Twist1 confers multidrug resistance in colon cancer through upregulation of ATP-binding cassette transporters

Resveratrol as sensitizer in colorectal cancer plasticity

Despite tremendous medical treatment successes, colorectal cancer (CRC) remains a leading cause of cancer deaths worldwide. Chemotherapy as monotherapy can lead to significant side effects and chemoresistance that can be linked to several resistance-activating biological processes, including an increase in inflammation, cellular plasticity, multidrug resistance (MDR), inhibition of the sentinel gene p53, and apoptosis. As a consequence, tumor cells can escape the effectiveness of chemotherapeutic agents. This underscores the need for cross-target therapeutic approaches that are not only pharmacologically safe but also modulate multiple potent signaling pathways and sensitize cancer cells to overcome resistance to standard drugs. In recent years, scientists have been searching for natural compounds that can be used as chemosensitizers in addition to conventional medications for the synergistic treatment of CRC. Resveratrol, a natural polyphenolic phytoalexin found in various fruits and vegetables such as peanuts, berries, and red grapes, is one of the most effective natural chemopreventive agents. Abundant in vitro and in vivo studies have shown that resveratrol, in interaction with standard drugs, is an effective chemosensitizer for CRC cells to chemotherapeutic agents and thus prevents drug resistance by modulating multiple pathways, including transcription factors, epithelial-to-mesenchymal transition-plasticity, proliferation, metastasis, angiogenesis, cell cycle, and apoptosis. The ability of resveratrol to modify multiple subcellular pathways that may suppress cancer cell plasticity and reversal of chemoresistance are critical parameters for understanding its anti-cancer effects. In this review, we focus on the chemosensitizing properties of resveratrol in CRC and, thus, its potential importance as an additive to ongoing treatments.

Epithelial-mesenchymal transition and H2O2 signaling - a driver of disease progression and a vulnerability in cancers

Mutation-selective drugs constitute a great advancement in personalized anticancer treatment with increased quality of life and overall survival in cancers. However, the high adaptability and evasiveness of cancers can lead to disease progression and the development of drug resistance, which cause recurrence and metastasis. A common characteristic in advanced neoplastic cancers is the epithelial-mesenchymal transition (EMT) which is strongly interconnected with H₂O₂ signaling, increased motility and invasiveness. H₂O₂ relays its signal through the installation of oxidative posttranslational modifications on cysteines. The increased H₂O₂ levels that are associated with an EMT confer a heightened sensitivity towards the induction of ferroptosis as a recently discovered vulnerability.

Epithelial to Mesenchymal Transition: A Challenging Playground for Translational Research. Current Models and Focus on TWIST1 Relevance and Gastrointestinal Cancers

Resembling the development of cancer by multistep carcinogenesis, the evolution towards metastasis involves several passages, from local invasion and intravasation, encompassing surviving anoikis into the circulation, landing at distant sites and therein establishing colonization, possibly followed by the outgrowth of macroscopic lesions. Within this cascade, epithelial to mesenchymal transition (EMT) works as a pleiotropic program enabling cancer cells to overcome local, systemic, and distant barriers against diffusion by replacing traits and functions of the epithelial signature with mesenchymal-like ones. Along the transition, a full-blown mesenchymal phenotype may not be accomplished. Rather, the plasticity of the program and its dependency on heterotopic signals implies a pendulum with oscillations towards its reversal, that is mesenchymal to epithelial transition. Cells in intermixed E⇔M states can also display stemness, enabling their replication together with the epithelial reversion next to successful distant colonization. If we aim to include the EMT among the hallmarks of cancer that could modify clinical practice, the gap between the results pursued in basic research by animal models and those achieved in translational research by surrogate biomarkers needs to be filled. We review the knowledge on EMT, derived from models and mechanistic studies as well as from translational studies, with an emphasis on gastrointestinal cancers (GI).

