Gastric cancer stem-like cells possess higher capability of invasion and metastasis in association with a mesenchymal transition phenotype

Gastric Cancer Mesenchymal Stem Cells Trigger Endothelial Cell Functional Changes to Promote Cancer Progression

Our previous studies have highlighted the pivotal role of gastric cancer mesenchymal stem cells (GCMSCs) in tumor initiation, progression, and metastasis. In parallel, it is well-documented that endothelial cells (ECs) undergo functional alterations in response to challenging tumor microenvironment. This study aims to elucidate whether functional changes in ECs might be induced by GCMSCs and thus influence cancer progression. Cell proliferation was assessed through CCK-8 and colony formation assays, while cell migration and invasion capabilities were evaluated by wound-healing and Transwell assays. Immunohistochemistry was employed to examine protein distribution and expression levels. Additionally, quantitative analysis of protein and mRNA expression was carried out through Western blotting and qRT-PCR respectively, with gene knockdown achieved using siRNA. Our findings revealed that GCMSCs effectively stimulate cell proliferation, migration, and angiogenesis of human umbilical vein endothelial cells (HUVECs), both in vitro and in vivo. GCMSCs promote the migration and invasion of gastric cancer cells by inducing the expression of Slit2 in HUVECs. Notably, the inhibition of phosphorylated AKT partially mitigates the aforementioned effects. In conclusion, GCMSCs may exert regulatory control over Slit2 expression in ECs via the AKT signaling pathway, thereby inducing functional changes in ECs that promote tumor progression.

The potential contribution of aberrant cathepsin K expression to gastric cancer pathogenesis

The role of cathepsin K (CTSK) expression in the pathogenesis and progression of gastric cancer (GC) remains unclear. Hence, the primary objective of this study is to elucidate the precise expression and biological role of CTSK in GC by employing a combination of bioinformatics analysis and in vitro experiments. Our findings indicated a significant upregulation of CTSK in GC. The bioinformatics analysis revealed that GC patients with a high level of CTSK expression exhibited enrichment of hallmark gene sets associated with angiogenesis, epithelial-mesenchymal transition (EMT), inflammatory response, KRAS signaling up, TNFα signaling via KFκB, IL2-STAT5 signaling, and IL6-JAK-STAT3 signaling. Additionally, these patients demonstrated elevated levels of M2-macrophage infiltration, which was also correlated with a poorer prognosis. The results of in vitro experiments provided confirmation that the over-expression of CTSK leads to an increase in the proliferative and invasive abilities of GC cells. However, further evaluation was necessary to determine the impact of CTSK on the migration capability of these cells. Our findings suggested that CTSK has the potential to facilitate the initiation and progression of GC by augmenting the invasive capacity of GC cells, engaging in tumor-associated EMT, and fostering the establishment of an immunosuppressive tumor microenvironment (TME).

Major Indole Alkaloids in Evodia Rutaecarpa: The Latest Insights and Review of Their Impact on Gastrointestinal Diseases

Evodia rutaecarpa, the near-ripe fruit of Euodia rutaecarpa (Juss.) Benth, Euodia rutaecarpa (Juss.) Benth. var. officinalis (Dode) Huang, or Euodia rutaecarpa (Juss.) Benth. var. bodinieri (Dode) Huang, is a famous herbal medicine with several biological activities and therapeutic values, which has been applied for abdominalgia, abdominal distension, vomiting, and diarrhea as a complementary and alternative therapy in clinic. Indole alkaloids, particularly evodiamine (EVO), rutaecarpine (RUT), and dedhydroevodiamine (DHE), are received rising attention as the major bioactivity compounds in Evodia rutaecarpa. Therefore, this review summarizes the physicochemical properties, pharmacological activities, pharmacokinetics, and therapeutic effects on gastrointestinal diseases of these three indole alkaloids with original literature collected by PubMed, Web of Science Core Collection, and CNKI up to June 2023. Despite sharing the same parent nucleus, EVO, RUT, and DHE have different structural and chemical properties, which result in different advantages of biological effects. In their wide range of pharmacological activities, the anti-migratory activity of RUT is less effective than that of EVO, and the neuroprotection of DHE is significant. Additionally, although DHE has a higher bioavailability, EVO and RUT display better permeabilities within blood-brain barrier. These three indole alkaloids can alleviate gastrointestinal inflammatory in particular, and EVO also has outstanding anti-cancer effect, although clinical trials are still required to further support their therapeutic potential.

Regulation of iron metabolism and ferroptosis in cancer stem cells

The ability of cancer stem cells (CSCs) to self-renew, differentiate, and generate new tumors is a significant contributor to drug resistance, relapse, and metastasis. Therefore, the targeting of CSCs for treatment is particularly important. Recent studies have demonstrated that CSCs are more susceptible to ferroptosis than non-CSCs, indicating that this could be an effective strategy for treating tumors. Ferroptosis is a type of programmed cell death that results from the accumulation of lipid peroxides caused by intracellular iron-mediated processes. CSCs exhibit different molecular characteristics related to iron and lipid metabolism. This study reviews the alterations in iron metabolism, lipid peroxidation, and lipid peroxide scavenging in CSCs, their impact on ferroptosis, and the regulatory mechanisms underlying iron metabolism and ferroptosis. Potential treatment strategies and novel compounds targeting CSC by inducing ferroptosis are also discussed.

Roles of cancer stem cells in gastrointestinal cancers

Cancer stem cells (CSCs) are the main cause of tumor growth, invasion, metastasis and recurrence. Recently, CSCs have been extensively studied to identify CSC-specific surface markers as well as signaling pathways that play key roles in CSCs self-renewal. The involvement of CSCs in the pathogenesis of gastrointestinal (GI) cancers also highlights these cells as a priority target for therapy. The diagnosis, prognosis and treatment of GI cancer have always been a focus of attention. Therefore, the potential application of CSCs in GI cancers is receiving increasing attention. This review summarizes the role of CSCs in GI cancers, focusing on esophageal cancer, gastric cancer, liver cancer, colorectal cancer, and pancreatic cancer. In addition, we propose CSCs as potential targets and therapeutic strategies for the effective treatment of GI cancers, which may provide better guidance for clinical treatment of GI cancers.

