Absence of CD71 transferrin receptor characterizes human gastric adenosquamous carcinoma stem cells

Internalization of transferrin-tagged Myxococcus xanthus encapsulins into mesenchymal stem cells

Currently, various functionalized nanocarrier systems are extensively studied for targeted delivery of drugs, peptides, and nucleic acids. Joining the approaches of genetic and chemical engineering may produce novel carriers for precise targeting different cellular proteins, which is important for both therapy and diagnosis of various pathologies. Here we present the novel nanocontainers based on vectorized genetically encoded Myxococcus xanthus (Mx) encapsulin, confining a fluorescent photoactivatable mCherry (PAmCherry) protein. The shells of such encapsulins were modified using chemical conjugation of human transferrin (Tf) prelabeled with a fluorescein-6 (FAM) maleimide acting as a vector. We demonstrate that the vectorized encapsulin specifically binds to transferrin receptors (TfRs) on the membranes of mesenchymal stromal/stem cells (MSCs) followed by internalization into cells. Two spectrally separated fluorescent signals from Tf-FAM and PAmCherry are clearly distinguishable and co-localized. It is shown that Tf-tagged Mx encapsulins are internalized by MSCs much more efficiently than by fibroblasts. It has been also found that unlabeled Tf effectively competes with the conjugated Mx-Tf-FAM formulations. That indicates the conjugate internalization into cells by Tf-TfR endocytosis pathway. The developed nanoplatform can be used as an alternative to conventional nanocarriers for targeted delivery of, e.g., genetic material to MSCs.

Overexpressed transferrin receptor implied poor prognosis and relapse in gastrointestinal stromal tumors

Ferroptosis, as a novel-induced programmed cell death, plays critical roles in the pathogenesis of cancers. However, the promising biomarkers of ferroptosis in gastrointestinal stromal tumor (GIST) remain to be elucidated. Herein, the expression of ferroptosis-related genes was analyzed in GIST. Among the 64 ferroptosis-related genes, transferrin receptor (TFRC) expression presented a remarkable upregulation in high-risk patients through Gene Expression Omnibus (GEO) dataset analysis, as well as its significant change after imatinib was treated. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis of TFRC-relevant genes revealed that TFRC expression was closely associated with cell growth pathways and metabolism-related pathways. Furthermore, patients at high risk of recurrence were more likely to exhibit high TFRC expression by immunohistochemistry. Additionally, high TFRC expression indicated an undesirable state of patient relapse, which could serve as a powerful significant independent predictor of recurrence-free survival (RFS). In summary, we systematically summarize the expression characteristics and clinical relevance of TFRC and show that TFRC can be used as a prognostic factor, which can be considered a potential therapeutic target in GIST.

The analysis of the relationship between transferrin receptor 1 (TfR1) and clinical, morphological and immunophenotypic characteristics of breast cancer: retrospective cohort study

Background. Transferrin receptor 1 (TfR1) expression has been identified in a number of malignant tumors. It is noted that its overexpression gives growth advantages to cancer cells. Estimation of transferrin receptor expression in breast cancer (BC) might be an important component in disease prognosis, choice of treatment, also might be an attractive target for targeted therapy. Aim. To evaluate the expression of TfR1 by BC cells and to study its relationship with the clinical, morphological and immunophenotypic characteristics of the tumor. Materials and methods. This study included 82 patients with BC who received treatment at the Blokhin National Medical Research Center of Oncology (Moscow). The expression of TfR1 on primary tumor cells was studied, the relationship of TfR1 with clinical, morphological and immunophenotypic characteristics of BC was analyzed. Immunophenotyping of the primary tumor was performed by the immunohistochemical method (immunofluorescent staining) on cryostat sections. Antibodies to CD71, CD95, CD54, CD29, MUC1, Pgp170 were used. The reaction was evaluated using a luminescent microscope (AXIOSKOP, Germany). The study was dominated by patients with stage IIB 54% and IIIB 21%. Infiltrative ductal BC was diagnosed in 67% (n=55) of patients, infiltrative-lobular in 22% (n=18) of cases, other types in 11.0% (n=9). Results. BC cells expressed TfR1 in most cases (64.4%; n=61). A combination of TfR1 monomorphic expression with MUC1 monomorphic expression (74.4%; n=47) was noted. CD29 is presented both mosaic (38.7%) and monomorphic (51.6%). The Pgp170 antigen was monomorphically observed in 27.5% of cases. As the proportion of TfR+ cells increased, the expression frequency of the adhesion molecule CD54 increased from 10.5 to 33.3%, a positive correlation was established (r=0.293; p=0.008). In the group with TfR1 monomorphic expression, the frequency of tumors expressing the CD95 apoptosis molecule decreased: 25.0% vs 13% (p=0.042). Conclusion. BC cells overexpress TfR1. TfR1 expression is associated with tumor immunophenotype.

Natural compounds as a potential modifier of stem cells renewal: Comparative analysis

Cancer stem cells (CSCs) are indispensable for development, progression, drug resistance, and tumor metastasis. Current cancer-directed interventions target targeting rapidly dividing cancer cells and slow dividing CSCs, which are the root cause of cancer origin and recurrence. The most promising targets include several self-renewal pathways involved in the maintenance and renewal of CSCs, such as the Wnt/β-Catenin, Sonic Hedgehog, Notch, Hippo, Autophagy, and Ferroptosis. In view of safety, natural compounds are coming to the front line of treatment modalities for modifying various signaling pathways simultaneously involved in maintaining CSCs. Therefore, targeting CSCs with natural compounds is a promising approach to treating various types of cancers. In view of this, here we provide a comprehensive update on the current status of natural compounds that effectively tune key self-renewal pathways of CSCs. In addition, we highlighted surface expression markers in several types of cancer. We also emphasize how natural compounds target these self-renewal pathways to reduce therapy resistance and cancer recurrence properties of CSCs, hence providing valuable cancer therapeutic strategies. The inclusion of nutraceuticals is believed to enhance the therapeutic efficacy of current cancer-directed interventions significantly.

