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

Morusin suppresses the stemness characteristics of gastric cancer cells induced by hypoxic microenvironment through inhibition of HIF-1α accumulation

Gastric cancer (GC) is a common, life-threatening malignancy that contributes to the global burden of cancer-related mortality, as conventional therapeutic modalities show limited effects on GC. Hence, it is critical to develop novel agents for GC therapy. Morusin, a typical prenylated flavonoid, possesses antitumor effects against various cancers. The present study aimed to demonstrate the inhibitory effect and mechanism of morusin on the stemness characteristics of human GC in vitro under hypoxia and to explore the potential molecular mechanisms. The effects of morusin on cell proliferation and cancer stem cell-like properties of the human GC cell lines SNU-1 and AGS were assessed by MTT assay, colony formation test, qRT-PCR, flow cytometry analysis, and sphere formation test under hypoxia or normoxia condition through in vitro assays. The potential molecular mechanisms underlying the effects of morusin on the stem-cell-like properties of human GC cells in vitro were investigated by qRT-PCR, western blotting assay, and immunofluorescence assay by evaluating the nuclear translocation and expression level of hypoxia-inducible factor-1α (HIF-1α). The results showed that morusin exerted growth inhibitory effects on SNU-1 and AGS cells under hypoxia in vitro. Moreover, the proportions of CD44+/CD24- cells and the sphere formation ability of SNU-1 and AGS reduced in a dose-dependent manner following morusin treatment. The expression levels of stem cell-related genes, namely Nanog, OCT4, SOX2, and HIF-1α, gradually decreased, and the nuclear translocation of the HIF-1α protein was apparently attenuated. HIF-1α overexpression partially reversed the abovementioned effects of morusin. Taken together, morusin could restrain stemness characteristics of GC cells by inhibiting HIF-1α accumulation and nuclear translocation and could serve as a promising compound for GC treatment.

The hypoxia-inducible factor-1α in stemness and resistance to chemotherapy in gastric cancer: Future directions for therapeutic targeting

Hypoxia-inducible factor-1α (HIF-1α) is a crucial mediator of intra-tumoral heterogeneity, tumor progression, and unresponsiveness to therapy in tumors with hypoxia. Gastric tumors, one of the most aggressive tumors in the clinic, are highly enriched in hypoxic niches, and the degree of hypoxia is strongly correlated with poor survival in gastric cancer patients. Stemness and chemoresistance in gastric cancer are the two root causes of poor patient outcomes. Based on the pivotal role of HIF-1α in stemness and chemoresistance in gastric cancer, the interest in identifying critical molecular targets and strategies for surpassing the action of HIF-1α is expanding. Despite that, the understanding of HIF-1α induced signaling in gastric cancer is far from complete, and the development of efficacious HIF-1α inhibitors bears various challenges. Hence, here we review the molecular mechanisms by which HIF-1α signaling stimulates stemness and chemoresistance in gastric cancer, with the clinical efforts and challenges to translate anti-HIF-1α strategies into the clinic.

Prognostic significance of sex determining region Y-box 2, E-cadherin, and vimentin in esophageal squamous cell carcinoma

BACKGROUND

Sex determining region Y-box 2 (SOX2) can promote squamous cell carcinoma (SSC) because it regulates the migration and invasion of several different types of squamous carcinoma cells. However, few studies have examined the prognostic value of SOX2 and its effect on the epithelial-mesenchymal transition (EMT) in esophageal SSC (ESCC), a cancer characterized by high invasion and rapid metastasis.

AIM

To verify the relationship of SOX2 and the EMT in ESCC and determine the prognostic value and significance of SOX2 and protein markers of the EMT in ESCC.

METHODS

One hundred and eighty-five postsurgical ESCC patients were retrospectively examined. Immunohistochemistry was used to detect SOX2, E-cadherin, and vimentin in ESCC tissues. The chi-square test was used to determine the relationships of the expression of these proteins with clinical data. Kaplan-Meier survival curves were used to evaluate factors associated with overall survival (OS).

RESULTS

SOX2 and vimentin had high expression in ESCC tissues and correlated with the depth of local carcinoma invasion. SOX2 expression had positive correlations with tumor size, vimentin expression, and the EMT, and a negative correlation with E-cadherin expression. Expression of SOX2 and vimentin had negative correlations with OS. SOX2 expression was an independent prognostic risk factor for poor OS in patients with ESCC.

CONCLUSION

SOX2 expression was an independent risk factor for OS in patients with ESCC and its expression had a positive correlation with the expression of vimentin, a classic marker of the EMT. SOX2 promoted the migration and invasion of ESCC, and this may related to its effect on vimentin in promoting the EMT.

The HIF-1α as a Potent Inducer of the Hallmarks in Gastric Cancer

Simple Summary

Gastric cancer is one of the most aggressive tumors in the clinic that is resistant to chemotherapy. Gastric tumors are rich in hypoxic niches, and high expression of hypoxia-inducible factor-1α is associated with poor prognosis. Therefore, strategies that target hypoxia-inducible factor-1α signaling may be highly effective in gastric cancer treatment. However, the precise mechanisms by which hypoxia-inducible factor-1α induces tumor hallmarks in gastric cancer are yet unrevealed. Here, we review the role of hypoxia-inducible factor-1α as a potent inducer of the cancer hallmarks in gastric cancer to provide a broad perspective and reveal missing links investigating which may offer new strategies to target hypoxia-inducible factor-1α signaling in gastric cancer.

