Gastric Cancer Microenvironment Research Articles

CPT1C-positive cancer-associated fibroblast facilitates immunosuppression through promoting IL-6-induced M2-like phenotype of macrophage

ABSTRACT Cancer-associated fibroblasts (CAFs) exhibit remarkable phenotypic heterogeneity, with specific subsets implicated in immunosuppression in various malignancies. However, whether and how they attenuate anti-tumor immunity in gastric cancer (GC) remains elusive. CPT1C, a unique isoform of carnitine palmitoyltransferase pivotal in regulating fatty acid oxidation, is briefly indicated as a protumoral metabolic mediator in the tumor microenvironment (TME) of GC. In the present study, we initially identified specific subsets of fibroblasts exclusively overexpressing CPT1C, hereby termed them as CPT1C+CAFs. Subsequent findings indicated that CPT1C+CAFs fostered a stroma-enriched and immunosuppressive TME as they correlated with extracellular matrix-related molecular features and enrichment of both immunosuppressive subsets, especially M2-like macrophages, and multiple immune-related pathways. Next, we identified that CPT1C+CAFs promoted the M2-like phenotype of macrophage in vitro. Bioinformatic analyses unveiled the robust IL-6 signaling between CPT1C+CAFs and M2-like phenotype of macrophage and identified CPT1C+CAFs as the primary source of IL-6. Meanwhile, suppressing CPT1C expression in CAFs significantly decreased IL-6 secretion in vitro. Lastly, we demonstrated the association of CPT1C+CAFs with therapeutic resistance. Notably, GC patients with high CPT1C+CAFs infiltration responded poorly to immunotherapy in clinical cohort. Collectively, our data not only present the novel identification of CPT1C+CAFs as immunosuppressive subsets in TME of GC, but also reveal the underlying mechanism that CPT1C+CAFs impair tumor immunity by secreting IL-6 to induce the immunosuppressive M2-like phenotype of macrophage in GC.

Analyzing the expression and clinical significance of CENPE in gastric cancer

BackgroundGastric cancer (GC) is a prevalent type of malignant gastrointestinal tumor. Many studies have shown that CENPE acts as an oncogene in some cancers. However, its expression level and clinical value in GC are not clear.MethodsObtaining clinical data information on gastric adenocarcinoma from TCGA and GEO databases. The gene expression profiling interaction analysis (GEPIA) was used to evaluate the relationship between prognosis and CENPE expression in gastric cancer patients. Utilizing the UALCAN platform, the correlation between CENPE expression and clinical parameters was examined. Functions and signaling pathways of CENPE were analyzed using the Gene Ontology (GO), the Kyoto Encyclopedia of Genes and Genomes (KEGG), and Gene Set Enrichment Analysis (GSEA). The association between immunological infiltrating cells and CENPE expression was examined using TIMER2.0. Validation was performed by real-time quantitative PCR (qPT-PCR) and immunohistochemical analysis.ResultsAccording to the analysis of the GEPIA database, the expression of CENPE is increased in gastric cancer tissues compared to normal tissues. It was also found to have an important relationship with the prognosis of the patient (p<0.05). The prognosis was worse and overall survival was lower in individuals with increased expression of CENPE. In line with the findings of the GEPIA, real-time fluorescence quantitative PCR (qPT-PCR) confirmed that CENPE was overexpressed in gastric cancer cells. Furthermore, It was discovered that H. pylori infection status and tumor grade were related to CENPE expression. Enrichment analysis revealed that CENPE expression was linked to multiple biological functions and tumor-associated pathways. CENPE expression also correlated with immune-infiltrating cells in the gastric cancer microenvironment and was positively connected to NK cells and mast cells. According to immunohistochemical examination, paracancerous tissues had minimal expression of CENPE, but gastric cancer showed significant expression of the protein.ConclusionsAccording to our findings, CENPE is substantially expressed in GC and may perhaps contribute to its growth. CENPE might be a target for gastric cancer therapy and a predictor of a bad prognosis.

Interpretation of PD-L1 expression in gastric cancer: summary of a consensus meeting of Korean gastrointestinal pathologists.