The origin of gastric cancer stem cells and their effects on gastric cancer: Novel therapeutic targets for gastric cancer

Gastric cancer (GC) is one of the most prevalent malignancies and the most common causes of cancer-related mortality worldwide. Furthermore, the prognosis of advanced GC remains poor even after surgery combined with chemoradiotherapy. As a small group of cells with unlimited differentiation and self-renewal ability in GC, accumulating evidence shows that GC stem cells (GCSCs) are closely associated with the refractory characteristics of GC, such as drug resistance, recurrence, and metastasis. With the extensive development of research on GCSCs, GCSCs seem to be promising therapeutic targets for GC. However, the relationship between GCSCs and GC is profound and intricate, and its mechanism of action is still under exploration. In this review, we elaborate on the source and key concepts of GCSCs, systematically summarize the role of GCSCs in GC and their underlying mechanisms. Finally, we review the latest information available on the treatment of GC by targeting GCSCs. Thus, this article may provide a theoretical basis for the future development of the novel targets based on GCSCs for the treatment of GC.

Cancer Stem Cells: From an Insight into the Basics to Recent Advances and Therapeutic Targeting

Cancer is characterized by an abnormal growth of the cells in an uncontrolled manner. These cells have the potential to invade and can eventually turn into malignancy, leading to highly fatal forms of tumor. Small subpopulations of cancer cells that are long-lived with the potential of excessive self-renewal and tumor formation are called cancer stem cells (CSCs) or cancer-initiating cells or tumor stem cells. CSCs can be found in tissues, such as breast, brain, lung, liver, ovary, and testis; however, their origin is still a matter of debate. These cells can differentiate and possess self-renewal capacity maintained by numerous intracellular signal transduction pathways, such as the Wnt/β-catenin signaling, Notch signaling, transforming growth factor-β signaling, and Hedgehog signaling. They can also contribute to numerous malignancies and are an important reason for tumor recurrence and metastasis because they are resistant to the known therapeutic strategies that mainly target the bulk of the tumor cells. This review contains collected and compiled information after analyzing published works of the last three decades. The goal was to gather information of recent breakthroughs related to CSCs, strategies to target CSCs' niche (e.g., nanotechnology with tumor biology), and their signaling pathways for cancer therapy. Moreover, the role of metformin, an antidiabetic drug, acting as a chemotherapeutic agent on CSCs by inhibiting cellular transformation and its selective killing is also addressed.

Molecular mechanism of therapeutic approaches for human gastric cancer stem cells

Gastric cancer (GC) is a primary cause of cancer-related mortality worldwide, and even after therapeutic gastrectomy, survival rates remain poor. The presence of gastric cancer stem cells (GCSCs) is thought to be the major reason for resistance to anticancer treatment (chemotherapy or radiotherapy), and for the development of tumor recurrence, epithelial–mesenchymal transition, and metastases. Additionally, GCSCs have the capacity for self-renewal, differentiation, and tumor initiation. They also synthesize antiapoptotic factors, demonstrate higher performance of drug efflux pumps, and display cell plasticity abilities. Moreover, the tumor microenvironment (TME; tumor niche) that surrounds GCSCs contains secreted growth factors and supports angiogenesis and is thus responsible for the maintenance of the growing tumor. However, the genesis of GCSCs is unclear and exploration of the source of GCSCs is essential. In this review, we provide up-to-date information about GCSC-surface/intracellular markers and GCSC-mediated pathways and their role in tumor development. This information will support improved diagnosis, novel therapeutic approaches, and better prognosis using GCSC-targeting agents as a potentially effective treatment choice following surgical resection or in combination with chemotherapy and radiotherapy. To date, most anti-GCSC blockers when used alone have been reported as unsatisfactory anticancer agents. However, when used in combination with adjuvant therapy, treatment can improve. By providing insights into the molecular mechanisms of GCSCs associated with tumors in GC, the aim is to optimize anti-GCSCs molecular approaches for GC therapy in combination with chemotherapy, radiotherapy, or other adjuvant treatment.

Cancer Stem Cells and the Tumor Microenvironment in Gastric Cancer

Gastric cancer (GC) remains one of the leading causes of cancer-related death worldwide. Cancer stem cells (CSCs) might be responsible for tumor initiation, relapse, metastasis and treatment resistance of GC. The tumor microenvironment (TME) comprises tumor cells, immune cells, stromal cells and other extracellular components, which plays a pivotal role in tumor progression and therapy resistance. The properties of CSCs are regulated by cells and extracellular matrix components of the TME in some unique manners. This review will summarize current literature regarding the effects of CSCs and TME on the progression and therapy resistance of GC, while emphasizing the potential for developing successful anti-tumor therapy based on targeting the TME and CSCs.

Human Gastric Cancer Stem Cell (GCSC) Markers Are Prognostic Factors Correlated With Immune Infiltration of Gastric Cancer

The prognosis of patients with gastric cancer (GC) is still unsatisfying. Numerous markers of gastric cancer stem cells (GCSCs) have been identified and were thought to be related to cancer aggressiveness. However, the roles of GCSC markers in GC patients’ prognosis and immune infiltration remain unknown. Expression of GCSC markers was analyzed using Oncomine and Gene Expression Profiling Interactive Analysis (GEPIA). Their associations with clinicopathological parameters were analyzed using UALCAN and LinkedOmics. Alternations and protein expression of GCSC markers were analyzed by cBioPortal and the Human Protein Atlas databases, respectively. The prognostic significance of GCSC markers was evaluated using Kaplan-Meier plotter. Correlations between the expression of GCSC markers and immune infiltration along with biomarkers of tumor-infiltrating immune cells (TIICs) were assessed combined Tumor Immune Estimation Resource and GEPIA. GeneMANIA was used to discover the interactive genes of GCSC markers, and enrichment analysis was performed using Database for Annotation, Visualization, and Integrated Discovery server. We identified six GCSC markers significantly up-expressed in GC, compared with normal stomach tissues. Among them, the overexpression of ICAM1, THY1, and CXCR4 significantly indicated adverse, while EPCAM indicated beneficial clinicopathological features of GC patients. The up-regulation of CXCR4 showed unfavorable prognostic significance, whereas EPCAM and TFRC showed the opposite. The six GCSC markers were all correlated with the infiltration and activation of distinct TIICs. Especially, ICAM1, THY1, and CXCR4 showed strongly positive correlations with tumor-associated macrophages. Besides, chemokine, Toll-like receptor, NF-kappa B, and HIF-1 signaling pathways might be involved in the regulation of GCSC markers on cancer development. This study proposed that GCSC markers might be promising targets of GC treatment to weaken cancer stem-like properties and strengthen anticancer immunity.

