Identifying inhibitors of epithelial-mesenchymal transition by connectivity map-based systems approach

Systematic computational strategies for identifying protein targets and lead discovery

Computational algorithms and tools have retrenched the drug discovery and development timeline. The applicability of computational approaches has gained immense relevance owing to the dramatic surge in the structural information of biomacromolecules and their heteromolecular complexes. Computational methods are now extensively used in identifying new protein targets, druggability assessment, pharmacophore mapping, molecular docking, the virtual screening of lead molecules, bioactivity prediction, molecular dynamics of protein-ligand complexes, affinity prediction, and for designing better ligands. Herein, we provide an overview of salient components of recently reported computational drug-discovery workflows that includes algorithms, tools, and databases for protein target identification and optimized ligand selection.

Effective Drug Concentration and Selectivity Depends on Fraction of Primitive Cells

Poor efficiency of chemotherapeutics in the eradication of Cancer Stem Cells (CSCs) has been driving the search for more active and specific compounds. In this work, we show how cell density-dependent stage culture profiles can be used in drug development workflows to achieve more robust drug activity (IC₅₀ and EC₅₀) results. Using flow cytometry and light microscopy, we characterized the cytological stage profiles of the HL-60-, A-549-, and HEK-293-derived sublines with a focus on their primitive cell content. We then used a range of cytotoxic substances—C-123, bortezomib, idarubicin, C-1305, doxorubicin, DMSO, and ethanol—to highlight typical density-related issues accompanying drug activity determination. We also showed that drug EC₅₀ and selectivity indices normalized to primitive cell content are more accurate activity measurements. We tested our approach by calculating the corrected selectivity index of a novel chemotherapeutic candidate, C-123. Overall, our study highlights the usefulness of accounting for primitive cell fractions in the assessment of drug efficiency.

Systemic sclerosis biomarkers detection in the secretome of TGFβ1-activated primary human lung fibroblasts

TGFβ1 is a profibrotic mediator that contributes to a broad spectrum of pathologies, including systemic sclerosis-associated pulmonary fibrosis (SSc-PF). However, the secretome of TGFβ1-stimulated primary human normal lung (NL) fibroblasts has not been well characterized. Using fluorescent 2-dimensional gel electrophoresis (2D-PAGE) and differential gel electrophoresis (DIGE) followed by Mass Spectrometry, we identified 37 differentially secreted proteins in the conditioned media of TGFβ1-activated NL fibroblasts and generated a protein-protein association network of the TGFβ1 secretome using STRING. Functional enrichment revealed that several biological processes and pathways characteristic of PF were enriched. Additionally, by comparing the TGFβ1 secretome of NL fibroblasts to proteomic biomarkers from biological fluids of systemic sclerosis (SSc) patients, we identified 11 overlapping proteins. Together our data validate the TGFβ1-induced secretome of NL fibroblasts as a valid in vitro model that reflects SSc biomarkers and identify potential therapeutic targets for SSc-PF. SIGNIFICANCE: All proteins secreted by fibroblasts into the extracellular space, representing the secretome, promote cell-to-cell communication as well as tissue homeostasis, immune mechanisms, developmental regulation, proteolysis, development of the extracellular matrix (ECM) and cell adhesion. Therefore, it is crucial to understand how TGFβ1, a well-known profibrotic cytokine, modulates the secretome of pulmonary fibroblasts, and how the TGFβ1-induced secretome resembles biomarkers in SSc. Using functional enrichment analysis, key pathways and hub proteins can be identified and studied as potential therapeutic targets for pulmonary fibrosis.

miR-944 Suppresses EGF-Induced EMT in Colorectal Cancer Cells by Directly Targeting GATA6

Background

miR-944 belongs to the MicroRNAs family, as shown in our previous study, and is essential in the colorectal cancer (CRC) progression. It is negatively associated with invasion depth and lymph node status. Epithelial-mesenchymal transition (EMT) is essential in tumor invasion and metastasis. However, the relationship between miR-944 and EMT in CRC is unknown and should be further investigated.

Methods

Epithelial–mesenchymal transition (EMT) progression in CRC cell lines was detected with Cell morphology and Western blotting. CRC cell migration and invasion were examined using Transwell assays. Transcriptome and clinical data were obtained from The Cancer Genome Atlas (TCGA) database. The potential pathway of miR-944 and GATA6 were predicted using KEGG analysis. Colocalization was validated using immunofluorescence and Immunohistochemistry. Nuclear and Cytoplasmic Protein Extraction assays were conducted to determine the effects of miR-944 on Wnt/β-catenin signaling.

Results

We found that miR‑944 influences EGF-induced EMT malignant phenotype in vitro. KEGG analyses showed that miR-944 and GATA6 are associated with EMT related pathways, wnt signaling pathways. On the other hand, Western Blot analyses showed that miR-944 can regulate EMT and wnt-β-catenin pathway-related protein, including β-catenin, ZEB1, snail1 via GATA6 regulation. miR-944 also abrogates E-ca after EGF induction. Immunohistochemistry (IHC) and Immunofluorescence (IF) co-expression showed that GATA6 expression is positively associated with β-catenin and ZEB1. GATA6 silencing can reverse EMT malignant phenotype and alterations of related protein induced by miR-944. Quantitative polymerase chain reaction analysis results showed that miR-944 is negatively associated with the UICC stage (P= 0.02), lymph nodes (p=0.04), and liver metastasis (p=0.03). Moreover, patients with high miR-944 expression have better survival (p=0.045). We finally combined miR-944 and GATA6 and found that miR-944/GATA6 ratio could be a novel prognostic biomarker in the TCGA dataset and it is an independent risk prognosis factor (p=0.045).

Conclusion

Our results suggest that miR-944 suppresses the aggressive biological processes by directly repressing GATA6 expression and could be a potential candidate for therapeutic applications in CRC.

