Acquisition of epithelial-mesenchymal transition phenotype of gemcitabine-resistant pancreatic cancer cells is linked with activation of the notch signaling pathway

Aggressive serous epithelial ovarian cancer is potentially propagated by EpCAM+CD45+ phenotype

Epithelial ovarian carcinoma (EOC) patients often acquire resistance against common chemotherapeutic drugs like paclitaxel and cisplatin. The mechanism responsible for the same is ambiguous. We have identified a putative drug-resistant tumour cell phenotype (EpCAM⁺CD45⁺) in the ascitic fluid of EOC patients, which appears to originate from the primary tumour. These cells represent the major tumour burden and are more drug resistant compared to EpCAM⁺ tumour cells due to the over-expression of SIRT1, ABCA1 and BCL2 genes. We have found that the entire EpCAM⁺CD45⁺ population is highly invasive with signature mesenchymal gene expression and also consists of subpopulations of ovarian cancer stem cells (CD133⁺ and CD117⁺CD44⁺). Additionally, we demonstrate that the EpCAM⁺CD45⁺ tumour cells over-express major histocompatibility complex class I antigen, which enable them to evade the natural killer cell-mediated immune surveillance. Preliminary evidence obtained in OVCAR-5 cells suggests that exosomes, secreted by non-tumour cells of the ascitic fluid, play an important role in rendering drug resistance and invasive properties to the cancer cells. Identification of such aggressive tumour cells and deciphering their origin is important for designing better drug targets for EOC.

Microfluidic co-culture of pancreatic tumor spheroids with stellate cells as a novel 3D model for investigation of stroma-mediated cell motility and drug resistance

BACKGROUND

Pancreatic stellate cells (PSCs), a major component of the tumor microenvironment in pancreatic cancer, play roles in cancer progression as well as drug resistance. Culturing various cells in microfluidic (microchannel) devices has proven to be a useful in studying cellular interactions and drug sensitivity. Here we present a microchannel plate-based co-culture model that integrates tumor spheroids with PSCs in a three-dimensional (3D) collagen matrix to mimic the tumor microenvironment in vivo by recapitulating epithelial-mesenchymal transition and chemoresistance.

METHODS

A 7-channel microchannel plate was prepared using poly-dimethylsiloxane (PDMS) via soft lithography. PANC-1, a human pancreatic cancer cell line, and PSCs, each within a designated channel of the microchannel plate, were cultured embedded in type I collagen. Expression of EMT-related markers and factors was analyzed using immunofluorescent staining or Proteome analysis. Changes in viability following exposure to gemcitabine and paclitaxel were measured using Live/Dead assay.

RESULTS

PANC-1 cells formed 3D tumor spheroids within 5 days and the number of spheroids increased when co-cultured with PSCs. Culture conditions were optimized for PANC-1 cells and PSCs, and their appropriate interaction was confirmed by reciprocal activation shown as increased cell motility. PSCs under co-culture showed an increased expression of α-SMA. Expression of EMT-related markers, such as vimentin and TGF-β, was higher in co-cultured PANC-1 spheroids compared to that in mono-cultured spheroids; as was the expression of many other EMT-related factors including TIMP1 and IL-8. Following gemcitabine exposure, no significant changes in survival were observed. When paclitaxel was combined with gemcitabine, a growth inhibitory advantage was prominent in tumor spheroids, which was accompanied by significant cytotoxicity in PSCs.

CONCLUSIONS

We demonstrated that cancer cells grown as tumor spheroids in a 3D collagen matrix and PSCs co-cultured in sub-millimeter proximity participate in mutual interactions that induce EMT and drug resistance in a microchannel plate. Microfluidic co-culture of pancreatic tumor spheroids with PSCs may serve as a useful model for studying EMT and drug resistance in a clinically relevant manner.

Neuraminidase-1: a novel therapeutic target in multistage tumorigenesis

Several of the growth factors and their receptor tyrosine kinases (RTK) such as epidermal growth factor (EGF), platelet-derived growth factor (PDGF), fibroblast growth factor (FGF), vascular endothelial growth factor (VEGF), nerve growth factor (NGF) and insulin are promising candidate targets for cancer therapy. Indeed, tyrosine kinase inhibitors (TKI) have been developed to target these growth factors and their receptors, and have demonstrated dramatic initial responses in cancer therapy. Yet, most patients ultimately develop TKI drug resistance and relapse. It is essential in the clinical setting that the targeted therapies are to circumvent multistage tumorigenesis, including genetic mutations at the different growth factor receptors, tumor neovascularization, chemoresistance of tumors, immune-mediated tumorigenesis and the development of tissue invasion and metastasis. Here, we identify a novel receptor signaling platform linked to EGF, NGF, insulin and TOLL-like receptor (TLR) activations, all of which are known to play major roles in tumorigenesis. The importance of these findings signify an innovative and promising entirely new targeted therapy for cancer. The role of mammalian neuraminidase-1 (Neu1) in complex with matrix metalloproteinase-9 and G protein-coupled receptor tethered to RTKs and TLRs is identified as a major target in multistage tumorigenesis. Evidence exposing the link connecting growth factor-binding and immune-mediated tumorigenesis to this novel receptor-signaling paradigm will be reviewed in its current relationship to cancer.

Orai1 is critical for Notch-driven aggressiveness under hypoxic conditions in triple-negative breast cancers

It is believed that hypoxia stimulates triple-negative breast cancers (TNBCs) metastasis, which is associated with a poor prognosis. However, the underlying mechanism remains unclear. Here, we demonstrated that hypoxia up-regulates both the levels of Orai1 and Notch1, and the increase in Orai1 is mediated by Notch1 signaling in TNBCs. Functionally, Orai1 caused a sustained elevation of intracellular Ca²⁺ via Store-operated Ca²⁺ entry (SOCE), then activated the calcineurin-nuclear factor of activated T-cell 4 (NFAT4, also named NFATc3) in hypoxic TNBCs. Furthermore, pharmacologic inhibition or gene-silencing studies showed that the aggressiveness mediated by Orai1 during hypoxia is dependent on the Notch1/Orai1/SOCE/NFAT4 signaling. Moreover, Orai1 signaling also mediated hypoxia-induced angiogenesis in TNBCs. Thus, our results revealed a novel role of Orai1 as an inducer of aggression and angiogenesis under hypoxic conditions, and this suggests a novel mechanism of hypoxia-induced invasion. It may be worthwhile to further explore the potential of using Orai1 signaling as new target for anti-tumor therapy in TNBCs.

Crosstalk between the Notch signaling pathway and non-coding RNAs in gastrointestinal cancers

The Notch signaling pathway is one of the main signaling pathways that mediates direct contact between cells, and is essential for normal development. It regulates various cellular processes, including cell proliferation, apoptosis, migration, invasion, angiogenesis and metastasis. It additionally serves an important function in tumor progression. Non-coding RNAs mainly include small microRNAs, long non-coding RNAs and circular RNAs. At present, a large body of literature supports the biological significance of non-coding RNAs in tumor progression. It is also becoming increasingly evident that cross-talk exists between Notch signaling and non-coding RNAs. The present review summarizes the current knowledge of Notch-mediated gastrointestinal cancer cell processes, and the effect of the crosstalk between the three major types of non-coding RNAs and the Notch signaling pathway on the fate of gastrointestinal cancer cells.

