Heat shock factor 1 is required for migration and invasion of human melanoma in vitro and in vivo

Targeting the heat shock response induced by modulated electro-hyperthermia (mEHT) in cancer

The Heat Shock Response (HSR) is a cellular stress reaction crucial for cell survival against stressors, including heat, in both healthy and cancer cells. Modulated electro-hyperthermia (mEHT) is an emerging non-invasive cancer therapy utilizing electromagnetic fields to selectively target cancer cells via temperature-dependent and independent mechanisms. However, mEHT triggers HSR in treated cells. Despite demonstrated efficacy in cancer treatment, understanding the underlying molecular mechanisms for improved therapeutic outcomes remains a focus. This review examines the HSR induced by mEHT in cancer cells, discussing potential strategies to modulate it for enhanced tumor-killing effects. Approaches such as HSF1 gene-knockdown and small molecule inhibitors like KRIBB11 are explored to downregulate the HSR and augment tumor destruction. We emphasize the impact of HSR inhibition on cancer cell viability, mEHT sensitivity, and potential synergistic effects, addressing challenges and future directions. This understanding offers opportunities for optimizing treatment strategies and advancing precision medicine in cancer therapy.

Monocarboxylate transporter 4 promotes the migration of non‑cancerous L929 fibroblast cells by activating the IGF1/IGF1R/PIK3R3/SGK1 axis

The tumor microenvironment (TME) and Warburg effect are critical for the regulation of tumor metastasis. The monocarboxylate transporter (MCT) family members, particularly MCT4, which is encoded by the solute carrier family 16 member 3 gene, play an important role in the regulation of the TME and mediation of the Warburg effect by transporting lactate out of cancer cells. Migration and invasion are two key features of metastasis. Few studies have investigated the mechanism by which MCT4 promotes cell migration, and the suggested mechanisms by which MCT4 promotes migration vary in different tumor cell models. The purpose of the present study was to use non-cancerous cells as a research model to investigate the specific mechanism underlying the promotion of migration by MCT4. In a previous study, murine L929 cells overexpressing human MCT4 (MCT4-L929 cells) were generated and MCT4 was demonstrated to promote the migration and invasion of these non-cancerous cells. In the present study, MCT4-L929 cells and control-L929 cells were used to investigate the potential pathways and mechanisms through which MCT4 promotes cell migration. RNA sequencing analysis revealed 872 differentially expressed genes, comprising 337 and 535 upregulated and downregulated genes, respectively, in the MCT4-L929 cells. Reverse transcription-quantitative analysis and western blotting revealed that MCT4 overexpression increased the transcription and protein levels of insulin-like growth factor 1 (IGF1). In a wound healing assay, the migration of exogenous mouse IGF1-treated control-L929 cells was similar to that of MCT4-L929 cells. Additionally, the inhibition of IGF1 receptor (IGF1R) or serum/glucocorticoid regulated kinase 1 (SGK1), a downstream protein in the IGF1 and phosphoinositide 3-kinase PI3K regulatory subunit 3 (PIK3R3) pathways, in MCT4-L929 cells mitigated the cell migration-promoting effect of MCT4. These novel findings suggest that MCT4 may promote the migration of L929 fibroblast cells via activation of the IGF1/IGF1R/PIK3R3/SGK1 axis.

Hsp90 Inhibitor STA9090 induced VPS35 related extracellular vesicle release and metastasis in hepatocellular carcinoma

