Hsp90 Inhibitor Research Articles

Identification of circRNA-miRNA-mRNA Network Regulated by Hsp90 in Human Melanoma A375 Cells.

Melanoma is the deadliest form of skin cancer. Heat shock protein 90 (Hsp90) is highly expressed in human melanoma. Hsp90 inhibitors can suppress the growth of human melanoma A375 cells; however, the underlying mechanism remains unclear. A375 cells were treated with SNX-2112, an Hsp90 inhibitor, for 48 h, and wholetranscriptome sequencing was performed. A total of 2,528 differentially expressed genes were identified, including 895 upregulated and 1,633 downregulated genes. Pathway enrichment analyses of differentially expressed mRNAs identified the extracellular matrix (ECM)-receptor interaction pathway as the most significantly enriched pathway. The ECM receptor family mainly comprises integrins (ITGs) and collagens (COLs), wherein ITGs function as the major cell receptors for COLs. 19 upregulated miRNAs were found to interact with 6 downregulated ITG genes and 8 upregulated miRNAs were found to interact with 3 downregulated COL genes. 9 differentially expressed circRNAs in SNX-2112- treated A375 cells were identified as targets of the ITG- and COL-related miRNAs. Based on the differentially expressed circRNAs, miRNAs, and mRNAs, ITGs- and COL-based circRNAmiRNA- mRNA regulatory networks were mapped, revealing a novel regulatory mechanism of Hsp90-regulated melanoma. Targeting the ITG-COL network is a promising approach to the treatment of melanoma.

Abstract A032: Low non-immune stromal cell levels and high hypoxic tumor microenvironments are associated with pathologic complete response in the neoadjuvant I-SPY2 TRIAL

Abstract Background: Non-immune components of the tumor microenvironment (TME) play important roles in cancer. We explore two important components of the TME: non-immune stromal cell populations including fibroblasts, adipocytes, and endothelial cells; and hypoxic conditions. We leverage published gene expression-based biomarkers of stromal cell types and hypoxia, and molecular and clinical data from the I-SPY2 TRIAL (PMID: 35623341) – an adaptive neoadjuvant trial for locally advanced breast cancers. We assess the contribution of stromal cell populations and oxygen-poor environments at pre-treatment in shaping the landscape of immune enrichment and therapeutic response in breast cancers. Methods: We curated 14 stromal and 11 hypoxia gene sets, in addition to 35 immune gene sets from literature. Signatures scores of stromal, hypoxic, and immune TME were calculated from gene expression profiles of pre-treatment tumor samples from I-SPY2 patients (n=987) in the first 9 treatment arms of the trial plus control arms. Correlation of stromal and hypoxia signatures with immune signatures were assessed, and association of TME features with HER2/HR receptor status, I-SPY response-predictive subtype (RPS), and pathological complete response (pCR) were evaluated using non-parametric tests. All p-values were adjusted for multiple testing. Significance levels were defined at adj. p<0.05. Results: Both stromal and hypoxia signatures showed significant differential enrichment across HR/HER2 and RPS subtypes, and association with pCR. Several stromal signatures including adipocytes, endothelial cells, mesenchymal stem cells, and overall stromal score had the lowest enrichment in HR-/HER2- breast cancers, and in the RPS HER2-/immune+ subtype. Moreover, most stromal signatures showed anti-correlation with CD8+ and CD4+ T cell enrichment. Stromal signatures including endothelial cells, smooth muscle cells, and overall score were significantly lower in patients who achieved pCR. Two hypoxia gene sets demonstrated highly significant enrichment in HR- versus HR+ samples regardless of HER2 status. All hypoxia signatures varied significantly across RPS subtypes, with the highest scores in HER2-/Immune-/DRD+, especially relative to HER2-/Immune-/DRD- and HER2+/BP-Luminal subtypes. Hypoxia signatures strongly linked to hypoxia inducible factor (HIF) and angiogenesis via VEGF were positively associated with pCR. These hypoxia signatures showed treatment-specific associations with pCR, specifically in agents targeting mechanisms with known interactions with hypoxia-induced biology: trebananib (angiogenesis inhibitor), ganetespib (HSP90 inhibitor) and veliparib/carboplatin (DNA damage repair inhibitor). Conclusions: Hypoxia and stromal cell gene signatures show breast cancer subtype-specific biology. Relative absence of non-immune stromal cell types is associated with higher immune infiltration and higher pCR rates, while specific hypoxia pathways were associated with response to therapeutic agents targeting hypoxia-related pathways. Citation Format: Kailey Dubinsky, Elene Tsopurashvili, Denise M. Wolf, Zheyun Xu, Silver Al Khafaji Alkhafaji, Anna van Montfort, Christina Yau, Diane Heditsian, Allison Fiscalini, Laura J. Esserman, Laura van ‘t Veer, Rosalyn W. Sayaman. Low non-immune stromal cell levels and high hypoxic tumor microenvironments are associated with pathologic complete response in the neoadjuvant I-SPY2 TRIAL [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Breast Cancer Research; 2023 Oct 19-22; San Diego, California. Philadelphia (PA): AACR; Cancer Res 2024;84(3 Suppl_1):Abstract nr A032.

