Heat shock factor 1 (HSF1) is highly expressed in various malignancies and is a potential modulator of tumor progression. Emerging evidence suggests that HSF1 activation in stromal cells is closely related to poor patient prognosis. However, the role of HSF1 in oral squamous cell carcinoma (OSCC) remains elusive. We aimed to investigate the function of HSF1 in cancer-associated fibroblasts (CAFs) of the tumor microenvironment (TME) and in tumor development. In the present study, we found that HSF1 was highly expressed in both CAFs and tumor cells, and was significantly correlated with poor prognosis and overall survival. Moreover, HSF1 overexpression in CAFs resulted in a fibroblast-like phenotype of Cal27 cells, induced epithelial-mesenchymal transition (EMT), and promoted proliferation, migration and invasion in Cal27 cells. HSF1 knockdown attenuated features of CAFs and reduced EMT, proliferation, migration and invasion in Cal27 cells. Furthermore, HSF1 in CAFs promoted tumor growth in nude mice. Taken together, these data suggest that HSF1 expression in CAFs drive OSCC progression, and could serve as an independent prognostic marker of patients with OSCC. Thus, HSF1 is a potent mediator of OSCC malignancy.

Aggressive behaviours of solid tumours are highly influenced by the tumour microenvironment. Multiple signalling pathways can affect the normal function of stromal fibroblasts in tumours, but how these events are coordinated to generate tumour-promoting cancer-associated fibroblasts (CAFs) is not well understood. Here we show that stromal expression of Dickkopf-3 (DKK3) is associated with aggressive breast, colorectal and ovarian cancers. We demonstrate that DKK3 is a HSF1 effector that modulates the pro-tumorigenic behaviour of CAFs in vitro and in vivo. DKK3 orchestrates a concomitant activation of β-catenin and YAP/TAZ. Whereas β-catenin is dispensable for CAF-mediated ECM remodelling, cancer cell growth and invasion, DKK3-driven YAP/TAZ activation is required to induce tumour-promoting phenotypes. Mechanistically, DKK3 in CAFs acts via canonical Wnt signalling by interfering with the negative regulator Kremen and increasing cell-surface levels of LRP6. This work reveals an unpredicted link between HSF1, Wnt signalling and YAP/TAZ relevant for the generation of tumour-promoting CAFs.

BACKGROUND/AIMS: Canopy homolog 2 (CNPY2) is a signature gene highly associated with tumor progression, including hepatocellular carcinoma (HCC). The presence of tumor hemorrhage (TH) implies a fast-growing and worse tumor microenvironment. We examined a possible association between CNPY2 levels and TH and evaluated their prognostic values in patients with HCC.
METHODS: CNPY2 mRNA and protein levels were respectively determined in two independent cohorts of HCC specimens using quantitative real-time polymerase chain reaction (qRT-PCR) and immunohistochemistry of tissue microarrays. Kaplan-Meier survival and Cox regression analyses were executed to evaluate the prognosis of HCC. CNPY2 knockout HCC cell lines were established by the CRISPR/Cas9 gene editing system, and the functional role of CNPY2 in HCC cell proliferation and growth was examined in vitro and in vivo.
RESULTS: qRT-PCR showed that CNPY2 expression was significantly higher in HCC tumor tissue than in adjacent non-tumor tissue. Immunohistochemistry of HCC tissue microarrays demonstrated that CNPY2 expression was significantly correlated with TH and clinicopathological features indicating worse HCC progression. The prognostic value of CNPY2 expression and TH was validated by Cox proportional hazards analyses. Furthermore, CNPY2 knockout resulted in the significant suppression of MHCC97H cell proliferation, tumor growth, and hemorrhage. Bioinformatics analysis revealed that CNPY2 was closely associated with the expression levels of 6 positive impact genes in HCC, namely, ROMO1, BOLA2, HSF1, ATG4B, ATF4, and DENR, which are implicated in the regulation of the tumor microenvironment.
CONCLUSION: CNPY2 is an oncogene that plays a critical role in the progression of HCC with TH. CNPY2 could be exploited as a novel prognostic marker and potential target for therapeutic intervention in HCC.

PURPOSE: Heat shock factor 1 (HSF1) is a key regulator of the heat shock response and plays an important role in various cancers. However, the role of HSF1 in gastric cancer is still unknown. The present study evaluated the function of HSF1 and related mechanisms in gastric cancer.
MATERIALS AND METHODS: The expression levels of HSF1 in normal and gastric cancer tissues were compared using cDNA microarray data from the NCBI Gene Expression Omnibus (GEO) dataset. The proliferation of gastric cancer cells was analyzed using the WST assay. Transwell migration and invasion assays were used to evaluate the migration and invasion abilities of gastric cancer cells. Protein levels of HSF1 were analyzed using immunohistochemical staining of tissue microarrays from patients with gastric cancer.
RESULTS: HSF1 expression was significantly higher in gastric cancer tissue than in normal tissue. Knockdown of HSF1 reduced the proliferation, migration, and invasion of gastric cancer cells, while HSF1 overexpression promoted proliferation, migration, and invasion of gastric cancer cells. Furthermore, HSF1 promoted the proliferation of gastric cancer cells
CONCLUSION: HSF1 may be closely associated with the proliferation and motility of gastric cancer cells and poor prognosis of patients with gastric cancer. Accordingly, HSF1 could serve as a prognostic marker for gastric cancer.

