Sequential expression of putative stem cell markers in gastric carcinogenesis

Single-cell sequencing analysis revealed that WDR72 was a novel cancer stem cells related gene in gastric cancer

Background

Cancer stem cells (CSCs) are pivotal in tumor resistance to chemotherapy and gastric cancer's rapid proliferation and metastasis. We aimed to explore the CSCs-related genes in gastric cancer epithelial cells.

Methods

The mRNA expression profile and single-cell sequencing data of gastric cancer were downloaded from the public database.

Results

We identified WDR72 as a CSCs-related gene in gastric cancer epithelial cells. WDR72 was highly expressed in gastric cancer tissues, and high expression of WDR72 was associated with inferior prognosis of patients. WDR72 expression had a significant negative correlation with the infiltration of CD8 + T cells and activated memory CD4 + T cells. PD-L1 expression was significantly reduced in gastric cancer patients with high WDR72 expression. WDR72 was correlated with IC50 of multiple small-molecule drugs.

Conclusion

We identified a novel CSCs-related gene in gastric cancer epithelial cells, WDR72, which was highly expressed in patients with high stemness scores.

An individualized stemness-related signature to predict prognosis and immunotherapy responses for gastric cancer using single-cell and bulk tissue transcriptomes

BACKGROUND

Currently, many stemness-related signatures have been developed for gastric cancer (GC) to predict prognosis and immunotherapy outcomes. However, due to batch effects, these signatures cannot accurately analyze patients one by one, rendering them impractical in real clinical scenarios. Therefore, we aimed to develop an individualized and clinically applicable signature based on GC stemness.

METHODS

Malignant epithelial cells from single-cell RNA-Seq data of GC were used to identify stemness-related signature genes based on the CytoTRACE score. Using two bulk tissue datasets as training data, the enrichment scores of the signature genes were applied to classify samples into two subtypes. Then, using the identified subtypes as criteria, we developed an individualized stemness-related signature based on the within-sample relative expression orderings of genes.

RESULTS

We identified 175 stemness-related signature genes, which exhibited significantly higher AUCell scores in poorly differentiated GCs compared to differentiated GCs. In training datasets, GC samples were classified into two subtypes with significantly different survival times and genomic characteristics. Utilizing the two subtypes, an individualized signature was constructed containing 47 gene pairs. In four independent testing datasets, GC samples classified as high risk exhibited significantly shorter survival times, higher infiltration of M2 macrophages, and lower immune responses compared to low-risk samples. Moreover, the potential therapeutic targets and corresponding drugs were identified for the high-risk group, such as CD248 targeted by ontuxizumab.

CONCLUSIONS

We developed an individualized stemness-related signature, which can accurately predict the prognosis and efficacy of immunotherapy for each GC sample.

Loss of ATOH1 in Pit Cell Drives Stemness and Progression of Gastric Adenocarcinoma by Activating AKT/mTOR Signaling through GAS1

Gastric cancer stem cells (GCSCs) are self-renewing tumor cells that govern chemoresistance in gastric adenocarcinoma (GAC), whereas their regulatory mechanisms remain elusive. Here, the study aims to elucidate the role of ATOH1 in the maintenance of GCSCs. The preclinical model and GAC sample analysis indicate that ATOH1 deficiency is correlated with poor GAC prognosis and chemoresistance. ScRNA-seq reveals that ATOH1 is downregulated in the pit cells of GAC compared with those in paracarcinoma samples. Lineage tracing reveals that Atoh1 deletion strongly confers pit cell stemness. ATOH1 depletion significantly accelerates cancer stemness and chemoresistance in Tff1-CreERT2; Rosa26Tdtomato and Tff1-CreERT2; Apcfl/fl ; p53fl/fl (TcPP) mouse models and organoids. ATOH1 deficiency downregulates growth arrest-specific protein 1 (GAS1) by suppressing GAS1 promoter transcription. GAS1 forms a complex with RET, which inhibits Tyr1062 phosphorylation, and consequently activates the RET/AKT/mTOR signaling pathway by ATOH1 deficiency. Combining chemotherapy with drugs targeting AKT/mTOR signaling can overcome ATOH1 deficiency-induced chemoresistance. Moreover, it is confirmed that abnormal DNA hypermethylation induces ATOH1 deficiency. Taken together, the results demonstrate that ATOH1 loss promotes cancer stemness through the ATOH1/GAS1/RET/AKT/mTOR signaling pathway in GAC, thus providing a potential therapeutic strategy for AKT/mTOR inhibitors in GAC patients with ATOH1 deficiency.

FTO-mediated m6A modification promotes malignant transformation of gastric mucosal epithelial cells in chronic Cag A+ Helicobacter pylori infection

OBJECTIVES

Cag A+ Helicobacter pylori chronic infection cause malignant transformation of the human gastric mucosa. N6-methyladenosine (m6A) modifications are the most common and abundant mRNA modifications and one of the pathways affecting tumorigenicity and tumor progression. However, the role of m6A modification in the process of chronic H. pylori infection leading to malignant transformation of gastric mucosa is unclear.

METHODS

In this study, we used Cag A- and Cag A+H. pylori chronic infection to establish cellular models in GES-1 cells and analyzed the cellular morphology, proliferation, apoptosis, invasiveness and tumorigenicity of gastric mucosal epithelial cells. The m6A expression levels of GES-1 cells after chronic infection with Cag A- and Cag A+H. pylori were examined, and modifying effect of FTO (the fat mass and obesity-associated protein) on CD44 was verified by MeRIP-qPCR. Finally, the FTO expression changes and m6A expression levels were further validated in clinical gastric cancer tissues.

RESULTS

Chronic Cag A+H. pylori-infected GES-1 cells exhibit altered cell morphology, apoptosis inhibition, abnormal proliferation, enhanced migration, colony formation, and increased stem cell-like properties. Meanwhile, FTO and CD44 expression was enhanced, and FTO may induce malignant transformation of gastric mucosa by regulating CD44 mRNA m6A methylation modifications.

CONCLUSIONS

We verified the effect of chronic stimulation of Cag A+H. pylori on malignant transformation of gastric mucosal epithelium. revealing the possibility of FTO in promoting malignant transformation of gastric mucosa by modifying CD44 mRNA methylation, suggesting that FTO expression is a potential molecule for malignant transformation of gastric mucosal epithelial cells.

Impact of Cancer Stem Cells on Therapy Resistance in Gastric Cancer

Gastric cancer (GC) is the fourth leading cause of cancer death worldwide, with an average 5-year survival rate of 32%, being of 6% for patients presenting distant metastasis. Despite the advances made in the treatment of GC, chemoresistance phenomena arise and promote recurrence, dissemination and dismal prognosis. In this context, gastric cancer stem cells (gCSCs), a small subset of cancer cells that exhibit unique characteristics, are decisive in therapy failure. gCSCs develop different protective mechanisms, such as the maintenance in a quiescent state as well as enhanced detoxification procedures and drug efflux activity, that make them insusceptible to current treatments. This, together with their self-renewal capacity and differentiation ability, represents major obstacles for the eradication of this disease. Different gCSC regulators have been described and used to isolate and characterize these cell populations. However, at the moment, no therapeutic strategy has achieved the effective targeting of gCSCs. This review will focus on the properties of cancer stem cells in the context of therapy resistance and will summarize current knowledge regarding the impact of the gCSC regulators that have been associated with GC chemoradioresistance.

Inhibition of Musashi-1 enhances chemotherapeutic sensitivity in gastric cancer patient-derived xenografts

Musashi-1 (MSI1), a neural RNA-binding protein, is considered a gastric and intestinal stem cell marker. Although the function of MSI1 in gastric cancer has attracted increasing interest, it is not known whether MSI1 can be used as a biomarker to monitor gastric cancer development and response to treatment. Here, the role of MSI1 in the chemotherapeutic sensitivity of gastric cancer was investigated. Patients with high MSI1 levels had poor outcomes, implicating the gene in the development and progression of the disease. We overexpressed and silenced MSI1 in the human gastric cancer cell lines MKN45 and HGC27, finding that knockdown reduced proliferation, invasion, and migration, while promoting apoptosis. A patient-derived xenograft gastric cancer model was constructed in which mice received chemical drugs, si-MSI1, or a drug-si-MSI1 combination. It was found that blocking MSI1 expression reduced gastric cancer drug tolerance. The combination treatment with si-MSI1 was superior to 5F-dUMP and cisplatin, either separately or in combination, indicating that including si-MSI1 was better than drug therapy alone. Transcriptome sequencing analysis showed that MSI1 altered cell cycle regulation and growth signal transduction, including that of blood vessel epicardial substance (BVES). These results suggest that MSI1 reduces the tolerance of gastric cancer to chemical drugs through modulation of MSI1/BVES signaling.

