Association between endogenous gene expression and growth regulation induced by TGF-β1 in human gastric cancer cells

GLIS3, a novel prognostic indicator of gastric adenocarcinoma, contributes to the malignant biological behaviors of tumor cells via modulating TGF-β1/TGFβR1/Smad1/5 signaling pathway

GLIS3 is highly expressed in multiple cancers, but it has not been studied in gastric adenocarcinoma (GAC). Based on bioinformatics analysis, the prognostic significance of GLIS3 in GAC was analyzed. GAC cells were transfected with small interfering (si)-GLIS3 and GLIS3 overexpression plasmid as well as treated with SB505124 [an inhibitor for transforming growth factor beta receptor 1 (TGFβR1)] and dorsomorphin [an inhibitor for bone morphogenetic protein receptor 1 (BMPR1)]. The GLIS3 expression was detected using qRT-PCR. The impacts of GLIS3 on the proliferation, invasion and migration of GAC cells were measured using cell function assays. The activation of phosphor (p)-Smad1/5 was tested by immunofluorescence. Western blot was utilized to measure the level of transforming growth factor (TGF)-β1/Smad1/5 signaling pathway-related proteins (TGF-β1, p-Smad1, Smad1, p-Smad5, Smad5). GLIS3 was expressed at high levels in GAC tissues and cell lines and its high expression could indicate the poor prognosis of GAC patients. GLIS3 inhibition declined the proliferative, invasive and migratory capabilities as well as TGF-β1 expression and phosphorylation of Smad1/5 in GAC cells. Overexpressed GLIS3 promoted proliferation, migration, invasion, TGF-β1 expression and Smad1/5 phosphorylation in GAC cells, with SB505124 reversing the effects of overexpressed GLIS3 on proliferation, migration, invasion and Smad1/5 phosphorylation whereas dorsomorphin exhibiting no influence on GLIS3-induced effects. GLIS3 facilitated the malignant phenotype of GAC cells via regulating TGF-β1/TGFβR1/Smad1/5 pathway, which may be a novel prognostic indicator of GAC and provided a target for GAC treatment.

TGFβ-Associated Signature Predicts Prognosis and Tumor Microenvironment Infiltration Characterization in Gastric Carcinoma

Background: Gastric carcinoma (GC) is a carcinoma with a high incidence rate, and it is a deadly carcinoma globally. An effective tool, that is, able to predict different survival outcomes for GC patients receiving individualized treatments is deeply needed.

Methods: In total, data from 975 GC patients were collected from TCGA-STAD, GSE15459, and GSE84437. Then, we performed a comprehensive unsupervised clustering analysis based on 54 TGFβ-pathway-related genes and correlated these patterns with tumor microenvironment (TME) cell-infiltrating characteristics. WGCNA was then applied to find the module that had the closest relation with these patterns. The least absolute shrinkage and selection operator (LASSO) algorithm was combined with cross validation to narrow down variables and random survival forest (RSF) was used to create a risk score.

Results: We identified two different TGFβ regulation patterns and named them as TGFβ Cluster 1 and Cluster 2. TGFβ Cluster 1 was linked to significantly poorer survival outcomes and represented an inflamed TME subtype of GC. Using WGCNA, a module (magenta) with the closest association with the TGFβ clusters was identified. After narrowing down the gene list by univariate Cox regression analysis, the LASSO algorithm and cross validation, four of the 243 genes in the magenta module were applied to build a risk score. The group with a higher risk score exhibited a considerably poorer survival outcome with high predictive accuracy. The risk score remained an independent risk factor in multivariate Cox analysis. Moreover, we validated this risk score using GSE15459 and GSE84437. Furthermore, we found that the group with a higher risk score represented an inflamed TME according to the evidence that the risk score was remarkably correlated with several steps of cancer immunity cycles and a majority of the infiltrating immune cells. Consistently, the risk score was significantly related to immune checkpoint genes and T cell–inflamed gene expression profiles (GEPs), indicating the value of predicting immunotherapy.

Conclusions: We have developed and validated a TGFβ-associated signature, that is, capable of predicting the survival outcome as well as depicting the TME immune characteristics of GC. In summary, this signature may contribute to precision medicine for GC.