A previous genome-wide association study (GWAS) identified common variation at the BARD1 locus as being highly associated with susceptibility to high-risk neuroblastoma, but the mechanisms underlying this association have been not extensively investigated. Here, we performed a fine mapping analysis of BARD1 locus (2q35) using GWAS data from 556 high-risk neuroblastoma patients and 2,575 controls of European-American ancestry, and identified two independent genome-wide neuroblastoma-associated loci. Functional single-nucleotide polymorphism (SNP) prioritization identified two causative variants that independently contributed to neuroblastoma risk, and each replicated robustly in multiple independent cohorts comprising 445 high-risk cases and 3,170 controls (rs17489363: combined p = 1.07 × 10

Cellular transformation is accompanied by extensive rewiring of many biological processes leading to augmented levels of distinct types of cellular stress, including proteotoxic stress. Cancer cells critically depend on stress-relief pathways for their survival. However, the mechanisms underlying the transcriptional initiation and maintenance of the oncogenic stress response remain elusive. Here, we show that the expression of heat shock transcription factor 1 (HSF1) and the downstream mediators of the heat shock response is transcriptionally upregulated in T cell acute lymphoblastic leukemia (T-ALL). Hsf1 ablation suppresses the growth of human T-ALL and eradicates leukemia in mouse models of T-ALL, while sparing normal hematopoiesis. HSF1 drives a compact transcriptional program and among the direct HSF1 targets, specific chaperones and co-chaperones mediate its critical role in T-ALL. Notably, we demonstrate that the central T-ALL oncogene NOTCH1 hijacks the cellular stress response machinery by inducing the expression of HSF1 and its downstream effectors. The NOTCH1 signaling status controls the levels of chaperone/co-chaperone complexes and predicts the response of T-ALL patient samples to HSP90 inhibition. Our data demonstrate an integral crosstalk between mediators of oncogene and non-oncogene addiction and reveal critical nodes of the heat shock response pathway that can be targeted therapeutically.

In this study, we investigated the role of microRNA-644a (miR-644a) in the growth and survival of hepatocellular carcinoma (HCC) cells. MiR-644a levels were lower in HCC tissues than in adjacent peri-cancerous tissues (n = 135). MiR-644a expression was inversely correlated with heat shock factor 1 (HSF1) expression, tumour diameter and TNM stage. Moreover, HepG2 and SMMC-7721 cell lines showed lower miR-644a expression than normal L-O2 hepatocytes. MiR-644a overexpression in HepG2 and SMMC-7721 cells increased apoptosis by downregulating HSF1. Dual luciferase reporter assays confirmed the presence of a miR-644a binding site in the 3'-untranslated region (3'-UTR) of HSF1. Xenograft tumours derived from SMMC-7721 cells transfected with a miR-664a mimic showed less growth than tumours derived from untransfected controls. Protein chip analysis revealed that miR-644a-overexpressing SMMC-7721 and HepG2 cells strongly expressed pro-apoptotic BH3-only proteins, such as BID, BAD, BIM, SMAC, Apaf-1 and cleaved caspases-3 and -9. These findings suggest miR-644a promotes apoptosis in HCC cells by inhibiting HSF1.

Background: Treatment-induced neuroendocrine prostate cancer (tNEPC) is an aggressive variant of late-stage metastatic castrate-resistant prostate cancer that commonly arises through neuroendocrine transdifferentiation (NEtD). Treatment options are limited, ineffective, and, for most patients, result in death in less than a year. We previously developed a first-in-field patient-derived xenograft (PDX) model of NEtD. Longitudinal deep transcriptome profiling of this model enabled monitoring of dynamic transcriptional changes during NEtD and in the context of androgen deprivation. Long non-coding RNA (lncRNA) are implicated in cancer where they can control gene regulation. Until now, the expression of lncRNAs during NEtD and their clinical associations were unexplored.
Results: We implemented a next-generation sequence analysis pipeline that can detect transcripts at low expression levels and built a genome-wide catalogue (n = 37,749) of lncRNAs. We applied this pipeline to 927 clinical samples and our high-fidelity NEtD model LTL331 and identified 821 lncRNAs in NEPC. Among these are 122 lncRNAs that robustly distinguish NEPC from prostate adenocarcinoma (AD) patient tumours. The highest expressed lncRNAs within this signature are H19, LINC00617, and SSTR5-AS1. Another 742 are associated with the NEtD process and fall into four distinct patterns of expression (NEtD lncRNA Class I, II, III, and IV) in our PDX model and clinical samples. Each class has significant (z-scores >2) and unique enrichment for transcription factor binding site (TFBS) motifs in their sequences. Enriched TFBS include (1) TP53 and BRN1 in Class I, (2) ELF5, SPIC, and HOXD1 in Class II, (3) SPDEF in Class III, (4) HSF1 and FOXA1 in Class IV, and (5) TWIST1 when merging Class III with IV. Common TFBS in all NEtD lncRNA were also identified and include E2F, REST, PAX5, PAX9, and STAF. Interrogation of the top deregulated candidates (n = 100) in radical prostatectomy adenocarcinoma samples with long-term follow-up (median 18 years) revealed significant clinicopathological associations. Specifically, we identified 25 that are associated with rapid metastasis following androgen deprivation therapy (ADT). Two of these lncRNAs (SSTR5-AS1 and LINC00514) stratified patients undergoing ADT based on patient outcome.
Discussion: To date, a comprehensive characterization of the dynamic landscape of lncRNAs during the NEtD process has not been performed. A temporal analysis of the PDX-based NEtD model has for the first time provided this dynamic landscape. TFBS analysis identified NEPC-related TF motifs present within the NEtD lncRNA sequences, suggesting functional roles for these lncRNAs in NEPC pathogenesis. Furthermore, select NEtD lncRNAs appear to be associated with metastasis and patients receiving ADT. Treatment-related metastasis is a clinical consequence of NEPC tumours. Top candidate lncRNAs FENDRR, H19, LINC00514, LINC00617, and SSTR5-AS1 identified in this study are implicated in the development of NEPC. We present here for the first time a genome-wide catalogue of NEtD lncRNAs that characterize the transdifferentiation process and a robust NEPC lncRNA patient expression signature. To accomplish this, we carried out the largest integrative study that applied a PDX NEtD model to clinical samples. These NEtD and NEPC lncRNAs are strong candidates for clinical biomarkers and therapeutic targets and warrant further investigation.