Defining the Role of GLI/Hedgehog Signaling in Chemoresistance: Implications in Therapeutic Approaches

Insight into cancer signaling pathways is vital in the development of new cancer treatments to improve treatment efficacy. A relatively new but essential developmental signaling pathway, namely Hedgehog (Hh), has recently emerged as a major mediator of cancer progression and chemoresistance. The evolutionary conserved Hh signaling pathway requires an in-depth understanding of the paradigm of Hh signaling transduction, which is fundamental to provide the necessary means for the design of novel tools for treating cancer related to aberrant Hh signaling. This review will focus substantially on the canonical Hh signaling and the treatment strategies employed in different studies, with special emphasis on the molecular mechanisms and combination treatment in regard to Hh inhibitors and chemotherapeutics. We discuss our views based on Hh signaling's role in regulating DNA repair machinery, autophagy, tumor microenvironment, drug inactivation, transporters, epithelial-to-mesenchymal transition, and cancer stem cells to promote chemoresistance. The understanding of this Achilles' Heel in cancer may improve the therapeutic outcome for cancer therapy.

Transferrin Coated d-penicillamine-Au-Cu Nanocluster PLGA Nanocomposite Reverses Hypoxia-Induced EMT and MDR of Triple-Negative Breast Cancers

Triple-negative breast cancer (TNBC), the most aggressive subtype of breast cancer, lacks effective targeted therapies due to negative expression of the targetable bioreceptors. Additionally, hypoxic condition in solid tumors contributes to the epithelial to mesenchymal transition (EMT), which aggravates cancer progression, multidrug resistance (MDR), migration, and stemness of the TNBC. A therapeutic module has been established in this regard by coating PLGA nanoparticle with d-penicillamine templated Au-Cu bimetallic nanoclusters. Further, the resultant nanomaterials were coated with recombinant transferrin protein to specifically target transferrin receptor overexpressing TNBC. The synthesized nanocomposites showed strong orange emission band at 630 nm with fluorescence quantum yield of 2%, rendering it suitable for theranostic applications. Experimental results demonstrated efficient cellular internalization and significant innate anti-cell proliferative potential of the nanocomposites. The fabricated nanocomposites were also able to induce cell death in spheroids, which was confirmed by live/dead dual staining results. Furthermore, when EMT-induced TNBC cells were treated with nanocomposites, they generated reactive oxygen species (ROS), depolarized the mitochondrial membrane potential, and induced apoptosis. Gene expression by real-time PCR indicated that treatment of EMT-induced TNBC cells with nanocomposites facilitated mesenchymal to epithelial transition (MET). In MDA-MB-468 cells, treatment with nanocomposites resulted in a 1.35-fold rise in E-cadherin an epithelial marker and a 1.36-fold decrease in vimentin a mesenchymal marker. Similarly, 2.87-fold and 1.76-fold decrease in stemness markers ALDH1A3 and EpCAM were observed in MDA-MB-231. Furthermore, 4.63-fold decrease in expression of ABCC1, a prominent contributor of MDR, was observed in MDA-MB-231. Protein expression studies revealed that nanocomposites reduced p-STAT-3 by 1.61-fold in MDA-MB-231 and by 7.8-fold in MDA-MB-468. Importantly, nanocomposites downregulated the expression of β-catenin by 3-fold in MDA-MB-231 and by 3.11-fold in MDA-MB-468. Downregulation of EMT with concomitant alteration of STAT-3 and β-catenin signaling pathways led to reduced migration ability of the TNBC cells.

linc‑ROR facilitates hepatocellular carcinoma resistance to doxorubicin by regulating TWIST1‑mediated epithelial‑mesenchymal transition