Abstract

Hypoxia is the principal architect of the topographic heterogeneity in tumors. Hypoxia-inducible factor-1α (HIF-1α) reinforces all hallmarks of cancer and donates cancer cells with more aggressive characteristics at hypoxic niches. HIF-1α potently induces sustained growth factor signaling, angiogenesis, epithelial–mesenchymal transition, and replicative immortality. Hypoxia leads to the selection of cancer cells that evade growth suppressors or apoptotic triggers and deregulates cellular energetics. HIF-1α is also associated with genetic instability, tumor-promoting inflammation, and escape from immunity. Therefore, HIF-1α may be an important therapeutic target in cancer. Despite that, the drug market lacks safe and efficacious anti-HIF-1α molecules, raising the quest for fully unveiling the complex interactome of HIF-1α in cancer to discover more effective strategies. The knowledge gap is even wider in gastric cancer, where the number of studies on hypoxia is relatively low compared to other well-dissected cancers. A comprehensive review of the molecular mechanisms by which HIF-1α induces gastric cancer hallmarks could provide a broad perspective to the investigators and reveal missing links to explore in future studies. Thus, here we review the impact of HIF-1α on the cancer hallmarks with a specific focus on gastric cancer.

A Low Dose Combination of Withaferin A and Caffeic Acid Phenethyl Ester Possesses Anti-Metastatic Potential In Vitro: Molecular Targets and Mechanisms

Simple Summary

Cancer therapy suffers from its high cost and high rate of adverse effects and relapse of the disease. Hence, the new (preferably natural), economic and safer therapeutic as well preventive measures have been on demand and have been subject of priority research. We have, earlier, demonstrated anticancer activity in the extracts of Ashwagandha leaves and propolis. A combination of Wi-A (an active anticancer ingredient in Ashwagandha extract) and CAPE (an active anticancer ingredient in propolis) was earlier shown to offer higher and cancer cell-selective cytotoxicity. In the present study, we report an anti-metastasis activity in the low dose combination of Wi-A and CAPE along with its mechanism of action and propose its use in cancer metastasis treatment.

Abstract

Withaferin A (Wi-A) and Caffeic Acid Phenethyl Ester (CAPE) are the bioactive ingredients of Ashwagandha (Withania somnifera) and propolis, respectively. Both of these natural compounds have been shown to possess anticancer activity. In the present study, we recruited a low dose of each of these compounds and developed a combination that exhibited remarkably potent anti-migratory and anti-angiogenic activities. Extensive molecular analyses including a cDNA array and expression analyses of the specific gene targets demonstrated that such activities are mediated through their effect on cell adhesion/tight junction proteins (Claudins, E-cadherin), inhibition of canonical Wnt/β-catenin signaling pathways and the consequent downregulation of EMT-signaling proteins (Vimentin, MMPs, VEGF and VEGFR) that play a critical role in cancer metastasis. The data supported that this novel combination of Wi-A and CAPE (Wi-ACAPE, containing 0.5 µM of Wi-A and 10 µM of CAPE) may be recruited for the treatment of metastatic and aggressive cancers and, hence, warrant further evaluation by recruiting a variety of experimental and clinical metastatic models.

Extracellular vesicles: General features and usefulness in diagnosis and therapeutic management of colorectal cancer

In the world, among all type of cancers, colorectal cancer (CRC) is the third most commonly diagnosed in males and the second in females. In most of cases, (RP1) patients’ prognosis limitation with malignant tumors can be attributed to delayed diagnosis of the disease. Identification of patients with early-stage disease leads to more effective therapeutic interventions. Therefore, new screening methods and further innovative treatment approaches are mandatory as they may lead to an increase in progression-free and overall survival rates. For the last decade, the interest in extracellular vesicles (EVs) research has exponentially increased as EVs generation appears to be a universal feature of every cell that is strongly involved in many mechanisms of cell-cell communication either in physiological or pathological situations. EVs can cargo biomolecules, such as lipids, proteins, nucleic acids and generate transmission signal through the intercellular transfer of their content. By this mechanism, tumor cells can recruit and modify the adjacent and systemic microenvironment to support further invasion and dissemination. This review intends to cover the most recent literature on the role of EVs production in colorectal normal and cancer tissues. Specific attention is paid to the use of EVs for early CRC diagnosis, follow-up, and prognosis as EVs have come into the spotlight of research as a high potential source of ‘liquid biopsies’. The use of EVs as new targets or nanovectors as drug delivery systems for CRC therapy is also summarized.

Effect of KLF17 overexpression on epithelial-mesenchymal transition of gastric cancer cells

Objective

To investigate Krüppel-like factor 17 (KLF17) expression in normal and gastric cancer tissues and cell lines.

Methods

Levels of KLF17 mRNA and protein in GES-1 normal gastric mucosal cells, and NCI-N87, SGC-7901, BGC-823 and HGC-27 gastric cancer cells were analysed by quantitative polymerase chain reaction (qPCR) and western blot. Differences in KLF17 expression between gastric cancer and adjacent tissues were analysed by qPCR and immunohistochemistry. Invasion/migration effects of KLF17 overexpression in BGC-823 and HGC-27 cells were analysed by wound-healing and Transwell chamber assays. Changes in expression of KLF17 and epithelial–mesenchymal transition (EMT)-related genes (matrix metalloproteinase [MMP]-9, vimentin and E-cadherin) were analysed in BGC-823 and HGC-27 cells before and after transfection using qPCR and western blot. Transforming growth factor (TGF)-β1, Smad family member (Smad)2/3 and phosphorylated-Smad2/3 levels in BGC-823 and HGC-27 cells were assessed by qPCR and western blot.

Results

KLF17 expression was lower in gastric cancer versus adjacent tissues, and in gastric cancer cell lines versus GES-1 normal gastric mucosal cells, and was positively correlated with degree of cancer-cell differentiation. Wound-healing and Transwell assays showed decreased migration and invasion ability of BGC-823 and HGC-27 cells transfected to overexpress KLF17. KLF17 overexpression was associated with decreased MMP-9 and vimentin in BGC-823 and HGC-27 cancer cells, and increased KLF17 and E-cadherin. KLF17 overexpression also resulted in decreased levels of TGF-β1 and p-Smad2/3 in BGC-823 and HGC-27 cancer cells.