The role of transforming growth factor β in upper gastrointestinal cancers: A systematic review

Esophageal and gastric malignancies are associated with poor prognosis, in part due to development of recurrences or metastases after curative treatment. The transforming growth factor β (TGF-β) pathway might play a role in the development of treatment resistance. In this systematic review, we provide an overview of preclinical studies investigating the role of TGF-β in esophageal and gastric malignancies. We systematically searched MEDLINE/PubMed and EMBASE for eligible preclinical studies describing the effect of TGF-β or TGF-β inhibition on hallmarks of cancer, such as proliferation, migration, invasion, angiogenesis and immune evasion. In total, 2107 records were screened and 45 articles were included, using mouse models and 45 different cell lines. TGF-β failed to induce apoptosis in twelve of sixteen tested cell lines. TGF-β could either decrease (five cell lines) or increase proliferation (seven cell lines) in gastric cancer cells, but had no effect in esophageal cancer cells. In all esophageal and all but two gastric cancer cell lines, TGF-β increased migratory, adhesive and invasive capacities. In vivo studies showed increased metastasis in response to TGF-β treatment. Additionally, TGF-β was shown to induce vascular endothelial growth factor production and differentiation of cancer-associated fibroblasts and regulatory T-cells. In conclusion, we found that TGF-β enhances hallmarks of cancer in most gastric and esophageal cancer cell lines, but not in all. Therefore, targeting the TGF-β pathway could be an attractive strategy in patients with gastric or esophageal cancer, but additional clinical trials are needed to define patient groups who would benefit most.

KLF8 involves in TGF-beta-induced EMT and promotes invasion and migration in gastric cancer cells

PURPOSE

Krüppel-like factor 8 (KLF8), a downstream transcription factor of transforming growth factor-β1 (TGF-β1), has a role in tumorigenesis, tumor progress and epithelial-to-mesenchymal transition (EMT) induction. Recent studies mainly focused on its role in breast cancer and hepatocellular carcinoma; however, little is studied in gastric cancer. Here, we aim to explore whether KLF8 is involved in TGF-β1-induced EMT in gastric cancer cells.

METHODS

Western blot and real-time PCR assays were used to detect the expression of KLF8, E-cadherin and vimentin in gastric cancer cell line SGC7901 treated with or without TGF-β1. The lentivirus-mediated RNA interference technique was used to knock down the expression of KLF8 in gastric cancer cell line SGC7901. In vitro, the ability of cell migration and invasion were measured by transwell and wound healing assays; the cell motility was detected by high content screening assay.

RESULTS

TGF-β1 could induce EMT via down-regulating E-cadherin and up-regulating vimentin expression in gastric cancer cells. Further study found that TGF-β1 could induce KLF8 expression at the protein and mRNA levels in gastric cancer cells (P < 0.05). Western blot and real-time PCR assays found that small interference RNA (siRNA)-mediated KLF8 silence blocked TGF-β1-induced EMT-like transformation and subsequently reversed the loss of E-cadherin and gain of vimentin. In vitro, inhibition of KLF8 decreased TGF-β1-prompted cell migration, invasion and motility.

CONCLUSIONS

KLF8, a transcription factor, is involved in TGF-β1-induced EMT in gastric cancer cells and may be a novel therapeutic target for the treatment of gastric cancer.

TGF-β1 alters microRNA profile in human gastric cancer cells

OBJECTIVE

MicroRNAs (miRNAs) are important regulators that play a key role in tumorigenesis and tumor progression. Transforming growth factor-β1 (TGF-β1) is involved in invasion and metastasis in many tumors. In this study, we investigated the microRNAs (miRNA) profiles altered by TGF-β1 in gastric cancer (GC) cells.

METHODS

We detected the expression profiles of miRNA by miRNA microarray and quantitative real-time polymerase chain reaction. Migration and invasion, wound-healing assay, prediction of miRNA targets, Western blot and qRT-PCR analysis were carried out to determine the role of one selected miRNA, namely miR-193b, in affecting the biological behaviors of GC BGC823 cells.

RESULTS

Among 847 human miRNAs in the microarray, three miRNAs (miR-27a, miR-29b-1 and miR-194) were up-regulated and three (miR-574-3p, miR-193b and miR-130b) were down-regulated in BGC823 cells treated with TGF-β1 compared with control. miR-193b suppressed the invasion and metastasis of GC cells in vivo and in vitro, and down-regulated urokinase-type plasminogen activator (uPA) protein in GC cells.