Targeting Gastric Cancer Stem Cells to Enhance Treatment Response

Gastric cancer (GC) was the fourth deadliest cancer in the world in 2020, and about 770,000 people died from GC that year. The death of patients with GC is mainly caused by the metastasis, recurrence, and chemotherapy resistance of GC cells. The cancer stem cell theory defines cancer stem cells (CSCs) as a key factor in the metastasis, recurrence, and chemotherapy resistance of cancer. It considers targeting gastric cancer stem cells (GCSCs) to be an effective method for the treatment of GC. For GCSCs, genes or noncoding RNAs are important regulatory factors. Many experimental studies have found that some drugs can target the stemness of gastric cancer by regulating these genes or noncoding RNAs, which may bring new directions for the clinical treatment of gastric cancer. Therefore, this review mainly discusses related genes or noncoding RNAs in GCSCs and drugs that target its stemness, thereby providing some information for the treatment of GC.

Cancer Stem Cells in Tumor Modeling: Challenges and Future Directions

Microfluidic tumors-on-chips models have revolutionized anticancer therapeutic research by creating an ideal microenvironment for cancer cells. The tumor microenvironment (TME) includes various cell types and cancer stem cells (CSCs), which are postulated to regulate the growth, invasion, and migratory behavior of tumor cells. In this review, the biological niches of the TME and cancer cell behavior focusing on the behavior of CSCs are summarized. Conventional cancer models such as three-dimensional cultures and organoid models are reviewed. Opportunities for the incorporation of CSCs with tumors-on-chips are then discussed for creating tumor invasion models. Such models will represent a paradigm shift in the cancer community by allowing oncologists and clinicians to predict better which cancer patients will benefit from chemotherapy treatments.

The transcription factor RUNX2 fuels YAP1 signaling and gastric cancer tumorigenesis

Despite considerable efforts in the detection and treatment of gastric cancer (GC), the underlying mechanism of the progression of GC remains unknown. Our previous work has demonstrated the remarkable role of Runt‐related transcription factor 2 (RUNX2), in fueling the invasion and metastasis of GC. The present study aimed to elucidate the role of RUNX2 in tumorigenesis of GC. We assessed Runx2 expression and its clinical significance via bioinformatic analysis of the Cancer Genome Atlas and Gene Expression Omnibus databases. Roles for Runx2 in self‐renewal and tumorigenesis were examined in vitro and in vivo. Further bioinformatic analysis was applied to study the mechanism of GC progression. We found that Runx2 was highly expressed in the early stage of GC and positively correlated with a poor clinical outcome of patients. Runx2 was also significantly correlated with clinicopathological features, such as Hp infection, new neoplastic events, primary therapeutic outcome, ethnicity, race, and tumor stage. Multivariate analysis revealed that together with Runx2, age, cancer status, M stage, and T stage were independent prognostic factors for the outcome of GC patients. RUNX2 overexpression induced increased anchorage‐independent colony formation, sphere formation, and tumorigenesis in GC cells in vitro and in vivo. Mechanistically, bioinformatic analysis indicated that yes1 associated transcriptional regulator (YAP1) might be a downstream target of RUNX2. Specific knockdown of YAP1 reduced the tumor‐initiating ability of GC cells induced by ectopic Runx2 expression. Our findings support the hypothesis that RUNX2 exerts oncogenic properties via YAP1 regulation, highlighting essential roles for RUNX2 and YAP1 in gastric carcinogenesis and suggesting potential therapeutic targets.

Could gastrointestinal tumor-initiating cells originate from cell-cell fusion in vivo?

Tumor-initiating cells (TICs) or cancer stem cells are believed to be responsible for gastrointestinal tumor initiation, progression, metastasis, and drug resistance. It is hypothesized that gastrointestinal TICs (giTICs) might originate from cell-cell fusion. Here, we systemically evaluate the evidence that supports or opposes the hypothesis of giTIC generation from cell-cell fusion both in vitro and in vivo. We review giTICs that are capable of initiating tumors in vivo with 5000 or fewer in vivo fused cells. Under this restriction, there is currently little evidence demonstrating that giTICs originate from cell-cell fusion in vivo. However, there are many reports showing that tumor generation in vitro occurs with more than 5000 fused cells. In addition, the mechanisms of giTIC generation via cell-cell fusion are poorly understood, and thus, we propose its potential mechanisms of action. We suggest that future research should focus on giTIC origination from cell-cell fusion in vivo, isolation or enrichment of giTICs that have tumor-initiating capabilities with 5000 or less in vivo fused cells, and further clarification of the underlying mechanisms. Our review of the current advances in our understanding of giTIC origination from cell-cell fusion may have significant implications for the understanding of carcinogenesis and future cancer therapeutic strategies targeting giTICs.

Effect of gastric cancer stem cell on gastric cancer invasion, migration and angiogenesis

Purpose: Using the gastric cancer cell line SGC7901 and gastric cancer stem cell (CSC-G), we conducted this study to investigate the role of cancer stem cells in invasion, metastasis and tumor angiogenesis. Methods: Stem cell markers (OCT4, SOX2, C-Myc and Klf4) expression was detected by RT-PCR and Western blotting. The proliferation, migration, invasion abilities, L-OHP and 5-FU resistance, angiogenesis were assessed using in vitro spherical clone formation assays, plate cloning experiments, transwell migration, transwell invasion, drug resistance, scratch-wound migration, ring formation assay, and their tumorigenic and ability were assessed using a tumor formation experiment in mice. Results: Compared with the SGC7901, the expression of Oct4, Sox2, Klf4 and CD44 mRNA was significantly higher in CSC-G, the mRNA relative expression of E-cadherin in CSC-G was lower than SGC7901, while the expression of c-Myc did not significantly change. The proliferation, drug resistance, migration, and invasion abilities were significantly higher in CSC-G, and the tumorigenic ability in mice was also significantly higher. Conclusion: The proliferation, drug resistance, migration, invasion, and tumorigenic abilities of CSC-G significantly were higher than SGC7901. CSC-G plays important roles in proliferation, migration, invasion, and tumorigenicity.