Immunoexpression of E-cadherin, CD44 and Claudin 7 in gastric adenocarcinomas

Gastric adenocarcinomas represent frequent malignant tumors in the digestive tract, with a high and constant mortality rate in last decades. The disturbance of the adhesion molecules expression, which normally is essential in maintaining epithelial homeostasis, has a critical role in the initiation and progression of tumors. In this study, we analyzed the immunoexpression of E-cadherin, cluster of differentiation 44 (CD44), and Claudin 7 in 58 cases of gastric adenocarcinomas, in relation to the histopathological parameters of the lesions' aggressiveness. Increased E-cadherin immunoexpression was observed in tubular adenocarcinomas, those of low grade and in stages I-III. CD44 presented high scores in discohesive, hepatoid, tubular, and tubulopapillary adenocarcinomas, those of high grade and in advanced stages. Claudin 7 associated increased scores for tubular, tubulopapillary and micropapillary tumors, those of low grade and mainly in stage I. The markers used in the study can be useful for assessing the aggressiveness of gastric adenocarcinomas, in the context of specific adapted therapy.

Cancerous and non-neoplastic stem cells in the stomach similarly express CD44 and CD133

CD44 and CD133 have been considered as cancer stem cell (CSC) markers. Stem cell markers are rarely described in healthy stomach tissues. However, the clinicopathological and prognostic value of CD44 and CD133 in gastric cancer remains controversial. This study investigated the expression of CD44 and CD133 in gastric cancer and non-neoplastic gastric mucosa. We used samples of primary gastric adenocarcinomas (n = 69), metastatic lymph nodes (n = 30), intestinal metaplasia (n = 17), and histologically normal gastric tissues of surgical margins (n = 54). The expression of CD44 and CD133 were studied in samples by immunohistochemistry. Fisher's exact test and a logistic regression model were used in this study. CD44 expression was observed in 12% of samples with intestinal metaplasia, 20% with lymph node metastases, 22% with normal mucosa, to 30% of samples with primary tumors. Most of these positive tumors showed immunostaining in less than 4% of cancerous cells, mainly in the diffuse type. CD133 expression was observed in 7% (intestinal metaplasia) to 46% (normal mucosa). In the positive cases of cancer (24%), in most of them, less than 3% of cells were marked. CD44 and CD133 expression in the histologically normal gastric mucosa was restricted to the deeper regions of the gastric crypts at the level where stem cells and progenitor cells are usually found. CD44 and CD133 expression occurs in few gastric cancer cells, mainly in diffuse carcinomas, and are expressed in histologically normal gastric mucosae. None of the markers are specific for cancer and are also present in intestinal metaplasia and the normal mucosa.

Musashi-1-A Stemness RBP for Cancer Therapy?

The RNA-binding protein Musashi-1 (MSI1) promotes stemness during development and cancer. By controlling target mRNA turnover and translation, MSI1 is implicated in the regulation of cancer hallmarks such as cell cycle or Notch signaling. Thereby, the protein enhanced cancer growth and therapy resistance to standard regimes. Due to its specific expression pattern and diverse functions, MSI1 represents an interesting target for cancer therapy in the future. In this review we summarize previous findings on MSI1's implications in developmental processes of other organisms. We revisit MSI1's expression in a set of solid cancers, describe mechanistic details and implications in MSI1 associated cancer hallmark pathways and highlight current research in drug development identifying the first MSI1-directed inhibitors with anti-tumor activity.

Increased CD44 Expression and MEK Activity Predict Worse Prognosis in Gastric Adenocarcinoma Patients Undergoing Gastrectomy

PURPOSE

We have shown that activation of the receptor tyrosine kinase (RTK)-RAS pathway in gastric adenocarcinoma (GA) promotes acquisition of cancer stem-like cell (CSC) phenotypes including metastasis and chemotherapy resistance. Here, we evaluated the prognostic value of the CSC marker CD44 and the RTK-RAS activation marker phosphorylated MEK (p-MEK) in patients with resectable GA.

METHODS

CD44 and p-MEK were measured in tumors from GA patients who underwent curative-intent gastrectomy at Fujian Medical University Union Hospital (FMUUH, n = 134) and Memorial Sloan Kettering Cancer Center (MSKCC, n = 56). Overall survival (OS) was estimated by the Kaplan-Meier method, and multivariate analysis was performed by Cox proportional hazards regression modeling.

RESULTS

Despite multiple significant differences in clinicopathologic characteristics between the FMUUH and MSKCC cohorts, high CD44 and high p-MEK expression were both independent negative prognostic factors for OS on univariate analysis in both cohorts (p < 0.05). Both factors were also significant on multivariate analysis when the cohorts were combined (p ≤ 0.003). On subgroup analysis, the 5-year OS of patients with both high CD44 and high p-MEK was 39.5-41.6% compared with 55.4-66.4% for patients with low CD44. High CD44 expression was associated with more advanced TNM stage in the FMUUH cohort and larger tumor size and undifferentiated histology in the MSKCC cohort. High p-MEK was associated with undifferentiated histology in the FMUUH cohort and larger tumor size in the MSKCC cohort.

CONCLUSIONS

Increased CD44 and p-MEK expression are predictive of worse OS in GA patients. Thus, targeting the RTK-RAS pathway may benefit patients with CD44-positive, RAS-activated GA by inhibiting metastasis and reversing chemotherapy resistance.

E2F1 Maintains Gastric Cancer Stemness Properties by Regulating Stemness-Associated Genes

Purpose

To determine the regulatory role of E2F1 in maintaining gastric cancer stemness properties and the clinical significance of E2F1 in gastric cancer.

Materials and Methods

We conducted a tumor spheroid formation assay to enrich gastric cancer stem-like cells. The protein and mRNA expression levels of genes were measured using Western Blot and qRT-PCR. Lentivirus-mediated overexpression and downregulation of E2F1 were performed to evaluate the effect of E2F1 on the stemness properties of gastric cancer cells. The effect of E2F1 on gastric cancer cell sensitivity of 5-Fu was evaluated using cell viability assay and TdT-mediated dUTP Nick-End Labeling staining. We also analyzed the association between E2F1 expression and clinical characteristics in gastric cancer patients. The KM plotter database was used to analyze the relationship between E2F1 and overall survival in GC patients.

Results

We found that E2F1 expression was significantly higher in gastric cancer tissues than in the paired adjacent normal tissues (p < 0.05) and was positively correlated with tumor size (p < 0.05), T stage (p < 0.05), and differentiation degree (p < 0.05). KM plotter database demonstrated a close association between higher E2F1 expression level and worse overall survival of gastric cancer patients (p < 0.05). In vitro assay illustrated that E2F1 could regulate the expression of stemness-associated genes, such as BMI1, OCT4, Nanog, and CD44, and maintain the tumor spheroid formation ability of gastric cancer cells. E2F1 enhanced 5-Fu resistance in gastric cancer cells, and the E2F1 expression level was correlated with the prognosis of gastric cancer patients receiving 5-Fu therapy. The expression levels of stemness-associated genes were also significantly higher in gastric cancer tissues than the paired adjacent normal tissues (p < 0.05). A positive correlation was observed between E2F1 and BMI1 (r = 0.422, p < 0.05), CD44 (r = 0.634, p < 0.05), OCT4 (r = 0.456, p < 0.05), and Nanog (r = 0.337, p < 0.05) in gastric cancer tissues. The co-overexpression of E2F1 and stemness-associated genes was associated with worse overall survival.

