Signaling Pathway In Gastric Cancer Research Articles

MiR-1236-3p inhibits invasion and metastasis in gastric cancer by targeting MTA2

BackgroundMicroRNAs deregulation are common in human tumor progression. miR-1236-3p has been reported to function as tumor suppressor microRNA in various malignancies. The aim of this study was to demonstrate the downregulated expression of miR-1236-3p in gastric cancer (GC) tissues and cell lines, and clarify its biological function in GC.MethodsReal-time polymerase chain reaction was used to measure the mRNA level of miR-1236-3p in GC. Dual luciferase assay was used to demonstrate that MTA2 was one of the candidate target genes of miR-1236-3p. Western blots were utilized to detect the protein levels. Cell function assays were also performed to determine the function of miR-1236-3p in GC.ResultsmiR-1236-3p expression, which was associated with lymph node metastasis, differentiation and clinical stage, was significantly reduced in GC tissues and cell lines. miR-1236-3p over-expression could inhibit GC cell proliferation, migration and invasion, and inhibition of miR-1236-3p expression had opposite effects. Furthermore, we demonstrated that MTA2 was a candidate target of miR-1236-3p, and miR-1236-3p over-expression significantly inhibited the process of epithelial–mesenchymal transition. We also found that miR-1236-3p could suppress the PI3K/Akt signaling pathway in GC cells.ConclusionsOur results suggest that miR-1236-3p functions as a tumor suppressor in GC and could be a promising therapeutic target for GC.

CXCL9/10/11, a regulator of PD-L1 expression in gastric cancer

BackgroundProgrammed death-ligand 1 (PD-L1) is an immunosuppressor that plays an important role in cancer treatments. Although majority of the studies demonstrated that PD-L1 expression was regulated by cellular intrinsic and extrinsic controls, and IFN-γ was a key molecule of extrinsic control, other studies imply that other cytokines play important roles in PD-L1 expression. In this study, we investigated the regulation of PD-L1 by chemokine signaling pathway in gastric cancer (GC) cells.MethodsBioinformatics was used to explore the PD-L1-related genes in GC and propose a hypothesis. PD-L1 and CXCR3 expression were detected by western blot in SGC7901 and MKN74 cell lines. Meanwhile, PD-L1 and CXCR3 expressions were immunohistochemically assessed for their relevance. Moreover, PD-L1, pSTAT3 and pAkt were detected after treatment with CXCL9/10/11. Furthermore,PD-L1, pSTAT3 and pAkt were evaluated after blocking chemokine signaling in SGC7901 cells.ResultsBased on online database analysis, CXCL9/10/11-CXCR3 is proposed to upregulate PD-L1 expression by activating the STAT and PI3K-Akt pathways. This hypothesis was confirmed by in vitro and vivo experiments. CXCR3 and PD-L1 were expressed in GC cell lines and tissues, and the expression of CXCR3 and PD-L1 was positively related. PD-L1 was upregulated after treatment with CXCL9/10/11, accompanied by activation of STAT3 and Akt. After blocking chemokine signaling, upregulation of PD-L1 and activation of STAT3 and Akt were diminished.ConclusionsCXCL9/10/11-CXCR3 upregulated the expression of PD-L1 by activating the STAT and PI3K-Akt signaling pathways in GC cells. There was a significant positive correlation between the expression of PD-L1 and CXCR3 in gastric cancer patient tissues.

RUNX1 positively regulates the ErbB2/HER2 signaling pathway through modulating SOS1 expression in gastric cancer cells

The dual function of runt-related transcriptional factor 1 (RUNX1) as an oncogene or oncosuppressor has been extensively studied in various malignancies, yet its role in gastric cancer remains elusive. Up-regulation of the ErbB2/HER2 signaling pathway is frequently-encountered in gastric cancer and contributes to the maintenance of these cancer cells. This signaling cascade is partly mediated by son of sevenless homolog (SOS) family, which function as adaptor proteins in the RTK cascades. Herein we report that RUNX1 regulates the ErbB2/HER2 signaling pathway in gastric cancer cells through transactivating SOS1 expression, rendering itself an ideal target in anti-tumor strategy toward this cancer. Mechanistically, RUNX1 interacts with the RUNX1 binding DNA sequence located in SOS1 promoter and positively regulates it. Knockdown of RUNX1 led to the decreased expression of SOS1 as well as dephosphorylation of ErbB2/HER2, subsequently suppressed the proliferation of gastric cancer cells. We also found that our novel RUNX inhibitor (Chb-M’) consistently led to the deactivation of the ErbB2/HER2 signaling pathway and was effective against several gastric cancer cell lines. Taken together, our work identified a novel interaction of RUNX1 and the ErbB2/HER2 signaling pathway in gastric cancer, which can potentially be exploited in the management of this malignancy.

