SOX9 is regulated by AURKA in response to Helicobacter pylori infection via EIF4E-mediated cap-dependent translation

Helicobacter pylori (H. pylori) infection is the main risk factor for gastric cancer. The SRY-Box Transcription Factor 9 (SOX9) serves as a marker of stomach stem cells. We detected strong associations between AURKA and SOX9 expression levels in gastric cancers. Utilizing in vitro and in vivo mouse models, we demonstrated that H. pylori infection induced elevated levels of both AURKA and SOX9 proteins. Notably, the SOX9 protein and transcription activity levels were dependent on AURKA expression. AURKA knockdown led to a reduction in the number and size of gastric gland organoids. Conditional knockout of AURKA in mice resulted in a decrease in SOX9 baseline level in AURKA-knockout gastric glands, accompanied by diminished SOX9 induction following H. pylori infection. We found an AURKA-dependent increase in EIF4E and cap-dependent translation with an AURKA-EIF4E-dependent increase in SOX9 polysomal RNA levels. Immunoprecipitation assays demonstrated binding of AURKA to EIF4E with a decrease in EIF4E ubiquitination. Immunohistochemistry analysis on tissue arrays revealed moderate to strong immunostaining of AURKA and SOX9 with a significant correlation in gastric cancer tissues. These findings elucidate the mechanistic role of AURKA in regulating SOX9 levels via cap-dependent translation in response to H. pylori infection in gastric tumorigenesis.

Fibroblast growth factor receptor-4 mediates activation of Nuclear Factor Erythroid 2-Related Factor-2 in gastric tumorigenesis

Helicobacter pylori (H. pylori) is the leading risk factor for gastric carcinogenesis. Fibroblast growth factor receptor 4 (FGFR4) is a member of transmembrane tyrosine kinase receptors that are activated in cancer. We investigated the role of FGFR4 in regulating the cellular response to H. pylori infection in gastric cancer. High levels of oxidative stress signature and FGFR4 expression were detected in gastric cancer samples. Gene set enrichment analysis (GSEA) demonstrated enrichment of NRF2 signature in samples with high FGFR4 levels. H. pylori infection induced reactive oxygen species (ROS) with a cellular response manifested by an increase in FGFR4 with accumulation and nuclear localization NRF2. Knocking down FGFR4 significantly reduced NRF2 protein and transcription activity levels, leading to higher levels of ROS and DNA damage following H. pylori infection. We confirmed the induction of FGFR4 and NRF2 levels using mouse models following infection with a mouse-adapted H. pyloristrain. Pharmacologic inhibition of FGFR4 using H3B-6527, or its knockdown, remarkably reduced the level of NRF2 with a reduction in the size and number of gastric cancer spheroids. Mechanistically, we detected binding between FGFR4 and P62 proteins, competing with NRF2-KEAP1 interaction, allowing NRF2 to escape KEAP1-dependent degradation with subsequent accumulation and translocation to the nucleus. These findings demonstrate a novel functional role of FGFR4 in cellular homeostasis via regulating the NRF2 levels in response to H. pylori infection in gastric carcinogenesis, calling for testing the therapeutic efficacy of FGFR4 inhibitors in gastric cancer models.

Reflux conditions induce E-cadherin cleavage and EMT via APE1 redox function in oesophageal adenocarcinoma

OBJECTIVE

Chronic gastro-oesophageal reflux disease, where acidic bile salts (ABS) reflux into the oesophagus, is the leading risk factor for oesophageal adenocarcinoma (EAC). We investigated the role of ABS in promoting epithelial-mesenchymal transition (EMT) in EAC.

DESIGN

RNA sequencing data and public databases were analysed for the EMT pathway enrichment and patients' relapse-free survival. Cell models, pL2-IL1β transgenic mice, deidentified EAC patients' derived xenografts (PDXs) and tissues were used to investigate EMT in EAC.

RESULTS

Analysis of public databases and RNA-sequencing data demonstrated significant enrichment and activation of EMT signalling in EAC. ABS induced multiple characteristics of the EMT process, such as downregulation of E-cadherin, upregulation of vimentin and activation of ß-catenin signalling and EMT-transcription factors. These were associated with morphological changes and enhancement of cell migration and invasion capabilities. Mechanistically, ABS induced E-cadherin cleavage via an MMP14-dependent proteolytic cascade. Apurinic/apyrimidinic endonuclease (APE1), also known as redox factor 1, is an essential multifunctional protein. APE1 silencing, or its redox-specific inhibitor (E3330), downregulated MMP14 and abrogated the ABS-induced EMT. APE1 and MMP14 coexpression levels were inversely correlated with E-cadherin expression in human EAC tissues and the squamocolumnar junctions of the L2-IL1ß transgenic mouse model of EAC. EAC patients with APE1high and EMThigh signatures had worse relapse-free survival than those with low levels. In addition, treatment of PDXs with E3330 restrained EMT characteristics and suppressed tumour invasion.

CONCLUSION

Reflux conditions promote EMT via APE1 redox-dependent E-cadherin cleavage. APE1-redox function inhibitors can have a therapeutic role in EAC.

Multivalent tyrosine kinase inhibition promotes T cell recruitment to immune-desert gastric cancers by restricting epithelial-mesenchymal transition via tumour-intrinsic IFN-γ signalling

OBJECTIVE

Gastric cancer (GC) ranks fifth in incidence and fourth for mortality worldwide. The response to immune checkpoint blockade (ICB) therapy in GC is heterogeneous due to tumour-intrinsic and acquired immunotherapy resistance. We developed an immunophenotype-based subtyping of human GC based on immune cells infiltration to develop a novel treatment option.

DESIGN

A algorithm was developed to reclassify GC into immune inflamed, excluded and desert subtypes. Bioinformatics, human and mouse GC cell lines, syngeneic murine gastric tumour model, and CTLA4 blockade were used to investigate the immunotherapeutic effects by restricting receptor tyrosine kinase (RTK) signalling in immune desert (ICB-resistant) type GC.

RESULTS

Our algorithm restratified subtypes of human GC in public databases and showed that immune desert-type and excluded-type tumours are ICB-resistant compared with immune-inflamed GC. Moreover, epithelial-mesenchymal transition (EMT) signalling was highly enriched in immune desert-type GC, and syngeneic murine tumours exhibiting mesenchymal-like, compared with epithelial-like, properties are T cell-excluded and resistant to CTLA4 blockade. Our analysis further identified a panel of RTKs as potential druggable targets in the immune desert-type GC. Dovitinib, an inhibitor of multiple RTKs, strikingly repressed EMT programming in mesenchymal-like immune desert syngeneic GC models. Dovitinib activated the tumour-intrinsic SNAI1/2-IFN-γ signalling axis and impeded the EMT programme, converting immune desert-type tumours to immune inflamed-type tumours, sensitising these mesenchymal-like 'cold' tumours to CTLA4 blockade.

CONCLUSION

Our findings identified potential druggable targets relevant to patient groups, especially for refractory immune desert-type/ 'cold' GC. Dovitinib, an RTK inhibitor, sensitised desert-type immune-cold GC to CTLA4 blockade by restricting EMT and recruiting T cells.

Smoking induces WEE1 expression to promote docetaxel resistance in esophageal adenocarcinoma

Esophageal adenocarcinoma (EAC) patients have poor clinical outcomes, with an overall 5-year survival rate of 20%. Smoking is a significant risk factor for EAC. The role of WEE1, a nuclear kinase that negatively regulates the cell cycle in normal conditions, in EAC tumorigenesis and drug resistance is not fully understood. Immunohistochemistry staining shows significant WEE1 overexpression in human EAC tissues. Nicotine, nicotine-derived nitrosamine ketone, or 2% cigarette smoke extract treatment induces WEE1 protein expression in EAC, detected by western blot and immunofluorescence staining. qRT-PCR and reporter assay indicates that smoking induces WEE1 expression through miR-195-5p downregulation in EAC. ATP-Glo cell viability and clonogenic assay confirmed that WEE1 inhibition sensitizes EAC cells to docetaxel treatment in vitro. A TE-10 smoking machine with EAC patient-derived xenograft mouse model demonstrated that smoking induces WEE1 protein expression and resistance to docetaxel in vivo. MK-1775 and docetaxel combined treatment improves EAC patient-derived xenograft mouse survival in vivo. Our findings demonstrate, for the first time, that smoking-induced WEE1 overexpression through miRNA dysregulation in EAC plays an essential role in EAC drug resistance. WEE1 inhibition is a promising therapeutic method to overcome drug resistance and target treatment refractory cancer cells.

Abstract 1232: Gastroesophageal reflux disease promotes E-cadherin cleavage and activates EMT via APE1-redox function in esophageal adenocarcinoma

The incidence of esophageal adenocarcinoma (EAC) has increased rapidly over the past four decades. Chronic gastroesophageal reflux disease (GERD), where acidic bile salts (ABS) abnormally refluxate into the esophagus, is the leading risk factor for the development of a metaplastic condition known as Barrett’s esophagus (BE) and its progression to EAC. We used 3D organotypic culture, mouse and human tissue samples to assess the role of ABS in Epithelial-to-Mesenchymal Transition (EMT) in EAC. Analysis of public databases revealed significant enrichment of EMT signaling in EAC progression. RNA-seq analysis of EAC cells showed activation of EMT pathway in response to ABS exposure. ABS induced multiple characteristics of the EMT process, such as downregulation of E-cadherin, upregulation of Vimentin, activation of ß-catenin and EMT-transcription factors (EMT-TFs), cell morphological changes, and enhancement of cell migration and invasion capabilities. Mechanistically, we discovered that ABS induced E-cadherin cleavage via MMP14 proteolytic cascade. APE1 silencing, or APE1-redox-specific inhibitor (E3330), abrogated the ABS-induced EMT process and signaling by downregulating MMP14. Furthermore, APE1 and MMP14 co-expression levels were inversely correlated with E-cadherin expression in gastroesophageal junctions of human EAC tissues, and the L2-IL1ß transgenic mouse model of BE/EAC. EAC patients with high APE1 and EMT signatures had worse relapse free survival than those with low signature. In a summary, this study demonstrates the role of ABS in promoting EMT via the redox-sensitive signaling axis of APE1/MMP14/E-cadherin/ß-catenin. Pharmacological inhibition of APE1-redox function could be a potential therapeutic approach to effectively reduce the risk of Barrett’s carcinogenesis.

Citation Format: Heng Lu, Longlong Cao, Farah Ballout, Abbes Belkhiri, Dunfa Peng, Lei Chen, Mohammed Soutto, Oliver McDonald, Alexander Zaika, Jianwen Que, Wael El-Rifai. Gastroesophageal reflux disease promotes E-cadherin cleavage and activates EMT via APE1-redox function in esophageal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1232.

Abstract 2592: Helicobacter pylori-induced FGFR4 mediates nuclear accumulation of NRF2 in gastric tumorigenesis

Background: Fibroblast growth factor receptor 4 (FGFR4) is a member of the transmembrane tyrosine kinase receptor family and has been linked to a variety of malignancies. NRF2 (Nuclear factor-erythroid 2-related factor) is a cytoprotective factor and a critical regulator in the antioxidant response pathway. In this study, we sought to uncover novel functions of FGFR4 and its role in regulating the antioxidant response in gastric carcinogenesis.