Conclusion

KLF17 is poorly expressed in gastric cancer tissues and cell lines. KLF17 overexpression might inhibit EMT via the TGF-β/Smad pathway, thereby reducing gastric cancer cell invasion and migration. Therefore, KLF17 may become a novel target for treating gastric cancer.

The Hypoxia-Long Noncoding RNA Interaction in Solid Cancers

Hypoxia is one of the representative microenvironment features in cancer and is considered to be associated with the dismal prognosis of patients. Hypoxia-driven cellular pathways are largely regulated by hypoxia-inducible factors (HIFs) and notably exert influence on the hallmarks of cancer, such as stemness, angiogenesis, invasion, metastasis, and the resistance towards apoptotic cell death and therapeutic resistance; therefore, hypoxia has been considered as a potential hurdle for cancer therapy. Growing evidence has demonstrated that long noncoding RNAs (lncRNAs) are dysregulated in cancer and take part in gene regulatory networks owing to their various modes of action through interacting with proteins and microRNAs. In this review, we focus attention on the relationship between hypoxia/HIFs and lncRNAs, in company with the possibility of lncRNAs as candidate molecules for controlling cancer.

Mechanisms of the Epithelial-Mesenchymal Transition and Tumor Microenvironment in Helicobacter pylori-Induced Gastric Cancer

Helicobacter pylori (H. pylori) is one of the most common human pathogens, affecting half of the world’s population. Approximately 20% of the infected patients develop gastric ulcers or neoplastic changes in the gastric stroma. An infection also leads to the progression of epithelial–mesenchymal transition within gastric tissue, increasing the probability of gastric cancer development. This paper aims to review the role of H. pylori and its virulence factors in epithelial–mesenchymal transition associated with malignant transformation within the gastric stroma. The reviewed factors included: CagA (cytotoxin-associated gene A) along with induction of cancer stem-cell properties and interaction with YAP (Yes-associated protein pathway), tumor necrosis factor α-inducing protein, Lpp20 lipoprotein, Afadin protein, penicillin-binding protein 1A, microRNA-29a-3p, programmed cell death protein 4, lysosomal-associated protein transmembrane 4β, cancer-associated fibroblasts, heparin-binding epidermal growth factor (HB-EGF), matrix metalloproteinase-7 (MMP-7), and cancer stem cells (CSCs). The review summarizes the most recent findings, providing insight into potential molecular targets and new treatment strategies for gastric cancer.

Shedding New Light on Cancer Metabolism: A Metabolic Tightrope Between Life and Death

Since the earliest findings of Otto Warburg, who discovered the first metabolic differences between lactate production of cancer cells and non-malignant tissues in the 1920s, much time has passed. He explained the increased lactate levels with dysfunctional mitochondria and aerobic glycolysis despite adequate oxygenation. Meanwhile, we came to know that mitochondria remain instead functional in cancer cells; hence, metabolic drift, rather than being linked to dysfunctional mitochondria, was found to be an active act of direct response of cancer cells to cell proliferation and survival signals. This metabolic drift begins with the use of sugars and the full oxidative phosphorylation via the mitochondrial respiratory chain to form CO₂, and it then leads to the formation of lactic acid via partial oxidation. In addition to oncogene-driven metabolic reprogramming, the oncometabolites themselves alter cell signaling and are responsible for differentiation and metastasis of cancer cells. The aberrant metabolism is now considered a major characteristic of cancer within the past 15 years. However, the proliferating anabolic growth of a tumor and its spread to distal sites of the body is not explainable by altered glucose metabolism alone. Since a tumor consists of malignant cells and its tumor microenvironment, it was important for us to understand the bilateral interactions between the primary tumor and its microenvironment and the processes underlying its successful metastasis. We here describe the main metabolic pathways and their implications in tumor progression and metastasis. We also portray that metabolic flexibility determines the fate of the cancer cell and ultimately the patient. This flexibility must be taken into account when deciding on a therapy, since singular cancer therapies only shift the metabolism to a different alternative path and create resistance to the medication used. As with Otto Warburg in his days, we primarily focused on the metabolism of mitochondria when dealing with this scientific question.

MicroRNA-93-5p promotes epithelial-mesenchymal transition in gastric cancer by repressing tumor suppressor AHNAK expression

BACKGROUND

Gastric cancer (GC) is a common cause of cancer-related mortality worldwide, and microRNAs (miRNAs) have been shown to play an important role in GC development. This study aims to explore the effect of microRNA-93-5p (miR-93-5p) on the epithelial-mesenchymal transition (EMT) in GC, via AHNAK and the Wnt signaling pathway.

METHODS

Microarray-based gene expression analysis was performed to identify GC-related differentially expressed miRNAs and genes. Then the expression of the miR-93-5p was examined in GC tissues and GC cell lines. The targeting relationship between miR-93-5p and AHNAK was verified by a dual luciferase reporter gene assay. In an attempt to ascertain the contributory role of miR-93-5p in GC, miR-93-5p mimic or inhibitor, as well as an AHNAK overexpression vector, were introduced to HGC-27 cells. HGC-27 cell migration and invasive ability, and EMT were assayed using Transwell assay and western blot analysis. Regulation of the Wnt signaling pathway was also assessed using TOP/FOP flash luciferase assay.

RESULTS

miR-93-5p was highly expressed in GC tissue samples and cells. Notably, miR-93-5p could target and negatively regulate AHNAK. Down-regulation of miR-93-5p or overexpression of AHNAK could suppress the migration and invasion abilities, in addition to EMT in GC cells via inactivation of the Wnt signaling pathway.

CONCLUSION

Taken together, downregulation of miR-93-5p attenuated GC development via the Wnt signaling pathway by targeting AHNAK. These findings provide an enhanced understanding of miR-93-5p as a therapeutic target for GC treatment.