GLI1 activation by non-classical pathway integrin αvβ3/ERK1/2 maintains stem cell-like phenotype of multicellular aggregates in gastric cancer peritoneal metastasis

Peritoneal metastasis is one of the most important causes of postoperative death in patients with gastric cancer, and the exact mechanism remains unclear. The proliferation of multicellular aggregates of exfoliated malignant gastric cells in the abdominal cavity is the focus of current research. However, the mechanism how gastric cancer multicellular aggregates survive remains unclear. In this study, we demonstrated that multicellular aggregates of exfoliated gastric cancer cells in the abdominal cavity expressed a stem cell-Like phenotype. We found that Integrin α_vβ₃ not only mediated adhesion of gastric cancer multicellular aggregates to form independent functional units, but also maintained their stem cell-like phenotype by the non-classical pathway Integrin α_vβ₃/ERK1/2/GLI1. In addition, ERK1/2 directly regulates the transcriptional activity of GLI1. GLI1 is a key effector of the Integrin α_vβ₃ pathway in regulating stem cell-like phenotype in multicellular aggregates. Our data indicates that although there is a crosstalk between the non-classical Integrin α_vβ₃ pathway and the classical Hedgehog pathway, the activation of GLI1 is almost independent of the Hedgehog pathway in multicellular aggregates of gastric cancer cells. Our study provides a basis for blocking GLI1 activity in the prevention and treatment of peritoneal metastases of gastric cancer.

Huaier polysaccharide inhibits the stem-like characteristics of ERα-36high triple negative breast cancer cells via inactivation of the ERα-36 signaling pathway

Triple negative breast cancer (TNBC) is a highly aggressive cancer and lack of targeting therapies. It is believed that the breast cancer stem cells (BCSCs) are responsible for the aggressive characteristics of TNBC. Hence, developing BCSC-targeting agents may provide new therapeutic strategies for the patients. Huaier polysaccharide (HP), an active ingredient extracted from the mushroom Trametes robiniophila Murr, has been widely used in clinical anti-cancer treatments in China. Here we demonstrated that HP could target BCSCs in TNBC cells, resulting in decreased mammosphere formation, downregulated expression of stem-related genes and reduced proportion of aldehyde dehydrogenase positive cells in vitro, and inhibited xenograft tumor formation in vivo. Mechanically, HP markedly reduced the expression of estrogen receptor α-36 (ERα-36), a recently identified subtype of estrogen receptor α, and attenuated ERα-36-mediated activation of AKT/β-catenin signaling in ERα-36^high TNBC cells. This study provides a new insight into the mechanism of HP on BCSC-targeting therapy and new ideas for comprehensive treatment strategies for TNBC.

Distinct biological characterization of the CD44 and CD90 phenotypes of cancer stem cells in gastric cancer cell lines

Recent study implicates that gastric cancer stem cells (CSCs) are capable of generating multiple types of cells to promote tumor growth and heterogeneity important for the development of gastric cancer. However, knowledge is limited regarding the expression and characteristics of marker-positive gastric CSCs. Therefore, gastric CSCs from a series of human gastric cancer cell lines (SNU-5, SNU-16, BGC-823, PAMC-82, MKN-45, and NCI-N87) using four putative CSC surface markers (CD44, CD90, CD133, and epithelial-cell adhesion molecule) were investigated the underlying mechanisms regulating such subpopulations. Only SNU-5 and SNU-16 exhibited independent co-expression of CD44⁺ and CD90⁺, which exhibited spheroid-colony formation in vitro and tumor formation in immunodeficient mice. Functional studies revealed that CD44⁺ cells were more invasive compared with CD90⁺ cells, whereas CD90⁺ cells exhibited higher levels of proliferation than CD44⁺ cells. Furthermore, serial xenotransplantation in mice of CD44⁺/CD90⁺ cells derived from SNU-5 and SNU-16 revealed rapid growth of CD90⁺ cells in subcutaneous lesions and a high metastatic capacity of CD44⁺ cells in the lung. Mechanistic analyses revealed that CD44⁺ cells underwent epithelial-to-mesenchymal transition (EMT) following acquisition of mesenchymal features, whereas CD90⁺ cells enhanced the activation of retinoblastoma phosphorylation at Ser780 and oncogenic cell cycle regulators. The expression of CD44 and CD90 in gastric cancer tissues was associated with distant metastasis and the differentiation state of tumors. These results demonstrated that CD44 and CD90 are specific biomarkers capable of identifying and isolating metastatic and tumorigenic CSCs through their ability to regulate EMT and the cell cycle in gastric cancer cell lines.

Novel Gastric Cancer Stem Cell-Related Marker LINGO2 Is Associated with Cancer Cell Phenotype and Patient Outcome

The expression of leucine-rich repeat and immunoglobulin-like domain-containing nogo receptor-interacting protein 2 (LINGO2) has been reported in Parkinson’s disease; however, its role in other diseases is unknown. Gastric cancer is the second leading cause of cancer death. Cancer stem cells (CSC) are a subpopulation of cancer cells that contribute to the initiation and invasion of cancer. We identified LINGO2 as a CSC-associated protein in gastric cancers both in vitro and in patient-derived tissues. We studied the effect of LINGO2 on cell motility, stemness, tumorigenicity, and angiogenic capacity using cells sorted based on LINGO2 expression and LINGO2-silenced cells. Tissue microarray analysis showed that LINGO2 expression was significantly elevated in advanced gastric cancers. The overall survival of patients expressing high LINGO2 was significantly shorter than that of patients with low LINGO2. Cells expressing high LINGO2 showed elevated cell motility, angiogenic capacity, and tumorigenicity, while LINGO2 silencing reversed these properties. Silencing LINGO2 reduced kinase B (AKT)/extracellular signal-regulated kinase (ERK)/ERK kinase (MEK) phosphorylation and decreased epithelial-mesenchymal transition (EMT)-associated markers—N-Cadherin and Vimentin and stemness-associated markers— POU class 5 homeobox 1 (OCT4) and Indian hedgehog (IHH), and markedly decreased the CD44⁺ population. These indicate the involvement of LINGO2 in gastric cancer initiation and progression by altering cell motility, stemness, and tumorigenicity, suggesting LINGO2 as a putative target for gastric cancer treatment.