Long non‑coding RNAs are associated with cancer progression. Long intergenic non‑protein coding RNA (linc)‑regulator of reprogramming (ROR) enhances tumor development in hepatocellular carcinoma (HCC). However, the effect of chemoresistance and its underlying mechanisms in HCC are not completely understood. The present study aimed to identify the effect of ROR on sensitivity to doxorubicin (DOX) in HCC cells. In the present study, Cell Counting Kit‑8 and EdU assays were performed to assess cell viability and proliferation, respectively. In addition, E‑cadherin and vimentin protein expression levels were assessed via western blotting and immunofluorescence.The results of the present study demonstrated that HCC cells with high linc‑ROR expression levels were more resistant to DOX, and linc‑ROR knockdown increased HCC cell DOX sensitivity compared with the control group. The results indicated that compared with the NC siRNA group, linc‑ROR knockdown notably suppressed epithelial‑mesenchymal transition by downregulating twist family bHLH transcription factor 1 (TWIST1) expression. TWIST1 knockdown displayed a similar effect on HCC cell DOX sensitivity to linc‑ROR knockdown. Moreover, linc‑ROR knockdown‑induced HCC cell DOX sensitivity was inhibited by TWIST1 overexpression. The present study provided evidence that linc‑ROR promoted HCC resistance to DOX by inducing EMT via interacting with TWIST1. Therefore, linc‑ROR might serve as a therapeutic target for reducing DOX resistance in HCC.

The role of epithelial-mesenchymal transition-regulating transcription factors in anti-cancer drug resistance

The complex orchestration of gene expression that mediates the transition of epithelial cells into mesenchymal cells is implicated in cancer development and metastasis. As the primary regulator of the process, epithelial-mesenchymal transition-regulating transcription factors (EMT-TFs) play key roles in metastasis. They are also highlighted in recent preclinical studies on resistance to cancer therapy. This review describes the role of three main EMT-TFs, including Snail, Twist1, and zinc-finger E homeobox-binding 1 (ZEB1), relating to drug resistance and current possible approaches for future challenges targeting EMT-TFs.

Selective dysregulation of ABC transporters in methotrexate-resistant leukemia T-cells can confer cross-resistance to cytarabine, vincristine and dexamethasone, but not doxorubicin

Pediatric acute lymphoblastic leukemia (pALL) includes 75 % of childhood leukemias, and methotrexate (MTX) is one of the most effective chemotherapy agents prescribed for pALL treatment. The aim of this study was to establish and characterize an MTX-resistant tumor cell model in order to study the mechanism contributing to drug sensitivity loss in pALL. Parental CCRF-CEM cells were treated with a gradual increasing concentration of MTX from 5 nM to 1.28 μM. The resistant subline was then characterized according to the cellular morphology, cellular growth curves and specific mRNA expression changes associated with drug resistance in ALL. Moreover, in vitro cytotoxicity assays were used to analyze cells relative responsiveness to a set of clinically used anti-ALL chemotherapy drugs. The morphological changes observed in the new R-CCRF-CEM/MVCD subline were associated with dysregulation of the EMT-related genes, Twist1 and CDH1. Cells demonstrated downregulation of ABCC1 and the overexpression of ABCA2, ABCA3, and ABCB1 membrane transporters. However, short treatment of the sensitive and parental cell line with MTX did not affect the expression profiles of the former ABC pumps. Moreover, R-CCRF-CEM/MVCD cells demonstrated cross-resistance to cytarabine (cytosine arabinoside, ara-C), vincristine, and dexamethasone, but not doxorubicin. The induced cross-resistance to specific chemotherapy drugs may possibly be attributed to selective dysregulation of the ABC transporters and EMT-related genes. These data may pave the way for the development of new cancer therapeutic strategies.

Establishment of Acquired Cisplatin Resistance in Ovarian Cancer Cell Lines Characterized by Enriched Metastatic Properties with Increased Twist Expression