Conclusion

E2F1 plays a significant role in gastric cancer progression by maintaining gastric cancer stemness properties through the regulation of stemness-associated genes. The close association between E2F1 and poor prognosis of patients suggests that E2F1 could serve as a prognostic biomarker and a therapeutic target in gastric cancer patients.

Identification and characterization of a subpopulation of CD133+ cancer stem-like cells derived from SK-UT-1 cells

BACKGROUND

Uterine leiomyosarcoma (ULMS) is a malignant tumor found in the smooth muscle lining the walls of the uterus. Cancer stem cells (CSCs) are responsible for metastasis, drug resistance, and relapse of cancer, resulting in treatment failure. However, little is known about CSCs and their associated-markers in ULMS. We aimed to characterize and identify a subpopulation of CD133⁺ cancer stem-like cells derived from SK-UT-1 cell line.

METHODS

SK-UT-1 cells were sphere-forming cultured in vitro. We also sorted the CD133⁺ cells derived from SK-UT-1 cell line by immunomagnetic beads. CD133⁺ subpopulation and apoptotic cells were detected by flow cytometry. Self-renewal and anchorage-independent growth capabilities were examined using sphere and colony formation assays. The tumorigenicity of the fourth-passage spheres and parental SK-UT-1 cells was used by mouse xenograft model in vivo. Cell proliferation ability and sensitivity to doxorubicin (DXR) were assessed by CCK-8 assay. Cell migration and invasion were tested by wound healing assay or Transwell migration and invasion assays. Expressions of CSC-related marker were analyzed by Western blotting.

RESULTS

The fourth-passage spheres were defined as a CD133⁺ cell population, which was accompanied by increase of sphere and colony forming rate, migration and invasion abilities, as well as drug-resistant properties in vitro. Moreover, the fourth-passage spheres showed a stronger tumorigenic potential in vivo. CD133⁺ cell population sorted from SK-UT-1 line showed an increased ability in sphere and colony formation, proliferation, migration, invasion, resistance to apoptosis after treatment with doxorubicin (DXR) compared with CD133^- cell population. The expression levels of CSCs-related markers (e.g., CD44, ALDH1,BMI1, and Nanog), were significantly elevated in CD133⁺ cells compared with those in CD133^- cells.

CONCLUSIONS

Collectively, our findings indicated that CD133 may be a significant marker for cancer stem-like cells, and it may be a potential therapeutic target for human ULMS.

LGR5 expression is associated with prognosis in poorly differentiated gastric adenocarcinoma

Background

Leucine-rich repeat-containing G-protein-coupled receptor 5 (LGR5) is an important cancer stem cell marker in gastric cancer. However, no detailed studies are available on LGR5 expression in poorly differentiated gastric adenocarcinoma (PD-AC). Therefore, we investigated the relationship between LGR5 expression and clinicopathological data in PD-AC.

Methods

LGR5 mRNA expression levels were quantified in 41 PD-AC specimens using a highly sensitive RNAscope in situ hybridization technique. Epstein–Barr virus (EBV) infection was also detected by EBV in situ hybridization.

Results

LGR5 expression levels were measured in 38 of 41 PD-AC cases, and 17 cases were identified as LGR5 high. The frequency of EBV positivity tended to be higher in the LGR5-low group than in the LGR5-high group (P = 0.0764). Furthermore, the frequency of vascular invasion tended to be higher in the LGR5-high group than in the LGR5-low group (P = 0.0764). The overall survival of PD-AC patients in the LGR5-high group was significantly lower than in the LGR5-low group (log-rank test, P = 0.0108). The Cox proportional hazard regression model revealed that the LGR5-low group (HR = 0.29; 95% CI: 0.11–0.74; P = 0.01) showed independently better OS for PD-AC.

Conclusions

Quantifying the levels of LGR5 expression may facilitate defining prognosis in Japanese patients with PD-AC. Further study of LGR5 in this context is warranted.

Clinical and prognostic significances of cancer stem cell markers in gastric cancer patients: a systematic review and meta-analysis

Background

Gastric cancer (GC) is considered one of the most lethal malignancies worldwide, which is accompanied by a poor prognosis. Although reports regarding the importance of cancer stem cell (CSC) markers in gastric cancer progression have rapidly developed over the last few decades, their clinicopathological and prognostic values in gastric cancer still remain inconclusive. Therefore, the current meta-analysis aimed to quantitatively re-evaluate the association of CSC markers expression, overall and individually, with GC patients’ clinical and survival outcomes.

Methods

Literature databases including PubMed, Scopus, ISI Web of Science, and Embase were searched to identify the eligible articles. Hazard ratios (HRs) or odds ratios (ORs) with 95% confidence intervals (CIs) were recorded or calculated to determine the relationships between CSC markers expression positivity and overall survival (OS), disease-free survival (DFS)/relapse-free survival (RFS), disease-specific survival (DSS)/ cancer-specific survival (CSS), and clinicopathological features.

Results

We initially retrieved 4,425 articles, of which a total of 66 articles with 89 studies were considered as eligible for this meta-analysis, comprising of 11,274 GC patients. Overall data analyses indicated that the overexpression of CSC markers is associated with TNM stage (OR = 2.19, 95% CI 1.84–2.61, P = 0.013), lymph node metastasis (OR = 1.76, 95% CI 1.54–2.02, P < 0.001), worse OS (HR = 1.65, 95% CI 1.54–1.77, P < 0.001), poor CSS/DSS (HR = 1.69, 95% CI 1.33–2.15, P < 0.001), and unfavorable DFS/RFS (HR = 2.35, 95% CI 1.90–2.89, P < 0.001) in GC patients. However, CSC markers expression was found to be slightly linked to tumor differentiation (OR = 1.25, 95% CI 1.01–1.55, P = 0.035). Sub-analysis demonstrated a significant positive relationship between most of the individual markers, specially Gli-1, Oct-4, CD44, CD44V6, and CD133, and clinical outcomes as well as the reduced survival, whereas overexpression of Lgr-5, Nanog, and sonic hedgehog (Shh) was not found to be related to the majority of clinical outcomes in GC patients.

Conclusion

The expression of CSC markers is mostly associated with worse outcomes in patients with GC, both overall and individual. The detection of a combined panel of CSC markers might be appropriate as a prognostic stratification marker to predict tumor aggressiveness and poor prognosis in patients with GC, which probably results in identifying novel potential targets for therapeutic approaches.

Screening and identification of a CD44v6 specific peptide using improved phage display for gastric cancer targeting

Background

Peptide probes can be applied for biomarker targeting to improve the diagnostic accuracy. Cluster of differentiation 44 (CD44) is up-regulated in gastric cancer (GC). Among all the variants of CD44, CD44v6 is reported the most promising biomarker for GC. The purpose of this study was generating and identification a peptide ligand specific to CD44v6.

Methods

A 12-mer phage peptide library was screened on CD44v overexpressed HEK-293 cells with an improved subtractive method. Five candidate sequences emerged. Candidate phages were selected using enzyme-linked immunosorbent assay and competitive inhibition assays. Then the sequence (designated ELT) was chosen for further study. Its binding affinity and specificity were verified on recombinant protein, GC cells, GC tissues and xenograft models based on BALB/c-nu/nu mice using dissociation constant calculation, immunofluorescence, immunohistochemistry and in vivo imaging separately.

Results

The dissociation constant of ELT with recombinant protein was 611.2 nM. ELT stained CD44v overexpressed HEK-293 but not the cell expressing wild-type CD44s. On GC cell lines, ELT co-stained with anti-CD44v6 antibody. ELT binding on tumor tissues significantly increased compared with that of paracancer tissues, also showed a linear positive correlation with CD44v6 expression. ELT specifically accumulated in tumor and eliminated in short time in vivo.

Conclusions

ELT can target GC in vitro and in vivo via CD44v6, indicating its potential to serve as a probe for GC targeting diagnosis and therapy.