First-in-Class Dual EZH2-HSP90 Inhibitor Eliciting Striking Antiglioblastoma Activity In Vitro and In Vivo.

Structural analysis of tazemetostat, an FDA-approved EZH2 inhibitor, led us to pinpoint a suitable site for appendage with a pharmacophoric fragment of second-generation HSP90 inhibitors. Resultantly, a magnificent dual EZH2/HSP90 inhibitor was pinpointed that exerted striking cell growth inhibitory efficacy against TMZ-resistant Glioblastoma (GBM) cell lines. Exhaustive explorations of chemical probe 7 led to several revelations such as (i) compound 7 increased apoptosis/necrosis-related gene expression, whereas decreased M phase/kinetochore/spindle-related gene expression as well as CENPs protein expression in Pt3R cells; (ii) dual inhibitor 7 induced cell cycle arrest at the M phase; (iii) compound 7 suppressed reactive oxygen species (ROS) catabolism pathway, causing the death of TMZ-resistant GBM cells; and (iv) compound 7 elicited substantial in vivo anti-GBM efficacy in experimental mice xenografted with TMZ-resistant Pt3R cells. Collectively, the study results confirm the potential of dual EZH2-HSP90 inhibitor 7 as a tractable anti-GBM agent.

Heat shock protein 90: biological functions, diseases, and therapeutic targets.

Heat shock protein 90 (Hsp90) is a predominant member among Heat shock proteins (HSPs), playing a central role in cellular protection and maintenance by aiding in the folding, stabilization, and modification of diverse protein substrates. It collaborates with various co-chaperones to manage ATPase-driven conformational changes in its dimer during client protein processing. Hsp90 is critical in cellular function, supporting the proper operation of numerous proteins, many of which are linked to diseases such as cancer, Alzheimer's, neurodegenerative conditions, and infectious diseases. Recognizing the significance of these client proteins across diverse diseases, there is a growing interest in targeting Hsp90 and its co-chaperones for potential therapeutic strategies. This review described biological background of HSPs and the structural characteristics of HSP90. Additionally, it discusses the regulatory role of heat shock factor-1 (HSF-1) in modulating HSP90 and sheds light on the dynamic chaperone cycle of HSP90. Furthermore, the review discusses the specific contributions of HSP90 in various disease contexts, especially in cancer. It also summarizes HSP90 inhibitors for cancer treatment, offering a thoughtful analysis of their strengths and limitations. These advancements in research expand our understanding of HSP90 and open up new avenues for considering HSP90 as a promising target for therapeutic intervention in a range of diseases.

Role of heat shock protein 90 in hypoxia-induced angiogenesis and epithelial-mesenchymal transition for esophageal squamous cancer cells.