Nivolumab plus chemotherapy in the first-line setting has demonstrated clinical efficacy in patients with human epidermal growth factor receptor 2-negative advanced or metastatic gastric cancer, and is currently indicated as a standard treatment. Programmed death-ligand 1 (PD-L1) expression is an important biomarker for predicting response to anti-programmed death 1/PD-L1 agents in several solid tumors, including gastric cancer. In the CheckMate-649 trial, significant clinical improvements were observed in patients with PD-L1 combined positive score (CPS) ≥ 5, determined using the 28-8 pharmDx assay. Accordingly, an accurate interpretation of PD-L1 CPS, especially at a cutoff of 5, is important. The CPS method evaluates both immune and tumor cells and provides a comprehensive assessment of PD-L1 expression in the tumor microenvironment of gastric cancer. However, CPS evaluation has several limitations, one of which is poor interobserver concordance among pathologists. Despite these limitations, clinical indications relying on PD-L1 CPS are increasing. In response, Korean gastrointestinal pathologists held a consensus meeting for the interpretation of PD-L1 CPS in gastric cancer. Eleven pathologists reviewed 20 PD-L1 slides with a CPS cutoff close to 5, stained with the 28-8 pharmDx assay, and determined the consensus scores. The issues observed in discrepant cases were discussed. In this review, we present cases of gastric cancer with consensus PD-L1 CPS. In addition, we briefly touch upon current practices and clinical issues associated with assays used for the assessment of PD-L1 expression in gastric cancer.

Effector Function Characteristics of Exhausted CD8+ T-cell in Microsatellite Stable and Unstable Gastric Cancer.

Gastric cancer exhibits molecular heterogeneity, with the microsatellite instability high (MSI-H) subtype drawing attention for its distinct features. Despite a higher survival rate, MSI-H gastric cancer lack significant benefits from conventional chemotherapy. The immune checkpoint inhibitors (ICIs), presents a potential avenue, but a deeper understanding of the tumor immune microenvironment of MSI-H gastric cancer is essential. We explored the molecular characteristics of CD8+ T cell subtypes in three MSI-H and three microsatellite stable (MSS) gastric cancer samples using single-cell RNA sequencing and spatial transcriptome analysis. In MSI-H gastric cancer, significantly higher proportions of effector memory T cell (Tem), exhausted T cell (Tex), proliferative exhausted T cell (pTex), and proliferative T cell were observed, while MSS gastric cancer exhibited significantly higher proportions of mucosal-associated invariant T (MAIT) cell and NKT cell. In MSI-H gastric cancer, Tex and pTex exhibited a significant upregulation of the exhaustion marker LAG3, as well as elevated expression of effector function markers such as IFNG, GZMB, GZMH, and GZMK, compared to those in MSS gastric cancer. The IFN-γ signaling pathway of Tex and pTex was retained compared to those of MSS gastric cancer. The spatial transcriptome analysis demonstrates the IFN-γ signaling pathway between neighboring Tex and malignant cell, showcasing a significantly elevated interaction in MSI-H gastric cancer. Our study reveals novel finding indicating that IFN-γ signaling pathway is retained in Tex and pTex of MSI-H gastric cancer, offering a comprehensive perspective for future investigations into immunotherapy for gastric cancer.

TOB1 modulates neutrophil phenotypes to influence gastric cancer progression and immunotherapy efficacy.

The ErbB-2.1(TOB1) signaling transducer protein is a tumor-suppressive protein that actively suppresses the malignant phenotype of gastric cancer cells. Yet, TOB1 negatively regulates the activation and growth of different immune cells. Understanding the expression and role of TOB1 in the gastric cancer immune environment is crucial to maximize its potential in targeted immunotherapy. This study employed multiplex immunofluorescence analysis to precisely delineate and quantify the expression of TOB1 in immune cells within gastric cancer tissue microarrays. Univariate and multivariate Cox analyses were performed to assess the influence of clinical-pathological parameters, immune cells, TOB1, and double-positive cells on the prognosis of gastric cancer patients. Subsequent experiments included co-culture assays of si-TOB1-transfected neutrophils with AGS or HGC-27 cells, along with EdU, invasion, migration assays, and bioinformatics analyses, aimed at elucidating the mechanisms through which TOB1 in neutrophils impacts the prognosis of gastric cancer patients. We remarkably revealed that TOB1 exhibits varying expression levels in both the nucleus (nTOB1) and cytoplasm (cTOB1) of diverse immune cell populations, including CD8+ T cells, CD66b+ neutrophils, FOXP3+ Tregs, CD20+ B cells, CD4+ T cells, and CD68+ macrophages within gastric cancer and paracancerous tissues. Significantly, TOB1 was notably concentrated in CD66b+ neutrophils. Survival analysis showed that a higher density of cTOB1/nTOB1+CD66b+ neutrophils was linked to a better prognosis. Subsequent experiments revealed that, following stimulation with the supernatant of tumor tissue culture, the levels of TOB1 protein and mRNA in neutrophils decreased, accompanied by enhanced apoptosis. HL-60 cells were successfully induced to neutrophil-like cells by DMSO. Neutrophils-like cells with attenuated TOB1 gene expression by si-TOB1 demonstrated heightened apoptosis, consequently fostering a malignant phenotype in AGS and HCG-27 cells upon co-cultivation. The subsequent analysis of the datasets from TCGA and TIMER2 revealed that patients with high levels of TOB1 combined neutrophils showed better immunotherapy response. This study significantly advances our comprehension of TOB1's role within the immune microenvironment of gastric cancer, offering promising therapeutic targets for immunotherapy in this context.

