The selective Hsp90 inhibitor BJ-B11 exhibits potent antitumor activity via induction of cell cycle arrest, apoptosis and autophagy in Eca-109 human esophageal squamous carcinoma cells

JD-02, a novel Hsp90 inhibitor, induces ROS/SRC axis-dependent cytoprotective autophagy in colorectal cancer cells

Heat shock protein 90 (Hsp90) is a tumor marker that accelerates cancer growth by disrupting protein homeostasis. However, concerns such as low clinical efficacy and drug resistance continue to be obstacles to the successful marketing of Hsp90 inhibitors. The cytoprotective function of autophagy has been identified as one of the mechanisms by which tumor cells gain resistance to chemotherapy. JD-02 was identified as a new Hsp90 inhibitor that suppressed colorectal cancer (CRC) growth by lowering client protein levels in vivo and in vitro. We found that JD-02 increased cellular autophagy, which inhibited apoptosis. JD-02 enhanced cytoprotective autophagy and regulated apoptotic suppression by increasing intracellular reactive oxygen species and inhibiting SRC protein levels, as demonstrated by quantitative proteomics, bioinformatic analysis, western blotting, and flow cytometry. This effect was reversed by autophagy inhibition. Therefore, due to the synergistic effects of Hsp90 and autophagy inhibitors in efficiently activating apoptotic pathways, they could potentially serve as promising therapeutic options for CRC.

BJ-B11, an Hsp90 Inhibitor, Constrains the Proliferation and Invasion of Breast Cancer Cells

Breast cancer is the leading cause of cancer-related deaths in women; however, its underlying etiology remains largely unknown. In this study, we systematically analyzed breast cancer tissues using comprehensive iTRAQ labeled quantitative proteomics, identifying 841 differentially expressed proteins (474 and 367 significantly over- and under-expressed, respectively), which were annotated by protein domain analysis. All the heat shock proteins identified were upregulated in breast cancer tissues; Hsp90 upregulation was also validated by RT-qPCR and immunohistochemistry, and high Hsp90 protein levels correlated with poorer survival. Hsp90AA1 overexpression promoted MDA-MB-231 cell proliferation, whilst BJ-B11, an Hsp90 inhibitor, hampered their invasion, migration, and proliferation in a time and dose-dependent manner and induced cell cycle arrest and apoptosis. BJ-B11 inhibited the expression of epithelial-mesenchymal transition (EMT) marker in MDA-MB-231 cells, whereas Hsp90AA1 promoted its expression. Moreover, BJ-B11 inhibited tumor growth in xenograft model. Altogether, Hsp90 activation is a risk factor in breast cancer patients, and BJ-B11 could be used to treat breast cancer.

Identification of the circRNA-miRNA-mRNA regulatory network of Hsp90 inhibitor-induced cell death in colorectal cancer by integrated analysis

Colorectal cancer (CRC) is a global disease with high incidence and mortality rate. Hsp90 inhibitors induce cell death in various cancers, including CRC. However, the underlying mechanisms need to be clarified further. In this study, Caco-2 cells were treated with 0.25 μM SNX-2112, an Hsp90 inhibitor, for 48 h; subsequently, whole-transcriptome sequencing was performed. At the mRNA level in SNX-2112-treated Caco-2 cells, 1588 genes were upregulated, and 433 genes were downregulated. Six genes were found to be associated with necroptosis and apoptosis, and these 6 upregulated genes were validated by RT-qPCR. Hundred and six miRNAs were upregulated, and 48 miRNAs were downregulated in SNX-2112-treated Caco-2 cells. Eleven downregulated miRNAs were found to interact with the 6 upregulated genes. Moreover, 676 circRNAs were upregulated, and 291 circRNAs were downregulated in SNX-2112-treated Caco-2 cells. Among them, 126 circRNAs were found to be the target of the 11 downregulated miRNAs. The circRNA-miRNA-mRNA regulatory network of Hsp90 inhibitor-induced cell death in colorectal cancer was constructed. This regulatory network extends the underlying mechanism of Hsp90 and improves our understanding of Hsp90 inhibitors as potential targeted therapeutic agents.