Foretinib Inhibits Cancer Stemness and Gastric Cancer Cell Proliferation by Decreasing CD44 and c-MET Signaling

Purpose

CD44 isoforms are highly expressed in cancer stem cells, initiating tumor growth and sustaining tumor self-renewal. Among these isoforms, CD44 variant 9 (CD44v9) is overexpressed in chronic inflammation-induced cancer. CD44 and the mesenchymal-to-epithelial transition (MET) receptor tyrosine kinase are coactivated in some gastric cancers (GCs). In this study, we characterized MET and CD44 expression and signaling in human GC cell lines and analyzed differences in the susceptibility of these lines to foretinib.

Patients and Methods

We analyzed cell viability and the rate of apoptotic cells using MTS assays and flow cytometry, respectively. Gene and protein expression were assessed by quantitative reverse-transcription polymerase chain reaction (qRT-PCR) and immunoblotting, respectively.

Results

Foretinib treatment resulted in dose-dependent inhibition of growth in c-MET-amplified MKN45 and SNU620 cells with concomitant induction of apoptosis, but not in c-MET-reduced MKN28 and AGS cells. Foretinib treatment also significantly reduced phosphor-c-MET, phosphor-AKT, beta-catenin, and COX-2 protein expression in MKN45 and SNU620 cells. Interestingly, foretinib significantly reduced CD44, CD44v9, COX-2, OCT3/4, CCND1, c-MYC, VEGFA, and HIF-1a gene expression in CD44 and MET coactivated MKN45 cells and increased CD44s gene expression; in contrast, these drugs were only slightly active against SNU620 cells.

Conclusion

The results of this study indicate that foretinib could be a therapeutic agent for the prevention or treatment of GCs positive for CD44v9 and c-MET.

SOX2 promotes hypoxia-induced breast cancer cell migration by inducing NEDD9 expression and subsequent activation of Rac1/HIF-1α signaling

Background

Hypoxia, a major condition associated with the tumor microenvironment, stimulates the migration of cancer cells. SOX2 is a powerful transcription factor that shows higher expression in several cancers, however, its role in hypoxia-induced breast cancer cell migration remains largely elusive.

Methods

The human breast cancer cell lines MDA-MB-231 and MDA-MB-468 were cultured under hypoxic conditions. The cell migration rate was determined using the wound-healing and transwell assays. The protein levels of SOX2, NEDD9 and HIF-1α were evaluated via western blotting analysis. The NEDD9 mRNA levels were evaluated using qPCR. The activation of Rac1 was detected with the pulldown assay. The binding of SOX2 to the NEDD9 promoter was checked using the luciferase reporter assay. We also transfected breast cancer cells with specific siRNA for SOX2, NEDD9 or the Rac1 inactive mutant (T17 N) to investigate the role of SOX2, NEDD9 and Rac1 in the response to hypoxia.

Results

Hypoxia markedly increased SOX2 protein levels in a time-dependent manner. SiRNA-mediated disruption of SOX2 inhibited cell migration under hypoxic conditions. Hypoxia also significantly augmented the NEDD9 mRNA and protein levels. Interestingly, SOX2 is a positive transcriptional regulator of NEDD9. Knockdown of SOX2 inhibited hypoxia-induced NEDD9 mRNA and protein expressions. Furthermore, hypoxia-induced upregulation of Rac1 activity and HIF-1α expression was attenuated by SOX2 or NEDD9 silencing, and Rac1-T17 N abolished HIF-1α expression as well as cell migration in cells subjected to hypoxia.

Conclusions

Our results highlight the essential role of SOX2 in breast cancer cell motility. The upregulation of SOX2 under hypoxic conditions may facilitate NEDD9 transcription and expression, and subsequent activation of Rac1 and HIF-1α expression. This could accelerate breast cancer cell migration.

SOX2 in development and cancer biology

The transcription factor SOX2 is essential for embryonic development and plays a crucial role in maintaining the stemness of embryonic cells and various adult stem cell populations. On the other hand, dysregulation of SOX2 expression is associated with a multitude of cancer types and it has been shown that SOX2 positively affects cancer cell traits such as the capacity to proliferate, migrate, invade and metastasize. Moreover, there is growing evidence that SOX2 mediates resistance towards established cancer therapies and that it is expressed in cancer stem cells. These findings indicate that studying the role of SOX2 in the context of cancer progression could lead to the development of new therapeutic options. In this review, the current knowledge about the role of SOX2 in development, maintenance of stemness, cancer progression and the resistance towards cancer therapies is summarized.

Stoichiogenomics reveal oxygen usage bias, key proteins and pathways associated with stomach cancer

Stomach cancer involves hypoxia-specific microenvironments. Stoichiogenomics explores environmental resource limitation on biological macromolecules in terms of element usages. However, the patterns of oxygen usage by proteins and the ways that proteins adapt to a cancer hypoxia microenvironment are still unknown. Here we compared the oxygen and carbon contents ([C]) between proteomes of stomach cancer (hypoxia) and two stomach glandular cells (normal). Key proteins, genome locations, pathways, and functional dissection associated with stomach cancer were also studied. An association of oxygen content ([O]) and protein expression level was revealed in stomach cancer and stomach glandular cells. For differentially expressed proteins (DEPs), oxygen contents in the up regulated proteins were3.2%higherthan that in the down regulated proteins in stomach cancer. A total of 1,062 DEPs were identified; interestingly none of these proteins were coded on Y chromosome. The up regulated proteins were significantly enriched in pathways including regulation of actin cytoskeleton, cardiac muscle contraction, pathway of progesterone-mediated oocyte maturation, etc. Functional dissection of the up regulated proteins with high oxygen contents showed that most of them were cytoskeleton, cytoskeleton associated proteins, cyclins and signaling proteins in cell cycle progression. Element signature of resource limitation could not be detected in stomach cancer for oxygen, just as what happened in plants and microbes. Unsaved use of oxygen by the highly expressed proteins was adapted to the rapid growth and fast division of the stomach cancer cells. In addition, oxygen usage bias, key proteins and pathways identified in this paper laid a foundation for application of stoichiogenomics in precision medicine.