Store-Operated Calcium Channels as Drug Target in Gastroesophageal Cancers

Gastroesophageal cancers, including tumors occurring in esophagus and stomach, usually have poor prognosis and lack effective chemotherapeutic drugs for treatment. The association between dysregulated store-operated calcium entry (SOCE), a key intracellular Ca²⁺ signaling pathway and gastroesophageal cancers are emerging. This review summarizes the recent advances in understanding the contribution of SOCE-mediated intracellular Ca²⁺ signaling to gastroesophageal cancers. It assesses the pathophysiological role of each component in SOCE machinery, such as Orais and STIMs in the cancer cell proliferation, migration, and invasion as well as stemness maintenance. Lastly, it discusses efforts towards development of more specific and potent SOCE inhibitors, which may be a new set of chemotherapeutic drugs appearing at the horizon, to provide either targeted therapy or adjuvant treatment to overcome drug resistance for gastroesophageal cancers.

The Transferrin Receptor-Directed CAR for the Therapy of Hematologic Malignancies

As many patients ultimately relapse after chimeric antigen receptor (CAR) T-cell therapy, identification of alternative targets is currently being evaluated. Substantial research efforts are underway to develop new targets. The transferrin receptor (TfR) is prevalently expressed on rapidly proliferating tumor cells and holds the potential to be the alternative target. In order to investigate the efficacy and challenges of TfR-targeting on the CAR-based therapy strategy, we generated a TfR-specific CAR and established the TfR-CAR–modified T cells. To take the advantage of TfR being widely shared by multiple tumors, TfR-CAR T cells were assessed against several TfR⁺ hematological malignant cell lines. Data showed that TfR-CAR T cells were powerfully potent in killing all these types of cells in vitro and in killing T-ALL cells in vivo. These findings suggest that TfR could be a universal target to broaden and improve the therapeutic efficacy of CAR T cells and warrant further efforts to use these cells as an alternative CAR T cell product for the therapy of hematological malignancies.

Clinicopathologic characteristics, survival, and treatments for gastric adenosquamous carcinoma: a population-based study

Background

Gastric adenosquamous carcinoma (gasc) is a rare entity with distinctive characteristics that are not fully understood. In the present study, we evaluated the characteristics of this rare disease.

Methods

The U.S. Surveillance, Epidemiology, and End Results program database was searched to determine the clinicopathologic features, prognostic factors, and treatments for 246 patients with gasc and 42,735 patients with gastric adenocarcinoma (gac).

Results

Relative to gac, gasc is associated with higher proportions of cardia involvement, high-grade tumours, deep tumour invasion, metastatic lymph nodes, and chemotherapy treatment. In patients who underwent potentially curative surgery (pcs), gasc was associated with a higher proportion of radiotherapy use and poorer overall survival (p < 0.001), although no significant difference (p = 0.802) was observed after propensity score matching (psm). Multivariate analysis after psm revealed that the independent prognostic factors for gasc were TNM stage [hazard ratio (hr): 1.512; p = 0.021] and regional nodes examined (hr: 0.588; p = 0.02). In patients with advanced disease, no significant difference in survival between gasc and gac was observed (p = 0.212), although survival was significantly poorer for gasc after psm (p = 0.019). Multivariate analysis after psm revealed that the independent prognostic factors for gasc were invasion depth (hr: 1.303; p = 0.036) and chemotherapy (hr: 0.444; p < 0.001).

Conclusions

Relative to gac, gasc was associated with more aggressive features, although survival outcomes were similar after pcs. Chemotherapy remains a mainstay of treatment for patients with advanced gasc, but its role remains unclear for patients who are undergoing pcs.

Adenosquamous carcinoma of the digestive system: a literature review

Adenosquamous carcinoma (ASC), containing both adenocarcinoma and squamous cell carcinoma components, is rare in the digestive system. Limited data is available on ASC of the digestive system (AS-ASC), and the current evidence is available mainly in the form of case reports and case series. We performed a thorough search of the available literature and compiled a review on the epidemiology, histopathology, pathogenesis, clinical manifestations, diagnosis, treatment, and prognosis of AS-ASC. Non-specific clinical and imaging presentations and low diagnostic accuracy of biopsy lead to difficulties in preoperative diagnosis in a high proportion of patients and high malignancy. The pathogenesis remains obscure. Surgery remains the mainstay of treatment for AS-ASC. The role of chemoradiotherapy as an adjuvant treatment is still inconclusive. Key messages Metastatic linings and the lack of efficacious treatments lead to an unfavorable outcome in AS-ASC patients. Further research could help us understand the pathophysiology of AS-ASCand the unique needs of AS-ASC patients.

Three-Dimensional Culture Systems in Gastric Cancer Research

Gastric cancer (GC), which includes cancer of the esophagus, the oesophagogastric junction, and the stomach fundus, is highly deadly with strong regional influence, Asia being the most affected. GC is often detected at late stages, with 30% of metastatic cases at diagnosis. Many authors have devised models to both unravel the mechanisms of GC development and to evaluate candidate therapeutics. Among these models, 2D-cell cultures are progressively replaced by 3D-cell cultures that recapitulate, much more comprehensively, tumor cellular and genetic heterogeneity, as well as responsiveness to environmental changes, such as exposure to drugs or irradiation. With respect to the specifics of GC, there are high hopes from such model systems, especially with the aim of identifying prognostic markers and novel drug targets.