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.

AEBP1 promotes epithelial-mesenchymal transition of gastric cancer cells by activating the NF-κB pathway and predicts poor outcome of the patients

Adipocyte enhancer binding protein 1 (AEBP1) is a transcriptional repressor that plays a critical role in regulating adipogenesis. Recent studies have indicated that AEBP1 might function as a candidate oncogene and is overexpressed in several human malignancies. However, the role of AEBP1 in gastric cancer (GC) remains largely unknown. This study aimed to investigate the expression pattern, prognostic significance and biological function of AEBP1 in human gastric cancer and to explore the underlying mechanism. We found that both the mRNA and protein levels of AEBP1 were significantly increased in human GC tissues. Elevated AEBP1 expression was significantly correlated with poor overall survival in patients with both early-stage (Tumor, Node, Metastases (TNM) TNM I and II) and late-stage (TNM III and IV) GC. Silencing AEBP1 markedly suppressed the proliferation, migration, invasion, metastasis and epithelial-mesenchymal transition of GC cells. Moreover, we demonstrated that knockdown of AEBP1 in GC cells led to inhibition of the NF-κB pathway by hampering the degradation of IκBα. Thus, AEBP1 might be served as a promising prognostic indicator and a potential therapeutic target in human GC.

Capillary morphogenesis gene 2 maintains gastric cancer stem-like cell phenotype by activating a Wnt/β-catenin pathway

A growing body of evidence shows that the development and progression of gastric cancer (GC) is mainly associated to the presence of gastric cancer stem-like cells (GCSLCs). However, it is unclear how GCSLC population is maintained. This study aimed to explore the role of capillary morphogenesis gene 2 (CMG2) in GCSLC maintenance and the relevance to GC progression. We found that CMG2 was highly expressed in GC tissues and the expression levels were associated with the invasion depth and lymph node metastasis of GC, and inversely correlated with the survival of GC patients. Sorted CMG2^High GC cells preferentially clustered in CD44^High stem-like cell population, which expressed high levels of stemness-related genes with increased capabilities of self-renewal and tumorigenicity. Depletion of CMG2 gene resulted in reduction of GCSLC population with attenuated stemness and decrease of invasive and metastatic capabilities with subdued epithelial–mesenchymal transition phenotype in GC cells. Mechanistically, CMG2 interacted with LRP6 in GCSLCs to activate a Wnt/β-catenin pathway. Thus, our results demonstrate that CMG2 promotes GC progression by maintaining GCSLCs and can serve as a new prognostic indicator and a target for human GC therapy.

Expressions of glia maturation factor-β by tumor cells and endothelia correlate with neovascularization and poor prognosis in human glioma

Glia maturation factor-β (GMF-β) has been reported to promote glial differentiation, and act as a negative prognostic indicator in certain cancers. However, its roles in glioma progression remain unclear. Since neurogenesis and vasculogenesis were proved to share some common regulators during gliomagenesis, we aim to explore the potential impact of GMF-β on tumor neovascularization and patient survival in glioma. In this study, we first detected GMF-β expression not only in tumor cells but also in microvascular endothelia by double immunohistochemical staining. Both tumoral and endothelial GMF-β expression levels were positively correlated with tumor grade and microvessel density (MVD), while negatively associated with poor prognoses of the patients. Interestingly, multivariate analysis demonstrated that endothelial GMF-β expression level was the only independent predictor of progression-free and overall survival of glioma patients. The results of in vitro angiogenesis assay showed that GMF-β knockdown significantly inhibited tubulogenesis of human U87 glioblastoma cells. Furthermore, GMF-β knockdown suppressed tumor growth and the formation of human-CD31 positive (glioma cell-derived) microvessels in a mouse orthotopic U87 glioma model. Our results demonstrated that GMF-β is an important player in glioma progression via promoting neovascularization. GMF-β may therefore be a novel prognostic marker as well as a potential therapeutic target for glioma.

CBX7 regulates stem cell-like properties of gastric cancer cells via p16 and AKT-NF-κB-miR-21 pathways

Background

Chromobox protein homolog 7 (CBX7), a member of the polycomb group (PcG) family of proteins, is involved in the regulation of cell proliferation and cancer progression. PcG family members, such as BMI, Mel-18, and EZH2, are integral constituents of the polycomb repressive complexes (PRCs) and have been known to regulate cancer stem cell (CSC) phenotype. However, the role of other PRCs’ constituents such as CBX7 in the regulation of CSC phenotype remains largely elusive. This study was to investigate the role of CBX7 in regulating stem cell-like properties of gastric cancer and the underlying mechanisms.

Methods

Firstly, the role of CBX7 in regulating stem cell-like properties of gastric cancer was investigated using sphere formation, Western blot, and xenograft tumor assays. Next, RNA interference and ectopic CBX7 expression were employed to determine the impact of CBX7 on the expression of CSC marker proteins and CSC characteristics. The expression of CBX7, its downstream targets, and stem cell markers were analyzed in gastric stem cell spheres, common cancer cells, and gastric cancer tissues. Finally, the pathways by which CBX7 regulates stem cell-like properties of gastric cancer were explored.

Results

We found that CBX7, a constituent of the polycomb repressive complex 1 (PRC1), plays an important role in maintaining stem cell-like characteristics of gastric cancer cells via the activation of AKT pathway and the downregulation of p16. Spearman rank correlation analysis showed positive correlations among the expression of CBX7 and phospho-AKT (pAKT), stem cell markers OCT-4, and CD133 in gastric cancer tissues. In addition, CBX7 was found to upregulate microRNA-21 (miR-21) via the activation of AKT-NF-κB pathway, and miR-21 contributes to CBX7-mediated CSC characteristics.

Conclusions

CBX7 positively regulates stem cell-like characteristics of gastric cancer cells by inhibiting p16 and activating AKT-NF-κB-miR-21 pathway.

Electronic supplementary material

The online version of this article (10.1186/s13045-018-0562-z) contains supplementary material, which is available to authorized users.