NES1/KLK10 promotes trastuzumab resistance via activation of PI3K/AKT signaling pathway in gastric cancer.

Trastuzumab, a humanized antibody targeting human epidermal growth factor receptor 2 (HER2), exhibits remarkable therapeutic efficacy against HER2-positive gastric cancer. Acquired resistance to trastuzumab remains a barrier to patient survival and the mechanisms underlying this are still not well understood. The normal epithelial cell-specific-1 (NES1) gene, also named as KLK10, is recognized as a potential therapeutic target for reversing trastuzumab resistance. The aim of this study was to explore the potential role of KLK10 in trastuzumab resistance (TR) gastric cancer cells. We found that KLK10 was significantly upregulated in trastuzumab-resistant cell lines, SGC7901-TR and BGC-823-TR. In addition, down regulation of KLK10 reversed the resistance in trastuzumab resistant cells. Overexpression of KLK10 induced trastuzumab resistance, and activated the PI3K/AKT signaling pathway, while downregulation of KLK10 presented the opposite effects. Moreover, when the PI3K/AKT signaling pathway was inhibited, the effect of KLK10 on resistance was diminished. Furthermore, combination of trastuzumab and PI3K/AKT inhibitor XL147 effectively inhibited tumor growth in KLK10-overexpressing xenografts. Taken together, our findings show that KLK10 promotes trastuzumab resistance, at least in part, through the PI3K/AKT signaling pathway, suggesting that KLK10 is a potentially target to overcome trastuzumab resistance, and the combination might overcome trastuzumab resistance in KLK10-overexpressed gastric cancer patients.

Corrigendum] RLIP76 increases apoptosis through Akt/mTOR signaling pathway in gastric cancer.

Following the publication of this article, we realize that the title appeared incorrectly: This appeared in print as 'RLIP76 increases apoptosis through Akt/mTOR signaling pathway in gastric cancer', and the corrected title is now featured above ('increases' should have read as 'decreases'). Note that this error did not have any bearing on the results reported in the paper (which were reported accurately in terms of the influence of RLIP76 on apoptosis of human gastric cancer SGC‑7901 and MGC‑803cells), or the conclusions therein. We regret any inconvenience that this mistake has caused. [the original article was published in the Oncology Reports 36: 2216-2224, 2016; DOI: 10.3892/or.2016.5043].

CDK5RAP3 suppresses Wnt/\u03b2-catenin signaling by inhibiting AKT phosphorylation in gastric cancer

BackgroundCDK5RAP3 was initially isolated as a binding protein of the CDK5 activator p35. Although CDK5RAP3 has been shown to negatively regulate the Wnt/β-catenin signaling pathway in gastric cancer by repressing GSK-3β phosphorylation, its in-depth mechanism has not been determined.MethodsFollowing CDK5RAP3 overexpression or knock down, CDK5RAP3 signaling pathways were investigated in gastric cancer cells by Western Blotting. Cell growth, invasion and migration were also evaluated in gastric cancer cell lines. We analyzed CDK5RAP3, AKT, p-AKT (Ser473), GSK-3β and p-GSK-3β (Ser9) expression in gastric tumor samples and adjacent non-tumor tissues from 295 patients using immunohistochemistry and Western Blotting. The prognostic significance of CDK5RAP3 and p-AKT (Ser473) was confirmed by a Log-rank test.ResultsOur study demonstrated that the expression of p-AKT (Ser473) and p-GSK-3β (Ser9) was negatively correlated with CDK5RAP3 in stable gastric cancer cell lines. CDK5RAP3 repressed AKT phosphorylation, which promoted GSK-3β phosphorylation, thereby suppressing β-catenin protein expression and, consequently, gastric cancer. The protein level of CDK5RAP3 was markedly decreased in most gastric tumor tissues compared with adjacent non-tumor tissues, and the levels of p-AKT (Ser473) and p-GSK-3β (Ser9) were also negatively correlated with those of CDK5RAP3. The prognostic value of CDK5RAP3 for overall survival was found to be dependent on AKT phosphorylation.ConclusionOur results demonstrated that CDK5RAP3 negatively regulates the Wnt/β-catenin signaling pathway by repressing AKT phosphorylation, which leads to better survival of patients with gastric cancer.