Methods and Results: Using western blot and immunofluorescence, H. pylori infection in gastric cancer cell lines demonstrated high levels of reactive oxygen species and induction of both FGFR4 and NRF2. Using Flow cytometry, FGFR4 silencing resulted in decrease of NRF2 with a significant spike in ROS levels and an increase in DNA damage and cell death. FGFR4 knockdown showed a significant decrease in NRF2 transcriptional activity as measured by NRF2 ARE luciferase reporter assay and resulted in reduced mRNA levels of HO-1 (Heme Oxygenase-1), which is a classical target of NRF2. These results were confirmed by immunofluorescence showing a significant increase of nuclear accumulation of NRF2 after H. pylori infection which was abolished after FGFR4 knockdown. Similar results were found using recombinant protein FGF19, a FGFR4 ligand. C57/B6 wild-type mice were infected with the pylori strain (PMSS1). An increase in FGFR4, NRF2, and HO-1 was seen by immunofluorescence, Western blot, and quantitative real-time PCR in H. pylori-infected mice vs control mice. We observed a reduction in NRF2 in our in vitro and in vivo models using H3B-6527, a specific FGFR4 inhibitor. We also discovered an association between an increase in FGFR4 and P62 protein expressions and NRF2 protein stability. We detected a significant increase in FGFR4, NRF2, and HO1 in dysplastic and neoplastic gastric lesions using the TFF1-KO mouse model which was further aggravated by H. pylori infection. In terms of the mechanism, utilizing proximity ligation and immunoprecipitation assays, we found that FGFR4 binds to P62 to inhibit the interaction between NRF2 and KEAP1, allowing NRF2 to avoid degradation facilitating its translocation and accumulation in the nucleus.

Conclusion: These findings revealed that FGFR4 has a unique functional role in promoting gastric carcinogenesis by mediating accumulation and activation of the NRF2 antioxidant response. The use of FGFR4 inhibitors is a viable treatment option that warrants further research in patients with gastric cancer.

Citation Format: Nadeem S. Bhat, Mohammed Soutto, Xing Zhang, Zheng Chen, Ahmed Gomaa, Marwah Al-Mathkour, Selma Maacha, Heng Lu, Dunfa Peng, Zekuan Xu, Wael El-Rifai. Helicobacter pylori-induced FGFR4 mediates nuclear accumulation of NRF2 in gastric tumorigenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2592.

Abstract 375: Smoking induces Wee1 expression through miRNA deregulation, promoting docetaxel resistance in esophageal adenocarcinoma

Esophageal Adenocarcinoma (EAC) is the most common subtype of Esophageal Cancer in Western countries, and its incidence rate has increased over the past few decades. The overall five-year survival rate of EAC is less than 20%. Smoking is a major risk factor for EAC development. WEE1 kinase plays a crucial role in the cell cycle by regulating the G2/M checkpoint, providing a time frame for the cells to repair DNA damage. Thus, targeting WEE1 using an inhibitor could potentiate the effect of chemotherapeutic drugs. This study investigated how smoking induces WEE1 protein expression, promoting docetaxel resistance in EAC.

IHC staining for WEE1 in the normal esophagus and EAC tissue sections revealed significant over-expression of WEE1 protein in EAC. Nicotine, Nicotine derived Nitrosamine Ketone (NNK), and 2% cigarette smoke extract (CSE) treatment induced WEE1 expression with a concomitant increase in CDC2 phosphorylation (p-CDC2, Y15), a well-established read-out of WEE1 activity in EAC cells. In addition, we found that smoking upregulates WEE1 expression by decreasing miR-195-5p expression levels in EAC.

Based on the differential gene expression signatures in EAC cell lines FLO1 and OE33 following WEE1 knockdown, drug and small molecule induced gene expression signatures analysis, L1000 fireworks display (L1000FWD), predicted that docetaxel is one of the best drug candidates which can synergize with the WEE1 inhibitor MK1775. Smoking-induced docetaxel resistance in EAC cells measured by cell viability assay. Down-regulating WEE1 expression with siRNA or pharmacological inhibition using MK1775 significantly sensitized EAC cells to docetaxel treatment, as evidenced by a remarkable decrease in the IC50 value of docetaxel. Inhibition of WEE1 combined with docetaxel can be considered an ideal therapeutic strategy due to its superior anti-tumor efficacy compared to the standard single-agent treatment. In conclusion, our data provide a firm rationale for the clinical combination of docetaxel with MK1775 in EAC patients.

Citation Format: Krishnapriya Thangaretnam, Islam MD Obaidul, Heng Lu, Dunfa Peng, Nadeem Sidiq Bhat, Mohammed Soutto, Zheng Chen. Smoking induces Wee1 expression through miRNA deregulation, promoting docetaxel resistance in esophageal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 375.

Abstract 5972: CDK1 bridges NF-kB and b-catenin signaling in response to H. pylori infection in gastric tumorigenesis

Background: Cell cycle dysregulation is a hallmark of cancer, resulting in unregulated cell proliferation and, eventually, tumor development. Cyclin-dependent kinase 1 (CDK1) is a cell cycle regulatory protein that is involved in cell cycle maintenance. CDK1 has been discovered to be substantially elevated in a several tumors and is linked to poor overall and relapse-free survival. The aim of this study is to understand the regulation role of Helicobacter Pylori infection and inflammation on CDK1 expression in gastric cancer.

Methods: Using TCGA data and our integrated comprehensive gene expression analysis, we found a significant overexpression of CDK1 in gastric cancer human and mouse tissues. We detected overexpression of CDK1 in human and mouse gastric glands in response to H. pylori infection. Our data demonstrated that H. pylori infection induced phosphorylation (S536) and activation of NF-kB in vitro and in vivo. Furthermore, H. pylori infection and TNF-α treatment increased the CDK1 mRNA and protein levels in gastric cancer cell lines. Using the ChIP assay, we detected direct biding of NF-κB on the CDK1 promoter regulating its transcription. CDK1 promoted activation of the β-catenin signaling pathway. Using the pTOP/pFOP luciferase reporter assays, as a measure of β-catenin/TCF transcription activity, we confirmed CDK1-dependent activation of β-catenin in response to H. pylori infection. Pharmacologic and genetic inhibition of CDK1 reversed these effects and decreased number and size of gastric tumors organoid from mouse and human.

Conclusion: Our findings demonstrate NF-kB-mediated induction of CDK1 expression in response to H. pylori infection with subsequent activation of tumorigenic β-catenin signaling. This novel regulatory link between infection, CDK1, and β-catenin suggests the importance of considering CDK1 inhibitors in gastric cancer.

Citation Format: Marwah M. Al-Mathkour, Shoumin Zhu, Longlong Cao, Shayan Khalafi, Zheng Chen, Julio Poveda, Dunfa Peng, Heng Lu, Mohammed Soutto, Tianling Hu, Oliver McDonalnd, Alexander Zaika, Wael El-Rifai. CDK1 bridges NF-kB and b-catenin signaling in response to H. pylori infection in gastric tumorigenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5972.

CDK1 bridges NF-κB and β-catenin signaling in response to H. pylori infection in gastric tumorigenesis

Infection with Helicobacter pylori (H. pylori) is the main risk factor for gastric cancer, a leading cause of cancer-related death worldwide. The oncogenic functions of cyclin-dependent kinase 1 (CDK1) are not fully understood in gastric tumorigenesis. Using public datasets, quantitative real-time PCR, western blot, and immunohistochemical (IHC) analyses, we detect high levels of CDK1 in human and mouse gastric tumors. H. pylori infection induces activation of nuclear factor κB (NF-κB) with a significant increase in CDK1 in in vitro and in vivo models (p < 0.01). We confirm active NF-κB binding sites on the CDK1 promoter sequence. CDK1 phosphorylates and inhibits GSK-3β activity through direct binding with subsequent accumulation and activation of β-catenin. CDK1 silencing or pharmacologic inhibition reverses these effects and impairs tumor organoids and spheroid formation. IHC analysis demonstrates a positive correlation between CDK1 and β-catenin. The results demonstrate a mechanistic link between infection, inflammation, and gastric tumorigenesis where CDK1 plays a critical role.

Induction of Fibroblast Growth Factor Receptor 4 by Helicobacter pylori via Signal Transducer and Activator of Transcription 3 With a Feedforward Activation Loop Involving SRC Signaling in Gastric Cancer

BACKGROUND & AIMS

Helicobacter pylori (H pylori) infection is the main risk factor for gastric cancer. The role of fibroblast growth factor receptors (FGRFs) in H pylori-mediated gastric tumorigenesis remains largely unknown. This study investigated the molecular and mechanistic links between H pylori, inflammation, and FGFR4 in gastric cancer.

METHODS

Cell lines, human and mouse gastric tissue samples, and gastric organoids models were implemented. Infection with H pylori was performed using in vitro and in vivo models. Western blot, real-time quantitative reverse-transcription polymerase chain reaction, flow cytometry, immunofluorescence, immunohistochemistry, chromatin immunoprecipitation, and luciferase reporter assays were used for molecular, mechanistic, and functional studies.

RESULTS

Analysis of FGFR family members using The Cancer Genome Atlas data, followed by validation, indicated that FGFR4 messenger (m)RNA was the most significantly overexpressed member in human gastric cancer tissue samples (P < .001). We also detected high levels of Fgfr4 mRNA and protein in gastric dysplasia and adenocarcinoma lesions in mouse models. Infection with J166, 7.13, and PMSS1 cytotoxin-associated gene A (CagA)+ H pylori strains induced FGFR4 mRNA and protein expression in in vitro and in vivo models. This was associated with a concordant activation of signal transducer and activator of transcription 3 (STAT3). Analysis of the FGFR4 promoter suggested several putative binding sites for STAT3. Using chromatin immunoprecipitation assay and an FGFR-promoter luciferase reporter containing putative STAT3 binding sites and their mutants, we confirmed a direct functional binding of STAT3 on the FGFR4 promoter. Mechanistically, we also discovered a feedforward activation loop between FGFR4 and STAT3 where the fibroblast growth factor 19–FGFR4 axis played an essential role in activating STAT3 in a SRC proto-oncogene non-receptor tyrosine kinase dependent manner. Functionally, we found that FGFR4 protected against H pylori-induced DNA damage and cell death.

CONCLUSIONS

Our findings demonstrated a link between infection, inflammation, and FGFR4 activation, where a feedforward activation loop between FGFR4 and STAT3 is established via SRC proto-oncogene non-receptor tyrosine kinase in response to H pylori infection. Given the relevance of FGFR4 to the etiology and biology of gastric cancer, we propose FGFR4 as a druggable molecular vulnerability that can be tested in patients with gastric cancer.

Abstract 5849: Activation of STAT3 is mediated by FGFR4 induction via SRC signaling after H. pylori infection

Background: Gastric cancer is considered the 5th most common form of cancer and 4th leading cause of cancer-related deaths worldwide. Due to the late stage of diagnosis, gastric cancer carries poor prognosis and poor overall survival. Infection with H. pylori is the strongest known risk factor. Fibroblast Growth Factor Receptor 4 (FGFR4) belongs to a family of highly conserved tyrosine kinases. This study investigated the molecular mechanism of FGFR4 regulation in response to H. pylori infection.

Methods and Results: Among all the FGFRs, FGFR4 mRNA expression level was the most significantly elevated in human gastric cancer samples as compared to normal samples, using Real-time qPCR. These results were confirmed using the TCGA and Geo database analysis, confirming that FGFR4 is highly expressed in gastric cancer. Using western blot, we found that FGFR4 is significantly expressed in dysplasia and adenocarcinoma lesions in the TFF1-KO gastric cancer mouse model. Following infection with H. pylori in in-vitro (J166, 7.13) and in-vivo (PMSS1) models, we detected a significant increase in the expression of FGFR4 at the protein and mRNA levels. We also detected activation of STAT3 in human gastric cell lines and mice gastric tissues. Furthermore, analysis of FGFR4 promoter revealed several putative binding sites for STAT3. To confirm that FGFR4 expression is dependent upon STAT3 activation, we performed ChIP assay and confirmed direct functional binding of STAT3 on FGFR4 promoter. Using the FGF19, the ligand for FGFR4, we found that FGF19-FGFR4 axis played a vital role in activating STAT3 through an SRC-dependent mechanism and discovered that there is a feedforward activation loop between FGFR4 and STAT3. Functionally, we found that FGFR4 protected against H. pylori-induced DNA damage and cell death.