395 Background: Hypoxia is known as an important trigger for the development and progression of human cancers. Heat shock proteins (Hsps) may be up-regulated in response to cellular stressors including hypoxia. To date, the functional role of Hsps within hypoxic tumor microenvironment for esophageal squamous cell cancer (ESCC) remains poorly defined. Methods: CoCl2 was used to induce hypoxia that mimics a hypoxic tumor microenvironment in cultured ESCC cells. Successful induction of hypoxia was confirmed by 2’,7’ –dichlorofluorescein diacetate (DCFDA) assay by detection of cellular reactive oxygen species (ROS). 7-Dimethylaminoethylamino-17-demethoxygeldanamycin (17-DMAG), a selective Hsp90 inhibitor, was used to treat 2 ESCC cell lines, KYSE-170 and -510 cells pretreated with or without CoCl2, an agent to induce a hypoxic tumor microenvironment. Cytotoxicity (MTT) and migration assays were conducted in KYSE-17 and -510 ESCC cells in response to different concentrations of CoCl2, followed by protein expression of Hsp 90, vascular endothelial growth factor (VEGF), hypoxia-inducible factor-1a (HIF-1a), mTOR as well as markers related epithelial-mesenchymal transition (EMT) such as snail or E-cadherin, by immunoblot or ELISA. In parallel, cell proliferation and migration assays of ESCC cells were analyzed. Results: CoCl2 induced hypoxia was supported by an induction of reactive oxygen species (ROS). CoCl2 (200 mM) significantly suppressed cell viability and proliferation with a concomitant up-regulation of VEGF and HIF-1a in a dose-dependent fashion. In contrast, cell migration was significantly increased in response to CoCl2, while down-regulating E-cadherin with concomitant increase in Snail expression. 17-DMAG decreased expression of VEGF and HIF-1a. In addition, it inhibited cell migration and invasion of ESCC cells were analyzed. Conclusions: Our data have shown that CoCl2 induced hypoxia promotes EMT and angiogenesis, which are inhibited by 17-DMAG, suggesting that hypoxia induced EMT and angiogenesis is Hsp 90 dependent in ESCC.

Inhibition of HSF1 as a Mechanism for Overcoming Hsp90 Treatment Resistance

Hsp90 inhibitors have been attempted as a targeted therapy with poor results. Despite numerous clinical trials, there are currently no FDA approved Hsp90 inhibitors available. It is known that Hsp90 sequesters HSF1 in the cytoplasm to suppress HSF1 activity, an oncogenic transcription factor. We hypothesize that HSF1 activation in response to Hsp90 inhibition is a significant reason that previous Hsp90 inhibitors have failed. Once released, HSF1 enters the nucleus and drives expression of many processes that promote the initiation and progression of tumors. This hypothesis was tested by evaluating the response of cancer cells to Hsp90 inhibition with or without combined inhibition of HSF1, thereby removing HSF1 activity as a consequence of Hsp90 inhibition. We observed synergy between Hsp90 inhibition (17-DMAG) and HSF1 inhibition (KRIBB11) from calculation of combination index in ovarian cancer cells (OVCAR8) and breast cancer cells (BT474). This synergy observed in cell viability assays were further reinforced in spheroid formation and clonogenic growth assays where the combination of these inhibitors had a greater effect than either treatment alone. These results further support the hypothesis that Hsp90 inhibition efficacy is mitigated by increased HSF1 activity and that HSF1 inhibitors synergize with Hsp90 inhibitors to improve their efficacy.

Heat shock protein 90 inhibition attenuates inflammation in models of atopic dermatitis: a novel mechanism of action.