Increased proportion of the squamous cell carcinoma component is associated with worse survival in resected gastric adenosquamous carcinoma: A STROBE compliant cohort study

For the diagnosis of gastric adenosquamous carcinoma (ASC), discrepancies regarding a rational diagnostic proportion of the squamous cell carcinoma (SCC) component exist among different organizations. Our study aimed to evaluate the impact of the SCC component on the survival of gastric cancer patients and identify the optimal cutoff value for the SCC component necessary for diagnosing gastric ASC.Cases of gastric cancer with an SCC component were obtained from our center and from case reports and series extracted from Medline. Univariate and multivariate analyses were conducted to compare the overall survival between groups and examine the prognostic value of various clinical parameters.We identified 45 qualified cases in published literature and 13 in our center. Forty-two of them were males and 16 females (M: F = 2.6:1). Thirty of them were Asian patients and the rest were mainly from the United States and Europe. The mean age was 61.1 years (median 64 years, range 32-84 years). The average tumor size was 6.9 cm (median 6.0 cm, range 2.0-16.0 cm). The most common location of the cancer was the lower third (39.7%). Although a statistical difference was not achieved, the Kaplan-Meier curve demonstrated that as the proportion of the SCC component in the primary lesion increased, the patients' survival risk increased (P = .489), and the presence of the SCC component in metastatic lymph nodes also increased the risk of survival (P = .259); both of these findings indicated a negative impact of the SCC component on survival. Furthermore, we identified the optimal cutoff for the SCC component as 35% (χ = 6.544, P = .011), which was subsequently validated in a Cox regression model as an independent prognostic factor (P = .026).An increased proportion of the SCC component is associated with worse survival in gastric cancer patients with an SCC component. The optimal cutoff for the proportion of the SCC component necessary for the diagnosis of gastric ASC is 35%.

Molecular Bases of Mechanisms Accounting for Drug Resistance in Gastric Adenocarcinoma

Gastric adenocarcinoma (GAC) is the most common histological type of gastric cancer, the fifth according to the frequency and the third among the deadliest cancers. GAC high mortality is due to a combination of factors, such as silent evolution, late clinical presentation, underlying genetic heterogeneity, and effective mechanisms of chemoresistance (MOCs) that make the available antitumor drugs scarcely useful. MOCs include reduced drug uptake (MOC-1a), enhanced drug efflux (MOC-1b), low proportion of active agents in tumor cells due to impaired pro-drug activation or active drug inactivation (MOC-2), changes in molecular targets sensitive to anticancer drugs (MOC-3), enhanced ability of cancer cells to repair drug-induced DNA damage (MOC-4), decreased function of pro-apoptotic factors versus up-regulation of anti-apoptotic genes (MOC-5), changes in tumor cell microenvironment altering the response to anticancer agents (MOC-6), and phenotypic transformations, including epithelial-mesenchymal transition (EMT) and the appearance of stemness characteristics (MOC-7). This review summarizes updated information regarding the molecular bases accounting for these mechanisms and their impact on the lack of clinical response to the pharmacological treatment currently used in GAC. This knowledge is required to identify novel biomarkers to predict treatment failure and druggable targets, and to develop sensitizing strategies to overcome drug refractoriness in GAC.

The Relevance of Transcription Factors in Gastric and Colorectal Cancer Stem Cells Identification and Eradication

Gastric and colorectal cancers have a high incidence and mortality worldwide. The presence of cancer stem cells (CSCs) within the tumor mass has been indicated as the main reason for tumor relapse, metastasis and therapy resistance, leading to poor overall survival. Thus, the elimination of CSCs became a crucial goal for cancer treatment. The identification of these cells has been performed by using cell-surface markers, a reliable approach, however it lacks specificity and usually differs among tumor type and in some cases even within the same type. In theory, the ideal CSC markers are those that are required to maintain their stemness features. The knowledge that CSCs exhibit characteristics comparable to normal stem cells that could be associated with the expression of similar transcription factors (TFs) including SOX2, OCT4, NANOG, KLF4 and c-Myc, and signaling pathways such as the Wnt/β-catenin, Hedgehog (Hh), Notch and PI3K/AKT/mTOR directed the attention to the use of these similarities to identify and target CSCs in different tumor types. Several studies have demonstrated that the abnormal expression of some TFs and the dysregulation of signaling pathways are associated with tumorigenesis and CSC phenotype. The disclosure of common and appropriate biomarkers for CSCs will provide an incredible tool for cancer prognosis and treatment. Therefore, this review aims to gather the new insights in gastric and colorectal CSC identification specially by using TFs as biomarkers and divulge promising drugs that have been found and tested for targeting these cells.

Cancer Stem Cells and Its Role in Angiogenesis and Vasculogenic Mimicry in Gastrointestinal Cancers

Cancer stem cells (CSCs) are able to promote initiation, survival and maintenance of tumor growth and have been involved in gastrointestinal cancers (GICs) such as esophageal, gastric and colorectal. It is well known that blood supply facilitates cancer progression, recurrence, and metastasis. In this regard, tumor-induced angiogenesis begins with expression of pro-angiogenic molecules such as vascular endothelial growth factor (VEGF), which in turn lead to neovascularization and thus to tumor growth. Another pattern of blood supply is called vasculogenic mimicry (VM). It is a reminiscent of the embryonic vascular network and is carried out by CSCs that have the capability of transdifferentiate and form vascular-tube structures in absence of endothelial cells. In this review, we discuss the role of CSCs in angiogenesis and VM, since these mechanisms represent a source of tumor nutrition, oxygenation, metabolic interchange and facilitate metastasis. Identification of CSCs mechanisms involved in angiogenesis and VM could help to address therapeutics for GICs.

Targeting cancer stem cell pathways for cancer therapy

Since cancer stem cells (CSCs) were first identified in leukemia in 1994, they have been considered promising therapeutic targets for cancer therapy. These cells have self-renewal capacity and differentiation potential and contribute to multiple tumor malignancies, such as recurrence, metastasis, heterogeneity, multidrug resistance, and radiation resistance. The biological activities of CSCs are regulated by several pluripotent transcription factors, such as OCT4, Sox2, Nanog, KLF4, and MYC. In addition, many intracellular signaling pathways, such as Wnt, NF-κB (nuclear factor-κB), Notch, Hedgehog, JAK-STAT (Janus kinase/signal transducers and activators of transcription), PI3K/AKT/mTOR (phosphoinositide 3-kinase/AKT/mammalian target of rapamycin), TGF (transforming growth factor)/SMAD, and PPAR (peroxisome proliferator-activated receptor), as well as extracellular factors, such as vascular niches, hypoxia, tumor-associated macrophages, cancer-associated fibroblasts, cancer-associated mesenchymal stem cells, extracellular matrix, and exosomes, have been shown to be very important regulators of CSCs. Molecules, vaccines, antibodies, and CAR-T (chimeric antigen receptor T cell) cells have been developed to specifically target CSCs, and some of these factors are already undergoing clinical trials. This review summarizes the characterization and identification of CSCs, depicts major factors and pathways that regulate CSC development, and discusses potential targeted therapy for CSCs.