Heat shock protein 90 (Hsp90) has been an important therapeutic target for cancer therapy for decades. Unexpectedly, the monotherapy of N-terminal Hsp90 inhibitor STA9090 related clinical trials halted in phase III, and metastases were reported in animal models with the treatment of N-terminal Hsp90 inhibitors. Vacuolar protein sorting-associated protein 35 (VPS35) plays a vital role in endosome-derived EV (extracellular vesicle) traffic in neurodegeneration diseases, but no vps35 related EV were reported in tumors till now. Since tumor derived EVs contributes to metastasis and VPS35 is recently found to be involved in the invasion and metastasis of hepatocellular carcinoma (HCC), whether N-terminal Hsp90 inhibitor STA9090 induced EVs generation and the role of VPS35 in it were explored in this study. We found that N-terminal Hsp90 inhibitor STA9090 upregulated Bclaf1 and VPS35 levels, increased the secretion of EVs, and STA9090-induced-EVs promoted the invasion of HepG2 cells. As the clinical data suggested that the increased Bclaf1 and VPS35 levels correlated with increased metastasis and poorer prognosis in HCC, we focused on the Bclaf1-VPS35-EVs axis to further explore the mechanism of VPS35-related metastasis. The results demonstrated that Bclaf1 facilitated the transcription of VPS35 via bZIP domain, and knockdown of Bclaf1 or VPS35 alleviated pro-metastatic capability of STA9090-induced-EVs. All the results revealed the role of Bclaf1-VPS35-EVs axis on metastasis of HCC, and VPS35 knockdown decreased Hsp90 Inhibitor STA9090 induced extracellular vesicle release and metastasis, which provided a new combination therapeutic strategy to inhibit the metastasis of HCC caused by N-terminal Hsp90 inhibitor induced extracellular vesicles.

Heat Shock Proteins and HSF1 in Cancer

Fitness of cells is dependent on protein homeostasis which is maintained by cooperative activities of protein chaperones and proteolytic machinery. Upon encountering protein-damaging conditions, cells activate the heat-shock response (HSR) which involves HSF1-mediated transcriptional upregulation of a group of chaperones - the heat shock proteins (HSPs). Cancer cells experience high levels of proteotoxic stress due to the production of mutated proteins, aneuploidy-induced excess of components of multiprotein complexes, increased translation rates, and dysregulated metabolism. To cope with this chronic state of proteotoxic stress, cancers almost invariably upregulate major components of HSR, including HSF1 and individual HSPs. Some oncogenic programs show dependence or coupling with a particular HSR factor (such as frequent coamplification of HSF1 and MYC genes). Elevated levels of HSPs and HSF1 are typically associated with drug resistance and poor clinical outcomes in various malignancies. The non-oncogene dependence ("addiction") on protein quality controls represents a pancancer target in treating human malignancies, offering a potential to enhance efficacy of standard and targeted chemotherapy and immune checkpoint inhibitors. In cancers with specific dependencies, HSR components can serve as alternative targets to poorly druggable oncogenic drivers.

ErbB2 promotes breast cancer metastatic potential via HSF1/LDHA axis-mediated glycolysis

ErbB2 is overexpressed in approximately 25% of breast cancer cases and promotes metastatic potential. We previously reported that ErbB2 promoted glycolysis via heat shock factor 1 (HSF1)/lactate dehydrogenase A (LDHA) axis and ErbB2-mediated glycolysis was required for the growth of breast cancer cells. However, the importance of HSF1/LDHA axis-mediated glycolysis in ErbB2-enhanced metastatic potential remains to be elucidated. In this study, we investigated the effect of HSF1/LDHA axis-mediated glycolysis on migration and invasion in breast cancer cells. Firstly, we demonstrated that ErbB2-mediated migration and invasion were dependent on glycolysis in breast cancer cells. Secondly, we found that HSF1/LDHA axis played an important role in glycolysis, which contributed to ErbB2-enhanced migration and invasion. Finally, we showed that ErbB2 was positively correlated with HSF1/LDHA axis in invasive breast cancer patients via GEO analysis. Taken together, ErbB2 promoted metastatic potential of breast cancer cells via HSF1/LDHA axis-mediated glycolysis. And our findings indicated that targeting HSF1/LDHA axis may be a promising strategy to treat ErbB2-overexpressing breast cancer patients.

Is cancer a disease set up by cellular stress responses?