Sodium Propionate Attenuates the Lipopolysaccharide-Induced Epithelial-Mesenchymal Transition via the PI3K/Akt/mTOR Signaling Pathway

Short-chain fatty acids (SCFAs), especially propionate, originate from the fermentation of dietary fiber in the gut and play a key role in inhibiting pulmonary inflammation. Chronic inflammation may induce an epithelial-mesenchymal transition (EMT) in alveolar epithelial cells and result in fibrotic disorders. This study was designed to investigate the beneficial effect of sodium propionate (SP) on lipopolysaccharide (LPS)-induced EMT. In cultured BEAS-2B cells, the protein expression levels of E-cadherin, α-smooth muscle actin (SMA), and vimentin were 0.66 ± 0.20, 1.44 ± 0.23, and 1.32 ± 0.21 in the LPS group vs 1.11 ± 0.36 (P < 0.05), 1.04 ± 0.30 (P < 0.05), and 0.96 ± 0.13 (P < 0.01) in the LPS + SP group (mean ± standard deviation), respectively. Meanwhile, LPS-triggered inflammatory cytokines and extracellular proteins were also reduced by SP administration in BEAS-2B cells. Moreover, SP treatment attenuated inflammation, EMT, extracellular matrix (ECM) deposition, and even fibrosis in a mouse EMT model. In terms of mechanism, LPS-treated BEAS-2B cells exhibited a higher level of phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) phosphorylation, which was interrupted by SP treatment. It is worth noting that the blockade of the PI3K/Akt/mTOR signaling cascade reduced the LPS-evoked EMT process in BEAS-2B cells. These results suggest that SP can block LPS-induced EMT via inhibition of the PI3K/Akt/mTOR signaling cascade, which provides a basis for possible clinical use of SP in airway and lung diseases.

Recent Advances in Cancer Plasticity: Cellular Mechanisms, Surveillance Strategies, and Therapeutic Optimization

The processes of recurrence and metastasis, through which cancer relapses locally or spreads to distant sites in the body, accounts for more than 90% of cancer-related deaths. At present there are very few treatment options for patients at this stage of their disease. The main obstacle to successfully treat advanced cancer is the cells' ability to change in ways that make them resistant to treatment. Understanding the cellular mechanisms that mediate this cancer cell plasticity may lead to improved patient survival. Epigenetic reprogramming, together with tumor microenvironment, drives such dynamic mechanisms favoring tumor heterogeneity, and cancer cell plasticity. In addition, the development of new approaches that can report on cancer plasticity in their native environment have profound implications for studying cancer biology and monitoring tumor progression. We herein provide an overview of recent advancements in understanding the mechanisms regulating cell plasticity and current strategies for their monitoring and therapy management.

Reversal of Epithelial-Mesenchymal Transition by Natural Anti-Inflammatory and Pro-Resolving Lipids

Epithelial mesenchymal transition (EMT) is a key process in the progression of malignant cancer. Therefore, blocking the EMT can be a critical fast track for the development of anticancer drugs. In this paper, we update recent research output of EMT and we explore suppression of EMT by natural anti-inflammatory compounds and pro-resolving lipids.

Defining Protein Pattern Differences Among Molecular Subtypes of Diffuse Gliomas Using Mass Spectrometry

Molecular characterization of diffuse gliomas has thus far largely focused on genomic and transcriptomic interrogations. Here, we utilized mass spectrometry and overlay protein-level information onto genomically defined cohorts of diffuse gliomas to improve our downstream molecular understanding of these lethal malignancies. Bulk and macrodissected tissues were utilized to quantitate 5,496 unique proteins over three glioma cohorts subclassified largely based on their IDH and 1p19q codeletion status (IDH wild type (IDHwt), n = 7; IDH mutated (IDHmt), 1p19q non-codeleted, n = 7; IDH mutated, 1p19q-codeleted, n = 10). Clustering analysis highlighted proteome and systems-level pathway differences in gliomas according to IDH and 1p19q-codeletion status, including 287 differentially abundant proteins in macrodissection-enriched tumor specimens. IDHwt tumors were enriched for proteins involved in invasiveness and epithelial to mesenchymal transition (EMT), while IDHmt gliomas had increased abundances of proteins involved in mRNA splicing. Finally, these abundance changes were compared with IDH-matched GBM stem-like cells (GSCs) to better pinpoint protein patterns enriched in putative cellular drivers of gliomas. Using this integrative approach, we outline specific proteins involved in chloride transport (e.g. chloride intracellular channel 1, CLIC1) and EMT (e.g. procollagen-lysine, 2-oxoglutarate 5-dioxygenase 3, PLOD3, and serpin peptidase inhibitor clade H member 1, SERPINH1) that showed concordant IDH-status-dependent abundance differences in both primary tissue and purified GSC cultures. Given the downstream position proteins occupy in driving biology and phenotype, understanding the proteomic patterns operational in distinct glioma subtypes could help propose more specific, personalized, and effective targets for the management of patients with these aggressive malignancies.

Crosstalk between autophagy and epithelial-mesenchymal transition and its application in cancer therapy

Autophagy is a highly conserved catabolic process that mediates degradation of pernicious or dysfunctional cellular components, such as invasive pathogens, senescent proteins, and organelles. It can promote or suppress tumor development, so it is a “double-edged sword” in tumors that depends on the cell and tissue types and the stages of tumor. The epithelial-mesenchymal transition (EMT) is a complex biological trans-differentiation process that allows epithelial cells to transiently obtain mesenchymal features, including motility and metastatic potential. EMT is considered as an important contributor to the invasion and metastasis of cancers. Thus, clarifying the crosstalk between autophagy and EMT will provide novel targets for cancer therapy. It was reported that EMT-related signal pathways have an impact on autophagy; conversely, autophagy activation can suppress or strengthen EMT by regulating various signaling pathways. On one hand, autophagy activation provides energy and basic nutrients for EMT during metastatic spreading, which assists cells to survive in stressful environmental and intracellular conditions. On the other hand, autophagy, acting as a cancer-suppressive function, is inclined to hinder metastasis by selectively down-regulating critical transcription factors of EMT in the early phases. Therefore, the inhibition of EMT by autophagy inhibitors or activators might be a novel strategy that provides thought and enlightenment for the treatment of cancer. In this article, we discuss in detail the role of autophagy and EMT in the development of cancers, the regulatory mechanisms between autophagy and EMT, the effects of autophagy inhibition or activation on EMT, and the potential applications in anticancer therapy.

Heat Shock Proteins (HSPs): A Novel Target for Cancer Metastasis Prevention

Background:

Heat shock proteins (HSPs) are predominant molecular chaperones which are actively involved in the protein folding; which is essential in protecting the structure and functioning of proteins during various stress conditions. Though HSPs have important physiological roles, they have been well known for their roles in various pathogenic conditions such as carcinogenesis; however, limited literature has consolidated its potential as an anti-metastatic drug target.

Objectives:

The present review outlines the role of different HSPs on cancer progression and metastasis; possible role of HSP inhibitors as anti-neoplastic agents is also discussed.

Methods:

The data were collected from PubMed/Medline and other reputed journal databases. The literature that was too old and had no significant role to the review was then omitted.