Gastrointestinal cancer stem cells as targets for innovative immunotherapy

The role of cancer stem cells in gastrointestinal cancer-associated death has been widely recognized. Gastrointestinal cancer stem cells (GCSCs) are considered to be responsible for tumor initiation, growth, resistance to cytotoxic therapies, recurrence and metastasis due to their unique properties. These properties make the current therapeutic trials against GCSCs ineffective. Moreover, recent studies have shown that targeting stem cell surface markers or stemness associated pathways might have an additional off-target effect on the immune system. Recent advances in oncology and precision medicine have opened alternative therapeutic strategies in the form of cancer immunotherapy. This approach differs from classical anti-cancer therapy through its mechanism of action involving the activation and use of a functional immune system against tumor cells, instead of aiming physically destruction of cancer cells through radio- or chemotherapy. New immunological approaches for GCSCs targeting involve the use of different immune cells and various immune mechanisms like targeting specific surface antigens, using innate immune cells like the natural killer and T cells, T-cell chimeric antigen receptor technology, dendritic cell vaccine, or immune checkpoint inhibitors. In this respect, better understandings of immune regulatory mechanisms that govern anti-tumor response bring new hope in obtaining long-term remission for cancer therapy.

Prognostic Value of Cyclin D1 and CD44 Expression in Gastric Adenocarcinoma

BACKGROUND

Worldwide, gastric carcinoma (GC) is the 5th most common malignancies in both sexes representing 6.8% of the total fatalities and is the 3rd leading cause of cancer death representing 8.8% of total fatalities. In Egypt, GC considers the 12th leading cause of cancer death representing 2.2% of the total cancer mortality. A growing body of evidence supports that cancer stem cells (CSCs) are resistant to chemotherapy or radiation, and the cell adhesion molecule CD44 has been identified as a cell surface marker associated with cancer stem cell in several types of tumors including gastric cancer. CD44 regulates gastric stem cell proliferation by increasing cyclin D1 expression which represents an important regulatory protein in the cell cycle transition from G1 phase to S phase. This study aimed to investigate whether cyclin D1 and CD44 can be used as prognostic indicators in gastric cancer.

MATERIAL AND METHODS

Forty formalin-fixed and paraffin-embedded gastric tissues, obtained from patients who underwent endoscopic resection or surgical resection, constituted the group of our study. The immunohistochemical expression of cyclin D1 and CD44 was examined and correlated with clinical-pathological parameters and outcome of the patients.

RESULTS

Overexpression of CD44 and cyclin D1 was noted (in of 55 and 50% respectively). Cyclin D1 and CD44 positive expressions in GC were positively correlated with tumor differentiation (p = 0.020, p = 0.004 respectively), TNM stage (p < 0.001 for both), poor survival (p < 0.001 for both), and with increased rate of recurrence (p = 0.020, p = 0.005 respectively).

CONCLUSION

CD44 and cyclin D1 were associated with poor prognosis in gastric cancer, and so, they comprise an attractive target for anticancer drug development.

Musashi-1 promotes stress-induced tumor progression through recruitment of AGO2

Carcinomatous progression and recurrence are the main therapeutic challenges frequently faced by patients with refractory tumors. However, the underlined molecular mechanism remains obscure.

Methods: We found Musashi-1 (MSI1) transported into cytosol under stress condition by confocal microscopy and cell fractionation. Argonaute 2 (AGO2) was then identified as a cytosolic binding partner of MSI1 by Mass Spectrametry, immunoprecipitation, and recombinant protein pull-down assay. We used RNA-IP to determine the MSI1/AGO2 associated regions on downstream target mRNAs. Finally, we overexpressed C-terminus of MSI1 to disrupt endogenous MSI1/AGO2 interaction and confirm it effects on tmor progression.

Results: Malignant tumors exhibit elevated level of cytosolic Musashi-1 (MSI1), which translocates into cytosol in response to stress and promote tumor progression. Cytosolic MSI1 forms a complex with AGO2 and stabilize or destabilize its target mRNAs by respectively binding to their 3´ untranslated region or coding domain sequence. Both MSI1 translocation and MSI1/AGO2 binding are essential for promoting tumor progression. Blocking MSI1 shuttling by either chemical inhibition or point mutation attenuates the growth of GBM-xenografts in mice. Importantly, overexpression of the C-terminus of MSI1 disrupts endogenous MSI1/AGO2 interaction and effectively reduces stress-induced tumor progression.

Conclusion: Our findings highlight novel molecular functions of MSI1 during stress-induced carcinomatous recurrence, and suggest a new therapeutic strategy for refractory malignancies by targeting MSI1 translocation and its interaction with AGOs.

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.

MicroRNA-331 inhibits development of gastric cancer through targeting musashi1

BACKGROUND

The molecular mechanisms involved in microRNAs (miRNAs) have been extensively investigated in gastric cancer (GC). However, how miR-331 regulates GC pathogenesis remains unknown.

AIM

To illuminate the effect of miR-331 on cell metastasis and tumor growth in GC.

METHODS

The qRT-PCR, CCK8, Transwell, cell adhesion, Western blot, luciferase reporter and xenograft tumor formation assays were applied to explore the regulatory mechanism of miR-331 in GC.

RESULTS

Downregulation of miR-331 associated with poor prognosis was detected in GC. Functionally, miR-331 suppressed cell proliferation, metastasis and tumor growth in GC. Further, miR-331 was verified to directly target musashi1 (MSI1). In addition, miR-331 inversely regulated MSI1 expression in GC tissues. Furthermore, upregulation of MSI1 weakened the inhibitory effect of miR-331 in GC.

CONCLUSION

miR-331 inhibited development of GC through targeting MSI1, which may be used as an indicator for the prediction and prognosis of GC.

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.

Immunoexpression of LGR4 and Β-Catenin in Gastric Cancer and Normal Gastric Mucosa

Background:

We evaluated the immunoexpression of LGR4 and β-catenin in primary gastric carcinomas, lymph node metastases and histologically normal gastric mucosa in the surgical margins of gastric primary tumours.

Methods:

We performed a cross-sectional, observational study, based on 75 gastric carcinoma specimens from gastrectomies conducted at the hospital of the Federal University of Ceará, Brazil. The samples were analysed by tissue microarray and immunohistochemistry. Chi-square, Fisher’s exact test and Pearson’s linear regression were used in this study.

Results:

LGR4 expression was greater in the histologically normal gastric mucosa (basal third of the epithelial thickness) of the tumour surgical resection margin than in the cases of primary carcinomas (P<0.001, mainly diffuse-histotype cancer margins), and also in the number of cells stained in the normal mucosa (P<0.0001). Primary intestinal-type carcinomas showed greater positivity for LGR4 than diffuse tumours (59% vs 13%, P<0.0001) and in these the positivity was higher in the metastases (P=0.0242). The membranous immunoexpression of β-catenin was ubiquitous in the normal mucosa and present in 2/3 of the positive carcinomas. In only one case, nuclear β-catenin expression was observed. Most LGR4-positive cases were stained for membranous β-catenin but not the opposite (P<0.01).

Conclusion:

LGR4 is a likely biomarker of stem cells in the normal gastric mucosa and carcinomas of the stomach, not specific to cancer cells and positively associated with cell proliferation. LGR4 immunoexpression is more frequent and found in a larger number of cells in normal tissues than in tumour samples. Expression of β-catenin in the junctional membrane-complex occurred predominantly, in positive cases of gastric carcinomas and very rarely in the nucleus. LGR4 apparently influenced the membranous expression of β-catenin. These findings suggest a controversial role for LGR4, related to proliferative status and inversely related to tumour progression, in contrast to most previous reports.

Impact of in vitro driven expression signatures of CD133 stem cell marker and tumor stroma on clinical outcomes in gastric cancers

Background

The CD133 transmembrane protein is a well-recognized stem cell marker that has been used to isolate putative cancer stem cell populations from gastric cancers (GCs). However, the molecular features or biomarkers underlying CD133 are largely unknown in GCs.

Methods

We performed gene expression profiling of CD133+ and CD133- cells sorted by flow cytometry from three GC cell lines to identify the CD133 expression signatures of GC. The CD133 expression signatures were investigated across publicly available expression profiles of multiple tumor types including GC and also for their relationship with patient survival.