For several decades, the somatic mutation theory (SMT) has been the dominant paradigm on cancer research, leading to the textbook notion that cancer is fundamentally a genetic disease. However, recent discoveries indicate that mutations, including "oncogenic" ones, are widespread in normal somatic cells, suggesting that mutations may be necessary but not sufficient for cancer to develop. Indeed, a fundamental but as yet unanswered question is whether or not the first step in oncogenesis corresponds to a mutational event. On the other hand, for some time, it has been acknowledged the important role in cancer progression of molecular processes that participate in buffering cellular stress. However, their role is considered secondary or complementary to that of putative oncogenic mutations. Here we present and discuss evidence that cancer may have its origin in epigenetic processes associated with cellular adaptation to stressful conditions, and so it could be a direct consequence of stress-buffering mechanisms that allow cells with aberrant phenotypes (not necessarily associated with genetic mutations) to survive and propagate within the organism. We put forward the hypothesis that there would be an inverse correlation between the activation threshold of the cellular stress responses (CSRs) and the risk of cancer, so that species or individuals with low-threshold CSRs will display a higher incidence or risk of cancer.

The Multifaceted Role of HSF1 in Pathophysiology: Focus on Its Interplay with TG2

The cellular environment needs to be strongly regulated and the maintenance of protein homeostasis is crucial for cell function and survival. HSF1 is the main regulator of the heat shock response (HSR), the master pathway required to maintain proteostasis, as involved in the expression of the heat shock proteins (HSPs). HSF1 plays numerous physiological functions; however, the main role concerns the modulation of HSPs synthesis in response to stress. Alterations in HSF1 function impact protein homeostasis and are strongly linked to diseases, such as neurodegenerative disorders, metabolic diseases, and different types of cancers. In this context, type 2 Transglutaminase (TG2), a ubiquitous enzyme activated during stress condition has been shown to promote HSF1 activation. HSF1-TG2 axis regulates the HSR and its function is evolutionary conserved and implicated in pathological conditions. In this review, we discuss the role of HSF1 in the maintenance of proteostasis with regard to the HSF1-TG2 axis and we dissect the stress response pathways implicated in physiological and pathological conditions.

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.

Dissecting the Functional Mechanisms of Somatic Copy-Number Alterations Based on Dysregulated ceRNA Networks across Cancers

Somatic copy-number alterations (SCNAs) drive tumor growth and evolution. However, the functional roles of SCNAs across the genome are still poorly understood. We provide an integrative strategy to characterize the functional roles of driver SCNAs in cancers based on dysregulated competing endogenous RNA (ceRNA) networks. We identified 44 driver SCNAs in lower-grade glioma (LGG). The dysregulated patterns losing all correlation relationships dominated dysregulated ceRNA networks. Homozygous deletion of six genes in 9p21.3 characterized an LGG subtype with poor prognosis and contributed to the dysfunction of cancer-associated pathways in a complementary way. The pan-cancer analysis showed that different cancer types harbored different driver SCNAs through dysregulating the crosstalk with common ceRNAs. The same SCNAs destroyed their ceRNA networks through different miRNA-mediated ceRNA regulations in different cancers. Additionally, some SCNAs performed different functional mechanisms in different cancers, which added another layer of complexity to cancer heterogeneity. Compared with previous methods, our strategy could directly dissect functional roles of SCNAs from the view of ceRNA networks, which not only complemented the functions of protein-coding genes but also provided a new avenue to characterize the functions of noncoding RNAs. Also, our strategy could be applied to more types of cancers to identify pathogenic mechanism driven by the SCNAs.