ATG4A promotes tumor metastasis by inducing the epithelial-mesenchymal transition and stem-like properties in gastric cells

The metastasis of tumor cells to distant organs is an ominous feature of gastric cancer. However, the molecular mechanisms underlying the invasion and metastasis of gastric cancer cells remain elusive. In this study, we found that the expression of ATG4A, an autophagy-regulating molecule, was significantly increased in gastric cancer tissues and was significantlycorrelated with the gastric cancer differentiation degree, tumor invasion and lymph node metastasis. ATG4A over-expression significantly promoted gastric cancer cell migration and invasion in vitro and metastasis in vivo, as well as promoted gastric cancer cell stem-like properties and the epithelial-mesenchymal transition (EMT) phenotype. By contrast, ATG4A knockdown inhibited the migration, invasion and metastasis of cancer cells, as well as the stem-like properties and EMT phenotype. Mechanistically, ATG4A promotes gastric cancer cell stem-like properties and the EMT phenotype through the activation of Notch signaling not via autophagy, and using the Notch signaling inhibitor DAPT attenuated the effects of ATG4A on gastric cancer cells. Taken together, these findings demonstrated that ATG4A promotes the metastasis of gastric cancer cells via the Notch signaling pathway, which is an autophagy-independent mechanism.

食管鳞癌干细胞及其耐药机制的研究进展

食管癌(esophageal carcinoma, EC)的全球发病率在恶性肿瘤中位居第8位, 死亡率居第6位, 化疗是EC主要的治疗方法之一, 但化疗药物耐药严重影响了化疗效果, 甚至引起化疗失败, 导致肿瘤复发或远处转移. 肿瘤干细胞(cancer stem cells, CSCs)学说提出CSCs是引起肿瘤对化疗药物耐药的重要原因之一. 本文就食管鳞癌干细胞的生物学特性、分选及化疗耐药的相关机制作一综述.

HIF-1α binding to AEG-1 promoter induced upregulated AEG-1 expression associated with metastasis in ovarian cancer

Ovarian cancer with the highest mortality rate among gynecological malignancies is one of common cancers among female cancer patients. As reported in recent years, AEG‐1 was associated with the occurrence, development, and metastasis of ovarian cancer, but the mechanisms remain unclear. In the current study, invasion capabilities of ovarian cancer OVCAR3 cells were measured by viral infection and transwell assay. Western blot analysis was used to evaluate the expression levels of β‐catenin, E‐cadherin, MMP2, and MMP9. With qRT‐PCR analysis, AEG‐1 and HIF‐1α gene expression were detected. We used luciferase reporter gene to measure AEG‐1 promoter activity under normoxia/hypoxia in OVCAR3 cells. Our work demonstrated that AEG‐1 significantly enhanced invasion capabilities of OVCAR3 cells and the expression levels of β‐catenin, E‐cadherin, MMP2, and MMP9 associated with invasion capabilities of OVCAR3 cells were upregulated. Furthermore, hypoxia enhanced invasion capabilities of OVCAR3 cells and induced AEG‐1 high gene expression, which was reversed by AEG‐1 knockdown lentivirus. HIF‐1α expression upregulation was induced in OVCAR3 cells after hypoxia. HIF‐1α knockdown lentivirus induced downregulated expression of AEG‐1 and invasion capabilities of OVCAR3 cells were also inhibited. Wild‐type AEG‐1 promoter activity under hypoxic conditions was significantly higher than that AEG‐1 mutation under normoxic conditions in the absence of hypoxia response. Our results suggested that HIF‐1α binds to AEG‐1 promoter to upregulate its expression, which was correlated with metastasis in ovarian cancer by inducing the expression of MMP2 and MMP9 as well as inhibiting expression of E‐cadherin and β‐catenin.

Predictive Value of Stemness Factor Sox2 in Gastric Cancer Is Associated with Tumor Location and Stage

Cancer stem cells (CSCs) are thought to be the "root" of cancer. Although stemness-related factors ALDH1A1 and Sox2 have been used as markers to identify gastric CSCs, the expression pattern and significance of these factors in gastric cancer have not been sufficiently demonstrated. In this study, the expressions of ALDH1A1 and Sox2 were detected by immunohistochemistry in 122 gastric cancer specimens. And the correlation between Sox2 or ALDH1A1 expression and clinicopathological parameters and overall survival data were analyzed. The positive rate of ALDH1A1 expression was 60%, but there was no significant difference between survival rates of ALDH1A1-positive and ALDH1A1-negative patients. Sox2 was expressed in 42% of specimens and was associated with poor prognosis of patients (P = 0.015). Stratified analysis showed that Sox2 expression correlated with shorter lifespan only in patients with cardiac gastric cancers (P = 0.002) or stage I or II gastric cancers (P = 0.002); but not in patients with non-cardiac cancers (P = 0.556) or stage III or IV gastric cancers (P = 0.121). Analysis on a database cohort validated the correlation between Sox2 expression and poor prognosis in stage II cancer. Also, expression of Sox2 was associated with lymphnode metastasis in patients with cardiac gastric cancer (P = 0.037). A multivariate analysis revealed that Sox2 was an independent prognostic factor in cardiac gastric cancer. Our results indicate that predictive value of Sox2 in gastric cancer is associated with cardiac cancer location and with early cancer stages (I and II).

Expression of NUAK2 in gastric cancer tissue and its effects on the proliferation of gastric cancer cells

The present study aimed to analyze the expression and effects of NUAK2 in gastric cancer and adjacent normal gastric tissues. The protein expression levels of NUAK2 were detected by western blot analysis. The effects of NUAK2 expression on the proliferation of gastric cancer cells was detected using an MTT and BrdU incorporation assay. Furthermore, the effects of NUAK2 on proliferation and cancer stem cell markers, both protein and microRNA (miRNA), were investigated by western blot analysis and miRNA microarrays, respectively. The results demonstrated that NUAK2 was able to significantly promote the proliferation of SGC-7901 gastric cancer cells. In addition, NUAK2 overexpression decreased the percentage of cells in the G1 phase and increased the percentage of cells in the S phase. Western blot analysis and miRNA microarrays revealed that overexpression of NUAK2 resulted in increased expression levels of proliferation markers, including c-myc, proliferating cell nuclear antigen, cyclin-dependent kinase 2, miRNA 21, and gastric cancer stem cell markers, including aldehyde dehydrogenase 1, CD44 and CD133. In conclusion, NUAK2 expression differed between the tumor and normal gastric tissues. NUAK2 was able to promote the proliferation of gastric cancer cells and regulate their cell cycle. Proliferation and cancer stem cell markers were upregulated by NUAK2 expression. Therefore, the results from the present study suggest that NUAK2 may be a promising target for gastric cancer therapy in the future.

