Hypoxia-inducing factors as master regulators of stemness properties and altered metabolism of cancer- and metastasis-initiating cells

Hypoxic Microenvironment Induces EMT and Upgrades Stem-Like Properties of Gastric Cancer Cells

Hypoxia microenvironment, as a major feature of solid tumors, increases tumors progression and metastasis. To research whether hypoxia influences the epithelial-mesenchymal transition (EMT) and cancer stem cells (CSCs) of gastric cancer cells and their cell biological behaviors. Human gastric cancer cell lines BGC823 and SGC7901 were cultivated in different oxygen tensions for proliferation, colony formation, soft agar formation, migration, and invasion analyses. Markers of EMT (E-cadherin, N-cadherin, Vimentin, and Snail) and markers of CSCs (Sox2, Oct4, and Bmi1) were investigated by real-time polymerase chain reaction, Western blotting, and immunofluorescent analysis. Cultivated at hypoxic condition, BGC823 and SGC7901 cells morphology began to change significantly. The cells pretreated under hypoxia grew faster than those cells always cultivated in normoxia. Meanwhile, hypoxia pretreatment dramatically promoted cell proliferation, migration and invasion, and increased capability of colony and soft agar colony formation. Furthermore, under hypoxia, E-cadherin decreased and N-cadherin, Vimentin, Snail, Sox2, Oct4, and Bmi1 increased both on the level of messenger RNA and protein. We drew a conclusion that the hypoxic microenvironment induced EMT, upgraded stem-like properties of gastric cancer cells, promoted invasion and metastasis, and behaved more malignantly.

Cancer stem cells and mesenchymal stem cells in the hypoxic tumor niche: two different targets for one only drug

Putative cancer stem cells (CSCs) reside in a hypoxic microenvironment where mesenchymal stem cells (MSCs) are also present. In this niche MSCs seem to promote the generation of CSCs and sustain tumor progression. Therefore, it may assume clinical relevance to produce a drug which kills not only CSCs but also MSCs. We hypothesized that bifunctional nanoparticles, loaded with a HIF-1α inhibitor and conjugated with an aptamer targeting a common receptor of CSCs and MSCs, may fulfill this strategy. The nanoparticle should ensure that: (1) the conveyed drug is less susceptible to degradation, (2) the common receptor of CSCs and MSCs is recognized by a superselective aptamer, and (3) receptor-mediated internalization is the main process to enter target cells. Small RNA or DNA aptamers represent an advantage over antibodies because do not cause immune reactions, are better internalized into the target cell, are more resistant to degradation, their cost of production are lower, and the purity of the oligonucleotide ligand is extremely elevated. Concerning the drugs to be delivered, we suggest to employ those exerting an anti-HIF-1α activity because they should be harmful for hypoxic CSCs and MCSs in their tumor niche but provide very limited toxicity, or even none, to well-oxygenated normal cells. Corresponding experimental approaches to perform pre-clinical studies and verify this hypothesis are also addressed.

Downregulation of CXCR4 by SDF-KDEL in SBC-5 cells inhibits their migration in vitro and organ metastasis in vivo

Metastasis is the principal cause of morbidity and mortality in cancer patients. The master genes that govern organ-selective metastasis remain elusive. We compared the expression levels of C-X-C chemokine receptor type 4 (CXCR4) in the human small cell lung cancer (SCLC) cells, SBC-5 and SBC-3, by flow cytometric analysis and found that CXCR4 was expressed at markedly higher levels in the SBC-5 cells which can produce multiple organ metastasis, particularly bone metastasis compared to the SBC-3 cells. Stromal-derived-factor-1 (SDF-1)-CXCR4 has been shown to regulate cell migration and metastasis in a various types of cancer; however, the roles of SDF-1-CXCR4 in the organ-selective metastasis of SCLC in vivo remain to be elucidated. Thus, in this study, we constructed a phenotype of SBC-5 cells in which CXCR4 was knocked out using the intrakine strategy and found that the downregulation of CXCR4 inhibited cell migration and invasion, but did not affect cell proliferation or apoptosis in vitro. In in vivo experiments, the knockout of CXCR4 suppressed the development of metastastic lesions in the lungs, liver and bone, but did not decrease metastasis to the kidneys. Our data demonstrate that CXCR4 is a candidate gene involved in the development of metastastic lesions in specific organs, such as the lungs, bone and liver, which can secrete high concentrations of SDF-1, the sole ligand of CXCR4. Thus, CXCR4 may prove to be a promising target for the prevention and effective treatment of metastastic lesions due to SCLC.

Perspectives of TGF-β inhibition in pancreatic and hepatocellular carcinomas

Advanced pancreatic ductal adenocarcinoma (PDAC) and hepatocellular carcinoma (HCC) are non-curable diseases with a particularly poor prognosis. Over the last decade, research has increasingly focused on the microenvironment surrounding cancer cells, and its role in tumour development and progression. PDAC and HCC differ markedly regarding their pathological features: PDAC are typically stromal-predominant, desmoplastic, poorly vascularized tumours, whereas HCC are cellular and highly vascularized. Despite these very different settings, PDAC and HCC share transforming growth factor-β (TGF-β) as a common key-signalling mediator, involved in epithelial-to-mesenchymal transition, invasion, and stroma-tumour dialogue. Recently, novel drugs blocking the TGF-β pathway have entered clinical evaluation demonstrating activity in patients with advanced PDAC and HCC. TGF-β signalling is complex and mediates both pro- and anti-tumoural activities in cancer cells depending on their context, in space and time, and their microenvironment. In this review we provide a comprehensive overview of the role of the TGF-β pathway and its deregulation in PDAC and HCC development and progression at the cellular and microenvironment levels. We also summarize key preclinical and clinical data on the role of TGF-β as a target for therapeutic intervention in PDAC and HCC, and explore perspectives to optimize TGF-β inhibition therapy.