Identification of a natural compound, sesamin, as a novel TRPM8 antagonist with inhibitory effects on prostate adenocarcinoma

Transient receptor potential melastatin 8 (TRPM8) is a calcium ion-permeable cation channel that is used as a prognostic marker and therapeutic target for different tumor types. To identify natural selective TRPM8 antagonists, we tested 158 traditional Chinese medicine (TCM) compounds for the ability to inhibit TRPM8. Calcium mobilization assays were used to evaluate the 158 TCM compound components in HEK293 cells stably expressing TRPM8. An identified putative TRPM8 antagonist, sesamin, was further evaluated. Publicly available cancer OMICS data were used to explore the expression of TRPM8, its gene regulatory network, and the survival of patients with prostate adenocarcinoma (PRAD). The cytotoxicity and specificity of sesamin to TRPM8 were tested in HEK293/TRPM8 cells. The effect of sesamin on cell proliferation in PRAD cell lines was assessed. Sesamin selectively inhibited TRPM8 in HEK293/TRPM8 cells (IC50: 9.78 μM), and a molecular docking study confirmed the binding of sesamin to TRPM8. TRPM8 was highly overexpressed in PRAD, and high TRPM8 expression was associated with poor survival of PRAD patients. Functional network analysis suggested that TRPM8 has key effects on proliferation, survival, and invasion of prostate cancer cells. Cell proliferation assays supported these findings and showed that sesamin inhibited the proliferation of PRAD cell lines DU145 and LNCaP cells. These data revealed that abnormal TRPM8 expression is associated with PRAD and that sesamin is a new anti-PRAD candidate drug, exerting inhibitory effects on TRPM8.

HSF1: Primary Factor in Molecular Chaperone Expression and a Major Contributor to Cancer Morbidity

Heat shock factor 1 (HSF1) is the primary component for initiation of the powerful heat shock response (HSR) in eukaryotes. The HSR is an evolutionarily conserved mechanism for responding to proteotoxic stress and involves the rapid expression of heat shock protein (HSP) molecular chaperones that promote cell viability by facilitating proteostasis. HSF1 activity is amplified in many tumor contexts in a manner that resembles a chronic state of stress, characterized by high levels of HSP gene expression as well as HSF1-mediated non-HSP gene regulation. HSF1 and its gene targets are essential for tumorigenesis across several experimental tumor models, and facilitate metastatic and resistant properties within cancer cells. Recent studies have suggested the significant potential of HSF1 as a therapeutic target and have motivated research efforts to understand the mechanisms of HSF1 regulation and develop methods for pharmacological intervention. We review what is currently known regarding the contribution of HSF1 activity to cancer pathology, its regulation and expression across human cancers, and strategies to target HSF1 for cancer therapy.

The Multifaceted Role of HSF1 in Tumorigenesis

Heat Shock Factor 1 (HSF1), the master transcriptional regulator of the heat shock response (HSR), was first cloned more than 30 years ago. Most early research interrogating the role that HSF1 plays in biology focused on its cytoprotective functions, as a factor that promotes the survival of organisms by protecting against the proteotoxicity associated with neurodegeneration and other pathological conditions. However, recent studies have revealed a deleterious role of HSF1, as a factor that is co-opted by cancer cells to promote their own survival to the detriment of the organism. In cancer, HSF1 operates in a multifaceted manner to promote oncogenic transformation, proliferation, metastatic dissemination, and anti-cancer drug resistance. Here we review our current understanding of HSF1 activation and function in malignant progression and discuss the potential for HSF1 inhibition as a novel anticancer strategy. Collectively, this ever-growing body of work points to a prominent role of HSF1 in nearly every aspect of carcinogenesis.

SKA3 Promotes Cell Growth in Breast Cancer by Inhibiting PLK-1 Protein Degradation