CONCLUSIONS

TGF-β1 altered miRNA expression profile in BGC823 cells. Among the altered miRNAs, TGF-β1 induced the down-regulation of miR-193b, which inhibited cell invasion and metastasis in vivo and in vitro, and down-regulated uPA protein in GC cells.

Involvement of KLF14 and egr-1 in the TGF-beta1 action on Leydig cell proliferation

Transforming growth factor β1 (TGF-β1) is a pleiotropic cytokine that modulates cell homeostasis. In Leydig cells, TGF-β1 exerts stimulatory and inhibitory effect depending on the type I receptor involved in the signaling pathway. The aim of the present work was to study the signaling mechanisms and the intermediates involved in the action of TGF-β1 on TM3 Leydig cell proliferation in the presence or absence of progesterone. The MTT assay showed that the presence of progesterone in the culture media lead to a proliferative effect that was blocked by Ru 486, an inhibitor of progesterone receptor; and ALK-5 did not participate in this effect. TGF-β1 (1 ng/ml) increased the expression of p15 (an inhibitor of cell cycle) in TM3 Leydig cells, and this effect was blocked by progesterone (1μM). The expression of PCNA presented a higher increase in the cell cultured with TGF-β1 plus progesterone than in cells cultured only with TGF-β1. Progesterone induced the gene expression of endoglin, a cofactor of TGF-β1 receptor that leads to a stimulatory signaling pathway, despite of the absence of progesterone response element in endoglin gene. In addition, the presence of progesterone induced the gene expression of egr-1 and also KLF14, indicating that this steroid channels the signaling pathway into a non-canonical mechanism. In conclusion, these findings suggest that the proliferative action of TGF-β1 involves endoglin. This co-receptor might be induced by KLF14 which is probably activated by progesterone.

FGFR4 and TGF-β1 expression in hepatocellular carcinoma: correlation with clinicopathological features and prognosis

OBJECTIVE

To investigate the expression and correlation of transforming growth factor-β1 (TGF-β1) and fibroblast growth factor receptor 4 (FGFR4) in human hepatocellular carcinoma (HCC) and the relationship with clinicopathological features and prognosis.

MATERIALS AND METHODS

The expression of TGF-β1 and FGFR4 in 126 HCC samples was detected immunohistochemically. Combined with clinical postoperative follow-up data, the expression of TGF-β1 and FGFR4 in HCC and the relationship with the prognosis of patients were analyzed by statistically.

RESULTS

The positive expression rate of TGF-β1 was 84.1% (106/126) in tumors, and that in peritumoral liver tissues was 64.3% (81/126); the positive expression rate of FGFR4 in tumors was 74.6% (94/126) and that in peritumoral liver tissues was 57.1% (72/126). The expression of TGF-β1 and FGFR4 in the carcinoma tissues was significantly higher than that in peritumoral liver tissues (p < 0.05). Intratumoral TGF-β1 and FGFR4 expression was associated with TNM stage (p < 0.05). TGF-β1 and FGFR4 expression levels didn't significantly correlate with other clinicopathological parameters, including age, sex, tumor size, serum AFP level, tumor differentiation, lymph node metastasis, etc. (p > 0.05). TGF-β1 expression was positively correlated with FGFR4 expression (r = 0.595, p < 0.05). Patients with positive FGFR4 or TGF-β1 expression had shorter overall survival compared with negative expression (p < 0.05).

CONCLUSIONS

The expression of TGF-β1 and FGFR4 could make synergy on the occurrence and progression of HCC, and may be used as prognosis indicators for HCC patients.

Influence of the photoperiod on TGF-β1 and p15 expression in hamster Leydig cells