Enhanced epithelial-mesenchymal transition signatures are linked with adverse tumor microenvironment, angiogenesis and worse survival in gastric cancer.

Epithelial-mesenchymal transition (EMT) is a crucial mechanism that facilitates cancer cell metastasis. Despite its importance, the clinical significance of EMT in gastric cancer (GC) patients has yet to be clearly demonstrated. For gauging the extent of EMT in GC, we employed gene set variation analysis to score 807 patient samples from two large cohorts: TCGA and GSE84437. In both cohorts, EMT high GC showed a significant association with worse overall survival (hazard ratio (HR) = 1.74, p = 0.011 and HR = 2.01, p < 0.001, respectively). This association was stronger when considering the EMT signature score compared to the individual expressions of EMT-related genes (CDH1, CDH2, VIM, and FN1). While the EMT signature level did not differ among various cancers, high EMT signature specifically correlated with survival in GC alone. Mucinous and diffuse histological types exhibited higher EMT levels compared to others (p < 0.001), and the EMT signature level was correlated with tumor depth and AJCC stage (all p < 0.001). Interestingly, the EMT score was an independent factor for overall and disease-specific survival (multivariate; p = 0.006 and 0.032, respectively). EMT high GC displayed a lower fraction of Th1 cells and a higher fraction of dendritic cells, M1 macrophages and several stromal cells. EMT high GC exhibited an inverse correlation with cell proliferation-related gene sets. While they significantly enriched multiple pro-cancerous gene sets, such as TGF-β signaling, hypoxia, and angiogenesis. The presence of EMT signature in a bulk tumor was linked to TGF-β signaling, hypoxia, and angiogenesis, and was also associated with poorer survival outcomes in GC patients.

Abstract 5075: Transcriptomic landscape of tumor microenvironment in gastric cancer in treatment with different types of cancer drugs

Abstract Gastric cancer (GC) in the fifth-leading types of cancer and the third-leading cause of death from cancer. Characterization of tumor microenvironment (TME) in GC is important not only to comprehensively understand tumor biology in GC but also to develop a novel cancer therapeutics targeting TME. In this study, we conducted multi-omics analyses of single-cell RNA sequencing (scRNA-seq), bulk RNA sequencing (bulk RNA-seq), and whole exome sequencing (WES) using biopsied tumor samples through endoscopy from 23 GC patients: 3 treatment-naïve patients, 7 patients in treatment with chemotherapy (Chemo), 5 patients in combination treatment with chemotherapy and immune checkpoint blockade (Chemo+CPI), 3 patients in combination treatment with chemotherapy and Her2-antibody targeted therapy (Chemo+Her2i), and 5 patients in third-line or later treatment. We initially classified the GC samples into 4 molecular subtypes (CIN, GS, MSI, and EBV) using datasets of WES, bulk RNA-seq and scRNA-seq, showing that our samples were mainly composed of CIN (n=7) and GS (n=16) types. In scRNA-seq, we revealed that drug treatments profoundly modulated not only proportions of TME components but also their molecular characteristics. For instance, Chemo+CPI treated patients showed higher proportion of CD8+ cytotoxic T cells with activation and/or exhaustion markers. Combination treatments with Chemo+Her2i, in addition, resulted in higher Trail and Estrogen signaling pathways in epithelial cells of TME components. These findings suggest that interventions with certain cancer therapeutic drugs could substantially convert transcriptome landscape and reconstitute GC TME components. High-resolution of GC TME analyses should provide a clue for developing a next generation of cancer therapeutic drugs. Citation Format: Hiroki Yamashita, Jason Guoqiang Zhang, Chiaki Mashima, Ryo Kamata, Tomoko Yamamori, Izuma Nakayama, Akihito Kawazoe, Kohei Shitara, Tomonori Yano, Qunli Xu, Akihiro Ohashi, Takeshi Saito. Transcriptomic landscape of tumor microenvironment in gastric cancer in treatment with different types of cancer drugs [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5075.