Results:

Despite their strong physiological functions, HSPs are considered as good markers for cancer prognosis and diagnosis. They have control over survival, proliferation and progression events of cancer including drug resistance, metastasis, and angiogenesis. Since, neoplastic cells are more dependent on HSPs for survival and proliferation, the selectivity and specificity of HSP-targeted cancer drugs remain high. This has made various HSPs potential clinical and experimental targets for cancer prevention. An array of HSP inhibitors has been in trials and many others are in experimental conditions as anticancer and anti-metastatic agents. Several natural products are also being investigated for their efficacy for anticancer and anti-metastatic agents by modulating HSPs.

Conclusion:

Apart from their role as an anticancer drug target, HSPs have shown to be promising targets for the prevention of cancer progression. Extensive studies are required for the use of these molecules as anti-metastatic agents. Further studies in this line may yield specific and effective antimetastatic agents.

Statins may have double-edged effects in patients with lung adenocarcinoma after lung resection

Purpose: The epithelial to mesenchymal transition (EMT) is pivotal for driving metastasis and recurrence in lung cancer. Some in vitro reports have shown that statins suppress EMT by inactivating mutant p53 functions. Several clinical trials of conventional treatments with statins have been performed, but the effect of these drugs on prognosis is still uncertain. The purpose of this study is to examine the impact of statins on EMT and the prognosis of patients with lung adenocarcinoma.

Materials and methods: Morphological changes were evaluated and EMT markers (E-cadherin, vimentin) were analyzed by Western blotting in p53-overexpressing H1650 and mutant p53-harboring H1975 lung adenocarcinoma cells, with and without simvastatin administration. The invasive ability of these cells was analyzed in a Matrigel chemoinvasion assay. A total of 250 lung adenocarcinoma specimens were also collected from patients who underwent surgery in our institute. EMT markers in these tumor specimens were evaluated by immunostaining and p53 mutation status was determined by direct sequencing. Associations among EMT status, p53 mutation status, and statin use were evaluated, and prognosis was analyzed using a marginal structural model.

Results: Mutant p53 induced EMT and increased the invasive ability of H1650 cells. Simvastatin restored the epithelial phenotype and decreased the invasive ability of both H1650 and H1975 cells. Statin administration was associated with inactivation of EMT only in patients with mutant p53, which was consistent with the in vitro results. Moreover, in patients with mutant p53, statin users had significantly better survival than non-statin users. In contrast, statins significantly worsened the prognosis of patients with wild type p53 (HR 2.10, 95% CI 1.14–3.85).

Conclusion: Statins suppress EMT and change the prognosis of patients with lung adenocarcinoma in a p53 mutation-dependent manner.

Heterogeneity and Plasticity of Breast Cancer Stem Cells

In the last 20 years, the conventional view of breast cancer as a homogeneous collection of highly proliferating malignant cells was totally replaced by a model of increased complexity, which points out that breast carcinomas are tissues composed of multiple populations of transformed cells. A large diversity of host cells and structural components of the extracellular matrix constitute the mammary tumour microenvironment, which supports its growth and progression, where individual cancer cells evolve with cumulative phenotypic and genetic heterogeneity. Moreover, contributing to this heterogeneity, it has been demonstrated that breast cancers can exhibit a hierarchical organization composed of tumour cells displaying divergent lineage biomarkers and where, at the apex of this hierarchy, some neoplastic cells are able to self-renew and to aberrantly differentiate. Breast cancer stem cells (BCSCs), as they were entitled, not only drive tumourigenesis, but also mediate metastasis and contribute to therapy resistance.Recently, adding more complexity to the system, it has been demonstrated that BCSCs maintain high levels of plasticity, being able to change between mesenchymal-like and epithelial-like states in a process regulated by the tumour microenvironment. These stem cell state transitions play a fundamental role in the process of tumour metastasis, as well as in the resistance to putative therapeutic strategies to target these cells. In this chapter, it will be mainly discussed the emerging knowledge regarding the contribution of BCSCs to tumour heterogeneity, their plasticity, and the role that this plasticity can play in the establishment of distant metastasis. A major focus will also be given to potential clinical implications of these discoveries in breast cancer recurrence and to possible BCSC targeted therapeutics by the use of specific biomarkers.

Gene expression profile-based drug screen identifies SAHA as a novel treatment for NAFLD

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide.

Metformin sensitizes hypoxia-induced gefitinib treatment resistance of HNSCC via cell cycle regulation and EMT reversal

Objectives

The objectives of this study were to explore the mechanisms of metformin sensitization to hypoxia-induced gefitinib treatment in resistant head and neck squamous cell carcinoma (HNSCC) and evaluate the effects of this combined treatment strategy.

Methods

The effects of gefitinib treatment on HNSCC were measured under normoxic and hypoxic conditions. The relationship between hypoxia and cell cycle and epithelial-mesenchymal transition (EMT) in tumor cells were analyzed. Palbociclib and LY294002 were used in combination with gefitinib to evaluate the effects on HNSCC cell cytotoxicity during hypoxia. Finally, metformin was used to evaluate the sensitizing effects of gefitinib treatment on HNSCC in vivo and in vitro.

Results

Cell viability and apoptosis assays demonstrated a significant difference in HNSCC cells treated with gefitinib between the normoxia and hypoxia groups. Hypoxia induced the expression of cyclin D1, decreased the percentage of cells in G1, and promoted the EMT of tumor cells. Both palbociclib and LY294002 enhanced gefitinib-induced cytotoxicity of HNSCC cells under hypoxic conditions. Encouragingly, metformin sensitized HNSCC to gefitinib treatment in vivo and in vitro.

Conclusion

Hypoxia promotes G1-S cell cycle progression and EMT in HNSCC, resulting in gefitinib treatment resistance. Metformin sensitizes HNSCC to gefitinib treatment, which might serve as a novel combined treatment strategy.

Cellular Phenotype Plasticity in Cancer Dormancy and Metastasis

Cancer dormancy is a period of cancer progression in which residual tumor cells exist, but clinically remain asymptomatic for a long time, as well as resistant to conventional chemo- and radiotherapies. Cellular phenotype plasticity represents that cellular phenotype could convert between epithelial cells and cells with mesenchymal traits. Recently, this process has been shown to closely associate with tumor cell proliferation, cancer dormancy and metastasis. In this review, we have described different scenarios of how the transition from epithelial to mesenchymal morphology (EMT) and backwards (MET) are connected with the initiation of dormancy and reactivation of proliferation. These processes are fundamental for cancer cells to invade tissues and metastasize. Recognizing the mechanisms underlying the cellular phenotype plasticity as well as dormancy and targeting them is likely to increase the efficiency of traditional tumor treatment inhibiting tumor metastasis.

