF1 also regulates a non-heat shock responsive transcriptional network to handle metabolic, chemical, and genetic stress. The function of HSF1 in cellular transformation and cancer development has been extensively studied in recent years. Due to important roles for HSF1 for coping with various stressful cellular states, research on HSF1 has been very active. New functions and molecular mechanisms underlying these functions have been continuously discovered, providing new targets for novel cancer treatment strategies. In this article, we review the essential roles and mechanisms of HSF1 action in cancer cells, focusing more on recently discovered functions and their underlying mechanisms to reflect the new advances in cancer biology. In addition, we emphasize new advances with regard to HSF1 inhibitors for cancer drug development.

HSF1 phosphorylation establishes an active chromatin state via the TRRAP-TIP60 complex and promotes tumorigenesis

Transcriptional regulation by RNA polymerase II is associated with changes in chromatin structure. Activated and promoter-bound heat shock transcription factor 1 (HSF1) recruits transcriptional co-activators, including histone-modifying enzymes; however, the mechanisms underlying chromatin opening remain unclear. Here, we demonstrate that HSF1 recruits the TRRAP-TIP60 acetyltransferase complex in HSP72 promoter during heat shock in a manner dependent on phosphorylation of HSF1-S419. TRIM33, a bromodomain-containing ubiquitin ligase, is then recruited to the promoter by interactions with HSF1 and a TIP60-mediated acetylation mark, and cooperates with the related factor TRIM24 for mono-ubiquitination of histone H2B on K120. These changes in histone modifications are triggered by phosphorylation of HSF1-S419 via PLK1, and stabilize the HSF1-transcription complex in HSP72 promoter. Furthermore, HSF1-S419 phosphorylation is constitutively enhanced in and promotes proliferation of melanoma cells. Our results provide mechanisms for HSF1 phosphorylation-dependent establishment of an active chromatin status, which is important for tumorigenesis.

Here the authors show phosphorylation of heat shock factor 1 (HSF1) at S419 via the chromatin-bound kinase PLK1, promotes HSF1 recruitment of histone acetyltransferases and histone acetylation reader proteins TRIM33 and TRIM24, which actually also execute histone H2BK120 mono-ubiquitination at target genes. Furthermore, HSF1 phosphorylation has an impact on melanoma cell proliferation.

HSF-1: Guardian of the Proteome Through Integration of Longevity Signals to the Proteostatic Network

Discoveries made in the nematode Caenorhabditis elegans revealed that aging is under genetic control. Since these transformative initial studies, C. elegans has become a premier model system for aging research. Critically, the genes, pathways, and processes that have fundamental roles in organismal aging are deeply conserved throughout evolution. This conservation has led to a wealth of knowledge regarding both the processes that influence aging and the identification of molecular and cellular hallmarks that play a causative role in the physiological decline of organisms. One key feature of age-associated decline is the failure of mechanisms that maintain proper function of the proteome (proteostasis). Here we highlight components of the proteostatic network that act to maintain the proteome and how this network integrates into major longevity signaling pathways. We focus in depth on the heat shock transcription factor 1 (HSF1), the central regulator of gene expression for proteins that maintain the cytosolic and nuclear proteomes, and a key effector of longevity signals.

Determination of the optimal maturation temperature for adult honey bee toxicity testing

Honey bees are exposed to various pesticides through pollinating and in-hive Varroa mite control. The most basic method for evaluating pesticide toxicity is the indoor bioassay using worker bees, in which newly emerged adults are matured in incubators for conditioning before use. However, little information is available on the optimum maturation temperature from a toxicological point of view, even though it can affect honey bee responses to pesticides. In this paper, to evaluate the optimal maturation temperature for pesticide toxicity testing, several indices related to the development, gene transcription, and toxicological properties of honey bee adults following maturation at 25, 30, and 35 °C were compared with those of field bees. The body weight and developmental state of hypopharyngeal glands were highest in the bees matured at 30 °C, and the overall transcription profiles of detoxification-related genes in the field bees were closest to those of bees matured at 30 °C, whereas immaturity and features of thermal stress were observed in the 25 °C and 35 °C bee groups, respectively. In the bioassay results, the effects of maturation temperature on the toxic response of honey bees varied significantly depending on the type of pesticide. By considering all the biological and toxicological aspects examined, we confirmed that 30 °C is a recommended maturation temperature for adult honey bee toxicity test.

ATF6 prevents DNA damage and cell death in colon cancer cells undergoing ER stress

Colon cancer represents one of the most common and aggressive cancers in its advanced state. Among the most innovative anti-cancer approaches, the manipulation of UPR is a promising one, effective also against cancers carrying dysfunctional p53. Interestingly, it is emerging that UPR cross-talks with DDR and that targeting the interplay between these two adaptive responses may be exploited to overcome the resistance to the single DDR- and UPR-targeting treatments. Previous studies have highlighted the role of IRE1 alpha and PERK UPR sensors on DDR, while the impact of ATF6 on this process remains under-investigated. This study shows for the first time that ATF6 sustains the expression level of BRCA-1 and protects colon cancer cells from the cytotoxic effect of ER stressors DPE and Thapsigargin. At molecular level, ATF6 activates mTOR to sustain the expression of HSP90, of which BRCA-1 is a client protein. Therefore, pharmacological or genetic inhibition of ATF6 promoted BRCA-1 degradation and increased DNA damage and cell death, particularly in combination with Adriamycin. All together this study suggests that targeting ATF6 may not only potentiate the cytotoxic effect of drugs triggering ER stress but may render colon cancer cells more sensitive to Adriamycin and possibly to other DNA damaging agents used to treat colon cancer.