Abstract 5583: Helicobacter pylori induces the wee1, promoting immune suppressive in human gastric adenocarcinoma

Abstract Background: Gastric cancer (GC) is the fourth most common cause of cancer-related death worldwide. GC has a dismal 5-year survival rate of about 32%. Helicobacter pylori (H. pylori) infection is the strongest risk factor for gastric carcinogenesis. 75-90% of gastric cancer patients exhibit positive H. pylori serology. WEE1 is a nuclear kinase that regulates cell cycle progression by inhibiting cyclin-dependent kinases. Methods &amp; Results: Analysis of non-cancer normal stomach tissue (n=360) and human GC samples (n=1221) identified that WEE1 mRNA was significantly overexpressed in GC. Using immunohistochemistry (IHC) staining in 41 normal and 44 GC human samples, the data indicated that WEE1 protein was significantly overexpressed in GC. Western blot and immunofluorescence (IF) staining confirmed that H. pylori infection induces WEE1 overexpression in GC cells with an unexpected cytosolic localization of WEE1 in GC cells. Tff1 knockout GC mouse model (Tff1-/-) was infected with mouse-adapted H. pylori strain PMSS1. Western blot and immunohistochemistry data demonstrated that H. pylori infection induced WEE1 expression in Tff1 -/- HGD/cancer mouse gastric tissues compared to control Tff1 -/- mouse stomach. To study how H. pylori infection induces WEE1 in GC, analysis from miRTAR, Target Scan, and miRDB demonstrated that WEE1 is predicted to be targeted by miR-497-5p. Using qRT-PCR analysis, we assessed 30 normal and 30 GC human tissue samples, revealing a pronounced downregulation of miR-497-5p in GC specimens. Western blot analysis confirmed that the restoration of miR-497-5p in GC cells markedly reduced WEE1 protein expression. Interestingly, H. pylori infection further decreased miR-497-5p levels in GC cells, upregulating WEE1 protein expression. Since the miR-497-5P host gene promoter region contains CpG islands, we confirmed that treatment with 5 Azacytidine (demethylating agent) or DNMT1 knockdown induced expression of miR-497-5p with decreased WEE1 level in GC cells. Furthermore, our preliminary results indicate that aberrant WEE1 overexpression in GC demonstrates a significant positive correlation with immune-suppression gene signatures, underscoring its predictive value for unfavorable patient survival outcomes in GC. Using the TFF1 knockout mouse GC model, we found that WEE1 inhibition notably decreases the number and activation of CD4+ and CD8+ T cells in neoplastic gastric tissues. These findings also indicate a crucial relationship between WEE1 and the immunosuppressive microenvironment in GC, establishing WEE1 as a promising therapeutic target to enhance therapeutic efficacy and overcome immunotherapy resistance in GC. Conclusions: Our findings demonstrated a novel mechanism in which H. pylori activates the WEE1 in GC, promoting an immune suppressive microenvironment. WEE1 inhibition with immunotherapy could be a promising therapeutic method for GC patients. Citation Format: Md Obaidul Islam, Krishnapriya Thangaretnam, Heng Lu, Dunfa Peng, Nadeem Sidiq Bhat, Mohammed Soutto, Wael El-Rifai, Zheng Chen. Helicobacter pylori induces the wee1, promoting immune suppressive in human gastric adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5583.