Reduction of cardiac TGFβ-mediated profibrotic events by inhibition of Hsp90 with engineered protein

Myocardial fibroblast activation coupled with extracellular matrix production is a pathological signature of myocardial fibrosis and is governed mainly by transforming growth factor TGFβ-Smad2/3 signaling. Targeting the ubiquitous TGFβ leads to cellular homeostasis deregulation with adverse consequences. We previously showed the anti-fibrotic effects upon downregulation of 90-kDa heat shock protein (Hsp90), a chaperone that associates to the TGFβ signaling cascade. In the present study, we use a fluorescent-labeled Hsp90 protein inhibitor (CTPR390-488) with specific Hsp90 binding properties to reduce myocardial pro-fibrotic events in vitro and in vivo. The mechanism of action involves the disruption of TGFβRI-Hsp90 complex, resulting in a decrease in TGFβ signaling and reduction in extracellular matrix collagen. In vivo, decreased myocardial collagen deposition was observed upon CTPR390-488 treatment in a pro-fibrotic mouse model. This is the first study demonstrating the ability of an engineered Hsp90 protein inhibitor to block collagen expression, reduce the motility of myocardial TGFβ-activated fibroblasts and ameliorate angiotensin-II induced cardiac myocardial fibrosis in vivo.

Inhibition of mTOR ameliorates bleomycin-induced pulmonary fibrosis by regulating epithelial-mesenchymal transition

Epithelial-mesenchymal transition (EMT) plays a pivotal role in idiopathic pulmonary fibrosis (IPF). In bleomycin-induced pulmonary fibrosis mice, we observed that inhibition of mTOR (mammalia target of rapamycin) attenuated IPF. Rapamycin suppressed the down-regulation of E-cadherin and up-regulation of fibronectin in bleomycin-induced pulmonary fibrosis mice. In addition, dual immunofluorescence staining for E-cadherin and fibronectin demonstrated that rapamycin pretreatment decreased the proportions of AECs undergoing EMT in bleomycin-induced pulmonary fibrosis, indicating that mTOR inhibition suppressed EMT in vivo. In the setting of transforming growth factor (TGF)-β1-induced EMT in AECs, we found that mTOR inhibitor attenuated TGF-β1-induced EMT in AECs. This EMT was characterized by morphology and cell skeleton changes and the expression of EMT phenotype markers. Finally, mTOR blockade decreased S6k and TGF-β1-induced Smad2/3 phosphorylation. Bleomycin induced pulmonary fibrosis and EMT in mice, while mTOR repression inhibited bleomycin-induced pulmonary fibrosis and attenuated EMT in vivo. Hence, our study provided evidence of a novel mechanism by which mTOR inhibitor ameliorates pulmonary fibrosis. Suppression of mTOR and EMT may be a target for treatment of pulmonary fibrosis.

Epithelial-mesenchymal transition leads to NK cell-mediated metastasis-specific immunosurveillance in lung cancer

During epithelial-mesenchymal transition (EMT) epithelial cancer cells transdifferentiate into highly motile, invasive, mesenchymal-like cells, giving rise to disseminating tumor cells. Few of these disseminated cells successfully metastasize. Immune cells and inflammation in the tumor microenvironment were shown to drive EMT, but few studies investigated the consequences of EMT for tumor immunosurveillance. In addition to initiating metastasis, we demonstrate that EMT confers increased susceptibility to natural killer (NK) cells and contributes, in part, to the inefficiency of the metastatic process. Depletion of NK cells allowed spontaneous metastasis without affecting primary tumor growth. EMT-induced modulation of E-cadherin and cell adhesion molecule 1 (CADM1) mediated increased susceptibility to NK cytotoxicity. Higher CADM1 expression correlates with improved patient survival in 2 lung and 1 breast adenocarcinoma patient cohorts and decreased metastasis. Our observations reveal a novel NK-mediated, metastasis-specific immunosurveillance in lung cancer and present a window of opportunity for preventing metastasis by boosting NK cell activity.

Phthalazinone Pyrazole Enhances the Hepatic Functions of Human Embryonic Stem Cell-Derived Hepatocyte-Like Cells via Suppression of the Epithelial-Mesenchymal Transition

During liver development, nonpolarized hepatic progenitor cells differentiate into mature hepatocytes with distinct polarity. This polarity is essential for maintaining the intrinsic properties of hepatocytes. The balance between the epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET) plays a decisive role in differentiation of polarized hepatocytes. In this study, we found that phthalazinone pyrazole (PP), a selective inhibitor of Aurora-A kinase (Aurora-A), suppressed the EMT during the differentiation of hepatocyte-like cells (HLCs) from human embryonic stem cells. The differentiated HLCs treated with PP at the hepatoblast stage showed enhanced hepatic morphology and functions, particularly with regard to the expression of drug metabolizing enzymes. Moreover, we found that these effects were mediated though suppression of the AKT pathway, which is involved in induction of the EMT, and upregulation of hepatocyte nuclear factor 4α expression rather than Aurora-A inhibition. In conclusion, these findings provided insights into the regulatory role of the EMT on in vitro hepatic maturation, suggesting that inhibition of the EMT may drive transformation of hepatoblast cells into mature and polarized HLCs.

Effect of Trichostatin A on radiation induced epithelial-mesenchymal transition in A549 cells

Radiotherapy is used to treat tumors of different origins and nature, but often lead to development of radioresistance and metastasis of cells. Interestingly, radiation induces epithelial-mesenchymal transition (EMT), a process by which epithelial cells undergo mesenchymal phenotype and stimulates tumor progression capability. Our study investigated the effect of Trichostatin A (TSA), a natural derivate isolated from Streptomyces, upon radiation-induced lung EMT and we tried to understand the role of signaling molecules in irradiated lung cancer cells (A549). The cells were categorized into four groups: untreated control, radiation alone (R; 8Gy, X-ray), radiation combined with TSA (R + T) and TSA (100nM). Radiation-induced lung EMT were evidenced by decreased expression of epithelial marker like E-cadherin, Zona occluden1 (ZO-1) and increased expression of N-cadherin and Vimentin. The Snail protein, a master regulator of EMT, was observed to be elevated after radiation treatment. In addition, TGF-β1 signaling (smad2, 3, and 4) proteins were activated upon irradiation. Western blot data were supported by the altered m-RNA expression of E-cadherin, TGF-β and Snail genes and this effect were reversed by TSA treatment. In addition to this, as supportive evidence, we performed docking studies between snail protein and TSA using Auto docking software and results suggested that less binding energy was needed for the putative binding of TSA on C-terminal domain of Snail protein. Based on our report, we suggest that TSA can effectively inhibit radiation-induced EMT (i) by altering epithelial and mesenchymal markers (ii) by modulating signaling molecules of TGFβ1 pathway (iii) by inhibiting cancer cell migratory potential in A549 cells (iv)by effectively binding to Snail which is an enhancer of EMT.