Interconnected Adaptive Responses: A Way Out for Cancer Cells to Avoid Cellular Demise

Different from normal cells, cancer cells must hyperactivate a variety of integrated responses in order to survive their basal stress or its exacerbation caused by exposure to anti-cancer agents. As cancer cells become particularly dependent on these adaptive responses, namely UPR, DDR autophagy, anti-oxidant and heat shock responses, this turns out to be an Achille’s heel, which allows them to be selectively killed while sparing normal unstressed cells. Better knowledge of the cross-talk between these adaptive processes and their impact on the immune system is needed to design more effective anti-cancer therapies, as reviewed in this paper.

mTOR substrate phosphorylation in growth control

The target of rapamycin (TOR), discovered 30 years ago, is a highly conserved serine/threonine protein kinase that plays a central role in regulating cell growth and metabolism. It is activated by nutrients, growth factors, and cellular energy. TOR forms two structurally and functionally distinct complexes, TORC1 and TORC2. TOR signaling activates cell growth, defined as an increase in biomass, by stimulating anabolic metabolism while inhibiting catabolic processes. With emphasis on mammalian TOR (mTOR), we comprehensively reviewed the literature and identified all reported direct substrates. In the context of recent structural information, we discuss how mTORC1 and mTORC2, despite having a common catalytic subunit, phosphorylate distinct substrates. We conclude that the two complexes recruit different substrates to phosphorylate a common, minimal motif.

Curcumin and Ethanol Effects in Trembler-J Schwann Cell Culture

Charcot-Marie-Tooth (CMT) syndrome is the most common progressive human motor and sensory peripheral neuropathy. CMT type 1E is a demyelinating neuropathy affecting Schwann cells due to peripheral-myelin-protein-22 (PMP22) mutations, modelized by Trembler-J mice. Curcumin, a natural polyphenol compound obtained from turmeric (Curcuma longa), exhibits dose- and time-varying antitumor, antioxidant and neuroprotective properties, however, the neurotherapeutic actions of curcumin remain elusive. Here, we propose curcumin as a possible natural treatment capable of enhancing cellular detoxification mechanisms, resulting in an improvement of the neurodegenerative Trembler-J phenotype. Using a refined method for obtaining enriched Schwann cell cultures, we evaluated the neurotherapeutic action of low dose curcumin treatment on the PMP22 expression, and on the chaperones and autophagy/mammalian target of rapamycin (mTOR) pathways in Trembler-J and wild-type genotypes. In wild-type Schwann cells, the action of curcumin resulted in strong stimulation of the chaperone and macroautophagy pathway, whereas the modulation of ribophagy showed a mild effect. However, despite the promising neuroprotective effects for the treatment of neurological diseases, we demonstrate that the action of curcumin in Trembler-J Schwann cells could be impaired due to the irreversible impact of ethanol used as a common curcumin vehicle necessary for administration. These results contribute to expanding our still limited understanding of PMP22 biology in neurobiology and expose the intrinsic lability of the neurodegenerative Trembler-J genotype. Furthermore, they unravel interesting physiological mechanisms of cellular resilience relevant to the pharmacological treatment of the neurodegenerative Tremble J phenotype with curcumin and ethanol. We conclude that the analysis of the effects of the vehicle itself is an essential and inescapable step to comprehensibly assess the effects and full potential of curcumin treatment for therapeutic purposes.

High PPT1 expression predicts poor clinical outcome and PPT1 inhibitor DC661 enhances sorafenib sensitivity in hepatocellular carcinoma

Background

Adaptive resistance and side effects of sorafenib treatment result in unsatisfied survival of patients with hepatocellular carcinoma (HCC). Palmitoyl-protein thioesterase 1 (PPT1) plays a critical role in progression of various cancers. However, its role on prognosis and immune infiltrates in HCC remains unclarified.

Methods

By data mining in the Cancer Genome Atlas databases, the role of PPT1 in HCC were initially investigated. Furthermore, HCC cell lines Hep 3B and Hep 1-6 were treated with DC661 or siRNA against PPT1. The biological function of PPT1 was determined by CCK-8 test, colony formation assay, TUNEL staining, immunofluorescence staining, Western blot test, and PI-Annexin V apoptosis assays in vitro. Animal models of subcutaneous injection were applied to investigate the therapeutic role of targeting PPT1.

Results

We found that PPT1 levels were significantly upregulated in HCC tissues compared with normal tissues and were significantly associated with a poor prognosis. Multivariate analysis further confirmed that high expression of PPT1 was an independent risk factor for poor overall survival of HCC patients. We initially found that PPT1 was significantly upregulated in sorafenib-resistant cell lines established in this study. Upon sorafenib treatment, HCC cells acquired adaptive resistance by inducing autophagy. We found that DC661, a selective and potent small-molecule PPT1-inhibitor, induced lysosomal membrane permeability, caused lysosomal deacidification, inhibited autophagy and enhanced sorafenib sensitivity in HCC cells. Interestingly, this sensitization effect was also mediated by the induction mitochondrial pathway apoptosis. In addition, the expression level of PPT1 was associated with the immune infiltration in the HCC tumor microenvironment, and PPT1 inhibitor DC661 significantly enhanced the anti-tumor immune response by promoting dendritic cell maturation and further promoting CD8+ T cell activation. Moreover, DC661 combined with sorafenib was also very effective at treating tumor models in immunized mice.

Conclusions

Our findings suggest that targeting PPT1 with DC661 in combination with sorafenib might be a novel and effective alternative therapeutic strategy for HCC.

Exercise mitigates the Toll of muscle atrophy: A narrative review of the effects of exercise on Toll-like receptor-4 in leukocytes and skeletal muscle

Conditions characterized by muscle wasting such as cachexia and sarcopenia are devastating at the individual level, and they place a profound burden on public health. Evidence suggests that inflammation is likely a mechanistic contributor to the pathogenesis of these conditions. One specific molecule, lipopolysaccharide, has gained attention due to its role in initiating inflammation. Toll-like receptor-4 is the primary receptor for lipopolysaccharide and has been shown to be implicit in the downstream proinflammatory response associated with lipopolysaccharide. Importantly, Toll-like receptor-4 is expressed on various cell types throughout the human body such as leukocytes and skeletal muscle fibers and may have site-specific effects that contribute to muscle wasting conditions based on the location in which activation occurs. Accordingly, reducing proinflammatory signaling at these locations may be an effective strategy at mitigating muscle wasting. Regular exercise training is believed to elicit anti-inflammatory adaptations, but the mechanisms by which this occurs are yet to be fully understood. Understanding the mechanisms by which Toll-like receptor-4 activation contributes to muscle wasting and how exercise affects this, may allow for the development of a non-pharmacological therapeutic intervention. Therefore, in this review, we summarize the current understanding of the lipopolysaccharide/Toll-like receptor-4 axis in leukocytes and skeletal muscle fibers on the pathogenesis of muscle wasting conditions and we critically examine the current evidence regarding the effects of exercise on this axis.