Conclusion: Our study established a feedforward activation loop between FGFR4 and STAT3 in response to H. pylori infection and FGFR4 could be a possible druggable moiety for future therapies in gastric cancer.

Citation Format: Nadeem S. Bhat, Mohammed Soutto, Xing Zhang, Zheng Chen, Shoumin Zhu, Heng Lu, Dunfa Peng, Zekuan Xu, Wael El-Rifai. Activation of STAT3 is mediated by FGFR4 induction via SRC signaling after H. pylori infection [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5849.

Helicobacter pylori-induced RASAL2 Through Activation of Nuclear Factor-κB Promotes Gastric Tumorigenesis via β-catenin Signaling Axis

BACKGROUND & AIMS

Helicobacter pylori infection is the predominant risk factor for gastric cancer. RAS protein activator like 2 (RASAL2) is considered a double-edged sword in carcinogenesis. Herein, we investigated the role of RASAL2 in response to H pylori infection and gastric tumorigenesis.

METHODS

Bioinformatics analyses of local and public databases were applied to analyze RASAL2 expression, signaling pathways, and clinical significance. In vitro cell culture, spheroids, patient-derived organoids, and in vivo mouse models were used. Molecular assays included chromatin immunoprecipitation, co-immunoprecipitation, Western blotting, quantitative polymerase chain reaction, and immunocyto/histochemistry.

RESULTS

H pylori infection induced RASAL2 expression via a nuclear factor-κB (NF-κB)-dependent mechanism whereby NF-κB was directly bound to the RASAL2 promoter activating its transcription. By gene silencing and ectopic overexpression, we found that RASAL2 upregulated β-catenin transcriptional activity. RASAL2 inhibited protein phosphatase 2A activity through direct binding with subsequent activation of the AKT/β-catenin signaling axis. Functionally, RASAL2 silencing decreased nuclear β-catenin levels and impaired tumor spheroids and organoids formation. Furthermore, the depletion of RASAL2 impaired tumor growth in gastric tumor xenograft mouse models. Clinicopathological analysis indicated that abnormal overexpression of RASAL2 correlated with poor prognosis and chemoresistance in human gastric tumors.

CONCLUSIONS

These studies uncovered a novel signaling axis of NF-κB/RASAL2/β-catenin, providing a novel link between infection, inflammation and gastric tumorigenesis.

NF-kB-dependent activation of STAT3 by H. pylori is suppressed by TFF1

BACKGROUND

H. pylori infection is the main risk factor for gastric cancer. In this study, we investigated H. pylori-mediated activation of STAT3 and NF-κB in gastric cancer, using in vitro and in vivo models.

METHODS

To investigate the activation of NF-κB and STAT3 by H. pylori strains we used in vitro and in vivo mouse models, western blots, immunofluorescence, ChIP Assay, luciferase and quantitative real-time PCR assays.

RESULTS

Following infection with H. pylori in vitro, we found an earlier phosphorylation of NF-kB-p65 (S536), followed by STAT3 (Y705). Immunofluorescence, using in vitro and in vivo models, demonstrated nuclear localization of NF-kB and STAT3, following H. pylori infection. NF-kB and STAT3 luciferase reporter assays confirmed earlier activation of NF-kB followed by STAT3. In vitro and in vivo models demonstrated induction of mRNA expression of IL-6 (p < 0.001), VEGF-α (p < 0.05), IL-17 (p < 0.001), and IL-23 (p < 0.001). Using ChIP, we confirmed co-binding of both NF-kB-p65 and STAT3 on the IL6 promoter. The reconstitution of Trefoil Factor 1 (TFF1) suppressed activation of NF-kB with reduction in IL6 levels and STAT3 activity, in response to H. pylori infection. Using pharmacologic (BAY11-7082) and genetic (IκB super repressor (IκBSR)) inhibitors of NF-kB-p65, we confirmed the requirement of NF-kB-p65 for activation of STAT3, as measured by phosphorylation, transcription activity, and nuclear localization of STAT3 in in vitro and in vivo models.

CONCLUSION

Our findings suggest the presence of an early autocrine NF-kB-dependent activation of STAT3 in response to H. pylori infection. TFF1 acts as an anti-inflammatory guard against H. pylori-mediated activation of pro-inflammatory networks.

Silencing of miR490-3p by H. pylori activates DARPP-32 and induces resistance to gefitinib

Infection with Helicobacter pylori (H. pylori) is the main risk factor for gastric carcinogenesis. In this study, we investigated the expression, molecular functions, and downstream effectors of miR490-3p in gastric cancer. We used in vitro and in vivo models to investigate the role of H. pylori in regulating miR490-3p, DARPP-32-dependent functions, and therapeutic resistance. Human and mouse neoplastic gastric lesions demonstrated a negative correlation between DARPP-32 and miR490-3p expression (R = -0.58, P < 0.01). This was also detected following infection with H. pylori (R = -0.66, P < 0.01). Molecular assays confirmed DARPP-32 as a direct target of miR490-3p. CHRM2, the host gene of miR490-3p, was hypermethylated and downregulated in neoplastic gastric tissues (P < 0.05). H. pylori induced methylation and downregulation of CHRM2 and miR490-3p. Functionally, the reconstitution of miR490-3p sensitized cancer cells to gefitinib by inactivating DRAPP-32-dependent AKT and STAT3 pathways. Patients with low miR490-3p or high DARPP-32 expression had decreased overall survival (P < 0.05). Hypermethylation-mediated silencing of CHRM2 and miR490-3p by H. pylori increased DARPP-32 expression. Downregulation of miR490-3p in gastric cancer plays a role in gefitinib response by inducing DARPP-32-mediated activation of PI3K/AKT, STAT3 signaling pathways.

Epigenetic regulation of AURKA by miR-4715-3p in upper gastrointestinal cancers

Aurora kinase A (AURKA) is frequently overexpressed in several cancers. miRNA sequencing and bioinformatics analysis indicated significant downregulation of miR-4715-3p. We found that miR-4715-3p has putative binding sites on the 3UTR region of AURKA. Upper gastrointestinal adenocarcinoma (UGC) tissue samples and cell models demonstrated significant overexpression of AURKA with downregulation of miR-4715-3p. Luciferase reporter assays confirmed binding of miR-4715-3p on the 3UTR region of AURKA. miR-4715-3p mediated a reduction in AURKA levels leading to G2/M delay, chromosomal polyploidy, and cell death. We also detected a remarkable decrease in GPX4, an inhibitor of ferroptosis, with an increase in cleaved PARP and caspase-3. Inhibition of AURKA using siRNA produced similar results, suggesting a possible link between AURKA and GPX4. Analysis of UGC samples and cell models demonstrated increased methylation levels of several CpG nucleotides upstream of miR-4715-3p. 5-Aza-2'-deoxycytidine induced demethylation of several CpG nucleotides, restoring miR-4715-3p expression, leading to downregulation of AURKA. In conclusion, our data identified a novel epigenetic mechanism mediating silencing of miR-4715-3p and induction of AURKA in UGCs. Inhibition of AURKA or reconstitution of miR-4715-3p inhibited GPX4 and induced cell death, suggesting a link between AURKA and ferroptosis.

PRDX2 protects against oxidative stress induced by H. pylori and promotes resistance to cisplatin in gastric cancer

BACKGROUND

Helicobacter pylori (H. pylori) infection is the main risk factor for gastric cancer. The role of antioxidant enzyme peroxiredoxin 2 (PRDX2) in gastric tumorigenesis remains unknown. In vitro (AGS and SNU-1 cell lines) and in vivo mouse models were utilized to investigate the role of PRDX2 in response to H. pylori infection (7.13, J166 or PMSS1 strain). We detected high levels of PRDX2 expression in gastric cancer tissues. Gastric cancer patients with high expression levels of PRDX2 had significantly worse overall and progression-free survival than those with low levels. H. pylori infection induced activation of NF-κB with increased expression of PRDX2, in in vitro and in vivo models. The knockdown of PRDX2 led to an increase in the levels of reactive oxygen species (ROS), oxidative DNA damage, and double-strand DNA breaks, in response to H. pylori infection, as measured by H₂DCFDA, 8-oxoguanine, and p-H2AXγ assays. Luciferase reporter and ChIP assays confirmed the presence of a putative binding site of NF-κB-p65 on PRDX2 promoter region. The inhibition of PRDX2 significantly sensitized AGS and SNU-1 cells to cisplatin treatment. Our data suggest that the future development of therapeutic approaches targeting PRDX2 may be useful in the treatment of gastric cancer.

Activation of STAT3 signaling is mediated by TFF1 silencing in gastric neoplasia

TFF1, a secreted protein, plays an essential role in keeping the integrity of gastric mucosa and its barrier function. Loss of TFF1 expression in the TFF1-knockout (KO) mouse leads to a pro-inflammatory phenotype with a cascade of gastric lesions that include low-grade dysplasia, high-grade dysplasia, and adenocarcinomas. In this study, we demonstrate nuclear localization of p-STAT^Y705, with significant overexpression of several STAT3 target genes in gastric glands from the TFF1-KO mice. We also show frequent loss of TFF1 with nuclear localization of STAT3 in human gastric cancers. The reconstitution of TFF1 protein in human gastric cancer cells and 3D gastric glands organoids from TFF1-KO mice abrogates IL6-induced nuclear p-STAT3^Y705 expression. Reconstitution of TFF1 inhibits IL6-induced STAT3 transcription activity, suppressing expression of its target genes. TFF1 blocks IL6Rα-GP130 complex formation through interfering with binding of IL6 to its receptor IL6Rα. These findings demonstrate a functional role of TFF1 in suppressing gastric tumorigenesis by impeding the IL6-STAT3 pro-inflammatory signaling axis.

Trefoil factor 1 (TFF1) is a protein secreted by the gastric mucosa that protects against gastric tumourigenesis. Here, the authors show that TFF1 inhibits the oncogenic inflammatory response and IL-6-mediated STAT3 activation by interfering with the binding of IL6 to its receptor IL6Rα.

Abstract LB-328: Loss of TFF1 leads to activation of RAGE in mouse and human gastric tumorigenesis

Background: The receptor for advanced glycation end products (RAGE) is a central signaling molecule in the innate immune system and is highly expressed in various cancers including gastric cancer. RAGE is a pattern recognition receptor that binds to multiple ligands leading to its activation and onset of pro-inflammatory response. Trefoil factor 1 (TFF1) is a small secreted protein expressed in the gastrointestinal tract which plays a key role in protection of gastric mucosal membrane and provides protection from injury and damage, therefore acts as tumor suppressor gene. In this study we investigated the role of TFF1 in regulation and degradation of RAGE receptor in vivo and in vitro.

Material and Results: Using quantitative real-time PCR, we observed significant increase of RAGE expression in gastric tissue from Tff1 knockout from non-dysplastic lesion; this increase of expression of RAGE was more notable in dysplastic samples, as compared to normal tissues (p&lt;0.001). The Tff1-KO mice tissues with gastritis and low grade dysplasia (LGD) and high grade dysplasia (HGD) showed significantly progressive higher expression of RAGE, as compared to normal tissues (p&lt;0.001). Analysis of human tissue samples demonstrated significant overexpression of RAGE, as compared to normal gastric tissues (p=0.01). Furthermore, we analyzed paired tumor and normal samples, and we found a significant up-regulation of RAGE mRNA expression in tumors compared to their corresponding normal samples (p=0.01). We also detected an inverse relationship between TFF1 and RAGE levels in mouse and human tissue samples. We next determined the levels of RAGE ligands, S100A2 and A4. The results showed significant increase in expression levels of S100A2 and A4 in human and mouse neoplastic gastric lesions, as compared to normal tissue samples (P&lt;.01). To determine a causal relationship between TFF1 and RAGE, we used in vitro cell models. Using Western blot and RT-PCR analysis, the reconstitution of TFF1 in AGS cells showed a decrease in expression levels of RAGE, S100A2, and A4, as compared to control cells. Treatment of cancer cell lines (AGS, MKN28, and MKN45) with RAGE inhibitor Azeliragon led to significant reduction in cell viability with IC50 range AGS= 1.65µM, MKN28=1.22µM, MKN45= 1.37µM .