The promotion of the transformation of quiescent gastric cancer stem cells by IL-17 and the underlying mechanisms

Postoperative recurrence and metastasis have crucial roles in the poor prognosis of gastric cancer patients. Previous studies have indicated that gastric cancer originates from cancer stem cells (CSCs), and some investigators have found that a particular subset of CSCs possesses higher metastatic capacity. However, the specific mechanism remains uncertain. In the present study, we aimed to explore the biological functions of the inflammatory cytokine interleukin-17 (IL-17) in gastric cancer metastasis and the distinct IL-17-induced transformation of quiescent gastric CSCs. Our results showed that invasive gastric CSCs were CD26+ and CXCR4+ and were closely associated with increased metastatic ability. The quiescent gastric CSCs, which were CD26- and CXCR4-, were exposed to appropriate concentrations of IL-17; this resulted in the decreased expression of E-cadherin and the increased expression of vimentin and N-cadherin. In addition, the upregulation of IL-17 both in vitro and in vivo resulted in a significant induction of invasion, migration and tumor formation ability in gastric CSCs compared with the control group, which was not treated with IL-17. Further experiments indicated that the activation of the downstream phosphorylated signal transducer and activator of transcription 3 (STAT3) transcription factor pathway was facilitated by IL-17. On the contrary, the downregulation of STAT3 by the specific inhibitor Stattic significantly reversed the IL-17-induced epithelial-mesenchymal transition (EMT)-associated properties of quiescent gastric CSCs. Moreover, tumorigenesis and metastasis were suppressed. Taken together, we suggest that IL-17 is positively correlated with the transformation of quiescent gastric CSCs into invasive gastric CSCs and that targeting IL-17 may emerge as a possible novel therapeutic strategy for gastric cancer.

Molecular classification of gastric cancer: Towards a pathway-driven targeted therapy

Gastric cancer (GC) is the third leading cause of cancer mortality worldwide. Although surgical resection is a potentially curative approach for localized cases of GC, most cases of GC are diagnosed in an advanced, non-curable stage and the response to traditional chemotherapy is limited. Fortunately, recent advances in our understanding of the molecular mechanisms that mediate GC hold great promise for the development of more effective treatment strategies. In this review, an overview of the morphological classification, current treatment approaches, and molecular alterations that have been characterized for GC are provided. In particular, the most recent molecular classification of GC and alterations identified in relevant signaling pathways, including ErbB, VEGF, PI3K/AKT/mTOR, and HGF/MET signaling pathways, are described, as well as inhibitors of these pathways. An overview of the completed and active clinical trials related to these signaling pathways are also summarized. Finally, insights regarding emerging stem cell pathways are described, and may provide additional novel markers for the development of therapeutic agents against GC. The development of more effective agents and the identification of biomarkers that can be used for the diagnosis, prognosis, and individualized therapy for GC patients, have the potential to improve the efficacy, safety, and cost-effectiveness for GC treatments.

Gastric cancer stem cells: evidence, potential markers, and clinical implications

Gastric cancer is a significant global health problem. It is the fifth most common cancer and third leading cause of cancer-related death worldwide (Torre et al. in CA Cancer J Clin 65(2):87-108, 2015). Despite advances in treatment, overall prognosis remains poor, due to tumour relapse and metastasis. There is an urgent need for novel therapeutic approaches to improve clinical outcomes in gastric cancer. The cancer stem cell (CSC) model has been proposed to explain the high rate of relapse and subsequent resistance of cancer to current systemic treatments (Vermeulen et al. in Lancet Oncol 13(2):e83-e89, 2012). CSCs have been identified in many solid malignancies, including gastric cancer, and have significant clinical implications, as targeting the CSC population may be essential in preventing the recurrence and spread of a tumour (Dewi et al. in J Gastroenterol 46(10):1145-1157, 2011). This review seeks to summarise the current evidence for CSC in gastric cancer, with an emphasis on candidate CSC markers, clinical implications, and potential therapeutic approaches.

MicroRNA-183 promotes migration and invasion of CD133(+)/CD326(+) lung adenocarcinoma initiating cells via PTPN4 inhibition

Non-small cell lung cancer (NSCLC) is the most common cancer worldwide and is a leading cause of lung cancer mortality due to early stage metastases. Cancer stem-like cells (CSLCs) or tumor-initiating cells (TICs) are rare subpopulation cells that are responsible for maintaining tumor growth and invasion leading to recurrence and metastasis. Previous studies revealed that miR-183 can mediate the invasiveness and growth of NSCLC. However, the exact role of miR-183 in regulating the biological behavior of CSLCs in NSCLC remains unclear. In the present study, we explored the regulation of protein tyrosine phosphatase non-receptor type 4 (PTPN4) by miR-183 in vitro using luciferase reporter assays, and we further analyzed the effects of miR-183 on the invasiveness of CSLCs in vitro and in vivo using transwell and bioluminescence assays. Following our finding that miR-183 binds to PTPN4 messenger RNA (mRNA) to prevent its translation through the 3'-untranslated region (UTR), we found that overexpression of miR-183 in CSLCs decreased PTPN4 protein levels while inhibition of miR-183 increased PTPN4 protein levels. The suppression of PTPN4 levels in CSLCs by miR-183 paralleled with a significant promotion in their motility in vitro and in vivo, while anti-sense miR-183 increased PTPN4 levels in CSLCs, which paralleled with a significant decrease in their invasiveness. Furthermore, correlation analysis between miR-183 and PTPN4 in clinical samples demonstrated a statistically significant inverse correlation between PTPN4 mRNA levels and miR-183. In brief, our data indicate that miR-183 plays a pro-invasive role by inverse regulation of PTPN4, and this axis may be a new therapeutic target for suppressing the metastatic capability of CSLCs in NSCLC.