Endothelial hypoxic metabolism in carcinogenesis and dissemination: HIF-A isoforms are a NO metastatic phenomenon

Tumor biology is a broad and encompassing field of research, particularly given recent demonstrations of the multicellular nature of solid tumors, which have led to studies of molecular and metabolic intercellular interactions that regulate cancer progression. Hypoxia is a broad stimulus that results in activation of hypoxia inducible factors (HIFs). Downstream HIF targets include angiogenic factors (e.g. vascular endothelial growth factor, VEGF) and highly reactive molecules (e.g. nitric oxide, NO) that act as cell-specific switches with unique spatial and temporal effects on cancer progression. The effect of cell-specific responses to hypoxia on tumour progression and spread, as well as potential therapeutic strategies to target metastatic disease, are currently under active investigation. Vascular endothelial remodelling events at tumour and metastatic sites are responsive to hypoxia, HIF activation, and NO signalling. Here, we describe the interactions between endothelial HIF and NO during tumor growth and spread, and outline the effects of endothelial HIF/NO signalling on cancer progression. In doing so, we attempt to identify areas of metastasis research that require attention, in order to ultimately facilitate the development of novel treatments that reduce or prevent tumour dissemination.

Targeting the TGFβ pathway for cancer therapy

The TGFβ signaling pathway has pleiotropic functions regulating cell growth, differentiation, apoptosis, motility and invasion, extracellular matrix production, angiogenesis, and immune response. TGFβ signaling deregulation is frequent in tumors and has crucial roles in tumor initiation, development and metastasis. TGFβ signaling inhibition is an emerging strategy for cancer therapy. The role of the TGFβ pathway as a tumor-promoter or suppressor at the cancer cell level is still a matter of debate, due to its differential effects at the early and late stages of carcinogenesis. In contrast, at the microenvironment level, the TGFβ pathway contributes to generate a favorable microenvironment for tumor growth and metastasis throughout all the steps of carcinogenesis. Then, targeting the TGFβ pathway in cancer may be considered primarily as a microenvironment-targeted strategy. In this review, we focus on the TGFβ pathway as a target for cancer therapy. In the first part, we provide a comprehensive overview of the roles played by this pathway and its deregulation in cancer, at the cancer cell and microenvironment levels. We go on to describe the preclinical and clinical results of pharmacological strategies to target the TGFβ pathway, with a highlight on the effects on tumor microenvironment. We then explore the perspectives to optimize TGFβ inhibition therapy in different tumor settings.

HIF1α Regulates mTOR Signaling and Viability of Prostate Cancer Stem Cells

Tumor-initiating subpopulations of cancer cells, also known as cancer stem cells (CSC), were recently identified and characterized in prostate cancer. A well-characterized murine model of prostate cancer was used to investigate the regulation of hypoxia-inducible factor 1α (HIF1A/HIF1α) in CSCs and a basal stem cell subpopulation (Lin(-)/Sca-1(+)/CD49f(+)) was identified, in primary prostate tumors of mice, with elevated HIF1α expression. To further analyze the consequences of hypoxic upregulation on stem cell proliferation and HIF1α signaling, CSC subpopulations from murine TRAMP-C1 cells (Sca-1(+)/CD49f(+)) as well as from a human prostate cancer cell line (CD44(+)/CD49f(+)) were isolated and characterized. HIF1α levels and HIF target gene expression were elevated in hypoxic CSC-like cells, and upregulation of AKT occurred through a mechanism involving an mTOR/S6K/IRS-1 feedback loop. Interestingly, resistance of prostate CSCs to selective mTOR inhibitors was observed because of HIF1α upregulation. Thus, prostate CSCs show a hypoxic deactivation of a feedback inhibition of AKT signaling through IRS-1. In light of these results, we propose that deregulation of the PI3K/AKT/mTOR pathway through HIF1α is critical for CSC quiescence and maintenance by attenuating CSC metabolism and growth via mTOR and promoting survival by AKT signaling. We also propose that prostate CSCs can exhibit primary drug resistance to selective mTOR inhibitors.

IMPLICATIONS

This work contributes to a deeper understanding of hypoxic regulatory mechanisms in CSCs and will help devise novel therapies against prostate cancer.

Strategies to improve homing of mesenchymal stem cells for greater efficacy in stem cell therapy

Stem/progenitor cell-based therapeutic approach in clinical practice has been an elusive dream in medical sciences, and improvement of stem cell homing is one of major challenges in cell therapy programs. Stem/progenitor cells have a homing response to injured tissues/organs, mediated by interactions of chemokine receptors expressed on the cells and chemokines secreted by the injured tissue. For improvement of directed homing of the cells, many techniques have been developed either to engineer stem/progenitor cells with higher amount of chemokine receptors (stem cell-based strategies) or to modulate the target tissues to release higher level of the corresponding chemokines (target tissue-based strategies). This review discusses both of these strategies involved in the improvement of stem cell homing focusing on mesenchymal stem cells as most frequent studied model in cellular therapies.

Altered gene products involved in the malignant reprogramming of cancer stem/progenitor cells and multitargeted therapies

Recent studies in the field of cancer stem cells have revealed that the alterations in key gene products involved in the epithelial-mesenchymal transition (EMT) program, altered metabolic pathways such as enhanced glycolysis, lipogenesis and/or autophagy and treatment resistance may occur in cancer stem/progenitor cells and their progenies during cancer progression. Particularly, the sustained activation of diverse developmental cascades such as hedgehog, epidermal growth factor receptor (EGFR), Wnt/β-catenin, Notch, transforming growth factor-β (TGF-β)/TGF-βR receptors and/or stromal cell-derived factor-1 (SDF-1)/CXC chemokine receptor 4 (CXCR4) can play critical functions for high self-renewal potential, survival, invasion and metastases of cancer stem/progenitor cells and their progenies. It has also been observed that cancer cells may be reprogrammed to re-express different pluripotency-associated stem cell-like markers such as Myc, Oct-3/4, Nanog and Sox-2 along the EMT process and under stressful and hypoxic conditions. Moreover, the enhanced expression and/or activities of some drug resistance-associated molecules such as Bcl-2, Akt/molecular target of rapamycin (mTOR), nuclear factor-kappaB (NF-κB), hypoxia-inducible factors (HIFs), macrophage inhibitory cytokine-1 (MIC-1) and ATP-binding cassette (ABC) multidrug transporters frequently occur in cancer cells during cancer progression and metastases. These molecular events may cooperate for the survival and acquisition of a more aggressive and migratory behavior by cancer stem/progenitor cells and their progenies during cancer transition to metastatic and recurrent disease states. Of therapeutic interest, these altered gene products may also be exploited as molecular biomarkers and therapeutic targets to develop novel multitargeted strategies for improving current cancer therapies and preventing disease relapse.