AKT1 mediates multiple phosphorylation events that functionally promote HSF1 activation

The heat stress response activates the transcription factor heat shock factor 1 (HSF1), which subsequently upregulates heat shock proteins to maintain the integrity of the proteome. HSF1 activation requires nuclear localization, trimerization, DNA binding, phosphorylation and gene transactivation. Phosphorylation at S326 is an important regulator of HSF1 transcriptional activity. Phosphorylation at S326 is mediated by AKT1, mTOR, p38, MEK1 and DYRK2. Here, we observed activation of HSF1 by AKT1 independently of mTOR. AKT2 also phosphorylated S326 of HSF1 but showed weak ability to activate HSF1. Similarly, mTOR, p38, MEK1 and DYRK2 all phosphorylated S326 but AKT1 was the most potent activator. Mass spectrometry showed that AKT1 also phosphorylated HSF1 at T142, S230 and T527 in addition to S326, whereas the other kinases did not. Subsequent investigation revealed that phosphorylation at T142 is necessary for HSF1 trimerization and that S230, S326 and T527 are required for HSF1 gene transactivation and recruitment of TFIIB and CDK9. Interestingly, T527 as a phosphorylated residue has not been previously shown and sits in the transactivation domain, further implying a role for this site in HSF1 gene transactivation. This study suggests that HSF1 hyperphosphorylation is targeted and these specific residues have direct function in regulating HSF1 transcriptional activity.

Engineering nanomedicines to inhibit hypoxia-inducible Factor-1 for cancer therapy

Hypoxia-inducible factor-1 (HIF-1), an essential promoter of tumor progression, has attracted increasing attention as a therapeutic target. In addition to hypoxic cellular conditions, HIF-1 activation can be triggered by cancer treatment, which causes drug tolerance and therapeutic failure. To date, a series of effective strategies have been explored to suppress HIF-1 function, including silencing the HIF-1α gene, inhibiting HIF-1α protein translation, degrading HIF-1α protein, and inhibiting HIF-1 transcription. Furthermore, nanoparticle-based drug delivery systems have been widely developed to improve the stability and pharmacokinetics of HIF-1 inhibitors or achieve HIF-1-targeted combination therapies as a nanoplatform. In this review, we summarize the current literature on nanomedicines targeting HIF-1 to combat cancer and discuss their potential for future development.

Role of the mTOR-autophagy-ER stress pathway in high fructose-induced metabolic-associated fatty liver disease

Metabolic-associated fatty liver disease (MAFLD) is the most common metabolic disease with a global prevalence of 25%. While MAFLD is serious and incurable at the later stage, it can be controlled or reversed at the early stage of hepatosteatosis originating from unhealthy diets. Recent laboratory evidence implicates a critical role of the mammalian target of rapamycin (mTOR)-autophagy signaling pathway in the pathogenesis of MAFLD induced by a high-fructose diet mimicking the overconsumption of sugar in humans. This review discusses the possible molecular mechanisms of mTOR-autophagy-endoplasmic reticulum (ER) stress in MAFLD. Based on careful analysis of recent studies, we suggest possible new therapeutic concepts or targets that can be explored for the discovery of new anti-MAFLD drugs.

Heat shock factor 1 suppression induces spindle abnormalities and sensitizes cells to antimitotic drugs

BACKGROUND

Heat shock factor 1 (HSF1) is the master regulator of the heat shock response and supports malignant cell transformation. Recent work has shown that HSF1 can access the promoters of heat shock proteins (HSPs) and allow HSP expression during mitosis. It also acts as a mitotic regulator, controlling chromosome segregation. In this study, we investigated whether the transactivation activity of HSF1 is required for the assembly of mitotic spindles.

RESULTS

Our results showed that phosphorylation of HSF1 at serine 326 (S326) and its transactivation activity were increased during mitosis. Inhibition of the transactivation activity of HSF1 by KRIBB11 or CCT251263 during mitosis significantly increased the proportion of mitotic cells with abnormal spindles. It also hampered the reassembly of spindle microtubules after nocodazole treatment and washout by impeding the formation of chromosomal microtubule asters. Depletion of HSF1 led to defects in mitotic spindle assembly, subsequently attenuating cell proliferation and anchorage-independent cell growth (AIG). These HSF1 depletion-induced effects could be rescued by ectopically expressing wild-type HSF1 or a constitutively active mutant (∆202-316, caHSF1) but not the S326A or dominant negative (∆361-529, dnHSF1) mutants. In addition, overexpression of HSP70 partially reduced HSF1 depletion-induced spindle abnormalities. These results indicate that HSF1 may support cell proliferation and AIG by maintaining spindle integrity through its transactivation activity. Furthermore, inhibition of HSF1 transactivation activity by KRIBB11 or CCT251236 can enhance diverse anti-mitosis drug-induced spindle defects and cell death.

CONCLUSIONS

The increased transactivation activity of HSF1 during mitosis appears to be required for accurate assembly of mitotic spindles, thereby supporting cell viability and probably AIG. In addition, inhibition of the transactivation activity of HSF1 may enhance the mitotic errors and cell death induced by anti-mitosis drugs.

The heat shock response and small molecule regulators

The heat shock response (HSR) is a highly conserved cellular pathway that is responsible for stress relief and the refolding of denatured proteins [1]. When a host cell is exposed to conditions such as heat shock, ischemia, or toxic substances, heat shock factor-1 (HSF-1), a transcription factor, activates the genes that encode for the heat shock proteins (Hsps), which are a family of proteins that work alongside other chaperones to relieve stress and refold proteins that have been denatured (Burdon, 1986) [2]. Along with the refolding of denatured proteins, Hsps facilitate the removal of misfolded proteins by escorting them to degradation pathways, thereby preventing the accumulation of misfolded proteins [3]. Research has indicated that many pathological conditions, such as diabetes, cancer, neuropathy, cardiovascular disease, and aging have a negative impact on HSR function and are commonly associated with misfolded protein aggregation [4,5]. Studies indicate an interplay between mitochondrial homeostasis and HSF-1 levels can impact stress resistance, proteostasis, and malignant cell growth, which further support the role of Hsps in pathological and metabolic functions [6]. On the other hand, Hsp activation by specific small molecules can induce the heat shock response, which can afford neuroprotection and other benefits [7]. This review will focus on the modulation of Hsps and the HSR as therapeutic options to treat these conditions.