Results

The CD133 signature genes defined as 177 upregulated genes and 129 downregulated genes in CD133+ cells compared to CD133- cells were enriched with genes involving the cell cycle and cytoskeleton, implying that cancer stem cells with unlimited self-renewal play cancer-initiating roles. The CD133 expression signatures in GC expression profiles were positively correlated with those of brain tumors expressing CD133 and human embryonic stem cells, emphasizing the transcriptional similarities across stem cell-related expression signatures. We also found that these stem cell expression signatures were inversely correlated with those representing tumor infiltrating immune and stromal cells. Additionally, high CD133 expression signatures were found in intestinal subtypes and low tumor stage GCs as well as in those with microsatellite instabilities and high mutation burdens. As examined across 20 additional tumor types, both the expression signatures representing CD133 and stromal cells were unfavorable prognostic features; however, their impact were variable across tumor types.

Conclusions

The transcriptional activities of CD133 and those of stromal cells representing the activity of stem cells and level of epithelial-to-mesenchymal transition, respectively, may be inversely correlated with each other across multiple tumor types including GC. This relationship may be a confounding factor and should therefore be considered when evaluating the clinical relevance of stem cell-related markers.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5332-y) contains supplementary material, which is available to authorized users.

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.

The role of GLI-SOX2 signaling axis for gemcitabine resistance in pancreatic cancer

Pancreatic cancer, mostly pancreatic ductal adenocarcinomas (PDAC), is one of the most lethal cancers, with a dismal median survival around 8 months. PDAC is notoriously resistant to chemotherapy. Thus far, numerous attempts using novel targeted therapies and immunotherapies yielded limited clinical benefits for pancreatic cancer patients. It is hoped that delineating the molecular mechanisms underlying drug resistance in pancreatic cancer may provide novel therapeutic options. Using acquired gemcitabine resistant pancreatic cell lines, we revealed an important role of the GLI-SOX2 signaling axis for regulation of gemcitabine sensitivity in vitro and in animal models. Down-regulation of GLI transcriptional factors (GLI1 or GLI2), but not SMO signaling inhibition, reduces tumor sphere formation, a characteristics of tumor initiating cell (TIC). Down-regulation of GLI transcription factors also decreased expression of TIC marker CD24. Similarly, high SOX2 expression is associated with gemcitabine resistance whereas down-regulation of SOX2 sensitizes pancreatic cancer cells to gemcitabine treatment. We further revealed that elevated SOX2 expression is associated with an increase in GLI1 or GLI2 expression. Our ChIP assay revealed that GLI proteins are associated with a putative Gli binding site within the SOX2 promoter, suggesting a more direct regulation of SOX2 by GLI transcription factors. The relevance of our findings to human disease was revealed in human cancer specimens. We found that high SOX2 protein expression is associated with frequent tumor relapse and poor survival in stage II PDAC patients (all of them underwent gemcitabine treatment), indicating that reduced SOX2 expression or down-regulation of GLI transcription factors may be effective in sensitizing pancreatic cancer cells to gemcitabine treatment.

Towards precision medicine: linking genetic and cellular heterogeneity in gastric cancer

Molecular and cellular heterogeneity are phenomena that are revolutionizing oncology research and becoming critical to the idea of personalized medicine. Recent comprehensive molecular profiling has identified molecular subtypes of gastric cancer (GC) and linked them to clinical information. Moreover, GC stem cells (gCSCs) have been identified and found to be responsible for GC initiation and progression, Helicobacter pylori oncogenic action and therapy resistance. Addressing molecular heterogeneity is critical for achieving an optimal therapeutic approach against GC as well as targeting gCSCs. In this review, we outline the implications of molecular and cellular heterogeneity in the treatment of GC and we summarize the clinical impact of the most important regulators of gCSCs.

Expression of PD-L1 and SOX2 during rectal tumourigenesis: Potential mechanisms for immune escape and tumour cell invasion

Immunoediting is defined as a process whereby tumour cells develop the capacity to escape immune cell recognition. Accumulating evidence suggests that cancer stem-like cells (CSCs) have an enhanced capacity to interact with the immune system. The expression of CSCs and immune cell-associated markers has been demonstrated to change with disease progression from premalignant lesions to invasive cancer. The present study investigated the expression of putative CSC and immune cell-associated markers in different stages of progression from dysplasia to invasive malignancy in rectal lesions. Immunohistochemistry was performed for the CSC markers Lgr5 and SOX2 and the immune-associated markers CD8, Foxp3 and PD-L1 in 79 cases of endoscopically-excised rectal lesions, ranging from low grade adenoma (LG) to invasive adenocarcinoma (AdCa). CD8 and Foxp3 expression significantly increased with advances in disease progression [AdCa vs. LG: Odds ratio (OR) 4.33; 95% confidence interval (CI), 1.16–16.3; P=0.03 and OR, 40.5; 95% CI, 6.57–249.6; P<0.0001, respectively]. An increase in programmed death-ligand 1 (PD-L1) expression was also observed with disease progression (OR, 24.0; 95% CI, 4.23–136.2; P=0.0003). The expression of sex determining region Y-box 2 (SOX2) did not correlate with disease progression, although an elevated expression was observed in areas with high grade dysplasia. Increased PD-L1 expression may be a mechanism by which tumour cells evade immune recognition, facilitating tumour cell invasion in rectal cancer. The expression of SOX2 in areas with high grade dysplasia may indicate the de-differentiation of tumour cells, or the activation of migration pathways for invasion.

CD133 Expression as a Helicobacter pylori-independent Biomarker of Gastric Cancer Progression

BACKGROUND/AIM

Gastric adenocarcinoma is the fourth most common cancer worldwide. While gastric cancer prevalence varies globally and incidence rates are decreasing in the West, many cases continue to be diagnosed at an advanced stage and the 5-year survival rate still falls below 30%. Early treatment of gastric cancer by endoscopic and/or surgical therapy may decrease mortality; yet reliable, universally applicable biomarkers for early detection of gastric cancer have still not been established.

MATERIALS AND METHODS

The present work compares the expression of CD133 (prominin-1), a potential biomarker of disease progression in gastric cancer, between independent cohorts of H. pylori (+) and H. pylori (-) patients at each respective stage of carcinogenesis. H. pylori (-) patients (N=45) who underwent gastric biopsy at the Moffitt Cancer Center (MCC) in Tampa, Florida, and H. pylori (+) patients (N=59) who underwent gastric biopsy at the Instituto de Patologia Mejia Jimenez (IPMJ) in Cali, Colombia were evaluated and immunostained for CD133.

RESULTS

A statistically significant increase in CD133 expression (in terms of the Allred score) was observed between all stages of progression (normal mucosa, inflammation/metaplasia, low-grade dysplasia and gastric adenocarcinoma) for each respective patient cohort. No statistically significant difference in CD133 expression at each respective stage of disease was observed between the H. pylori-positive and negative-cohorts.

CONCLUSION

The observation of distinct stepwise increases in CD133 expression in both patient cohorts, and the lack of any significant difference between groups, suggests that CD133 expression may serve as a biomarker for early detection of gastric cancer independent of bacterial status and strain, and corresponding differences in disease histomorphology and classification. This warrants further validation on larger independent cohorts across multiple geographic regions and incorporating multiple bacterial strain types.

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.

Clinical significance of putative markers of cancer stem cells in gastric cancer: A retrospective cohort study

Cancer stem cells (CSCs) are thought as the source of tumor maintaining and many CSCs markers have been identified. Regarding the heterogeneity in gastric cancer (GC), TNM stage is not enough to accurately predict the prognosis. The aim of this study was to investigate the clinical significance of CSCs markers (Lgr5, Oct4, CD133, EpCAM, CD54 and Sox2) and establish a new model based on these markers to accurately predict prognosis of GC. We retrospectively enrolled 377 GC tissues from January 2006 to October 2012 to perform immunohistochemistry (IHC), and 93 pairs of GC tissues and corresponding adjacent normal gastric tissues to perform quantitative PCR (qPCR) from December 2011 to October 2012. The clinicopathological and follow-up characteristics were collected. In IHC, Oct4, CD133 and EpCAM were independently related to tumor progression, while Sox2 were associated with well or moderate differentiation (all p<0.05). Cox regression showed that Oct4-EpCAM was an independently prognostic factor, indicating that double low expression of Oct4-EpCAM group had significantly better prognosis than control group (p=0.035). Regarding qPCR, CD133 was an independent prognostic factor, showing that the prognosis of patients with CD133 high expression was significantly worse than that of patients with CD133 low expression (p<0.001). The prognostic prediction accuracy of nomogram based on Oct4-EpCAM expression in IHC was significantly better than TNM stage alone (p=0.003). Low expressions of Oct4-EpCAM in IHC and CD133 in qPCR were favorable prognostic factors in GC. The nomogram based on Oct4-EpCAM was valuable in prognostic prediction of GC patients.

