Sonic hedgehog mediates the proliferation and recruitment of transformed mesenchymal stem cells to the stomach

Therapeutic potential of hedgehog signaling in advanced cancer types

In this chapter, we have made an attempt to elucidate the relevance of hedgehog signaling pathway in tumorigenesis. Here, we have described different types of hedgehog signaling (canonical and non-canonical) with emphasis on the different mechanisms (mutation-driven, autocrine, paracrine and reverse paracrine) it adopts during tumorigenesis. We have discussed the role of hedgehog signaling in regulating cell proliferation, invasion and epithelial-to-mesenchymal transition in both local and advanced cancer types, as reported in different studies based on preclinical and clinical models. We have specifically addressed the role of hedgehog signaling in aggressive neuroendocrine tumors as well. We have also elaborated on the studies showing therapeutic relevance of the inhibitors of hedgehog signaling in cancer. Evidence of the crosstalk of hedgehog signaling components with other signaling pathways and treatment resistance due to tumor heterogeneity have also been briefly discussed. Together, we have tried to put forward a compilation of the studies on therapeutic potential of hedgehog signaling in various cancers, specifically aggressive tumor types with a perspective into what is lacking and demands further investigation.

Hedgehog/GLI and gastric cancer: Research progress and current status

Hedgehog/GLI (Hh/GLI) is an important signaling pathway. It has been confirmed in various cancer studies that mutated or dysregulated Hh signals may be the behavioral phenotype of tumors, leading to the occurrence of various cancers. The abnormally activated Hh pathway endows tumor cells with a tendency to occur, proliferate, and migrate. In recent years, studies have found that the Hh signaling pathway induces gastric cancer (GC) invasion and epithelial mesenchymal transition. This article reviews the research progress and current status of Hh/GLI related to GC. Unveiling the new veil of GC occurrence will open a new approach for targeted therapy of this malignancy.

Molecular mechanisms underlying the action of carcinogens in gastric cancer with a glimpse into targeted therapy

BACKGROUND

Gastric cancer imposes a substantial global health burden despite its overall incidence decrease. A broad spectrum of inherited, environmental and infectious factors contributes to the development of gastric cancer. A profound understanding of the molecular underpinnings of gastric cancer has lagged compared to several other tumors with similar incidence and morbidity rates, owing to our limited knowledge of the role of carcinogens in this malignancy. The International Agency for Research on Cancer (IARC) has classified gastric carcinogenic agents into four groups based on scientific evidence from human and experimental animal studies. This review aims to explore the potential comprehensive molecular and biological impacts of carcinogens on gastric cancer development and their interactions and interferences with various cellular signaling pathways.

CONCLUSIONS

In this review, we highlight recent clinical trial data reported in the literature dealing with different ways to target various carcinogens in gastric cancer. Moreover, we touch upon other multidisciplinary therapeutic approaches such as surgery, adjuvant and neoadjuvant chemotherapy. Rational clinical trials focusing on identifying suitable patient populations are imperative to the success of single-agent therapeutics. Novel insights regarding signaling pathways that regulate gastric cancer can potentially improve treatment responses to targeted therapy alone or in combination with other/conventional treatments. Preventive strategies such as control of H. pylori infection through eradication or immunization as well as dietary habit and lifestyle changes may reduce the incidence of this multifactorial disease, especially in high prevalence areas. Further in-depth understanding of the molecular mechanisms involved in the role of carcinogenic agents in gastric cancer development may offer valuable information and update state-of-the-art resources for physicians and researchers to explore novel ways to combat this disease, from bench to bedside. A schematic outlining of the interaction between gastric carcinogenic agents and intracellular pathways in gastric cancer H. pylori stimulates multiple intracellular pathways, including PI3K/AKT, NF-κB, Wnt, Shh, Ras/Raf, c-MET, and JAK/STAT, leading to epithelial cell proliferation and differentiation, apoptosis, survival, motility, and inflammatory cytokine release. EBV can stimulate intracellular pathways such as the PI3K/Akt, RAS/RAF, JAK/STAT, Notch, TGF-β, and NF-κB, leading to cell survival and motility, proliferation, invasion, metastasis, and the transcription of anti-apoptotic genes and pro-inflammatory cytokines. Nicotine and alcohol can lead to angiogenesis, metastasis, survival, proliferation, pro-inflammatory, migration, and chemotactic by stimulating various intracellular signaling pathways such as PI3K/AKT, NF-κB, Ras/Raf, ROS, and JAK/STAT. Processed meat contains numerous carcinogenic compounds that affect multiple intracellular pathways such as sGC/cGMP, p38 MAPK, ERK, and PI3K/AKT, leading to anti-apoptosis, angiogenesis, metastasis, inflammatory responses, proliferation, and invasion. Lead compounds may interact with multiple signaling pathways such as PI3K/AKT, NF-κB, Ras/Raf, DNA methylation-dependent, and epigenetic-dependent, leading to tumorigenesis, carcinogenesis, malignancy, angiogenesis, DNA hypermethylation, cell survival, and cell proliferation. Stimulating signaling pathways such as PI3K/Akt, RAS/RAF, JAK/STAT, WNT, TGF-β, EGF, FGFR2, and E-cadherin through UV ionizing radiation leads to cell survival, proliferation, and immortalization in gastric cancer. The consequence of PI3K/AKT, NF-κB, Ras/Raf, ROS, JAK/STAT, and WNT signaling stimulation by the carcinogenic component of Pickled vegetables and salted fish is the Warburg effect, tumorigenesis, angiogenesis, proliferation, inflammatory response, and migration.