The C-terminal HSP90 inhibitor NCT-58 kills trastuzumab-resistant breast cancer stem-like cells

N-terminal HSP90 inhibitors in development have had issues arising from heat shock response (HSR) induction and off-target effects. We sought to investigate the capacity of NCT-58, a rationally-synthesized C-terminal HSP90 inhibitor, to kill trastuzumab-resistant HER2-positive breast cancer stem-like cells. NCT-58 does not induce the HSR due to its targeting of the C-terminal region and elicits anti-tumor activity via the simultaneous downregulation of HER family members as well as inhibition of Akt phosphorylation. NCT-58 kills the rapidly proliferating bulk tumor cells as well as the breast cancer stem-like population, coinciding with significant reductions in stem/progenitor markers and pluripotent transcription factors. NCT-58 treatment suppressed growth and angiogenesis in a trastuzumab-resistant xenograft model, concomitant with downregulation of ICD-HER2 and HSF-1/HSP70/HSP90. These findings warrant further investigation of NCT-58 to address trastuzumab resistance in heterogeneous HER2-positive cancers.

mTORC1 Crosstalk With Stress Granules in Aging and Age-Related Diseases

The mechanistic target of rapamycin complex 1 (mTORC1) kinase is a master regulator of metabolism and aging. A complex signaling network converges on mTORC1 and integrates growth factor, nutrient and stress signals. Aging is a dynamic process characterized by declining cellular survival, renewal, and fertility. Stressors elicited by aging hallmarks such as mitochondrial malfunction, loss of proteostasis, genomic instability and telomere shortening impinge on mTORC1 thereby contributing to age-related processes. Stress granules (SGs) constitute a cytoplasmic non-membranous compartment formed by RNA-protein aggregates, which control RNA metabolism, signaling, and survival under stress. Increasing evidence reveals complex crosstalk between the mTORC1 network and SGs. In this review, we cover stressors elicited by aging hallmarks that impinge on mTORC1 and SGs. We discuss their interplay, and we highlight possible links in the context of aging and age-related diseases.

Inhibition of translation initiation factor eIF4a inactivates heat shock factor 1 (HSF1) and exerts anti-leukemia activity in AML

Eukaryotic initiation factor 4A (eIF4A), the enzymatic core of the eIF4F complex essential for translation initiation, plays a key role in the oncogenic reprogramming of protein synthesis, and thus is a putative therapeutic target in cancer. As important component of its anticancer activity, inhibition of translation initiation can alleviate oncogenic activation of HSF1, a stress-inducible transcription factor that enables cancer cell growth and survival. Here, we show that primary acute myeloid leukemia (AML) cells exhibit the highest transcript levels of eIF4A1 compared to other cancer types. eIF4A inhibition by the potent and specific compound rohinitib (RHT) inactivated HSF1 in these cells, and exerted pronounced in vitro and in vivo anti-leukemia effects against progenitor and leukemia-initiating cells, especially those with FLT3-internal tandem duplication (ITD). In addition to its own anti-leukemic activity, genetic knockdown of HSF1 also sensitized FLT3-mutant AML cells to clinical FLT3 inhibitors, and this synergy was conserved in FLT3 double-mutant cells carrying both ITD and tyrosine kinase domain mutations. Consistently, the combination of RHT and FLT3 inhibitors was highly synergistic in primary FLT3-mutated AML cells. Our results provide a novel therapeutic rationale for co-targeting eIF4A and FLT3 to address the clinical challenge of treating FLT3-mutant AML.

Propionate and Dietary Fermentable Fibers Upregulate Intestinal Heat Shock protein70 in Intestinal Caco-2 Cells and Mouse Colon

Short-chain fatty acids (SCFAs), including propionate, are major metabolites of intestinal microorganisms and play an essential role in regulating intestinal epithelial integrity. Heat shock proteins (HSPs) promote cellular homeostasis under physiological and stressed conditions. This study aimed to investigate the regulation of intestinal HSP70 by propionate in human intestinal Caco-2 cells and the colon of fermentable dietary fiber (DF)-fed mice and germ-free mice. The results showed that propionate increased Hspa1a (HSP70 mRNA) level in Caco-2 cells, upregulated HSP70 protein, and phosphorylation of heat shock factor 1; however, the latter two were reduced by mitogen-activated protein kinases and the mechanistic target of rapamycin inhibitors. Feeding fermentable DFs, such as guar gum (GG) and partially hydrolyzed GG, increased both cecal SCFAs and colonic HSP70 expression, both of which were reduced in germ-free mice than in specific-pathogen-free mice. Collectively, the propionate-induced HSP70 expression was shown to be possibly involved in intestinal homeostasis.

Multifaceted roles of HSF1 in cell death: A state-of-the-art review

Cell death is a common and active process that is involved in various biological processes, including organ development, morphogenesis, maintaining tissue homeostasis and eliminating potentially harmful cells. Abnormal regulation of cell death significantly contributes to tumor development, progression and chemoresistance. The mechanisms of cell death are complex and involve not only apoptosis and necrosis but also their cross-talk with other types of cell death, such as autophagy and the newly identified ferroptosis. Cancer cells are chronically exposed to various stresses, such as lack of oxygen and nutrients, immune responses, dysregulated metabolism and genomic instability, all of which lead to activation of heat shock factor 1 (HSF1). In response to heat shock, oxidative stress and proteotoxic stresses, HSF1 upregulates transcription of heat shock proteins (HSPs), which act as molecular chaperones to protect normal cells from stresses and various diseases. Accumulating evidence suggests that HSF1 regulates multiple types of cell death through different signaling pathways as well as expression of distinct target genes in cancer cells. Here, we review the current understanding of the potential roles and molecular mechanism of HSF1 in regulating apoptosis, autophagy and ferroptosis. Deciphering HSF1-regulated signaling pathways and target genes may help in the development of new targeted anti-cancer therapeutic strategies.