MiR-1298 expression correlates with prognosis and inhibits cell proliferation and invasion of gastric cancer.

To explore the association between miR-1298 expression and clinicopathological factors, prognosis of gastric cancer (GC) patients and biological functions underlying the GC progression. Expression of miR-1298 was examined by qRT-PCR in GC tissues and cells, the adjacent normal tissues and normal gastric cell line GES-1 cells were used as controls. Association of disease-free survival (DFS) and overall survival (OS) time with miR-1298 expression was analyzed by Kaplan-Meier analysis and log-rank test. Univariate and multivariate analysis were also performed to analyze relative prognostic risk factors of GC patients. Cell proliferation and invasion assays were used to examine cell proliferation and invasion capacities in vitro. The relative protein expression was analyzed by Western blot analysis. MiR-1298 expression was lower in GC tissues and cells, compared to adjacent normal tissues and GES-1 cells, respectively. Lower miR-1298 expression levels were associated with lymph node metastasis and TNM stage. Kaplan-Meier analysis showed that lower miR-1298 expression predicted poor DFS and OS of GC patients. Furthermore, we demonstrated that lymph node metastasis, TNM stage, and lower miR-1298 expression were independent risk factors for DFS and OS in GC patients. In vitro, miR-1298 overexpression inhibited cell proliferation and invasion abilities. Additionally, our results revealed that miR-1298 overexpression suppressed PI3K/AKT signaling pathway in GC cells. Our evidence indicated that miR-1298 may provide a specifically promising target for therapy of GC patients.

MicroRNA-28 promotes cell proliferation and invasion in gastric cancer via the PTEN/PI3K/AKT signalling pathway.

Gastric cancer is the fourth most common malignant disease and second leading cause of cancer‑associated mortalities worldwide. Previous studies revealed aberrantly expressed microRNAs (miRNAs) in various types of human cancer; these miRNAs play important roles in tumourigenesis and tumour development. miRNAs present a considerable potential for novel therapeutic approaches for treating human cancer. Therefore, the investigation of novel miRNAs involved in gastric cancer progression provides an opportunity to improve the prognosis of patients with gastric cancer. miRNA‑28 (miR‑28) has been investigated with regards to its expression and biological functions in many types of human cancer. However, previous studies have not discussed the expression patterns, roles and associated molecular mechanisms of miR‑28 in gastric cancer. In the present study, miR‑28 expression was identified to be upregulated in gastric cancer tissues and cell lines. miR‑28 inhibition functionally inhibited cell proliferation and invasion in gastric cancer invitro. Using bioinformatics analysis, luciferase reporter assay, reverse transcription‑quantitative polymerase chain reaction and western blot analysis, phosphatase and tensin homolog(PTEN) was mechanically identified as a direct target of miR‑28 in gastric cancer. PTEN was downregulated in gastric cancer and negatively correlated with miR‑28 levels. Inhibition of PTEN restored the biological effects of miR‑28 downregulation on the proliferation and invasion of gastric cancer cells. Notably, the downregulation of miR‑28 results in the regulation of the phosphatidylinositol 3‑kinase/protein kinase B signaling pathway in gastric cancer. These results suggested that miR‑28 may be targeted for the development of novel treatments for gastric cancer in the future.

Isoprenaline/\u03b22-AR activates Plexin-A1/VEGFR2 signals via VEGF secretion in gastric cancer cells to promote tumor angiogenesis