Increased expression levels of S100A4 associated with hypoxia-induced invasion and metastasis in esophageal squamous cell cancer

Here, we explored the expression of S100A4 in esophageal squamous cell cancer (ESCC) tissues and investigated its role in hypoxia-induced invasion and metastasis in ESCC cell lines EC-1 and EC-9706. Immunohistochemistry analysis demonstrated that S100A4 was overexpressed in human ESCC tissues especially in ESCC tissues with deep invasion and lymph node metastasis. Hypoxia-induced S100A4 overexpression was observed in EC-1 and EC-9706 cells, in which it was associated with invasion and metastasis. Furthermore, we used EC-1 and EC-9706 cells again to upregulate or knockdown the expression S100A4 to investigate the mechanism role of S100A4 in hypoxia-induced invasion and metastasis in ESCC cells. And the results showed that S100A4 played an important role in promoting the invasion and metastasis of EC-1 and EC-9706 cells under hypoxia. Therefore, S100A4 overexpression might be an important mechanism by which hypoxia induced invasion and metastasis, and S100A4 could also be a potential target for the treatment of ESCC.

Regulatory effect of merlin-1 on adhesion/metastasis and cytoskeleton remodeling in gastric cancer cells under hypoxia

AIM: To investigate the regulatory effect of merlin-1 on cell proliferation, adhesion/metastasis and cytoskeleton remodeling in gastric cancer cells under hypoxia from Qinghai Han-, Hui- and Tibetan-ethnic patients, and to study if the function of merlin-1 in different ethnic groups is related to ethnic specificity under normoxic or hypoxic conditions.

METHODS: MTT assay was used to analyze the influence of merlin-1 on the cell proliferation, adhesion/metastasis and motility, and immunofluorescence staining was performed to detect cytoskeleton remodeling, morphological changes, and the distribution of microvilli on the surface of gastric cancer cells from Han-, Hui- and Tibetan-ethnic patients. In addition, we explored whether the function of merlin-1 in different ethnic groups is correlated with ethnic specificity under normoxic or hypoxic conditions.

RESULTS: The proliferation of gastric cancer cells from Han-, Hui- and Tibetan-ethnic groups was inhibited by merlin-1 under both normoxic and conditions (P_normoxic = 0.00, 0.00, 0.00; P_hypoxic = 0.00, 0.00, 0.00), and the influence of merlin-1 on cancer cell proliferation was not related to ethnic specificity (P_normoxic ≥ 0.05; P_hypoxic ≥ 0.05). The results of adhesion/metastasis analysis showed that merlin-1 inhibited the adhesion/metastasis ability of gastric cancer cells from Han-, Hui- and Tibetan-ethnic groups under both normoxic and hypoxic conditions (P_normoxic = 0.00, 0.00, 0.00; P_hypoxic = 0.00, 0.00, 0.00), and the inhibitory effect of merlin-1 in three ethnic groups showed no significant differences [P_normoxic = 0.51 (3 h), 0.07 (48 h); P_hypoxic = 0.47 (3 h), 0.17 (48 h)]. By detection of cytoskeleton remodeling, morphological change and microvilli distribution, it was found that merlin-1 enhanced cytoskeleton remodeling under hypoxic conditions compared with normoxic conditions.

CONCLUSION: Merlin-1 can inhibit the proliferation and adhesion/metastasis of gastric cancer cells under both hypoxic and normoxic conditions, which is independent on the ethnicity of patients from whom gastric cancer cells are obtained. However, merlin-1 enhances cytoskeleton remodeling under hypoxic conditions.

Deconstructing breast cancer cell biology and the mechanisms of multidrug resistance

Cancer complexity constantly challenges the way that clinicians manage breast cancer therapy. Tumor heterogeneity and intratumoral stroma characteristics allow cells with different phenotypes and deregulated apoptotic, proliferative and migration abilities to co-exist contributing to a disappointing therapeutic response. While new approaches are being associated with conventional chemotherapy, such as hormonal therapy or target monoclonal antibodies, recurrence and metastasization are still observed. Membrane transporters are the cell's first line of contact with anticancer drugs having a major role in multidrug resistance events. This structural-based activity enables the cell to be drug-resistant by decreasing drug intracellular concentration through an efflux-transport mechanism, mainly associated with overexpression of ATP-binding cassette (ABC) proteins. This review focuses on some of the important structural and biological properties of the malignant cell and tumor microenvironment, addressing the role of the membrane ABC transporters in therapeutic outcomes, and highlighting related molecular pathways that may represent meaningful target therapies.

Genetics of breast cancer bone metastasis: a sequential multistep pattern

Bone metastasis accounts for the vast majority of breast cancer (BC) metastases, and is related to a high rate of morbidity and mortality. A number of seminal studies have uncovered gene expression signatures involved in BC development and bone metastasis; each of them points at a distinct step of the 'invasion-metastasis cascade'. In this review, we provide most recently discovered functions of sets of genes that are selected from widely accepted gene signatures that are implicate in BC progression and bone metastasis. We propose a possible sequential pattern of gene expression that may lead a benign primary breast tumor to get aggressiveness and progress toward bone metastasis. A panel of genes which primarily deal with features like DNA replication, survival, proliferation, then, angiogenesis, migration, and invasion has been identified. TGF-β, FGF, NFκB, WNT, PI3K, and JAK-STAT signaling pathways, as the key pathways involved in breast cancer development and metastasis, are evidently regulated by several genes in all three signatures. Epithelial to mesenchymal transition that is also an important mechanism in cancer stem cell generation and metastasis is evidently regulated by these genes. This review provides a comprehensive insight regarding breast cancer bone metastasis that may lead to a better understanding of the disease and take step toward better treatments.