Hsf1 activation by proteotoxic stress requires concurrent protein synthesis

Heat shock factor 1 (Hsf1) activation is responsible for increasing the abundance of protein-folding chaperones and degradation machinery in response to proteotoxic conditions that give rise to misfolded or aggregated proteins. Here we systematically explored the link between concurrent protein synthesis and proteotoxic stress in the budding yeast, Saccharomyces cerevisiae. Consistent with prior work, inhibiting protein synthesis before inducing proteotoxic stress prevents Hsf1 activation, which we demonstrated across a broad array of stresses and validate using orthogonal means of blocking protein synthesis. However, other stress-dependent transcription pathways remained activatable under conditions of translation inhibition. Titrating the protein denaturant ethanol to a higher concentration results in Hsf1 activation in the absence of translation, suggesting extreme protein-folding stress can induce proteotoxicity independent of protein synthesis. Furthermore, we demonstrate this connection under physiological conditions where protein synthesis occurs naturally at reduced rates. We find that disrupting the assembly or subcellular localization of newly synthesized proteins is sufficient to activate Hsf1. Thus, new proteins appear to be especially sensitive to proteotoxic conditions, and we propose that their aggregation may represent the bulk of the signal that activates Hsf1 in the wake of these insults.

MED12 interacts with the heat-shock transcription factor HSF1 and recruits CDK8 to promote the heat-shock response in mammalian cells

Activated and promoter-bound heat-shock transcription factor 1 (HSF1) induces RNA polymerase II recruitment upon heat shock, and this is facilitated by the core Mediator in Drosophila and yeast. Another Mediator module, CDK8 kinase module (CKM), consisting of four subunits including MED12 and CDK8, plays a negative or positive role in the regulation of transcription; however, its involvement in HSF1-mediated transcription remains unclear. We herein demonstrated that HSF1 interacted with MED12 and recruited MED12 and CDK8 to the HSP70 promoter during heat shock in mammalian cells. The kinase activity of CDK8 (and its paralog CDK19) promoted HSP70 expression partly by phosphorylating HSF1-S326 and maintained proteostasis capacity. These results indicate an important role for CKM in the protection of cells against proteotoxic stress.

Rapamycin as a "One-Stone-Three-Birds" Agent for Cooperatively Enhanced Phototherapies Against Metastatic Breast Cancer

Cooperative photothermal therapy (PTT) and photodynamic therapy (PDT) represents a promising strategy to conquer tumor with synergistic effect, while their long-term efficacy has been strictly limited by the multiple resistances of tumor. Here, we reported a core-shell nanoplatform for enhanced PTT/PDT combination against metastatic breast cancer. The nanosystem had photosensitizer chlorin e6 (Ce6) and rapamycin (RAP) pure drugs core and the polydopamine (PDA) shell, with surface PEGylation. Notably, we found that RAP was a highly robust sensitizer to boost the efficacy of both PTT and PDT by inhibiting the expression of heat shock protein 70 (HSP 70) and hypoxia inducible factor-1α (HIF-1α), respectively, resulting in cooperatively enhanced antitumor efficiency. Moreover, metastasis, the fatal risk of breast cancer, was also inhibited by virtue of RAP-mediated matrix metalloproteinases-2 (MMP-2) suppression. Upon intravenous injection, the nanosystem could passively accumulate into the tumor and impose potent phototherapies upon dual laser irradiations for complete tumor elimination and metastasis inhibition, giving rise to 100% mice survival over a long observation period. Collectively, this work offers a general solution to address the key limitations of tumor-resistant phototherapies and provides a highly promising nanoplatform for the management of metastatic cancer.

Genotype and Trait Specific Responses to Rapamycin Intake in Drosophila melanogaster

Simple Summary

Rapamycin is commonly used as an immunosuppressant, but also as an anti-aging medicine. Despite its widespread use, results suggest that there is large variability in drug efficiency among patients, and limited knowledge exists about potential side-effects. In the present study, we investigated the effects of rapamycin using the common fruit fly as model organism. Six genetically distinct lines were exposed to rapamycin, and the phenotypic consequence on fecundity, longevity and heat stress tolerance was quantified. Flies exposed to rapamycin had increased longevity and heat stress tolerance, however a side effect in the form of decreased fecundity was also observed. Our data clearly show that the costs and benefits of rapamycin treatment is strongly genotype dependent. These observations are important as they imply that a ‘one size fits all’ approach when it comes to rapamycin treatment is not advisable. Future studies should address the underlying genetic component that drive the drug response variability.

Abstract

Rapamycin is a powerful inhibitor of the TOR (Target of Rapamycin) pathway, which is an evolutionarily conserved protein kinase, that plays a central role in plants and animals. Rapamycin is used globally as an immunosuppressant and as an anti-aging medicine. Despite widespread use, treatment efficiency varies considerably across patients, and little is known about potential side effects. Here we seek to investigate the effects of rapamycin by using Drosophila melanogaster as model system. Six isogenic D. melanogaster lines were assessed for their fecundity, male longevity and male heat stress tolerance with or without rapamycin treatment. The results showed increased longevity and heat stress tolerance for male flies treated with rapamycin. Conversely, the fecundity of rapamycin-exposed individuals was lower than for flies from the non-treated group, suggesting unwanted side effects of the drug in D. melanogaster. We found strong evidence for genotype-by-treatment interactions suggesting that a ‘one size fits all’ approach when it comes to treatment with rapamycin is not recommendable. The beneficial responses to rapamycin exposure for stress tolerance and longevity are in agreement with previous findings, however, the unexpected effects on reproduction are worrying and need further investigation and question common believes that rapamycin constitutes a harmless drug.