Conclusion: Our data demonstrate, for the first time, that high levels of RAGE and its ligands S100A2 and A4 are mechanistically related to TFF1 levels. RAGE inhibitors demonstrated a therapeutic efficacy in pre-clinical in vitro models. Additional in vitro and in vivo studies are planned to determine the functional, mechanistic and therapeutic outcomes of RAGE in gastric tumorigenesis.

Citation Format: Nadeem S. Bhat, Mohammed Soutto, Zheng Chen, Shoumin Zhu, Huma Naz, Ahmed Gomaa, Sen Wang, Barry I. Hudson, El-Rifai Wael. Loss of TFF1 leads to activation of RAGE in mouse and human gastric tumorigenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-328.

Activation of IGF1R by DARPP-32 promotes STAT3 signaling in gastric cancer cells

Dopamine and cAMP-regulated phosphoprotein, Mr 32000 (DARPP-32), is frequently overexpressed in early stages of gastric cancers. We utilized in vitro assays, 3D gastric gland organoid cultures, mouse models, and human tissue samples to investigate the biological and molecular impact of DARPP-32 on activation of IGF1R and STAT3 signaling and gastric tumorigenesis. DARPP-32 enhanced phosphorylation of IGF1R (Y1135), a step that was critical for STAT3 phosphorylation at Y705, nuclear localization, and transcription activation. By using proximity ligation and co-immunoprecipitation assays, we found that IGF1R and DARPP-32 co-existed in the same protein complex. Binding of DARPP-32 to IGF1R promoted IGF1R phosphorylation with subsequent activation of downstream SRC and STAT3. Analysis of gastric tissues from the TFF1 knockout (KO) mouse model of gastric neoplasia, demonstrated phosphorylation of STAT3 in the early stages of gastric tumorigenesis. By crossing the TFF1 KO mice with DARPP-32 (DP) knockout (KO) mice, that have normal stomach, we obtained double knockout (TFF1 KO/DP KO). The gastric mucosa from the double KO mice did not show phosphorylation of IGF1R or STAT3. In addition, the TFF1 KO/DP KO mice had a significant delay in developing neoplastic gastric lesions. Analysis of human gastric cancer tissue microarrays, showed high levels of DARPP-32 and positive immunostaining for nuclear STAT3 in cancer tissues, as compared to non-cancer histologically normal tissues. In summary, the DARPP-32-IGF1R signaling axis plays a key role in regulating the STAT3 signaling, a critical step in gastric tumorigenesis.

Abstract 885: Induction of PRDX2 by H. pylori reduces ROS and promotes cancer cell survival and resistance to cisplatin

Background & Aims: The antioxidant enzyme peroxiredoxin 2 (PRDX2) plays a critical role in regulating reactive oxygen species (ROS) levels in several diseases. Helicobacter pylori (H. pylori) infection is a well-known risk factor of gastric cancer. The role of PRDX2 in gastric tumorigenesis remains largely unknown. We investigated the molecular function and regulation of PRDX2 in response to infection with H. pylori and cisplatin treatment in gastric cancer cells.

Methods:Western blots (WB) and quantitative real-time PCR (qPCR) analysis were performed on AGS, SNU-1 and MKN28 gastric cancer cell lines to detect PRDX2 expression levels with or without H. pyloriinfection (7.13 or J166 strain). We evaluated the levels of ROS by H2DCFDA staining. WB analysis was used to determine oxidative DNA damage and double stranded DNA breaks by using antibodies against 8-Oxo-guanine and p-H2AX. WB and NF-κb luciferase reporter assay were performed to investigate the link between PRDX2 and NF-κb signaling. ATP-GLO cell titer analysis was utilized to determine cell viability.

Results:Our data indicated that PRDX2 mRNA and protein expression levels were induced byH. pyloriin AGS and SNU-1 cells. PRDX2 knockdown significantly increased ROS levels and 8-Oxoguanine staining followingH. pyloriinfection in both cells. These results were further confirmed by Western blot data showing that p-H2AX protein level was strongly induced in PRDX2 knockdown and H. pyloriinfected cells. Interestingly, Western blot data showed that TNF-αtreatment induced PRDX2 protein levels while Bay 11-7082 treatment decreased PRDX2 protein level in AGS and SNU-1 cells. At the same time, PRDX2 transient knockdown in both AGS and SNU-1 cells decreased p-P65 (S536) protein expression levels, nuclear localization of NF-κB-p65, and luciferase reporter activity (P&lt;0.05). We also found that inhibition of PRDX2 significantly sensitized AGS and SNU-1 cells to cisplatin treatment.

Conclusion:Our data indicates that knockdown of PRDX2 enhances ROS and DNA damage with H. pylori infection on gastric cancer cells after H. pylori infection and sensitizes gastric cancer cells to cisplatin treatment. Our results suggest a positive feedforward loop between PRDX2 and NF-kB to reduce ROS levels.

KEY WORDS: PRDX2,H. pylori, gastric cancer, reactive oxygen species, DNA damage, NF-κb

Citation Format: Sen Wang, Zheng Chen, Heng Lu, Shoumin Zhu, Dunfa Peng, Mohammed Soutto, Ahmed Gomma, Nadeem Bhat, Huma Naz, Zekuan Xu, Wael El-Rifai. Induction of PRDX2 by H. pylori reduces ROS and promotes cancer cell survival and resistance to cisplatin [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 885.

Integrated Analysis of Mouse and Human Gastric Neoplasms Identifies Conserved microRNA Networks in Gastric Carcinogenesis

BACKGROUND & AIMS

microRNAs (miRNAs) are small noncoding RNAs that bind to the 3' untranslated regions of mRNAs to promote their degradation or block their translation. Mice with disruption of the trefoil factor 1 gene (Tff1) develop gastric neoplasms. We studied these mice to identify conserved miRNA networks involved in gastric carcinogenesis.

METHODS

We performed next-generation miRNA sequencing analysis of normal gastric tissues (based on histology) from patients without evidence of gastric neoplasm (n = 64) and from TFF1-knockout mice (n = 22). We validated our findings using 270 normal gastric tissues (including 61 samples from patients without evidence of neoplastic lesions) and 234 gastric tumor tissues from 3 separate cohorts of patients and from mice. We performed molecular and functional assays using cell lines (MKN28, MKN45, STKM2, and AGS cells), gastric organoids, and mice with xenograft tumors.

RESULTS

We identified 117 miRNAs that were significantly deregulated in mouse and human gastric tumor tissues compared with nontumor tissues. We validated changes in levels of 6 miRNAs by quantitative real-time polymerase chain reaction analyses of neoplastic gastric tissues from mice (n = 39) and 3 independent patient cohorts (n = 332 patients total). We found levels of MIR135B-5p, MIR196B-5p, and MIR92A-5p to be increased in tumor tissues, whereas levels of MIR143-3p, MIR204-5p, and MIR133-3p were decreased in tumor tissues. Levels of MIR143-3p were reduced not only in gastric cancer tissues but also in normal tissues adjacent to tumors in humans and low-grade dysplasia in mice. Transgenic expression of MIR143-3p in gastric cancer cell lines reduced their proliferation and restored their sensitivity to cisplatin. AGS cells with stable transgenic expression of MIR143-3p grew more slowly as xenograft tumors in mice than control AGS cells; tumor growth from AGS cells that expressed MIR143-3p, but not control cells, was sensitive to cisplatin. We identified and validated bromodomain containing 2 (BRD2) as a direct target of MIR143-3p; increased levels of BRD2 in gastric tumors was associated with shorter survival times for patients.

CONCLUSIONS

In an analysis of miRNA profiles of gastric tumors from mice and human patients, we identified a conserved signature associated with the early stages of gastric tumorigenesis. Strategies to restore MIR143-3p or inhibit BRD2 might be developed for treatment of gastric cancer.

TFF1 antagonizes TIMP-1 mediated proliferative functions in gastric cancer

Tissue inhibitor matrix metalloproteinase-1 (TIMP1) is one of four identified members of the TIMP family. We evaluated the role of TIMP1 in gastric cancer using human and mouse tissues along with gastric organoids and in vitro cell models. Using quantitative real-time RT-PCR, we detected significant overexpression of TIMP1 in the human gastric cancer samples, as compared to normal stomach samples (P < 0.01). We also detected overexpression of Timp1 in neoplastic gastric lesions of the Tff1-knockout (KO) mice, as compared to normal stomach tissues. Reconstitution of TFF1 in human gastric cancer cell lines led to a significant decrease in the mRNA expression level of TIMP1 (P < 0.05). In vitro analysis demonstrated that TIMP1 mRNA expression is induced by TNF-α and activation of NF-κB whereas inhibition of NF-κB using BAY11-7082 led to inhibition of NF-κB and downregulation of TIMP1. Western blot analysis confirmed the decrease in TIMP1 protein level following reconstitution of TFF1. By using immunofluorescence, we showed nuclear localization of NF-κB and expression of TIMP1 in gastric organoids established from the Tff1-KO stomach where reconstitution of Tff1 using recombinant protein led to a notable reduction in the expression of both NF-κB and TIMP1. Using EDU assay, as a measure of proliferating cells, we found that TIMP1 promotes cellular proliferation whereas TFF1 reconstitution leads to a significant decrease in cellular proliferation (P < 0.05). In summary, our findings demonstrate overexpression of TIMP1 in mouse and human gastric cancers through NF-kB-dependent mechanism. We also show that TFF1 suppresses NF-κB and inhibits TIMP1-mediated proliferative potential in gastric cancer.

Exposure of Barrett's and esophageal adenocarcinoma cells to bile acids activates EGFR-STAT3 signaling axis via induction of APE1

The development of Barret’s esophagus (BE) and its progression to esophageal adenocarcinoma (EAC) is highly linked to exposure to acidic bile salts due to chronic gastroesophageal reflux disease (GERD). In this study, we investigated the role of Apurinic/apyrimidinic endonuclease 1 /redox effector factor-1 (APE-1/REF-1) in STAT3 activation in response to EAC. Our results indicate that APE1 is constitutively overexpressed in EAC whereas its expression is transiently induced in response to acidic bile salts in non-neoplastic BE. Using overexpression or shRNA knockdown of APE1, we found that APE1 is required for phosphorylation, nuclear localization, and transcription activation of STAT3. By using an APE1 redox-specific mutant (C65A) and APE1 redox inhibitor (E3330), we demonstrate that APE1 activates STAT3 in a redox-dependent manner. By using pharmacologic inhibitors and genetic knockdown systems, we found that EGFR is a required link between APE1 and STAT3. EGFR phosphorylation (Y1068) was directly associated with APE1 levels and redox function. Co-immunoprecipitation and proximity ligation assays indicated that APE-1 coexists and interacts with the EGFR-STAT3 protein complex. Consistent with these findings, we demonstrated a significant induction in mRNA expression levels of STAT3 target genes (IL-6, IL-17A, BCL-xL, Survivin and c-Myc) in BE and EAC cells, following acidic bile salts treatment. ChIP assays indicated that acidic bile salts treatment enhances binding of STAT3 to the promoter of its target genes, Survivin and BCL-xL. Inhibition of APE1/REF-1 redox activity using E3330 abrogated STAT3 DNA binding and transcriptional activity. The induction of APE-1 - STAT3 axis in acidic bile salts conditions provided a survival advantage and promoted cellular proliferation. In summary, our study provides multiple pieces of evidence supporting a critical role for APE1 induction in activating the EGFR-STAT3 signaling axis in response to acidic bile salts, the main risk factors for Barrett’s carcinogenesis.