Adult hamsters exposed to short photoperiods show a marked atrophy of their internal reproductive organs, including a reduction in size, though not number of Leydig cells. Transforming growth factor-β1 (TGF-β1) is involved in the regulation of growth and proliferation of different cell types. The aim of the present study was to examine the influence of photoperiod on the protein and gene expression of TGF-β1 and its receptors as well as gene expression of p15. The effect of TGF-β1 on the expression of p15 in purified Leydig cells from regressed and non-regressed hamster testes was also tested. Protein and gene expression of TGF-β1 was detected in both regressed and non-regressed testes. In contrast to the activin receptor-like kinase 1 (ALK-1), the TGF-β1, the activin receptor-like kinase 5 (ALK-5) and the co-receptor endoglin all showed a greater basal expression in regressed than non-regressed hamster testes. Melatonin induced the TGF-β1 mRNA expression in purified Leydig cells from non-regressed testes. The p15 mRNA level was greater in regressed than non-regressed testes. A high dose of TGF-β1 during a short incubation period increased the p15 mRNA level in Leydig cells from non-regressed testes. ALK-5 and mitogen-activated protein kinase (MAPK) p38 might have played a role in this process. In regressed hamster testes, the p15 mRNA level increased due to a low dose of TGF-β1 after short incubation periods and to a high dose after longer incubation periods; in both instances, ALK-5, ERK 1/2 and p38 were involved. Collectively, these results suggest that the alterations in p15 expression, mediated by MAPK, are involved in the shift between the active and inactive states in hamster Leydig cells.

Lipid Peroxidation and Transforming Growth Factor-β1 Levels in Gastric Cancer at Pathologic Stages

OBJECTIVE

High levels of TGF-β1 and enhanced TGF-β1 receptor signaling are related to the pathology of gastric cancer. This effect is caused by oxidative stress and lipid peroxidation products. The aim of this study was to investigate the levels of TGF-β1 and lipid peroxidation products in gastric cancer patients and their correlation with pathologic stage.

MATERIAL AND METHODS

Lipid peroxidation products and TGF-β1 levels were studied in the serum samples of 50 gastric cancer patients and 18 control subjects.

RESULTS

HNE-protein adducts and TGF-β1 levels were significantly higher in T2, T3 and T4 gastric cancers than in either the T1 stage or controls (p<0.001). Pathologic stage was correlated with TGF-β1 levels (r=0.702, p<0.05).

CONCLUSION

These markers production may contribute to tumor angiogenesis and aid in the prognosis of the gastric cancer.

A novel mouse model of gastric cancer with human gastric microenvironment

Mouse models play an irreplaceable role in the in vivo research of human gastric cancer. In this study, we developed a novel human Gastric tissue-derived Orthotopic and Metastatic (GOM) mouse model of human gastric cancer, in which the human normal gastric tissues were implanted subcutaneously into immunodeficient mice to create a human gastric microenvironment. Then, human gastric cancer cells were injected into the implants. GOM model could mimic the interactions between human gastric microenvironment and human gastric cancer cells, which help exhibit the real characteristics of tumor cells, and finally mimic the clinical-like tumor proliferation and metastases of human beings.

Genetic Mechanisms and Aberrant Gene Expression during the Development of Gastric Intestinal Metaplasia and Adenocarcinoma

Gastric adenocarcinoma occurs via a sequence of molecular events known as the Correa’s Cascade which often progresses over many years. Gastritis, typically caused by infection with the bacterium H. pylori, is the first step of the cascade that results in gastric cancer; however, not all cases of gastritis progress along this carcinogenic route. Despite recent antibiotic intervention of H. pylori infections, gastric adenocarcinoma remains the second most common cause of cancer deaths worldwide. Intestinal metaplasia is the next step along the carcinogenic sequence after gastritis and is considered to be a precursor lesion for gastric cancer; however, not all patients with intestinal metaplasia develop adenocarcinoma and little is known about the molecular and genetic events that trigger the progression of intestinal metaplasia into adenocarcinoma. This review aims to highlight the progress to date in the genetic events involved in intestinal-type gastric adenocarcinoma and its precursor lesion, intestinal metaplasia. The use of technologies such as whole genome microarray analysis, immunohistochemical analysis and DNA methylation analysis has allowed an insight into some of the events which occur in intestinal metaplasia and may be involved in carcinogenesis. There is still much that is yet to be discovered surrounding the development of this lesion and how, in many cases, it develops into a state of malignancy.