The functions and regulation of heat shock proteins; key orchestrators of proteostasis and the heat shock response

Cells respond to protein-damaging (proteotoxic) stress by activation of the Heat Shock Response (HSR). The HSR provides cells with an enhanced ability to endure proteotoxic insults and plays a crucial role in determining subsequent cell death or survival. The HSR is, therefore, a critical factor that influences the toxicity of protein stress. While named for its vital role in the cellular response to heat stress, various components of the HSR system and the molecular chaperone network execute essential physiological functions as well as responses to other diverse toxic insults. The effector molecules of the HSR, the Heat Shock Factors (HSFs) and Heat Shock Proteins (HSPs), are also important regulatory targets in the progression of neurodegenerative diseases and cancers. Modulation of the HSR and/or its extended network have, therefore, become attractive treatment strategies for these diseases. Development of effective therapies will, however, require a detailed understanding of the HSR, important features of which continue to be uncovered and are yet to be completely understood. We review recently described and hallmark mechanistic principles of the HSR, the regulation and functions of HSPs, and contexts in which the HSR is activated and influences cell fate in response to various toxic conditions.

Inhibition of HSF1 and SAFB Granule Formation Enhances Apoptosis Induced by Heat Stress

Stress resistance mechanisms include upregulation of heat shock proteins (HSPs) and formation of granules. Stress-induced granules are classified into stress granules and nuclear stress bodies (nSBs). The present study examined the involvement of nSB formation in thermal resistance. We used chemical compounds that inhibit heat shock transcription factor 1 (HSF1) and scaffold attachment factor B (SAFB) granule formation and determined their effect on granule formation and HSP expression in HeLa cells. We found that formation of HSF1 and SAFB granules was inhibited by 2,5-hexanediol. We also found that suppression of HSF1 and SAFB granule formation enhanced heat stress-induced apoptosis. In addition, the upregulation of HSP27 and HSP70 during heat stress recovery was suppressed by 2,5-hexanediol. Our results suggested that the formation of HSF1 and SAFB granules was likely to be involved in the upregulation of HSP27 and HSP70 during heat stress recovery. Thus, the formation of HSF1 and SAFB granules was involved in thermal resistance.

The stress-responsive kinase DYRK2 activates heat shock factor 1 promoting resistance to proteotoxic stress

To survive proteotoxic stress, cancer cells activate the proteotoxic-stress response pathway, which is controlled by the transcription factor heat shock factor 1 (HSF1). This pathway supports cancer initiation, cancer progression and chemoresistance and thus is an attractive therapeutic target. As developing inhibitors against transcriptional regulators, such as HSF1 is challenging, the identification and targeting of upstream regulators of HSF1 present a tractable alternative strategy. Here we demonstrate that in triple-negative breast cancer (TNBC) cells, the dual specificity tyrosine-regulated kinase 2 (DYRK2) phosphorylates HSF1, promoting its nuclear stability and transcriptional activity. DYRK2 depletion reduces HSF1 activity and sensitises TNBC cells to proteotoxic stress. Importantly, in tumours from TNBC patients, DYRK2 levels positively correlate with active HSF1 and associates with poor prognosis, suggesting that DYRK2 could be promoting TNBC. These findings identify DYRK2 as a key modulator of the HSF1 transcriptional programme and a potential therapeutic target.

Rhein Suppresses Colorectal Cancer Cell Growth by Inhibiting the mTOR Pathway In Vitro and In Vivo

Colorectal cancer (CRC) is one of the leading causes of mortality and morbidity in the world. Rhein has demonstrated therapeutic effects in various cancer models. However, its effects and underlying mechanisms of action in CRC remain poorly understood. We investigated the potential anticancer activity and underlying mechanisms of rhein in CRC in vitro and in vivo. Cell viability and anchorage-independent colony formation assays were performed to examine the antigrowth effects of rhein on CRC cells. Wound-healing and Transwell assays were conducted to assess cell migration and invasion capacity. Cell cycle and apoptosis were investigated by flow cytometry and verified by immunoblotting. A tissue microarray was used to detect mTOR expression in CRC patient tissues. Gene overexpression and knockdown were done to analyze the function of mTOR in CRC. The anticancer effect of rhein in vivo was assessed in a CRC xenograft mouse model. The results show that rhein significantly inhibited CRC cell growth by inducing S-phase cell cycle arrest and apoptosis. Rhein inhibited CRC cell migration and invasion through the epithelial-mesenchymal transition (EMT) process. mTOR was highly expressed in CRC cancer tissues and cells. Overexpression of mTOR promoted cell growth, migration, and invasion, whereas mTOR knockdown diminished these phenomena in CRC cells in vitro. In addition, rhein directly targeted mTOR and inhibited the mTOR signaling pathway in CRC cells. Rhein promoted mTOR degradation through the ubiquitin-proteasome pathway. Intraperitoneal administration of rhein inhibited HCT116 xenograft tumor growth through the mTOR pathway. In conclusion, rhein exerts anticancer activity in vitro and in vivo by targeting mTOR and inhibiting the mTOR signaling pathway in CRC. Our results indicate that rhein is a potent anticancer agent that may be useful for the prevention and treatment of CRC.

Andrographolide upregulates protein quality control mechanisms in cell and mouse through upregulation of mTORC1 function

BACKGROUND

Heat shock response (HSR), a component of cellular protein quality control mechanisms, is defective in different neurodegenerative conditions such as Parkinson's disease (PD). Forced upregulation of heat shock factor 1 (HSF1), an HSR master regulator, showed therapeutic promise in PD models. Many of the reported small-molecule HSF1 activators have limited functions. Therefore, identification and understanding the molecular bases of action of new HSF1 activating molecules is necessary.

METHOD

We used a cell-based reporter system to screen Andrographis paniculata leaf extract to isolate andrographolide as an inducer of HSF1 activity. The andrographolide activity was characterized by analyzing its role in different protein quality control mechanisms.

RESULT

We find that besides ameliorating the PD in MPTP-treated mice, andrographolide upregulated different machineries controlled by HSF1 and NRF2 in both cell and mouse brain. Andrographolide achieves these functions through mTORC1 activated via p38 MAPK and ERK pathways. NRF2 activation is reflected in the upregulation of proteasome as well as autophagy pathways. We further show that NRF2 activation is mediated through mTORC1 driven phosphorylation of p62/sequestosome 1. Studies with different cell types suggested that andrographolide-mediated induction of ROS level underlies all these activities in agreement with the upregulation of mTORC1 and NRF2-antioxidant pathway in mice.