Cdc20 overexpression is involved in temozolomide-resistant glioma cells with epithelial-mesenchymal transition

Glioma remains one of the most aggressive and lethal cancers in central nervous system. Temozolomide (TMZ) is the most commonly used chemotherapeutic agent in gliomas. However, therapeutic benefits of TMZ could be very limited and all patients would finally suffer from tumor progression as the tumors develop resistance to TMZ. In this study, we aim to investigate the underlying mechanism of chemoresistance in glioma cell line and to identify whether there is still a close link between epithelial-mesenchymal transition (EMT) and TMZ resistance in gliomas. The real-time RT-PCR and Western blotting were used to measure the expression of EMT markers in TMZ-resistant cells. The migration and invasion assays were conducted to detect the cell motility activity in TMZ-resistant cells. The transfection was used to down-regulate the Cdc20 expression. The student t-test was applied for data analysis. We established stable TMZ-resistant glioma cells and designated as TR. Our results revealed that TR cells exhibited a significantly increased resistance to TMZ compared with their parental cells. Moreover, TMZ-resistant cells had acquired EMT-like changes. For the mechanism study, we measured a significant increased expression of CDC20 and decreased expression of Bim in TR cells. Moreover, upon suppression of CDC20 by shRNA transfection, TR cells underwent a reverse of EMT features. Importantly, knockdown of CDC20 enhanced the drug sensitivity of TR cells to TMZ. Our results suggested that inactivation of CDC20 could contribute to the future therapy that possibly overcomes drug resistance in human cancers.

Alternative polyadenylation of ZEB1 promotes its translation during genotoxic stress in pancreatic cancer cells

Pancreatic ductal adenocarcinoma (PDAC) is characterized by extremely poor prognosis. The standard chemotherapeutic drug, gemcitabine, does not offer significant improvements for PDAC management due to the rapid acquisition of drug resistance by patients. Recent evidence indicates that epithelial-to-mesenchymal transition (EMT) of PDAC cells is strictly associated to early metastasization and resistance to chemotherapy. However, it is not exactly clear how EMT is related to drug resistance or how chemotherapy influences EMT. Herein, we found that ZEB1 is the only EMT-related transcription factor that clearly segregates mesenchymal and epithelial PDAC cell lines. Gemcitabine treatment caused upregulation of ZEB1 protein through post-transcriptional mechanisms in mesenchymal PDAC cells within a context of global inhibition of protein synthesis. The increase in ZEB1 protein correlates with alternative polyadenylation of the transcript, leading to shortening of the 3' untranslated region (UTR) and deletion of binding sites for repressive microRNAs. Polysome profiling indicated that shorter ZEB1 transcripts are specifically retained on the polysomes of PDAC cells during genotoxic stress, while most mRNAs, including longer ZEB1 transcripts, are depleted. Thus, our findings uncover a novel layer of ZEB1 regulation through 3'-end shortening of its transcript and selective association with polysomes under genotoxic stress, strongly suggesting that PDAC cells rely on upregulation of ZEB1 protein expression to withstand hostile environments.

Acquisition of EGFR TKI resistance and EMT phenotype is linked with activation of IGF1R/NF-κB pathway in EGFR-mutant NSCLC

Epithelial-mesenchymal transition (EMT) is clinically associated with acquired resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKI) in non-small cell lung cancers (NSCLC). However, the mechanisms promoting EMT in EGFR TKI-resistant NSCLC have not been fully elucidated. Previous studies have suggested that IGF1R signaling is involved in both acquired EGFR TKI resistance in NSCLC and induction of EMT in some types of tumor. In this study, we further explored the role of the IGF1R signaling in the acquisition of EMT phenotype associated with EGFR TKI resistance in mutant-EGFR NSCLC. Compared to gefitinib-sensitive parental cells, gefitinib-resistant (GR) cells displayed an EMT phenotype associated with increased migration and invasion abilities with the concomitant activation of IGF1R and NF-κB p65 signaling. Inhibition of IGF1R or p65 using pharmacological inhibitor or specific siRNA partially restored sensitivity to gefitinib with the concomitant reversal of EMT in GR cells. Conversely, exogenous IGF1 induced both gefitinib resistance and accompanying EMT in parental cells. We also demonstrated that IGF1R could phosphorylate downstream Akt and Erk to activate NF-κB p65. Taken together, our findings indicate that activation of IGF1R/Akt/Erk/NF-κB signaling is linked to the acquisition of EGFR TKI resistance and EMT phenotype in EGFR-mutant NSCLC and could be a novel therapeutic target for advanced NSCLC.

Targeting epithelial-mesenchymal plasticity in cancer: clinical and preclinical advances in therapy and monitoring

The concept of epithelial-mesenchymal plasticity (EMP), which describes the dynamic flux within the spectrum of phenotypic states that invasive carcinoma cells may reside, is being increasingly recognised for its role in cancer progression and therapy resistance. The myriad of events that are able to induce EMP, as well as the more recently characterised control loops, results in dynamic transitions of cancerous epithelial cells to more mesenchymal-like phenotypes through an epithelial-mesenchymal transition (EMT), as well as the reverse transition from mesenchymal phenotypes to an epithelial one. The significance of EMP, in its ability to drive local invasion, generate cancer stem cells and facilitate metastasis by the dissemination of circulating tumour cells (CTCs), highlights its importance as a targetable programme to combat cancer morbidity and mortality. The focus of this review is to consolidate the existing knowledge on the strategies currently in development to combat cancer progression via inhibition of specific facets of EMP. The prevalence of relapse due to therapy resistance and metastatic propensity that EMP endows should be considered when designing therapy regimes, and such therapies should synergise with existing chemotherapeutics to benefit efficacy. To further improve upon EMP-targeted therapies, it is imperative to devise monitoring strategies to assess the impact of such treatments on EMP-related phenomenon such as CTC burden, chemosensitivity/-resistance and micrometastasis in patients.

EMT and Treatment Resistance in Pancreatic Cancer

Pancreatic cancer (PC) is the third leading cause of adult cancer mortality in the United States. The poor prognosis for patients with PC is mainly due to its aggressive course, the limited efficacy of active systemic treatments, and a metastatic behavior, demonstrated throughout the evolution of the disease. On average, 80% of patients with PC are diagnosed with metastatic disease, and the half of those who undergo surgery and adjuvant therapy develop liver metastasis within two years. Metastatic dissemination is an early event in PC and is mainly attributed to an evolutionary biological process called epithelial-to-mesenchymal transition (EMT). This innate mechanism could have a dual role during embryonic growth and organ differentiation, and in cancer progression, cancer stem cell intravasation, and metastasis settlement. Many of the molecular pathways decisive in EMT progression have been already unraveled, but little is known about the causes behind the induction of this mechanism. EMT is one of the most distinctive and critical features of PC, occurring even in the very first stages of tumor development. This is known as pancreatic intraepithelial neoplasia (PanIN) and leads to early dissemination, drug resistance, and unfavorable prognosis and survival. The intention of this review is to shed new light on the critical role assumed by EMT during PC progression, with a particular focus on its role in PC resistance.

Roles of Long Noncoding RNAs in Recurrence and Metastasis of Radiotherapy-Resistant Cancer Stem Cells

Radiotherapy is a well-established therapeutic regimen applied to treat at least half of all cancer patients worldwide. Radioresistance of cancers or failure to treat certain tumor types with radiation is associated with enhanced local invasion, metastasis and poor prognosis. Elucidation of the biological characteristics underlying radioresistance is therefore critical to ensure the development of effective strategies to resolve this issue, which remains an urgent medical problem. Cancer stem cells (CSCs) comprise a small population of tumor cells that constitute the origin of most cancer cell types. CSCs are virtually resistant to radiotherapy, and consequently contribute to recurrence and disease progression. Metastasis is an increasing problem in resistance to cancer radiotherapy and closely associated with the morbidity and mortality rates of several cancer types. Accumulating evidence has demonstrated that radiation induces epithelial-mesenchymal transition (EMT) accompanied by increased cancer recurrence, metastasis and CSC generation. CSCs are believed to serve as the basis of metastasis. Previous studies indicate that CSCs contribute to the generation of metastasis, either in a direct or indirect manner. Moreover, the heterogeneity of CSCs may be responsible for organ specificity and considerable complexity of metastases. Long noncoding RNAs (lncRNAs) are a class of noncoding molecules over 200 nucleotides in length involved in the initiation and progression of several cancer types. Recently, lncRNAs have attracted considerable attention as novel critical regulators of cancer progression and metastasis. In the current review, we have discussed lncRNA-mediated regulation of CSCs following radiotherapy, their association with tumor metastasis and significance in radioresistance of cancer.