Heat shock protein 90 (HSP90) is an important chaperone supporting the function of many proinflammatory client proteins. Recent studies indicate HSP90 inhibition may be a novel mechanism of action for inflammatory skin diseases; however, this has not been explored in atopic dermatitis (AD). Our study aimed to investigate HSP90 as a novel target to treat AD. Experimental models of AD were used including primary human keratinocytes stimulated with cytokines (TNF/IFNγ or TNF/IL-4) and a mouse model established by MC903 applications. In primary human keratinocytes using RT-qPCR, the HSP90 inhibitor RGRN-305 strongly suppressed the gene expression of Th1- (TNF, IL1B, IL6) and Th2-associated (CCL17, CCL22, TSLP) cytokines and chemokines related to AD. We next demonstrated that topical and oral RGRN-305 robustly suppressed MC903-induced AD-like inflammation in mice by reducing clinical signs of dermatitis (oedema and erythema) and immune cell infiltration into the skin (T cells, neutrophils, mast cells). Interestingly, topical RGRN-305 exhibited similar or slightly inferior efficacy but less weight loss compared with topical dexamethasone. Furthermore, RNA sequencing of skin biopsies revealed that RGRN-305 attenuated MC903-induced transcriptome alterations, suppressing genes implicated in inflammation including AD-associated cytokines (Il1b, Il4, Il6, Il13), which was confirmed by RT-qPCR. Lastly, we discovered using Western blot that RGRN-305 disrupted JAK-STAT signaling by suppressing the activity of STAT3 and STAT6 in primary human keratinocytes, which was consistent with enrichment analyses from the mouse model. HSP90 inhibition by RGRN-305 robustly suppressed inflammation in experimental models mimicking AD, proving that HSP90 inhibition may be a novel mechanism of action in treating AD.

Amyloid aggregates induced by the p53-R280T mutation lead to loss of p53 function in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a malignant tumor that is highly prevalent in Southeast Asia, especially in South China. The pathogenesis of NPC is complex, and genetic alterations of tumor suppressors and proto-oncogenes play important roles in NPC carcinogenesis. p53 is unexpectedly highly expressed in NPC and possesses an uncommon mutation of R280T, which is different from a high frequency of hotspot mutations or low expression in other tumors. However, the mechanism of p53 loss of function and its correlation with R280T in NPC are still unclear. In this study, p53 amyloid aggregates were found to be widespread in NPC and can be mainly induced by the R280T mutation. Aggregated p53-R280T impeded its entry into the nucleus and was unable to initiate the transcription of downstream target genes, resulting in decreased NPC cell cycle arrest and apoptosis. In addition, NPC cells with p53-R280T amyloid aggregates also contributed aggressively to tumor growth in vivo. Transcriptome analysis suggested that p53 amyloid aggregation dysregulated major signaling pathways associated with the cell cycle, proliferation, apoptosis, and unfolded protein response (UPR). Further studies revealed that Hsp90, as a key molecular chaperone in p53 folding, was upregulated in NPC cells with p53-R280T aggregation, and the upregulated Hsp90 facilitated p53 aggregation in turn, forming positive feedback. Therefore, Hsp90 inhibitors could dissociate p53-R280T aggregation and restore the suppressor function of p53 in vitro and in vivo. In conclusion, our study demonstrated that p53-R280T may misfold to form aggregates with the help of Hsp90, resulting in the inability of sequestered p53 to initiate the transcription of downstream target genes. These results revealed a new mechanism for the loss of p53 function in NPC and provided novel mechanistic insight into NPC pathogenesis.

Hsp Inhibitor is Affective Against Adenocarcinomic Human Alveolar Basal Epithelial Cells Through Modulating ERK/MAPK Signaling Pathway.

The extracellular signal-regulated kinase (ERK) - mitogen-activated protein kinase (MAPK) pathway regulates cell proliferation, differentiation, and apoptosis. Heat Shock Protein 90 (HSP90) is required to activate proto-oncogenic protein kinases and promotes tumor growth through anti-apoptotic effects on A549-non-small cell lung cancer (NSCLC). Therefore, deregulation of the ERK-MAPK pathway and abnormal expression of HSP90 are reasonably frequent events in NSCLC. In this study, novel perimidine-pyrazole compounds employed to block ERK-MAPK deregulation through inhibiting HSP dependent cancer cell survival mechanisms. A set of perimidine-pyrazole derivatives effects was monitored on NSCLC cell line. Array experiments performed to understand the effect of the compounds on signaling pathways and results were analyzed by gene enrichment analysis. Further, senescence and apoptosis experiments were performed to support the enrichment results along with in silico methods to determine perimidine-pyrazole/HSP interactions. Treatment of NSCLC cells with perimidine-pyrazole derivatives displayed cancer-inhibitory, pro-senescent and pro-apoptotic effects on NSCLC cells through ERK/MAPK pathway and these compounds are promising templates for designing anticancer drugs.