GLI1-mediated regulation of side population is responsible for drug resistance in gastric cancer

Gastric cancer is the third leading cause of cancer-related mortality worldwide. Chemotherapy is frequently used for gastric cancer treatment. Most patients with advanced gastric cancer eventually succumb to the disease despite some patients responded initially to chemotherapy. Thus, identifying molecular mechanisms responsible for cancer relapse following chemotherapy will help design new ways to treat gastric cancer. In this study, we revealed that the residual cancer cells following treatment with chemotherapeutic reagent cisplatin have elevated expression of hedgehog target genes GLI1, GLI2 and PTCH1, suggestive of hedgehog signaling activation. We showed that GLI1 knockdown sensitized gastric cancer cells to CDDP whereas ectopic GLI1 expression decreased the sensitivity. Further analyses indicate elevated GLI1 expression is associated with an increase in tumor sphere formation, side population and cell surface markers for putative cancer stem cells. We have evidence to support that GLI1 is critical for maintenance of putative cancer stem cells through direct regulation of ABCG2. In fact, GLI1 protein was shown to be associated with the promoter fragment of ABCG2 through a Gli-binding consensus site in gastric cancer cells. Disruption of ABCG2 function, through ectopic expression of an ABCG2 dominant negative construct or a specific ABCG2 inhibitor, increased drug sensitivity of cancer cells both in culture and in mice. The relevance of our studies to gastric cancer patient care is reflected by our discovery that high ABCG2 expression was associated with poor survival in the gastric cancer patients who underwent chemotherapy. Taken together, we have identified a molecular mechanism by which gastric cancer cells gain chemotherapy resistance.

Toward early detection of Helicobacter pylori-associated gastric cancer

BACKGROUND

Gastric cancer is typically diagnosed at a late stage, leading to poor prognoses. Helicobacter pylori is responsible for 70% of gastric cancers globally, and patients with this bacterial infection often present with early stages of the carcinogenic pathway such as inflammation or gastritis. Although many patients continue to progress to advanced-stage disease after antibacterial treatment, there are no follow-up screening protocols for patients with a history of H. pylori.

METHODS

Several biomarkers (Lgr5, CD133, CD44) become upregulated during gastric carcinogenesis. A logistic regression model is developed using clinical data from 59 patients at different stages of the carcinogenic pathway to identify the likelihood of being at an advanced stage of disease for all combinations of age, sex, and marker positivity. Using these likelihood distributions and the observed rate of marker positivity increase, time to high likelihood (probability >0.8) of advanced disease for individual patients is predicted.

RESULTS

A strong correlation between marker positivity and disease stage was found for all three markers. Disease stage was accurately classified by the respective regression models for more than 86% of retrospective patients. Highly patient-specific predictions of time to onset of dysplasia were made, allowing the classification of 17 patients initially diagnosed with intestinal metaplasia into high-, intermediate-, or low-risk categories.

CONCLUSIONS

We present an approach designed to integrate pathology, mathematics, and statistics for detection of the earliest precancerous, treatable lesion. Given the simplicity and robustness of the framework, such technique has the potential to guide personalized screening schedules to minimize the risk of undetected malignant transformation.

High expression of intratumoral stromal proteins is associated with chemotherapy resistance in breast cancer

We studied the changes of intratumoral stromal proteins including THBS1, TNC, FN, SPARC and α-SMA, following neoadjuvant chemotherapy. The underlying mechanisms by which THBS1 and TNC regulated resistance to docetaxel were further studied using functional studies. 100 patients with newly diagnosed breast cancer were treated with alternating sequential doxorubicin and docetaxel. Immunohistochemistry (IHC) staining for stromal proteins was performed on pre- and post-treatment core biopsies respectively. THBS1 and TNC were further validated with IHC in an independent cohort of 31 patients. A high baseline combined expression score of the 5 stromal proteins predicted independently for poor progression-free (HR_adjusted 2.22, 95% CI 1.06–4.64) and overall survival (HR_adjusted 5.94, 95% CI 2.25–15.71). After 1–2 cycles of chemotherapy, increased expression of THBS1, TNC, FN, SPARC and α-SMA was seen in patients with subsequent pathological lymph node involvement at surgery. Increased expression of THBS1 and TNC compared to baseline was also seen in intrinsically resistant tumors, but not in sensitive ones. Both THBS1 and TNC-associated chemoresistance were confirmed in an independent validation cohort. Exogenous THBS1 and TNC protected MCF-7 cells against proliferation inhibition induced by docetaxel through activating integrin β1/mTOR pathway. Thus, up-regulation of THBS1, TNC, FN, SPARC and α-SMA following neoadjuvant chemotherapy was associated with chemotherapy resistance in breast cancer patients. Functional studies showed THBS1 and TNC to mediate chemoresistance through the integrin β1/mTOR pathway, suggesting that therapies targeting integrin β1/mTOR pathway may be a promising strategy to overcome chemotherapy resistance.

Systemic Inflammation Response Index (SIRI), cancer stem cells and survival of localised gastric adenocarcinoma after curative resection

PURPOSE

Systemic Inflammation Response Index (SIRI), based on peripheral neutrophil, monocyte, and lymphocyte counts, was recently developed and used as a marker to predict the survival of patients with malignant tumours. Cancer stem cells (CSCs) can contribute to gastric cancer progression and recurrence. It is not clear whether SIRI is associated with CSCs during gastric cancer development.

METHODS

The SIRI was developed in a training cohort of 455 gastric cancer patients undergoing curative resection between 2007 and 2009, and validated in a validation cohort of 327 patients from 2010 to 2011. CD44 + CSCs were measured on tumour sections by immunohistochemical analysis.

RESULTS

An optimal cut-off point for the SIRI of 0.82 divided the gastric cancer patients into a low SIRI group (SIRI < 0.82) and a high SIRI group (SIRI ≥ 0.82) in the training cohort. Compared with patients who had a SIRI < 0.82, patients who had a SIRI ≥ 0.82 had a shorter disease-free survival (DFS) (HR 2.529; 95% CI 1.922-3.326; p < 0.001) and shorter disease-special survival (DSS) (HR 2.692; 95% CI 2.022-3.585; p < 0.001) in the training cohort, comparable DFS and DSS findings were observed in the validation cohort, even for patients in pathological TNM stage of I subgroup. A SIRI ≥ 0.82 was significantly associated with older age, larger tumour, higher pathological TNM stage, lymphovascular invasion, and perineural invasion. Additionally, patients in the low SIRI group were prone to DFS and DSS benefits from postoperative adjuvant chemotherapy. Univariate and multivariate analyses revealed that SIRI was an independent predictor for DFS and DSS. Furthermore, gastric cancer patients with CD44 + CSCs scores had higher SIRI level (mean 1.198 vs. 0.835; p < 0.001). In patients with CD44 + CSCs, those with SIRI ≥ 0.82 had higher recurrence rates and shorter survival time than patients with SIRI < 0. 82.

CONCLUSIONS

SIRI was a useful prognostic indicator of poor outcomes in patients with gastric cancer and is a promising tool for gastric cancer treatment strategy decisions. The dismal outcomes in patients with high SIRI might be related to CSCs.