Novel crosstalk between KLF4 and ZEB1 regulates gemcitabine resistance in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignancies with broad resistance to chemotherapeutic drugs. Krüppel-like factor 4 (KLF4) is a candidate tumor suppressor in PDAC. However, the precise role of KLF4 in gemcitabine resistance of PDAC remains largely unclear. In this study, we demonstrated that gemcitabine inhibited KLF4 expression. Moreover, gemcitabine also reduced the levels of miR‑200b and miR‑183, but promoted ZEB1 expression in PDAC cells. KLF4 knockdown blocked the expression of miR‑200b and miR‑183, and inversely, KLF4 overexpression promoted the expression of miR‑200b and miR‑183, suggesting that KLF4 positively regulated the expression of miR‑200b and miR‑183. Moreover, KLF4 knockdown enhanced ZEB1 expression and gemcitabine resistance while KLF4 overexpression induced the opposite effect. ChIP assays verified that KLF4 positively regulated the expression of miR‑200b and miR‑183 by directly binding to their promoters. Then, miR‑200b and miR‑183 directly inhibited ZEB1 expression by targeting its 3'UTR region. ZEB1 knockdown attenuated gemcitabine resistance in PDAC cells. KLF4 overexpression promoted gemcitabine sensitivity of PDAC in vivo by negatively regulating ZEB1 expression. Our results revealed that novel crosstalk between KLF4 and ZEB1 regulated gemcitabine resistance in PDAC.

EGFR-Targeted Cationic Polymeric Mixed Micelles for Codelivery of Gemcitabine and miR-205 for Treating Advanced Pancreatic Cancer

Gemcitabine (GEM), a first-line chemotherapy for pancreatic cancer undergoes rapid metabolism and develops chemoresistance after repeated administration. We previously demonstrated that the combination of GEM and miR-205 provides an effective therapeutic strategy to sensitize GEM-resistant pancreatic cancer cells. Since epidermal growth factor receptor (EGFR) is overexpressed in pancreatic cancer cells, in this study, we aimed to deliver mixed micelles containing GEM and miR-205 decorated with EGFR-targeting cetuximab (C225) monoclonal antibody for targeted therapy. Cetuximab C225 was conjugated to malemido-poly(ethylene glycol)-block-poly(2-methyl-2-carboxyl-propylene carbonate-graft-dodecanol (C225-PEG-PCD) to prepare mixed micelles with mPEG-b-PCC-g-GEM-g-DC-g-TEPA for targeted codelivery of GEM and miR-205. This mixed micelle formulation showed a significant enhancement in EGFR-mediated cellular uptake in GEM-resistant MIA PaCa-2^R cells. Further, an enhanced tumor accumulation of C225-micelles conjugated with near-infrared fluorescent Cy7.5 dye and Dy677-labeled miR-205 in orthotopic pancreatic tumor bearing NSG mice was evident after systemic administration. In addition, inhibition of tumor growth was also observed with increased apoptosis and reduced EMT after treatment with C225-micelles containing GEM and miR-205. Therefore, we believe that the targeted delivery of GEM and miR-205 in combination could be a novel strategy for treating advanced pancreatic cancer.

Hippo pathway contributes to cisplatin resistant-induced EMT in nasopharyngeal carcinoma cells

Nasopharyngeal carcinoma (NPC) is a kind of head-neck malignant tumor derived from the nasopharyngeal epithelium and is mainly prevalent in Southern China and Southeast Asia countries. Cisplatin (DDP) provides the first-line therapeutic administration in NPC patients. However, chemoresistance has been a main barrier and caused bad treatment outcome in NPC therapy. To understand the molecular mechanism of acquired resistance to DDP, multiple methods were performed to examine the morphocytology and molecular changes in DDP-resistant NPC cells. We found that drug resistance cells displayed epithelial-mesenchymal transition (EMT) characteristics. DDP-resistant NPC cells exhibited enhanced migration and invasion potential. Moreover, overexpression of TAZ, one key gene in Hippo pathway, is closely associated with the DDP resistance of NPC cells and its EMT properties. Depletion of TAZ in DDP-resistant cells reversed EMT phenotypes to MET characteristics and restored chemosensitivity of DDP-resistant cells to DDP treatment. These results suggest that inactivation of TAZ could be a promising approach for the treatment of NPC patients.

Depleted tumor suppressor miR-107 in plasma relates to tumor progression and is a novel therapeutic target in pancreatic cancer

This study explored decreased tumor suppressor microRNA (miRNA) plasma levels in pancreatic cancer (PCa) patients to clarify their potential as novel biomarkers and therapeutic targets. We used the microRNA array-based approach to select candidates by comparing plasma levels between PCa patients and healthy volunteers. Six down-regulated miRNAs (miR-107, miR-126, miR-451, miR-145, miR-491-5p, and miR-146b-5p) were selected. Small- and large-scale analyses using samples from 100 PCa patients and 80 healthy volunteers revealed that miR-107 was the most down-regulated miRNA in PCa patients compared with healthy volunteers (P < 0.0001; area under the receiver-operating characteristic curve, 0.851). A low miR-107 plasma level was significantly associated with advanced T stage, N stage, and liver metastasis and was an independent factor predicting poor prognosis in PCa patients (P = 0.0424; hazard ratio, 2.95). miR-107 overexpression in PCa cells induced G1/S arrest with the production of p21 and inhibited cell proliferation through the transcriptional regulation of Notch2. In vivo, the restoration and maintenance of the miR-107 plasma level significantly inhibited tumor progression in mice. Depletion of the tumor suppressor miR-107 in plasma relates to tumor progression and poor outcomes. The restoration of the plasma miR-107 level might be a novel anticancer treatment strategy for PCa.

Pancreatic Ductal Adenocarcinoma: Current and Evolving Therapies

Pancreatic ductal adenocarcinoma (PDAC), which constitutes 90% of pancreatic cancers, is the fourth leading cause of cancer-related deaths in the world. Due to the broad heterogeneity of genetic mutations and dense stromal environment, PDAC belongs to one of the most chemoresistant cancers. Most of the available treatments are palliative, with the objective of relieving disease-related symptoms and prolonging survival. Currently, available therapeutic options are surgery, radiation, chemotherapy, immunotherapy, and use of targeted drugs. However, thus far, therapies targeting cancer-associated molecular pathways have not given satisfactory results; this is due in part to the rapid upregulation of compensatory alternative pathways as well as dense desmoplastic reaction. In this review, we summarize currently available therapies and clinical trials, directed towards a plethora of pathways and components dysregulated during PDAC carcinogenesis. Emerging trends towards targeted therapies as the most promising approach will also be discussed.

Phenotypic Plasticity and Cell Fate Decisions in Cancer: Insights from Dynamical Systems Theory

Waddington's epigenetic landscape, a famous metaphor in developmental biology, depicts how a stem cell progresses from an undifferentiated phenotype to a differentiated one. The concept of "landscape" in the context of dynamical systems theory represents a high-dimensional space, in which each cell phenotype is considered as an "attractor" that is determined by interactions between multiple molecular players, and is buffered against environmental fluctuations. In addition, biological noise is thought to play an important role during these cell-fate decisions and in fact controls transitions between different phenotypes. Here, we discuss the phenotypic transitions in cancer from a dynamical systems perspective and invoke the concept of "cancer attractors"-hidden stable states of the underlying regulatory network that are not occupied by normal cells. Phenotypic transitions in cancer occur at varying levels depending on the context. Using epithelial-to-mesenchymal transition (EMT), cancer stem-like properties, metabolic reprogramming and the emergence of therapy resistance as examples, we illustrate how phenotypic plasticity in cancer cells enables them to acquire hybrid phenotypes (such as hybrid epithelial/mesenchymal and hybrid metabolic phenotypes) that tend to be more aggressive and notoriously resilient to therapies such as chemotherapy and androgen-deprivation therapy. Furthermore, we highlight multiple factors that may give rise to phenotypic plasticity in cancer cells, such as (a) multi-stability or oscillatory behaviors governed by underlying regulatory networks involved in cell-fate decisions in cancer cells, and (b) network rewiring due to conformational dynamics of intrinsically disordered proteins (IDPs) that are highly enriched in cancer cells. We conclude by discussing why a therapeutic approach that promotes "recanalization", i.e., the exit from "cancer attractors" and re-entry into "normal attractors", is more likely to succeed rather than a conventional approach that targets individual molecules/pathways.