Abstract 162: Fatty acid synthesis blockade synergizes with immune checkpoint blockade by repolarizing macrophages and enhancing anti-tumor cytotoxicity in gastric cancer

Abstract Background: Immune checkpoint blockade (ICB), which unleashes potent CD8+ T cell-based anti-tumor responses, has emerged as a promising therapeutic option for several cancer types. However, response rates stay limited in gastric cancer (GC) patients, indicating the necessity of combinational strategies to overcome other immunosuppressive factors. Fatty acid synthesis (FAS) is an indispensable metabolic pathway proven to support cancer cell survival. The rate-limiting enzyme of FAS, FASN, is upregulated in several cancers and could contribute to cancer immune escape. Though some investigations propose that specific gene alterations can cause FASN upregulation under the GC setting, the immunoregulatory role and therapeutic value of FASN in the tumor microenvironment (TME) of GC have not been fully elucidated. Methods: FASN expression was measured by Western Blotting and flow cytometry. Bioinformatic analysis was conducted via an online website (www.camoip.net). The syngeneic GC mouse model was established by subcutaneous inoculation of MFC cells in 615-line mice, treated by vehicles, FASN inhibitor (FASNi), anti-PD-1 antibodies, or FASNi+anti-PD-1 antibodies. TAM and CD8+ T cell depletion was implemented by anti-CSF1R and anti-CD8α antibodies. Bone marrow-derived macrophages (BMDMs) were extracted from the femurs of 615-line mice, induced by M-CSF and stimulated by LPS or IL-4. The proportions and functional status of immune cells were identified by flow cytometry. Results: FASN was upregulated in GC tissues and GC human cell lines. Bioinformatic analyses demonstrated that FASN expression was related to poor infiltration of cytotoxic lymphocytes, as well as the downregulation of pathways related to anti-cancer immune responses. FASNi inhibited tumor growth in a syngeneic GC mouse model, with elevated PD-1 and IFN-γ expression in CD8+ T cells and increased NK cell infiltration, suggesting the enhancement in anti-cancer cytotoxicity. Meanwhile, FASNi induced a shift from M2-like to M1-like in tumor-associated macrophages (TAM). We detected that M2-like TAM and CD8+ T cells harbored higher FASN expression than other immune cells in GC mouse tissues, and tumor-suppressing effects of FASN inhibition could be reversed by TAM and CD8+ T cell depletion, which corroborated the key role of TAM and CD8+ T cells in shaping FASN-mediated tumor regulation. FASNi could also repolarize BMDMs from M1-like to M2-like in vitro. Finally, FASNi exhibited synergistic tumor control with anti-PD-1 therapy in GC and melanoma mouse models. Conclusion: This work sheds light on the impact of FASN on TME modulation of GC. We proved that FASNi could repolarize M2-like TAM to M1 phenotypes and promote cytotoxic lymphocyte-mediated anti-tumor immunity. Our results propose FASN inhibition as a potential therapeutic strategy to sensitize ICB therapy in GC. Citation Format: Hanbing Wang, Tao Shi, Yue Wang, Yuting Luo, Yunfeng Pan, Xiaoyu Zhou, Yue Zhang, Baorui Liu, Jia Wei. Fatty acid synthesis blockade synergizes with immune checkpoint blockade by repolarizing macrophages and enhancing anti-tumor cytotoxicity in gastric cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 162.

Abstract 6526: Spatial characterisation of the tumour immune microenvironment in ARID1A-deficient gastric cancer

