Androgen receptor promotes cell stemness via interacting with co-factor YAP1 in gastric cancer.

Cancer stem cells (CSCs) have been proposed to explain tumor relapse and chemoresistance in various types of cancers, and androgen receptor (AR) has been emerged as a potential regulator of stemness in cancers. However, the underlying mechanism of AR-regulated CSCs properties and chemoresistance in gastric cancer (GC) remains unknown. Here, we shown that AR is upregulated in GC tissues and correlates with poor survival rate and CSCs phenotypes of GC patients. According to our experimental data, overexpression of AR upregulated the expression of CSCs markers and this was consistent with the result concluded from data analysis that the expression of AR was positively correlated with CD44 in GC patients. In addition, AR overexpression obviously enhanced the tumor sphere formation ability and chemoresistance of GC cells in vitro. Whereas these effects were attenuated by inhibition of AR. These results were further validated in vivo that MGC-803 cells overexpressing AR had stronger properties to initiate gastric tumorigenesis than the control cells, and inhibition of AR increased the chemosensitivity of GC cells. Mechanically, AR upregulated CD44 expression by directly binding to its promoter region and Yes-associated protein 1 (YAP1) served as the co-factor of AR, which was demonstrated by the fact that the promoting effects of AR on GC cells stemness were partially counteracted by YAP1 knockdown. Thus, this study revealed that AR facilitates CSCs properties and chemoresistance of GC cells via forming complex with YAP1and indicates a potential therapeutic approach to GC patients.

BPTF Drives Gastric Cancer Resistance to EGFR Inhibitor by Epigenetically Regulating the C-MYC/PLCG1/Perk Axis.

Erlotinib, an EGFR tyrosine kinase inhibitor, is used for treating patients with cancer exhibiting EGFR overexpression or mutation. However, the response rate of erlotinib is low among patients with gastric cancer (GC). The findings of this study illustrated that the overexpression of bromodomain PHD finger transcription factor (BPTF) is partially responsible for erlotinib resistance in GC, and the combination of the BPTF inhibitor AU-1 with erlotinib synergistically inhibited tumor growth both in vivo and in vitro. AU-1 inhibited the epigenetic function of BPTF and decreased the transcriptional activity of c-MYC on PLCG1 by attenuating chromosome accessibility of the PLCG1 promoter region, thus decreasing the expression of p-PLCG1 and p-Erk and eventually improving the sensitivity of GC cells to erlotinib. In patient-derived xenograft (PDX) models, AU-1 monotherapy exhibited remarkable tumor-inhibiting activity and is synergistic anti-tumor effects when combined with erlotinib. Altogether, the findings illustrate that BPTF affects the responsiveness of GC to erlotinib by epigenetically regulating the c-MYC/PLCG1/pErk axis, and the combination of BPTF inhibitors and erlotinib is a viable therapeutic approach for GC.

The roles and molecular mechanisms of long non-coding RNA WT1-AS in the maintenance and development of gastric cancer stem cells.

It has been proposed that cancer stem cells (CSCs) are responsible for almost all malignant phenotypes of tumors. Long non-coding RNA WT1 antisense RNA (WT1-AS) has been found to be implicated in lung cancer cell stemness. However, the roles and molecular mechanisms of WT1-AS in the development of gastric cancer stem cells (GCSCs) remain unknown. Our present study showed that WT1-AS negatively regulated WT1 expression in GCSCs. WT1-AS knockdown or Wilms' tumor 1 (WT1) overexpression improved GCSC proliferative and migratory capacities, inhibited GCSC apoptosis, potentiated the resistance of GCSCs to 5-FU, promoted GCSC EMT, induced HUVEC angiogenesis, enhanced GCSC stemness, and facilitated in-vitro 3D GCSC aggregate formation. WT1-AS overexpression exerted reverse effects. WT1-AS ameliorated the malignant phenotypes of GCSCs by down-regulating WT1 in vitro. WT1-AS inhibited tumor growth and metastasis, and reduced tumor stemness in GCSCs-derived (s.c., i.p., and i.v.) xenografts in vivo. Moreover, XBP1 was identified as an upstream regulator of WT1-AS in GCSCs. Also, 4 potential WT1-AS downstream targets (i.e. PSPH, GSTO2, FYN, and PHGDH) in GCSCs were identified. Additionally, CACNA2D1 was demonstrated to be a downstream target of the WT1-AS/WT axis. XBP1 or CACNA2D1 knockdown exerted an adverse effect on the maintenance of stem cell-like behaviors and characteristics of GCSCs. In conclusion, WT1-AS weakened the stem cell-like behaviors and characteristics of GCSCs in vitro and in vivo by down-regulating WT1. Investigations into the molecular mechanisms underlying the complex phenotypes of GCSCs might contribute to the better management of gastric cancer.