Repurposing Established Compounds to Target Pancreatic Cancer Stem Cells (CSCs)

The diagnosis of pancreatic ductal adenocarcinoma (PDAC) carries a dismal prognosis, in particular, when patients present with unresectable disease. While significant progress has been made in understanding the biology of PDAC, this knowledge has not translated into a clear clinical benefit and current chemotherapeutic strategies only offer a modest improvement in overall survival. Accordingly, novel approaches are desperately needed. One hypothesis that could—at least in part—explain the desolate response of PDAC to chemotherapy is the so-called cancer stem cell (CSC) concept, which attributes specific traits, such as chemoresistance, metastatic potential and a distinct metabolism to a small cellular subpopulation of the whole tumor. At the same time, however, some of these attributes could make CSCs more permissive for novel therapeutic strategies with compounds that are already in clinical use. Most recently, several publications have tried to enlighten the field with the idea of repurposing established drugs for antineoplastic use. As such, recycling drugs could present an intriguing and fast-track method with new therapeutic paradigms in anti-cancer and anti-CSC treatments. Here, we aim to summarize important aspects and novel findings of this emerging field.

Vasohibin 2 as a potential predictor of aggressive behavior of triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a subtype breast cancer with aggressive behavior, advanced disease status and poor prognosis. Because of the lack of targeting agents and limited therapeutic options, treatment of TNBC remains a great clinical challenge. Vasohibin 2 (VASH2) was previously identified as an angiogenic factor, but its role in TNBC tumorigenesis is unknown. Using quantitative PCR and western blot analyses, we found that VASH2 is overexpressed in TNBC cells and tissues. Knockdown of VASH2 via siRNA inhibited the proliferation of the TNBC cell lines by delaying cell cycle progression and increasing apoptosis. Further analyses showed that the VASH2-mediated increase in the transcription of fibroblast growth factor-2, vascular endothelial growth factor and vasohibin 1 may be the mechanism underlying these effects. Taken together, these data indicate that VASH2 is abnormally expressed in TNBC, indicating a novel and important role for VASH2 in TNBC malignant transformation.

Effects of microRNA-183 on epithelial-mesenchymal transition, proliferation, migration, invasion and apoptosis in human pancreatic cancer SW1900 cells by targeting MTA1

OBJECTIVE

This study aims to explore effects of miR-183 on epithelial-mesenchymal transition (EMT) and invasion by targeting MTA1 in human pancreatic cancer (PC) cells.

METHODS

Totally, 108 PC patients admitted in Wenzhou Central Hospital and Wenzhou People's Hospital, The Dingli Clinical Institute of Wenzhou Medical University from March 2010 to March 2014 were enrolled. qRT-PCR and immunohistochemistry were applied to examine expression of MTA1 mRNA and protein. Samples were divided into 6 groups: blank, NC, miR-183 mimics, miR-183 inhibitors, MTA1-siRNA and miR-183 inhibitors +MTA1-siRNA groups. CCK8 method was employed for determining cell proliferation rate, flow cytometry for cell apoptosis rate, scratch test for cell migration and Transwell assay for cell invasion. qRT-PCR and Western blotting were used to determine expression of MTA1, E-cadherin and Vimentin mRNA and protein.

RESULTS

Positive expression rate of MTA1 was upregulated in PC tissues, and expression of miR-183 and MTA1 was associated with differentiation, migration, tumor size, TNM. The miR-183 mimics and MTA1-siRNA groups showed a decrease in proliferation, migration and invasion, whereas increased apoptosis, in comparison with blank and NC groups, as expression of MTA1 and Vimentin mRNA and protein were reduced, expression of E-cadherin mRNA and protein was elevated. Compared to blank and NC groups, the miR-183 inhibitors group exhibited enhanced proliferation, migration and invasion and inhibited apoptosis; increased expressions of MTA1 and Vimentin mRNA and protein and decreased expressions of E-cadherin mRNA and protein.

CONCLUSION

Our study supported that miR-183 could repress EMT and invasion of human PC cells through inhibition of MTA1 expression.

TAZ overexpression is associated with epithelial-mesenchymal transition in cisplatin-resistant gastric cancer cells

Gastric cancer is one of the common malignant diseases. The poor treatment outcome is mainly due to chemotherapeutic resistance. Therefore, it is important to determine the molecular mechanism of drug resistance in gastric cancer. To explore the mechanisms of cisplatin resistance in gastric cancer cells, several approaches were performed including MTT assay, real-time RT-PCR, western blot analysis, migration and invasion assays, wound healing assay, and transfection. We found that cisplatin-resistant (CR) gastric cancer cells acquired epithelial-mesenchymal transition (EMT) phenotype. The CR cells with EMT features obtained higher migratory and invasive activities. Moreover, we observed that TAZ was highly expressed in CR cells. Consistently, depletion of TAZ caused partial reversal of EMT to MET in CR cells. Our results suggest that TAZ plays a pivotal role in CR-induced EMT. Targeting TAZ could be a potential therapeutic strategy for gastric cancer.

Expression of Notch Gene and Its Impact on Survival of Patients with Resectable Non-small Cell Lung Cancer

BACKGROUND: Notch signaling has been demonstrated to frequently participate in the process of lung carcinogenesis. This study aimed to search Notch expression in non-small cell lung cancer (NSCLC) and its impact on survival.

METHODS: From 2001 to 2011, patients with diagnosis of NSCLC who received surgical resection were included. The expression of Notch gene was assessed by real-time polymerase chain reaction (RT-PCR). Clinical characteristics, histological types, disease stages, and outcomes were analyzed.

RESULTS: Ninety-seven patients with NSCLC being explored the expression of Notch gene (Notch1 - 4). Seventy-five patients (77.3%) were adenocarcinoma. Patients with adenocarcinoma had higher expression of Notch2 than other histology types (p < 0.001). Otherwise, patients with squamous cell carcinoma had relative higher expression of Notch1 and Notch3 expression (p = 0.014 and p = 0.032, respectively). Notch2 expression increased associated with patients with more advanced lung cancer stage. Patients who had cancer recurrence also had higher Notch2 expression (p = 0.008). The patient group with lung adenocarcinoma of both high Notch1 and Notch3 expression had a shorter median disease-free survival (DFS) (both high v.s both low: DFS, median, 7.2 v.s 25.3 months, p = 0.03). However, the expression of Notch gene had no impact on overall survival.

CONCLUSIONS: Patients with lung adenocarcinoma had higher Notch2 expression. Patients with higher Notch2 expression also had higher rate of cancer recurrence. Both higher Notch1 and Notch3 expression was associated with poor prognosis in lung adenocarcinoma.