Expression and significance of MMP2 and HIF-1α in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a serious threat to human health. HCC is a malignant tumor and its invasion and metastasis are the result of multigene interactions. Matrix metalloproteinase-2 (MMP-2) is capable of degrading the majority of components of the extracellular matrix and is regarded to closely correlate with tumor invasion and metastasis. Furthermore, the hypoxia-inducible factor 1α (HIF-1α) is an important transcription factor, which is closely associated with the process of tumor growth. The aim of the present study was to investigate the expression of MMP2 and HIF-1α) in HCC, and the relationship between MMP2/HIF-1α protein expression and the clinical/pathological characteristics of HCC. The mRNA levels of MMP2 and HIF-1α were detected in 32 cases of HCC and the corresponding normal adjacent tissues with fluorescence-based quantitative polymerase chain reaction (qPCR). The protein expression of MMP2 and HIF-1α was assessed in 45 HCC cases and 33 cases of corresponding normal adjacent tissue, using immunohistochemical methods. The association between MMP2/HIF-1α and pathological features of HCC, and the correlation between MMP2 and HIF-1α were analyzed. The Kaplan-Meier method was used to assess the impact of MMP2 and HIF-1α expression on survival. The fluorescence-based qPCR demonstrated that MMP2 and HIF-1α mRNA expression levels in the HCC tissues were 0.84±0.17 and 0.87±0.11, respectively, which were significantly higher than those in the adjacent normal tissues (0.70±0.13 and 0.68±0.13, respectively; P<0.05). Immunohistochemical analysis revealed that MMP2 and HIF-1α protein expression in the HCC tissues was 63.1 and 70.8%, respectively, which was also higher than that in the adjacent normal tissues (34.2 and 36.8%, respectively). There was no significant correlation between the expression of MMP2 or HIF-1α protein and the age or gender of patients with HCC (P>0.05). However, there was significant correlation between MMP2 or HIF-1α protein expression and tumor size, metastasis, presence of a capsule and clinical TNM staging of HCC. Their expression also had a significant effect on patient survival time. In conclusion, MMP2 and HIF-1α are overexpressed in HCC, and the MMP2 signaling pathway may promote the development of HCC together with HIF-1α.

MicroRNAs and epigenetic mechanisms of rhabdomyosarcoma development

Rhabdomyosarcoma is the most common type of soft tissue sarcoma in children. Two main subtypes of rhabdomyosarcoma with different molecular pattern and distinct clinical behaviour may be identified - embryonal and alveolar rhabdomyosarcoma. All types of rhabdomyosarcoma are believed to be of myogenic origin as they express high levels of myogenesis-related factors. They all, however, fail to undergo a terminal differentiation which results in tumour formation. In the aberrant regulation of myogenesis in rhabdomyosarcoma, microRNAs and epigenetic factors are particularly involved. Indeed, these mediators seem to be even more significant for the development of rhabdomyosarcoma than canonical myogenic transcription factors like MyoD, a master regulatory switch for myogenesis. Therefore, in this review we focus on the regulation of rhabdomyosarcoma progression by microRNAs, and especially on microRNAs of the myo-miRNAs family (miR-1, -133a/b and -206), other well-known myogenic regulators like miR-29, and on microRNAs recently recognized to play a role in the differentiation of rhabdomyosarcoma, such as miR-450b-5p or miR-203. We also review changes in epigenetic modifiers associated with rhabdomyosarcoma, namely histone deacetylases and methyltransferases, especially from the Polycomp Group, like Yin Yang1 and Enhancer of Zeste Homolog2. Finally, we summarize how the functioning of these molecules can be affected by oxidative stress and how antioxidative enzymes can influence the development of this tumour. This article is part of a Directed Issue entitled: Rare Cancers.

A new twist in neuroendocrine tumor research: Pacak-Zhuang syndrome, HIF-2α as the major player in its pathogenesis and future therapeutic options

Backround. There is increasing evidence of the role of hypoxia or pseudohypoxia in tumorigenesis, including pheochromocytoma (PHEO) and paraganglioma (PGL). (Pseudo)hypoxia leads to activation of hypoxia-inducible transcription factors (HIFs) and thus, promotes the transcription of hypoxia-responsive genes which are involved in tumorigenesis. Recently identified is a new syndrome consisting of multiple and recurrent PGLs or PHEOs, somatostatinoma, and congenital polycythemia, due to somatic hypoxia-inducible factor 2α gene (HIF2A) mutations.

METHODS AND RESULTS

PubMed and Web of Science online databases were used to search reviews and original articles on the HIF, PHEO/PGL, and Pacak-Zhuang syndrome.

CONCLUSIONS

The novel somatic and germline gain-of-function HIF2A mutations described latterly emphasize the role of the HIF-2α in the PHEO/PGL development and these findings designate HIF, especially HIF-2α, as a promising treatment target.

miRNA in Prostate Cancer: New Prospects for Old Challenges

Prostate cancer (PCa) is one of the most commonly diagnosed cancers among men but has limited prognostic biomarkers available for follow up. MicroRNAs (miRNAs) are small non-coding RNAs that regulate expression of their target genes. Accumulating experimental evidence reports differential miRNA expression in PCa, and that miRNAs are actively involved in the pathogenesis and progression of PCa. miRNA and androgen receptor signaling cross-talk is an established factor in PCa pathogenesis. Differential miRNA expression was found between patients with high versus low Gleason scores, and was also observed in patients with biochemical failure, hormone-resistant cancer and in metastasis. Metastasis requires epithelial-mesenchymal transition which shares many cancer stem cell biological characteristics and both are associated with miRNA dysregulation. In the era of personalized medicine, there is a broad spectrum of potential clinical applications of miRNAs. These applications can significantly improve PCa management including their use as diagnostic and/or prognostic markers, or as predictive markers for treatment efficiency. Preliminary evidence demonstrates that miRNAs can also be used for risk stratification. Circulatory miRNAs can serve as non-invasive biomarkers in urine and/or serum of PCa patients. More recently, analysis of miRNAs and circulating tumor cells are gaining significant attention. Moreover, miRNAs represent an attractive new class of therapeutic targets for PCa. Here, we summarize the current knowledge and the future prospects of miRNAs in PCa, their advantages, and potential challenges as tissue and circulating biomarkers. Prostate cancer (PCa) is the most commonly diagnosed cancer among men in western populations. The American Cancer Society estimated 239, 590 new cases and 29, 720 expected deaths in the USA in 2013. One in every six men are at risk of developing PCa during their lifetime (1). Currently, the standard biomarker for PCa diagnosis is prostate-specific antigen (PSA), which has its limitations, leading to the risks of PCa over diagnosis and harmful overtreatment. The prognostic value of PSA is also questionable (2). Stepping into the new epoch of personalized medicine, molecular markers are urgently needed to improve the different aspects of PCa management (3). miRNAs represent an attractive class of emerging biomarkers that can help in this regard (4;5).