BackgroundThe role of stress signals in regulating gastric cancer initiation and progression is not quite clear. It is known that stress signals modulate multiple processes such as immune function, cell migration and angiogenesis. However, few studies have investigated the mechanisms of how stress signals contribute to gastric cancer angiogenesis.MethodsHere, we used β2-adrenergic receptor (β2-AR) agonist isoprenaline to imitate a stress signal and demonstrated the molecular mechanism underlying stress’s influence on tumor angiogenesis.ResultsWe found that isoprenaline stimulated vascular endothelial growth factor (VEGF) secretion in gastric cancer cells and plexin-A1 expression was induced by human recombinant VEGF165 in both gastric cancer cells and vascular endothelial cells. Furthermore, interfere with plexin-A1 expression in gastric cancer cells influence HUVEC tube formation, migration and tumor growth in vivo.ConclusionsThese findings suggest that isoprenaline stimulate VGEF secretion and subsequently up-regulate the expression of plexin-A1 and VEGFR2 in gastric cancer cells, which form a positive impetus to promote tumor angiogenesis. This study reveals a novel molecular mechanism that a stress signal like isoprenaline may enhance angiogenesis via activating plexin-A1/VEGFR2 signaling pathway in gastric cancer, which may be a potential target in development of an anti-angiogenic therapy for gastric cancer.

Extracellular matrix protein 1 promotes cell metastasis and glucose metabolism by inducing integrin β4/FAK/SOX2/HIF-1α signaling pathway in gastric cancer.

Extracellular matrix protein 1 (ECM1) is related to strong invasiveness and poor prognosis in major malignancies, but the underlying mechanism remains unknown. Here we aimed to elucidate the function of ECM1 on cell metastasis and glucose metabolism in gastric cancer (GC). The level of ECM1 in sera and tissues of patient with GC were positively correlated with tumor invasion and recurrence. Genetic manipulation of ECM1 expression affected cell metastasis and glucose metabolism in GC cell lines. Enhanced ECM1 expression facilitated gene expression levels associated with epithelial-mesenchymal transition (EMT) and glucose metabolism. Interestingly, our results indicated that ECM1 directly interacted with integrin β4 (ITGB4) and activated ITGB4/focal adhesion kinase (FAK)/glycogen synthase kinase 3β signaling pathway, which further induced the expression of transcription factor SOX2. Aberrant expression of SOX2 altered gene expression of EMT factors and glucose metabolism enzymes. Furthermore, SOX2 enhanced hypoxia-inducible factor α (HIF-1α) promoter activity to regulate glucose metabolism. The micro-positron emission tomography/computed tomography imaging of xenograft model showed that ECM1 substantially increased 18F-fluorodeoxyglucose uptake in xenograft tumors. Using in vivo mouse tail vein injection experiments, ECM1 was also found to increase in lung surface metastasis. These findings provide evidence that ECM1 regulates GC cell metastasis and glucose metabolism by inducing ITGB4/FAK/SOX2/HIF-1α signal pathway and have important implications for the development of therapeutic target to prevent tumor metastasis and recurrence.

CD133 mediates the TGF-β1-induced activation of the PI3K/ERK/P70S6K signaling pathway in gastric cancer cells.

Cluster of differentiation (CD)133 has been reported to be involved in the activation of the extracellular signal-regulated kinase (ERK) signaling pathway in different types of cancer cells. CD133 has been reported to be involved in the activation of the ERK signaling pathway in various cancer cells. Transforming growth factor (TGF)-β1 has also been reported to mediate the activation of the ERK signaling pathway. In addition, TGF-β1 has been previously shown to mediate the activation of the ERK signaling pathway. Hence, the present study investigated the function of CD133 in the TGF-β1-induced activation of the ERK/P70S6K signaling pathway in human gastric cancer (GC) cells. To this end, GC cell lines SGC7901 and MKN45 were treated with TGF-β1. The expression of CD133, phospho-ERK (p-ERK) and phospho-P70S6 kinase (p-P70S6K) was upregulated in the cells treated with TGF-β1, while the expression of ERK and P70S6K was not altered. To investigate whether CD133 is involved in the TGF-β1-induced activation of the ERK/P70S6K signaling pathway in GC cells, immunomagnetic cell sorting was employed to isolate CD133+ GC cells, and a CD133-expression construct or CD133-targeting small interfering ribonucleic acids were transfected into cells to modulate the expression of CD133. Subsequently, the expression of CD133, ERK, p-ERK, P70S6K, and p-P70S6K was analyzed by western blotting. The CD133+ cells displayed a high expression of p-ERK and p-P70S6K. Furthermore, SGC7901 GC cells were treated with U0126, an inhibitor of the ERK signaling pathway, to assess whether CD133 is upstream of ERK/P70S6K. The results showed that the expression of p-ERK and p-P70S6K was downregulated in the cells treated with U0126, while the expression of CD133 remained unaltered. The above preliminary results showed that CD133 likely mediates the TGF-β1-induced activation of the ERK/P70S6K signaling pathway in human GC cells. To further understand the mechanism of regulation of the ERK/P70S6K signaling pathway by CD133, the expression of CD133 was modulated by transfecting cells with CD133-expression constructs or CD133-targeting small interfering ribonucleic acids. Results indicated that overexpression and silencing of CD133 directly increased and decreased the expression of p-ERK and p-P70S6K, respectively. Therefore, we hypothesized that CD133 mediates the TGF-β1-induced activation of the PI3K/ERK/P70S6K signaling pathway in human GC cells.