STAT3 is Overactivated in Gastric Cancer Stem-Like Cells

Objective

Gastric cancer (GC) is widely associated with chronic inflammation. The pro inflammatory microenvironment provides conditions that disrupt stem/progenitor cell proliferation and differentiation. The signal transducer and activator of transcrip- tion-3 (STAT3) signaling pathway is involved in inflammation and also contributes to the maintenance of embryonic stem cell (ESCs) pluripotency. Here, we have investi- gated the activation status of STAT3 in GC stem-like cells (GCSLCs).

Materials and Methods

In this experimental research, CSLCs derived from the human GC cell line MKN-45 and patient specimens, through spheroid body formation, character- ized and then assayed for the STAT3 transcription factor expression in mRNA and protein level further to its activation.

Results

Spheroid cells showed higher potential for spheroid formation than the pa- rental cells. Furthemore, stemness genes NANOG, c-MYC and SOX-2 were over expressed in spheroids of MKN-45 and in patient samples. In MKN-45 spheroid cells, epithelial mesenchymal transition (EMT) related markers CDH2, SNAIL2, TWIST and VIMENTIN were upregulated (P<0.05), but we observed no change in expression of the E-cadherin epithelial marker. These cells exhibited more resistance to docetaxel (DTX) when compared with parental cells (P<0.05) according to the MTS assay. Al- though immunostaining and Western blotting showed expression of the STAT3 pro- tein in both spheroids and parents, the mRNA level of STAT3 in spheroids was higher than the parents. Nuclear translocation of STAT3 was accompanied by more intensive phospho-STAT3 (p-STAT3) in spheroid structures relative to the parent cells accord- ing to flow cytometry analysis (P<0.05).

Conclusion

The present findings point to STAT3 over activation in GCSLCs. Com- plementary experiments are required to extend the role of STAT3 in stemness fea- tures and invasion properties of GCSCs and to consider the STAT3 pathway for CSC targeted therapy.

Resveratrol Inhibits the Invasion of Glioblastoma-Initiating Cells via Down-Regulation of the PI3K/Akt/NF-κB Signaling Pathway

Invasion and metastasis of glioblastoma-initiating cells (GICs) are thought to be responsible for the progression and recurrence of glioblastoma multiforme (GBM). A safe drug that can be applied during the rest period of temozolomide (TMZ) maintenance cycles would greatly improve the prognosis of GBM patients by inhibiting GIC invasion. Resveratrol (RES) is a natural compound that exhibits anti-invasion properties in multiple tumor cell lines. The current study aimed to evaluate whether RES can inhibit GIC invasion in vitro and in vivo. GICs were identified using CD133 and Nestin immunofluorescence staining and tumorigenesis in non-obese diabetic severe combined immunodeficient (NOD/SCID) mice. Invasive behaviors, including the adhesion, invasion and migration of GICs, were determined by tumor invasive assays in vitro and in vivo. The activity of matrix metalloproteinases (MMPs) was measured by the gelatin zymography assay. Western blotting analysis and immunofluorescence staining were used to determine the expression of signaling effectors in GICs. We demonstrated that RES suppressed the adhesion, invasion and migration of GICs in vitro and in vivo. Moreover, we proved that RES inhibited the invasion of GICs via the inhibition of PI3K/Akt/NF-κB signal transduction and the subsequent suppression of MMP-2 expression.

B7-H1 enhances proliferation ability of gastric cancer stem-like cells as a receptor

Cancer stem-like cells (CSCs) are a rare tumorigenic population with the ability to self-renew in numerous cancer types. Their existence is considered a pivotal contributor to tumor recurrence. B7-H1 is a ligand of inhibitory inducible co-stimulator (ICOS) that is broadly expressed on various human cancers. ICOS acts as a ligand of programmed death-1 (PD-1) on T cells, induces the immune escape of cancer cells and also acts as a receptor mediating anti-apoptotic effects on cancer cells. However, the expression and function of B7-H1 on CSCs is not yet clear. In the present study, gastric cancer samples were collected and the B7-H1 expression in gastric cancer CSCs was detected. Ki67, a proliferation marker, was found to be expressed at a higher rate in B7-H1⁺ CSCs compared with the B7-H1^- counterparts. SGC-7901 cells, a gastric cancer cell line, were cultured in serum-free medium to form sphere cells that possessed stem cell characteristics and could express B7-H1 with the stimulation of interferon-γ. The proliferative ability of sphere cells was enhanced following B7-H1 activation with recombinant PD-1 in vivo and in vitro. This effect could be eliminated by neutralizing B7-H1. Overall, B7-H1 can act as a stimulating receptor for CSCs, and induce CSC proliferation. Blocking B7-H1 on CSCs may possess therapeutic potential for treating gastric cancer.

Transcriptional coexpression network reveals the involvement of varying stem cell features with different dysregulations in different gastric cancer subtypes

Despite the advancements in the cancer therapeutics, gastric cancer ranks as the second most common cancers with high global mortality rate. Integrative functional genomic investigation is a powerful approach to understand the major dysregulations and to identify the potential targets toward the development of targeted therapeutics for various cancers. Intestinal and diffuse type gastric tumors remain the major subtypes and the molecular determinants and drivers of these distinct subtypes remain unidentified. In this investigation, by exploring the network of gene coexpression association in gastric tumors, mRNA expressions of 20,318 genes across 200 gastric tumors were categorized into 21 modules. The genes and the hub genes of the modules show gastric cancer subtype specific expression. The expression patterns of the modules were correlated with intestinal and diffuse subtypes as well as with the differentiation status of gastric tumors. Among these, G1 module has been identified as a major driving force of diffuse type gastric tumors with the features of (i) enriched mesenchymal, mesenchymal stem cell like, and mesenchymal derived multiple lineages, (ii) elevated OCT1 mediated transcription, (iii) involvement of Notch activation, and (iv) reduced polycomb mediated epigenetic repression. G13 module has been identified as key factor in intestinal type gastric tumors and found to have the characteristic features of (i) involvement of embryonic stem cell like properties, (ii) Wnt, MYC and E2F mediated transcription programs, and (iii) involvement of polycomb mediated repression. Thus the differential transcription programs, differential epigenetic regulation and varying stem cell features involved in two major subtypes of gastric cancer were delineated by exploring the gene coexpression network. The identified subtype specific dysregulations could be optimally employed in developing subtype specific therapeutic targeting strategies for gastric cancer.