Cancer stem cells and tumor metastasis (Review)

Previous studies have shown that tumors can induce angiogenesis and lymphangiogenesis, which plays an important role in promoting hematogenous and lymphogenous spread. In recent years, the cancer stem cell (CSC) theory has emerged as an attractive hypothesis for tumor development and progression. The theory proposes that one small subset of cancer cells has the characteristics of stem cells. These CSCs have the capability of both self-renewal and differentiation into diverse cancer cells, which play a decisive role in maintaining capacity for malignant proliferation, invasion, metastasis, and tumor recurrence. CSCs are involved in tumor metastasis, however, the details, and the possible relationship of CSCs, angiogenesis, lymphangiogenesis, and tumor metastasis is still ambiguous. The aim of this report is to summarize current studies of CSCs and tumor metastasis at the cellular level, with the goal of bringing new insights into understanding the role of CSCs in tumor metastasis.

Ηypoxia-inducible factor-1α, von Hippel-Lindau protein, and heat shock protein expression in ophthalmic pterygium and normal conjunctiva

PURPOSE

Εnhanced expression of transcription factor hypoxia inducible factor HIF-1α is known to play a critical role in the modulation of cell metabolism and survival pathways as well as having stem-cell-like properties. Furthermore, accumulated data reveal the existence of cross-regulation between the oxygen-sensing and heat shock pathways contributing to the adaptation of cells under stressful conditions. Pterygium, a stem cell disorder with premalignant features, has been reported to demonstrate hypoxia. The purpose of this study was to investigate the co-expression patterns of transcription factor HIF-1α and von Hippel Lindau protein (pVHL)--which normally acts to keep levels of HIF-1α activity low under normoxic conditions--in pterygium and normal conjunctival human samples. Additionally, expression of HIF-1α compared to the activation of heat shock proteins (Hsp90, Hsp70, and Hsp27) was studied. Emphasis was placed on the detection of HIF-1α and Hsp90, which associates with and stabilizes HIF-1α to promote its transcriptional activity.

METHODS

Semi-serial paraffin-embedded sections and tissue extracts from pterygium and normal conjunctival samples were studied by immunohistochemistry and western blot analysis, respectively, with the use of specific antibodies. Double labeling immunofluorescence studies on cryostat sections were also included.

RESULTS

Statistically significant increased expression of HIF-1α and Hsps (Hsp90, Hsp70, and Hsp27) in pterygia compared to normal conjunctiva was demonstrated (p<0.05). In contrast, no significant difference was detected for pVHL expression (p>0.05). Immunohistochemical findings revealed nuclear HIF-1α immunoreactivity in all the epithelial layers of 23/32 (71.8%) pterygium tissues. Furthermore, all epithelial layers of the majority (75%) of pterygium samples showed strong cytoplasmic immunoreactivity for Hsp27 while Hsp27 expression was detected in all pterygia (100%) examined. Hsp27 expression was not observed in the superficial layer of goblet cells. In some samples, focal basal epithelial cells exhibited weak Hsp27 expression or were Hsp27 immunonegative. Ιmmunoreactivity of phopsho-Hsp27 showed the same distribution pattern as Hsp27 did. Epithelium of all pterygia (100%) displayed moderate to strong Hsp90 cytoplasmic immunoreactivity. Furthermore, the majority of pterygia, specifically, 30/32 (93.7%) and 27/32 (84.3%) demonstrated, respectively, Hsp70 and pVHL cytoplasmic immunoreactivity. Hsp90, Hsp70, and pVHL immunoreactivity was mainly detected in basal and suprabasal epithelial layers even though strong immunoreactivity in all epithelial layers was also observed in some pterygia. Stroma vessels were immunopositive for Hsps (Hsp90, Hsp70, and Hsp27) and pVHL. A statistically significant correlation between the expression of HIF-1α and the activation status of Hsps (Hsp90, Hsp70, and Hsp27; p<0.05) was observed whereas HIF-1α expression did not correlate with pVHL expression (p>0.05). Double labeling immunofluorescence studies showed nuclear HIF-1α co-localization with cytoplasmic Hsp90 expression in cells distributed in the entire epithelium of pterygia, in contrast to, normal conjunctiva, which exhibited only a few scattered epithelial cells with cytoplasmic HIF-1α expression and basal epithelial cells with Hsp90 expression.

CONCLUSIONS

The upregulation of coordinated activation of HIF-1α and Hsps in pterygium may represent an adaptive process for the survival of cells under stressful conditions. The significance of the association of HIF-1α with Hsp90 with respect to the therapeutic approach of pterygium requires further evaluation.

Tumor-induced STAT3 activation in monocytic myeloid-derived suppressor cells enhances stemness and mesenchymal properties in human pancreatic cancer

Pancreatic cancer (PC) mobilizes myeloid cells from the bone marrow to the tumor where they promote tumor growth and proliferation. Cancer stem cells (CSCs) are a population of tumor cells that are responsible for tumor initiation. Aldehyde dehydrogenase-1 activity in PC identifies CSCs, and its activity has been correlated with poor overall prognosis in human PC. Myeloid cells have been shown to impact tumor stemness, but the impact of immunosuppressive tumor-infiltrating granulocytic and monocytic myeloid-derived suppressor cells (Mo-MDSC) on ALDH1^Bright CSCs and epithelial to mesenchymal transition is not well understood. In this study, we demonstrate that Mo-MDSC (CD11b⁺/Gr1⁺/Ly6G⁻/Ly6C^hi) significantly increase the frequency of ALDH1^Bright CSCs in a mouse model of PC. Additionally, there was significant upregulation of genes associated with epithelial to mesenchymal transition. We also found that human PC converts CD14⁺ peripheral blood monocytes into Mo-MDSC (CD14⁺/HLA-DR^low/−) in vitro, and this transformation is dependent on the activation of the STAT3 pathway. In turn, these Mo-MDSC increase the frequency of ALDH1^Bright CSCs and promote mesenchymal features of tumor cells. Finally, blockade of STAT3 activation reversed the increase in ALDH1^Bright CSCs. These data suggest that the PC tumor microenvironment transforms monocytes to Mo-MDSC by STAT3 activation, and these cells increase the frequency of ALDH1^Bright CSCs. Therefore, targeting STAT3 activation may be an effective therapeutic strategy in targeting CSCs in PC.