Ovarian cancer (OC) is the most lethal of the gynecologic cancers, and platinum-based treatment is a part of the standard first-line chemotherapy regimen. However, rapid development of acquired cisplatin resistance remains the main cause of treatment failure, and the underlying mechanism of resistance in OC treatment remains poorly understood. Faced with this problem, our aim in this study was to generate cisplatin-resistant (CisR) OC cell models in vitro and investigate the role of epithelial–mesenchymal transition (EMT) transcription factor Twist on acquired cisplatin resistance in OC cell models. To achieve this aim, OC cell lines OV-90 and SKOV-3 were exposed to cisplatin using pulse dosing and stepwise dose escalation methods for a duration of eight months, and a total of four CisR sublines were generated, two for each cell line. The acquired cisplatin resistance was confirmed by determination of 50% inhibitory concentration (IC₅₀) and clonogenic survival assay. Furthermore, the CisR cells were studied to assess their respective characteristics of metastasis, EMT phenotype, DNA repair and endoplasmic reticulum stress-mediated cell death. We found the IC₅₀ of CisR cells to cisplatin was 3–5 times higher than parental cells. The expression of Twist and metastatic ability of CisR cells were significantly greater than those of sensitive cells. The CisR cells displayed an EMT phenotype with decreased epithelial cell marker E-cadherin and increased mesenchymal proteins N-cadherin and vimentin. We observed that CisR cells showed significantly higher expression of DNA repair proteins, X-ray repair cross-complementing protein 1 (XRCC1) and poly (ADP-ribose) polymerases 1 (PARP1), with significantly reduced endoplasmic reticulum (ER) stress-mediated cell death. Moreover, Twist knockdown reduced metastatic ability of CisR cells by suppressing EMT, DNA repair and inducing ER stress-induced cell death. In conclusion, we highlighted the utilization of an acquired cisplatin resistance model to identify the potential role of Twist as a therapeutic target to reverse acquired cisplatin resistance in OC.

Effect of sodium butyrate on ABC transporters in lung cancer A549 and colorectal cancer HCT116 cells

Histone deacetylase (HDAC) inhibitors and DNA alkylators are effective components of combination chemotherapy. The aim of the present study was to investigate the possible mechanism of their synergism by detecting the effect of HDAC inhibitors on the expression levels of drug transporters that export DNA alkylators. It was demonstrated that the HDAC inhibitor sodium butyrate (NaB) induced the differential expression of multidrug resistant ATP-binding cassette (ABC) transporters in lung cancer and colorectal cancer cells. Specifically, NaB increased the mRNA expression levels of ABC subfamily B member 1 (ABCB1), ABCC10 and ABCC12, and protein expression levels of multidrug resistance-1 (MDR1), multidrug resistance-associated protein 7 (MRP7) and MRP9. Moreover, NaB decreased the expression levels of ABCC1, ABCC2 and ABCC3 mRNAs, as well as those of MRP1, MRP2 and MRP3 proteins. The molecular mechanism underlying this process was subsequently investigated. NaB decreased the expression of HDAC4, but not HDAC1, HDAC2 or HDAC3. In addition, NaB promoted histone H3 acetylation and methylation at lysine 9, as well as MDR1 acetylation, suggesting that acetylation and methylation may be involved in NaB-mediated ABC transporter expression. Thus, the present results indicated that the synergism of the HDAC inhibitors with the DNA alkylating agents may due to the inhibitory effect of MRPs by HDAC inhibitors. The findings also suggested the possibility of antagonistic effects following the combined treatment of HDAC inhibitors with MDR1 ligands.

α-Linolenic acid inhibits the migration of human triple-negative breast cancer cells by attenuating Twist1 expression and suppressing Twist1-mediated epithelial-mesenchymal transition

α-Linolenic acid (ALA), an essential fatty acid, has anticancer activity in breast cancer, but the mechanism of its effects in triple-negative breast cancer (TNBC) remains unclear. We investigated the effect of ALA on Twist1, which is required to initiate epithelial-mesenchymal transition (EMT) and promotes tumor metastasis, and Twist1-mediated migration in MDA-MB231, MDA-MB468 and Hs578T cells. Twist1 protein was constitutively expressed in these TNBC cells, particularly MDA-MB-231 cells. Treatment with 100 μM ALA and Twist1 siRNA markedly decreased the Twist1 protein level and cell migration. Moreover, ALA transiently attenuated the nuclear accumulation of STAT3α as well as Twist1 mRNA expression. Treatment with ALA significantly attenuated the phosphorylation of JNK, ERK and Akt and decreased the phosphorylation of Twist1 at serine 68 in MDA-MB-231 cells. ALA accelerated Twist1 degradation in the presence of cycloheximide, whereas the ubiquitination and degradation of Twist1 by ALA was suppressed by MG-132. Pretreatment with ALA mimicked Twist1 siRNA, increased the protein expression of epithelial markers such as E-cadherin, and decreased the protein expression of mesenchymal markers including Twist1, Snail2, N-cadherin, vimentin, and fibronectin. Our findings suggest that ALA can be used not only to abolish EMT but also to suppress Twist1-mediated migration in TNBC cells.