Characterization of Aurora A and Its Impact on the Effect of Cisplatin-Based Chemotherapy in Patients with Non-Small Cell Lung Cancer

BACKGROUND AND OBJECTIVE: Aurora A, as a member of serine/threonine kinase family and a common characteristic of epithelial cancers, plays a critical role in cell mitosis. However, the clinical significance of Aurora A in non–small cell lung cancer (NSCLC) remains undetermined. METHODS: The expression of Aurora A in NSCLC and paired normal adjacent lung tissues was determined by immunohistochemistry, Western blot, and reverse transcriptase polymerase chain reaction. Receiver operating characteristic (ROC) curve analysis was employed to determine a cutoff score for Aurora A expression in a training set (n = 135). For validation, the ROC-derived cutoff score was subjected to analysis of the association of Aurora A expression with patient outcome and clinicopathological characteristics in a testing set (n = 128) and overall patients (n = 263). The correlation of Aurora A with cisplatin resistance and epithelial-mesenchymal transition (EMT) was examined in vitro in NSCLC cells by overexpression or knockdown of Aurora A. RESULTS: Aurora A expression was significantly upregulated in tumor tissues compared with paired normal tissues (P < .01). The expression of Aurora A was closely associated with clinical stage, lymph node metastasis, and recurrence and was an independent prognostic parameter in multivariate analysis. High level of Aurora A expression predicted poorer overall survival and disease-free survival in NSCLC patients treated with cisplatin-based adjuvant chemotherapy. In vitro data showed that overexpression or knockdown of Aurora A resulted in increased or decreased cellular resistance to cisplatin. Furthermore, inhibition of Aurora A reversed the EMT process. CONCLUSIONS: Aurora A was identified as an inferior prognostic and cisplatin-resistant biomarker in NSCLC patients, which provided potential evidences for therapeutic target and reversing drug resistance.

Baicalein increases cisplatin sensitivity of A549 lung adenocarcinoma cells via PI3K/Akt/NF-κB pathway

Baicalein, a bioactive flavonoid, exhibits anti-inflammatory and anti-cancer activities. However, few studies reported the interaction of baicalein with chemotherapeutic agents. Our study showed that baicalein significantly enhanced the chemosensitivity of cisplatin (CDDP) in vivo and in vitro. We found that A549/CDDP (resistant to CDDP) cells not only acquired epithelial-mesenchymal transition (EMT) phenotype, but also showed increased NF-κB activity compared with A549 cells (sensitive to CDDP). Our study further demonstrated that PI3K/Akt/NF-κB pathway controlled CDDP resistance via EMT and NF-κB-mediated apoptosis. Baicalein significantly suppressed the PI3K/Akt/NF-κB pathway, leading to conversion of EMT to mesenchymal-epithelial transition (MET, the reciprocal mesenchymal to epithelial transition), and inhibition of NF-κB-mediated antiapoptotic proteins in A549/CDDP cells. In conclusion, our study demonstrated that baicalein reversed the resistance of human A549 lung adenocarcinoma cells to cisplatin by inhibiting EMT and attenuating apoptosis via PI3K/Akt/NF-κB pathway.

Activation of Notch pathway is linked with epithelial-mesenchymal transition in prostate cancer cells

Notch signaling has been reported to play an essential role in tumorigenesis. Several studies have suggested that Notch receptors could be oncoproteins or tumor suppressors in different types of human cancers. Emerging evidence has suggested that Notch pathway regulates cell growth, apoptosis, cell cycle, and metastasis. In the current study, we explore whether Notch-1 could regulate the cell invasion and migration as well as EMT (epithelial-mesenchymal transition) in prostate cancer cells. We found that overexpression of Notch-1 enhanced cell migration and invasion in PC-3 cells. However, downregulation of Notch-1 retarded cell migration and invasion in prostate cancer cells. Importantly, we observed that overexpression of Notch-1 led to EMT in PC-3 cells. Notably, we found that EMT-type cells are associated with EMT markers change and cancer stem cell phenotype. Taken together, we concluded that downregulation of Notch-1 could be a promising approach for inhibition of invasion in prostate cancer cells, which could be useful for the treatment of metastatic prostate cancer.

Down-regulation of E-cadherin enhances prostate cancer chemoresistance via Notch signaling

Background

The chemoresistance of prostate cancer (PCa) is invariably associated with the aggressiveness and metastasis of this disease. New emerging evidence indicates that the epithelial-to-mesenchymal transition (EMT) may play pivotal roles in the development of chemoresistance and metastasis. As a hallmark of EMT, E-cadherin is suggested to be a key marker in the development of chemoresistance. However, the molecular mechanisms underlying PCa chemoresistance remain unclear. The current study aimed to explore the association between EMT and chemoresistance in PCa as well as whether changing the expression of E-cadherin would affect PCa chemoresistance.

Methods

Parental PC3 and DU145 cells and their chemoresistant PC3-TxR and DU145-TxR cells were analyzed. PC3-TxR and DU145-TxR cells were transfected with E-cadherin-expressing lentivirus to overexpress E-cadherin; PC3 and DU145 cells were transfected with small interfering RNA to silence E-cadherin. Changes of EMT phenotype-related markers and signaling pathways were assessed by Western blotting and quantitative real-time polymerase chain reaction. Tumor cell migration, invasion, and colony formation were then evaluated by wound healing, transwell, and colony formation assays, respectively. The drug sensitivity was evaluated using MTS assay.

Results

Chemoresistant PC3-TxR and DU145-TxR cells exhibited an invasive and metastatic phenotype that associated with EMT, including the down-regulation of E-cadherin and up-regulation of Vimentin, Snail, and N-cadherin, comparing with that of parental PC3 and DU145 cells. When E-cadherin was overexpressed in PC3-TxR and DU145-TxR cells, the expression of Vimentin and Claudin-1 was down-regulated, and tumor cell migration and invasion were inhibited. In particular, the sensitivity to paclitaxel was reactivated in E-cadherin-overexpressing PC3-TxR and DU145-TxR cells. When E-cadherin expression was silenced in parental PC3 and DU145 cells, the expression of Vimentin and Snail was up-regulated, and, particularly, the sensitivity to paclitaxel was decreased. Interestingly, Notch-1 expression was up-regulated in PC3-TxR and DU145-TxR cells, whereas the E-cadherin expression was down-regulated in these cells comparing with their parental cells. The use of γ-secretase inhibitor, a Notch signaling pathway inhibitor, significantly increased the sensitivity of chemoresistant cells to paclitaxel.

Conclusion

The down-regulation of E-cadherin enhances PCa chemoresistance via Notch signaling, and inhibiting the Notch signaling pathway may reverse PCa chemoresistance.

Bone morphogenetic protein 4 is overexpressed in and promotes migration and invasion of drug-resistant cancer cells

Drug resistance and metastasis significantly hinder chemotherapy and worsen prognoses in cancer. Bone morphogenetic protein 4 (BMP4) belongs to the TGF-β superfamily, has broad biological activities in cell proliferation and cartilage differentiation and is also able to induce migration and invasion. Herein, we investigated the role of BMP4 in the regulation of metastasis in paclitaxel-resistant human esophageal carcinoma EC109 cells (EC109/Taxol) and docetaxel-resistant human gastric cancer MGC803 cells (MGC/Doc). In these drug-resistant cell lines, we found the cell motility was enhanced and BMP4 was up-regulated relative to their respective parental cell lines. Consistent with in vitro assays, migration potential and BMP4 expression were increased in EC109/Taxol nude mice. Furthermore, to address whether BMP4 was required to enhance the metastatic in EC109/Taxol cells, the pharmacological inhibitor of BMP signaling dorsomorphin was used; meanwhile, we found that the migration and invasion abilities were inhibited. Moreover, the canonical Smad signaling pathway was investigated. Overall, our studies demonstrated that BMP4 participates in the regulation of invasion and migration by EC109/Taxol cells, and inhibition of BMP4 may be a novel strategy to interfere with metastasis in cancer therapy.