TfR1 binding with H-ferritin nanocarrier achieves prognostic diagnosis and enhances the therapeutic efficacy in clinical gastric cancer

H-ferritin (HFn) nanocarrier is emerging as a promising theranostic platform for tumor diagnosis and therapy, which can specifically target tumor cells via binding transferrin receptor 1 (TfR1). This led us to investigate the therapeutic function of TfR1 in GC. The clinical significance of TfR1 was assessed in 178 GC tissues by using a magneto-HFn nanoparticle-based immunohistochemistry method. The therapeutic effects of doxorubicin-loaded HFn nanocarriers (HFn-Dox) were evaluated on TfR1-positive GC patient-derived xenograft (GC-PDX) models. The biological function of TfR1 was investigated through in vitro and in vivo assays. TfR1 was upregulated (73.03%) in GC tissues, and reversely correlated with patient outcome. TfR1-negative sorted cells exhibited tumor-initiating features, which enhanced tumor formation and migration/invasion, whereas TfR1-positive sorted cells showed significant proliferation ability. Knockout of TfR1 in GC cells also enhanced cell invasion. TfR1-deficient cells displayed immune escape by upregulating PD-L1, CXCL9, and CXCL10, when disposed with IFN-γ. Western blot results demonstrated that TfR1-knockout GC cells upregulated Akt and STAT3 signaling. Moreover, in TfR1-positive GC-PDX models, the HFn-Dox group significantly inhibited tumor growth, and increased mouse survival, compared with that of free-Dox group. TfR1 could be a potential prognostic and therapeutic biomarker for GC: (i) TfR1 reversely correlated with patient outcome, and its negative cells possessed tumor-aggressive features; (ii) TfR1-positive cells can be killed by HFn drug nanocarrier. Given the heterogeneity of GC, HFn drug nanocarrier combined with other therapies toward TfR1-negative cells (such as small molecules or immunotherapy) will be a new option for GC treatment.

Gastric Cancer Stem Cells: Current Insights into the Immune Microenvironment and Therapeutic Targets

Gastric cancer (GC) is a leading cause of cancer-related death worldwide. Cancer stem cells (CSCs) are known to be involved in chemotherapy resistance and the development of metastases. Although CSCs harbor self-renewal and tumorigenic abilities, the immune microenvironment surrounding CSCs provides various factors and supports the maintenance of CSC properties. The current review summarizes the accumulating findings regarding the relationship between the immune microenvironment and gastric CSCs (GCSCs), which will support the possibility of developing novel therapeutic strategies for targeting GCSCs.

Cancer stem cells and nanotechnological approaches for eradication

Cancer stem cells (CSCs) are currently known as the main cause of tumor recurrence. After chemotherapy is completed, CSCs proliferate and then differentiate to generate new tumor tissues. Similar to normal stem cells, this non-uniformly distributed cell population in the tumor tissue has self-renewal capacity and is responsible for survival of the tumor and difference in its genetic and metabolic characteristics. Followed by gene instability in CSCs, new phenotypic markers are aberrantly expressed in CSCs subpopulation. Hence, some of the surface markers and metabolic pathways that are upregulated in CSCs may be applied as specific targets for development of diagnostic and therapeutic approaches. In this review article, the distinctive properties of CSCs including signal pathways implicated in self-renewal and surface markers were discussed. Moreover, targeting CSCs based on their specific properties using nanodrugs was reviewed.

Downregulation of TfR1 promotes progression of colorectal cancer via the JAK/STAT pathway

Background: Colorectal cancer (CRC) is one of the most prevalent gastrointestinal malignancies. The incidence of CRC has been rapidly increasing in China. Transferrin receptor 1 (TfR1) is a key regulator of cellular iron homeostasis. Several studies have demonstrated TfR1 overexpression in a variety of human tumors, but the association between TfR1 and CRC remains unclear.

Methods: TfR1 expression was evaluated in six CRC cell lines and tumor tissues. A total of 201 CRC patients were included for immunohistochemistry and 19 pairs of frozen tissues were used for real-time PCR. Cell proliferation, cell cycle, cell migration and invasion, and in vivo carcinogenesis were tested after downregulation of TfR1 by lentivirus. Protein microarray and Western blot analyses were used to explore the underlying mechanisms of TfR1 in CRC.

Results: TfR1 expression was higher in CRC tissues than in normal tissues (57.2% vs 22.9%, P＜0.001). TfR1 expression was obviously higher in CRC tissues with well differentiation (P＝0.008), no lymph node metastasis (P＝0.002), no distant metastasis (P＝0.006), no vascular invasion (P＜0.001) and early TNM stage (P＝0.013). CRC patients with TfR1-positive expression had a better survival than those with TfR1-negative expression (P＝0.044). Downregulation of TfR1 expression inhibited cell proliferation, promoted cells from G1 phase to S phase and facilitated cell migration and invasion. Knockdown of TfR1 also suppressed tumor growth in BALB/C-nu mice. Protein microarray and Western blot analyses showed that the Janus protein tyrosine kinase/signal transducer and activator of transcription pathway was activated along with downregulation of TfR1 expression.

Conclusion: Though TfR1 was overexpressed in colorectal cancer tissues, there was evidence that downregulation of TfR1 could promote cancer progression.