Helicobacter pylori-induced miR-135b-5p promotes cisplatin resistance in gastric cancer

Helicobacter pylori infection is a major risk factor for the development of gastric cancer. Aberrant expression of microRNAs is strongly implicated in gastric tumorigenesis; however, their contribution in response to H. pylori infection has not been fully elucidated. In this study, we evaluated the expression of miR-135b-5p and its role in gastric cancer. We describe the overexpression of miR-135b-5p in human gastric cancer tissue samples compared with normal tissue samples. Furthermore, we found that miR-135b-5p is also up-regulated in gastric tumors from the trefoil factor 1-knockout mouse model. Infection with H. pylori induced the expression of miR-135b-5p in the in vitro and in vivo models. miR-135b-5p induction was mediated by NF-κB. Treatment of gastric cancer cells with TNF-α induced miR-135b-5p in a NF-κB-dependent manner. Mechanistically, we found that miR-135b-5p targets Krüppel-like factor 4 (KLF4) and binds to its 3' UTR, leading to reduced KLF4 expression. Functionally, high levels of miR-135b-5p suppress apoptosis and induce cisplatin resistance. Our results uncovered a mechanistic link between H. pylori infection and miR-135b-5p-KLF4, suggesting that targeting miR-135b-5p could be a potential therapeutic approach to circumvent resistance to cisplatin.-Shao, L., Chen, Z., Soutto, M., Zhu, S., Lu, H., Romero-Gallo, J., Peek, R., Zhang, S., El-Rifai, W. Helicobacter pylori-induced miR-135b-5p promotes cisplatin resistance in gastric cancer.

Abstract 5447: Overexpression of DARPP-32 promotes activation of STAT3 through IGF1R-SRC axis in gastric cancer

Background: Dopamine and cAMP-regulated phosphoprotein, Mr 32000 (DARPP-32), is a novel cancer gene overexpressed in 2/3 of gastric cancer patients. DARPP-32 promotes cancer cell survival, drug resistance, and invasion. Activation of STAT3, signal transducer and activator of transcription 3, is important for tumorigenesis and drug resistance. Among factors that regulate STAT3, SOCS3 acts as a negative regulator of STAT3 to prevent its uncontrolled oncogenic activation. In this study, we aimed to investigate if DARPP-32 regulates STAT3 and determine the underlying molecular mechanisms.

Methods: The mRNA and protein levels were evaluated by quantitative real-time PCR and Western blot analysis. The association between DARPP-32 and STAT3 was evaluated by immunofluorescence. SOCS3 degradation was analyzed by Ubiquitination Assay. The interaction between DARPP-32 and IGF1R was evaluated by co-immunoprecipitation assays. Luciferase reporter and immunohistochemistry stain were used in this study.

Results: Overexpression of DARPP-32 in AGS gastric cancer cells increased phosphorylation of STAT3 (Y705) and activation of STAT3 luciferase reporter (P&lt;0.01), and decreased SOCS3 protein expression. DARPP-32 expression increased phosphorylation and ubiquitination of the SOCS3 protein, and subsequently shortened the SOCS3 protein half-life. We provide evidence showing that DARPP-32 promotes activation of IGF1R-SRC axis, critical for phosphorylation and degradation of SOCS3, a negative regulator of STAT3 activity. Proximity ligation and co-immunoprecipitation assays indicated that DARPP-32 and IGF1R co-exist in the same protein complex where DARPP-32 binding to IGF1R promotes its phosphorylation with activation of downstream SRC and STAT3. We obtained double knockouts mice (Darpp32KO/Tff1KO) to determine the histological changes at 3 age groups (3, 6, 9- 12 month). Using the different age groups, we found that the double knockout mouse model have significantly lower incidence of LGD at the age of 3 month, as compared to TFF1 KO (P&lt;0.05) mice. The Darpp32KO/Tff1KO gastric mucosa demonstrated lack of phosphorylation and nuclear localization of STAT3 with significant delay in the onset of tumor lesions. Immunohistochemistry analysis confirmed overexpression of DARPP-32 and nuclear localization of STAT3 in human gastric cancers.

Conclusion: The in vitro studies indicate that DARPP-32 plays a critical role in activation of STAT3 signaling through regulation of IGF1R and SRC, leading to SOCS3 degradation. In vivo results suggest that lack of DARPP-32 delays the development of tumors in the TFF1 knockout mouse model but is not sufficient alone to abrogate the full carcinogenesis cascade. These novel findings add to the oncogenic functions of DARPP-32 and highlight its potential role in the pro-inflammatory gastric carcinogenesis cascade.

Citation Format: Shoumin Zhu, Mohammed Soutto, Zheng Chen, Wael El-Rifai. Overexpression of DARPP-32 promotes activation of STAT3 through IGF1R-SRC axis in gastric cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5447.

Methylation of the HOXA10 Promoter Directs miR-196b-5p-Dependent Cell Proliferation and Invasion of Gastric Cancer Cells

The cross-talk between epigenetics and miRNA expression plays an important role in human tumorigenesis. Herein, the regulation and role of miR-196b-5p in gastric cancer was investigated. qRT-PCR demonstrated that miR-196b-5p is significantly overexpressed in human gastric cancer tissues (P < 0.01). In addition, it was determined that HOXA10, a homeobox family member and host gene for miR-196b-5p, is overexpressed and positively correlated with miR-196b-5p expression levels (P < 0.001). Quantitative pyrosequencing methylation analysis demonstrated significantly lower levels of DNA methylation at the HOXA10 promoter in gastric cancer, as compared with nonneoplastic gastric mucosa specimens. 5-Aza-2'-deoxycytidine treatment confirmed that demethylation of HOXA10 promoter induces the expression of HOXA10 and miR-196b-5p in gastric cancer cell model systems. Using the Tff1 knockout mouse model of gastric neoplasia, hypomethylation and overexpression of HOXA10 and miR-196b-5p in gastric tumors was observed, as compared with normal gastric mucosa from Tff1 wild-type mice. Mechanistically, reconstitution of TFF1 in human gastric cancer cells led to an increased HOXA10 promoter methylation with reduced expression of HOXA10 and miR-196b-5p. Functionally, miR-196b-5p reconstitution promoted human gastric cancer cell proliferation and invasion in vitro In summary, the current data demonstrate overexpression of miR-196b-5p in gastric cancer and suggest that TFF1 plays an important role in suppressing the expression of miR-196b-5p by mediating DNA methylation of the HOXA10 promoter. Loss of TFF1 expression may promote proliferation and invasion of gastric cancer cells through induction of promoter hypomethylation and expression of the HOXA10/miR-196b-5p axis.Implications: This study indicates that loss of TFF1 promotes the aberrant overexpression of HOXA10 and miR-196b-5p by demethylation of the HOXA10 promoter, which provides a new perspective of TFF1/HOXA10/miR-196b-5p functions in human gastric cancer. Mol Cancer Res; 16(4); 696-706. ©2018 AACR.

Loss of Tff1 Promotes Pro-Inflammatory Phenotype with Increase in the Levels of RORγt+ T Lymphocytes and Il-17 in Mouse Gastric Neoplasia

Background: TFF1 deficiency induces a mucosal pro-inflammatory phenotype that contributes to gastric tumorigenesis in mouse and human. Methods: We utilized the Tff1-KO mouse model to assess the impact of TFF1 loss on immune cells infiltration in the stomach. We used single cell suspension, flow cytometry, immunohistochemistry, and quantitative PCR (qPCR) assays. Results: The Tff1-KO gastric mucosa demonstrated high chronic inflammatory scores (score: 3-4) at age 2 months, which exacerbated at age 8 months (score: 4-6). We next used single-cell suspensions for flow cytometry analysis of total leukocytes (CD45+ cells), total T lymphocytes (CD45+CD3+cells), T cell subsets (CD4+, CD8+, and CD3+CD4-CD8-cells), and monocytes/macrophages (CD45+F4/80+cells). The results demonstrated an age-dependent (2 → 8 month age) significant increase of leukocytes (p<0.05), T cells (p<0.05), and monocytes/macrophages (p<0.001) in the gastric mucosa of the Tff1-KO mice, as compared to Tff1-WT. A similar increase was observed in blood samples (p<0.05). Using ionomycin to activate CD4⁺ splenocytes, the results indicated that Tff1-KO CD4⁺ splenocytes secreted higher levels of IL-17A (p<0.05 at 2 and p<0.001 at 8 months) and IL-17F (p<0.05 at 2 and 8 months) than Tff1-WT splenocytes. Conversely, Tff1-KO CD8⁺-cells secreted less IL-17F, but comparable levels of IL-17A. In addition, we detected a significant upregulation of Il-17 mRNA expression in gastric tissues in the Tff1-KO, as compared to Tff1-WT (p<0.001). Conclusions: The results identify TFF1 loss as a major pro-inflammatory step that modulates the tumor microenvironment and immune cell infiltration in the stomach. Furthermore, the data suggest that the increase of IL-17A and IL-17F in Th17 cells, derived from CD4⁺ T cells, reflects the chronic inflammation in gastric mucosa, whereas the absence of change of IL-17A and decrease of IL-17F in CD8⁺Tc17 cells suggest loss of cytotoxic function of CD8⁺Tc17 cells during gastric tumorigenesis of the Tff1-KO mice.

Helicobacter pylori-induced cell death is counteracted by NF-κB-mediated transcription of DARPP-32

OBJECTIVE

DARPP-32 is a frequently amplified and overexpressed gene that promotes several oncogenic functions in gastric cancer. Herein, we investigated the relationship between Helicobacter pylori infection, proinflammatory NF-κB activation and regulation of DARPP-32.

DESIGN

The study used in vivo and in vitro experiments. Luciferase reporter, quantitative real-time PCR, immunoblot, chromatin immunoprecipitation (ChIP), cell viability, H. pylori infection, tissue microarrays and immunohistochemical assays were used.

RESULTS

Our results indicated that H. pylori infection increased the DARPP-32 mRNA and protein levels in gastric cancer cell lines and gastric mucosa of mice. H. pylori infection increased the activity of NF-κB reporter and p-NF-κB (S536) protein level in vitro and in vivo. To investigate the transcriptional regulation of DARPP-32, we cloned a 3019 bp of the DARPP-32 promoter into the luciferase reporter (pGL3-Luc). Both H. pylori infection and tumour necrosis factor-α treatment induced DARPP-32 reporter activity (p<0.01). Using deletion constructs of DARPP-32 promoter and ChIP assay, we demonstrated that the sequence -996 to -1008 bp containing putative NF-κB-binding sites is the most active region. The induction of DARPP-32 expression by H. pylori infection counteracted H. pylori-induced cell death through activation of serine/threonine-specific protein kinase (AKT), as determined by ATP-Glo and clonogenic survival assays. Immunohistochemistry analysis demonstrated a significant positive correlation between NF-κB and DARPP-32 expression levels in gastric cancer tissues (r²=0.43, p<0.01).

CONCLUSIONS

Given the high frequency of DARPP-32 overexpression and its prosurvival oncogenic functions, the induction of DARPP-32 expression following H. pylori infection and activation of NF-κB provides a link between infection, inflammation and gastric tumourigenesis.