Molecular alterations contributing to pancreatic cancer chemoresistance

Pancreatic ductal adenocarcinoma (PDAC) is one of the most common causes of cancer-related death all over the world. This disease is difficult to treat and patients have an overall 5-year survival rate of less than 5%. Although two drugs, gemcitabine (GEM) and 5-fluorouracil (5-FU) have been shown to improve the survival rate of patients systematically, they do not increase general survival to a clinically acceptable degree. Lack of ideal clinical response of pancreatic cancer patients to chemotherapy is likely to be due to intrinsic and acquired chemoresistance of tumor cells. Various mechanisms of drug resistance have been investigated in pancreatic cancer, including genetic and epigenetic changes in particular genes or signaling pathways. In addition, evidence suggests that microRNAs (miRNAs) play significant roles as key regulators of gene expression in many cellular processes, including drug resistance. Understanding underlying genes and mechanisms of drug resistance in pancreatic cancer is critical to develop new effective treatments for this deadly disease. This review illustrates the genes and miRNAs involved in resistance to gemcitabine in pancreatic cancer.

A mechanopharmacology approach to overcome chemoresistance in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is a highly chemoresistant malignancy. This chemoresistant phenotype has been historically associated with genetic factors. Major biomedical research efforts were concentrated that resulted in the identification of subtypes characterized by specific genetic lesions and gene expression signatures that suggest important biological differences. However, to date, these distinct differences could not be exploited for therapeutic interventions. Apart from these genetic factors, desmoplasia and tumor microenvironment have been recognized as key contributors to PDAC chemoresistance. However, while several strategies targeting tumor-stroma have been explored including drugs against members of the Hedgehog family, they failed to meet the expectations in the clinical setting. These unsatisfactory clinical results suggest that, an important link between genetics and the influence of tumor microenvironment on PDAC chemoresistance remains to be elucidated. In this respect, mechanobiology is an emerging multidisciplinary field that encompasses cell and developmental biology as well as biophysics and bioengineering. Herein we provide a comprehensive overview of the key players in pancreatic cancer chemoresistance from the perspective of mechanobiology, and discuss novel experimental avenues such as elastic micropillar arrays that could provide fresh insights for the development of mechanobiology-targeted therapeutic approaches (know as mechanopharmacology) to overcome anticancer drug resistance in pancreatic cancer.

Snail-Modulated MicroRNA 493 Forms a Negative Feedback Loop with the Insulin-Like Growth Factor 1 Receptor Pathway and Blocks Tumorigenesis

In this study, we have identified one microRNA, microRNA 493 (miR-493), which could simultaneously and directly regulate multiple genes downstream of the insulin-like growth factor 1 receptor (IGF1R) pathway, including IGF1R, by binding with complementary sequences in the 3' untranslated region (UTR) of mRNAs of IGF1R, insulin receptor substrate 1 (IRS1), and mitogen-activated protein kinase 1 (MAPK1), thereby potentiating their inhibitory function at multiple levels in development and progression of cancers. This binding was further confirmed by pulldown of miR with AGO-2 antibody. Further, results from head and neck samples showed that miR-493 levels were significantly downregulated in tumors, with a concomitant increase in the expression of IGF1R and key downstream effectors. Functional studies from miR-493 overexpression cells and nude-mouse models revealed the tumor suppressor functions of miR-493. Regulation studies revealed that Snail binds to the miR-493 promoter and represses it. We found the existence of a dynamic negative feedback loop in the regulation of IGF1R and miR-493 mediated via Snail. Our study showed that nicotine treatment significantly decreases the levels of miR-493-with a concomitant increase in the levels of Snail-an indication of progression of cells toward tumorigenesis, reestablishing the role of tobacco as a major risk factor for head and neck cancers and elucidating the mechanism behind nicotine-mediated tumorigenesis.

Overcoming treatment resistance in cancer: Current understanding and tactics

Chemotherapy is the standard treatment for many, if not all, metastatic cancers. While chemotherapy is often capable of inducing cell death in tumors leading to shrinkage of the tumor bulk, many patients suffer from recurrence and ultimately death due to resistance. During the last decade, treatment resistance has attracted great attention followed by some seminal discoveries, including sequential mutations, cancer stem cells, and bidirectional inter-conversion of stem and non-stem cancer cell populations. Nevertheless, the successful treatment of cancer will require a considerable refinement of our knowledge concerning treatment resistance. In doing so, we expect that a more informed and refined approach to treat cancer will be developed and this may improve prognosis of cancer patients. In this review, we will discuss the current knowledge concerning the failure of cancer treatments and the potential approaches to overcome therapeutic resistance.

Epithelial-mesenchymal transition in morphogenesis, cancer progression and angiogenesis

All organs consist of an epithelium and an associated mesenchyme, so these epithelial-mesenchymal intercations are among the most important phenomena in nature. The aim of this article is the summarize the common mechanisms involved in the establishment of epithelial mesenchymal transition in three biological processes, namely organogenesis, tumor progression and metastasis, and angiogenesis, apparently independent each from other. A common feature of these processes is the fact that specialized epithelial cells lose their features, including cell adhesion and polarity, reorganize their cytoskeleton, and acquire a mesenchymal morphology and the ability to migrate.

Up-regulation of glycolysis promotes the stemness and EMT phenotypes in gemcitabine-resistant pancreatic cancer cells

Cancer stem cells (CSCs) and epithelial–mesenchymal transition (EMT)‐type cells are considered as underlying causes of chemoresistance, tumour recurrence and metastasis in pancreatic cancer. We aimed to describe the mechanisms – particularly glycolysis – involved in the regulation of the CSC and EMT phenotypes. We used a gemcitabine‐resistant (GR) Patu8988 cell line, which exhibited clear CSC and EMT phenotypes and showed reliance on glycolysis. Inhibition of glycolysis using 2‐deoxy‐D‐glucose (2‐DG) significantly enhanced the cytotoxicity of gemcitabine and inhibited the CSC and EMT phenotypes in GR cells both in vitro and in vivo. Intriguingly, the use of the reactive oxygen species (ROS) scavenger N‐acetylcysteine (NAC) restored the CSC and EMT phenotypes. H₂O₂ produced changes similar to those of 2‐DG, indicating that ROS were involved in the acquired cancer stemness and EMT phenotypes of GR cells. Moreover, doublecortin‐like kinase 1 (DCLK1), a pancreatic CSC marker, was highly expressed and regulated the stemness and EMT phenotypes in GR cell. Both 2‐DG and H₂O₂ treatment suppressed DCLK1 expression, which was also rescued by NAC. Together, these findings revealed that glycolysis promotes the expression of DCLK1 and maintains the CSC and EMT phenotypes via maintenance of low ROS levels in chemoresistant GR cells. The glycolysis‐ROS‐DCLK1 pathway may be potential targets for reversing the malignant behaviour of pancreatic cancer.

Luteolin suppresses gastric cancer progression by reversing epithelial-mesenchymal transition via suppression of the Notch signaling pathway

BACKGROUND

Gastric cancer (GC) is one of the most malignant tumors and the second leading cause of cancer-related deaths in the world. Luteolin, a flavonoid present in many fruits and green plants, suppresses cancer progression. The effects of luteolin on GC cells and their underlying mechanisms remain unclear.

METHODS

Effects of luteolin on cell proliferation, migration, invasion, and apoptosis were examined in vitro and in vivo by cell counting kit-8 (CCK-8), transwell assays, and flow cytometry, respectively. Real-time reverse transcription polymerase chain reaction (RT-PCR) and Western blots were performed to evaluate Notch1 signaling and activation of epithelial-mesenchymal transition (EMT) in GC cells treated with or without luteolin. Immunohistochemistry was performed to examine proliferation and Notch1 expression in xenograft tumors.