Heat shock factor 1 (HSF1) generally exhibits its properties under stress conditions. In tumors, HSF1 has a pleiotropic feature in regulating growth, survival, and aggressiveness of cancer cells. In this study, we found HSF1 was increased in colorectal cancer (CRC) and had a positive correlation with shorter disease-free survival (DFS). Knockdown of HSF1 in CRC cells attenuated their growth while inhibiting mTOR activation and glutamine metabolism. HSF1 inhibited the expression of microRNA137 (MIR137), which targeted GLS1 (glutaminase 1), thus stimulating GLS1 protein expression to promote glutaminolysis and mTOR activation. HSF1 bound DNA methyltransferase DNMT3a and recruited it to the promoter of lncRNA MIR137 host gene (MIR137HG), suppressing the generation of primary MIR137. The chemical inhibitor of HSF1 also reduced cell growth, increased apoptosis, and impaired glutamine metabolism in vitro. Moreover, both chemical inhibition and genetic knockout of HSF1 succeeded in increasing MIR137 expression, reducing GLS1 expression, and alleviating colorectal tumorigenesis in azoxymethane (AOM)/dextran sulfate sodium (DSS) mice. In conclusion, HSF1 expression was increased and associated with poor prognosis in CRC. By recruiting DNMT3a to suppress the expression of MIR137 that targets GLS1 mRNA, HSF1 stimulated GLS1-dependent mTOR activation to promote colorectal carcinogenesis. Therefore, targeting HSF1 to attenuate glutaminolysis and mTOR activation could be a promising approach for CRC treatment.

Genetic linkage analysis previously suggested that GKAP, a scaffold protein of the N-methyl-D-aspartate receptor (NMDAR), was a potential modifier of invasion in a mouse model of pancreatic neuroendocrine tumor (PanNET). Here, we establish that GKAP governs invasive growth and treatment response to NMDAR inhibitors of PanNET via its pivotal role in regulating NMDAR pathway activity. Combining genetic knockdown of GKAP and pharmacological inhibition of NMDAR, we implicate as downstream effectors FMRP and HSF1, which along with GKAP demonstrably support invasiveness of PanNET and pancreatic ductal adenocarcinoma cancer cells. Furthermore, we distilled genome-wide expression profiles orchestrated by the NMDAR-GKAP signaling axis, identifying transcriptome signatures in tumors with low/inhibited NMDAR activity that significantly associate with favorable patient prognosis in several cancer types.

The transcription factor, heat shock factor 1 (HSF1), influences the expression of heat shock proteins as well as other activities like the induction of tumor suppressor genes, signal transduction pathway, and glucose metabolism. We hypothesized that single nucleotide polymorphisms (SNPs) in HSF1 gene might affect its expression or function which might have an influence on the development of breast cancer. The study group included 242 individuals (146 breast cancer patients and 96 healthy controls). From the cancer patients, genomic DNA was extracted from 96 blood samples and 50 Formalin-Fixed Paraffin Embedded (FFPE) tissues, while from the controls DNA were extracted from blood only. Genotype was carried out for four SNPs in the HSF1 gene (rs78202224, rs35253356, rs4977219 and rs34404564) using Taqman genotyping assay method. The HSF1 expression was investigated using immunohistochemistry on FFPE tissues (cancer tissue and adjacent normal tissue). The SNP rs78202224 (G>T) was significantly associated with increased risk of breast cancer. The combined TT + GT genotype (OR: 6.91; p: 0.035) and the T allele showed high risk (OR: 5.81; p:0.0085) for breast cancer development. The SNP rs34404564 (A>G) had a protective effect against the development of breast cancer. The genotype AG (OR: 0.41; p = 0.0059) and GG+AG (OR: 0.52; p: 0.026) occurred at a significantly lower frequency in the breast cancer patients compared to the frequency in healthy controls. No significant relationship was identified between either rs35253356 (A>G) or rs4977219 (A>C) and breast cancer in Saudi. The HSF1 protein expression was higher in all invasive and in situ breast carcinoma compared to the normal tissue. A stronger positive staining for HSF1 was found in the nucleus compared to the cytoplasm. Our results show that HSF1 gene expression is elevated in breast cancer tissue and two of the studied SNPs correlate significantly with cancer development.