Epithelial-to-Mesenchymal Transition and MicroRNAs in Lung Cancer

Despite major advances, non-small cell lung cancer (NSCLC) remains the major cause of cancer-related death in developed countries. Metastasis and drug resistance are the main factors contributing to relapse and death. Epithelial-to-mesenchymal transition (EMT) is a complex molecular and cellular process involved in tissue remodelling that was extensively studied as an actor of tumour progression, metastasis and drug resistance in many cancer types and in lung cancers. Here we described with an emphasis on NSCLC how the changes in signalling pathways, transcription factors expression or microRNAs that occur in cancer promote EMT. Understanding the biology of EMT will help to define reversing process and treatment strategies. We will see that this complex mechanism is related to inflammation, cell mobility and stem cell features and that it is a dynamic process. The existence of intermediate phenotypes and tumour heterogeneity may be debated in the literature concerning EMT markers, EMT signatures and clinical consequences in NSCLC. However, given the role of EMT in metastasis and in drug resistance the development of EMT inhibitors is an interesting approach to counteract tumour progression and drug resistance. This review describes EMT involvement in cancer with an emphasis on NSCLC and microRNA regulation.

FSIP1 binds HER2 directly to regulate breast cancer growth and invasiveness

Fibrous sheath interacting protein 1 (FSIP1), a spermatogenesis-related testicular antigen, is expressed in abundance in breast cancers, particularly in those overexpressing human epidermal growth factor receptor 2 (HER2); however, little is known about its role in regulating the growth and metastasis of breast cancer cells. We and others have shown previously that FSIP1 expression in breast cancer correlates positively with HER2-positivity, recurrence, and metastases and negatively with survival. Here, using coimmunoprecipitation and microscale thermophoresis, we find that FSIP1 binds to the intracellular domain of HER2 directly. We further show that shRNA-induced FSIP1 knockdown in SKBR3 and MCF-7 breast cancer cells inhibits proliferation, stimulates apoptosis, attenuates epithelial-mesenchymal transition, and impairs migration and invasiveness. Consistent with reduced proliferation and enhanced apoptosis, xenotransplantation of SKBR3 cells stably transfected with sh-FSIP1 into nu/nu mice results in reduced tumor volumes compared with sh-NC transplants. Furthermore, Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) mapping using sh-FSIP1 gene signature yielded associations with extracellular matrix protein pathways, and a reduction in SNAI2 protein expression was confirmed on Western blot analysis. Complementarily, interrogation of the Connectivity Map using the same gene signature yielded, as top hits, chemicals known to inhibit epithelial-mesenchymal transition, including rapamycin, 17-N-allylamino-17-demethoxygeldanamycin, and LY294002. These compounds phenocopy the effects of sh-FSIP1 on SKBR3 cell viability. Thus, FSIP1 suppression limits oncogenesis and invasiveness in breast cancer cells and, considering its absence in most other tissues, including normal breast, may become a potential target for breast cancer therapy.

Therapeutic Targeting of Epithelial Plasticity Programs: Focus on the Epithelial-Mesenchymal Transition

Mounting data points to epithelial plasticity programs such as the epithelial-mesenchymal transition (EMT) as clinically relevant therapeutic targets for the treatment of malignant tumors. In addition to the widely realized role of EMT in increasing cancer cell invasiveness during cancer metastasis, the EMT has also been implicated in allowing cancer cells to avoid tumor suppressor pathways during early tumorigenesis. In addition, data linking EMT to innate and acquired treatment resistance further points towards the desire to develop pharmacological therapies to target epithelial plasticity in cancer. In this review we organized our discussion on pathways and agents that can be used to target the EMT in cancer into 3 groups: (1) extracellular inducers of EMT, (2) the transcription factors that orchestrate the EMT transcriptome, and (3) the downstream effectors of EMT. We highlight only briefly specific canonical pathways known to be involved in EMT, such as the signal transduction pathways TGFβ, EFGR, and Axl-Gas6. We emphasize in more detail pathways that we believe are emerging novel pathways and therapeutic targets such as epigenetic therapies, glycosylation pathways, and immunotherapy. The heterogeneity of tumors and the dynamic nature of epithelial plasticity in cancer cells make it likely that targeting only 1 EMT-related process will be unsuccessful or only transiently successful. We suggest that with greater understanding of epithelial plasticity regulation, such as with the EMT, a more systematic targeting of multiple EMT regulatory networks will be the best path forward to improve cancer outcomes.

Extracellular heat shock protein 90 binding to TGFβ receptor I participates in TGFβ-mediated collagen production in myocardial fibroblasts

The pathological remodeling heart shows an increase in left ventricular mass and an excess of extracellular matrix deposition that can over time cause heart failure. Transforming growth factor β (TGFβ) is the main cytokine controlling this process. The molecular chaperone heat shock protein 90 (Hsp90) has been shown to play a critical role in TGFβ signaling by stabilizing the TGFβ signaling cascade. We detected extracellular Hsp90 in complex with TGFβ receptor I (TGFβRI) in fibroblasts and determined a close proximity between both proteins suggesting a potential physical interaction between the two at the plasma membrane. This was supported by in silico studies predicting Hsp90 dimers and TGFβRI extracellular domain interaction. Both, Hsp90aa1 and Hsp90ab1 isoforms participate in TGFβRI complex. Extracellular Hsp90 inhibition lessened the yield of collagen production as well as the canonical TGFβ signaling cascade, and collagen protein synthesis was drastically reduced in Hsp90aa1 KO mice. These observations together with the significant increase in activity of Hsp90 at the plasma membrane pointed to a functional cooperative partnership between Hsp90 and TGFβRI in the fibrotic process. We propose that a surface population of Hsp90 extracellularly binds TGFβRI and this complex behaves as an active participant in collagen production in TGFβ-activated fibroblasts. We also offer an in vivo insight into the role of Hsp90 and its isoforms during cardiac remodeling in murine aortic banding model suffering from pathological cardiac remodeling and detect circulating Hsp90 overexpressed in remodeling mice.