Quantifying Cancer Epithelial-Mesenchymal Plasticity and its Association with Stemness and Immune Response

Cancer cells can acquire a spectrum of stable hybrid epithelial/mesenchymal (E/M) states during epithelial-mesenchymal transition (EMT). Cells in these hybrid E/M phenotypes often combine epithelial and mesenchymal features and tend to migrate collectively commonly as small clusters. Such collectively migrating cancer cells play a pivotal role in seeding metastases and their presence in cancer patients indicates an adverse prognostic factor. Moreover, cancer cells in hybrid E/M phenotypes tend to be more associated with stemness which endows them with tumor-initiation ability and therapy resistance. Most recently, cells undergoing EMT have been shown to promote immune suppression for better survival. A systematic understanding of the emergence of hybrid E/M phenotypes and the connection of EMT with stemness and immune suppression would contribute to more effective therapeutic strategies. In this review, we first discuss recent efforts combining theoretical and experimental approaches to elucidate mechanisms underlying EMT multi-stability (i.e., the existence of multiple stable phenotypes during EMT) and the properties of hybrid E/M phenotypes. Following we discuss non-cell-autonomous regulation of EMT by cell cooperation and extracellular matrix. Afterwards, we discuss various metrics that can be used to quantify EMT spectrum. We further describe possible mechanisms underlying the formation of clusters of circulating tumor cells. Last but not least, we summarize recent systems biology analysis of the role of EMT in the acquisition of stemness and immune suppression.

ROS Production and Distribution: A New Paradigm to Explain the Differential Effects of X-ray and Carbon Ion Irradiation on Cancer Stem Cell Migration and Invasion

Although conventional radiotherapy promotes the migration/invasion of cancer stem cells (CSCs) under normoxia, carbon ion (C-ion) irradiation actually decreases these processes. Unraveling the mechanisms of this discrepancy, particularly under the hypoxic conditions that pertain in niches where CSCs are preferentially localized, would provide a better understanding of the origins of metastases. Invasion/migration, proteins involved in epithelial-to-mesenchymal transition (EMT), and expression of MMP-2 and HIF-1α were quantified in the CSC subpopulations of two head-and-neck squamous cell carcinoma (HNSCC) cell lines irradiated with X-rays or C-ions. X-rays triggered HNSCC-CSC migration/invasion under normoxia, however this effect was significantly attenuated under hypoxia. C-ions induced fewer of these processes in both oxygenation conditions. The differential response to C-ions was associated with a lack of HIF-1α stabilization, MMP-2 expression, or activation of kinases of the main EMT signaling pathways. Furthermore, we demonstrated a major role of reactive oxygen species (ROS) in the triggering of invasion/migration in response to X-rays. Monte-Carlo simulations demonstrated that HO^● radicals are quantitatively higher after C-ions than after X-rays, however they are very differently distributed within cells. We postulate that the uniform distribution of ROS after X-rays induces the mechanisms leading to invasion/migration, which ROS concentrated in C-ion tracks are unable to trigger.

Mechanisms of Metastasis and Cell Mobility - The Role of Metabolism

Tumour metastasis is responsible for more than 90% of tumour-associated mortality. About one third of breast cancer patients in the early stage develop metastases. The transformation in tumour development referred to as the "metastatic cascade" or "metastatic cycle" is a complex and multi-stage event. While it is generally recognised that epithelial-mesenchymal transformation (EMT) plays a crucial role in cancer progression and metastasis, the metabolic events in this process have received little attention to date. We would therefore like to provide a brief overview here of the influence of the metabolism on the progression and metastasis of tumours.

Hypoxia-induced cancer stemness acquisition is associated with CXCR4 activation by its aberrant promoter demethylation

Background

A hypoxic microenvironment leads to an increase in the invasiveness and the metastatic potential of cancer cells within tumors via the epithelial-mesenchymal transition (EMT) and cancer stemness acquisition. However, hypoxia-induced changes in the expression and function of candidate stem cell markers and their possible molecular mechanism is still not understood.

Methods

Lung cell lines were analyzed in normoxic or hypoxic conditions. For screening among the stem cell markers, a transcriptome analysis using next-generation sequencing was performed. For validation, the EMT and stem cell characteristics were analyzed. To determine whether an epigenetic mechanism was involved, the cell lines were treated with a DNA methyltransferase inhibitor (AZA), and methylation-specific PCR and bisulfite sequencing were performed.

Results

Next-generation sequencing revealed that the CXCR4 expression was significantly higher after the hypoxic condition, which functionally resulted in the EMT and cancer stemness acquisition. The acquisition of the EMT and stemness properties was inhibited by treatment with CXCR4 siRNA. The CXCR4 was activated by either the hypoxic condition or treatment with AZA. The methylation-specific PCR and bisulfite sequencing displayed a decreased CXCR4 promoter methylation in the hypoxic condition.

Conclusions

These results suggest that hypoxia-induced acquisition of cancer stem cell characteristics was associated with CXCR4 activation by its aberrant promoter demethylation.

The Crosstalk between Cancer Stem Cells and Microenvironment Is Critical for Solid Tumor Progression: The Significant Contribution of Extracellular Vesicles

Several evidences nowadays demonstrated the critical role of the microenvironment in regulating cancer stem cells and their involvement in tumor progression. Extracellular vesicles (EVs) are considered as one of the most effective vehicles of information among cells. Accordingly, a number of studies led to the recognition of stem cell-associated EVs as new complexes able to contribute to cell fate determination of either normal or tumor cells. In this review, we aim to highlight an existing bidirectional role of EV-mediated communication—from cancer stem cells to microenvironment and also from microenvironment to cancer stem cells—in the most widespread solid cancers as prostate, breast, lung, and colon tumors.