Design, synthesis, and biological assessment of prodrugs for nitroreductase-based HSP90 inhibitor BIIB021: exploring their potential as anticancer agents

Design, synthesis, and biological assessment of prodrugs for nitroreductase-based HSP90 inhibitor BIIB021: exploring their potential as anticancer agents

The HSP90 inhibitor HVH-2930 exhibits potent efficacy against trastuzumab-resistant HER2-positive breast cancer.

Rationale: Resistance to targeted therapies like trastuzumab remains a critical challenge for HER2-positive breast cancer patients. Despite the progress of several N-terminal HSP90 inhibitors in clinical trials, none have achieved approval for clinical use, primarily due to issues such as induction of the heat shock response (HSR), off-target effects, and unfavorable toxicity profiles. We sought to examine the effects of HVH-2930, a novel C-terminal HSP90 inhibitor, in overcoming trastuzumab resistance. Methods: The effect of HVH-2930 on trastuzumab-sensitive and -resistant cell lines in vitro was evaluated in terms of cell viability, expression of HSP90 client proteins, and impact on cancer stem cells. An in vivo model with trastuzumab-resistant JIMT-1 cells was used to examine the efficacy and toxicity of HVH-2930. Results: HVH-2930 was rationally designed to fit into the ATP-binding pocket interface cavity of the hHSP90 homodimer in the C-terminal domain of HSP90, stabilizing its open conformation and hindering ATP binding. HVH-2930 induces apoptosis without inducing the HSR but by specifically suppressing the HER2 signaling pathway. This occurs with the downregulation of HER2/p95HER2 and disruption of HER2 family member heterodimerization. Attenuation of cancer stem cell (CSC)-like properties was associated with the downregulation of stemness factors such as ALDH1, CD44, Nanog and Oct4. Furthermore, HVH-2930 administration inhibited angiogenesis and tumor growth in trastuzumab-resistant xenograft mice. A synergistic effect was observed when combining HVH-2930 and paclitaxel in JIMT-1 xenografts. Conclusion: Our findings highlight the potent efficacy of HVH-2930 in overcoming trastuzumab resistance in HER2-positive breast cancer. Further investigation is warranted to fully establish its therapeutic potential.

Arsenite treatment induces Hsp90 aggregatesdistinct from conventional stress granules in fission yeast.

Various stress conditions, such as heat stress (HS) and oxidative stress, can cause biomolecular condensates represented by stress granules (SGs) via liquid-liquid phase separation. We have previously shown that Hsp90 forms aggregates in response to HS and that Hsp90 aggregates transiently co-localize with SGs as visualized by Pabp. Here, we showed that arsenite, one of the well-described SG-inducing stimuli, induces Hsp90 aggregates distinct from conventional SGs in fission yeast. Arsenite induced Hsp90 granules in a dose-dependent manner, and these granules were significantly diminished by the co-treatment with a ROS scavenger N-acetyl cysteine (NAC), indicating that ROS are required for the formation of Hsp90 granules upon arsenite stress. Notably, Hsp90 granules induced by arsenite do not overlap with conventional SGs as represented by eIF4G or Pabp, while HS-induced Hsp90 granules co-localize with SGs. Nrd1, an RNA-binding protein known as a HS-induced SG component, was recruited into Hsp90 aggregates but not to the conventional SGs upon arsenite stress. The non-phosphorylatable eIF2α mutants significantly delayed the Hsp90 granule formation upon arsenite treatment. Importantly, inhibition of Hsp90 by geldanamycin impaired the Hsp90 granule formation and reduced the arsenite tolerance. Collectively, arsenite stimulates two types of distinct aggregates, namely conventional SGs and a novel type of aggregates containing Hsp90 and Nrd1, wherein Hsp90 plays a role as a center for aggregation, and stress-specific compartmentalization of biomolecular condensates.

The small-molecule drug homoharringtonine targets HSF1 to suppress pancreatic cancer progression.