Overexpression of sonic hedgehog enhances the osteogenesis in rat ectomesenchymal stem cells

Ectoderm-derived mesenchymal stem cells (EMSCs) were used as potential seed cells for bone tissue engineering to treat bone defects due to their capability of rapid proliferation and osteogenic differentiation. Sonic hedgehog (Shh) signaling was reported to play an important role in the development of bone tissue, but its role is not understood. The present study investigated the role of Shh molecule in osteogenic differentiation of rat EMSCs in vitro. Rat EMSCs were isolated form nasal respiratory mucosa and identified with immunofluorescence and analyzed with other methods, including reverse transcriptase polymerase chain reaction (qPCR) and western blotting. EMSCs expressed CD90, CD105, nestin, and vimentin. On the seventh day of osteogenic induction, expression levels of Shh and Gli1 was higher according to the result of qPCR and Western blotting. After induction for 14 days, higher alkaline phosphatase (ALP) activity and more mineralized nodules were seen in comparison to the cells that did not undergo induction. Shh signaling appears to enhance osteogenic differentiation of rat EMSCs, suggesting that Shh signaling directs the lineage differentiation of ectodermal stem cells and represents a promising strategy for skeletal tissue regeneration.

Mesenchymal Stem Cells in Gastric Cancer: Vicious but Hopeful

Tumor progression depends on the collaborative interactions between tumor cells and the surrounding stroma. First-line therapies direct against cancer cells may not reach a satisfactory outcome, such as gastric cancer (GC), with high risk of recurrence and metastasis. Therefore, novel treatments and drugs target the effects of stroma components are to be promising alternatives. Mesenchymal stem cells (MSC) represent the decisive components of tumor stroma that are found to strongly affect GC development and progression. MSC from bone marrow or adjacent normal tissues express homing profiles in timely response to GC-related inflammation signals and anchor into tumor bulks. Then the newly recruited “naïve” MSC would achieve phenotype and functional alternations and adopt the greater tumor-supporting potential under the reprogramming of GC cells. Conversely, both new-comers and tumor-resident MSC are able to modulate the tumor biology via aberrant activation of oncogenic signals, metabolic reprogramming and epithelial-to-mesenchymal transition. And they also engage in remodeling the stroma better suited for tumor progression through immunosuppression, pro-angiogenesis, as well as extracellular matrix reshaping. On the account of tumor tropism, MSC could be engineered to assist earlier diagnosis of GC and deliver tumor-killing agents precisely to the tumor microenvironment. Meanwhile, intercepting and abrogating vicious signals derived from MSC are of certain significance for the combat of GC. In this review, we mainly summarize current advances concerning the reciprocal metabolic interactions between MSC and GC and their underlying therapeutic implications in the future.

Airway epithelial cell differentiation relies on deficient Hedgehog signalling in COPD

BACKGROUND

Hedgehog (HH) pathway is constantly under scrutiny in the context of organ development. Lung morphogenesis requires HH signalling which participates thereafter to the pulmonary homeostasis by regulating epithelial cell quiescence and repair. Since epithelial remodelling is a hallmark of Chronic Obstructive Pulmonary Disease (COPD), we investigated whether the main molecular actors of HH pathway participate to airway epithelial cell differentiation and we analysed their alterations in COPD patients.