Priming the seed: Helicobacter pylori alters epithelial cell invasiveness in early gastric carcinogenesis

Helicobacter pylori (H. pylori) infection is a well-established risk factor for the development of gastric cancer (GC), one of the most common and deadliest neoplasms worldwide. H. pylori infection induces chronic inflammation in the gastric mucosa that, in the absence of treatment, may progress through a series of steps to GC. GC is only one of several clinical outcomes associated with this bacterial infection, which may be at least partially attributed to the high genetic variability of H. pylori. The biological mechanisms underlying how and under what circumstances H. pylori alters normal physiological processes remain enigmatic. A key aspect of carcinogenesis is the acquisition of traits that equip preneoplastic cells with the ability to invade. Accumulating evidence implicates H. pylori in the manipulation of cellular and molecular programs that are crucial for conferring cells with invasive capabilities. We present here an overview of the main findings about the involvement of H. pylori in the acquisition of cell invasive behavior, specifically focusing on the epithelial-to-mesenchymal transition, changes in cell polarity, and deregulation of molecules that control extracellular matrix remodeling.

Inhibition of lysyl oxidase expression by dextran sulfate affects invasion and migration of gastric cancer cells

In the present study, the effect of dextran sulfate (DS) on the metastasis and invasion of human gastric cancer cells and its key underlying mechanism were investigated. The levels of hypoxia‑inducible factor 1α (HIF‑1α), transforming growth factor β (TGF‑β) and lysyl oxidase (LOX) expression were evaluated in human gastric cancer and peritumoral tissues by immunohistochemical analysis. Cell proliferation and apoptosis were also examined using the Cell Counting Kit‑8 assay and flow cytometry. The effect of DS on the invasion and migration of BGC‑823 cells was assessed using a Transwell assay. BGC‑823 cells were divided into the control (phosphate‑buffered saline‑treated) and experimental (DS‑treated) groups, and cultured for different times under hypoxic conditions. Subsequently, LOX and TGF‑β expression levels in the cells were measured by immunocytochemistry, immunofluorescence, reverse transcription‑quantitative polymerase chain reaction and western blot analysis. HIF‑1α, TGF‑β and LOX expression levels were significantly higher in human gastric cancer tissues as compared with that in adjacent tissues. DS influenced cell proliferation and apoptosis in a dose‑dependent manner. Furthermore, DS reduced the number of invaded and migrated cells. Under hypoxic conditions, DS reduced HIF‑1α, TGF‑β and LOX expression levels in BGC‑823 cells. After 12 h, the effect of combination of DS and β‑aminopropionitrile (BAPN) on LOX and TGF‑β protein levels was more significant compared with that of DS or BAPN alone. Therefore, DS may inhibit the invasion and migration of human gastric cancer cells under hypoxic conditions by influencing LOX.

Knockdown of A-kinase anchor protein 4 inhibits hypoxia-induced epithelial-to-mesenchymal transition via suppression of the Wnt/β-catenin pathway in human gastric cancer cells

Hypoxia induces epithelial-mesenchymal transition (EMT) in tumorigenesis. A-kinase anchor protein 4 (AKAP4) is a member of AKAPs family and plays a critical role in tumorigenesis. However, the biological role of AKAP4 in gastric cancer remains unknown. Thus, we investigated the effect of AKAP4 on EMT in human gastric cancer cells under hypoxic conditions. Our results showed that AKAP4 expression was significantly upregulated in human gastric cancer cell lines. In addition, silenced expression of hypoxia-inducible factor-1α markedly suppressed AKAP4 expression in gastric cancer cells under hypoxia. Furthermore, knockdown of AKAP4 significantly prevented hypoxia-induced migration, invasion, and EMT process in gastric cancer cells. Mechanistically, knockdown of AKAP4 prevented the activation of the Wnt/β-catenin pathway in gastric cancer cells under hypoxia condition. These findings indicate that knockdown of AKAP4 inhibits hypoxia-induced EMT in human gastric cancer cells, at least in part, via inactivation of the Wnt/β-catenin signaling pathway. It is, therefore, AKAP4 may be a potential therapeutic target for the treatment of gastric cancer.

LDH-Apromotes epithelial-mesenchymal transition by upregulating ZEB2 in intestinal-type gastric cancer

Introduction

Epithelial-mesenchymal transition (EMT) is regarded as a crucial process of invasion and metastasis, which contribute greatly to cancer-related relapse and death. Based on research results that hypoxia can trigger gastric cancer EMT and decreasing lactate production can selectively kill hypoxic cancer cells, we infer that lactate dehydrogenase A (LDH-A) transforming pyruvate into lactate is at least in part responsible for poor prognosis of gastric cancer.

Materials and methods

We used siRNA to knock down LDH-A in intestinal-type gastric cancer (ITGC) cell lines SGC7901 and BGC823. Western blot and RT-PCR were applied to detect mRNA and protein expression of EMT-related genes, respectively. Transwell invasion assay and migration assay were applied to study invasive and migratory abilities, respectively. Survival analysis was used to evaluate prognostic values.

Results and conclusion

The results of in vitro experiment demonstrated that LDH-A facilitates ITGC cells’ invasion and migration by upregulating ZEB2. The positive correlation between LDH-A and ZEB2 was verified in 371 ITGC specimens. Survival analysis indicated that co-expression of LDH-A/ZEB2 had synergetic power to predict overall survival. Thus, we conclude that the close relationship between LDH-A and ZEB2 may offer a potential therapeutic strategy for ITGC.