A gene-signature progression approach to identifying candidate small-molecule cancer therapeutics with connectivity mapping

Background

Gene expression connectivity mapping has gained much popularity recently with a number of successful applications in biomedical research testifying its utility and promise. Previously methodological research in connectivity mapping mainly focused on two of the key components in the framework, namely, the reference gene expression profiles and the connectivity mapping algorithms. The other key component in this framework, the query gene signature, has been left to users to construct without much consensus on how this should be done, albeit it has been an issue most relevant to end users. As a key input to the connectivity mapping process, gene signature is crucially important in returning biologically meaningful and relevant results. This paper intends to formulate a standardized procedure for constructing high quality gene signatures from a user’s perspective.

Results

We describe a two-stage process for making quality gene signatures using gene expression data as initial inputs. First, a differential gene expression analysis comparing two distinct biological states; only the genes that have passed stringent statistical criteria are considered in the second stage of the process, which involves ranking genes based on statistical as well as biological significance. We introduce a “gene signature progression” method as a standard procedure in connectivity mapping. Starting from the highest ranked gene, we progressively determine the minimum length of the gene signature that allows connections to the reference profiles (drugs) being established with a preset target false discovery rate. We use a lung cancer dataset and a breast cancer dataset as two case studies to demonstrate how this standardized procedure works, and we show that highly relevant and interesting biological connections are returned. Of particular note is gefitinib, identified as among the candidate therapeutics in our lung cancer case study. Our gene signature was based on gene expression data from Taiwan female non-smoker lung cancer patients, while there is evidence from independent studies that gefitinib is highly effective in treating women, non-smoker or former light smoker, advanced non-small cell lung cancer patients of Asian origin.

Conclusions

In summary, we introduced a gene signature progression method into connectivity mapping, which enables a standardized procedure for constructing high quality gene signatures. This progression method is particularly useful when the number of differentially expressed genes identified is large, and when there is a need to prioritize them to be included in the query signature. The results from two case studies demonstrate that the approach we have developed is capable of obtaining pertinent candidate drugs with high precision.

Electronic supplementary material

The online version of this article (doi:10.1186/s12859-016-1066-x) contains supplementary material, which is available to authorized users.

Epithelial-mesenchymal plasticity of breast cancer stem cells: implications for metastasis and therapeutic resistance

Over the past several decades the traditional view of cancer being a homogeneous mass of rapid proliferating malignant cells is being replaced by a model of ever increasing complexity, which points out that cancers are complex tissues composed of multiple cell types. A large variety of immune and other host cells constitute the tumor microenvironment, which supports the growth and progression of the tumor where individual cancer cells evolve with increasing phenotypic and genetic heterogeneity. Furthermore, it has also become clear that, in addition to this cellular and genetic heterogeneity, most tumors exhibit a hierarchical organization composed of tumor cells displaying divergent lineage markers and at the apex of this hierarchy are cells capable of self-renewal. These "cancer stem cells" not only drive tumor growth, but also mediate metastasis and contribute to treatment resistance. Besides displaying remarkable genetic and phenotypic heterogeneity, cancer stem cells maintain plasticity to transition between mesenchymal-like (EMT) and epithelial-like (MET) states in a process regulated by the tumor microenvironment. These stem cell state transitions may play a fundamental role in the process of tumor metastasis. In this review, we will discuss emerging knowledge regarding the plasticity of cancer stem cells and the role that this plasticity plays in tumor metastasis. We also discuss the implications of these findings for the development of cancer stem cell targeted therapeutics.

Epithelial to Mesenchymal Transition in a Clinical Perspective

Tumor growth and metastatic dissemination rely on cellular plasticity. Among the different phenotypes acquired by cancer cells, epithelial to mesenchymal transition (EMT) has been extensively illustrated. Indeed, this transition allows an epithelial polarized cell to acquire a more mesenchymal phenotype with increased mobility and invasiveness. The role of EMT is quite clear during developmental stage. In the neoplastic context in many tumors EMT has been associated with a more aggressive tumor phenotype including local invasion and distant metastasis. EMT allows the cell to invade surrounding tissues and survive in the general circulation and through a stem cell phenotype grown in the host organ. The molecular pathways underlying EMT have also been clearly defined and their description is beyond the scope of this review. Here we will summarize and analyze the attempts made to block EMT in the therapeutic context. Indeed, till today, most of the studies are made in animal models. Few clinical trials are ongoing with no obvious benefits of EMT inhibitors yet. We point out the limitations of EMT targeting such tumor heterogeneity or the dynamics of EMT during disease progression.

Regulation of complement-dependent cytotoxicity by TGF-β-induced epithelial-mesenchymal transition

The process of Epithelial-mesenchymal transition (EMT), in addition to being an initiating event for tumor metastasis, is implicated in conferring several clinically relevant properties to disseminating cancer cells. These include stem cell like properties, resistance to targeted therapies and ability to evade immune surveillance. Enrichment analysis of gene expression changes during TGF-β induced EMT in lung cancer cells identified complement cascade as one of the significantly enriched pathway. Further analysis of the genes in the complement pathway revealed an increase in the expression of complement inhibitors and a decrease in the expression of proteins essential for complement activity. In this study, we tested whether EMT confers resistance to complement-dependent cytotoxicity (CDC) in lung cancer cells and promotes tumor progression. CD59 is a potent inhibitor of membrane attack complex that mediates complement-dependent cell lysis. We observed a significant increase in the CD59 expression on the surface of cells after TGF-β-induced EMT. Furthermore, CD59 knock down restored susceptibility of cells undergoing EMT to Cetuximab-mediated CDC. TGF-β-induced CD59 expression during EMT is dependent on Smad3 but not Smad2. ChIP analysis confirmed that Smad3 directly binds to the CD59 promoter. Stable knock-down of CD59 in A549 cells inhibited experimental metastasis. These results demonstrate that TGF-β-induced EMT and CD59 expression confers an immune evasive mechanism to disseminating tumor cells facilitating tumor progression. Together, our data demonstrates that CD59 inhibition may serve as an adjuvant to enhance the efficacy of antibody-mediated therapies, as well as to inhibit metastasis in lung cancer.