METHODS

Sonic HH (Shh) secretion was assessed by ELISA in airway epithelial cell (AEC) air-liquid interface culture supernatants. HH pathway activation was evaluated by RT-qPCR, western blot and immunostaining. Inhibition of HH signalling was achieved upon Shh chelation during epithelial cell differentiation. HH pathway core components localization was investigated in lung tissues from non-COPD and COPD patients.

FINDINGS

We demonstrate that progenitors of AEC produced Shh responsible for the activation of HH signalling during the process of differentiation. Preventing the ligand-induced HH activation led to the establishment of a remodelled epithelium with increased number of basal cells and reduced ciliogenesis. Gli2 activating transcription factor was demonstrated as a key-element in the regulation of AEC differentiation. More importantly, Gli2 and Smo were lost in AEC from COPD patients.

INTERPRETATION

Our data suggest that HH pathway is crucial for airway epithelial cell differentiation and highlight its role in COPD-associated epithelial remodelling.

The role of hedgehog signaling in gastric cancer: molecular mechanisms, clinical potential, and perspective

Patients with advanced gastric cancer usually have a poor prognosis and limited therapeutic options. Overcoming this challenge requires novel targets and effective drugs. The Hedgehog (Hh) signaling pathway plays a crucial role in the development of the gastrointestinal tract and maintenance of the physiologic function of the stomach. Aberrantly activated Hh signaling is implicated in carcinogenesis as well as maintenance of cancer stem cells. Somatic mutations in the components of Hh signaling (PTCH1 and SMO) have been shown to be a major cause of basal cell carcinoma, and dozens of Hh inhibitors have been developed. To date, two inhibitors (GDC-0449 and LDE225) have been approved by the U.S. Food and Drug Administration to treat basal cell carcinoma and medulloblastoma. Here, we review the role of the Hh signaling in the carcinogenesis and progression of gastric cancer and summarize recent findings on Hh inhibitors in gastric cancer. Hedgehog signaling is often aberrantly activated and plays an important role during inflammation and carcinogenesis of gastric epithelial cells. Further study of the precise mechanisms of Hh signaling in this disease is needed for the validation of therapeutic targets and evaluation of the clinical utility of Hh inhibitors for gastric cancer.

Sonic Hedgehog Ligand: A Role in Formation of a Mesenchymal Niche in Human Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is characterised by desmoplasia, thought to support progression and chemotherapeutic resistance. The Hedgehog pathway is known to play an important role in this cancer. While the upregulation of Sonic hedgehog (Shh) in the epithelium of PDAC is known, we investigated its expression in the tumour microenvironment in order to find new targets for new chemotherapeutical approaches. Immunohistochemistry was used for the investigation of Shh and Vimentin in primary human pancreatic tissues. Gene (qRT-PCR) and protein (immunofluorescence) expression of Shh, αSMA (a marker of the mesenchymal phenotype) and periostin (a marker of mesenchymal cells within a mixed population) were investigated in in vitro cell models. Shh expression was significantly upregulated in the stromal and epithelial compartments of poorly-differentiated PDAC samples, with a strong correlation with the amount of stroma present. Characterisation of stromal cells showed that there was expression of Shh ligand in a mixed population comprising αSMA+ myofibroblasts and αSMA- mesenchymal stem cells. Moreover, we demonstrated the interaction between these cell lines by showing a higher rate of mesenchymal cell proliferation and the upregulation of periostin. Therefore, targeting stromal Shh could affect the equilibrium of the tumour microenvironment and its contribution to tumour growth.