Aldehyde Dehydrogenase 1 in Gastric Cancer.

Gastric cancer (GC) is a disease that threatens human health. It is thus crucial to clarify the mechanisms involved in GC development and discover diagnostic biomarkers and therapeutics. As a cancer stem cell marker, aldehyde dehydrogenase 1 (ALDH1) is involved in the development, progression, and treatment of GC. This review evaluated the prognostic value of ALDH1 and explored its mechanism of action in GC. Importantly, ALDH1 is an informative biomarker in clinical practice as it has specific relationships with indicators, such as metastasis and overall survival. Additionally, ALDH1 interacts with genes and exhibits properties that mimic stem cell characteristics amongst other mechanisms employed in the occurrence and progression of GC. Our results, therefore, provide evidence of possible clinical utility of ALDH1 as a GC therapeutic target.

Crocetin suppresses angiogenesis and metastasis through inhibiting sonic hedgehog signaling pathway in gastric cancer.

Gastric cancer (GC) is one of the major causes of cancer-related deaths and chemoresistance is a key obstacle to the treatment of GC, particularly in advanced GC. As an active component of saffron stigma, crocetin has important therapeutic effects on various diseases including tumors. However, the therapeutic potential of crocetin targeting GC is still unclear and the underlying mechanisms are remained to be further explored. In this study, crocetin significantly inhibited angiogenesis in GC, including tubes of HUVECs and vasculogenic mimicry (VM) formation of GC cells. Crocetin also suppressed cell proliferation, migration and invasion. To explore which signaling pathway involving in crocetin, HIF-1α, Notch1, Sonic hedgehog (SHH) and VEGF were examined with crocetin treatment and we found that SHH significantly decreased. Crocetin suppressed SHH signaling with SHH, PTCH2, Sufu and Gli1 protein level decreased in western blot assay. In addition, crocetin suppressed SHH secretion in GC and HUVEC cells. The promoted effects on cell migration induced by secreted SHH were also inhibited by crocetin in GC and HUVEC cell co-culture system. Furthermore, recombinant SHH promoted angiogenesis as well as cell migration and proliferation. However, these promoted effects were reversed by crocetin treatment. These results revealed that crocetin suppressed GC angiogenesis and metastasis through SHH signaling pathway, indicating that crocetin may function as an effective therapeutic drug against GC.

Identification of ARGLU1 as a potential therapeutic target for gastric cancer based on genome-wide functional screening data.

BACKGROUND: Due to the molecular mechanism complexity and heterogeneity of gastric cancer (GC), mechanistically interpretable biomarkers were required for predicting prognosis and discovering therapeutic targets for GC patients. METHODS: Based on a total of 824 GC-specific fitness genes from the Project Score database, LASSOCox regression was performed in TCGA-STAD cohort to construct a GC Prognostic (GCP) model which was then evaluated on 7 independent GC datasets. Targets prioritization was performed in GC organoids. ARGLU1 was selected to further explore the biological function and molecular mechanism. We evaluated the potential of ARGLU1 serving as a promising therapeutic target for GC using patients derived xenograft (PDX) model. FINDINGS: The 9-gene GCP model showed a statistically significant prognostic performance for GC patients in 7 validation cohorts. Perturbation of SSX4, DDX24, ARGLU1 and TTF2 inhibited GC organoids tumor growth. The results of tissue microarray indicated lower expression of ARGLU1 was correlated with advanced TNM stage and worse overall survival. Over-expression ARGLU1 significantly inhibited GC cells viability in vitro and in vivo. ARGLU1 could enhance the transcriptional level of mismatch repair genes including MLH3, MSH2, MSH3 and MSH6 by potentiating the recruitment of SP1 and YY1 on their promoters. Moreover, inducing ARGLU1 by LNP-formulated saRNA significantly inhibited tumor growth in PDX model. INTERPRETATION: Based on genome-wide functional screening data, we constructed a 9-gene GCP model with satisfactory predictive accuracy and mechanistic interpretability. Out of nine prognostic genes, ARGLU1 was verified to be a potential therapeutic target for GC. FUNDING: National Natural Science Foundation of China.