Abstract AT-Rich Interacting Domain 1A (ARID1A) is an important component in SWI/SNF Complex, a chromatin remodeller and an established tumor suppressor gene that is mutated in a variety of cancer types. This includes endometrial (~45%), bladder (~20%), and gastric (~15%). ARID1A mutations usually lead to a loss of protein expression or function, which results in tumor progression. The loss of ARID1A has been linked to genomic instability, potentially making the tumor more immunogenic/amenable to immune checkpoint inhibitor therapy. However, there is a discrepancy between clinical and mechanistic studies in determining the consequence of ARID1A-loss on the tumor immune microenvironment (TIME): clinical studies have shown that ARID1A mutation is a potential predictive biomarker for immunotherapy success, whereas another mechanistic study found that ARID1A-loss results in a cold TIME that is less amenable to immunotherapy. Considering this controversy, our overarching objective is to use multiple high-dimensional microscopy-based techniques to robustly and comprehensively characterize the TIME sculpted by ARID1A-loss. We study this in the context of gastric cancer, a disease which has heterogenous responses to PD-1 based immunotherapy and also shows frequent (10-25%) mutations in ARID1A. We looked at two retrospective cohorts with 250 patients each, one from UK (Leeds) and one from Japan (KCCH). To ascertain ARID1A-loss in these patients, we have set up an IHC-based assay comparing ARID1A expression between tumor and stroma regions. From this, we derive a ratio. In both studies, we were able to clearly stratify the cohort into ARID1A-loss and ARID1A-wildtype. Leeds had about 23 cases (10%) of ARID1A-loss, while KCCH had 39 cases (17.9%). Looking at the clinical parameters, we realized that ARID1A-loss does not stratify for survival nor staging of the tumor, which is also seen in ARID1A-mutation studies. Using multiplex immunohistochemistry (IHC), we saw differences in the immune cell population. ARID1A-loss patients seem to have a greater proportion of CD3+ cells in the Leeds (1423 vs 666 cells/mm2, p = 0.0269) and KCCH cohorts (1457 vs 1268 cells/mm2, p = 0.1745). Interestingly, CD68+ cells also show an increase in the ARID1A-loss population in the Leeds (802.1 cells/mm2 vs 580.3 cells/mm2, p = 0.0649) and KCCH cohorts (659 vs 623.2 cells/mm2). However, CD20+ cells show no changes in abundance for either cohort (249.1 vs 193.2 cells/mm2, p = 0.4985; and 361.6 vs 357.5 cells/mm2, p = 0.9634) respectively. Overall, there seems to be an increase in the T-cell population in ARID1A-loss tumors and an increase in the macrophage population in stroma regions of ARID1A-loss tumors. The B-cell population remains unchanged. To complement our preliminary findings, we will leverage hyperplex and spatial transcriptome techniques to uncover the interactions between tumor cells and the TIME. Citation Format: Norbert Sheng Cong Tay, Yan Fen Peng, Heike Grabsch, Anand D. Jeyasekharan. Spatial characterisation of the tumour immune microenvironment in ARID1A-deficient gastric cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6526.

Abstract 282: SFRP4+ cancer associated fibroblasts activate epithelial to mesenchymal transitions in malignant cells and dictate adverse clinical outcomes in stomach cancer

Abstract Cancer-associated fibroblasts (CAFs), a pivotal component in the tumor microenvironment (TME) of gastric cancer (GC), play a crucial role in tumor progression and resistance to treatment. In this study, we performed analyses to build a comprehensive cellular landscape of fibroblasts in GC EMT using three single-cell RNA cohorts including ours (GSE183904, GSE134520 and GSE167297). We observed distinct fibroblast subtypes (CXCL14+/POSTN+, CXCL14+/APOE+, SFRP4+, and SFRP2+ fibroblasts). Among the subtypes, we observed that SFRP4+ fibroblasts sharing cellular origins with normal tissue-residing SFRP2+ myofibroblasts. Notably, SFRP4+ fibroblasts showed a regional prediction for tumor and deep tumor layers compared to normal and superficial tumor layers, respectively. To further understand the role of these fibroblasts, we employed spatial transcriptome data. Spatially resolving the cellular interactions within the TME, the adjacency of SFRP4+ CAFs to malignant cells undergoing epithelial-to-mesenchymal transition (EMT), was observed. Ligand-receptor analyses demonstrated SFRP4+CAFs regulate key genes of EMT in malignant cells (TGFBI, COL1A1, SPARC, COL3A1, COL1A2, and BGN). The regulatory roles of SFRP4+ CAFs in driving the epithelial-mesenchymal transition (EMT) of malignant cells were further validated in vitro. Clinical relevance was also demonstrated with the correlation between the abundance of SFRP4+ CAF and clinical outcomes, i.e., high SFRP4+CAF abundance was consistently associated with shorter survival of GC patients across cohorts. Thus, we present SFRP4+ CAFs as major fibroblast subtypes in GC TME. Spatial cellular architectures and in vitro evidence support that SFRP4+fibroblasts activate the EMT of malignant cells along with their association with patient prognosis. This study advances our understanding into the mechanistic roles of SFRP4+ fibroblasts in GC pathogenesis and progression, paving the way for potential targeted therapeutic strategies. Citation Format: Seungho Lee, Austin Cho, Hyoung-Il Kim, Hoon Hur, Jae-Ho Cheong, Tae-Min Kim. SFRP4+ cancer associated fibroblasts activate epithelial to mesenchymal transitions in malignant cells and dictate adverse clinical outcomes in stomach cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 282.