Organized networks of heat shock proteins, which possess molecular chaperone activity, protect cells from abrupt environmental changes. Additionally, molecular chaperones are essential during stress-free periods, where they moderate housekeeping functions. During tumorigenesis, these chaperone networks are extensively remodeled in such a way that they are advantageous to the transforming cell. Molecular chaperones by buffering critical elements of signaling pathways empower tumor evolution leading to chemoresistance of cancer cells. Controversially, the same molecular chaperones, which are indispensable for p53 in reaching its tumor suppressor potential, are beneficial in adopting an oncogenic gain of function phenotype when TP53 is mutated. On the molecular level, heat shock proteins by unwinding the mutant p53 protein expose aggregation-prone sites leading to the sequestration of other tumor suppressor proteins causing inhibition of apoptosis and chemoresistance. Therefore, within this review therapeutic approaches combining classical immuno- and/or chemotherapy with specific inhibition of selected molecular chaperones shall be discussed.

Arg Kinase-binding protein 2 (ArgBP2) is considered to be a scaffold protein that coordinates multiple signaling pathways converging on cell adhesion and actin cytoskeletal organization. It also plays an important role in blocking cancer metastasis as a potential tumor suppressor. However, its regulation mechanisms in tumor migration, especially in gastric cancer, are not fully understood. Here, we identified an ArgBP2 enhancer and showed that heat shock factor 1 (HSF1) directly interacted with microrchidia CW-type zinc finger 2 (MORC2) and bound to the enhancer of ArgBP2. HSF1 was found to promote proliferation, migration and invasion of gastric cancer cells. HSF1 or/and MORC2 increased recruitment of the polycomb repressive complex 2 (PRC2), particularly enhancer of zeste homolog 2 (EZH2), to the ArgBP2 enhancer and catalyzed tri-methylation of lysine 27 on histone H3 (H3K27me3), leading to transcriptional repression of ArgBP2. In addition, HSF1 and MORC2-induced migration and invasion in gastric cancer cells was dependent on ArgBP2 or EZH2. Clinical data exhibited a negative correlation of ArgBP2 with MORC2, HSF1, and EZH2. Our results thus contribute to the knowledge of the regulatory mechanism of HSF1 in down-regulating ArgBP2, providing new insight into the HSF1&MORC2-PRC2-ArgBP2 signaling pathway and a better understanding of their functions in gastric cancer cells.

In a previous study, we found that DNAJB8, a heat shock protein (HSP) 40 family member is expressed in kidney cancer stem-like cells (CSC)/cancer-initiating cells (CIC) and that it has a role in the maintenance of kidney CSC/CIC. Heat shock factor (HSF) 1 is a key transcription factor for responses to stress including heat shock, and it induces HSP family expression through activation by phosphorylation. In the present study, we therefore examined whether heat shock (HS) induces CSC/CIC. We treated the human kidney cancer cell line ACHN with HS, and found that HS increased side population (SP) cells. Western blot analysis and qRT-PCR showed that HS increased the expression of DNAJB8 and SOX2. Gene knockdown experiments using siRNAs showed that the increase in SOX2 expression and SP cell ratio depends on DNAJB8 and that the increase in DNAJB8 and SOX2 depend on HSF1. Furthermore, treatment with a mammalian target of rapamycin (mTOR) inhibitor, temsirolimus, decreased the expression of DNAJB8 and SOX2 and the ratio of SP cells. Taken together, the results indicate that heat shock induces DNAJB8 by activation of HSF1 and induces cancer stem-like cells.

BACKGROUND: The heat shock transcription factor, HSF1, is the main regulator of the proteotoxic stress response that orchestrates the adaptation of cells to stress conditions such as elevated temperature, oxidative stress, and proteotoxic stress. As such, HSF1 regulates a large number of stress response-related genes, primarily those encoding heat shock proteins (HSPs). HSPs are molecular chaperones involved in the acquisition of native protein conformations and the prevention of protein degradation, and they also contribute to the removal of denatured proteins via the proteasome. Representative members of the HSP family are HSP70 and HSP90. The stress response is a highly conserved mechanism across all eukaryotes, and HSF1 has been linked to a number of physiological processes (ribosomal biogenesis, translation, transcription, cell cycle, and metabolism) and pathological disorders (neurodegenerative disorders such as Parkinson´s and Alzheimer´s diseases). HSF1 activation is also prominent in different types of cancer (prostate, breast, colorectal carcinoma etc.) where it correlates with tumor aggressiveness and poor prognosis. HSF1 is therefore considered a diagnostic and prognostic marker and is currently being targeted to develop new cancer therapies. Several inhibitors of HSF1 have already been synthesized, but their molecular mechanism (s) of action, specificity those of HSF1, nontoxicity in healthy tissues, and their efficacy in targeting tumor cells remain to be elucidated.
PURPOSE: This review summarizes known mechanisms of HSF1 regulation and activation, the role of HSF1 during malignant transformation, and the potential of designing small molecule HSF1 inhibitors for cancer therapy. Key words: HSF1 transcription factor - molecular chaperones - cellular stress - tumor transformation - cancer This work was supported by the project MEYS - NPS I - LO1413. The authors declare they have no potential conflicts of interest concerning drugs, products, or services used in the study. The Editorial Board declares that the manuscript met the ICMJE recommendation for biomedical papers. Accepted: 10. 8. 2018.