Heat shock factor 1 (HSF1), an essential transcription factor for stress response, is exploited by various tumors to facilitate their initiation, progression, invasion, and migration. Amplification of HSF1 is widely regarded as an indicator in predicting cancer severity, the likelihood of treatment failure and reduced patient survival. Notably, HSF1 is markedly amplified in 40% of pancreatic cancer (PC), which typically have limited treatment options. HSF1 has been proven to be a promising therapeutic target for multiple cancers. However, a direct small molecule HSF1 inhibitor with sufficient bioactivity and reliable safety has not been developed clinically. In this study, we successfully established a high-throughput screening system utilizing luciferase reporter assay specifically designed for HSF1, which leads to the discovery of a potent small molecule inhibitor targeting HSF1. Homoharringtonine (HHT) selectively inhibited PC cell viability with high HSF1 expression and induced a markedly stronger tumor regression effect in the subcutaneous xenograft model than the comparator drug KRIBB11, known for its direct action on HSF1. Moreover, HHT shows promise in countering the resistance encountered with HSP90 inhibitors, which have been observed to increase heat shock response intensity in clinical trials. Mechanistically, HHT directly bound to HSF1, suppressing its expression and thereby inhibiting transcription of HSF1 target genes. In conclusion, our work presents a preclinical discovery and validation for HHT as a HSF1 inhibitor for PC treatment.

Type II mode of JAK2 inhibition and destabilization are potential therapeutic approaches against the ruxolitinib resistance driven myeloproliferative neoplasms.

Ruxolitinib has been approved by the US FDA for the treatment of myeloproliferative neoplasms such as polycythemia vera and primary myelofibrosis. Ruxolitinib will remain a main stay in the treatment of MPN patients due to its effective therapeutic benefits. However, there have been instances of ruxolitinib resistance in MPN patients. As JAK2 is a direct target of ruxolitinib, we generated ruxolitinib-resistant clones to find out the mechanism of resistance. Cell-based screening strategy was used to detect the ruxolitinib-resistant mutations in JAK2. The Sanger sequencing method was used to detect the point mutations in JAK2. Mutations were re-introduced using the site-directed mutagenesis method and stably expressed in Ba/F3 cells. Drug sensitivities against the JAK2 inhibitors were measured using an MTS-based assay. JAK2 and STAT5 activation levels and total proteins were measured using immunoblotting. Computational docking studies were performed using the Glide module of Schrodinger Maestro software. In this study, we have recovered seven residues in the kinase domain of JAK2 that affect ruxolitinib sensitivity. All these mutations confer cross-resistance across the panel of JAK2 kinase inhibitors except JAK2-L983F. JAK2-L983F reduces the sensitivity towards ruxolitinib. However, it is sensitive towards fedratinib indicating that our screen identifies the drug-specific resistance profiles. All the ruxolitinib-resistant JAK2 variants displayed sensitivity towards type II JAK2 inhibitor CHZ-868. In this study, we also found that JAK1-L1010F (homologous JAK2-L983F) is highly resistant towards ruxolitinib suggesting the possibility of JAK1 escape mutations in JAK2-driven MPNs and JAK1 mutated ALL. Finally, our study also shows that HSP90 inhibitors are potent against ruxolitinib-resistant variants through the JAK2 degradation and provides the rationale for clinical evaluation of potent HSP90 inhibitors in genetic resistance driven by JAK2 inhibitors. Our study identifies JAK1 and JAK2 resistance variants against the type I JAK2 inhibitors ruxolitinib, fedratinib, and lestaurtinib. The sensitivity of these resistant variants towards the type II JAK2 inhibitor CHZ-868 indicates that this mode of type II JAK2 inhibition is a potential therapeutic approach against ruxolitinib refractory leukemia. This also proposes the development of potent and specific type II JAK2 inhibitors using ruxolitinib-resistance variants as a prototype.

17-AAG Induces Endoplasmic Reticulum Stress-mediated Apoptosis in Breast Cancer Cells, Possibly Through PERK/eIF2α Up-regulation.