CTHRC1 promotes gastric cancer metastasis via HIF-1α/CXCR4 signaling pathway.

Metastasis is the main cause of gastric cancer (GC) related death and the underlying mechanisms still remain unclear. Collagen triple helix repeat containing 1 (CTHRC1) protein is known to be involved in tissue remodeling processes and closely associated with carcinogenesis and metastasis in solid tumors, but the functional role of CTHRC1 and its underlying mechanism with tumor metastasis in GC have not been fully illuminated. In the present study, CTHRC1 was highly expressed in tumor tissues and associated with poor prognosis of GC according to TCGA and GEO database. Functional studies revealed that CTHRC1 overexpression in GC significantly increased cell migration and invasion capacity. However, the promoting effects were abolished subsequent to silencing of CXCR4. In addition, CTHRC1 increased CXCR4 expression through upregulating HIF-1α expression, which eventually contributed to the promotion of cell migration and invasion. Inhibiting HIF-1α expression decreased CXCR4 expression and suppressed cell migration and invasion in GC. These results substantiated our hypothesis that HIF-1α/CXCR4 signaling pathway mediated the promoting effect of CTHRC1 on cell migration and invasion in GC.

CagA increases DNA methylation and decreases PTEN expression in human gastric cancer.

Gastric cancer is one of the leading causes of cancer-associated mortality worldwide. Cytotoxin­associated gene A (CagA) has been reported to be associated with gastric diseases. Phosphatase and tensin homolog (PTEN) and tet methylcytosine dioxygenase 1 (Tet1) are important tumor­suppressor genes. The present study aimed to investigate the underlying functions of CagA in human gastric cancer, and to explore the associations between CagA, PTEN and Tet1 in gastric cancer. For that purpose, CagA overexpression and Tet1 interference recombinant lentiviral plasmids were constructed. Quantitative polymerase chain reaction (qPCR) was utilized to screen gene expression in HGC­27 human gastric cancer cells overexpressing CagA. qPCR and western blotting were used to detect gene and protein expression, respectively. In addition, the methylation status of PTEN was detected by methylation­specific PCR. The expression levels of PTEN, Tet1, apolipoprotein B mRNA editing enzyme catalytic subunit (APOBEC)3A, APOBEC3C and APOBEC3F were significantly decreased in the CagA overexpression group compared with in the negative control group in HGC­27 cells. Compared with in the negative control group, the mRNA and protein expression levels of PTEN were markedly decreased in cells with Tet1 interference. The decreased expression of PTEN was associated with increased methylation levels in the cells. In addition, the protein expression levels of PTEN were significantly decreased in HGC­27 cells when CagA was overexpressed. The expression levels of PTEN and Tet1 were also markedly decreased in CagA+ gastric cancer tissues compared with in non­cancerous tissues. The decreased expression of PTEN in CagA+ gastric cancer tissues was associated with increased methylation levels. In conclusion, overexpression of CagA significantly decreased the expression of PTEN, Tet1, APOBEC3A, APOBEC3C and APOBEC3F in human gastric cancer. In addition, CagA increased DNA methylation and decreased PTEN expression, which was reversed by Tet1 overexpression. The present study may facilitate future therapeutic approaches targeting human gastric cancer.

G9A promotes gastric cancer metastasis by upregulating ITGB3 in a SET domain-independent manner.