The dark side of SOX2: cancer - a comprehensive overview

The pluripotency-associated transcription factor SOX2 is essential during mammalian embryogenesis and later in life, but SOX2 expression can also be highly detrimental. Over the past 10 years, SOX2 has been shown to be expressed in at least 25 different cancers. This review provides a comprehensive overview of the roles of SOX2 in cancer and focuses on two broad topics. The first delves into the expression and function of SOX2 in cancer focusing on the connection between SOX2 levels and tumor grade as well as patient survival. As part of this discussion, we address the developing connection between SOX2 expression and tumor drug resistance. We also call attention to an under-appreciated property of SOX2, its levels in actively proliferating tumor cells appear to be optimized to maximize tumor growth - too little or too much SOX2 dramatically alters tumor growth. The second topic of this review focuses on the exquisite array of molecular mechanisms that control the expression and transcriptional activity of SOX2. In addition to its complex regulation at the transcriptional level, SOX2 expression and activity are controlled carefully by microRNAs, long non-coding RNAs, and post-translational modifications. In the Conclusion and Future Perspectives section, we point out that there are still important unanswered questions. Addressing these questions is expected to lead to new insights into the functions of SOX2 in cancer, which will help design novels strategies for more effectively treating some of the most deadly cancers.

Targeting hypoxic response for cancer therapy

Hypoxic tumor microenvironment (HTM) is considered to promote metabolic changes, oncogene activation and epithelial mesenchymal transition, and resistance to chemo- and radio-therapy, all of which are hallmarks of aggressive tumor behavior. Cancer cells within the HTM acquire phenotypic properties that allow them to overcome the lack of energy and nutrients supply within this niche. These phenotypic properties include activation of genes regulating glycolysis, glucose transport, acidosis regulators, angiogenesis, all of which are orchestrated through the activation of the transcription factor, HIF1A, which is an independent marker of poor prognosis. Moreover, during the adaptation to a HTM cancer cells undergo deep changes in mitochondrial functions such as “Warburg effect” and the “reverse Warburg effect”.

This review aims to provide an overview of the characteristics of the HTM, with particular focus on novel therapeutic strategies currently in clinical trials, targeting the adaptive response to hypoxia of cancer cells.

Loss of AMPK activation promotes the invasion and metastasis of pancreatic cancer through an HSF1-dependent pathway

Pancreatic ductal adenocarcinoma (PDAC) is a lethal malignancy with a mortality rate that closely parallels its incidence rate, and a better understanding of the molecular and cellular mechanisms associated with the invasion and distant metastasis is required. Heat shock factor 1 (HSF1) is a very highly conserved factor in eukaryotes that regulates the protective heat shock response. Here, we show that HSF1 is abnormally activated in pancreatic cancer. The knockdown of HSF1 impaired the invasion and migration and epithelial–mesenchymal transition (EMT) of pancreatic cancer cells in vitro; however, the upregulation of HSF1 showed the opposite effects. In vivo, the pharmacological inhibition of HSF1 significantly reduced the tumor burden, decreased the incidence of invasion, and prolonged the overall survival of transgenic mice harboring the spontaneous pancreatic cancer. We suggest that the loss of AMP‐activated protein kinase (AMPK) activation mediates the abnormal activation of HSF1 based on the findings that phospho‐HSF1 (p‐HSF1) was highly expressed in human PDAC tissues with a low expression of p‐AMPK and that in those tissues with a high p‐AMPK expression, the level of p‐HSF1 was decreased. The in vivo and in vitro activation of AMPK impaired the activity of HSF1, and HSF1 mediated the effects of the AMPK knockdown‐induced pancreatic cancer invasion and migration. Our study revealed a novel mechanism by which the loss of AMPK activation amplifies the activity of HSF1 to promote the invasion and metastasis of pancreatic cancer.

Mesenchymal Stromal Cell-Derived Interleukin-6 Promotes Epithelial-Mesenchymal Transition and Acquisition of Epithelial Stem-Like Cell Properties in Ameloblastoma Epithelial Cells

Epithelial-mesenchymal transition (EMT), a biological process associated with cancer stem-like or cancer-initiating cell formation, contributes to the invasiveness, metastasis, drug resistance, and recurrence of the malignant tumors; it remains to be determined whether similar processes contribute to the pathogenesis and progression of ameloblastoma (AM), a benign but locally invasive odontogenic neoplasm. Here, we demonstrated that EMT- and stem cell-related genes were expressed in the epithelial islands of the most common histologic variant subtype, the follicular AM. Our results revealed elevated interleukin (IL)-6 signals that were differentially expressed in the stromal compartment of the follicular AM. To explore the stromal effect on tumor pathogenesis, we isolated and characterized both mesenchymal stromal cells (AM-MSCs) and epithelial cells (AM-EpiCs) from follicular AM and demonstrated that, in in vitro culture, AM-MSCs secreted a significantly higher level of IL-6 as compared to the counterpart AM-EpiCs. Furthermore, both in vitro and in vivo studies revealed that exogenous and AM-MSC-derived IL-6 induced the expression of EMT- and stem cell-related genes in AM-EpiCs, whereas such effects were significantly abrogated either by a specific inhibitor of STAT3 or ERK1/2, or by knockdown of Slug gene expression. These findings suggest that AM-MSC-derived IL-6 promotes tumor-stem like cell formation by inducing EMT process in AM-EpiCs through STAT3 and ERK1/2-mediated signaling pathways, implying a role in the etiology and progression of the benign but locally invasive neoplasm. Stem Cells 2017;35:2083-2094.

Epithelial–mesenchymal transition and gastric cancer stem cell

Gastric cancer remains a big health problem in China. Gastric cancer cells contain a small subpopulation of cells that exhibit capabilities of differentiation and tumorigenicity. A putative explanation for ineffective therapy is the presence of cancer stem-like cells. Side population cells, which have cancer stem-like cells’ property, are characterized by the high efflux ability of Hoechst 33342 dye. Side population cells have been isolated from gastric cancer cell lines in previous studies. The epithelial–mesenchymal transition is very important in the invasion and metastasis of epithelial-derived cancers. More and more studies showed that gastric cancer stem-like cells possess high invasive ability and epithelial–mesenchymal transition property. A brief overview of the recent advancements in gastric cancer stem-like cells and epithelial–mesenchymal transition will be helpful for providing novel insight into gastric cancer treatment.