Luteolin induces apoptosis in vitro through suppressing the MAPK and PI3K signaling pathways in gastric cancer.

Luteolin, an active component of traditional Chinese medicine, exhibits potential for anti-tumor proliferation; however, the molecular events occurring in such process and the signal transduction pathways involved are currently unknown. Our group previously reported that luteolin inhibited proliferation and induced apoptosis in the gastric cancer cell line BGC-823. The aim of the present study was to investigate the mechanism by which the mitogen-activated protein kinase (MAPK) and phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K) signaling pathways regulate the apoptosis in vitro of BGC-823 cells following treatment with luteolin. It was observed that luteolin induced apoptosis through the intrinsic pathway by increasing the levels of caspase-3, caspase-9 and cytochrome c, and the ratio of B-cell lymphoma (Bcl)-2 associated X protein (Bax) to Bcl-2. Luteolin suppressed the phosphorylation of extracellular signal-regulated kinase in the MAPK signaling pathway, as well as suppressing the phosphorylation of AKT, PI3K and mechanistic target of rapamycin in the PI3K signaling pathway. In addition, luteolin combined with LY294002 markedly increased the Bax/Bcl-2 ratio, while when combined with U0126, luteolin had less effects on the Bax/Bcl-2 ratio compared with luteolin treatment alone, suggesting that both the MAPK and PI3K signaling pathways are involved in the apoptosis induced by luteolin. Furthermore, luteolin attenuated the MAPK and PI3K signaling pathways by increasing the expression of specific dual-specificity phosphatases and decreasing the expression of chemokine (C-X-C motif) ligand 16 at the messenger RNA level, respectively. Taken together, the present results demonstrate that luteolin is a potential chemotherapeutic agent against gastric cancer by exerting a dual inhibition on the MAPK and PI3K signaling pathways.

CMIP is oncogenic in human gastric cancer cells.

Gastric cancer is one of the most common cancers and the second leading cause of cancer-associated mortality worldwide. Recurrence, metastasis and resistance to drug treatment are the main barrier to survival of patients with advanced stage gastric cancer. Further study of the molecular mechanisms involved will improve the therapeutic options for gastric cancer. In a previous study, c-Maf was discovered as an oncogene transduced in the avian AS42 retrovirus, and was found to be overexpressed in multiple myeloma and angioimmunoblastic T-cell lymphoma. c-Maf inducing protein (CMIP) is involved in the c-Maf signaling pathway, which was reported to serve an important role in human minimal change nephrotic syndrome and in human reading and language related behavior. However, the relationship between CMIP and human gastric cancer has not yet been reported. In the present study, CMIP protein levels in gastric cancer tissues and cells were measured using immunohistochemistry and western blot analysis; the expression of CMIP protein was significantly higher in gastric cancer tissues compared with normal gastric tissues. Expression was positively associated with poorer clinical parameters, relapse-free survival and overall survival. Furthermore, using cell counting, Cell Counting Kit-8, colony formation, wound healing and Transwell assays, together with flow cytometry, CMIP depletion by RNA interference was observed to reduce the capacity of gastric cancer cells to proliferate and migrate in vitro. Furthermore, the upstream and downstream genes of CMIP were analyzed by luciferase reporter assay and reverse transcription quantitative polymerase chain reaction, which indicated that CMIP was a direct target of miR-101-3p. In addition, CMIP knockdown was observed to result in the downregulation of MDM2 and mitogen activated protein kinase (MAPK) expression at the mRNA level. In conclusion, CMIP demonstrated an oncogenic role in human gastric cancer cells. Furthermore, microRNA-101-3p, MDM2 and MAPK were involved in the CMIP signaling pathway in gastric cancer. CMIP could be a novel target for further investigation in the clinical therapeutic management of gastric cancer.