CD71+ Population Enriched by HPV-E6 Protein Promotes Cancer Aggressiveness and Radioresistance in Cervical Cancer Cells

A subpopulation of cells within tumors has been suggested to possess the ability to initiate tumorigenesis and contribute to resistance to cancer therapy. Identification and isolation of this subpopulation in cancer cells can be achieved by detecting specific cell-surface markers. In this study, flow cytometry analysis revealed an abundant CD71⁺ subpopulation in human papillomavirus (HPV)-positive cervical cancer cells, while limited CD71⁺ cells were detected in HPV-negative cervical cancer cells. Furthermore, ectopic expression of the HPV-E6 protein in HPV-negative C33A cells enriched the CD71⁺subpopulation. The CD71⁺ subpopulation isolated from the C33A cell line and an HPV-E6-overexpressing clone exhibited enhanced transforming ability, proliferation, and resistance to irradiation. In contrast, suppression of CD71 in HPV-positive SiHa cells and the HPV-E6-overexpressing stable clone inhibited spheroid formation and in vitro and in vivo tumorigenicity and sensitized cells to irradiation treatment. CRISPR/Cas9 knockout of CD71 in SiHa cells also produced similar inhibitory effects on tumorigenicity. Double knockout of CD71 and CD55 reversed the oncogenic properties of the HPV-E6-overexpressing clone. These findings suggest that the HPV-E6 protein enriches the subpopulation of CD71⁺cells in cervical cancer, which exhibit cancer stem-like cell properties and are resistant to irradiation treatment. Targeting the CD71⁺ subpopulation in cervical cancer cells with siRNAs or CRISPR/Cas9 may provide new insights for the development of novel therapeutic approaches for treating cervical cancer. IMPLICATIONS: We describe the enrichment of CD71⁺ population by HPV-E6 protein in cervical cancer cells that promotes cancer aggressiveness and resistance to irradiation treatment.

The Role of MicroRNAs in the Regulation of Gastric Cancer Stem Cells: A Meta-Analysis of the Current Status

Gastric cancer (GC) remains one of the major causes of cancer-related mortality worldwide. As for other types of cancers, several limitations to the success of current therapeutic GC treatments may be due to cancer drug resistance that leads to tumor recurrence and metastasis. Increasing evidence suggests that cancer stem cells (CSCs) are among the major causative factors of cancer treatment failure. The research of molecular CSC mechanisms and the regulation of their properties have been intensively studied. To date, molecular gastric cancer stem cell (GCSC) characterization remains largely incomplete. Among the GCSC-targeting approaches to overcome tumor progression, recent studies have focused their attention on microRNA (miRNA). The miRNAs are short non-coding RNAs which play an important role in the regulation of numerous cellular processes through the modulation of their target gene expression. In this review, we summarize and discuss recent findings on the role of miRNAs in GCSC regulation. In addition, we perform a meta-analysis aimed to identify novel miRNAs involved in GCSC homeostasis.

Gastric Cancer Stem Cells Effect on Th17/Treg Balance; A Bench to Beside Perspective

Gastric cancer stem cells (GCSCs), a small population among tumor cells, are responsible for tumor initiation, development, metastasis, and recurrence. They play a crucial role in immune evasion, immunomodulation, and impairment of effector immunity and believed to be emerged to change the balance of the immune system, importantly CD4⁺ T cells in the chronic inflamed tumor site. However, different subtypes of innate and adaptive immune cells are involved in the formation of the immune system in the tumor microenvironment, we would look at T cells in this study. Tumor microenvironment induces differentiation of CD4⁺ T cells into different subsets of T cells, mainly suppressive regulatory T cells (Treg), and T helper 17 (Th17) cells, although their exact role in tumor immunity is still under debate depending on tumor types and stages. Counterbalance between Th17 and Treg cells in the gastrointestinal system result in the homeostasis and normal function of the immune system, particularly mucosal immunity. Recent data demonstrated a high infiltration of Th17 and Treg cells into the gastric tumor site and proved that tumor microenvironment might disturb the balance between Th17 and Treg. It is possible to assume an association between activation of CSCs which contribute to metastasis in late stages, and the imbalanced Th17/Treg cells observed in advanced gastric cancer patients. This review intends to clarify the importance of gastric tumor microenvironment specifically CSCs in relation to Th17/Tregs balance firstly and to highlight the relevance of imbalanced Th17/Treg subsets in determining the stages and behavior of the tumor secondly. Finally, the present study suggests a clinical approach looking at the plasticity of T cells with a focus on Th17 as a promising dedicated arm in cancer immunotherapy.

Targeting Cancer Stem Cells to Overcome Chemoresistance

Cancers are heterogeneous at the cell level, and the mechanisms leading to cancer heterogeneity could be clonal evolution or cancer stem cells. Cancer stem cells are resistant to most anti-cancer treatments and could be preferential targets to reverse this resistance, either targeting stemness pathways or cancer stem cell surface markers. Gold nanoparticles have emerged as innovative tools, particularly for photo-thermal therapy since they can be excited by laser to induce hyperthermia. Gold nanoparticles can be functionalized with antibodies to specifically target cancer stem cells. Preclinical studies using photo-thermal therapy have demonstrated the feasibility of targeting chemo-resistant cancer cells to reverse clinical chemoresistance. Here, we review the data linking cancer stem cells and chemoresistance and discuss the way to target them to reverse resistance. We particularly focus on the use of functionalized gold nanoparticles in the treatment of chemo-resistant metastatic cancers.

Gastric Cancer Stem Cells: Mechanisms and Therapeutic Approaches

Gastric cancer (GC) is the third leading cause of cancer-related deaths worldwide. GC stem-like cells (GCSCs), with unlimited self-renewal, differentiation, and tumor-regenerating capacities, contribute significantly to the refractory features of GC and have gained increasing attention for their role in GC drug resistance, relapse, and metastasis. Therapies targeting GCSCs seem to be one of the most promising methods to improve the outcomes of GC patients. Extensive investigations have attempted to outline the regulatory mechanisms in GCSCs and to develop GCSCs-targeting therapies with which to diminish GC drug resistance, metastasis and relapse. To the best of our knowledge, there is a lack of reviews summarizing these studies. In this review, we systematically recapitulated findings regarding the regulatory mechanisms of GCSCs, as well as therapies that target GCSCs, hoping to support the development of prognostic biomarkers and GCSCs-targeting anticancer therapies in GC.

New Opportunities and Challenges to Defeat Cancer Stem Cells

Cancer stem cells (CSCs) are a subpopulation of cancer cells that are capable of self-renewal, proliferation, differentiation, plastic adaptation, and immune regulation, thereby mediating tumorigenesis, metastasis, and therapy resistance. CSCs are associated with cancer progression and clinical outcome in cancer patients. Successful targeting of CSCs will therefore be necessary to eradicate and cure cancer. Functional regulators of stem cell (stemness) signaling pathways in human cancers have brought new opportunities to target CSCs and reframe cancer-targeting strategies in clinical settings. However, challenges remain due to a lack of complete understanding of CSC plasticity/heterogeneity and the limited efficacy of individual stemness inhibitors in cancer treatment. In this article we review CSC signaling pathways and the current state of CSC-targeting therapeutics in combinatory treatments in clinical trials.