Breast cancer (Bca) remains the most common form of malignancy affecting females in China, leading to significant reductions in the mental and physical health of those with this condition. While spindle and kinetochore associated complex subunit 3 (SKA3) is known to be linked with cervical cancer progression, whether it is similarly associated with Bca progression remains unknown. Using shRNA, we specifically knocked down the expression of SKA3 in Bca cell lines and then assessed the resultant changes in cell proliferation using CCK-8 and colony formation assays. In addition, we used western blotting to quantify the expression levels of relevant proteins in these cells, and we assessed the interaction between SKA3 and polo-like kinase-1 (PLK-1) via co-immunoprecipitation.In this study, we observed elevated SKA3 expression in Bca tissues and cell lines. When we knocked down SKA3 expression in Bca cells, we were able to determine that it functions in an oncogenic manner so as to promote the growth and proliferation of these cells in vitro. From a mechanistic perspective, we were able to show that in Bca cells SKA functions at least in part via interacting with PLK-1 and preventing its degradation. In summary, we found that SKA3 is able to regulate PLK-1 degradation in Bca cells, thus controlling their growth and proliferation. These results highlight SKA3 as a potentially viable target for anti-cancer drug development aimed at combatting Bca.

Inhibiting Heat Shock Factor 1 in Cancer: A Unique Therapeutic Opportunity

The ability of cancer cells to cope with stressful conditions is critical for their survival, proliferation, and metastasis. The heat shock transcription factor 1 (HSF1) protects cells from stresses such as chemicals, radiation, and temperature. These properties of HSF1 are exploited by a broad spectrum of cancers, which exhibit high levels of nuclear, active HSF1. Functions for HSF1 in malignancy extend well beyond its central role in protein quality control. While HSF1 has been validated as a powerful target in cancers by genetic knockdown studies, HSF1 inhibitors reported to date have lacked sufficient specificity and potency for clinical evaluation. We review the roles of HSF1 in cancer, its potential as a prognostic indicator for cancer treatment, evaluate current HSF1 inhibitors and provide guidelines for the identification of selective HSF1 inhibitors as chemical probes and for clinical development.

Heat shock factor 1 (HSF1)-targeted anticancer therapeutics: overview of current preclinical progress

INTRODUCTION

The heat shock factor 1 (HSF1) plays a pivotal role in guarding proteome stability or proteostasis by induction of heat shock proteins (HSPs). While HSF1 remains mostly latent in unstressed normal cells, it is constitutively active in malignant cells, rendering them addicted to HSF1 for their growth and survival. HSF1 affects tumorigenesis, cancer progression, and treatment resistance by preserving cancer proteostasis, thus suggesting disruption of HSF1 activity as a potential anticancer strategy. Areas covered: In this review, we focus on the HSF1 activation cycle and its interaction with HSPs, the role of HSF1 in oncogenesis, and development of HSF1-targeted drugs as a potential anticancer therapy for disrupting cancer proteostasis. Expert opinion: HSF1 systematically maintains proteostasis in malignant cancer cells. Although genomic instability is widely accepted as a hallmark of cancer, little is known about the role of proteostasis in cancer. Unveiling the complicated mechanism of HSF1 regulation, particularly in cancer cells, will enable further development of proteostasis-targeted anticancer therapy.

ABBREVIATIONS

AMPK: AMP-activated protein kinase; DBD: DNA-binding domain; HR-A/B; HR-C: heptad repeats; HSE: heat shock elements; HSF1: heat shock factor; HSPs: heat shock proteins; HSR: heat shock response; MEK: mitogen-activated protein kinase kinase; mTOR: mammalian target of rapamycin; NF1: neurofibromatosis type 1; P-TEFb: positive transcription elongation factor b; RD: regulatory domain; RNAi: RNA interference; TAD: transactivation domain; TRiC: TCP-1 ring complex.