Tumor metastasis is the leading cause of death in patients with advanced gastric cancer (GC). Limited therapeutic regimens are available for this condition, which is associated with a poor prognosis, and the mechanisms underlying tumor metastasis remain unclear. In the present study, increased histone methyltransferase G9A expression in GC tissues correlated with advanced stage and shorter overall survival, and in vitro and in vivo experiments revealed that G9A promoted tumor invasion and metastasis. Moreover, we observed that Reg IV induced G9A via the p-ERK/p-SP1 pathway. SP1 directly binds the G9A promoter and enhances G9A expression, and upregulated G9A then forms a transcriptional activator complex with P300 and GR, thereby promoting ITGB3 expression induced by dexamethasone (DEX) and contributing to GC metastasis. However, the G9A-mediated increase in ITGB3 expression was not dependent on the SET domain and methyltransferase activity of G9A. This study demonstrates that G9A is an independent prognostic marker and promotes metastasis in GC, thus suggesting that it may be a tumor biomarker and potential therapeutic target in GC.

ALEX1, a novel tumor suppressor gene, inhibits gastric cancer metastasis via the PAR-1/Rho GTPase signaling pathway.

BACKGROUND: The ALEX is a novel member of the armadillo family and ALEX1 was reported to be reduced or even lost in multiple solid tumors. However, its expression profile and oncogenic role in gastric cancer (GC) remains largely unknown. METHODS: ALEX1 expression was detected in 161 GC samples by immunohistochemistry staining. NCI-N87 cells transfected by ALEX1 lentivirus vectors and MKN28 cells transfected by ALEX1 shRNA were used for biological function investigation. Western blot was applied to explore the molecular mechanism and pull-down assays were applied to measure the activity of Rho GTPases. In vivo tumorigenicity, peritoneal and lung metastasis experiments were performed by tumor cell engraftment into nude mice. Bisulfite genomic sequencing and methylation-specific PCR were applied to check the methylation status of the ALEX1 gene. RESULTS: The expression rate of ALEX1 was significantly reduced in gastric tumor samples compared to non-tumor samples (43.5 vs. 90.2%), and its expression was closely related to the tumor differentiation, TNM staging, and lymph nodes metastasis. ALEX1 overexpression in NCI-N87 cells significantly inhibited cell proliferation, migration, and invasion in vitro, and disrupted the structure of the cytoskeleton. ALEX1 overexpression attenuated xenografts growth, peritoneal, and lung metastasis in nude mice. Mechanistically, the overexpression of ALEX1 inhibits thrombin-induced metastasis and Rho GTPases activation. Bisulfite genomic sequencing and methylation-specific PCR revealed that the promoter of ALEX1 is highly methylated in GC cells and tissues. CONCLUSIONS: ALEX1 expression is reduced in GC and is involved in diverse cellular functions. ALEX1 inhibits metastasis through the PAR-1/Rho GTPase signaling pathway.

Dual role of carcinoembryonic antigen-related cell adhesion molecule 6 expression in predicting the overall survival of gastric cancer patients.

Carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6) is a member of the glycosylphosphatidylinositol-linked immunoglobulin superfamily that is implicated in many human cancers. Here, we aimed to investigate the role of CEACAM6 expression in predicting the overall survival (OS) in gastric cancer (GC). The impact of CEACAM6 on the survival of patients with GC (n = 876) was assessed using an online Kaplan-Meier plotter. Findings were validated using the OS data of patients (n = 160) recruited from Ruijin Hospital. We found that high CEACAM6 expression was associated with a better OS in early-stage or well-differentiated GC, or who were treated without 5-fluorouracil (5-FU). Conversely, high CEACAM6 expression was associated with a poor OS in advanced-stage GC, poorly differentiated tumors, or who were treated with 5-FU. Furthermore, CEACAM6 may serve as a better marker for predicting OS in GC than CEA. In addition, CEACAM6 overexpression in GC cells increased apoptotic resistance to 5-FU. Moreover, CEACAM6 induced cluster of differentiation 4- and 8-positive lymphocytes were detected in early-stage GC. In conclusion, CEACAM6 plays a contradictory role in predicting the OS in GC. In early-stage GC, high CEACAM6 expression is associated with improved OS. However, in advanced-stage GC, high CEACAM6 expression is associated with a poor OS.