CFTR interacts with Hsp90 and regulates the phosphorylation of AKT and ERK1/2 in colorectal cancer cells

Cystic fibrosis (CF) is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. CF cells and tissues exhibit various mitochondrial abnormalities. However, the underlying molecular mechanisms remain elusive. Here, we examined the mechanisms through which CFTR regulates Bcl‐2 family proteins, which in turn regulate permeabilization of the mitochondrial outer membrane. Notably, inhibition of CFTR activated Bax and Bad, but inhibited Bcl‐2. Moreover, degradation of phosphorylated extracellular signal‐regulated kinase 1/2 (ERK1/2) and AKT increased significantly in CFTR‐knockdown cells. Dysfunction of CFTR decreased heat‐shock protein 90 (Hsp90) mRNA levels, and CFTR was found to interact with Hsp90. Inhibition of Hsp90 by SNX‐2112 induced the degradation of phosphorylated AKT and ERK1/2 in Caco2 and HRT18 cells. These findings may help provide insights into the physiological role of CFTR in CF‐related diseases.

Inhibition of autophagosome-lysosome fusion by ginsenoside Ro via the ESR2-NCF1-ROS pathway sensitizes esophageal cancer cells to 5-fluorouracil-induced cell death via the CHEK1-mediated DNA damage checkpoint

Modulation of autophagy has been increasingly regarded as a promising cancer therapeutic approach. In this study, we screened several ginsenosides extracted from Panax ginseng and identified ginsenoside Ro (Ro) as a novel autophagy inhibitor. Ro blocked the autophagosome-lysosome fusion process by raising lysosomal pH and attenuating lysosomal cathepsin activity, resulting in the accumulation of the autophagosome marker MAP1LC3B/LC3B and SQSTM1/p62 (sequestosome 1) in various esophageal cancer cell lines. More detailed studies demonstrated that Ro activated ESR2 (estrogen receptor 2), which led to the activation of NCF1/p47(PHOX) (neutrophil cytosolic factor 1), a subunit of NADPH oxidase, and subsequent reactive oxygen species (ROS) production. Treatment with siRNAs or inhibitors of the ESR2-NCF1-ROS axis, such as N-acetyl-L-cysteine (NAC), diphenyleneiodonium chloride (DPI), apocynin (ACN), Tiron, and Fulvestrant apparently decreased Ro-induced LC3B-II, GFP-LC3B puncta, and SQSTM1, indicating that ROS instigates autophagic flux inhibition triggered by Ro. More importantly, suppression of autophagy by Ro sensitized 5-fluorouracil (5-Fu)-induced cell death in chemoresistant esophageal cancer cells. 5-Fu induced prosurvival autophagy, and by inhibiting such autophagy, siRNAs against BECN1/beclin 1, ATG5, ATG7, and LC3B enhanced 5-Fu-induced autophagy-associated and apoptosis-independent cell death. We observed that Ro potentiates 5-Fu cytotoxicity via delaying CHEK1 (checkpoint kinase 1) degradation and downregulating DNA replication process, resulting in the delayed DNA repair and the accumulation of DNA damage. In summary, these data suggest that Ro is a novel autophagy inhibitor and could function as a potent anticancer agent in combination therapy to overcome chemoresistance.

Metabolism elucidation of BJ-B11 (a heat shock protein 90 inhibitor) by human liver microsomes: identification of main contributing enzymes

OBJECTIVE

The aim of this article is to elucidate the metabolic pathways of BJ-B11, a heat shock protein 90 inhibitor, in human liver microsomes (HLM) and determine the main enzymes responsible for formation of each metabolite.

METHODS

Metabolites of BJ-B11 were identified using the ultra performance liquid chromatography- quadrupole time-of-flight/mass spectrometry (UPLC-QTOF/MS) method. Esterase contributing to the hydrolysis of BJ-B11 was identified by chemical inhibition and activity correlation assays. Reaction phenotyping and kinetic studies using expressed cytochrome P450 (CYP) enzymes were performed to determine the contributions of CYP isozymes to BJ-B11 metabolism.

RESULTS

BJ-B11 was rapidly hydrolyzed to generate a deacetylated product M1-1. M1-1 was subsequently metabolized to form eight metabolites. Hydrolysis of BJ-B11 was markedly inhibited by vinblastine (a dual inhibitor of arylacetamide deacetylase and carboxylesterase 2). By contrast, digitonin and telmisartan (the specific inhibitors for carboxylesterase 1 and carboxylesterase 2, respectively) did not inhibit BJ-B11 hydrolysis at all. Further, BJ-B11 hydrolysis was significantly correlated with hydrolysis of phenacetin (an activity marker of arylacetamide deacetylase). Moreover, reaction phenotyping revealed that metabolism of M1-1 in HLM was attributable to several CYP enzymes, including CYP1A1, 1B1, 3A4 and 3A5.

CONCLUSION

BJ-B11 was subjected to efficient metabolism in the liver, generating nine metabolites. BJ-B11 metabolism was contributed mainly by arylacetamide deacetylase and multiple CYP enzymes.