The heat-shock, or HSF1-mediated proteotoxic stress, response in cancer: from proteomic stability to oncogenesis

The heat-shock, or HSF1-mediated proteotoxic stress, response (HSR/HPSR) is characterized by induction of heat-shock proteins (HSPs). As molecular chaperones, HSPs facilitate the folding, assembly, transportation and degradation of other proteins. In mammals, heat shock factor 1 (HSF1) is the master regulator of this ancient transcriptional programme. Upon proteotoxic insults, the HSR/HPSR is essential to proteome homeostasis, or proteostasis, thereby resisting stress and antagonizing protein misfolding diseases and ageing. Contrasting with these benefits, an unexpected pro-oncogenic role of the HSR/HPSR is unfolding. Whereas HSF1 remains latent in primary cells without stress, it becomes constitutively activated within malignant cells, rendering them addicted to HSF1 for their growth and survival. Highlighting the HSR/HPSR as an integral component of the oncogenic network, several key pathways governing HSF1 activation by environmental stressors are causally implicated in malignancy. Importantly, HSF1 impacts the cancer proteome systemically. By suppressing tumour-suppressive amyloidogenesis, HSF1 preserves cancer proteostasis to support the malignant state, both providing insight into how HSF1 enables tumorigenesis and suggesting disruption of cancer proteostasis as a therapeutic strategy. This review provides an overview of the role of HSF1 in oncogenesis, mechanisms underlying its constitutive activation within cancer cells and its pro-oncogenic action, as well as potential HSF1-targeting strategies.This article is part of the theme issue 'Heat shock proteins as modulators and therapeutic targets of chronic disease: an integrated perspective'.

Discovery and optimization of cardenolides inhibiting HSF1 activation in human colon HCT-116 cancer cells

Combinational anticancer therapy demonstrates increased efficiency, as it targets different cell-survival mechanisms and allows the decrease of drug dosages that are often toxic to normal cells. Inhibitors of the heat shock response (HSR) are known to reduce the efficiency of proteostasis mechanisms in many cancerous cells, and therefore, may be employed as anti-tumor drug complements. However, the application of HSR inhibitors is limited by their cytotoxicity, and we suggested that milder inhibitors may be employed to sensitize cancer cells to a certain drug. We used a heat-shock element-luciferase reporter system and discovered a compound, CL-43, that inhibited the levels of heat shock proteins 40, 70 (Hsp70), and 90 kDa in HCT-116 cells and was not toxic for cells of several lines, including normal human fibroblasts. Consequently, CL-43 was found to reduce colony formation and motility of HCT-116 in the appropriate assays suggesting its possible application in the exploration of biology of metastasizing tumors. Importantly, CL-43 elevated the growth-inhibitory and cytotoxic activity of etoposide, cisplatin, and doxorubicin suggesting that the pro-drug has broad prospect for application in a variety of anti-tumor therapy schedules.

A Futile Battle? Protein Quality Control and the Stress of Aging

There exists a phenomenon in aging research whereby early life stress can have positive impacts on longevity. The mechanisms underlying these observations suggest a robust, long-lasting induction of cellular defense mechanisms. These include the various unfolded protein responses of the endoplasmic reticulum (ER), cytosol, and mitochondria. Indeed, ectopic induction of these pathways, in the absence of stress, is sufficient to increase lifespan in organisms as diverse as yeast, worms, and flies. Here, we provide an overview of the protein quality control mechanisms that operate in the cytosol, mitochondria, and ER and discuss how they affect cellular health and viability during stress and aging.

Evaluation of in vitro and in vivo therapeutic antitumor efficacy of transduction of polo-like kinase 1 and heat shock transcription factor 1 small interfering RNA

Mitotic progression is regulated by the phosphorylation of heat shock transcription factor 1 (HSF1) by polo-like kinase 1 (PLK1); however, this interaction is often deregulated in tumors. High expression levels of PLK1 and HSF1 have been observed in various types of human cancer. In the present study, it was investigated whether small interfering (si)RNA against PLK1 or HSF1 could suppress tumor growth in vitro and in vivo. In vitro transfection of PLK1 and HSF1 siRNA into PKL1- and HSF1-positive human breast tumor MDA-MB-231 and human cervical carcinoma HeLa cells inhibited cell growth via suppression of PLK1 and HSF1 mRNA expression, respectively. However, the transfection of PLK1 or HSF1 siRNA did not significantly affect the cytotoxicity of doxorubicin in HeLa cells. Furthermore, injection of PKL1 or HSF1 siRNA into mice with liver HeLa metastasis suppressed tumor growth. From these findings, PLK1 and HSF1 may be considered to be promising targets for antitumor therapy.