Integrated expression analysis identifies transcription networks in mouse and human gastric neoplasia

Gastric cancer (GC) is a leading cause of cancer-related deaths worldwide. The Tff1 knockout (KO) mouse model develops gastric lesions that include low-grade dysplasia (LGD), high-grade dysplasia (HGD), and adenocarcinomas. In this study, we used Affymetrix microarrays gene expression platforms for analysis of molecular signatures in the mouse stomach [Tff1-KO (LGD) and Tff1 wild-type (normal)] and human gastric cancer tissues and their adjacent normal tissue samples. Combined integrated bioinformatics analysis of mouse and human datasets indicated that 172 genes were consistently deregulated in both human gastric cancer samples and Tff1-KO LGD lesions (P < .05). Using Ingenuity pathway analysis, these genes mapped to important transcription networks that include MYC, STAT3, β-catenin, RELA, NFATC2, HIF1A, and ETS1 in both human and mouse. Further analysis demonstrated activation of FOXM1 and inhibition of TP53 transcription networks in human gastric cancers but not in Tff1-KO LGD lesions. Using real-time RT-PCR, we validated the deregulated expression of several genes (VCAM1, BGN, CLDN2, COL1A1, COL1A2, COL3A1, EpCAM, IFITM1, MMP9, MMP12, MMP14, PDGFRB, PLAU, and TIMP1) that map to altered transcription networks in both mouse and human gastric neoplasia. Our study demonstrates significant similarities in deregulated transcription networks in human gastric cancer and gastric tumorigenesis in the Tff1-KO mouse model. The data also suggest that activation of MYC, STAT3, RELA, and β-catenin transcription networks could be an early molecular step in gastric carcinogenesis.

Gastric tumour-derived ANGPT2 regulation by DARPP-32 promotes angiogenesis

OBJECTIVE

Overexpression of dopamine and cAMP-regulated phosphoprotein, Mr 32000 (DARPP-32), and its truncated isoform (t-DARPP) are associated with gastric tumorigenesis. Herein, we investigated the role of DARPP-32 proteins in regulating angiopoietin 2 (ANGPT2) and promoting tumour angiogenesis.

DESIGN

Quantitative real-time RT-PCR, immunoblotting, luciferase reporter, immunofluorescence, immunohistochemistry and angiogenesis assays were applied to investigate the regulation of angiogenesis by DARPP-32 proteins.

RESULTS

Overexpression of DARPP-32 significantly increased the mRNA and protein levels of ANGPT2 in gastric cancer cells. The overexpression of DARPP-32 T34A mutant or the N-terminal truncated isoform, t-DARPP, led to similar effects ruling out the T34-dependent regulation of protein phosphatase 1 activity in regulating ANGPT2. DARPP-32 proteins induced a secreted form of ANGPT2, which was detectable in the media, functionally active, and able to induce angiogenesis, measured by the human umbilical vein endothelial cells tube formation assay. Antibody blocking of the secreted ANGPT2 abrogated its function. To identify the mechanism by which DARPP-32 regulates ANGPT2, we examined the activities of NF-κB and signal transducer and activator of transcription 3 (STAT3), known regulators of angiogenesis. The results ruled out NF-κB and showed induction of STAT3 phosphorylation, activation and nuclear localisation. Inhibition or knockdown of STAT3 significantly attenuated the induction of ANGPT2 by DARPP-32 proteins. In vivo xenograft models demonstrated that overexpression of DARPP-32 promotes angiogenesis and tumour growth. Analyses of human gastric cancer tissues showed a strong correlation between DARPP-32 and ANGPT2.

CONCLUSIONS

Our novel findings establish the role of DARPP-32-STAT3 axis in regulating ANGPT2 in cancer cells to promote angiogenesis and tumorigenesis.

Loss of TFF1 promotes Helicobacter pylori-induced β-catenin activation and gastric tumorigenesis

Using in vitro and in vivo models, we investigated the role of TFF1 in suppressing H. pylori-mediated activation of oncogenic β-catenin in gastric tumorigenesis. A reconstitution of TFF1 expression in gastric cancer cells decreased H. pylori-induced β-catenin nuclear translocation, as compared to control (p < 0.001). These cells exhibited significantly lower β-catenin transcriptional activity, measured by pTopFlash reporter, and induction of its target genes (CCND1 and c-MYC), as compared to control. Because of the role of AKT in regulating β-catenin, we performed Western blot analysis and demonstrated that TFF1 reconstitution abrogates H. pylori-induced p-AKT (Ser473), p-β-catenin (Ser552), c-MYC, and CCND1 protein levels. For in vivo validation, we utilized the Tff1-KO gastric neoplasm mouse model. Following infection with PMSS1 H. pylori strain, we detected an increase in the nuclear staining for β-catenin and Ki-67 with a significant induction in the levels of Ccnd1 and c-Myc in the stomach of the Tff1-KO, as compared to Tff1-WT mice (p < 0.05). Only 10% of uninfected Tff1-KO mice, as opposed to one-third of H. pylori-infected Tff1-KO mice, developed invasive adenocarcinoma (p = 0.03). These findings suggest that loss of TFF1 could be a critical step in promoting the H. pylori-mediated oncogenic activation of β-catenin and gastric tumorigenesis.

Trefoil factor 1 expression suppresses Helicobacter pylori-induced inflammation in gastric carcinogenesis

BACKGROUND

Infection with Helicobacter pylori, a high-risk factor for gastric cancer, is frequently associated with chronic inflammation through activation of nuclear factor κB (NF-κB). Trefoil factor 1 (TFF1) is a constitutively expressed protein in the stomach that has tumor-suppressor functions and plays a critical role in maintaining mucosal integrity. This study investigated the role of TFF1 in regulating the proinflammatory response to H. pylori infections.

METHODS

For in vitro studies, immunofluorescence, luciferase reporter assays, Western blots, and quantitative real-time polymerase chain reaction were performed to investigate the activation of NF-κB and its target genes in response to infections with H. pylori strains J166 and 7.13. In addition, Tff1-knockout (KO) and Tff1-wild-type mice were used for infections with the H. pylori strain called premouse Sydney strain 1.

RESULTS

The reconstitution of TFF1 expression in gastric cancer cells significantly suppressed H. pylori-mediated increases in NF-κB-p65 nuclear staining, transcriptional activity, and expression of proinflammatory cytokine genes (tumor necrosis factor α, interleukin 1β, chemokine [C-X-C motif] ligand 5, and interleukin 4 receptor) that were associated with reductions in the expression and phosphorylation of NF-κB-p65 and IκB kinase α/β proteins. The in vivo studies using the Tff1-KO mouse model of gastric neoplasia confirmed the in vitro findings. Furthermore, they demonstrated increases in chronic inflammation scores and in the frequency of invasive gastric adenocarcinoma in the Tff1-KO mice infected with H. pylori versus the uninfected Tff1-KO mice.

CONCLUSIONS

These findings underscore an important protective role of TFF1 in abrogating H. pylori-mediated inflammation, a crucial hallmark of gastric tumorigenesis. Therefore, loss of TFF1 expression could be an important step in H. pylori-mediated gastric carcinogenesis.

Activation of β-catenin signalling by TFF1 loss promotes cell proliferation and gastric tumorigenesis

OBJECTIVE

In this study, we investigated the role of Trefoil factor 1 (TFF1) in regulating cell proliferation and tumour development through β-catenin signalling using in vivo and in vitro models of gastric tumorigenesis.

DESIGN

Tff1-knockout (Tff1-KO) mice, immunohistochemistry, luciferase reporter, qRT-PCR, immunoblot, and phosphatase assays were used to examine the role of TFF1 on β-catenin signalling pathway.

RESULTS

Nuclear localisation of β-catenin with transcriptional upregulation of its target genes, c-Myc and Ccnd1, was detected in hyperplastic tissue at an early age of 4-6 weeks and maintained during all stages of gastric tumorigenesis in the Tff1-KO mice. The reconstitution of TFF1 or TFF1 conditioned media significantly inhibited the β-catenin/T-cell factor (TCF) transcription activity in MKN28 gastric cancer cells. In agreement with these results, we detected a reduction in the levels of nuclear β-catenin with downregulation of c-MYC and CCND1 mRNA. Analysis of signalling molecules upstream of β-catenin revealed a decrease in phosphorylated glycogen synthase kinase 3β (p-GSK3β) (Ser9) and p-AKT (Ser473) protein levels following the reconstitution of TFF1 expression; this was consistent with the increase of p-β-catenin (Ser33/37/Thr41) and decrease of p-β-catenin (Ser552). This TFF1-induced reduction in phosphorylation of GSK3β, and AKT was dependent on protein phosphatase 2A (PP2A) activity. The treatment with okadaic acid or knockdown of PP2A abrogated these effects. Consistent with the mouse data, we observed loss of TFF1 and an increase in nuclear localisation of β-catenin in stages of human gastric tumorigenesis.

CONCLUSIONS

Our data indicate that loss of TFF1 promotes β-catenin activation and gastric tumorigenesis through regulation of PP2A, a major regulator of AKT-GSK3β signalling.

TFF1 activates p53 through down-regulation of miR-504 in gastric cancer

The expression of TFF1 is frequently down-regulated in human gastric cancer whereas its knockout leads to the development of gastric adenomas and carcinomas in mouse models. The molecular mechanisms underlying the TFF1 tumor suppressor functions remain unclear. In this study, we demonstrate, using colony formation assay and Annexin V staining, that reconstitution of TFF1 expression in gastric cancer cell models suppresses cell growth and promotes cell death. Furthermore, using a tumor xenograft mouse model of gastric cancer, we demonstrated that reconstitution of TFF1 suppresses tumor growth in vivo. The results from PG13-luciferase reporter assay and Western blot analysis indicated that TFF1 promotes the expression and transcription activity of the p53 protein. Further analysis using cycloheximide-based protein assay and quantitative real-time PCR data suggested that TFF1 does not interfere with p53 mRNA levels or protein stability. Alternatively, we found that the reconstitution of TFF1 down-regulates miR-504, a negative regulator of p53. Western blot analysis data demonstrated that miR-504 abrogates TFF1-induced p53 protein expression and activity. In conclusion, the in vitro and in vivo data demonstrate, for the first time, a novel mechanism by which the tumor suppressor functions of TFF1 involve activation of p53 through down-regulation of miR-504.

Glutathione Peroxidase 7 Suppresses Bile Salt-Induced Expression of Pro-Inflammatory Cytokines in Barrett's Carcinogenesis

Esophageal adenocarcinoma (EAC) is the most frequent malignancy in the esophagus in the US and its incidence has been rising rapidly in the past few decades. Chronic gastroesophageal reflux disease (GERD), where the esophageal epithelium is abnormally exposed to acid and bile salts, is a pro-inflammatory condition that is the main risk factor for the development of Barrett's esophagus (BE) and its progression to EAC. Glutathione peroxidase 7 (GPX7) is frequently silenced through DNA hypermethylation during Barrett's tumorigenesis. In this study, we investigated the role of GPX7 in regulating the bile salts-induced inflammatory signaling in Barrett's carcinogenesis. Using quantitative real-time PCR (qRT-PCR), we demonstrated a significant induction in the expression levels of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6, and IL-8) and chemokines (CXCL-1 and CXCL-2) in esophageal cells after exposure to acidic (pH4) or neutral (pH7) bile salts. Western blot analysis showed that exposure to acidic and neutral bile salts increased p-NF-κB-p65 (S536) protein levels independent of ROS. Reconstitution of GPX7 expression in EAC cells abolished the increase of p-p65 (S536) protein levels and mRNA expression of cytokines and chemokines upon treatment with acidic and neutral bile salts. Examination of human primary EAC tissues by qRT-PCR demonstrated significant overexpression of cytokines (TNF-α, IL-1β and IL-8) in EAC samples, as compared to normal samples, with significant inverse correlation with GPX7 expression level. Taken together, the loss of GPX7 expression promotes bile salt-induced activation of pro-inflammatory cytokines and chemokines; important contributors to GERD-associated Barrett's carcinogenesis.