Epithelial-mesenchymal transition in colorectal cancer metastasis: A system review

Tumor metastasis is a multi-step process by which tumor cells disseminate from their primary site and form secondary tumors at a distant site. And metastasis is the major cause of death in the vast majority of cancer patients. However, the mechanisms underlying each step remain obscure. In the past decade, a developmental program epithelial-to-mesenchymal transition (EMT) has been increasingly recognized to play pivotal and intricate roles in promoting carcinoma invasion and metastasis. The EMT process is very complex and controlled by various families of transcriptional regulators through different signaling pathways. In this system review, we focus on the molecular network of the EMT program and its malignant phenotypes associated with metastasis in colorectal cancer (CRC), including cancer stem cells, tumor budding, circulating tumor cells and drug resistance. A better understanding of the molecular regulation of the dynamic EMT program during tumor metastasis will help to provide much-needed therapeutic interventions to target this program when treating metastatic CRC.

The emerging molecular machinery and therapeutic targets of metastasis

Metastasis is a 100-year-old research topic. Technological advances during the past few decades have led to significant progress in our understanding of metastatic disease. However, metastasis remains the leading cause of cancer-related mortalities. The lack of appropriate clinical trials for metastasis preventive drugs and incomplete understanding of the molecular machinery are major obstacles in metastasis prevention and treatment. Numerous processes, factors, and signaling pathways are involved in regulating metastasis. Here we discuss recent progress in metastasis research, including epithelial-mesenchymal plasticity, cancer stem cells, emerging molecular determinants and therapeutic targets, and the link between metastasis and therapy resistance.

Involvement of YAP, TAZ and HSP90 in contact guidance and intercellular junction formation in corneal epithelial cells

The extracellular environment possesses a rich milieu of biophysical and biochemical signaling cues that are simultaneously integrated by cells and influence cellular phenotype. Yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (WWTR1; TAZ), two important signaling molecules of the Hippo pathway, have been recently implicated as nuclear relays of cytoskeletal changes mediated by substratum rigidity and topography. These proteins intersect with other important intracellular signaling pathways (e.g. Wnt and TGFβ). In the cornea, epithelial cells adhere to the stroma through a 3-dimensional topography-rich basement membrane, with features in the nano-submicron size-scale that are capable of profoundly modulating a wide range of fundamental cell behaviors. The influences of substratum-topography, YAP/TAZ knockdown, and HSP90 inhibition on cell morphology, YAP/TAZ localization, and the expression of TGFβ2 and CTGF, were investigated. The results demonstrate (a) that knockdown of TAZ enhances contact guidance in a YAP dependent manner, (b) that CTGF is predominantly regulated by YAP and not TAZ, and (c) that TGFβ2 is regulated by both YAP and TAZ in these cells. Additionally, inhibition of HSP90 resulted in nuclear localization and subsequent transcriptional-activation of YAP, formation of cell-cell junctions and co-localization of E-cadherin and β-catenin at adherens junctions. Results presented in this study reflect the complexities underlying the molecular relationships between the cytoskeleton, growth factors, heat shock proteins, and co-activators of transcription that impact mechanotransduction. The data reveal the importance of YAP/TAZ on the cell behaviors, and gene and protein expression.

Screening of alternative drugs to the tumor suppressor miR-375 in esophageal squamous cell carcinoma using the connectivity map

OBJECTIVE

The aim of this study was to identify alternative compounds to the tumor suppressor miR-375 using the connectivity map (CMAP) and to validate the antitumor effects of the identified drugs in esophageal squamous cell carcinoma (ESCC).

METHODS

Gene profiling of miR-375-treated TE2 and T.Tn cells was applied in order to search the CMAP database. Among the compounds identified using the CMAP, we focused on 8 drugs [(-)-epigallocatechin-3-gallate, metformin, rosiglitazone among others], excluding 2 drugs among the top 10 compounds. We evaluated whether these compounds possess tumor-suppressive functions in ESCC.

RESULTS

A cytotoxicity assay showed that the sensitivity of TE2 and T.Tn cells treated with the 8 compounds was evaluated based on IC50 values of 42.9 µM to 3.8 mM. A cell cycle analysis revealed that the percentage of TE2 and T.Tn cells incubated with 6 compounds in the G0/G1 phase or the G2/M phase increased by approximately 40-80%. A TUNEL assay showed that the percentages of apoptotic cells treated with almost all compounds were significantly increased (p < 0.05) compared with the control cells.

CONCLUSION

The CMAP database is a useful tool for identifying compounds affecting the same molecular pathways, particularly products that are difficult to apply via practical approaches, such as microRNAs.

Epithelial-mesenchymal transition-associated secretory phenotype predicts survival in lung cancer patients

In cancer cells, the process of epithelial-mesenchymal transition (EMT) confers migratory and invasive capacity, resistance to apoptosis, drug resistance, evasion of host immune surveillance and tumor stem cell traits. Cells undergoing EMT may represent tumor cells with metastatic potential. Characterizing the EMT secretome may identify biomarkers to monitor EMT in tumor progression and provide a prognostic signature to predict patient survival. Utilizing a transforming growth factor-β-induced cell culture model of EMT, we quantitatively profiled differentially secreted proteins, by GeLC-tandem mass spectrometry. Integrating with the corresponding transcriptome, we derived an EMT-associated secretory phenotype (EASP) comprising of proteins that were differentially upregulated both at protein and mRNA levels. Four independent primary tumor-derived gene expression data sets of lung cancers were used for survival analysis by the random survival forests (RSF) method. Analysis of 97-gene EASP expression in human lung adenocarcinoma tumors revealed strong positive correlations with lymph node metastasis, advanced tumor stage and histological grade. RSF analysis built on a training set (n = 442), including age, sex and stage as variables, stratified three independent lung cancer data sets into low-, medium- and high-risk groups with significant differences in overall survival. We further refined EASP to a 20 gene signature (rEASP) based on variable importance scores from RSF analysis. Similar to EASP, rEASP predicted survival of both adenocarcinoma and squamous carcinoma patients. More importantly, it predicted survival in the early-stage cancers. These results demonstrate that integrative analysis of the critical biological process of EMT provides mechanism-based and clinically relevant biomarkers with significant prognostic value.

Epithelial-mesenchymal plasticity in carcinoma metastasis

Tumor metastasis is a multistep process by which tumor cells disseminate from their primary site and form secondary tumors at a distant site. Metastasis occurs through a series of steps: local invasion, intravasation, transport, extravasation, and colonization. A developmental program termed epithelial-mesenchymal transition (EMT) has been shown to play a critical role in promoting metastasis in epithelium-derived carcinoma. Recent experimental and clinical studies have improved our knowledge of this dynamic program and implicated EMT and its reverse program, mesenchymal-epithelial transition (MET), in the metastatic process. Here, we review the functional requirement of EMT and/or MET during the individual steps of tumor metastasis and discuss the potential of targeting this program when treating metastatic diseases.