BACKGROUND AND AIM: Heat shock factor 1 (HSF1), a master regulator of heat shock response, has been shown to play a multifaceted role in cancer progression. However, the clinical significance and biological effect of HSF1 expression in intrahepatic cholangiocarcinoma (IHCC) remain unknown.
METHODS: Forty-nine patients with IHCC who underwent hepatic resection were enrolled in this study. HSF1 expression in tumor tissue was determined by immunohistochemistry, and patients were divided into two groups, those with high (n = 20) and low (n = 29) HSF1 expression. Clinicopathological factors including prognosis were compared in these two groups.
RESULTS: HSF1 expression was significantly higher in tumors than in normal tissue. The overall survival rate was significantly lower in patients with high than low HSF1. Multivariate analysis showed that high HSF1 expression was a factor independently prognostic of patient survival.
CONCLUSION: High HSF1 expression in tumor tissues may be a prognostic biomarker in patients with IHCC.

BACKGROUND: HSF1 (heat shock factor 1) is a transcription factor that is found to facilitate malignant cancer development and proliferation. In cancer cells, HSF1 mediates a set of genes distinct from heat shock that contributes to malignancy. This set of genes is known as the HSF1 Cancer Signature genes or simply HSF1-CanSig genes. HSF1-CanSig genes function and operate differently than typical cancer-causing genes, yet it is involved in fundamental oncogenic processes.
RESULTS: By utilizing expression data from 9241 cancer patients, we identified that human chromosome 8q21-24 is a location hotspot for the most frequently overexpressed HSF1-CanSig genes. Intriguingly, the strength of the HSF1 cancer program correlates with the number of overexpressed HSF1-CanSig genes in 8q, illuminating the essential role of HSF1 in mediating gene expression in different cancers. Chromosome 8q21-24 is found under selective pressure in preserving gene order as it exhibits strong synteny among human, mouse, rat, and bovine, although the biological significance remains unknown. Statistical modeling, hierarchical clustering, and gene ontology-based pathway analyses indicate crosstalk between HSF1-mediated responses and pre-mRNA 3' processing in cancers.
CONCLUSIONS: Our results confirm the unique role of chromosome 8q mediated by the master regulator HSF1 in cancer cases. Additionally, this study highlights the connection between cellular processes triggered by HSF1 and pre-mRNA 3' processing in cancers.

Poly(ADP-ribose) polymerase 1 (PARP1) is involved in DNA repair, chromatin structure, and transcription. However, the mechanisms that regulate PARP1 distribution on DNA are poorly understood. Here, we show that heat shock transcription factor 1 (HSF1) recruits PARP1 through the scaffold protein PARP13. In response to DNA damage, activated and auto-poly-ADP-ribosylated PARP1 dissociates from HSF1-PARP13, and redistributes to DNA lesions and DNA damage-inducible gene loci. Histone deacetylase 1 maintains PARP1 in the ternary complex by inactivating PARP1 through deacetylation. Blocking ternary complex formation impairs redistribution of PARP1 during DNA damage, which reduces gene expression and DNA repair. Furthermore, ternary complex formation and PARP1 redistribution protect cells from DNA damage by promoting DNA repair, and support growth of BRCA1-null mammary tumors, which are sensitive to PARP inhibitors. Our findings identify HSF1 as a regulator of genome integrity and define this function as a guarding mechanism for a specific type of mammary tumorigenesis.

Past studies have shown that mutant KRAS colon cancer cells are susceptible to apoptosis induced by the HSP90 inhibitor AUY922. Nevertheless, intrinsic and acquired resistance remains an obstacle for the potential application of the inhibitor in the treatment of the disease. Here we report that Mcl-1 is important for survival of colon cancer cells in the presence of AUY922. Mcl-1 was upregulated in mutant KRAS colon cancer cells selected for resistance to AUY922-induced apoptosis. This was due to its increased stability mediated by Bcl-2-associated athanogene domain 3 (BAG3), which was also increased in resistant colon cancer cells by heat shock factor 1 (HSF1) as a result of chronic endoplasmic reticulum (ER) stress. Functional investigations demonstrated that inhibition of Mcl-1, BAG3, or HSF1 triggered apoptosis in resistant colon cancer cells, and rendered AUY922-naïve colon cancer cells more sensitive to the inhibitor. Together, these results identify that the HSF1-BAG3-Mcl-1 signal axis is critical for protection of mutant KRAS colon cancer cells from AUY922-induced apoptosis, with potential implications for targeting HSF1/BAG3/Mcl-1 to improve the efficacy of AUY922 in the treatment of colon cancer.