Overexpression of the anti-apoptotic protein BAG3 in human choroidal melanoma: A case report

Bcl-2-associated athanogene 3 (BAG3), a co-chaperone of heat shock protein 70 (HSP70), exerts anti-apoptotic effects in various malignant tumors. However, relationships between choroidal melanoma and BAG3 are poorly studied. This study investigated the expression of BAG3 in a case of human choroidal melanoma. Funduscopy, computed tomography, and single-photon emission computed tomography with the intravenous injection of N-isopropyl-p-[¹²³I] iodoamphetamine strongly indicated choroidal melanoma in a 68-year-old woman. Accordingly, we carried out an enucleation and pathological diagnosis. Proteins and total RNA were extracted from normal retinochoroidal and tumor tissues. Proteins were also extracted from ocular nevus tissues of other patients. We examined the expression of BAG3 protein and mRNA using Western blotting and the real-time quantitative polymerase chain reaction, respectively. Immunohistochemical stains were positive for melan-A, HMB-45, and S-100. Histopathology confirmed a choroidal melanoma. The expression of BAG3 protein and mRNA in the choroidal melanoma tissue was upregulated with respect to both normal retinochoroidal tissue and ocular nevus tissues from other patients. Because BAG3 may inhibit apoptosis of choroidal melanoma and facilitate its survival, overexpression of this gene product may be a prognostic marker and therapeutic target.

The Heat Shock Transcription Factor HSF1 Induces Ovarian Cancer Epithelial-Mesenchymal Transition in a 3D Spheroid Growth Model

Ovarian cancer is the most lethal gynecological cancer, with over 200,000 women diagnosed each year and over half of those cases leading to death. The proteotoxic stress-responsive transcription factor HSF1 is frequently overexpressed in a variety of cancers and is vital to cellular proliferation and invasion in some cancers. Upon analysis of various patient data sets, we find that HSF1 is frequently overexpressed in ovarian tumor samples. In order to determine the role of HSF1 in ovarian cancer, inducible HSF1 knockdown cell lines were created. Knockdown of HSF1 in SKOV3 and HEY ovarian cancer cell lines attenuates the epithelial-to-mesenchymal transition (EMT) in cells treated with TGFβ, as determined by western blot and quantitative RT-PCR analysis of multiple EMT markers. To further explore the role of HSF1 in ovarian cancer EMT, we cultured multicellular spheroids in a non-adherent environment to simulate early avascular tumors. In the spheroid model, cells more readily undergo EMT; however, EMT inhibition by HSF1 becomes more pronounced in the spheroid model. These findings suggest that HSF1 is important in the ovarian cancer TGFβ response and in EMT.

Adapt, Recycle, and Move on: Proteostasis and Trafficking Mechanisms in Melanoma

Melanoma has emerged as a paradigm of a highly aggressive and plastic cancer, capable to co-opt the tumor stroma in order to adapt to the hostile microenvironment, suppress immunosurveillance mechanisms, and disseminate. In particular, oncogene- and aneuploidy-driven dysregulations of proteostasis in melanoma cells impose a rewiring of central proteostatic processes, such as the heat shock and unfolded protein responses, autophagy, and the endo-lysosomal system, to avoid proteotoxicity. Research over the past decade has indicated that alterations in key nodes of these proteostasis pathways act in conjunction with crucial oncogenic drivers to increase intrinsic adaptations of melanoma cells against proteotoxic stress, modulate the high metabolic demand of these cancer cells and the interface with other stromal cells, through the heightened release of soluble factors or exosomes. Here, we overview and discuss how key proteostasis pathways and vesicular trafficking mechanisms are turned into vital conduits of melanoma progression, by supporting cancer cell's adaptation to the microenvironment, limiting or modulating the ability to respond to therapy and fueling melanoma dissemination.