Hair curvature: a natural dialectic and review

Although hair forms (straight, curly, wavy, etc.) are present in apparently infinite variations, each fibre can be reduced to a finite sequence of tandem segments of just three types: straight, bent/curly, or twisted. Hair forms can thus be regarded as resulting from genetic pathways that induce, reverse or modulate these basic curvature modes. However, physical interconversions between twists and curls demonstrate that strict one-to-one correspondences between them and their genetic causes do not exist. Current hair-curvature theories do not distinguish between bending and twisting mechanisms. We here introduce a multiple papillary centres (MPC) model which is particularly suitable to explain twisting. The model combines previously known features of hair cross-sectional morphology with partially/completely separated dermal papillae within single follicles, and requires such papillae to induce differential growth rates of hair cortical material in their immediate neighbourhoods. The MPC model can further help to explain other, poorly understood, aspects of hair growth and morphology. Separate bending and twisting mechanisms would be preferentially affected at the major or minor ellipsoidal sides of fibres, respectively, and together they exhaust the possibilities for influencing hair-form phenotypes. As such they suggest dialectic for hair-curvature development. We define a natural-dialectic (ND) which could take advantage of speculative aspects of dialectic, but would verify its input data and results by experimental methods. We use this as a top-down approach to first define routes by which hair bending or twisting may be brought about and then review evidence in support of such routes. In particular we consider the wingless (Wnt) and mammalian target of rapamycin (mTOR) pathways as paradigm pathways for molecular hair bending and twisting mechanisms, respectively. In addition to the Wnt canonical pathway, the Wnt/Ca(2+) and planar cell polarity (PCP) pathways, and others, can explain many alternatives and specific variations of hair bending phenotypes. Mechanisms for hair papilla budding or its division by bisection or fission can explain MPC formation. Epithelial-to-mesenchymal (EMT) and mesenchymal-to-epithelial (MET) transitions, acting in collaboration with epithelial-mesenchymal communications are also considered as mechanisms affecting hair growth and its bending and twisting. These may be treated as sub-mechanisms of an overall development from neural-crest stem cell (NCSC) lineages to differentiated hair follicle (HF) cell types, thus providing a unified framework for hair growth and development.

Tumor microenvironment and metabolism in prostate cancer

Prostate cancer is no longer viewed mostly as a disease of abnormally proliferating epithelial cells, but rather as a disease affecting the complex interactions between the cells of the prostate epithelial compartment and the surrounding stromal compartment in which they live. Indeed, the microenvironment in which tumor cells evolve towards an aggressive phenotype is highly heterogeneous, as it is composed of different cell populations such as endothelial cells, fibroblasts, macrophages, and lymphocytes, either resident or trans-differentiated by bone marrow-derived mesenchymal stem cells recruited at the tumor site. Cancer-associated fibroblasts, the most abundant population within this microenvironment, exert a mandatory role in prostate cancer progression as they metabolically sustain cancer cell survival and growth, recruit inflammatory and immune cells, and promote cancer cells stemness and epithelial mesenchymal transition, thereby favoring metastatic dissemination of aggressive cancers. The interruption of this two-compartment crosstalk, together with the idea that stromal cells are mostly vulnerable, being drug-sensitive, could lead to the development of anticancer therapies that target tumor stromal elements.

Enrichment of cancer stem cell-like cells by culture in alginate gel beads

Cancer stem cells (CSCs) are most likely the reason of cancer reoccurrence and metastasis. For further elucidation of the mechanism underlying the characteristics of CSCs, it is necessary to develop efficient culture systems to culture and expand CSCs. In this study, a three-dimensional (3D) culture system based on alginate gel (ALG) beads was reported to enrich CSCs. Two cell lines derived from different histologic origins were encapsulated in ALG beads respectively and the expansion of CSCs was investigated. Compared with two-dimensional (2D) culture, the proportion of cells with CSC-like phenotypes was significantly increased in ALG beads. Expression levels of CSC-related genes were greater in ALG beads than in 2D culture. The increase of CSC proportion after being cultured within ALG beads was further confirmed by enhanced tumorigenicity in vivo. Moreover, increased metastasis ability and higher anti-cancer drug resistance were also observed in 3D-cultured cells. Furthermore, we found that it was hypoxia, through the upregulation of hypoxia-inducible factors (HIFs) that occurred in ALG beads to induce the increasing of CSC proportion. Therefore, ALG bead was an efficient culture system for CSC enrichment, which might provide a useful platform for CSC research and promote the development of new anti-cancer therapies targeting CSCs.

Molecular biomarkers of cancer stem/progenitor cells associated with progression, metastases, and treatment resistance of aggressive cancers

The validation of novel diagnostic, prognostic, and predictive biomarkers and therapeutic targets in tumor cells is of critical importance for optimizing the choice and efficacy of personalized therapies. Importantly, recent advances have led to the identification of gene-expression signatures in cancer cells, including cancer stem/progenitor cells, in the primary tumors, exosomes, circulating tumor cells (CTC), and disseminated cancer cells at distant metastatic sites. The gene-expression signatures may help to improve the accuracy of diagnosis and predict the therapeutic responses and overall survival of patients with cancer. Potential biomarkers in cancer cells include stem cell-like markers [CD133, aldehyde dehydrogenase (ALDH), CD44, and CD24], growth factors, and their cognate receptors [epidermal growth factor receptor (EGFR), EGFRvIII, and HER2], molecules associated with epithelial-mesenchymal transition (EMT; vimentin, N-cadherin, snail, twist, and Zeb1), regulators of altered metabolism (phosphatidylinositol-3' kinase/Akt/mTOR), and drug resistance (multidrug transporters and macrophage inhibitory cytokine-1). Moreover, different pluripotency-associated transcription factors (Oct3/4, Nanog, Sox2, and Myc) and microRNAs that are involved in the epigenetic reprogramming and acquisition of stem cell-like properties by cancer cells during cancer progression may also be exploited as molecular biomarkers to predict the risk of metastases, systemic treatment resistance, and disease relapse of patients with cancer.

Stratified control of IGF-I expression by hypoxia and stress hormones in osteoblasts

Bone cells respond to the integrated effects of local and systemic regulation. Here we show that hypoxia and the stress hormones PGE2 and glucocorticoid interact in complex ways in osteoblasts, converging on insulin like growth factor I (IGF-I) expression. Whereas hypoxia alone rapidly increased transcription factor HIF activity, it suppressed DNA synthesis, had no significant effects on protein synthesis or alkaline phosphatase activity, and drove discrete changes in a panel of osteoblast mRNAs. Notably, hypoxia increased expression of the acute phase response transcription factor C/EBPδ which can induce IGF-I in response to PGE2, but conversely prevented the stimulatory effect of PGE2 on IGF-I mRNA. However, unlike its effect on C/EBPδ, hypoxia suppressed expression of the obligate osteoblast transcription factor Runx2, which can activate an upstream response element in the IGF-I gene promoter. Hypoxic inhibition of IGF-I and Runx2 were enforced by glucocorticoid, and continued with prolonged exposure. Our studies thus reveal that IGF-I expression is stratified by two critical transcriptional elements in osteoblasts, which are resolved by the individual and combined effects of hypoxic stress and stress hormones. In so doing, hypoxia suppresses Runx2, limits the enhancing influence of PGE2, and interacts with glucocorticoid to reduce IGF-I expression by osteoblasts.