RESULTS

Luteolin significantly inhibited cell proliferation, invasion, and migration in a dose-dependent and time-dependent manner and promoted cell apoptosis. Luteolin reversed EMT by shrinking the cytoskeleton and by inducing the expression of epithelial biomarker E-cadherin and downregulating the mesenchymal biomarkers N-cadherin, vimentin and Snail. Furthermore, Notch1 signaling was inhibited by luteolin, and downregulation of Notch1 had similar effects as luteolin treatment on cell proliferation, migration, and apoptosis. In addition, luteolin suppressed tumor growth in vivo. A higher expression of Notch1 correlated with a poor overall survival and a poor time to first progression. Furthermore, co-immunoprecipitation analysis revealed that activated Notch1 and β-catenin formed a complex and regulated cell proliferation, migration, and invasion.

CONCLUSIONS

In this study, GC progression was inhibited by luteolin through suppressing Notch1 signaling and reversing EMT, suggesting that luteolin may serve as an effective anti-tumor drug in GC treatment.

Epigenetics in cancer stem cells

Compelling evidence have demonstrated that bulk tumors can arise from a unique subset of cells commonly termed "cancer stem cells" that has been proposed to be a strong driving force of tumorigenesis and a key mechanism of therapeutic resistance. Recent advances in epigenomics have illuminated key mechanisms by which epigenetic regulation contribute to cancer progression. In this review, we present a discussion of how deregulation of various epigenetic pathways can contribute to cancer initiation and tumorigenesis, particularly with respect to maintenance and survival of cancer stem cells. This information, together with several promising clinical and preclinical trials of epigenetic modulating drugs, offer new possibilities for targeting cancer stem cells as well as improving cancer therapy overall.

Acriflavine Inhibits Acquired Drug Resistance by Blocking the Epithelial-to-Mesenchymal Transition and the Unfolded Protein Response

Epithelial-to-mesenchymal transition (EMT) is linked to tumor invasion, drug resistance and aggressive disease and this is largely dependent on the cell's microenvironment. Acriflavine (ACF) is an old antibacterial drug recently also suggested as anticancer agent and HIF inhibitor. We wanted to study the effect of acriflavine on EMT in different human cancer models. Pancreatic cancer cells (Panc-1) were exposed to TGF-β1 or cobalt chloride (to mimick severe hypoxia) to induce EMT. For our third model we exposed HepG2 liver cancer cells to sorafenib which resulted in development of acquired drug resistance with strong features of EMT and aggressive behavior. These models were morphologically and functionally (invasion assay) characterized. Markers of EMT were determined using qRT-PCR and Western blotting. Transcriptome analysis was performed following gene expression determination and combining the iRegulon tool and Gene Set Enrichment Analysis (GSEA). We made the following observations: (1) acriflavine inhibited EMT based on changes in cell morphology, invasive capacities and markers of EMT (at protein and gene expression level). (2) Transcriptome analysis revealed potent inhibition of ATF4 target genes and of the unfolded protein response. We showed that acriflavine blocked eIF2a phosphorylation and reduced ATF4 translation thereby inhibiting the PERK/eIF2a/ATF4 UPR pathway. (3) ACF restored drug sensitivity of cells that obtained acquired resistance.

CONCLUSIONS

We identified acriflavine as a potent inhibitor of EMT and the UPR, thereby re-sensitizing the cancer cells to antineoplastic drugs.

HMGA2-FOXL2 Axis Regulates Metastases and Epithelial-to-Mesenchymal Transition of Chemoresistant Gastric Cancer

Purpose: Chemoresistance is the main cause of treatment failure in cancer and is associated with distant metastases and epithelial-to-mesenchymal transition (EMT). This study was aimed to explore the mechanism of metastases and EMT in chemoresistant gastric cancer.Experimental Design: A key molecular pathway was identified via gene profiling and a bioinformatic analysis in a chemoresistant gastric cancer model. The roles of FOXL2, HMGA2, and ITGA2 were validated via loss-of-function and gain-of-function experiments in vitro and in an orthotopic gastric cancer animal model. The regulation of FOXL2 by HMGA2 was explored via immunoprecipitation and luciferase reporter assays. The expression of these proteins in gastric cancer tissues was examined by IHC.Results: HMGA2 and FOXL2 directly regulated the metastasis and EMT of chemoresistant gastric cancer. The interaction between HMGA2 and pRb facilitated the transactivation of FOXL2 by E2F1, and ITGA2 was the downstream effector of the HMGA2-FOXL2 pathway. HMGA2, FOXL2, and ITGA2 were associated with the TNM classification and staging of gastric cancer and were increased in metastatic lymph nodes and distant metastases. Increased HMGA2, FOXL2, and ITGA2 levels were associated with reduced overall survival periods of patients with gastric cancer.Conclusions: This study demonstrated that the transactivation of FOXL2 driven by interactions between HMGA2 and pRb might exert critical effects on the metastases and EMT of chemoresistant gastric cancer. Blocking the HMGA2-FOXL2-ITGA2 pathway could serve as a new strategy for gastric cancer treatment. Clin Cancer Res; 23(13); 3461-73. ©2017 AACR.

Gamma secretase inhibitor impairs epithelial-to-mesenchymal transition induced by TGF-β in ovarian tumor cell lines

Ovarian cancer is characterized by being highly metastatic, a feature that represents the main cause of failure of the treatment. This study investigated the effects of γ-secretase inhibition on the TGF-β-induced epithelial-mesenchymal transition (EMT) process in ovarian cancer cell lines. SKOV3 cells incubated in the presence of TGF-β showed morphological and biochemical changes related to EMT, which were blocked by co-stimulation with TGF-β and the γ-secretase inhibitor DAPT. In SKOV3 and IGROV1 cells, the co-stimulation blocked the cadherin switch and the increase in the transcription factors Snail, Slug, Twist and Zeb1 induced by TGF-β. DAPT impaired the translocation of phospho-β-catenin to the inner cell compartment observed in TGF-β-treated cells, but was not able to block the induction at protein level induced by TGF-β. Moreover, the inhibitor blocked the increased cell migration and invasiveness ability of both cell lines induced by TGF-β. Notch target genes (Hes1 and Hey1) were induced by TGF-β, decreased by DAPT treatment and remained low in the presence of both stimuli. However, DAPT alone caused no effects on most of the parameters analyzed. These results demonstrate that the γ-secretase inhibitor used in this study exerted a blockade on TGF-β-induced EMT in ovarian cancer cells.

Epithelial-mesenchymal transition as a therapeutic target for overcoming chemoresistance in pancreatic cancer

Pancreatic cancer has one of the worst prognoses among all cancers due to the late manifestation of identifiable symptoms and high resistance to chemo- and radiation therapies. In recent years, a cancer development phase termed epithelial-mesenchymal transition (EMT) has gained increasing research focus. The process is implicated in tumour metastasis, and emerging evidence suggests EMT also contributes or induces chemoresistance in several cancers. Nevertheless, the applicability of therapeutic targeting of EMT faces many challenges. In this mini-review, we summarise the evidence supporting the role of EMT in pancreatic cancer progression, focusing particularly on its association with chemoresistance.

Regulation of EMT by STAT3 in gastrointestinal cancer (Review)

Gastrointestinal (GI) cancer is characterized by its aggressiveness and tendency to metastasize at early stage. Epithelial-mesenchymal transition (EMT), commonly known as the preparing step of metastasis, may account for the aggressive phenotype of GI cancer cells. The process of EMT is finely orchestrated by multiple layers of regulators. Signal transducer and activator of transcription 3 (STAT3) is a transcription factor constitutively activated in diverse malignancies. Recent studies have suggested an involvement of STAT3 in GI cancer EMT. In this review, we first take an insight into the oncogenic functions of STAT3 in GI cancer, and then summarize the possible mechanisms by which STAT3 regulates the EMT process. Through the extensive interactions with EMT-inducing transcription factors and non-coding RNAs, and crosstalk with other signaling pathways, STAT3 has been demonstrated to promote the mesenchymal and invasive phenotype of GI cancer, which provides rationales for specifically targeting STAT3 to prevent and reverse the progression of GI cancer.