Resveratrol reverses Doxorubicin resistance by inhibiting epithelial-mesenchymal transition (EMT) through modulating PTEN/Akt signaling pathway in gastric cancer

BackgroundGastric cancer is one of the major causes of cancer-related mortality worldwide. Most of patients presenting with inoperable gastric cancers rely on systemic chemotherapy for prolongation of survival. Doxorubicin (DOX) is one of the important agents against gastric cancer. Acquired DOX-resistance severely impedes the chemotherapeutic effect, invariably leading to poor prognosis. Resveratrol (RES) as a kind of phytoalexin has demonstrated anti-tumor functions in breast cancer and myeloid leukemia, but its function and mechanism are still unknown in gastric cancer treatment.MethodsCCK8 assay was used to detect the cytotoxicity of DOX and RES to gastric cancer cells. DOX-resistant subclone cell line (SGC7901/DOX) was derived from SGC7901 cells exposed to stepwise increasing concentrations of DOX treatment. We measured the migratory capabilities of SGC7901/DOX cells by Cell scratch test and Transwell assay. SGC7901/DOX cells were treated with DOX, RES, neither or both. Then we analyzed cell survival by CCK8 assay, colony formation by Colony-forming assay, cell apoptosis by Annexin-V-FITC and PI dual staining assay and cell migration by Cell scratch test and Transwell assay. Western blotting was conducted to detect the protein expressions of PTEN/Akt signaling pathway and EMT-related markers. Immunofluorescence was performed to confirm the EMT-related markers expressions. The xenograft model was used to assess the effect of DOX and RES in vivo. The key molecules associated with proliferation, apoptosis and EMT were evaluated by immunohistochemistry in tumor specimens.ResultsSGC7901/DOX cells acquired drug resistance and enhancive migratory capability. RES enabled SGC7901/DOX cells to regain DOX sensitivity, mitigated the aggressive biological features, promoted cell apoptosis in vitro and inhibited tumor growth in vivo. Mechanistic studies revealed that SGC7901/DOX cells underwent epithelial-mesenchymal transition (EMT) which was induced by Akt activation, and through activating PTEN, RES inhibited the Akt pathway, and then achieved the reversion of EMT.ConclusionRES serves as a novel solution to reverse the DOX-resistance of gastric cancer via preventing EMT by modulating PTEN/Akt signaling pathway. DOX-RES combined treatment provides a promising future for gastric cancer patients to postpone drug resistance and prolong survival.

MAGI1 inhibits migration and invasion via blocking MAPK/ERK signaling pathway in gastric cancer.

ObjectiveTo explore the association of membrane-associated guanylate kinase inverted 1 (MAGI1) with gastric cancer (GC) and the related molecular mechanisms.MethodsThe reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry (IHC) were utilized to measure the MAGI1 expression level in GC tissues. Quantitative real-time PCR and Western blotting were used to ensure the MAGI1 expression in GC cell lines. Small hairpin RNA (shRNA) was applied for knockdown of endogenous MAGI1 in GC cells. MTT assay and colony formation assay, scratch wounding migration assay and transwell chamber migration assay, as well as transwell chamber invasion assay were employed respectively to investigate the GC cell proliferation, migration and invasion in MAGI1-knockdown and control GC cells. The potential molecular mechanism mediated by MAGI1 was studied using Western blotting and RT- PCR.ResultsRT-PCR and IHC verified MAGI1 was frequently expressed in matched adjacent noncancerous mucosa compared with GC tissues and the expression of MAGI1 was related to clinical pathological parameters. Functional assays indicated that MAGI1 knockdown significantly promoted GC cell migration and invasion. Further mechanism investigation demonstrated that one pathway of MAGI1 inhibiting migration and invasion was mainly by altering the expression of matrix metalloproteinases (MMPs) and epithelial-mesenchymal transition (EMT)-related molecules via inhibiting MAPK/ERK signaling pathway.ConclusionsMAGI1 was associated with GC clinical pathological parameters and acted as a tumor suppressor via inhibiting of MAPK/ERK signaling pathway in GC.