Overexpression of Rictor has been demonstrated to result in increased mechanistic target of rapamycin C2 (mTORC2) nucleation and activity leading to tumor growth and increased invasive characteristics in glioblastoma multiforme (GBM). However, the mechanisms regulating Rictor expression in these tumors is not clearly understood. In this report, we demonstrate that Rictor is regulated at the level of mRNA translation via heat-shock transcription factor 1 (HSF1)-induced HuR activity. HuR is shown to directly bind the 3' untranslated region of the Rictor transcript and enhance translational efficiency. Moreover, we demonstrate that mTORC2/AKT signaling activates HSF1 resulting in a feed-forward cascade in which continued mTORC2 activity is able to drive Rictor expression. RNAi-mediated blockade of AKT, HSF1 or HuR is sufficient to downregulate Rictor and inhibit GBM growth and invasive characteristics in vitro and suppress xenograft growth in mice. Modulation of AKT or HSF1 activity via the ectopic expression of mutant alleles support the ability of AKT to activate HSF1 and demonstrate continued HSF1/HuR/Rictor signaling in the context of AKT knockdown. We further show that constitutive overexpression of HuR is able to maintain Rictor expression under conditions of AKT or HSF1 loss. The expression of these components is also examined in patient GBM samples and correlative associations between the relative expression of these factors support the presence of these signaling relationships in GBM. These data support a role for a feed-forward loop mechanism by which mTORC2 activity stimulates Rictor translational efficiency via an AKT/HSF1/HuR signaling cascade resulting in enhanced mTORC2 activity in these tumors.

Considerable evidences have shown that both heat shock transcription factor 1 (HSF1) and autophagy can attenuate the sensitivity of hepatocellular carcinoma (HCC) cells to chemotherapeutic reagents. However, it is still little known whether HSF1 is associated with autophagy in regulating the chemosensitivity of HCC cells. In this study, we for the first time demonstrated that HSF1 markedly attenuated the killing effect of epirubicin (EPI) to HCC cells via enhancing the EPI-induced protective autophagy. Mechanistically, HSF1 upregulated autophagy related 4B (ATG4B) in HCC cells, which enhanced the EPI-triggered protective autophagy. Reporter assay showed that HSF1 increased the transcriptional activity of ATG4B gene promoter, and chromatin immunoprecipitation assay verified that HSF1 bound to the site (-1429 to -1417) in ATG4B gene promoter region. The experiments in nude mice showed that knockdown of HSF1 or ATG4B strengthened the anti-HCC effect of EPI in vivo. Collectively, these results revealed that HSF1 elevates ATG4B via promoting its transcription, which alleviates the sensitivity of EPI in HCC cells through enhancing protective autophagy, suggesting that the "HSF1/ATG4B/protective autophagy" pathway may be a novel target for developing sensitizing strategy to HCC chemotherapy.

Autophagy plays a critical role in the maintenance of cellular homeostasis by degrading proteins, lipids and organelles. Autophagy is activated in response to stress, but its regulation in the context of other stress response pathways, such as those mediated by heat shock factor 1 (HSF1) and nuclear factor-erythroid 2 p45-related factor 2 (NRF2), is not well understood. We found that the Michael acceptor bis(2-hydoxybenzylidene)acetone (HBB2), a dual activator of NRF2 and HSF1, protects against the development of UV irradiation-mediated cutaneous squamous cell carcinoma in mice. We further show that HBB2 is an inducer of autophagy. In cells, HBB2 increases the levels of the autophagy-cargo protein p62/sequestosome 1, and the lipidated form of microtubule-associated protein light chain 3 isoform B. Activation of autophagy by HBB2 is impaired in NRF2-deficient cells, which have reduced autophagic flux and low basal and induced levels of p62. Conversely, HSF1-deficient cells have increased autophagic flux under both basal as well as HBB2-induced conditions, accompanied by increased p62 levels. Our findings suggest that NRF2 and HSF1 have opposing roles during autophagy, and illustrate the existence of tight mechanistic links between the cellular stress responses.

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Piwi-interacting RNAs (piRNAs), a novel class of small non-coding RNAs, were first discovered in germline cells and are thought to silence transposons in spermatogenesis. Recently, piRNAs have also been identified in somatic tissues, and aberrant expression of piRNAs in tumor tissues may be implicated in carcinogenesis. However, the function of piR-823 in colorectal cancer (CRC) remains unclear. Here, we first found that piR-823 was significantly upregulated in CRC tissues compared with its expression in the adjacent tissues. Inhibition of piR-823 suppressed cell proliferation, arrested the cell cycle in the G1 phase and induced cell apoptosis in CRC cell lines HCT116 and DLD-1, whereas overexpression of piR-823 promoted cell proliferation in normal colonic epithelial cell line FHC. Interestingly, Inhibition of piR-823 repressed the expression of heat shock protein (HSP) 27, 60, 70. Furthermore, elevated HSPs expression partially abolished the effect of piR-823 on cell proliferation and apoptosis. In addition, we further demonstrated that piR-823 increased the transcriptional activity of HSF1, the common transcription factor of HSPs, by binding to HSF1 and promoting its phosphorylation at Ser326. Our study reveals that piR-823 plays a tumor-promoting role by upregulating phosphorylation and transcriptional activity of HSF1 and suggests piR-823 as a potential therapeutic target for CRC.