Tumor microenvironment and epithelial mesenchymal transition as targets to overcome tumor multidrug resistance

It is well established that multifactorial drug resistance hinders successful cancer treatment. Tumor cell interactions with the tumor microenvironment (TME) are crucial in epithelial-mesenchymal transition (EMT) and multidrug resistance (MDR). TME-induced factors secreted by cancer cells and cancer-associated fibroblasts (CAFs) create an inflammatory microenvironment by recruiting immune cells. CD11b+/Gr-1+ myeloid-derived suppressor cells (MDSCs) and inflammatory tumor associated macrophages (TAMs) are main immune cell types which further enhance chronic inflammation. Chronic inflammation nurtures tumor-initiating/cancer stem-like cells (CSCs), induces both EMT and MDR leading to tumor relapses. Pro-thrombotic microenvironment created by inflammatory cytokines and chemokines from TAMs, MDSCs and CAFs is also involved in EMT and MDR. MDSCs are the most common mediators of immunosuppression and are also involved in resistance to targeted therapies, e.g. BRAF inhibitors and oncolytic viruses-based therapies. Expansion of both cancer and stroma cells causes hypoxia by hypoxia-inducible transcription factors (e.g. HIF-1α) resulting in drug resistance. TME factors induce the expression of transcriptional EMT factors, MDR and metabolic adaptation of cancer cells. Promoters of several ATP-binding cassette (ABC) transporter genes contain binding sites for canonical EMT transcription factors, e.g. ZEB, TWIST and SNAIL. Changes in glycolysis, oxidative phosphorylation and autophagy during EMT also promote MDR. Conclusively, EMT signaling simultaneously increases MDR. Owing to the multifactorial nature of MDR, targeting one mechanism seems to be non-sufficient to overcome resistance. Targeting inflammatory processes by immune modulatory compounds such as mTOR inhibitors, demethylating agents, low-dosed histone deacetylase inhibitors may decrease MDR. Targeting EMT and metabolic adaptation by small molecular inhibitors might also reverse MDR. In this review, we summarize evidence for TME components as causative factors of EMT and anticancer drug resistance.

Characterization of Melanoma Cell Lines Resistant to Vemurafenib and Evaluation of Their Responsiveness to EGFR- and MET-Inhibitor Treatment

Constitutively active mutated BRAF kinase occurs in more than 40% of patients suffering from melanoma. To block its activity, a specific inhibitor, vemurafenib, is applied as a therapy. Unfortunately, patients develop resistance to this drug rather quickly. Previously, we demonstrated that pairs of inhibitors directed against EGFR (epidermal growth factor receptor) and MET (hepatocyte growth factor receptor) trigger a synergistic cytotoxic effect in human melanoma cells, and decrease their invasive abilities. In this study, we aimed to generate and characterize melanoma cells resistant to vemurafenib treatment, and then to evaluate the effectiveness of a previously developed therapy in this model. We showed that melanoma cells resistant to the BRAF inhibitor are characterized by a lower proliferation rate and they acquire a spindle-like shape. Using Western Blot, we also noticed increased levels of EGFR, MET, and selected markers of cancer stem cells in generated cell lines. Resistant cells also exhibited increased invasive abilities and elevated proteolytic activity, observed using scratch wound assays and gelatin zymography. Moreover, combination therapy reduced their viability, as measured with a colorimetric cytotoxicity test, and decreased invasiveness. The obtained results validate the application of combination therapy directed against EGFR and MET in melanoma cells resistant to treatment with inhibitors of mutated BRAF.