CONCLUSION

Andrographolide through upregulating HSF1 activity ameliorates protein aggregation induced cellular toxicity.

GENERAL SIGNIFICANCE

Our results provide a reasonable basis for use of andrographolide in the therapy regimen for the treatment of PD.

Heat shock factor 1 (HSF1-pSer326) predicts response to bortezomib-containing chemotherapy in pediatric AML: a COG report

Bortezomib (BTZ) was recently evaluated in a randomized phase 3 clinical trial by the Children's Oncology Group (COG) that compared standard chemotherapy (cytarabine, daunorubicin, and etoposide [ADE]) vs standard therapy with BTZ (ADEB) for de novo pediatric acute myeloid leukemia (AML). Although the study concluded that BTZ did not improve outcome overall, we examined patient subgroups benefiting from BTZ-containing chemotherapy using proteomic analyses. The proteasome inhibitor BTZ disrupts protein homeostasis and activates cytoprotective heat shock responses. Total heat shock factor 1 (HSF1) and phosphorylated HSF1 (HSF1-pSer326) were measured in leukemic cells from 483 pediatric patients using reverse phase protein arrays. HSF1-pSer326 phosphorylation was significantly lower in pediatric AML compared with CD34+ nonmalignant cells. We identified a strong correlation between HSF1-pSer326 expression and BTZ sensitivity. BTZ significantly improved outcome of patients with low-HSF1-pSer326 with a 5-year event-free survival of 44% (ADE) vs 67% for low-HSF1-pSer326 treated with ADEB (P = .019). To determine the effect of HSF1 expression on BTZ potency in vitro, cell viability with HSF1 gene variants that mimicked phosphorylated (S326A) and nonphosphorylated (S326E) HSF1-pSer326 were examined. Those with increased HSF1 phosphorylation showed clear resistance to BTZ vs those with wild-type or reduced HSF1-phosphorylation. We hypothesize that HSF1-pSer326 expression could identify patients who benefit from BTZ-containing chemotherapy.

Effect of Heat Stress on Dairy Cow Performance and on Expression of Protein Metabolism Genes in Mammary Cells

Simple Summary

Environmental temperatures are increasing, and consequent global warming also has negative effects on dairy cattle farms, which may result in reduced production and poorer milk quality. The protein content of casein, in particular, is important in influencing the coagulation properties of milk and, therefore, the production and quality of cheese. The aim of this study was to assess the effect of heat stress on animal performance and on the expression of selected genes involved in milk protein metabolism. Eight dairy cows were kept under thermoneutral conditions for 8 days. The same animals were then maintained under mild heat stress conditions for an additional 8 days. The results of this study revealed that mild heat stress reduced the feed intake and performance of dairy cows in terms of milk and protein yield, but not the expression of the target genes involved in milk protein metabolism, such as those coding for caseins.

Abstract

The aim of this study was to assess the effect of heat stress on dairy cow performance and on the expression of selected genes involved in milk protein metabolism. Eight Italian Holstein Friesian cows were kept under thermoneutral conditions (temperature–humidity index (THI) < 72, CON) for 8 days and under mild heat stress conditions (72 < THI < 78, HS) for an additional 8 days. The rectal temperature, feed intake, and milk yield were recorded during the last 3 days of the CON and HS periods. During the same time period, milk samples were collected to assess the composition and expression of selected genes involved in milk protein metabolism. Gene expression analyses were performed on somatic cells from milk, which are representative of mammary tissue. In terms of dairy cow performance, HS resulted in lower milk and protein yields and feed intake but higher rectal temperature than for CON (p < 0.05). Under HS, there were greater abundances of HSPA1A (p < 0.05) and BCL2 (p < 0.05), compared to CON, but similar levels of CSN2 (p > 0.05), CSN3 (p > 0.05), HSPA8 (p > 0.05), and STAT5B (p > 0.05) mRNA. Mild heat stress reduced the performance of dairy cows without affecting the expression of genes coding for caseins.

Hsp70 in cancer: A double agent in the battle between survival and death

The heat shock protein (Hsps) superfamily, also known as molecular chaperones, are highly conserved and present in all living organisms and play vital roles in protein fate. The HspA1A (Hsp70-1), called Hsp70 in this review, is expressed at low or undetectable levels in most unstressed normal cells, but numerous studies have shown that diverse types of tumor cells express Hsp70 at the plasma membrane that leads to resistance to programmed cell death and tumor progression. Hsp70 is released into the extracellular milieu in three forms including free soluble, complexed with cancer antigenic peptides, and exosome forms. Therefore, it seems to be a promising therapeutic target in human malignancies. However, a great number of studies have indicated that both intracellular and extracellular Hsp70 have a dual function. A line of evidence presented that intracellular Hsp70 has a cytoprotective function via suppression of apoptosis and lysosomal cell death (LCD) as well as that extracellular Hsp70 can promote tumorigenesis and angiogenesis. Other evidence showed intracellular Hsp70 can promote apoptosis and membrane-associated/extracellular Hsp70 can elicit antitumor innate and adaptive immune responses. Given the contradictory functions, as a "double agent," could Hsp70 be a promising tool in the future of targeted cancer therapies? To answer this question, in this review, we will discuss the functions of Hsp70 in cancers besides inhibition and stimulation strategies for targeting Hsp70 along with their challenges.

HSF1 as a Cancer Biomarker and Therapeutic Target

Heat shock factor 1 (HSF1) was discovered in 1984 as the master regulator of the heat shock response. In this classical role, HSF1 is activated following cellular stresses such as heat shock that ultimately lead to HSF1-mediated expression of heat shock proteins to protect the proteome and survive these acute stresses. However, it is now becoming clear that HSF1 also plays a significant role in several diseases, perhaps none more prominent than cancer. HSF1 appears to have a pleiotropic role in cancer by supporting multiple facets of malignancy including migration, invasion, proliferation, and cancer cell metabolism among others. Because of these functions, and others, of HSF1, it has been investigated as a biomarker for patient outcomes in multiple cancer types. HSF1 expression alone was predictive for patient outcomes in multiple cancer types but in other instances, markers for HSF1 activity were more predictive. Clearly, further work is needed to tease out which markers are most representative of the tumor promoting effects of HSF1. Additionally, there have been several attempts at developing small molecule inhibitors to reduce HSF1 activity. All of these HSF1 inhibitors are still in preclinical models but have shown varying levels of efficacy at suppressing tumor growth. The growth of research related to HSF1 in cancer has been enormous over the last decade with many new functions of HSF1 discovered along the way. In order for these discoveries to reach clinical impact, further development of HSF1 as a biomarker or therapeutic target needs to be continued.