The ERK-ZEB1 pathway mediates epithelial-mesenchymal transition in pemetrexed resistant lung cancer cells with suppression by vinca alkaloids

High thymidylate synthase (TS) level in cancer tissue is considered to result in resistance to pemetrexed therapy for advanced stages of nonsquamous non-small cell lung cancers. To further investigate the mechanism of pemetrexed resistance and potential prognostic outcomes in lung cancer, we established pemetrexed-resistant lung adenocarcinoma cell sublines from CL1 harboring a mutated TP53 gene (R248W) and A549 harboring wild-type TP53. We found the TS expression is upregulated in both pemetrexed-resistant sublines and the reduced TS level achieved through shRNA inhibition resulted in higher pemetrexed sensitivity. We also demonstrated that the acquisitions of pemetrexed resistance enhances epithelial-mesenchymal transition (EMT) in vivo with a mice animal model and in vitro with CL1 and A549 sublines, which was associated with upregulation of ZEB1 which, in turn, downregulates E-cadherin and upregulates fibronectin. When ERK1/2 phosphorylation was reduced by an inhibitor (U0126) or siRNA inhibition, both pemetrexed-resistant sublines reduced their migration and invasion abilities. Therefore, the ERK-mediated pathways induce apoptosis with pemetrexed treatment, and may in turn mediate EMT when cancer cells are resistant to pemetrexed. We further demonstrated that the growth of pemetrexed-resistant tumors could be inhibited by vinblastine in vivo and vincristine in vitro. Our data indicate that pemetrexed resistance could be relieved by non-cross-resistant chemotherapeutic drugs such as vinca alkaloids and might be independent to TP53 status. Furthermore, the phosphorylation of ERK was reduced by vincristine. This finding provides a new insight for overcoming pemetrexed resistance and metastasis by application of vinca alkaloids.

miR-25-3p reverses epithelial-mesenchymal transition via targeting Sema4C in cisplatin-resistance cervical cancer cells

Acquisition of epithelial-mesenchymal transition (EMT) has recently been proposed as an important contributor of drug resistance in cervical cancer cells. However, the underlying mechanisms are still unclear. MicroRNAs play a crucial role in regulating EMT. The aim of this study was to explore the potential role of miR-25-3p in regulating EMT in cisplatin-resistant (CR) cervical cancer cells. To this end, we established stable CR cervical cancer cells, HeLa-CR and CaSki-CR, and investigated the function of miR-25-3p in regulating EMT. It is found that CR cervical cancer cells possessed more EMT characteristics and demonstrated higher migratory abilities and invasiveness. miR-25-3p downregulation was also seen in HeLa-CR and CaSki-CR cells. Of note, ectopic expression of miR-25-3p reversed the EMT phenotype and sensitized CR cells to cisplatin via targeting Sema4C. Furthermore, stable overexpression of miR-25-3p in HeLa-CR cells suppressed tumor growth in mice, downregulated Sema4C and Snail, and upregulated E-cadherin compared with the control group. These results suggest that miR-25-3p is an important regulator of cervical cancer EMT and chemoresistance. Thus, upregulation of miR-25-3p could be a novel approach to treat cervical cancers that are resistant to chemotherapy.

Acriflavine Inhibits Acquired Drug Resistance by Blocking the Epithelial-to-Mesenchymal Transition and the Unfolded Protein Response

Epithelial-to-mesenchymal transition (EMT) is linked to tumor invasion, drug resistance and aggressive disease and this is largely dependent on the cell's microenvironment. Acriflavine (ACF) is an old antibacterial drug recently also suggested as anticancer agent and HIF inhibitor. We wanted to study the effect of acriflavine on EMT in different human cancer models. Pancreatic cancer cells (Panc-1) were exposed to TGF-β1 or cobalt chloride (to mimick severe hypoxia) to induce EMT. For our third model we exposed HepG2 liver cancer cells to sorafenib which resulted in development of acquired drug resistance with strong features of EMT and aggressive behavior. These models were morphologically and functionally (invasion assay) characterized. Markers of EMT were determined using qRT-PCR and Western blotting. Transcriptome analysis was performed following gene expression determination and combining the iRegulon tool and Gene Set Enrichment Analysis (GSEA). We made the following observations: (1) acriflavine inhibited EMT based on changes in cell morphology, invasive capacities and markers of EMT (at protein and gene expression level). (2) Transcriptome analysis revealed potent inhibition of ATF4 target genes and of the unfolded protein response. We showed that acriflavine blocked eIF2a phosphorylation and reduced ATF4 translation thereby inhibiting the PERK/eIF2a/ATF4 UPR pathway. (3) ACF restored drug sensitivity of cells that obtained acquired resistance. Conclusions: We identified acriflavine as a potent inhibitor of EMT and the UPR, thereby re-sensitizing the cancer cells to antineoplastic drugs.

Notch3 inhibits epithelial-mesenchymal transition by activating Kibra-mediated Hippo/YAP signaling in breast cancer epithelial cells

Invasion, metastasis and chemoresistance are leading causes of death in breast cancer patients. A vital change of epithelial cells, epithelial-mesenchymal transition (EMT), is involved in these processes. Unfortunately, the molecular mechanisms controlling EMT remain to be elucidated. Our previous studies have shown that ectopic N3ICD expression inhibits EMT in MDA-MB-231, a triple-negative breast cancer (TNBC) epithelial cell line. To decipher the mechanism, we performed in-depth studies. Specifically, we found that overexpressing N3ICD transcriptionally upregulated the expression of Kibra, an upstream member of the Hippo pathway. Correspondingly, we also observed that phosphorylated Hippo pathway core kinases, including Lats1/2 and MST1/2, were increased and decreased by overexpressing and knocking down Notch3, respectively. Furthermore, we found that the oncogenic transcriptional coactivator yes-associated protein (YAP), which is negatively regulated by the Hippo pathway, was inhibited by overexpressing N3ICD in breast cancer epithelial cells. The ability of Kibra to inhibit EMT has been previously reported. We thus speculated that Notch3 inhibition of EMT is mediated by upregulated Kibra. To verify this hypothesis, a rescue experiment was performed. Evidently, the ability of Notch3 to inhibit EMT can be countered by knocking down Kibra expression. These data suggest that Notch3 inhibits EMT by activating the Hippo/YAP pathway by upregulating Kibra in breast cancer epithelial cells, and Kibra may be a downstream effector of Notch3. These findings deepen our understanding of EMT in both development and disease, and will undoubtedly help to provide new therapeutic strategies for interfering with cancer invasion and metastasis, especially for TNBC.

Acquired platinum resistance involves epithelial to mesenchymal transition through ubiquitin ligase FBXO32 dysregulation

To identify the molecules involved in epithelial to mesenchymal transition (EMT) in urothelial carcinoma (UC) after acquisition of platinum resistance, here we examined the changes in global gene expression before and after platinum treatment. Four invasive UC cell lines, T24, 5637, and their corresponding sublines T24PR and 5637PR with acquired platinum resistance, were assessed by microarray, and the ubiquitin E3 ligase FBXO32 was newly identified as a negative regulator of EMT in UC tumors after acquisition of platinum resistance. In vitro and in vivo studies showed an intimate relationship between FBXO32 expression and EMT, demonstrating that FBXO32 dysregulation in T24PR cells results in elevated expression of the mesenchymal molecules SNAIL and vimentin and decreased expression of the epithelial molecule E-cadherin. The association between FBXO32 expression and EMT was further validated using clinical samples. Knockdown of MyoD expression, a specific target of FBXO32 polyubiquitination, revealed upregulation of E-cadherin expression and downregulation of SNAIL and vimentin expression in T24PR cells. Comparative genomic hybridization array analysis demonstrated loss of heterozygosity at 8q24.13 in T24PR cells, which harbors FBXO32. Our findings suggest the importance of the association between EMT and ubiquitin-proteasome regulation when tumors develop acquired platinum resistance.