AURKA regulates JAK2-STAT3 activity in human gastric and esophageal cancers

Aurora kinase A is a frequently amplified and overexpressed gene in upper gastrointestinal adenocarcinomas (UGCs). Using in vitro cell models of UGCs, we investigated whether AURKA can regulate Signal Transducer and Activator of Transcription 3 (STAT3). Our data indicate that overexpression of AURKA in FLO-1 and AGS cells increase STAT3 phosphorylation at the Tyr705 site, whereas AURKA genetic depletion by siRNA results in decreased phosphorylation levels of STAT3 in FLO-1 and MKN45 cells. Immunofluorescence analysis showed that AURKA overexpression enhanced STAT3 nuclear translocation while AURKA genetic knockdown reduced the nuclear translocation of STAT3 in AGS and FLO-1 cells, respectively. Using a luciferase reporter assay, we demonstrated that AURKA expression induces transcriptional activity of STAT3. Pharmacological inhibition of AURKA by MLN8237 reduced STAT3 phosphorylation along with down-regulation of STAT3 pro-survival targets, BCL2 and MCL1. Moreover, by using clonogenic cells survival assay, we showed that MLN8237 single dose treatment reduced the ability of FLO-1 and AGS cells to form colonies. Additional experiments utilizing cell models of overexpression and knockdown of AURKA indicated that STAT3 upstream non-receptor tyrosine kinase Janus kinase 2 (JAK2) is mediating the effect of AURKA on STAT3. The inhibition of JAK2 using JAK2-specific inhibitor AZD1480 or siRNA knockdown, in presence of AURKA overexpression, abrogated the AURKA-mediated STAT3 activation. These results confirm that the AURKA-JAK2 axis is the main mechanism by which AURKA regulates STAT3 activity. In conclusion, we report, for the first time, that AURKA promotes STAT3 activity through regulating the expression and phosphorylation levels of JAK2. This highlights the importance of targeting AURKA as a therapeutic approach to treat gastric and esophageal cancers.

Regulation of Desmocollin3 Expression by Promoter Hypermethylation is Associated with Advanced Esophageal Adenocarcinomas

BACKGROUND: Desmocollin3 (DSC3) is a member of the cadherin superfamily of calcium-dependent cell adhesion molecules and plays an important role in tumor invasion and metastasis. In this study, we investigated the epigenetic mechanism that regulates DSC3 expression in esophageal adenocarcinomas (EACs). METHODS: Expression of DSC3 was analyzed by quantitative real-time polymerase chain reaction (qRT-PCR). The promoter DNA methylation level of DSC3 was examined using quantitative bisulfite pyrosequencing. RESULTS: The qRT-PCR analysis demonstrated significant down-regulation of the DSC3 mRNA levels in human EAC cell lines and tissue samples (P<.001). In addition, the EAC cell lines and tumor samples have aberrant promoter hypermethylation as compared to normal esophageal samples (P<.001). DSC3 promoter hypermethylation (>10% methylation level) was detected in 97.5% (39/40) of EAC samples whereas none of the normal tissue samples showed hypermethylation (P<.0001). There was a significant inverse correlation between promoter DNA methylation levels and mRNA expression folds for DSC3 (coefficient r=-0.685, P<.0001). Treatment of FLO-1 and SKGT4 EAC cells with 5-Aza-deoxytidine led to a significant reduction in the promoter DNA methylation levels with restoration of the DSC3 expression, suggesting that promoter DNA methylation is a key epigenetic mechanism regulating DSC3 expression. High DSC3 promoter DNA methylation levels were significantly correlated with advanced tumor stage (P<.001) and lymph node metastasis (P<.001). CONCLUSION: Taken together, our results demonstrate that epigenetic silencing of DSC3 is a frequent finding in EAC that is possibly associated with advanced stages.

Glutathione peroxidase 7 has potential tumour suppressor functions that are silenced by location-specific methylation in oesophageal adenocarcinoma

OBJECTIVE

To investigate the potential tumour suppressor functions of glutathione peroxidase 7 (GPX7) and examine the interplay between epigenetic and genetic events in regulating its expression in oesophageal adenocarcinomas (OAC).

DESIGN

In vitro and in vivo cell models were developed to investigate the biological and molecular functions of GPX7 in OAC.

RESULTS

Reconstitution of GPX7 in OAC cell lines, OE33 and FLO-1, significantly suppressed growth as shown by the growth curve, colony formation and EdU proliferation assays. Meanwhile, GPX7-expressing cells displayed significant impairment in G1/S progression and an increase in cell senescence. Concordant with the above functions, Western blot analysis displayed higher levels of p73, p27, p21 and p16 with a decrease in phosphorylated retinoblastoma protein (RB), indicating its increased tumour suppressor activities. On the contrary, knockdown of GPX7 in HET1A cells (an immortalised normal oesophageal cell line) rendered the cells growth advantage as indicated with a higher EdU rate, lower levels of p73, p27, p21 and p16 and an increase in phosphorylated RB. We confirmed the tumour suppressor function in vivo using GPX7-expressing OE33 cells in a mouse xenograft model. Pyrosequencing of the GPX7 promoter region (-162 to +138) demonstrated location-specific hypermethylation between +13 and +64 in OAC (69%, 54/78). This was significantly associated with the downregulation of GPX7 (p<0.01). Neither mutations in the coding exons of GPX7 nor DNA copy number losses were frequently present in the OAC examined (<5%).

CONCLUSIONS

Our data suggest that GPX7 possesses tumour suppressor functions in OAC and is silenced by location-specific promoter DNA methylation.

Loss of glutathione peroxidase 7 promotes TNF-α-induced NF-κB activation in Barrett's carcinogenesis

Esophageal adenocarcinoma (EAC) is a classic example of inflammation-associated cancer, which develops through GERD (gastroesophageal reflux disease)-Barrett's esophagus (BE)-dysplasia-adenocarcinoma sequence. The incidence of EAC has been rising rapidly in the USA and Western countries during the last few decades. The functions of glutathione peroxidase 7 (GPX7), an antioxidant enzyme frequently silenced during Barrett's tumorigenesis, remain largely uncharacterized. In this study, we investigated the potential role of GPX7 in regulating nuclear factor-kappaB (NF-κB) activity in esophageal cells. Western blot analysis, immunofluorescence and luciferase reporter assay data indicated that reconstitution of GPX7 expression in CP-A (non-dysplastic BE cells) and FLO-1 (EAC cells) abrogated tumor necrosis factor-α (TNF-α)-induced NF-κB transcriptional activity (P < 0.01) and nuclear translocation of NF-κB-p65 (P = 0.01). In addition, we detected a marked reduction in phosphorylation levels of components of NF-κB signaling pathway, p-p65 (S536), p-IκB-α (S32) and p-IKKα/β (S176/180), as well as significant suppression in induction of NF-κB target genes [TNF-α, interleukin (IL)-6, IL-8, IL-1β, CXCL-1 and CXCL-2] following treatment with TNF-α in GPX7-expressing FLO-1 cells as compared with control cells. We validated these effects by knockdown of GPX7 expression in HET1A (normal esophageal squamous cells). We found that GPX7-mediated suppression of NF-κB is independent of reactive oxygen species level and GPX7 antioxidant function. Further mechanistic investigations demonstrated that GPX7 promotes protein degradation of TNF-receptor 1 (TNFR1) and TNF receptor-associated factor 2 (TRAF2), suggesting that GPX7 modulates critical upstream regulators of NF-κB. We concluded that the loss of GPX7 expression is a critical step in promoting the TNF-α-induced activation of proinflammatory NF-κB signaling, a major player in GERD-associated Barrett's carcinogenesis.

Role of aurora kinase A on regulating inflammation and inducing NF-κB pathway activation in gastric cancer

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Background: Aurora kinase A gene (AURKA) is frequently amplified and/or overexpressed in several malignancies. Inflammation contributes to the pathogenesis of gastric tumorigenesis. We explored the roles of AURKA in inflammation and tumorigenesis. Methods: Immunofluorescence, immunohistochemistry, Quantitative real-time PCR, immunoblot, co-immunoprecipitation, luciferase reporter, and in vitro kinase assays were used to analyze AGS and MKN28 gastric cancer cells. We also analyzed Tff1–/– mice, growth of tumor xenografts, and human tissues. Results: We showed an elevated level of AURKA in the Tff1–/– gastric tissues as compared to wild-type. We also found a positive correlation between AURKA and inflammation (coefficient r = 0.25; P = 0.0056) as well as TNF-α (coefficient r = 0.25; P = 0.0057). AURKA inhibition by MLN8237, a specific AURKA inhibitor, reduced nuclear staining of NFκB in human gastric cancer samples and mouse epithelial cells, suppressed NFκB reporter activity, and reduced the expression of NFκB target genes that regulate inflammation and cell survival. Additionally, AURKA inhibition reduced xenograft tumor size in mice and reversed the development of gastric tumors in Tff1–/– mice. Further, we found that AURKA regulate NFκB activity by directly binding and phosphorylating IκBα in vitro. Premalignant and malignant lesions from the gastric mucuosa of patients had increased levels of AURKA protein and nuclear NFκB, compared with healthy gastric tissue. Conclusions: In analyses of gastric cancer cell lines, human tissue samples, and mouse models, we found AURKA to be upregulated during chronic inflammation to promote IκBα-mediated activation of NFκB and tumorigenesis. This provides a novel role of AURKA in cancer and shows the importance of targeting it as a therapeutic approach in cancer treatment.

Regulation of STAT3 activity by DARPP-32 in gastric cancer

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Background: Dopamine and cAMP regulated phosphoprotein MW 32 kDa (DARPP-32) and its truncated form (t-DARPP) are overexpressed in two-thirds of gastric adenocarcinomas. STAT3 is a member of STAT family. It mediates the expression of a variety of genes in response to cell stimuli, and thus plays a key role in many cellular processes such as cell growth and apoptosis. Constitutive STAT3 activation is associated with various human cancers and commonly suggests poor prognosis. It has anti-apoptotic as well as proliferative effects. The relationship and interaction between DARPP-32 and STAT3 remain unknown. Methods: DARPP-32 was stable or transient overexpressed in gastric cancer cell lines. STAT3 expression and transcriptional activity were investigated by immunofluorescence and STAT3 luciferase reporter assay. DARPP-32 mRNA level was detected in 63 gastric cancer samples. Results: Using stable and transient expression of DARPP-32 and t-DARPP in AGS gastric cancer cell line, lacking endogenous DARPP-32, led to a significant increase of the phosphorylation of STAT3 as compared to empty vector control. Consistent with these findings, immunofluorescence assay also showed the up-regulation of nuclear p-STAT3 in AGS cells following transient expression of DARPP-32, as compared to empty vector control. Using the STAT3 luciferase reporter assay, AGS cells with stable overexpression of DARPP-32 showed higher luciferase activity than empty vector stable cells with and without IL-6 stimulate (p<0.01). Using qPCR in 63 gastric cancers, we found that DARPP-32 is frequently overexpressed in gastric cancer samples (p=0.018). We have also shown that DARPP-32 has a progressive increase in expression from normal to metaplasia, dysplasia, and adenocarcinoma (p<0.001). The relationship between DARPP-32 and STAT3 in these tissues will be examined. Conclusions: Our results suggest that DARPP-32 overexpression may participate in regulating the STAT3 phosphorylation and activating STAT3 signaling pathway in gastric cancer. The precise signaling mechanisms that mediate this activation and its functional impact on gastric tumorigenesis are under investigation.

Aurora kinase A promotes inflammation and tumorigenesis in mice and human gastric neoplasia

BACKGROUND & AIMS

Chronic inflammation contributes to the pathogenesis of gastric tumorigenesis. The aurora kinase A (AURKA) gene is frequently amplified and overexpressed in gastrointestinal cancers. We investigated the roles of AURKA in inflammation and gastric tumorigenesis.