Luteolin suppresses angiogenesis and vasculogenic mimicry formation through inhibiting Notch1-VEGF signaling in gastric cancer.

Gastric cancer is a great threat to the health of the people worldwide and lacks effective therapeutic regimens. Luteolin is one of Chinese herbs and presents in many fruits and green plants. In our previous study, we observed that luteolin inhibited cell migration and promoted cell apoptosis in gastric cancer. In the present study, luteolin significantly inhibited tube formation of human umbilical vein endothelial cells (HUVECs) through decreasing cell migration and proliferation of HUVECs in a dose-dependent manner. Vasculogenic mimicry (VM) tubes formed by gastric cancer cells were also inhibited with luteolin treatment. To explore how luteolin inhibited tubes formation, ELISA assay for VEGF was performed. Both of the VEGF secretion from Hs-746T cells and HUVECs were significantly decreased subsequent to luteolin treatment. In addition, cell migration was increased with the interaction between gastric cancer cells and HUVECs in co-culture assays. However, the promoting effects were abolished subsequent to luteolin treatment. Furthermore, luteolin inhibited VEGF secretion through suppressing Notch1 expression in gastric cancer. Overexpression of Notch1 in gastric cancer cells partially rescued the effects on cell migration, proliferation, HUVECs tube formation, and VM formation induced by luteolin treatment. In conclusion, luteolin inhibits angiogenesis and VM formation in gastric cancer through suppressing VEGF secretion dependent on Notch1 expression.

Luteolin suppresses gastric cancer progression by reversing epithelial-mesenchymal transition via suppression of the Notch signaling pathway.

BACKGROUND: Gastric cancer (GC) is one of the most malignant tumors and the second leading cause of cancer-related deaths in the world. Luteolin, a flavonoid present in many fruits and green plants, suppresses cancer progression. The effects of luteolin on GC cells and their underlying mechanisms remain unclear. METHODS: Effects of luteolin on cell proliferation, migration, invasion, and apoptosis were examined in vitro and in vivo by cell counting kit-8 (CCK-8), transwell assays, and flow cytometry, respectively. Real-time reverse transcription polymerase chain reaction (RT-PCR) and Western blots were performed to evaluate Notch1 signaling and activation of epithelial-mesenchymal transition (EMT) in GC cells treated with or without luteolin. Immunohistochemistry was performed to examine proliferation and Notch1 expression in xenograft tumors. RESULTS: Luteolin significantly inhibited cell proliferation, invasion, and migration in a dose-dependent and time-dependent manner and promoted cell apoptosis. Luteolin reversed EMT by shrinking the cytoskeleton and by inducing the expression of epithelial biomarker E-cadherin and downregulating the mesenchymal biomarkers N-cadherin, vimentin and Snail. Furthermore, Notch1 signaling was inhibited by luteolin, and downregulation of Notch1 had similar effects as luteolin treatment on cell proliferation, migration, and apoptosis. In addition, luteolin suppressed tumor growth in vivo. A higher expression of Notch1 correlated with a poor overall survival and a poor time to first progression. Furthermore, co-immunoprecipitation analysis revealed that activated Notch1 and ß-catenin formed a complex and regulated cell proliferation, migration, and invasion. CONCLUSIONS: In this study, GC progression was inhibited by luteolin through suppressing Notch1 signaling and reversing EMT, suggesting that luteolin may serve as an effective anti-tumor drug in GC treatment.

Biglycan stimulates VEGF expression in endothelial cells by activating the TLR signaling pathway.