Suppressed Helicobacter pylori-associated gastric tumorigenesis in Fat-1 transgenic mice producing endogenous ω-3 polyunsaturated fatty acids

Dietary approaches to preventing Helicobacter pylori (H. pylori)-associated gastric carcinogenesis are widely accepted because surrounding break-up mechanisms are mandatory for cancer prevention, however, eradication alone has been proven to be insufficient. Among these dietary interventions, omega-3-polyunsaturated-fatty acids (ω-3 PUFAs) are often the first candidate selected. However, there was no trial of fatty acids in preventing H. pylori-associated carcinogenesis and inconclusive results have been reported, likely based on inconsistent dietary administration. In this study, we developed an H. pylori initiated-, high salt diet promoted-gastric tumorigenesis model and conducted a comparison between wild-type (WT) and Fat-1-transgenic (TG)-mice. Gross and pathological lesions in mouse stomachs were evaluated at 16, 24, 32, and 45 weeks after H. pylori infection, and the underlying molecular changes to explain the cancer preventive effects were investigated. Significant changes in: i) ameliorated gastric inflammations at 16 weeks of H. pylori infection, ii) decreased angiogenic growth factors at 24 weeks, iii) attenuated atrophic gastritis and tumorigenesis at 32 weeks, and iv) decreased gastric cancer at 45 weeks were all noted in Fat-1-TG-mice compared to WT-mice. While an increase in the expression of Cyclooxygenase (COX)-2, and reduced expression of the tumor suppressive 15-PGDH were observed in WT-mice throughout the experimental periods, the expression of Hydroxyprostaglandin dehydrogenase (15-PGDH) was preserved in Fat-1-TG-mice. Using a comparative protein array, attenuated expressions of proteins implicated in proliferation and inflammation were observed in Fat-1-TG-mice compared to WT-mice. Conclusively, long-term administration of ω-3 PUFAs can suppress H. pylori-induced gastric tumorigenesis through a dampening of inflammation and reduced proliferation in accordance with afforded rejuvenation.

From inflammation to gastric cancer - the importance of Hedgehog/GLI signaling in Helicobacter pylori-induced chronic inflammatory and neoplastic diseases

Infections with the human pathogen Helicobacter pylori (H. pylori) are closely associated with the development of inflammatory disorders and neoplastic transformation of the gastric epithelium. Drastic changes in the micromilieu involve a complex network of H. pylori-regulated signal transduction pathways leading to the release of proinflammatory cytokines, gut hormones and a wide range of signaling molecules. Besides controlling embryonic development, the Hedgehog/GLI signaling pathway also plays important roles in epithelial proliferation, differentiation, and regeneration of the gastric physiology, but also in the induction and progression of inflammation and neoplastic transformation in H. pylori infections. Here, we summarize recent findings of H. pylori-associated Hedgehog/GLI signaling in gastric homeostasis, malignant development and the modulation of the gastric tumor microenvironment.

Hedgehog-Gli1 signaling regelates differentiation of chicken (Gallus gallus) embryonic stem cells to male germ cells

Gli1 is an important signaling molecular in Hedgehog signaling pathway. In our study, we explored the adjustment effect of Hedgehog-Gli1 signaling pathway on chicken male germ cells differentiation based on the transcriptome-wide analyses of chicken ESCs, primordial germ cells (PGCs) and spermatogonia stem cells (SSCs) that were associated with male germ cell differentiation. We screened out Hedgehog signaling pathway and identified 8 candidated differentially expressed genes (DEGs), Wnt3a, Wnt16, Wnt8a, HHIPL1, Gli1, BMP6, BMP7 and TTLL4. These DEGs expression change trend among blastoderm, genital ridge and testes, from which ESCs, PGCs and SSCs were isolated was the same as RNA-Seq data with quantitative RT-PCR evaluation. Based on retinoic acid (RA) induction of ESCs to SSCs in vitro, Gli1 overexpression has the ability to induce ESCs differentiation and SSCs-like cells formation and high expression of related reproductive genes, like Cvh, C-kit, Blamp1, Prmd14, Stra8, Dazl, integrin α6 and integrin β1 and so on in vitro. While RNAi knockdown of Gli1 can protect ESCs from differentiating into SSCs and correspondingly reduce the expression of the associated reproductive gene in vivo and vitro. Immunochemistry results showed that Gli1 overexpression could increase the expression of PGCs markers Cvh and C-kit and SSCs markers integrin α6 and integrin β1 in vivo, while Gli1 knockdown can have the opposite effect in vivo and in vitro. PAS stain and flow cytometry (FCM) evaluation results indicated the quantity of germ cells is decrease or increase with Gli1 knockdown or overexpression. Collectively, these results uncovered a novel function of Gli1 and demonstrated Hedgehog-Gli1 signaling pathway involved in chicken male germ cell differentiation, where it acts as a facilitator.