PMP22 Regulates Self-Renewal and Chemoresistance of Gastric Cancer Cells

Cancer stem cells possess self-renewal and chemoresistance activities. However, the manner in which these features are maintained remains obscure. We sought to identify cell surface protein(s) that mark self-renewing and chemoresistant gastric cancer cells using the explorer antibody microarray. We identified PMP22, a target gene of the Wnt/β-catenin pathway, as the most upregulated cell surface protein in gastric cancer xenografts exposed to cisplatin (DDP). PMP22 expression was markedly upregulated in tumorspheric cells and declined with differentiation. Infecting gastric cancer cells with lentivirus expressing PMP22 shRNAs reduced proliferation, tumorsphere formation, and chemoresistance to cisplatin in vitro and in NOD/SCID mice. When combined with bortezomib, a PMP22 inhibitor, the chemotherapeutic sensitivity to cisplatin treatment was dramatically increased by inducing cell apoptosis in cultured cells and xenograft mouse models. Finally, mRNA expression levels of PMP22 were detected in 38 tumor specimens from patients who received six cycles of perioperative chemotherapy. A strong correlation between PMP22 level and tumor recurrence was revealed, thus showing a pivotal role of PMP22 in the clinical chemoresistance of gastric cancer. Our study is the first to show the role of PMP22 in gastric cancer stemness and chemoresistance and reveals a potential new target for the diagnosis and treatment of recurrent gastric cancer. Mol Cancer Ther; 16(6); 1187-98. ©2017 AACR.

A unified model of the hierarchical and stochastic theories of gastric cancer

Gastric cancer (GC) is a life-threatening disease worldwide. Despite remarkable advances in treatments for GC, it is still fatal to many patients due to cancer progression, recurrence and metastasis. Regarding the development of novel therapeutic techniques, many studies have focused on the biological mechanisms that initiate tumours and cause treatment resistance. Tumours have traditionally been considered to result from somatic mutations, either via clonal evolution or through a stochastic model. However, emerging evidence has characterised tumours using a hierarchical organisational structure, with cancer stem cells (CSCs) at the apex. Both stochastic and hierarchical models are reasonable systems that have been hypothesised to describe tumour heterogeneity. Although each model alone inadequately explains tumour diversity, the two models can be integrated to provide a more comprehensive explanation. In this review, we discuss existing evidence supporting a unified model of gastric CSCs, including the regulatory mechanisms of this unified model in addition to the current status of stemness-related targeted therapy in GC patients.

Identifying and targeting cancer stem cells in the treatment of gastric cancer

Current treatment regimens for gastric cancer are not adequate. Cancer stem cells (CSCs) may be a key driving factor for growth and metastasis of this tumor type. In contrast to the conventional clonal evolution hypothesis, CSCs can initiate tumor formation, self‐renew, and differentiate into tumor‐propagating cells. Because gastric cancer can originate from CSCs, it is necessary to review current targets of signaling pathways for CSCs in gastric cancer that are being studied in clinical trials. These pathways are known to regulate the self‐renewal and differentiation process in gastric CSCs. A better understanding of the clinical results of trials that target gastric CSCs will lead to better outcomes for patients with gastric cancer. Cancer 2017;123:1303–1312. © 2017 The Authors. Cancer published by Wiley Periodicals, Inc. on behalf of American Cancer Society. This is an open access article under the terms of the Creative Commons Attribution NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

Cancer stem cells may be a key driving factor in the growth and metastasis of gastric cancer. Because gastric cancer can originate from cancer stem cells, it is necessary to review current targets of signaling pathways for cancer stem cells in gastric cancer that are being studied in clinical trials.

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.

New trends in guided nanotherapies for digestive cancers: A systematic review

Digestive tract tumors are among the most common and deadliest malignancies worldwide, mainly due to late diagnosis and lack of efficient therapeutics. Current treatments essentially rely on surgery associated with (neo)adjuvant chemotherapy agents. Despite an upfront response, conventional drugs often fail to eliminate highly aggressive clones endowed with chemoresistant properties, which are responsible for tumor recurrence and disease dissemination. Synthetic drugs also present severe adverse systemic effects, hampering the administration of biologically effective dosages. Nanoencapsulation of chemotherapeutic agents within biocompatible polymeric or lipid matrices holds great potential to improve the pharmacokinetics and efficacy of conventional chemotherapy while reducing systemic toxicity. Tagging nanoparticle surfaces with specific ligands for cancer cells, namely monoclonal antibodies or antibody fragments, has provided means to target more aggressive clones, further improving the selectivity and efficacy of nanodelivery vehicles. In fact, over the past twenty years, significant research has translated into a wide array of guided nanoparticles, providing the molecular background for a new generation of intelligent and more effective anti-cancer agents. Attempting to bring awareness among the medical community to emerging targeted nanopharmaceuticals and foster advances in the field, we have conducted a systematic review about this matter. Emphasis was set on ongoing preclinical and clinical trials for liver, colorectal, gastric and pancreatic cancers. To the best of our knowledge this is the first systematic and integrated overview on this field. Using a specific query, 433 abstracts were gathered and narrowed to 47 manuscripts when matched against inclusion/exclusion criteria. All studies showed that active targeting improves the effectiveness of the nanodrugs alone, while lowering its side effects. The main focus has been on hepatocarcinomas, mainly by exploring glycans as homing molecules. Other ligands such as peptides/small proteins and antibodies/antibody fragments, with affinity to either tumor vasculature or tumor cells, have also been widely and successfully applied to guide nanodrugs to gastrointestinal carcinomas. Conversely, few solutions have been presented for pancreatic tumors. To this date only three nanocomplexes have progressed beyond pre-clinical stages: i) PK2, a galactosamine-functionalized polymeric-DOX formulation for hepatocarcinomas; ii) MCC-465, an anti-(myosin heavy chain a) immunoliposome for advanced stage metastatic solid tumors; and iii) MBP-426, a transferrin-liposome-oxaliplatin conjugate, also for advanced stage tumors. Still, none has been approved for clinical use. However, based on the high amount of pre-clinical studies showing enthusiastic results, the number of clinical trials is expected to increase in the near future. A more profound understanding about the molecular nature of chemoresistant clones and cancer stem cell biology will also contribute to boost the field of guided nanopharmacology towards more effective solutions.