Biglycan (BGN) is an important component of the extracellular matrix (ECM) that is implicated in a variety of human cancers. In our previous study, we reported that BGN was overexpressed in gastric cancer (GC) tissues and promoted cancer metastasis. Moreover, the tubular formation capacity in HUVECs was promoted by stimulation with culture media from BGN-overexpressing GC cells, but the exact underlying mechanism is still unknown. The purpose of this study was to determine the role and molecular mechanism of BGN in VEGF expression in endothelial cells. We found that BGN stimulation of endothelial cells increased the interaction between NF-kB and the HIF-1α promoter, leading to enhanced promoter activity and increased HIF-1α mRNA levels, as well as augmented HIF-1 activity that resulted in VEGF expression. All of this was dependent on the interaction of BGN with its receptors, TLR2 and TLR4. Moreover, we found that BGN enhanced endothelial cell migration and proliferation, as well as tube formation, in a TLR signaling pathway-dependent manner. In addition, endothelial cell-derived VEGF in turn was found to act on GC cells and promotes their migration. The combined findings of our current and previous studies suggest that BGN secreted from GC cells into the tumor stroma promotes GC development, as well as its progression, potentially through the chronic activation of tumor angiogenesis.

REG4 promotes peritoneal metastasis of gastric cancer through GPR37.

Being the major reason of recurrence and death after surgery, peritoneal metastasis of gastric cancer dooms the prognosis of advanced gastric cancer patients. Regenerating islet-derived family, member 4 (REG4) is believed to promote peritoneal metastasis, however, its mechanism is still a moot point at present. In the present study, we show that high expression of REG4 correlates with advanced stage and poor survival prognosis for gastric cancer patients. REG4 overexpression significantly enhances peritoneal metastasis by increasing adhesion ability. Moreover, SP1 is proved to be a transcription factor of REG4 and induce REG4 expression upon TGF-alpha stimulation. Also, G protein-coupled receptor 37 (GPR37) is identified to be in the same complex of REG4, which mediates REG4's signal transduction and promotes peritoneal metastasis of gastric cancer cell. Interestingly, we also discover a positive feedback loop triggered by REG4, amplifying itself through EGFR transactivation, consisting of GPR37, ADAM17, TGF-alpha, EGFR, SP1 and REG4. In conclusion, REG4 promotes peritoneal metastasis of gastric cancer through GPR37 and triggers a positive feedback loop.

Helicobacter pylori CagA induces tumor suppressor gene hypermethylation by upregulating DNMT1 via AKT-NFκB pathway in gastric cancer development.

Methylation of CpG islands in tumor suppressor gene prompter is one of the most characteristic abnormalities in Helicobacter pylori (HP)-associated gastric carcinoma (GC). Here, we investigated the pathogenic and molecular mechanisms underlying hypermethylation of tumor suppressor genes in HP induced GC development. We found that tumor suppressor genes hypermethylation, represented by MGMT, positively correlated with CagA in clinical specimens, gastric tissues from HP infected C57 mice and GC cell lines transfected by CagA or treated by HP infection. CagA enhanced PDK1 and AKT interaction and increased AKT phosphorylation. The P-AKT subsequent activated NFκB, which then bound to DNMT1 promoter and increased its expression. Finally, the upregulated DNMT1 promoted tumor suppressor genes hypermethylation with MGMT as a representative. In conclusion, CagA increased tumor suppressor genes hypermethylation via stimulating DNMT1 expression through the AKT-NFκB pathway.

CEACAM6 promotes tumor angiogenesis and vasculogenic mimicry in gastric cancer via FAK signaling.

CEACAM6 is a member of glycosylphosphatidylinositol-linked immunoglobulin superfamily that is implicated in a variety of human cancers. In our previous study, we reported that CEACAM6 was overexpressed in gastric cancer tissues and promoted cancer metastasis. The purpose of this study is to determine the role of CEACAM6 in tumor angiogenesis and mimicry formation. We found that overexpressed CEACAM6 promoted tubule formation dependent on HUVEC cells and vasculogenic mimicry formation of gastric cancer cells; opposing results were achieved in CEACAM6-silenced groups. Moreover, we found that mosaic vessels formed by HUVEC cells and gastric cancer cells were observed in vitro by 3D-culture assay. Overexpressed CEACAM6 in gastric cancer cells promoted tumor growth, VEGF expression and vasculogenic mimicry structures formation in vivo. In accordance with these observations, we found that phosphorylation of FAK and phosphorylation of paxillin were up-regulated in CEACAM6-overexpressing gastric cancer cells, and FAK inhibitor Y15 could reduce tubule and vasculogenic mimicry formation. These findings suggest that CEACAM6 promotes tumor angiogenesis and vasculogenic mimicry formation via FAK signaling in gastric cancer and CEACAM6 may be a new target for cancer anti-vascular treatment.