The self-renewal signaling pathways utilized by gastric cancer stem cells

Gastric cancer is a leading cause of cancer-related mortality worldwide. Cancer stem cells are the source of tumor recurrence and metastasis. Self-renewal is a marker of cancer stem cells and also the basis of long-lasting survival and tumor progression. Although the mechanism of gastric cancer stem cell self-renewal is not clear, there are several signaling pathways and environmental factors known to be involved. This mini review describes recent developments in the self-renewal signaling pathway of gastric cancer stem cell research. Advancements made in this field of research will likely support the development of novel therapeutic strategies for gastric cancer.

Relevance of mortalin to cancer cell stemness and cancer therapy

Mortalin/mtHsp70 is a member of Hsp70 family of proteins. Enriched in a large variety of cancers, it has been shown to contribute to the process of carcinogenesis by multiple ways including inactivation of tumor suppressor p53 protein, deregulation of apoptosis and activation of EMT signaling. In this study, we report that upregulation of mortalin contributes to cancer cell stemness. Several cancer cell stemness markers, such as ABCG2, OCT-4, CD133, ALDH1, CD9, MRP1 and connexin were upregulated in mortalin-overexpressing cells that showed higher ability to form spheroids. These cells also showed higher migration, and were less responsive to a variety of cancer chemotherapeutic drugs. Of note, knockdown of mortalin by specific shRNA sensitized these cells to all the drugs used in this study. We report that low doses of anti-mortalin molecules, MKT-077 and CAPE, also caused similar sensitization of cancer cells to chemotherapeutic drugs and hence are potential candidates for effective cancer chemotherapy.

Hypoxia regulates CD44 expression via hypoxia-inducible factor-1α in human gastric cancer cells

Hypoxia induces proliferation and invasion in cancer cells via hypoxia-inducible factor (HIF)-1α. The cell adhesion molecule cluster of differentiation (CD) 44 has been associated with increased cell invasion and metastasis. Whether hypoxia regulates the expression of CD44 in gastric cancer cells remains to be established. In the current study, the effects of hypoxia on HIF-1α and CD44 expression levels in human gastric cell lines SGC-7901 and BGC-823 were evaluated. The cells were cultured in 1% O₂ for 1 week and then treated with 20 nM rapamycin for 72 h. Cell viability was evaluated using the Cell Counting kit-8 assay, and cell invasion was detected by the Transwell invasion assay. The protein and messenger (m) RNA expression levels of HIF-1α and CD44 were detected using western blotting and reverse transcription-quantitative polymerase chain reaction, respectively. The results revealed that cell viability and invasion increased under hypoxic conditions, but decreased following rapamycin treatment in SGC-7901 and BGC-823 cells. Hypoxia also increased the protein and mRNA expression levels of HIF-1α and CD44 in these two cell lines. However, this hypoxia-induced increase in HIF-1α and CD44 protein and mRNA expression levels was inhibited by rapamycin. These findings suggest that hypoxia induced the proliferation and invasion of SGC-7901 and BGC-823 cells. Furthermore, CD44 expression levels were potentially associated with HIF-1α expression levels. Therefore, in gastric cancer cells, hypoxia may regulate CD44 expression via HIF-1α in order to promote cell proliferation and invasion.

Cancer Stem Cell Quiescence and Plasticity as Major Challenges in Cancer Therapy

Cells with stem-like properties, tumorigenic potential, and treatment-resistant phenotypes have been identified in many human malignancies. Based on the properties they share with nonneoplastic stem cells or their ability to initiate and propagate tumors in vivo, such cells were designated as cancer stem (stem-like) or tumor initiating/propagating cells. Owing to their implication in treatment resistance, cancer stem cells (CSCs) have been the subject of intense investigation in past years. Comprehension of CSCs' intrinsic properties and mechanisms they develop to survive and even enhance their aggressive phenotype within the hostile conditions of the tumor microenvironment has reoriented therapeutic strategies to fight cancer. This report provides selected examples of malignancies in which the presence of CSCs has been evidenced and briefly discusses methods to identify, isolate, and functionally characterize the CSC subpopulation of cancer cells. Relevant biological targets in CSCs, their link to treatment resistance, proposed targeting strategies, and limitations of these approaches are presented. Two major aspects of CSC physiopathology, namely, relative in vivo quiescence and plasticity in response to microenvironmental cues or treatment, are highlighted. Implications of these findings in the context of the development of new therapies are discussed.

Clinical relevance of the tumor microenvironment and immune escape of oral squamous cell carcinoma

BACKGROUND

Changes in the tumor microenvironment and immune surveillance represent crucial hallmarks of various kinds of cancer, including oral squamous cell carcinoma (OSCC), and a close crosstalk of hypoxia regulating genes, an activation of chemokines and immune cells has been described.

METHODS

A review about the pivotal role of HIF-1, its crosstalk to various cornerstones in OSCC tumorigenesis is presented.

RESULTS

Hypoxia is a frequent event in OSCC and leads to a reprogramming of the cellular metabolism in order to prevent cell death. Hypoxic OSCC cells induce different adaptive changes such as anaerobic glycolysis, pH stabilisation and alterations of the gene and protein expression profile. This complex metabolic program is orchestrated by the hypoxia inducible factor (HIF)-1, the master regulator of early tumor progression. Hypoxia-dependent and -independent alterations in immune surveillance lead to different immune evasion strategies, which are partially mediated by alterations of the tumor cells, changes in the frequency, activity and repertoire of immune cell infiltrates and of soluble and environmental factors of the tumor micromilieu with consecutive generation of an immune escape phenotype, progression of disease and poor clinical outcome of OSCC patients.

CONCLUSIONS

This review focusses on the importance of HIF-1 in the adaption and reprogramming of the metabolic system to reduced oxygen values as well as on the role of the tumor microenvironment for evasion of OSCC from immune recognition and destruction.

Epithelial-to-mesenchymal transition involves triacylglycerol accumulation in DU145 prostate cancer cells

Epithelial to mesenchymal transition (EMT) is a biological process that plays a crucial role in cancer metastasis.