Genistein-inhibited cancer stem cell-like properties and reduced chemoresistance of gastric cancer

Genistein, the predominant isoflavone found in soy products, has exerted its anticarcinogenic effect in many different tumor types in vitro and in vivo. Accumulating evidence in recent years has strongly indicated the existence of cancer stem cells in gastric cancer. Here, we showed that low doses of genistein (15 µM), extracted from Millettia nitida Benth var hirsutissima Z Wei, inhibit tumor cell self-renewal in two types of gastric cancer cells by colony formation assay and tumor sphere formation assay. Treatment of gastric cancer cells with genistein reduced its chemoresistance to 5-Fu (fluorouracil) and ciplatin. Further results indicated that the reduced chemoresistance may be associated with the inhibition of ABCG2 expression and ERK 1/2 activity. Furthermore, genistein reduced tumor mass in the xenograft model. Together, genistein inhibited gastric cancer stem cell-like properties and reduced its chemoresistance. Our results provide a further rationale and experimental basis for using the genistein to improve treatment of patients with gastric cancer.

Gastric cancer stem cells: therapeutic targets

During the past decade, a growing body of evidence has implied that cancer stem cells (CSCs) play an important role in the development of gastric cancer (GC). The notion that CSCs give rise to GC and may be responsible for invasion, metastasis, and resistance to treatment has profound implications for anti-cancer therapy. Recent major advances in the rapidly evolving field of CSCs have opened novel exciting opportunities for developing CSC-targeted therapies. Discovery of specific markers and signaling pathways in gastric CSCs (GCSCs), with the perfecting of technologies for identification, isolation, and validation of CSCs, may provide the basis for a revolutionary cancer treatment approach based on the eradication of GCSCs. Emerging therapeutic tools based on specific properties and functions of CSCs, including activation of self-renewal signaling pathways, differences in gene expression profiles, and increased activity of telomerase or chemoresistance mechanisms, are developing in parallel with advances in nanotechnology and bioengineering. The addition of GCSC-targeted therapies to current oncological protocols and their complementary application may be the key to successfully fighting GC.

β -Elemene-Attenuated Tumor Angiogenesis by Targeting Notch-1 in Gastric Cancer Stem-Like Cells

Emerging evidence suggests that cancer stem cells are involved in tumor angiogenesis. The Notch signaling pathway is one of the most important regulators of these processes. β-Elemene, a naturally occurring compound extracted from Curcumae Radix, has been used as an antitumor drug for various cancers in China. However, its underlying mechanism in the treatment of gastric cancer remains largely unknown. Here, we report that CD44+ gastric cancer stem-like cells (GCSCs) showed enhanced proliferation capacity compared to their CD44− counterparts, and this proliferation was accompanied by the high expression of Notch-1 (in vitro). These cells were also more superior in spheroid colony formation (in vitro) and tumorigenicity (in vivo) and positively associated with microvessel density (in vivo). β-Elemene was demonstrated to effectively inhibit the viability of GCSCs in a dose-dependent manner, most likely by suppressing Notch-1 (in vitro). β-Elemene also contributed to growth suppression and attenuated the angiogenesis capacity of these cells (in vivo) most likely by interfering with the expression of Notch-1 but not with Dll4. Our findings indicated that GCSCs play an important role in tumor angiogenesis, and Notch-1 is one of the most likely mediators involved in these processes. β-Elemene was effective at attenuating angiogenesis by targeting the GCSCs, which could be regarded as a potential mechanism for its efficacy in gastric cancer management in the future.

Gastric cancer stem cells: a novel therapeutic target

Gastric cancer remains one of the leading causes of global cancer mortality. Multipotent gastric stem cells have been identified in both mouse and human stomachs, and they play an essential role in the self-renewal and homeostasis of gastric mucosa. There are several environmental and genetic factors known to promote gastric cancer. In recent years, numerous in vitro and in vivo studies suggest that gastric cancer may originate from normal stem cells or bone marrow-derived mesenchymal cells, and that gastric tumors contain cancer stem cells. Cancer stem cells are believed to share a common microenvironment with normal niche, which play an important role in gastric cancer and tumor growth. This mini-review presents a brief overview of the recent developments in gastric cancer stem cell research. The knowledge gained by studying cancer stem cells in gastric mucosa will support the development of novel therapeutic strategies for gastric cancer.

Sox2 enhances the tumorigenicity and chemoresistance of cancer stem-like cells derived from gastric cancer

Gastric cancer stem-like cells (GCSCs) have been identified to possess the ability of self-renewal and tumor initiation. However, the mechanisms involved remain largely unknown. Here, we isolated and characterized the GCSCs by side population (SP) sorting procedure and cultured sphere cells (SC) from human gastric cancer cell lines SGC-7901, BGC-823, MGC-803, HGC-27 and MKN-28. The sorting and culture assay revealed that SP cells proliferated in an asymmetric division manner. In addition, SP cells exhibited a higher potential of spheroid colony formation and greater drug resistance than non-SP cells (NSP). Moreover, the SC were found with enhanced capabilities of drug resistance in vitro and tumorigenicity in vivo. Sox2 mRNA and protein was highly and significantly overexpressed in the SP cells and SC. Importantly, downregulation of Sox2 with siRNA obviously reduced spheroid colony formation and doxorubicin efflux, as well as increased apoptosis rate in sphere cells in vitro and suppressed tumorigenicity in vivo. These results suggest that both SP cells and cultured SC enrich with GCSCs and that Sox2 plays a pivotal role in sustaining stem cell properties and might be a potential target for gastric cancer therapy.