Hedgehog signaling in the stomach

The Hedgehog (Hh) signaling pathway not only plays a key part in controlling embryonic development, but in the adult stomach governs important cellular events such as epithelial cell differentiation, proliferation, gastric disease, and regeneration. In particular, Sonic Hedgehog (Shh) signaling has been well studied for its role in gastric physiology and pathophysiology. Shh is secreted from the gastric parietal cells and contributes to the regeneration of the epithelium in response to injury, or the development of gastritis during Helicobacter pylori infection. Dysregulation of the Shh signaling pathway leads to the disruption of gastric differentiation, loss of gastric acid secretion and the development of cancer. In this chapter, we will review the most recent findings that reveal the role of Shh as a regulator of gastric physiology, regeneration, and disease.

Role of Helicobacter pylori infection in generation of gastric cancer stem cells

Helicobacter pylori (H. pylori) is a key cause of gastric cancer, and gastric cancer stem cells play an important role in the development of gastric cancer. Therefore in this paper, we try to explore the relationship between H. pylori infection and stem cells in gastric cancer. H. pylori infection promotes the generation of gastric cancer stem cells through the epithelial-mesenchymal transition (EMT). In addition, H. pylori participates in the processes of the formation and progression of gastric cancer stem cells by affecting related signal pathways, such as Wnt/β-catenin, Hh/SHH, Notch, FGF/BMP. On this basis, we disscuss the challenges and future directions in the research of H. pylori infection and gastric cancer stem cells.

Methylation Microarray Studies Highlight PDGFA Expression as a Factor in Biliary Atresia

Biliary atresia (BA) is a progressive fibro-inflammatory disorder that is the leading indication for liver transplantation in children. Although there is evidence implicating genetic, infectious, environmental, and inflammatory causes, the etiology of BA remains unknown. We have recently reported that cholangiocytes from BA patients showed decreased DNA methylation relative to disease- and non-disease controls, supporting a potential role for DNA hypomethylation in BA etiopathogenesis. In the current study, we examined the methylation status of specific genes in human BA livers using methylation microarray technology. We found global DNA hypomethylation in BA samples as compared to disease- and non-disease controls at specific genetic loci. Hedgehog pathway members, SHH and GLI2, known to be upregulated in BA, were both hypomethylated, validating this approach as an investigative tool. Another region near the PDGFA locus was the most significantly hypomethylated in BA, suggesting potential aberrant expression. Validation assays confirmed increased transcriptional and protein expression of PDGFA in BA livers. We also show that PDGF-A protein is specifically localized to cholangiocytes in human liver samples. Injection of PDGF-AA protein dimer into zebrafish larvae caused biliary developmental and functional defects. In addition, activation of the Hedgehog pathway caused increased expression of PDGF-A in zebrafish larvae, providing a previously unrecognized link between PDGF and the Hedgehog pathway. Our findings implicate DNA hypomethylation as a specific factor in mediating overexpression of genes associated with BA and identify PDGF as a new candidate in BA pathogenesis.

Recapitulating Human Gastric Cancer Pathogenesis: Experimental Models of Gastric Cancer

This review focuses on the various experimental models to study gastric cancer pathogenesis, with the role of genetically engineered mouse models (GEMMs) used as the major examples. We review differences in human stomach anatomy compared to the stomachs of the experimental models, including the mouse and invertebrate models such as Drosophila and C. elegans. The contribution of major signaling pathways, e.g., Notch, Hedgehog, AKT/PI3K is discussed in the context of their potential contribution to foregut tumorigenesis. We critically examine the rationale behind specific GEMMs, chemical carcinogens, dietary promoters, Helicobacter infection, and direct mutagenesis of relevant oncogenes and tumor suppressor that have been developed to study gastric cancer pathogenesis. Despite species differences, more efficient and effective models to test specific genes and pathways disrupted in human gastric carcinogenesis have yet to emerge. As we better understand these species differences, "humanized" versions of mouse models will more closely approximate human gastric cancer pathogenesis. Towards that end, epigenetic marks on chromatin, the gut microbiota, and ways of manipulating the immune system will likely move center stage, permitting greater overlap between rodent and human cancer phenotypes thus providing a unified progression model.