The process of lung carcinogenesis is still not well understood and involves different levels of regulation of several genes. The search for molecular biomarkers, which can be applicable to clinical practice, has been the focus of various studies. XIAP-associated factor 1 (XAF1) was previously shown to be downregulated in many types of tumors, including squamous cell lung cancer. XAF1 is a pro-apoptotic protein and its restoration was found to sensitize cancer cells to apoptotic stimuli; however, the precise mechanism involved in the downregulation of XAF1 in tumors is unknown and promoter hypermethylation or heat-shock transcription factor 1 (HSF1) may be involved. Therefore, the aim of the present study was to evaluate the expression of XAF1 in tumors and adjacent non-tumor specimens from non-small cell lung cancer (NSCLC) patients, and its potential association with various factors including clinicopathological characteristics and other genes involved in NSCLC. Our results indicated that XAF1 expression was markedly altered in NSCLC tumor samples when compared to that found in normal lung tissues. Predominantly, XAF1 was downregulated in the tumors, except in never-smoker patients. In addition, XAF1 may also be important in the whole cell stress mechanism where the p53 status is crucial.

Late diagnosis and lack of specific therapeutic targets contribute to the low survival rate of patients with epithelial ovarian cancer (EOC), the most lethal gynecologic malignancy. Therefore, the screening of diagnostic markers and the identification of therapeutic targets are urgently required. Heat shock factor 1 (HSF1) has been demonstrated to be overexpressed in certain malignancies and to be involved in tumor initiation, development, transformation and metastasis. It is believed that HSF1 is a promising candidate for antitumor therapy. However, its expression pattern and function in ovarian cancer are far from being fully elucidated. Therefore, we examined the HSF1 expression in human EOC tissues, and evaluated its carcinogenesis-promoting activity in a xenograft tumor model. Examination of HSF1 expression in human EOC tissues was performed by immunohistochemical assay using ovarian tissue blots. Specific short hairpin RNA (shRNA) against HSF1 was employed to knockdown HSF1 in SKOV3 cells. Cell proliferative activity was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay; cell cycle distribution and apoptosis were determined by flow cytometric analysis. In normal ovarian tissues, HSF1 was barely detected, whereas, high expression of HSF1 was found in malignant EOC tissues, including serous, mucinous, endometrioid, and clear cell EOC tissues. Suppressed proliferative activity and intensified apoptosis were observed in HSF1-knockdown SKOV3 cells. In nude mouse xenografts, downregulation of HSF1 was found to cause reduced carinogenesis, indicating the antitumor effect induced by modulation of HSF1 against EOC. Our findings suggest that HSF1 may be considered as a potential candidate diagnostic marker of human EOC, and that modulation of HSF1 could be a promising therapeutic strategy against human EOC.

BACKGROUND: As a relatively conservative transcriptional regulator in biological evolution, heat shock factor 1 (HSF1) is activated by, and regulates the expression of heat shock proteins (HSPs) in response to a variety of stress conditions. HSF1 also plays a key role in regulating the development of various tumors; however, its role in pancreatic cancer and the specific underlying mechanism are not clear.
METHODS: We first examined HSF1 expression in pancreatic cancer tissues by immunohistochemistry, and then studied its clinical significance. We then constructed HSF1-siRNA to investigate the potential of HSF1 to regulate apoptosis, proliferation and the cell cycle of pancreatic cancer cells and the underlying mechanism both in vitro and in vivo. Protein chip analysis was used subsequently to explore the molecular regulation pathway. Finally, second mitochondria-derived activator of caspase (SMAC)-siRNA was used to validate the signaling pathway.
RESULTS: HSF1 was highly expressed in pancreatic cancer tissues and the level of upregulation was found to be closely related to the degree of pancreatic cancer differentiation and poor prognosis. After HSF1-silencing, we found that pancreatic cancer cell proliferation decreased both in vitro and in vivo and the apoptotic cell ratio increased, while the mitochondrial membrane potential decreased, and the cells were arrested at the G0/G1 phase. In terms of the molecular mechanism, we confirmed that HSF1 regulated SMAC to inhibit mitochondrial apoptosis in pancreatic cancer cells, and to promote the occurrence of pancreatic tumors. SMAC silencing reversed the effects of HSF1 silencing.
CONCLUSION: Our study provides evidence that HSF1 functions as a novel oncogene in pancreatic tumors and is implicated as a target for the diagnosis and treatment of pancreatic cancer.