Inhibition of ERN1 modifies the hypoxic regulation of the expression of TP53-related genes in U87 glioma cells

Inhibition of ERN1 (endoplasmic reticulum to nuclei 1), the major signalling pathway of endoplasmic reticulum stress, significantly decreases tumor growth. We have studied the expression of tumor protein 53 (TP53)- related genes such as TOPORS (topoisomerase I binding, arginine/serine-rich, E3 ubiquitin protein ligase), TP53BP1 (TP53 binding protein 1), TP53BP2, SESN1 (sestrin 1), NME6 (non-metastatic cells 6), and ZMAT3 (zinc finger, Matrin-type 3) in glioma cells expressing dominantnegative ERN1 under baseline and hypoxic conditions. We demonstrated that inhibition of ERN1 function in U87 glioma cells resulted in increased expression of RYBP, TP53BP2, and SESN1 genes, but decreased expression of TP53BP1, TOPORS, NME6, and ZMAT3 genes. Moreover, inhibition of ERN1 affected hypoxia-mediated changes in expression of TP53-related genes and their magnitude. Indeed, hypoxia has no effect on expression of TP53BP1 and SESN1 in control cells, while resulted in increased expression of these genes in cells with inhibited ERN1 function. Magnitude of hypoxia-mediated changes in expression levels of RYBP and TP53BP2 was gene specific and more robust in the case of TP53BP2. Hypoxiamediated decrease in expression levels of TOPORS was more prominent if ERN1 was inhibited. Present study demonstrates that fine-tuning of the expression of TP53- associated genes depends upon endoplasmic reticulum stress signaling under normal and hypoxic conditions. Inhibition of ERN1 branch of endoplasmic reticulum stress response correlates with deregulation of p53 signaling and slower tumor growth.

Metformin as an adjuvant drug against pediatric sarcomas: hypoxia limits therapeutic effects of the drug

Metformin, a well-known insulin-sensitizer commonly used for type 2 diabetes therapy, has recently emerged as potentially very attractive drug also in oncology. It is cheap, it is relatively safe and many reports have indicated effects in cancer prevention and therapy. These desirable features are particularly interesting for pediatric sarcomas, a group of rare tumors that have been shown to be dependent on IGF and insulin system for pathogenesis and progression. Metformin exerts anti-mitogenic activity in several cancer histotypes through several molecular mechanisms. In this paper, we analyzed its effects against osteosarcoma, Ewing sarcoma and rhabdomyosarcoma, the three most common pediatric sarcomas. Despite in vitro metformin gave remarkable antiproliferative and chemosensitizing effects both in sensitive and chemoresistant cells, its efficacy was not confirmed against Ewing sarcoma xenografts neither as single agent nor in combination with vincristine. This discrepancy between in vitro and in vivo effects may be due to hypoxia, a common feature of solid tumors. We provide evidences that in hypoxia conditions metformin was not able to activate AMPK and inhibit mTOR signaling, which likely prevents the inhibitory effects of metformin on tumor growth. Thus, although metformin may be considered a useful complement of conventional chemotherapy in normoxia, its therapeutic value in highly hypoxic tumors may be more limited. The impact of hypoxia should be considered when novel therapies are planned for pediatric sarcomas.

Manipulation of autophagy in cancer cells: an innovative strategy to fight drug resistance

Autophagy is a catabolic process activated by stress conditions and nutrient deprivation, to which it reacts by promoting the degradation of damaged organelles and misfolded/aggregated proteins, as well as generating new energetic pools. Paradoxically, in cancer cells, which signal the dangerous microenvironment occurring during clinical therapies, autophagy could promote their proliferation and sustain drug resistance. Special attention is given to autophagy manipulation in order to counteract drug resistance of cancer cells. This article describes the basic properties of autophagy and focuses on the strategies of manipulating it.

VEGF targets the tumour cell

The function of vascular endothelial growth factor (VEGF) in cancer is not limited to angiogenesis and vascular permeability. VEGF-mediated signalling occurs in tumour cells, and this signalling contributes to key aspects of tumorigenesis, including the function of cancer stem cells and tumour initiation. In addition to VEGF receptor tyrosine kinases, the neuropilins are crucial for mediating the effects of VEGF on tumour cells, primarily because of their ability to regulate the function and the trafficking of growth factor receptors and integrins. This has important implications for our understanding of tumour biology and for the development of more effective therapeutic approaches.

The roles of HLH transcription factors in epithelial mesenchymal transition and multiple molecular mechanisms

Epithelial-to-mesenchymal transition (EMT) is presently recognized as an important event and the initiating stage for tumor invasion and metastasis. Several EMT inducers have been identified, among which the big family of helix-loop-helix (HLH) transcription factors are rising as a novel and promising family of proteins in EMT mediation, such as Twist1, Twist2, E47, and HIFs, etc. Due to the variety and complexities of HLH members, the pathways and mechanisms they employ to promote EMT are also complex and characteristic. In this review, we will discuss the roles of various HLH proteins in the regulation and sustenance of the EMT and multiple cellular mechanisms, attempting to provide a novel and broadened view towards the link between HLH proteins and EMT.

Honokiol as a Radiosensitizing Agent for Colorectal cancers

Radioresistance is a frustrating obstacle for patients with colorectal cancers (CRCs) undergoing radiotherapy. There is an urgent need to find an effective agent to increase the sensitivity of CRCs to radiation. Honokiol, an active compound purified from Magnolia, was found to radiosensitize colorectal cancer cells both in vitro and in vivo. However, the mechanisms control important signaling that enhances radiosensitivity is currently unknown. In this study, we have reviewed important signaling pathways that are closely related to radiosensitization, such as cell cycle arrest, tumor angiogenesis, JAK/STAT3 signaling pathway and Mismatch repair. Studies show that honokiol can interfere with these pathways at different levels. With overall analysis, it may bring light on finding the possible mechanism by which honokiol acts as a radiosensitizing agent for CRCs.