Patho-epigenetics of Infectious Diseases Caused by Intracellular Bacteria

In multicellular eukaryotes including plants, animals and humans, epigenetic reprogramming may play a role in the pathogenesis of a wide variety of diseases. Recent studies revealed that in addition to viruses, pathogenic bacteria are also capable to dysregulate the epigenetic machinery of their target cells. In this chapter we focus on epigenetic alterations induced by bacteria infecting humans. Most of them are obligate or facultative intracellular bacteria that produce either bacterial toxins and surface proteins targeting the host cell membrane, or synthesise effector proteins entering the host cell nucleus. These bacterial products typically elicit histone modifications, i.e. alter the "histone code". Bacterial pathogens are capable to induce alterations of host cell DNA methylation patterns, too. Such changes in the host cell epigenotype and gene expression pattern may hinder the antibacterial immune response and create favourable conditions for bacterial colonization, growth, or spread. Epigenetic dysregulation mediated by bacterial products may also facilitate the production of inflammatory cytokines and other inflammatory mediators affecting the epigenotype of their target cells. Such indirect epigenetic changes as well as direct interference with the epigenetic machinery of the host cells may contribute to the initiation and progression of malignant tumors associated with distinct bacterial infections.

A cancer theory kerfuffle can lead to new lines of research

The standard viewpoint that cancer is a genetic disease is often stated as a fact rather than a theory. By not acknowledging that it is a theory, namely the Somatic Mutation Theory (SMT), researchers are limiting their progress. An attractive alternative to SMT is the tissue organization field theory (TOFT), which is summarized as "development gone awry." To initiate a kerfuffle, I discuss the interpretation of various results under both TOFT and SMT, including recurrent mutations, hereditary cancers, induction of tumors in transgenic experiments, remission of tumors following the inhibition of enzymes activated by mutated genes, nongenotoxic carcinogens, denervation experiments, foreign-body carcinogenesis, transplantation experiments, and tumors with zero mutations. Thinking in terms of TOFT can spur new lines of research; examples are given related to the early detection of cancer.

Mesenchymal stem cells induce epithelial proliferation within the inflamed stomach

Bone marrow-derived mesenchymal stem cells (MSCs) sustain cancer cells by creating a microenvironment favorable for tumor growth. In particular, MSCs have been implicated in gastric cancer development. There is extensive evidence suggesting that Hedgehog signaling regulates tumor growth. However, very little is known regarding the precise roles of Hedgehog signaling and MSCs in tumor development within the stomach. The current study tests that hypothesis that Sonic Hedgehog (Shh), secreted from MSCs, provides a proliferative stimulus for the gastric epithelium in the presence of inflammation. Red fluorescent protein-expressing MSCs transformed in vitro (stMSCs) were transduced with lentiviral constructs containing a vector control (stMSC(vect)) or short hairpin RNA (shRNA) targeting the Shh gene (stMSC(ShhKO)). Gastric submucosal transplantation of wild-type MSCs (wtMSCs), wild-type MSCs overexpressing Shh (wtMSC(Shh)), stMSC(vect), or stMSC(ShhKO) cells in C57BL/6 control (BL/6) or gastrin-deficient (GKO) mice was performed and mice analyzed 30 and 60 days posttransplantation. Compared with BL/6 mice transplanted with wtMSC(Shh) and stMSC(vect) cells, inflamed GKO mice developed aggressive gastric tumors. Tumor development was not observed in mouse stomachs transplanted with wtMSC or stMSC(ShhKO) cells. Compared with stMSC(ShhKO)-transplanted mice, within the inflamed GKO mouse stomach, Shh-expressing stMSC(vect)- and wtMSC(Shh)-induced proliferation of CD44-positive cells. CD44-positive cells clustered in gland-like structures within the tumor stroma and were positive for Patched (Ptch) expression. We conclude that Shh, secreted from MSCs, provides a proliferative stimulus for the gastric epithelium that is associated with tumor development, a response that is sustained by chronic inflammation.

Cancer stem cell-related signaling pathways in development of gastric cancer

Cancer stem cells are a subset of cancer cells with self-renewal and differentiation capacity. They play an important role in gastric carcinogenesis, proliferation, migration, invasion and metastasis and are involved in resistance to chemotherapy. Numerous studies indicate that stem cell-related signaling pathways (such as Wnt, Notch, Hedgehog, PI3K, and BMP) are activated in the occurrence and development of gastric cancer. Inhibition of tumor self-renewal-related signaling pathways can significantly improve the prognosis of patients with gastric cancer. In this paper we will review the roles of these cancer stem cell-related signaling pathways in gastric cancer.