BRCA-Monet: a breast cancer specific drug treatment mode-of-action network for treatment effective prediction using large scale microarray database

BACKGROUND

Connectivity map (cMap) is a recent developed dataset and algorithm for uncovering and understanding the treatment effect of small molecules on different cancer cell lines. It is widely used but there are still remaining challenges for accurate predictions.

METHOD

Here, we propose BRCA-MoNet, a network of drug mode of action (MoA) specific to breast cancer, which is constructed based on the cMap dataset. A drug signature selection algorithm fitting the characteristic of cMap data, a quality control scheme as well as a novel query algorithm based on BRCA-MoNet are developed for more effective prediction of drug effects.

RESULT

BRCA-MoNet was applied to three independent data sets obtained from the GEO database: Estrodial treated MCF7 cell line, BMS-754807 treated MCF7 cell line, and a breast cancer patient microarray dataset. In the first case, BRCA-MoNet could identify drug MoAs likely to share same and reverse treatment effect. In the second case, the result demonstrated the potential of BRCA-MoNet to reposition drugs and predict treatment effects for drugs not in cMap data. In the third case, a possible procedure of personalized drug selection is showcased.

CONCLUSIONS

The results clearly demonstrated that the proposed BRCA-MoNet approach can provide increased prediction power to cMap and thus will be useful for identification of new therapeutic candidates.

Strategies and challenges for systematically mapping biologically significant molecular pathways regulating carcinoma epithelial-mesenchymal transition

Enormous progress has been made towards understanding the role of specific factors in the process of epithelial-mesenchymal transition (EMT); however, the complex underlying pathways and the transient nature of the transition continues to present significant challenges. Targeting tumour cell plasticity underpinning EMT is an attractive strategy to combat metastasis. Global gene expression profiling and high-content analyses are among the strategies employed to identify novel EMT regulators. In this review, we highlight several approaches to systematically interrogate key pathways involved in EMT, with particular emphasis on the features of multiparametric, high-content imaging screening strategies that lend themselves to the systematic discovery of highly significant modulators of tumour cell plasticity.

Metformin, at concentrations corresponding to the treatment of diabetes, potentiates the cytotoxic effects of carboplatin in cultures of ovarian cancer cells

The use of the type 2 diabetics drug metformin has been correlated with enhanced progression-free survival in ovarian cancer. The literature has speculated that this enhancement is due to the high concentration of metformin directly causing cancer cell death. However, this explanation does not fit with clinical data reporting that the women exposed to constant micromolar concentrations of metformin, as present in the treatment of diabetes, respond better to chemotherapy. Herein, our aim was to examine whether micromolar concentrations of metformin alone could bring about cancer cell death and whether micromolar metformin could increase the cytotoxic effect of commonly used chemotherapies in A2780 and SKOV3 cell lines and primary cultured cancer cells isolated from the peritoneal fluid of patients with advanced ovarian cancer. Our results in cell lines demonstrate that no significant loss of viability or change in cell cycle was observed with micromolar metformin alone; however, we observed cytotoxicity with micromolar metformin in combination with chemotherapy at concentrations where the chemotherapy alone produced no loss in viability. We demonstrate that previous exposure and maintenance of metformin in conjunction with carboplatin produces a synergistic enhancement in cytotoxicity of A2780 and SKOV3 cells (55% and 43%, respectively). Furthermore, in 5 (44%) of the 11 ovarian cancer primary cultures, micromolar metformin improved the cytotoxic response to carboplatin but not paclitaxel or doxorubicin. In conclusion, we present data that support the need for a clinical study to evaluate the adjuvant maintenance or prescription of currently approved doses of metformin during the chemotherapeutic treatment of ovarian cancer.

Regional differences in susceptibiity of bronchial epithelium to mesenchymal transition and inhibition by the macrolide antibiotic azithromycin

Objective

Dysregulated repair following epithelial injury is a key forerunner of disease in many organs, and the acquisition of a mesenchymal phenotype by the injured epithelial cells (epithelial to mesenchymal transition, EMT) may serve as a source of fibrosis. The macrolide antibiotic azithromycin and the DNA synthesis inhibitor mycophenolate are in clinical use but their mechanism of action remains unknown in post-transplant bronchiolitis obliterans syndrome (BOS). Here we determined if regional variation in the EMT response to TGFβ1 underlies the bronchiolocentric fibrosis leading to BOS and whether EMT could be inhibited by azithromycin or mycophenolate.

Methods/Results

We found that small and large airway epithelial cells from stable lung transplant patients underwent EMT when stimulated with TGFβ1, however mesenchymal protein expression was higher and loss of epithelial protein expression more complete in small airway epithelial cells. This regional difference was not mediated by changes in expression of the TGFβRII or Smad3 activation. Azithromycin potentially inhibited EMT in both small and large airway epithelial cells by inhibiting Smad3 expression, but not activation.

Conclusion

Collectively, these observations provide a biologic basis for a previously unexplained but widely observed clinical phenomena, and a platform for the development of new approaches to fibrotic diseases.

Hsp90 inhibitors and drug resistance in cancer: the potential benefits of combination therapies of Hsp90 inhibitors and other anti-cancer drugs

Hsp90 is a chaperone protein that interacts with client proteins that are known to be in the cell cycle, signaling and chromatin-remodeling pathways. Hsp90 inhibitors act additively or synergistically with many other drugs in the treatment of both solid tumors and leukemias in murine tumor models and humans. Hsp90 inhibitors potentiate the actions of anti-cancer drugs that target Hsp90 client proteins, including trastuzumab (Herceptin™) which targets Her2/Erb2B, as Hsp90 inhibition elicits the drug effects in cancer cell lines that are otherwise resistant to the drug. A phase II study of the Hsp90 inhibitor 17-AAG and trastuzumab showed that this combination therapy has anticancer activity in patients with HER2-positive metastatic breast cancer progressing on trastuzumab. In this review, we discuss the results of Hsp90 inhibitors in combination with trastuzumab and other cancer drugs. We also discuss recent results from yeast focused on the genetics of drug resistance when Hsp90 is inhibited and the implications that this might have in understanding the effects of genetic variation in treating cancer in humans.