CEACAM6 promotes gastric cancer invasion and metastasis by inducing epithelial-mesenchymal transition via PI3K/AKT signaling pathway.

Overexpressed CEACAM6 in tumor tissues plays important roles in invasion, metastasis and anoikis resistance in a variety of human cancers. We recently reported that CEACAM6 expression is upregulated in Gastric cancer (GC) tissues and promoted GC metastasis. Here, we report that CEACAM6 promotes peritoneal metastases in vivo and is negatively correlated with E-cadherin expression in GC tissues. Overexpressed CEACAM6 induced epithelial-mesenchymal transition (EMT) in GC, as measured by increases in the EMT markers N-cadherin, Vimentin and Slug while E-cadherin expression was decreased in CEACAM6-overexpressing GC cells; opposing results were observed in CEACAM6-silenced cells. Furthermore, E-cadherin expression was negatively correlated with depth of tumor invasion, lymph node metastasis and TNM stage in GC tissues. Additionally, CEACAM6 elevated matrix metalloproteinase-9 (MMP-9) activity in GC, and anti-MMP-9 antibody could reverse the increasing invasion and migration induced by CEACAM6. CEACAM6 also increased the levels of phosphorylated AKT, which is involved in the progression of a variety of human tumors. We further observed that LY294002, a PI3K inhibitor, could reverse CEACAM6-induced EMT via mesenchymal-epithelial transition. These findings suggest that CEACAM6 enhances invasion and metastasis in GC by promoting EMT via the PI3K/AKT signaling pathway.

Androgen receptor promotes gastric cancer cell migration and invasion via AKT-phosphorylation dependent upregulation of matrix metalloproteinase 9.

Androgen receptor (AR) plays an important role in many kinds of cancers. However, the molecular mechanisms of AR in gastric cancer (GC) are poorly characterized. Here, we investigated the role of AR in GC cell migration, invasion and metastatic potential. Our data showed that AR expression was positively correlated with lymph node metastasis and late TNM stages. These findings were accompanied by activation of AKT and upregulation of matrix metalloproteinase 9 (MMP9). AR overexpression induced increases in GC cell migration, invasion and proliferation in vitro and in vivo. These effects were attenuated by inhibition of AKT, AR and MMP9. AR overexpression upregulated MMP9 protein levels, whereas this effect was counteracted by AR siRNA. Inhibition of AKT by siRNA or an inhibitor (MK-2206 2HC) decreased AR protein expression in both stably transfected and parental SGC-7901 cells. Luciferase reporter and chromatin immunoprecipitation assays demonstrated that AR bound to the AR-binding sites of the MMP9 promoter. In summary, AR overexpression induced by AKT phosphorylation upregulated MMP9 by binding to its promoter region to promote gastric carcinogenesis. The AKT/AR/MMP9 pathway plays an important role in GC metastasis and may be a novel therapeutic target for GC treatment.

CEACAM6 promotes tumor migration, invasion, and metastasis in gastric cancer.

Carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6) shows increased expression in a wide variety of human cancers, and its over-expression is associated with enhanced migration, invasion, and in vivo metastasis. Here, we reported that CEACAM6 was up-regulated in gastric cancer (GC) cell lines and tumor tissues. Over-expression of CEACAM6 in MKN-45 and SGC-7901 GC cells promoted migration and invasion in vitro and metastasis in athymic mice, whereas migration and invasion of MKN-28 and SNU-16 GC cells were suppressed by knockdown of CEACAM6. We also observed that steroid receptor coactivator (C-SRC) phosphorylation was increased when CEACAM6 was over-expressed in SGC-7901 cells. Taken together, these results suggested that CEACAM6 functions as an oncoprotein in GC and may be an important metastatic biomarker and therapeutic target.