Interaction between gastric cancer stem cells and the tumor microenvironment

Gastric cancer (GC) remains a leading cause of cancer-related deaths worldwide. Cancer stem cells (CSCs) are selectively capable of tumor initiation and are implicated in tumor relapse and metastasis, thus, governing the prognosis of GC patients. Stromal cells and extracellular matrix adjacent to cancer cells are known to form a supportive environment for cancer progression. CSC properties are also regulated by their microenvironment through cell signaling and related factors. This review presents the current findings regarding the influence of the tumor microenvironment on GC stem cells, which will support the development of novel therapeutic strategies for patients with GC.

Gastric cancer stem cells in gastric carcinogenesis, progression, prevention and treatment

In recent decades, the study of the mechanism of tumorigenesis has brought much progress to cancer treatment. However, cancer stem cell (CSC) theory has changed previous views of tumors, and has provided a new method for treatment of cancer. The discovery of CSCs and their characteristics have contributed to understanding the molecular mechanism of tumor genesis and development, resulting in a new effective strategy for cancer treatment. Gastric CSCs (GCSCs) are the basis for the onset of gastric cancer. They may be derived from gastric stem cells in gastric tissues, or bone marrow mesenchymal stem cells. As with other stem cells, GCSCs highly express drug-resistance genes such as aldehyde dehydrogenase and multidrug resistance, which are resistant to chemotherapy and thus form the basis of drug resistance. Many specific molecular markers such as CD44 and CD133 have been used for identification and isolation of GCSCs, diagnosis and grading of gastric cancer, and research on GCSC-targeted therapy for gastric cancer. Therefore, discussion of the recent development and advancements in GCSCs will be helpful for providing novel insight into gastric cancer treatment.

Cancer stem cells: the 'heartbeat' of gastric cancer

Gastric cancer (GC) remains one of the most common cancers worldwide. Its prevalence is still on the rise in the developing countries due to the ageing population. The cancer stem cell (CSC) theory provides a new insight into the interpretation of tumor initiation, aggressive growth, recurrence, and metastasis of cancer, as well as the development of new strategies for cancer treatment. This review will focus on the progress of biomarkers and signaling pathways of CSCs, the complex crosstalk networks between the microenvironment and CSCs, and the development of therapeutic approaches against CSCs, predominantly focusing on GC.

Efficacy of RNA polymerase II inhibitors in targeting dormant leukaemia cells

Background

Dormant cells are characterised by low RNA synthesis. In contrast, cancer cells can be addicted to high RNA synthesis, including synthesis of survival molecules. We hypothesised that dormant cancer cells, already low in RNA, might be sensitive to apoptosis induced by RNA Polymerase II (RP2) inhibitors that further reduce RNA synthesis.

Methods

We cultured leukaemia cells continuously in vitro in the presence of an mTOR inhibitor to model dormancy. Apoptosis, damage, RNA content and reducing capacity were evaluated. We treated dormancy-enriched cells for 48 hours with the nucleoside analogues ara-C, 5-azacytidine and clofarabine, the topoisomerase targeting agents daunorubicin, etoposide and irinotecan and three multikinase inhibitors with activity against RP2 - flavopiridol, roscovitine and TG02, and we measured growth inhibition and apoptosis. We describe use of the parameter 2 × IC₅₀ to measure residual cell targeting. RNA synthesis was measured with 5-ethynyl uridine. Drug-induced apoptosis was measured flow cytometrically in primary cells from patients with acute myeloid leukaemia using a CD34/CD71/annexinV gating strategy to identify dormant apoptotic cells.

Results

Culture of the KG1a cell line continuously in the presence of an mTOR inhibitor induced features of dormancy including low RNA content, low metabolism and low basal ROS formation in the absence of a DNA damage response or apoptosis. All agents were more effective against the unmanipulated than the dormancy-enriched cells, emphasising the chemoresistant nature of dormant cells. However, the percentage of cell reduction by RP2 inhibitors at 2 × IC₅₀ was significantly greater than that of other agents. RP2 inhibitors strongly inhibited RNA synthesis compared with other drugs. We also showed that RP2 inhibitors induce apoptosis in proliferating and dormancy-enriched KG1a cells and in the CD71^neg CD34^pos subset of primary acute myeloid leukaemia cells.

Conclusion

We suggest that RP2 inhibitors may be a useful class of agent for targeting dormant leukaemia cells.

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.

EZH2 is required for breast and pancreatic cancer stem cell maintenance and can be used as a functional cancer stem cell reporter

Although cancer is largely seen as a disease stemming from genetic mutations, evidence has implicated epigenetic regulation of gene expression as a driving force for tumorigenesis. Epigenetic regulation by histone modification, specifically through polycomb group (PcG) proteins such as EZH2 and BMI-1, is a major driver in stem cell biology and is found to be correlated with poor prognosis in many tumor types. This suggests a role for PcG proteins in cancer stem cells (CSCs). We hypothesized that epigenetic modification by EZH2, specifically, helps maintain the CSC phenotype and that in turn this epigenetic modifier can be used as a reporter for CSC activity in an in vitro high-throughput screening assay. CSCs isolated from pancreatic and breast cancer lines had elevated EZH2 levels over non-CSCs. Moreover, EZH2 knockdown by RNA interference significantly reduced the frequency of CSCs in all models tested, confirming the role of EZH2 in maintenance of the CSC population. Interestingly, genes affected by EZH2 loss, and therefore CSC loss, were inversely correlated with genes identified by CSC enrichment, further supporting the function of EZH2 CSC regulation. We translated these results into a novel assay whereby elevated EZH2 staining was used as a reporter for CSCs. Data confirmed that this assay could effectively measure changes, both inhibition and enrichment, in the CSC population, providing a novel approach to look at CSC activity. This assay provides a unique, rapid way to facilitate CSC screening across several tumor types to aid in further CSC-related research.

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.