The role of GLI2-ABCG2 signaling axis for 5Fu resistance in gastric cancer

Gastric cancer is a leading cause of cancer-related mortality worldwide, and options to treat gastric cancer are limited. Fluorouracil (5Fu)-based chemotherapy is frequently used as a neoadjuvant or an adjuvant agent for gastric cancer therapy. Most patients with advanced gastric cancer eventually succumb to the disease despite the fact that some patients respond initially to chemotherapy. Thus, identifying molecular mechanisms responsible for chemotherapy resistance will help design novel strategies to treat gastric cancer. In this study, we discovered that residual cancer cells following 5Fu treatment have elevated expression of hedgehog (Hg) target genes GLI1 and GLI2, suggestive of Hh signaling activation. Hh signaling, a pathway essential for embryonic development, is an important regulator for putative cancer stem cells/residual cancer cells. We found that high GLI1/GLI2 expression is associated with some features of putative cancer stem cells, such as increased side population. We demonstrated that GLI2 knockdown sensitized gastric cancer cells to 5Fu treatment, decreased ABCG2 expression, and reduced side population. Elevated GLI2 expression is also associated with an increase in tumor sphere size, another marker for putative cancer stem cells. We believe that GLI2 regulates putative cancer stem cells through direct regulation of ABCG2. ABCG2 can rescue the GLI2 shRNA effects in 5Fu response, tumor sphere formation and side population changes, suggesting that ABCG2 is an important mediator for GLI2-associated 5Fu resistance. The relevance of our studies to gastric cancer patient care is reflected by our discovery that high GLI1/GLI2/ABCG2 expression is associated with a high incidence of cancer relapse in two cohorts of gastric cancer patients who underwent chemotherapy (containing 5Fu). Taken together, we have identified a molecular mechanism by which gastric cancer cells gain 5Fu resistance.

β-arrestin1-mediated acetylation of Gli1 regulates Hedgehog/Gli signaling and modulates self-renewal of SHH medulloblastoma cancer stem cells

Background

Aberrant Sonic Hedgehog/Gli (Hh/Gli) signaling pathway is a critical regulator of Sonic hedgehog medulloblastoma (SHH-MB). Cancer stem cells (CSCs), thought to be largely responsible for tumor initiation, maintenance, dissemination and relapse, have been identified in SHH-MB. Since we previously demonstrated that Hh/Gli signaling controls CSCs features in SHH-MB and that in these tumors miR-326 is down regulated, here we investigated whether there is a functional link between Hh/Gli signaling and miR-326.

Methods

We evaluated β-arrestin1 (Arrb1) and its intragenic miR-326 levels in CSCs derived from SHH-MB. Subsequently, we modulated the expression of Arrb1 and miR-326 in CSCs in order to gain insight into their biological role. We also analyzed the mechanism by which Arrb1 and miR-326 control Hh/Gli signaling and self-renewal, using luciferase and protein immunoprecipitation assays.

Results

Low levels of Arrb1 and miR-326 represent a feature of CSCs derived from SHH-MB. We observed that re-expression of Arrb1 and miR-326 inhibits Hh/Gli signaling pathway at multiple levels, which cause impaired proliferation and self-renewal, accompanied by down regulation of Nanog levels. In detail, miR-326 negatively regulates two components of the Hh/Gli pathway the receptor Smoothened (Smo) and the transcription factor Gli2, whereas Arrb1 suppresses the transcriptional activity of Gli1, by potentiating its p300-mediated acetylation.

Conclusions

Our results identify a new molecular mechanism involving miR-326 and Arrb1 as regulators of SHH-MB CSCs. Specifically, low levels of Arrb1 and miR-326 trigger and maintain Hh/Gli signaling and self-renewal.

Overexpression of Musashi-1 protein is associated with progression and poor prognosis of gastric cancer

Musashi-1, an evolutionally conserved RNA-binding protein, has been implicated in the promotion of pathological stem cell proliferation, including tumorigenesis. The objective of the present study was to evaluate the expression of Musashi-1 protein and its implications in the progression and prognosis of gastric cancer. The expression level of Musashi-1 protein in gastric cancer was determined by western blotting and immunohistochemistry, and compared with the clinicopathological parameters. The present study revealed that the expression level of Musashi-1 protein in gastric cancer was significantly upregulated and correlated with the tumor size, tumor-node-metastasis (TNM) stage, Lauren classification, depth of invasion, vessel invasion, lymph node metastasis and distant metastasis. The mean survival time for patients with low expression levels of Musashi-1 was significantly longer compared with patients with high expression levels of Musashi-1. For each TNM stage, the mean survival time for patients with a low Musashi-1 expression levels was also significantly longer compared with patients with a high Musashi-1 expression level. Notably, TNM stage II patients with a low Musashi-1 expression level demonstrated a longer mean survival time compared with TNM stage I patients with high Musashi-1 expression level (56.8 vs. 42.3 months; P=0.001), and TNM stage III patients with low Musashi-1 expression level exhibited a longer mean survival time compared with TNM stage II patients with a high Musashi-1 expression level (44.0 vs. 33.8 months; P=0.034). Multivariate Cox's regression test demonstrated that Musashi-1 protein expression level was an independent prognostic indicator for the survival rate of the patients with gastric cancer. The results of the present study highlighted an important role for Musashi-1 protein in the progression of gastric cancer. The detection of the Musashi-1 protein expression level alone or in combination with TNM staging may aid the prediction of the prognosis of patients with gastric cancer.

Msi1 promotes tumor progression by epithelial-to-mesenchymal transition in cervical cancer

Musashi1 (Msi1) is an RNA-binding protein that has been reported to be a pivotal regulator in tumorigenesis and progression in several cancers. However, its function and mechanism in cervical cancer is still unknown. In this study, Msi1 expression was found elevated in cervical cancers by immunohistochemistry and correlated with poor outcomes. Then, endogenous Msi1 was silenced in cervical cancer cell lines by short hairpin RNA, and its function and mechanism were determined. The results showed that the silencing of Msi1 in SiHa and HeLa cells inhibited the cells' migratory and invasive abilities in vitro and tumor progression in vivo. Epithelial-to-mesenchymal transition (EMT) markers were down-regulated, and Wnt activity was inhibited by the silencing of Msi1. In clinical tissues, positive correlations between Msi1 and EMT markers were found. In conclusion, Msi1, a diagnostic marker and potential therapeutic target, promoted the EMT progression through activation of the Wnt signaling pathway in cervical cancers, thereby contributing to poor prognosis.

Identification of stem-like cells and clinical significance of candidate stem cell markers in gastric cancer

The existence of gastric cancer stem cells (CSCs) has not been definitively proven and specific cell surface markers for identifying gastric CSCs have largely not been identified. Our research aimed to isolate potential gastric CSCs and clarify their clinical significance, while defining markers for GCSC identification and verification. Here, we report that spheroid cells possess stem cell-like properties, and overexpress certain stem cell markers. CD133 or CD44-positive cells also exhibit properties of CSCs. The expression of Oct4, Sox2, Gli1, CD44, CD133, p-AKT, and p-ERK was significantly higher in metastatic lesions compared to that in primary lesions. Elevated expression of some of these proteins was correlated with a more aggressive phenotype and poorer prognosis, including Oct4, Sox2, Gli1, CD44, and p-ERK. Multivariate Cox proportional hazards model analysis showed that only CD44 is an independent factor. Knockdown of CD44 down-regulated the stem cell-like properties, which was accompanied by the down-regulation of p-ERK and Oct4. Oct4 overexpression could reverse the decreased CSCs properties induced by CD44 knockdown. Taken together, our research revealed that spheroid cell culture, and CD133 or CD44-labeled FACS methods can be used to isolate gastric CSCs. Some CSC markers have clinical significance in predicting the prognosis. CD44 is an independent prognostic factor and maintains the properties of CSCs in CD44-p-ERK-Oct4 positive feedback loop.