Dermatopontin is expressed in human liver and is downregulated in hepatocellular carcinoma

Dermatopontin (DPT) was recently found as a downstream target of vitamin D receptor, which is a key molecule in the 1,25-dihydroxy-vitamin D(3) anti-hepatoma proliferation pathway. MCTx-1 from Millepora, a homolog of DPT, is identified as a cytotoxin towards leukemia cells. The aim of this study was to analyze DPT expression in hepatocellular carcinoma (HCC) based on the analysis for DPT gene in normal tissues in order to estimate its function in the progression of HCC. DPT mRNA expression was analyzed in normal tissues and HCC cell lines by RT-PCR, and in HCC tissue by RT-PCR and real-time PCR. Its protein was examined in HCC tissues by Western blot and immunohistochemistry assays. Meanwhile, transforming growth factor-beta1 (TGF-beta1) that is closely associated with HCC and DPT was observed by immunohistochemistry in HCC tissues. The results showed that DPT mRNA was strongly expressed in human fetal and adult liver, kidney, and spleen, weakly in ovary and heart, and absent in other tissues and HCC cell lines examined. Its mRNA was significantly downregulated in HCC tissues, while its protein was weakly expressed in tumor compared with non-tumor. DPT is located mainly in the cytoplasm of several cell types in the liver; it has been identified also in the extracellular matrix of the skin. TGF-beta1 was observed in extensive tumor tissue of HCC. This fact suggests that DPT can play various roles in different tissues and might be a molecule related to carcinogenesis and the progression of HCC via possible interaction with TGF-beta1 and other potential mechanisms.

Small bowel carcinoid (enterochromaffin cell) neoplasia exhibits transforming growth factor-beta1-mediated regulatory abnormalities including up-regulation of C-Myc and MTA1

BACKGROUND

Although it is known that small intestinal carcinoids are derived from enterochromaffin (EC) cells, these cells remain poorly characterized and little is known of the growth regulatory mechanisms of these neuroendocrine cells. Down-regulation or loss of the transforming growth factor-beta1 (TGFbeta1) cytostatic program and activation of TGFbeta-mediated transcriptional networks is associated with uncontrolled growth and metastasis in other neural tumors, glioblastomas. Whether this phenomenon is common to small intestinal carcinoid tumors was investigated.

METHODS

The effects of TGFbeta1 on cultured normal EC cells (isolated by FACS sorting) and the neoplastic EC cell line, KRJ-I, was assessed using the MTT assay. The TGFbetaRII transcript and protein were identified in tumor cells and the effects of TGFbeta1 on SMAD2 phosphorylation and nuclear translocation quantified. The time-dependent response of SMAD4, SMAD7, c-Myc, and P21(WAF1/CIP1) protein expression and c-Myc and p21(WAF1/CIP1) transcript was measured in response to TGFbeta1 and the transcript expression of candidate downstream targets, MTA1 and E-cadherin, were assessed.

RESULTS

TGFbeta1 inhibited normal EC cell proliferation (IC(50) = 17 pM) but stimulated neoplastic EC cell proliferation (EC(50) = 22 pM). In tumor cells, significantly decreased transcript (P < .01) of TGFbetaRII was identified, but no receptor mutations were identified and protein expression was evident. TGFbeta1 (1 ng/mL) resulted in SMAD2 phosphorylation and <7% nuclear expression compared with 93% in normal EC cells. In neoplastic cells, TGFbeta1 (1 ng/mL) caused a decrease in SMAD4 (>16%, P < .05), whereas SMAD7 and c-Myc transcript and protein were respectively increased >21% (P < .05) and approximately 40% (P < .002). TGFbeta1 (1 ng/mL) also decreased p21(WAF1/CIP1) transcript by 60% (P < .001) and protein that was undetectable at 24 hours. Expression of the downstream targets of the c-Myc pathway, MTA1, was increased (20%) and E-cadherin decreased (30%).

CONCLUSIONS

The neoplastic EC cell is characterized by loss of TGFbeta-1-mediated growth inhibition and, similar to glioblastomas, utilizes the TGFbeta system to induce gene responses associated with growth promotion (c-Myc and the ERK pathway), invasion (E-cadherin), and metastasis (MTA1).

GO-2D: identifying 2-dimensional cellular-localized functional modules in Gene Ontology

BACKGROUND

Rapid progress in high-throughput biotechnologies (e.g. microarrays) and exponential accumulation of gene functional knowledge make it promising for systematic understanding of complex human diseases at functional modules level. Based on Gene Ontology, a large number of automatic tools have been developed for the functional analysis and biological interpretation of the high-throughput microarray data.