Breast cancer is the most predominant type of cancer affecting women worldwide and the current therapeutic treatment for breast cancer patients is not adequately effective. This study aimed to investigate the mechanism of 17-AAG, a heat shock protein (HSP90) inhibitor, as a treatment for inducing breast cancer cell apoptosis. The pharmacology network was employed to examine the correlation of 17-AAG with the gene expression profiles of breast cancer, obtained by Gene Expression Profiling Interactive Analysis (GEPIA). MTT and flow cytometry were utilized to investigate cell proliferation and cell apoptosis, respectively. Dichloro-dihydro-fluorescein diacetate (DCFH-DA) assay and western blot analysis were employed to examine the correlation between cellular oxidant levels and protein expression. Immunofluorescence staining was utilized to confirm the protein localization and assess DNA damage. The pharmacological network analysis revealed that HSP90 serves as the common target connecting 17-AAG and breast cancer genes. Treatment with 17-AAG significantly increased cell apoptosis. Moreover, the treatment resulted in up-regulation of cellular oxidant levels and PERK/eIF2α expression. In line with these, protein localization after treatment revealed an increase in DNA damage, correlating with higher ER stress levels. Furthermore, GEPIA demonstrated that PERK and eIF2α expression were significantly higher in breast invasive carcinoma compared to other tumor types. HSP90 emerges as a potential target for inducing apoptosis in breast cancer cells by disrupting protein homeostasis in the endoplasmic reticulum, possibly through PERK/eIF2α up-regulation. 17-AAG, an HSP90 inhibitor, may therefore potentially hold an alternative therapeutic strategy for breast cancer treatment.

Rationally modified SNX-class Hsp90 inhibitors disrupt extracellular fibronectin assembly without intracellular Hsp90 activity.

Despite Hsp90's well documented promise as a target for developing cancer chemotherapeutics, its inhibitors have struggled to progress through clinical trials. This is, in part, attributed to the cytoprotective compensatory heat shock response (HSR) stimulated through intracellular Hsp90 inhibition. Beyond its intracellular role, secreted extracellular Hsp90 (eHsp90) interacts with numerous pro-oncogenic extracellular clients. This includes fibronectin, which in the tumour microenvironment enhances cell invasiveness and metastasis. Through the rational modification of known Hsp90 inhibitors (SNX2112 and SNX25a) we developed four Hsp90 inhibitory compounds, whose alterations restricted their interaction with intracellular Hsp90 and did not stimulate the HSR. Two of the modified cohort (compounds 10 and 11) were able to disrupt the assembly of the extracellular fibronectin network at non-cytotoxic concentrations, and thus represent promising new tool compounds for studying the druggability of eHsp90 as a target for inhibition of tumour invasiveness and metastasis.

HSPB8 Facilitates the Oncogenesis and Advancement of Bladder Cancer via Activation of HSP27.

Bladder cancer (BCa) stands as a significant malignancy within the genitourinary system. Notably, heat shock proteins (HSPs) exhibit elevated expression in cells subjected to environmental stresses and have been linked to the progression of many human malignancies. Among these, the functional implications and specific mechanism of HSPB8 in BCa have yet to be fully explored. In this study, we measured HSPB8 expression in both BCa tissues and various cell lines, further delving into its influence on cellular behaviors. Our observations pinpoint an upregulation of HSPB8 in BCa, a trend strongly associated with more advanced clinical manifestations. Suppressing HSPB8 exhibited marked reductions in cell proliferation and migration capabilities, while simultaneously amplifying apoptosis and inducing cell cycle arrest. Reinforcing these findings, our in vivo analyses using mouse models showed similar trends. Notably, upon HSPB8 knockdown, levels of specific proteins including eNOS (S1177), Hsp27 (S78/S82), PRAS40(T246), RSK1/2(S221/S227), and STAT3 (S727) decreased, with Hsp27 (S78/S82) and PRAS40(T246) experiencing the most profound drops. Furthermore, the application of an HSP27 inhibitor effectively reversed the phenotypes caused by increased HSPB8 expression. Collectively, our results suggest that elevated HSPB8 expression could act as a potential prognostic marker for BCa, and targeting HSPB8 might open new therapeutic avenues for treating this malignancy.