Inhibition of heat shock protein 90 suppresses squamous carcinogenic progression in a mouse model of esophageal cancer

PURPOSE

Heat shock protein 90 (Hsp90), a potential therapeutic target, has been widely recognized in vitro and in vivo in immunodeficient mice. Here, we aimed to evaluate the role of Hsp90 in an immunocompetent mouse model of esophageal squamous cell cancer (ESCC).

METHODS

The carcinogen 4-nitroquinoline 1-oxide (4NQO) was used to induce ESCC in C57BL/6 mice. Cancer progression was analyzed through observation of appearance, hematoxylin-eosin staining, immunohistochemical detection, and terminal dUTP nick-end labeling analysis.

RESULTS

4NQO led to the progressive appearance of preneoplastic and tumoral lesions in the esophagus, with 100 % incidence of ESCC in situ occurring only after 16 weeks of carcinogen exposure. Most of these lesions evolved spontaneously into highly invasive ESCC even after 4NQO withdrawal (weeks 16-22). Interestingly, there was marked upregulation of Hsp90 and its client proteins in tumoral lesions at 22 weeks. Hsp90 inhibition by intraperitoneal injection of SNX-2112 over the following 2 weeks downregulated AKT and cyclin D1 expression, leading to significant reduction in tumor incidence and prevention of ESCC progression. Moreover, SNX-2112 treatment decreased proliferating cell nuclear antigen expression and increased the number of apoptotic cells in ESCC tissues.

CONCLUSIONS

Our in vivo findings support the contribution of Hsp90 to ESCC progression, which was achieved by stimulating apoptosis and inhibition of cell proliferation, and provide a strong rationale for further evaluation of Hsp90 inhibitors for treating ESCC.

Combination of SNX-2112 with 5-FU exhibits antagonistic effect in esophageal cancer cells

The low efficacy of single-drug chemotherapy forms the basis for combination therapy in esophageal squamous cell carcinoma. SNX-2112, a selective heat shock protein 90 (Hsp90) inhibitor, was recently reported as being effective in combination with cisplatin and paclitaxel. In this study, we investigated the effect of SNX-2112 in combination with 5-fluorouracil (5-FU), another first-line anticancer drug, in esophageal cancer. Unexpectedly, tetrazolium assay revealed that the combination of SNX-2112 with 5-FU exhibited antagonistic effect. Flow cytometry revealed that the SNX-2112 and 5-FU combination greatly decreased the number of G2/M cells compared to SNX-2112-only treatment in Eca‑109 cells. This effect might be related to the altered mRNA level of cyclin-related genes including cyclin D1, Chk2 and Cdk4. Further, 5-FU attenuated SNX-2112-induced apoptosis by decreasing poly(ADP-ribose) polymerase (PARP) cleavage and inactivating caspase-3, -8 and -9. Additionally, 5-FU suppressed the SNX-2112-induced decrease of mitochondrial membrane potential. Moreover, 5-FU partly recovered Hsp90 client proteins, including Akt, p-Akt, inhibitor of κB kinase (IKK)α, extracellular signal-regulated kinase (ERK)1/2, and glycogen synthase kinase (GSK)-3β, which SNX-2112 had downregulated. Taken together, this is the first report that the combination of SNX-2112 with 5-FU exhibited antagonistic effect in esophageal cancer cells by affecting growth inhibition, cell cycle, apoptosis, and Hsp90 client proteins, suggesting that care is required in the clinical application of combined SNX-2112 and 5-FU.

BIIB021, an Hsp90 inhibitor, effectively kills a myelodysplastic syndrome cell line via the activation of caspases and inhibition of PI3K/Akt and NF-κB pathway proteins

The novel orally available inhibitor of the molecular chaperone heat shock protein 90 (Hsp90), BIIB021, induces the apoptosis of various types of tumor cell in vitro and in vivo. However, the effects and mechanisms of this agent on myelodysplastic syndrome (MDS) cell lines remain unknown. The aim of this study was to investigate the effects of BIIB021 on SKM-1 cells (a MDS cell line) and examine its mechanisms of action. The results showed that BIIB021 inhibited the growth of SKM-1 cells effectively in vitro. The treatment of SKM-1 cells with BIIB021 resulted in the inhibition of cell growth through G0/G1-phase cell cycle arrest and induced apoptosis by activating caspase-3, -8 and -9. Furthermore, this study also demonstrated that the mechanisms of apoptosis in SKM-1 cells were associated with the suppression of the phosphatidylinositide 3-kinase/Akt and nuclear factor-κB signaling pathways. Therefore, the findings indicate a novel approach for the treatment of high-risk MDS.