Ubiquitin-specific peptidase 22 promotes proliferation and metastasis in human colon cancer

Colon cancer is one of the most common malignant tumors in the world; however, the mechanism underlying the progression of colon cancer remains unclear. In the present study, the expression of ubiquitin-specific peptidase 22 (USP22) in paraffin sections of human colon cancer tissues and normal colon tissues were examined using immunohistochemistry. The human colon cancer cell lines HCT116 and HT29 were used for USP22 knockdown experiments, and functional assays were performed. The results demonstrated that compared with normal colon tissues, human colon cancer tissues exhibited upregulated expression of USP22 and this was associated with tumor lymph node metastasis and tumor stage in colon cancer tissues. In addition, upregulated expression of USP22 was significantly correlated with both lower relapse-free survival and lower overall survival rates in patients with colon cancer. When USP22 was silenced in colon cancer cell lines, this resulted in a decrease in cell proliferation and metastatic behaviors. Furthermore, Bmi-1 and Cyclin D2 were found to be positively regulated by USP22, which may have mediated the tumorigenic effects of USP22 in human colon cancer. The results of the present study may have significant implications for examining the underlying mechanisms of cancer development and the potential development of cancer therapeutics.

Effects of histone deacetylase inhibitors on ATP-binding cassette transporters in lung cancer A549 and colorectal cancer HCT116 cells

Histone deacetylase (HDAC) inhibitors and DNA alkylators are effective components used in combination chemotherapy. In the present study, the effects of HDAC inhibitors on the expression of ATP-binding cassette (ABC) transporters were investigated. It was observed that HDAC inhibitors induced the expression of multidrug-resistant ABC transporters differently in lung cancer A549 cells than in colorectal cancer HCT116 cells. In these two cell lines, the HDAC inhibitors suberoylanilide hydroxamic acid (SAHA) and trichostatin A (TSA) significantly increased ABCB1 expression at the mRNA and protein levels, whereas they had no evident effect on ABCG2 protein expression. SAHA and TSA decreased ABCG2 mRNA expression in A549 cells and had no evident effect on ABCG2 mRNA expression in HCT116 cells. Notably, SAHA and TSA increased the mRNA expression levels of ABCC5, ABCC6, ABCC10, ABCC11 and ABCC12, as well as the protein expression levels of ABCC2, ABCC10 and ABCC12. By contrast, these inhibitors decreased the mRNA expression levels of ABCC1, ABCC2, ABCC3 and ABCC4, as well as the expression of ABCC1 and ABCC3 proteins. Furthermore, SAHA and TSA were found to downregulate HDAC3 and HDAC4, but not HDAC1 and HDAC2. Taken together, the results suggested that HDAC inhibitors work synergistically with DNA alkylators, in part, due to the inhibitory effect of these inhibitors on ABCC1 expression, which translocates these alkylators from inside to outside of cancer cells. These results further suggested the possibility of antagonism when HDAC inhibitors are combined with anthracyclines and other ABCB1 drug ligands in chemotherapy.

miR-34a Regulates Multidrug Resistance via Positively Modulating OAZ2 Signaling in Colon Cancer Cells

Although aberrant expression of miR-34a, an essential tumor suppressor miRNA, has been frequently observed in colon cancer (CCa), whether miR-34a can regulate CCa progression by modulating other facets of this malignancy (such as multidrug resistance, MDR) remains unknown. Here, we report for the first time that miR-34a expression was significantly downregulated in clinical CCa samples from oxaliplatin-resistant patients and in experimentally established multidrug-resistant CCa cells. By using histoculture drug response assay, we further confirmed that clinical CCa samples with lower miR-34a expression appeared to be more resistant to chemotherapy. Functionally, ectopic expression of exogenous miR-34a resensitized multidrug-resistant HCT-8/OR cells to oxaliplatin treatment, whereas miR-34a inhibition augmented the oxaliplatin resistance in chemosensitive HCT-8 cells. Mechanistically, miR-34a positively regulated the mRNA stability of the ornithine decarboxylase antizyme 2 (OAZ2) by directly targeting its three prime untranslated region (3′UTR). Consequently, suppression of the expression of miR-34a/OAZ2 signaling by chemotherapeutic agents significantly enhanced the activation of MDR-associated ATP-binding cassette (ABC) transporters and antiapoptosis pathways, thus leading to MDR development in CCa cells. Collectively, our combined analysis reveals a critical role of miR-34a/OAZ2 cascade in conferring a proper cellular response to CCa chemotherapy.