Redefining proteostasis transcription factors in organismal stress responses, development, metabolism, and health

Eukaryotic organisms have evolved complex and robust cellular stress response pathways to ensure maintenance of proteostasis and survival during fluctuating environmental conditions. Highly conserved stress response pathways can be triggered and coordinated at the cell-autonomous and cell-nonautonomous level by proteostasis transcription factors, including HSF1, SKN-1/NRF2, HIF1, and DAF-16/FOXO that combat proteotoxic stress caused by environmental challenges. While these transcription factors are often associated with a specific stress condition, they also direct “noncanonical” transcriptional programs that serve to integrate a multitude of physiological responses required for development, metabolism, and defense responses to pathogen infections. In this review, we outline the established function of these key proteostasis transcription factors at the cell-autonomous and cell-nonautonomous level and discuss a newly emerging stress responsive transcription factor, PQM-1, within the proteostasis network. We look beyond the canonical stress response roles of proteostasis transcription factors and highlight their function in integrating different physiological stimuli to maintain cytosolic organismal proteostasis.

Emerging roles of HSF1 in cancer: Cellular and molecular episodes

Heat shock factor 1 (HSF1) systematically guards proteome stability and proteostasis by regulating the expression of heat shock protein (HSP), thus rendering cancer cells addicted to HSF1. The non-canonical transcriptional programme driven by HSF1, which is distinct from the heat shock response (HSR), plays an indispensable role in the initiation, promotion and progression of cancer. Therefore, HSF1 is widely exploited as a potential therapeutic target in a broad spectrum of cancers. Various molecules and signals in the cell jointly regulate the activation and attenuation of HSF1. The high-level expression of HSF1 in tumours and its relationship with patient prognosis imply that HSF1 can be used as a biomarker for patient prognosis and a target for cancer treatment. In this review, we discuss the newly identified mechanisms of HSF1 activation and regulation, the diverse functions of HSF1 in tumourigenesis, and the feasibility of using HSF1 as a prognostic marker. Disrupting cancer cell proteostasis by targeting HSF1 represents a novel anti-cancer therapeutic strategy.

Identification of Genomic Characteristics and Selective Signals in a Du'an Goat Flock

The Du'an goat is one of the most important farm animals in the Guangxi Autonomous Region of China, but the genetic basis underlying its adaptive traits has still not been investigated. Firstly, in this study, the genomes of 15 Du'an goats from a breeding farm were sequenced (mean depth: 9.50X) to analyze the patterns of genetic variation. A comparable diversity (17.3 million single nucleotide polymorphisms and 2.1 million indels) was observed to be associated with a lower runs of homozygosity-based inbreeding coefficient and smaller effective population size in comparison with other breeds. From selective sweep and gene set enrichment analyses, we revealed selective signals related to adaptive traits, including immune resistance (serpin cluster, INFGR1, TLR2, and immune-related pathways), body size (HMGA2, LCOR, ESR1, and cancer-related pathways) and heat tolerance (MTOR, ABCG2, PDE10A, and purine metabolism pathway). Our findings uncovered the unique diversity at the genomic level and will provide the opportunities for improvement of productivity in the Du'an goat.

A molecular perspective on age-dependent changes to the heat shock axis

Aging is a complex process associated with progressive damage that leads to cellular dysfunction often accompanied by frailty and age-related diseases. Coping with all types of physiologic stress declines with age. While representing a primordial, cross-species response in poikilo- and homeotherms, the age-dependent perturbation of the stress response is more complex than previously thought. This short review examines how age influences the stress axis at multiple levels that involve both activating and attenuating pathways.

Hyperthermia and protein homeostasis: Cytoprotection and cell death

Protein homeostasis or proteostasis, the correct balance between production and degradation of proteins, is an essential pillar for proper cellular function. Among the several cellular mechanisms that disrupt homeostatic conditions in cancer cells, hyperthermia (HT) has shown promising anti-tumor effects. However, cancer cells are also capable of thermoresistance. Indeed, HT-induced protein denaturation and aggregation results in the up regulation of heat shock proteins, a group of molecular chaperones with cytoprotective and anti-apoptotic properties via stress-inducible transcription factor, heat shock factor 1(HSF1). Heat shock proteins assist in the refolding of misfolded proteins and aids in their elimination if they become irreversibly damaged by various stressors. Furthermore, HSF1 also initiates the unfolded protein response in the endoplasmic reticulum (ER) to assist in the protein folding capacity of ER and also promotes the translation of pro-survival proteins' mRNA such as activating transcription factor 4 (ATF 4). Moreover, HT associated induction of microRNAs is also involved in thermal resistance of cancer cells via up-regulation of anti-apoptotic Bcl-2 proteins and down regulation of pro-apoptotic Bax and caspase 3 activities. Another cellular protection in response to stressors is Autophagy, which is regulated by the Mammalian target of rapamycin (mTOR) protein. Kinase activity in mTOR phosphorylates HSF1 and promotes its nuclear translocation for heat shock protein synthesis. Over-expression of heat shock proteins are reported to up-regulate Beclin-1, an autophagy initiator. Moreover, HT-induced reactive oxygen species (ROS) generation is sensitized by transcription factor NF-E2 related factor 2 (Nrf2) and activates the cellular expression of antioxidants and autophagy gene. Furthermore, ROS also potentiates autophagy via activation of Beclin-1. Inhibition of thermotolerance can potentiate HT-induced apoptosis. Here, we outlined that heat stress alters cellular proteins which activates cellular homeostatic processes to promote cell survival and make cancer cells thermotolerant.