METHODS

We used quantitative real-time reverse transcription polymerase chain reaction, immunofluorescence, immunohistochemistry, luciferase reporter, immunoblot, co-immunoprecipitation, and in vitro kinase assays to analyze AGS and MKN28 gastric cancer cells. We also analyzed Tff1(-/-) mice, growth of tumor xenografts, and human tissues.

RESULTS

We correlated increased expression of AURKA with increased levels of tumor necrosis factor-α and inflammation in the gastric mucosa of Tff1(-/-) mice (r = 0.62; P = .0001). MLN8237, an investigational small-molecule selective inhibitor of AURKA, reduced nuclear staining of nuclear factor-κB (NF-κB) p65 in human gastric cancer samples and mouse epithelial cells, suppressed NF-κB reporter activity, and reduced expression of NF-κB target genes that regulate inflammation and cell survival. Inhibition of AURKA also reduced growth of xenograft tumors from human gastric cancer cells in mice and reversed the development of gastric tumors in Tff1(-/-) mice. AURKA was found to regulate NF-κB activity by binding directly and phosphorylating IκBα in cells. Premalignant and malignant lesions from the gastric mucosa of patients had increased levels of AURKA protein and nuclear NF-κB, compared with healthy gastric tissue.

CONCLUSIONS

In analyses of gastric cancer cell lines, human tissue samples, and mouse models, we found AURKA to be up-regulated during chronic inflammation to promote activation of NF-κB and tumorigenesis. AURKA inhibitors might be developed as therapeutic agents for gastric cancer.

HDM2 regulation by AURKA promotes cell survival in gastric cancer

PURPOSE

Suppression of P53 (tumor protein 53) transcriptional function mediates poor therapeutic response in patients with cancer. Aurora kinase A (AURKA) and human double minute 2 (HDM2) are negative regulators of P53. Herein, we examined the role of AURKA in regulating HDM2 and its subsequent effects on P53 apoptotic function in gastric cancer.

EXPERIMENTAL DESIGN

Primary tumors and in vitro gastric cancer cell models with overexpression or knockdown of AURKA were used. The role of AURKA in regulating HDM2 and cell survival coupled with P53 expression and activity were investigated.

RESULTS

Overexpression of AURKA enhanced the HDM2 protein level; conversely, knockdown of endogenous AURKA decreased expression of HDM2 in AGS and SNU-1 cells. Dual co-immunoprecipitation assay data indicated that AURKA was associated with HDM2 in a protein complex. The in vitro kinase assay using recombinant AURKA and HDM2 proteins followed by co-immunoprecipitation revealed that AURKA directly interacts and phosphorylates HDM2 protein in vitro. The activation of HDM2 by AURKA led to induction of P53 ubiquitination and attenuation of cisplatin-induced activation of P53 in gastric cancer cells. Inhibition of AURKA using an investigational small-molecule specific inhibitor, alisertib, decreased the HDM2 protein level and induced P53 transcriptional activity. These effects markedly decreased cell survival in vitro and xenograft tumor growth in vivo. Notably, analysis of immunohistochemistry on tissue microarrays revealed significant overexpression of AURKA and HDM2 in human gastric cancer samples (P < 0.05).

CONCLUSION

Collectively, our novel findings indicate that AURKA promotes tumor growth and cell survival through regulation of HDM2-induced ubiquitination and inhibition of P53. Clin Cancer Res; 20(1); 76-86. ©2013 AACR.

Regulation of HDM2 E3-ubiquitin ligase in esophageal adenocarcinoma cells by AURKA

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Background: Esophageal adenocarcinomas (EAC) exhibit intrinsic resistance against chemotherapy. AURKA regulates cell cycle progression and its overexpression is associated with oncogenic transformation. We have recently reported that AURKA is significantly overexpressed in about 70% of human EAC tissue samples and EAC cell lines. We have previously shown that AURKA inhibits p53- and p73-mediated apoptotic pathways in GI adenocarcinomas. HDM2 is an E3-ubiquitin ligase which is closely involved in regulating p53 and p73 protein stability and activity. In this study we demonstrate that AURKA directly interacts with HDM2 and regulates HDM2 protein expression and phosphorylation in both FLO-1 and OE33 EAC cells. Methods and Results: Western blot analyses were done following AURKA overexpression with adenovirus, knockdown with si-RNA or inhibition with MLN 8237 (0.5µM) in FLO-1 and OE33 EAC cell lines. The data indicated that overexpression of AURKA induced both total and phospho-HDM2-(Ser166) protein levels. Knockdown or inhibition of AURKA significantly decreased expression of both total and phospho-HDM2-(Ser166) protein levels in FLO-1 and OE33 EAC cells. Additionally, following adenovirus mediated overexpression of AURKA, co-immunoprecipitaion (Co-IP) was done for AURKA and HDM2 in FLO-1 and OE33 EAC cells. The two-way Co-IP data indicated the presence of HDM2 in a complex associated with AURKA and vice-versa. The data from in vitro protein kinase assay indicated that recombinant AURKA directly phosphorylates recombinant HDM2 at Ser166 site. To confirm direct interaction between recombinant AURKA and HDM2 proteins we performed IP following the in vitro kinase assay. The in vitro kinase IP data indicates that kinase intact recombinant AURKA directly interacts and phosphorylates recombinant HDM2 protein. Conclusions: Our data indicate that AURKA regulates HDM2 expression and phosphorylation in both FLO-1 and OE33 EAC cells. Additionally, we also report for the first time that AURKA directly interacts with HDM2 and phosphorylates it at Ser166 site. Therefore, our study suggests that AURKA-mediated regulation of HDM2 could be the major underlying mechanism for induction of apoptosis in p53-negative EAC.

Resistance to TRAIL is mediated by DARPP-32 in gastric cancer

PURPOSE

Dopamine and cAMP-regulated phosphoprotein, Mr 32,000 (DARPP-32), is overexpressed during the gastric carcinogenesis cascade. Here, we investigated the role of DARPP-32 in promoting resistance to treatment with TRAIL.

EXPERIMENTAL DESIGN

In vitro cell models including stable expression and knockdown of DARPP-32 were used. The role of DARPP-32 in regulating TRAIL-dependent apoptosis was evaluated by clonogenic survival assay, Annexin V staining, immunofluorescence, quantitative reverse transcriptase PCR, Western blot, and luciferase reporter assays.

RESULTS

Stable expression of DARPP-32 in MKN-28 cells enhanced cell survival and suppressed TRAIL-induced cytochrome c release and activation of caspase-8, -9, and -3. Conversely, short hairpin RNA-mediated knockdown of endogenous DARPP-32 sensitized the resistant MKN-45 cells to TRAIL-induced apoptosis and enhanced TRAIL-mediated activation of caspase-8, -9, and -3. DARPP-32 induced BCL-xL expression through activation of Src/STAT3 signaling, and treatment with the Src-specific inhibitor PP1 abrogated DARPP-32-dependent BCL-xL upregulation and cell survival in MKN-28 cells. The TRAIL treatment induced caspase-dependent cleavage of NF-κBp65 protein; this cleavage was prevented by DARPP-32, thus maintaining NF-κB activity and the expression of its target, FLIP(S) protein. This suggests that upregulation of BCL-xL could play a possible role in blocking the mitochondria intrinsic apoptosis pathway, whereas the DARPP-32 effect on the NF-κB/FLIP(S) axis could serve as an additional negative feedback loop that blocks TRAIL-induced activation of caspase-8.

CONCLUSION

Our findings uncover a novel mechanism of TRAIL resistance mediated by DARPP-32, whereby it inhibits the intrinsic apoptosis pathway through upregulation of BCL-xL, and the extrinsic apoptosis pathway through the NF-κB/FLIP(S) axis.

The aurora kinase A inhibitor MLN8237 enhances cisplatin-induced cell death in esophageal adenocarcinoma cells

Esophageal adenocarcinomas are poorly responsive to chemotherapeutics. This study aimed to determine the levels of Aurora kinase A (AURKA) and the therapeutic potential of MLN8237, an investigational AURKA inhibitor, alone and in combination with cisplatin. Using quantitative real-time PCR, we detected frequent AURKA gene amplification (15 of 34, 44%) and mRNA overexpression (37 of 44, 84%) in esophageal adenocarcinomas (P < 0.01). Immunohistochemical analysis showed overexpression of AURKA in more than two-thirds of esophageal adenocarcinoma tissue samples (92 of 132, 70%; P < 0.001). Using FLO-1, OE19, and OE33 esophageal adenocarinoma cell lines, with constitutive AURKA overexpression and mutant p53, we observed inhibition of colony formation with a single treatment of 0.5 μmol/L MLN8237 (P < 0.05). This effect was further enhanced in combination with 2.5 μmol/L cisplatin (P < 0.001). Twenty-four hours after treatment with the MLN8237 or MLN8237 and cisplatin, cell-cycle analyses showed a sharp increase in the percentage of polyploid cells (P < 0.001). This was followed by an increase in the percentage of cells in the sub-G(1) phase at 72 hours, concordant with the occurrence of cell death (P < 0.001). Western blot analysis showed higher induction of TAp73β, PUMA, NOXA, cleaved caspase-3, and cleaved PARP with the combined treatment, as compared with a single-agent treatment. Using xenograft models, we showed an enhanced antitumor role for the MLN8237 and cisplatin combination, as compared with single-agent treatments (P < 0.001). In conclusion, this study shows frequent overexpression of AURKA and suggests that MLN8237 could be an effective antitumor agent, which can be combined with cisplatin for a better therapeutic outcome in esophageal adenocarcinomas.

Effect of a combination of aurora kinase A inhibitor MLN-8237 and cisplatin on gastrointestinal tumors

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Background: Gastric cancers respond poorly to current chemotherapeutic protocols indicating active intrinsic mechanisms against drug induced cell death. We have previously reported that AURKA overexpression induces pro-survival (AKT and β-catenin) and inhibits apoptotic (p53 and p73) pathways.

Methods: We evaluated the effect of AURKA specific inhibitor (MLN-8237) alone and/or in combination with cisplatin (CDDP) in gastrointestinal (GI) cancer cells. Following treatment with MLN-8237 and/or CDDP, cell survival, cell viability, western blot and qRT-PCR analyses were done on GI cancer cell lines. Additionally, tumor xenografted mice were treated with MLN (30mg/kg) and/or CDDP (2mg/kg) for 21 days and tumor volume was measured every alternate day.

Results: The ATP-Glo cell viability and cell survival assay data indicated that in comparison to single agent treatments alone; the combination treatment with MLN-8237 (0.5µM) and CDDP (2.5µM) significantly increased inhibition of cellular viability and survival (p<0.05) in AGS, KATO-III, MKN28, FLO-1, OE-19 and OE33 cell lines. Similarly, the western blot data exhibited higher levels of p73, Puma, Noxa, cleaved caspase 3 and cleaved PARP with MLN (0.5µM) and CDDP (2.5µM) combination treatment, as compared to single agent treatments in AGS, FLO-1 and OE33 cell lines. The tumor growth results for OE33 mouse xenograft study demonstrate synergistic antitumor effect with MLN-8237 and CDDP combination in the following order of effectiveness: Control > CDDP > MLN-8237 > and MLN-8237/CDDP (p<0.01). Moreover, the qRT-PCR data from tumor xenograft samples treated with MLN-8237/CDDP combination showed significantly higher mRNA levels of p73 downstream transcriptional target genes (P21, PUMA, NOXA and BAX) (p<0.05).

Conclusions: Our in vitro and in vivo data indicate that inhibition of AURKA with MLN-8237 in combination with CDDP enhances the antitumor activity of MLN-8237 against GI cancer cells. Therefore, our study demonstrates that MLN-8237 is an effective anti-tumor agent which can be potentially combined with CDDP for better therapeutic outcome in GI cancer patients.