MiRNA-194 activates the Wnt/β-catenin signaling pathway in gastric cancer by targeting the negative Wnt regulator, SUFU

Emerging evidence has shown that miRNA-194 is aberrantly upregulated in gastric cancer (GC); however, the biological mechanisms underlying its involvement are largely unknown. Wnt/β-catenin signaling has been implicated in gastric tumorigenesis; we therefore hypothesized that miRNA-194 promotes gastric carcinogenesis by activating Wnt/β-catenin signaling. MiRNA-194 was found to be overexpressed in GC cell lines and 43 paired GC tissues. Overexpression of miRNA-194 promoted cell proliferation and migration, while inhibition of miRNA-194 blocked these processes. Inhibition of miRNA-194 decreased tumor volumes in nude mice. Furthermore, miRNA-194 inhibitors promoted cytoplasmic localization of β-catenin, leading to repression of Wnt signaling. We also discovered that SUFU, a known negative regulator of Hedgehog and Wnt signaling, was a target of miRNA-194. Anti-SUFU siRNAs rescued the inhibitory effects of miRNA-194 antagonists on cell proliferation and migration and on colony formation. We also found that SUFU expression was downregulated in GC tissues and cell lines and negatively correlated with miRNA-194 expression in primary GC tissues. Moreover, SUFU expression was negatively correlated with tumor stage, supporting its potential as a diagnostic or prognostic marker in GC. Taken together, these findings suggest that miRNA-194 is oncogenic and promotes GC cell proliferation and migration by activating Wnt signaling, at least in part, via suppression of SUFU.

RLIP76 increases apoptosis through Akt/mTOR signaling pathway in gastric cancer.

RLIP76 is a stress-responsive multifunctional protein and is usually overexpressed in malignant carcinomas. It plays a significant role in multiple cellular biological behaviors, including cell growth, motility, division and apoptosis, in many types of malignant cells. However, functions of RLIP76 in gastric cancer (GC) remain unknown. In the present study, RLIP76 was overexpressed in GC tissues by immunohistochemistry. RLIP76-targeted shRNA-containing lentivirus (KD) and the scrambled shRNA (NC) were used to explore the knockout of RLIP76 on cellular functions of human GC SGC-7901 and MGC-803 cells. Quantitative RT-PCR and western blotting were used to confirm that the RLIP76 was suppressed both on mRNA and protein levels after transfection. The mRNA level in SGC-7901 and MGC-803 after transfection of RLIP76-targeted shRNA was 0.245722±0.021077 (p<0.05) and 0.225389±0.00974 (p<0.05), respectively. Our results showed that the konckdown of RLIP76 downregulated cell growth after 24 h in Cell Counting Kit-8 (CCK-8) assay, reduced migration from 486.7±128.8 to 219.7±43.6 in SGC-7901 (p<0.05) and from 630±95 to 333.7±46.5 in MGC-803 (p<0.05), decreased invasion from 306±33.5 to 97.7±24.3 in SGC-7901 (p<0.05) and from 350±50.9 to 163.3±87.5 in MGC-803 (p<0.05). Length of vascular endothelial growth factor (VEGF)-induced tube formation also decreased from 202.8±83.3 to 44.5±3.69 in SGC-7901 and from 193±3.5 to 71.8±8.83 in MGC-803 (p<0.05). Phosphorylation level of Akt declined from 138.45±13.8 to 69.9±29.7% in SGC-7901, and from 115.5±26.6 to 49.07±27% in MGC-803 (p<0.05) and phosphorylation level of mTOR also significantly decreased (p<0.05). While apoptosis of GC cells increased which we verified with apoptosis proteins and staining analysis. Our data showed that RLIP76 plays a significant oncogenic role in GC and it maybe a potential target in GC treatment.

MiR-302b regulates cell cycles by targeting CDK2 via ERK signaling pathway in gastric cancer.