Evaluation of combined use of hsp90 inhibitor mpc-3100 and traditional cancer drug 5-fu on liver cancer cell lines

Hepatocellular carcinoma (HCC), which constitutes an important part of the global cancer burden, poses an important problem in the field of medicine. Combination therapy targets multiple mechanisms simultaneously using different therapeutic agents together. Heat shock protein 90 (HSP90) inhibitors are emerging as interesting targets in this area, since they play a vital role in the control of cellular processes and impact malignant cell survival and resistance mechanisms. This study evaluated the combined effect of the HSP90 inhibitor MPC-3100 and the traditional chemotherapy drug 5-fluorouracil (5-FU) on HCC. MTT assay was performed to evaluate the individual and combined cytotoxic effects of 5-FU and MPC-3100 on HUH-7 and HepG2 liver cancer cell lines. To assess the effectiveness of combination therapy, the Chou and Talalay method was applied. Both 5-FU and MPC-3100 and 5-FU+ MPC-3100 exhibited dose- and time-dependent cytotoxic effects. Combined administration of the two drugs showed an antagonistic impact on the cell lines. The findings demonstrated that combining 5-FU with MPC-3100 was less effective in inducing cytotoxicity in liver cancer cell lines compared to the use of each drug separately. In this context, the combination of these two drugs in liver cancer is not an appropriate strategy for effective treatment. Current research findings will help design more effective and targeted therapies for HCC and other cancers.

Therapeutic Potential of Heat Shock Protein 90 Inhibitors, Geldanamycin, and Analog Compounds in Precision Cancer Therapy

Heat shock protein (HSP90) is a molecular chaperone involved in numerous physiological processes. The primary role of this is to assist in the process of protein folding and to restore misfolded proteins to their correct shape. Chaperones additionally inhibit protein breakdown and aggregation. HSP90 inhibitors possess a notable characteristic of obstructing many cancer-causing pathways by facilitating the breakdown of numerous oncogenic client proteins. Targeting HSP90 therapeutics has been recognized as a viable approach for treating cancer and inflammatory-associated disorders in clinical studies involving different forms of cancer. Inhibition of HSP90 using natural, synthetic, and semi-synthetic chemicals has shown encouraging outcomes. HSP90 inhibitors have been extracted from several fungi, bacteria, and plant species. These naturally occurring chemicals play a crucial function in regulating HSP90 activity and can be utilized to develop innovative semi-synthetic or synthetic inhibitors. Over 120 clinical trials have been carried out to evaluate the effectiveness of HSP90 inhibitors as a supplementary therapy for different types of tumor cells. Presently, ongoing research is being carried out to acquire an understanding of innovative and more efficacious methods for treating cancer. Continuing in this research approach, we aim to investigate the discovery, biosynthesis, mechanism of action, and biological features of geldanamycin and its analogs.

A newly identified 45-kDa JAK2 variant with an altered kinase domain structure represents a novel mode of JAK2 kinase inhibitor resistance.

Tyrosine-protein kinase (janus kinase; JAK)-signal transducer and activator of transcription (STAT) signaling plays a pivotal role in the development of myeloproliferative neoplasms (MPNs). Treatment with the potent JAK1/JAK2-specific inhibitor, ruxolitinib, significantly reduces tumor burden; however, ruxolitinib treatment does not fully eradicate the malignant clone. As the molecular basis for the disease persistence is not well understood, we set out to gain new insights by generating ruxolitinib-resistant cell lines. Surprisingly, these cells harbor a 45 kDa JAK2 variant (FERM-JAK2) consisting of the N-terminal FERM domain directly fused to the C-terminal kinase domain in 80% of sublines resistant to ruxolitinib. At the molecular level, FERM-JAK2 is able to directly bind and activate STAT5 in the absence of cytokine receptors. Furthermore, phosphorylation of activation-loop tyrosines is dispensable for FERM-JAK2-mediated STAT5 activation and cellular transformation, in contrast to JAK2-V617F. As a result, FERM-JAK2 is highly resistant to several ATP-competitive JAK2 inhibitors, whereas it is particularly sensitive to HSP90 inhibition. A murine model of FERM-JAK2 leukemogenesis showed an accelerated MPN phenotype with pronounced splenomegaly. Notably, most current protocols for the monitoring of emerging JAK variants are unable to detect FERM-JAK2, highlighting the urgent need for implementing next-generation sequencing approaches in MPN patients receiving ruxolitinib.