HSF1: Guardian of Proteostasis in Cancer

Proteomic instability is causally related to human diseases. In guarding proteome stability, the heat shock factor 1 (HSF1)-mediated proteotoxic stress response plays a pivotal role. Contrasting with its beneficial role of enhancing cell survival, recent findings have revealed a compelling pro-oncogenic role for HSF1. However, the mechanisms underlying the persistent activation and function of HSF1 within malignancy remain poorly understood. Emerging evidence reveals that oncogenic signaling mobilizes HSF1 and that cancer cells rely on HSF1 to avert proteomic instability and repress tumor-suppressive amyloidogenesis. In aggregate, these new developments suggest that cancer cells endure chronic proteotoxic stress and that proteomic instability is intrinsically associated with the malignant state, a characteristic that could be exploited to combat cancer.

Higher heat shock factor 1 expression in tumor stroma predicts poor prognosis in esophageal squamous cell carcinoma patients

Background

Heat shock factor 1 (HSF1) is a powerful, multifaceted modifier of carcinogenesis. However, the clinical significance and biologic function of HSF1 in esophageal squamous cell carcinoma (ESCC) remain unknown.

Methods

HSF1 was detected in ESCC cell lines, fibroblast cell lines and ESCC xenograft tumors and human ESCC tissues by real-time RT-PCR and western blotting. HSF1 protein expression was analyzed by immunochemistry in 134 ESCC patients followed by correlation with clinicopathological parameters.

Results

HSF1 expression is weak in fibroblast cell 3T3 and moderate in ESCC cell Eca109, but increasing expression of HSF1 was observed in both of 3T3 and Eca109 cells when they interplayed with each other. In Eca109 xenograft tumors, both tumor cells and stromal fibroblasts showed stronger expression of HSF1. In ESCC patients, the HSF1 expression in tumor or in stromal cells was significantly associated with tumor stage, lymph node metastasis and clinical stage. Multivariate analysis demonstrated a significant negative correlation between disease-free survival (DFS), overall survival (OS) and the HSF1 expression in stromal cells (P < 0.05) but not in tumor cells. Additionally, the expression of HSF1 in tumor cells or stromal cells was an independent factor for DFS (P = 0.032 or P = 0.012) and OS (P = 0.017 or P = 0.013) in metastatic ESCC patients but not for locoregional ESCC. ESCC patients with low HSF1 in both tumor cells and stromal cells had the longest survivals (P < 0.001).

Conclusions

The interaction of tumor cells and stromal fibroblasts increases the expression of HSF1 reciprocally in tumor microenvironment. The HSF1 expression in stromal cells was significantly associated with poor prognosis of ESCC.

Active heat shock transcription factor 1 supports migration of the melanoma cells via vinculin down-regulation

Heat shock transcription factor 1 (HSF1), the major regulator of stress response, is frequently activated in cancer and has an apparent role in malignant transformation. Here we analyzed the influence of the over-expression of a constitutively active transcriptionally-competent HSF1 mutant form on phenotypes of mouse and human melanoma cells. We observed that the expression of active HSF1 supported anchorage-independent growth in vitro, and metastatic spread in the animal model in vivo, although the proliferation rate of cancer cells was not affected. Furthermore, active HSF1 enhanced cell motility, reduced the adherence of cells to a fibronectin-coated surface, and affected the actin cytoskeleton. We found that although the expression of active HSF1 did not affect levels of epithelial-to-mesenchymal transition markers, it caused transcriptional down-regulation of vinculin, protein involved in cell motility, and adherence. Functional HSF1-binding sites were found in mouse and human Vcl/VCL genes, indicating a direct role of HSF1 in the regulation of this gene. An apparent association between HSF1-induced down-regulation of vinculin, increased motility, and a reduced adherence of cells suggests a possible mechanism of HSF1-mediated enhancement of the metastatic potential of cancer cells.