Knockdown of TWIST enhances the cytotoxicity of chemotherapeutic drugs in doxorubicin-resistant HepG2 cells by suppressing MDR1 and EMT

The transcription factor twist family bHLH transcription factor 1 (TWIST), which is a member of the basic helix-loop-helix class of proteins, is known to induce epithelial-mesenchymal transition (EMT) and promote cancer metastasis. TWIST has previously been reported to be associated with multidrug resistance (MDR), since its depletion increases drug sensitivity. Although these previous studies have established a strong association between EMT and MDR, the molecular mechanism remains obscure. The present study demonstrated that TWIST protein expression was elevated in liver cancer, and was positively correlated with multidrug resistance protein 1 (MDR1) expression. Conversely, MDR1 was negatively correlated with E‑cadherin expression in liver cancer samples. In addition, the present study indicated that doxorubicin-resistant HepG2 (R‑HepG2) cells acquired an EMT phenotype. TWIST was also more highly expressed in R‑HepG2 cells compared with in parental HepG2 cells. Knockdown of TWIST increased the sensitivity of R‑HepG2 cells to 5-fluroracil, cisplatin and doxorubicin through a reduction in MDR1 expression and drug efflux ability. Furthermore, knockdown of TWIST in R‑HepG2 cells inhibited the migratory ability of cells and suppressed the EMT phenotype. These findings demonstrated that targeting TWIST may be considered a novel strategy to overcome drug resistance in liver cancer.

An extracellular matrix (ECM) model at high malignant colorectal tumor increases chondroitin sulfate chains to promote epithelial-mesenchymal transition and chemoresistance acquisition

Chemoresistance is one of the major barriers for tumor chemotherapy. It is clinically known that chemoresistance increases during tumor progression. Additionally, the extracellular matrix (ECM) is also remodeled during tumor progression. However, it remains unclear how ECM remodeling contributes to chemoresistance acquisition. Recently, it has been reported that epithelial-mesenchymal transition (EMT) contributes to chemoresistance acquisition. Here, how ECM remodeling contributes to 5-fluorouracil (5-FU) resistance acquisition was investigated from the viewpoints of EMT using in vitro ECM models mimicking native ECM in colorectal tumor tissue at three different malignant levels. 5-FU partially induced EMT and increased ABCB1 in colorectal HT-29 cells via TGF-β signaling (an invasive tumor cell model). When HT-29 cells were cultured on an ECM model (high malignant matrices) mimicking native ECM in highly malignant tumor tissues, the cells facilitated TGF-β-induced EMT and increased ABCB1 upregulation compared with that of other ECM models mimicking the low malignant level and normal tissues. High malignant matrices contained more chondroitin sulfate (CS) chains than those of other ECM models. Finally, CS chain-reduced high malignant matrices could not facilitate ABCB1 upregulation and TGF-β-induced EMT. These results demonstrated that ECM remodeling during tumor progression increased CS chains to facilitate EMT and ABCB1 upregulation, contributing to chemoresistance acquisition.

Epithelial Mesenchymal Transition in Embryonic Development, Tissue Repair and Cancer: A Comprehensive Overview

The epithelial mesenchymal transition (EMT) plays a central role in both normal physiological events (e.g., embryonic development) and abnormal pathological events (e.g., tumor formation and metastasis). The processes that occur in embryonic development are often reactivated under pathological conditions such as oncogenesis. Therefore, defining the regulatory networks (both gene and protein levels) involved in the EMT during embryonic development will be fundamental in understanding the regulatory networks involved in tumor development, as well as metastasis. There are many molecules, factors, mediators and signaling pathways that are involved in the EMT process. Although the EMT is a very old topic with numerous publications, recent new technologies and discoveries give this research area some new perspective and direction. It is now clear that these important processes are controlled by a network of transcriptional and translational regulators in addition to post-transcriptional and post-translational modifications that amplify the initial signals. In this review article, we will discuss some key concepts, historical findings, as well as some recent progresses in the EMT research field.