Critical research gaps and translational priorities for the successful prevention and treatment of breast cancer

INTRODUCTION

Breast cancer remains a significant scientific, clinical and societal challenge. This gap analysis has reviewed and critically assessed enduring issues and new challenges emerging from recent research, and proposes strategies for translating solutions into practice.

METHODS

More than 100 internationally recognised specialist breast cancer scientists, clinicians and healthcare professionals collaborated to address nine thematic areas: genetics, epigenetics and epidemiology; molecular pathology and cell biology; hormonal influences and endocrine therapy; imaging, detection and screening; current/novel therapies and biomarkers; drug resistance; metastasis, angiogenesis, circulating tumour cells, cancer 'stem' cells; risk and prevention; living with and managing breast cancer and its treatment. The groups developed summary papers through an iterative process which, following further appraisal from experts and patients, were melded into this summary account.

RESULTS

The 10 major gaps identified were: (1) understanding the functions and contextual interactions of genetic and epigenetic changes in normal breast development and during malignant transformation; (2) how to implement sustainable lifestyle changes (diet, exercise and weight) and chemopreventive strategies; (3) the need for tailored screening approaches including clinically actionable tests; (4) enhancing knowledge of molecular drivers behind breast cancer subtypes, progression and metastasis; (5) understanding the molecular mechanisms of tumour heterogeneity, dormancy, de novo or acquired resistance and how to target key nodes in these dynamic processes; (6) developing validated markers for chemosensitivity and radiosensitivity; (7) understanding the optimal duration, sequencing and rational combinations of treatment for improved personalised therapy; (8) validating multimodality imaging biomarkers for minimally invasive diagnosis and monitoring of responses in primary and metastatic disease; (9) developing interventions and support to improve the survivorship experience; (10) a continuing need for clinical material for translational research derived from normal breast, blood, primary, relapsed, metastatic and drug-resistant cancers with expert bioinformatics support to maximise its utility. The proposed infrastructural enablers include enhanced resources to support clinically relevant in vitro and in vivo tumour models; improved access to appropriate, fully annotated clinical samples; extended biomarker discovery, validation and standardisation; and facilitated cross-discipline working.

CONCLUSIONS

With resources to conduct further high-quality targeted research focusing on the gaps identified, increased knowledge translating into improved clinical care should be achievable within five years.

FOXM1 promotes the epithelial to mesenchymal transition by stimulating the transcription of Slug in human breast cancer

The Forkhead Box M1 (FOXM1) transcription factor is involved in tumorigenesis and tumor progression in multiple human carcinomas. In this study, we found that FOXM1 promoted the epithelial to mesenchymal transition (EMT) in human breast cancer. We observed a strong correlation between the expression levels of FOXM1 and the mesenchymal phenotype. Knockdown of FOXM1 inhibited the mesenchymal phenotype, whereas stable overexpression of FOXM1 induced EMT in breast cancer cells. FOXM1 was found to endogenously bind to and stimulate the promoter of Slug that is crucial for EMT progression. The knockdown of Slug abolished the EMT-inducing function of FOXM1. The stable overexpression of FOXM1 promoted metastasis of breast cancer cells in vivo. This study confirmed that FOXM1 promoted EMT in breast cancer cells by stimulating the transcription of EMT-related genes such as Slug.

Anoikis molecular pathways and its role in cancer progression

Anoikis is a programmed cell death induced upon cell detachment from extracellular matrix, behaving as a critical mechanism in preventing adherent-independent cell growth and attachment to an inappropriate matrix, thus avoiding colonizing of distant organs. As anchorage-independent growth and epithelial-mesenchymal transition, two features associated with anoikis resistance, are vital steps during cancer progression and metastatic colonization, the ability of cancer cells to resist anoikis has now attracted main attention from the scientific community. Cancer cells develop anoikis resistance due to several mechanisms, including change in integrins' repertoire allowing them to grow in different niches, activation of a plethora of inside-out pro-survival signals as over-activation of receptors due to sustained autocrine loops, oncogene activation, growth factor receptor overexpression, or mutation/upregulation of key enzymes involved in integrin or growth factor receptor signaling. In addition, tumor microenvironment has also been acknowledged to contribute to anoikis resistance of bystander cancer cells, by modulating matrix stiffness, enhancing oxidative stress, producing pro-survival soluble factors, triggering epithelial-mesenchymal transition and self-renewal ability, as well as leading to metabolic deregulations of cancer cells. All these events help cancer cells to inhibit the apoptosis machinery and sustain pro-survival signals after detachment, counteracting anoikis and constituting promising targets for anti-metastatic pharmacological therapy. This article is part of a Special Section entitled: Cell Death Pathways.

Hypoxia, notch signalling, and prostate cancer

The notch signalling pathway is involved in differentiation, proliferation, angiogenesis, vascular remodelling, and apoptosis. Deregulated expression of notch receptors, ligands, and targets is observed in many solid tumours, including prostate cancer. Hypoxia is a common feature of prostate tumours, leading to increased gene instability, reduced treatment response, and increased tumour aggressiveness. The notch signalling pathway is known to regulate vascular cell fate and is responsive to hypoxia-inducible factors. Evidence to date suggests similar, therapeutically exploitable, behaviour of notch-activated and hypoxic prostate cancer cells.

Epithelial-mesenchymal transition triggers cancer stem cell generation in human thyroid cancer cells

Increasing evidence has shown that cancer stem cells or tumor initiating cells are the 'root cause' of malignant cancers. However, the exact origin of cancer stem cells still remains obscure in thyroid research. EMT has been implicated in the initiation and conversion of early-stage tumors into invasive malignancies and is associated with the stemness of cancer cells. Based on these facts, a new hypothesis was suggested that EMT induces cancer stem cell generation and tumor progression in human thyroid cancer cells in vitro. In the present study, FTC133 cells identified as EMT-negative cells were used for EMT induction by HIF‑1α transfection. Overexpression of HIF-1α induced FTC133 cells to undergo EMT, downregulated the epithelial markers E-cadherin, upregulated the mesenchymal marker vimentin, and associated with highly invasive and metastatic properties. Most importantly, the induction of EMT promoted the stem-like side population cell proportion in the FTC133 cells. These results indicate that EMT induction promotes CSC traits and cell proportions in the thyroid cancer cells, which implies that EMT could induce cancer stem cell generation and tumor progression in thyroid cancers. Further understanding of the role of EMT and cancer stem cells in cancer progression may reveal new targets for the prevention or therapy of thyroid cancers.