To investigate the molecular mechanism of miR‐302b in the regulation of cell proliferation and cell cycle regulation in gastric cancer. Samples of tumor and adjacent normal tissues were collected from 30 gastric cancer patients. Bioinformatics and the dual luciferase report were used for verification of the relationship between miR‐302b expression and cyclin‐dependent kinase 2 (CDK2). RT‐PCR and western blot were used to examine CDK2 mRNA and protein levels. The impacts of miR‐302b on CDK2 expression and extracellular signal‐regulated kinase (ERK) signaling pathway were assessed in cells transfected with miR‐302b analogs and CDK2 overexpression carrier, respectively. We used 3‐(4,5‐dimethylthiazol‐2‐yl)‐2, 5‐diphenyltetrazolium bromide (MTT) to assay gastric cancer cell growth after transfection, flow cytometry to analyze cell cycle. Compared with normal tissues, miR‐302b expression was significantly lower in gastric cancer tissues, which was significantly related to lymph node metastasis, metastasis distance, and TNM staging. miR‐302b expression was increased in miR‐302b mimics transfected cells and was significantly decreased in miR‐302b inhibitors transfected cells. CDK2 is a target gene of miR‐302b. Decreased miR‐302b and increased CDK2 expressions can significantly promote proliferation and G1/S phase transformation in gastric cancer. miR‐302b promoted the proliferation of gastric cancer cells through upregulation of CDK2, thereby inhibiting ERK pathway, which can in turn inhibit the promoting ability of miR‐302b on proliferation. The upregulation of miR‐302b reduced the expression of CDK2, and inhibited ERK signaling pathway, thereby inhibiting cell proliferation and G1/S phase conversion rate. Therefore, miR‐302b provides new perspectives for research of cell regulation and proliferation in gastric cancer, and new targets for gastric cancer diagnosis and treatment.

Linifanib (ABT-869) Potentiates the Efficacy of Chemotherapeutic Agents through the Suppression of Receptor Tyrosine Kinase-Mediated AKT/mTOR Signaling Pathways in Gastric Cancer.

Gastric cancer, highly dependent on tumor angiogenesis, causes uncontrolled lethality, in part due to chemoresistance. Here, we demonstrate that linifanib (ABT-869), a novel multi-targeted receptor tyrosine kinase inhibitor, markedly augments cytotoxicity of chemotherapies in human gastric cancer. ABT-869 and chemotherapeutic agents exhibited a strong synergy to inhibit the viability of several gastric cancer cell lines, with combination index values ranging from 0.017 to 0.589. Additionally, the combination of ABT-869 and chemotherapeutic agents led to remarkable suppression of vascular endothelial growth factor (VEGF)-induced angiogenesis in vitro and in vivo. Importantly, in a preclinical gastric cancer xenograft mouse model, drug co-treatments led to increased mouse survival as well as a synergistic reduction in tumor size and the inhibition of tumor angiogenesis. Mechanistic studies further revealed that all of the co-treatments containing ABT-869 resulted in decreased activation of the VEGF receptor, the epidermal growth factor receptor and the insulin growth factor receptor. Inhibition of these receptor tyrosine kinases consequently attenuated the activation of the downstream AKT/mTOR signaling pathway both in cultured gastric cancer cells and in gastric cancer xenografts. Collectively, our findings suggest that the addition of ABT-869 to traditional chemotherapies may be a promising strategy for the treatment of human gastric cancer.

AURKA induces EMT by regulating histone modification through Wnt/β-catenin and PI3K/Akt signaling pathway in gastric cancer.

Gastric cancer, a highly invasive and aggressive malignancy, is the third leading cause of death from cancer worldwide. Genetic association studies have successfully revealed several important genes consistently associated with gastric cancer to date. However, these robust gastric cancer-associated genes do not fully elucidate the mechanisms underlying the development and progression of the disease. In the present study, we performed an alternative approach, a gene expression-based genome-wide association study (eGWAS) across 13 independent microarray experiments (including 251 gastric cancer cases and 428 controls), to identify top candidates (p<0.00001). Additionally, we conducted gene ontology analysis, pathway analysis and network analysis and identified aurora kinase A (AURKA) as our candidate. We observed that MLN8237, which is a specific inhibitor of AURKA, decreased the β-catenin and the phosphorylation of Akt1 and GSK-3β, as well as blocked the Akt and Wnt signaling pathways. Furthermore, MLN8237 arrested the cells in the G2/M phase. The activity of Wnt and Akt signaling pathways affected the level of histone methylation significantly, and we supposed that MLN8237 affected the level of histone methylation through these two signaling pathways. Additionally, the treatment of MLN8237 influenced the level of H3K4 me1/2/3 and H3K27 me1/2/3. Chip data on cell lines suggested that MLN8237 increases the level of H3K27 me3 on the promoter of Twist and inhibits EMT (epithelial-mesenchymal transition). In summary, AURKA is a potential therapeutic target in gastric cancer and induces EMT through histone methylation.