Simvastatin-induced breast cancer cell death and deactivation of PI3K/Akt and MAPK/ERK signalling are reversed by metabolic products of the mevalonate pathway

Statins purportedly exert anti-tumoral effects on breast cancer. However, the biologic mechanisms for these actions are not fully elucidated. The aims of this study were 1) to explore the effects of simvastatin on apoptosis, proliferation as well as PI3K/Akt/mTOR and MAPK/ERK pathway in a window-of-opportunity breast cancer trial; 2) to further confirm findings from the clinical trial by functional studies; 3) to explore the regulatory role of mevalonate pathway on the anti-tumoral effects of simvastatin. In clinical samples, simvastatin led to increase in cleaved caspase-3 (p = 0.002) and decreased trend for Ki67 (p = 0.245). Simvastatin markedly suppressed PI3K/Akt/mTOR signalling by activating PTEN (p = 0.005) and by dephosphorylating Akt (p = 0.002) and S6RP (p = 0.033); it also inhibited MAPK/ERK pathway by dephosphorylating c-Raf (p = 0.018) and ERK1/2 (p = 0.002). In ER-positive (MCF-7, T47D) and ER-negative (MDA-MB-231, BT-549) breast cancer cells, simvastatin treatment consistently induced apoptosis and inhibited proliferation by deregulating caspase cascades and cell cycle proteins in a dose dependent manner. Concordantly, simvastatin strongly suppressed PI3K/Akt/mTOR pathway by enhancing PTEN expression and by further sequentially dephosphorylating downstream cascades including Akt, mTOR, p70S6K, S6RP and 4E-BP1. Furthermore, simvastatin significantly inhibited MAPK/ERK pathway by dephosphorylating sequential cascades such as c-Raf, MEK1/2 and ERK1/2. These simvastatin anti-tumoral effects were reversed by metabolic products of the mevalonate pathway, including mevalonate, farnesyl pyrophosphate and geranylgeranyl pyrophosphate. These findings shed light on the biological and potential anti-tumoral effects of simvastatin in breast cancer.

Prognostic impact of CD44-positive cancer stem-like cells at the invasive front of gastric cancer

Background:

The invasive tumour front may provide prognostic information. We examined the relationship between the presence of cancer stem cells (CSCs) at the invasive tumour front and prognosis in gastric cancer (GC).

Methods:

CD44 is a CSC marker; accordingly, CD44 standard (CD44s), CD44 variant-6 (CD44v6), and CD44 variant-9 (CD44v9) expression were examined in 123 resected primary GCs and the clinical significance of CSCs at the invasive tumour front was analysed.

Results:

Thirteen (10.6%), 79 (64.2%), and 47 (38.2%) GCs were CD44s-, CD44v6-, and CD44v9-positive, respectively. Patients with CD44-positive expression at the invasive tumour front had significantly poorer disease-specific survival than those with negative expression (CD44s: P<0.00001, CD44v6: P=0.013, CD44v9: P=0.0002). CD44s expression at the invasive tumour front was an independent prognostic factor in resectable GC patients (hazard ratio=3.13; 95% confidence interval, 1.09–9.01; P=0.035) and was significantly associated with peritoneal (P<0.001), lymphatic (P<0.001), and haematogenous recurrences (P=0.008). In addition, the number of CD44 isoforms expressed in cancer cells at the invasive tumour front was associated with patient prognosis. No conventional clinicopathological factors were independently associated with CD44 expression at the invasive tumour front.

Conclusions:

CD44-positive cancer stem-like cells at the invasive tumour front indicate poor survival and can be a unique biological prognostic factor for GC.

MiR-330-3p inhibits gastric cancer progression through targeting MSI1

Increasing evidences demonstrated that microRNAs (miRNAs) play critical roles in the human tumor development and progression. In our study, we found that miR-330-3p expression was downregulated in gastric cancer cell lines and tissues. Ectopic expression of miR-330-3p suppressed the gastric cancer cell proliferation, colony formation and migration. Overexpression of miR-330-3p promoted E-cadherin expression and inhibited the expression of N-cadherin, vimentin and snail. We identified Musashi-1 (MSI1) as a direct target gene of miR-330-3p in gastric cancer cell. In addition, MSI1 was upregulated in gastric cancer cell lines and tissues and the MSI1 expression was inversely correlated with miR-330-3p expression in gastric cancer tissues. MiR-330-3p expression was increased in gastric cancer cells after treated with histone deacetylase inhibitor trichostatin A (TSA) and DNA methylation inhibitor 5-aza-CdR (AZA). These indicated that downregulated expression of miR-330-3p was partly mediated by gene promoter region hypermethylation. These results suggested that miR-330-3p acted as a tumor suppressor gene in GC.

CD133 overexpression correlates with clinicopathological features of gastric cancer patients and its impact on survival: a systematic review and meta-analysis

Background

CD133 is one of the most commonly used markers of cancer stem cells (CSCs), which are characterized by their ability for self-renewal and tumorigenicity. However, the clinical and prognostic significance of CD133 in gastric cancer remains controversial. To clarify a precise determinant of the clinical significance of CD133, we conducted a systematic review and meta-analysis to elucidate the correlation of CD133 overexpression with prognosis and clinicopathological features of GC patients.

Methods

A search in the Cochrane Library, Pubmed, Medline, Web of Knowledge and Chinese CNKI, CBM (up to Jun 30, 2015) was performed using the following keywords gastric cancer, CD133, AC133, prominin-1, etc. Electronic searches were supplemented by hand searching reference lists, abstracts and proceedings from meetings. Outcomes included overall survival and various clinicopathological features. Two reviewers independently screened the literature according to the inclusion and exclusion criteria, extracted the data, and assessed the methodological quality of the included studies, and then RevMan 5.2.0 software was used for meta-analysis.

Results

A total of 603 gastric cancer patients from 8 studies were included. The results of the meta-analyses showed that, there were significant differences of CD133 expression in the following comparisons: gastric cancer tissues vs. normal esophageal tissue (OR = 3.49, 95% CI [2.48, 490], P < 0.00001), lymph node metastasis vs. non-lymph node metastasis (OR = 2.75, 95% CI [1.99, 3.81], P < 0.00001), distant metastasis vs. non-distant metastasis (OR = 2.38, 95%CI [1.47, 3.85], P < 0.0004), clinical stages III~IV vs. clinical stages I~II (OR = 2.83, 95% CI [2.13, 3.76], P < 0.00001), as well as the accumulative 5-year overall survival rates of CD133-positive vs. CD133-negative patients (OR = 0.23, 95% CI [0.16, 0.33], P < 0.00001).

Conclusion

Overexpression of CD133 is associated with lymph node metastasis, distant metastasis, poor TNM stage. Additionally, CD133-positive gastric cancer patients had worse prognosis. Our results indicate that CD133 may be involved in the carcinogenesis of gastric cancer. Evaluation of cytoplasmic CD133 overexpression in gastric cancer tissue sections may be useful in the future as a novel prognostic factor. Nevertheless, due to the poor quality and small sample size of included trials, more well-designed multi-center randomized controlled trials should be performed.

Therapeutic Effectiveness of Anticancer Phytochemicals on Cancer Stem Cells

Understanding how to target cancer stem cells (CSCs) may provide helpful insights for the development of therapeutic or preventive strategies against cancers. Dietary phytochemicals with anticancer properties are promising candidates and have selective impact on CSCs. This review summarizes the influence of phytochemicals on heterogeneous cancer cell populations as well as on specific targeting of CSCs.

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.

Emerging molecular basis of hematogenous metastasis in gastric cancer

Lymphatic metastasis is commonly observed in gastric cancer (GC), but hematogenous metastasis is more likely responsible for the cancer-related mortality. Since Stephen Paget first introduced the “seed and soil hypothesis” a century ago, growing evidence recognizes that numerous essential secreted factors and signaling pathway effectors participate in the pre-metastatic niche formation and distant organ metastasis. The cross-talk between GC cells and surrounding microenvironment may consist of a series of interrelated steps, including epithelial mesenchymal transition, intravasation into blood vessels, circulating tumor cell translocation, and secondary organ metastasis. Secreted factors including vascular endothelial growth factor (VEGF), matrix metalloproteinases and cancer-derived extracellular vesicles, especially exosomes, are essential in formation of premetastatic niche. Circulating tumor cells and microRNAs represent as ‘‘metastatic intermediates’’ between primary tumors and sites of dissemination. Many biomarkers have been identified as novel metastatic markers and prognostic effectors. In addition, molecular therapy has been designed to target biomarkers such as growth factors (human epidermal growth factor receptor 2, VEGF) and chemokines, although they have not clearly proven to be effective in inhibiting GC metastasis in clinical trials. In this review, we will systematically discuss the emerging molecules and their microenvironment in hematogenous metastasis of GC, which may help us to find new therapeutic strategies in the future.