BACKGROUND The purpose of this study was to research the effects of hyperthermia on osteosarcoma (OS) by integrating the Chromatin Immunoprecipitation with the generation sequencing (ChIP-Seq) and TargetScan analysis of heat shock transcription factor 1 (HSF1). MATERIAL AND METHODS The HSF1 ChIP-seq dataset of GSE60984 was downloaded from the Gene Expressed Omnibus (GEO) database. The HSF1-binding sites were screened by MACS2 in OS cells after 10 and 20 min of hyperthermia, and they were annotated using the ChIPseeker package. The overlapped genes were selected out when HSF1-binding sites were located in the promoter region. The Database for Annotation, Visualization, and Integrated Discovery (DAVID) was used to perform Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis of the overlaps. The miRNA-gene pairs of the overlaps were screened out via TargetScan, and the miRNA-gene-regulated network was constructed by Cytoscape software. RESULTS 1880 and 1283 genes of promoter regions were obtained in the osteosarcoma cells after 10 and 20 min of hyperthermia, respectively, and 889 of them were overlapped. The overlapped genes were enriched in 122 GO terms and 3 KEGG pathways. There were 13 657 pairs involved in the miRNA-gene regulated network of the overlaps. CONCLUSIONS Some biomarkers were identified for OS treated with hyperthermia. Moreover, some GO terms (regulation of programmed cell death and regulation of cell death) and pathways (p53 signaling pathway, methane metabolism, and viral myocarditis) might be involved.

BACKGROUND: Cancer-associated fibroblasts (CAFs) communicate with cancer cells to play important roles in tumor progression. However, CAFs have heterogeneous phenotypes and functions. To understand how much of this heterogeneity relates to different biological responses, a more efficient method of generating single-cell-derived CAF clones is required.
METHOD: We transduced two primary CAF cultures (CAFs-608 and CAFs-621) from lung adenocarcinoma with human telomerase reverse transcriptase (hTERT), mutant forms of cyclin dependent kinase 4 (CDK4R24C) independently and in combination (hTERT/CDK4R24C). After live imaging of each sorted-single cell, we evaluated the numbers of successfully established clones from CAFs-hTERT, CAFs-CDK4R24C, and CAFs-hTERT/CDK4R24C. Furthermore, we examined the expression levels of genes associated with tumor promoting pathways in established clones by qRT-PCR.
RESULTS: Overexpression of hTERT and CDK4R24C efficiently extended the lifespan of both CAFs-608 and CAFs-621. The number of established CAF clones was highest for CAFs-hTERT/CDK4R24C, with 57 and 62 clones established from CAFs-608 and CAFs-621, respectively. Conversely, 16 and 11 CAFs-hTERT clones were derived from CAFs-608 and CAFs-621, respectively and 10 and 8 CAFs-CDK4R24C clones were from CAFs-608 and CAFs-621, respectively. TGF-b, ATCA2, and HSF1 mRNA levels differed in individual clones established from CAFs-hTERT/CDK4R24C. The expression levels of ATCA2 and HSF1 were much higher in one clone than in the other established clones and the parental CAFs.
CONCLUSION: Our results show that combined exogenous expression of hTERT and mutant CDK4 is an effective method to generate single-cell-derived CAF clones. This provides an innovative and suitable approach to investigate the heterogeneous function and phenotype of CAFs.

BACKGROUND: Docetaxel based therapy is one of the first line chemotherapeutic agents for the treatment of metastatic castrate-resistant prostate cancer. However, one of the major obstacles in the treatment of these patients is docetaxel-resistance. Defining the mechanisms of resistance so as to inform subsequent treatment options and combinations represents a challenge for clinicians and scientists. Previous work by our group has shown complex changes in pro and anti-apoptotic proteins in the development of resistance to docetaxel. Targeting these changes individually does not significantly impact on the resistant phenotype but understanding the central signalling pathways and transcription factors (TFs) which control these could represent a more appropriate therapeutic targeting approach.
METHODS: Using a number of docetaxel-resistant sublines of PC-3 cells, we have undertaken a transcriptomic analysis by expression microarray using the Affymetrix Human Gene 1.0 ST Array and in conjunction with bioinformatic analyses undertook to predict dysregulated TFs in docetaxel resistant prostate cancer. The clinical significance of this prediction was ascertained by performing immunohistochemical (IHC) analysis of an identified TF (SRF) in the metastatic sites from men who died of advanced CRPC. Investigation of the functional role of SRF was examined by manipulating SRF using SiRNA in a docetaxel-resistant PC-3 cell line model.
RESULTS: The transcription factors identified include serum response factor (SRF), nuclear factor kappa-B (NFκB), heat shock factor protein 1 (HSF1), testicular receptor 2 & 4 (TR2 &4), vitamin-D and retinoid x receptor (VDR-RXR) and oestrogen-receptor 1 (ESR1), which are predicted to be responsible for the differential gene expression observed in docetaxel-resistance. IHC analysis to quantify nuclear expression of the identified TF SRF correlates with both survival from date of bone metastasis (p = 0.003), survival from androgen independence (p = 0.00002), and overall survival from prostate cancer (p = 0.0044). Functional knockdown of SRF by siRNA demonstrated a reversal of apoptotic resistance to docetaxel treatment in the docetaxel-resistant PC-3 cell line model.
CONCLUSIONS: Our results suggest that SRF could aid in treatment stratification of prostate cancer, and may also represent a therapeutic target in the treatment of men afflicted with advanced prostate cancer.