RESULTS

Different from the existing tools such as Onto-Express and FatiGO, we develop a tool named GO-2D for identifying 2-dimensional functional modules based on combined GO categories. For example, it refines biological process categories by sorting their genes into different cellular component categories, and then extracts those combined categories enriched with the interesting genes (e.g., the differentially expressed genes) for identifying the cellular-localized functional modules. Applications of GO-2D to the analyses of two human cancer datasets show that very specific disease-relevant processes can be identified by using cellular location information.

CONCLUSION

For studying complex human diseases, GO-2D can extract functionally compact and detailed modules such as the cellular-localized ones, characterizing disease-relevant modules in terms of both biological processes and cellular locations. The application results clearly demonstrate that 2-dimensional approach complementary to current 1-dimensional approach is powerful for finding modules highly relevant to diseases.

Effect of transforming growth factor-β1 on human intrahepatic cholangiocarcinoma cell growth

AIM: To elucidate the biological effects of transforming growth factor-β1 (TGF-β1) on intrahepatic cholan-giocarcinoma (ICC).

METHODS: We investigated the effects of TGF-β1 on human ICC cell lines (HuCCT1, MEC, and HuH-28) by monitoring the influence of TGF-β1 on tumor growth and interleukin-6 (IL-6) expression in ICC cells.

RESULTS: All three human ICC cell lines produced TGF-β1 and demonstrated accelerated growth in the presence of TGF-β1 with no apoptotic effect. Studies on HuCCT1 revealed a TGF-β1-induced stimulation of the expression of TGF-β1, as well as a decrease in TGF-β1 mRNA expression induced by neutralizing anti-TGF-β1 antibody. These results indicate that TGF-β1 stimulates the production and function of TGF-β1 in an autocrine fashion. Further, IL-6 secretion was observed in all three cell lines and exhibited an inhibitory response to neutralizing anti-TGF-β1 antibody. Experiments using HuCCT1 revealed a TGF-β1-induced acceleration of IL-6 protein expression and mRNA levels. These findings demonstrate a functional interaction between TGF-β1 and IL-6. All three cell lines proliferated in the presence of IL-6. In contrast, TGF-β1 induced no growth effect in HuCCT1 in the presence of small interfering RNA against a specific cell surface receptor of IL-6 and signal transducer and activator of transcription-3.

CONCLUSION: ICC cells produce TGF-β1 and confer a TGF-β1-induced growth effect in an autocrine fashion. TGF-β1 activates IL-6 production, and the functional interaction between TGF-β1 and IL-6 contributes to ICC cell growth by TGF-β1.

Enhancement of metastatic and invasive capacity of gastric cancer cells by transforming growth factor-beta1

Transforming growth factor-beta (TGF-beta), a multifunctional cytokine, exerts contradictory roles in different kinds of cells. A number of studies have revealed its involvement in the progression of many types of tumors. To investigate the effect of TGF-beta on gastric carcinoma, SGC7901, BGC823 and MKN28 (a TGF-beta-resistant cell line) adenocarcinoma clones were used. After pretreatment in serum-free medium with or without 10 ng/ml TGF-beta1, their experimental metastatic potential, chemotaxis, and invasive and adhesive ability were measured. Furthermore, zymography for gelatinase was processed. Liver colonies were also measured 4 weeks after inoculation of SGC7901, BGC823 and MKN28 in Balb/c nude mice, and an increase in the number of surface liver metastases was seen in SGC7901 (from 11.0+/-3.0 to 53.3+/-3.3) and BGC823 (from 9.3+/-2.5 to 60.0+/-2.8) groups, whereas there was no difference between MKN28 groups (from 35.2+/-3.8 to 38.5+/-2.7). In vitro experiments showed that TGF-beta1 increased the adhesion capacity of SGC7901 and BGC823 cells to immobilized reconstituted basement membrane/fibronectin matrices and promoted their penetration through reconstituted basement membrane barriers. Zymography demonstrated that enhanced invasive potential was partly due to the increased type IV collagenolytic (gelatinolytic) activity, but there was no difference in type IV collagenolytic activity and other biological behaviors between MKN28 groups. These results suggested that TGF-beta1 might modulate the metastatic potential of gastric cancer cells by promoting their ability to break down and penetrate basement membrane barriers and their adhesive and motile activities. We speculated that TGF-beta1 might act as a progression-enhancing factor in gastric cancer. Therefore blockage of TGF-beta or TGF-beta signaling might prevent gastric cancer cells from invading and metastasizing.