Abstract 2570: Gastric cancer with high neuron infiltration was associated with enhanced epithelial-to-mesenchymal transition, angiogenesis and poor clinical outcomes

Abstract Introduction: Neurons within the tumor microenvironment of gastric cancer (GC), as identified through immunohistochemistry, have been reported to be associated with worse overall survival (OS) of GC patients. However, histology-based analyses have limitations in quantifying nerve cells and investigating the underlying biology. Thus, we aim to study the clinical significance of intratumoral nerve cells in GC using computational deconvolution of transcriptomes from bulk tumors. Methods: Total of 807 GC patients from two independent cohorts (TCGA; n = 375, GSE84437; n = 432) were included, encompassing both clinical and transcriptomic profiles. The neuron infiltration fraction was determined using the xCell algorithm. Results: GC with high neuron infiltration was associated with high expressions of neurotransmitter receptors; beta-adrenaline, dopamine, muscarinic acetylcholine, and neurokinin receptors in TCGA cohort (all p &amp;lt; 0.02). It was associated with reduced mutation rate and increased intratumoral heterogeneity (all p ≦ 0.002), as well as less immune response; interferon-alpha and interferon-gamma, and with low infiltration of immune cells; CD4 memory, T-helper 1, M1 and M2 macrophages, and NK cells (all p ≦ 0.02). Further, neuron highly infiltrated GC enriched Epithelial-to-Mesenchymal Transition and Angiogenesis gene sets and had higher lymphatic and microvessel endothelial cells and pericyte infiltrations (all p ≦ 0.001). Conversely, GC with high neuron infiltration showed an inverse relationship with cell proliferation-related gene sets; E2F Targets, G2M Checkpoint, and MYC Targets v1 and v2, and had lower Ki67 gene expression (FDR &amp;lt; 0.25 and p &amp;lt; 0.001, respectively). High neuron infiltration in GC was associated with worse patient OS in TCGA cohort, which was validated in GSE84437 cohort (both p &amp;lt; 0.05). It was an independent prognostic factor of OS in both univariate and multivariate Cox-regression analysis in the TCGA cohort (hazard ratio [HR]: 1.46; 95% confidence interval [CI]: 1.01 to 2.12; p = 0.045 and [HR]:1.54; 95% CI: 1.05 to 2.26; p = 0.026). Conclusion: Our research indicates that high infiltration of neurons in GC correlates with high expressions of neurotransmitter receptors, high intratumoral heterogeneity, less immune response and immune cell infiltrations, and less cell proliferation. It enriched EMT and angiogenesis which may explain its association with worse patient survival. Citation Format: Kohei Chida, Masanori Oshi, Arya Mariam Roy, Jun Arima, Pia Sharma, Gabriella Kim Mann, Itaru Endo, Kenichi Hakamada, Kazuaki Takabe. Gastric cancer with high neuron infiltration was associated with enhanced epithelial-to-mesenchymal transition, angiogenesis and poor clinical outcomes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2570.

Cancer-associated fibroblasts: protagonists of the tumor microenvironment in gastric cancer.

Enhanced knowledge of the interaction of cancer cells with their environment elucidated the critical role of tumor microenvironment in tumor progression and chemoresistance. Cancer-associated fibroblasts act as the protagonists of the tumor microenvironment, fostering the metastasis, stemness, and chemoresistance of cancer cells and attenuating the anti-cancer immune responses. Gastric cancer is one of the most aggressive cancers in the clinic, refractory to anti-cancer therapies. Growing evidence indicates that cancer-associated fibroblasts are the most prominent risk factors for a poor tumor immune microenvironment and dismal prognosis in gastric cancer. Therefore, targeting cancer-associated fibroblasts may be central to surpassing resistance to conventional chemotherapeutics, molecular-targeted agents, and immunotherapies, improving survival in gastric cancer. However, the heterogeneity in cancer-associated fibroblasts may complicate the development of cancer-associated fibroblast targeting approaches. Although single-cell sequencing studies started dissecting the heterogeneity of cancer-associated fibroblasts, the research community should still answer these questions: "What makes a cancer-associated fibroblast protumorigenic?"; "How do the intracellular signaling and the secretome of different cancer-associated fibroblast subpopulations differ from each other?"; and "Which cancer-associated fibroblast subtypes predominate specific cancer types?". Unveiling these questions can pave the way for discovering efficient cancer-associated fibroblast targeting strategies. Here, we review current knowledge and perspectives on these questions, focusing on how CAFs induce aggressiveness and therapy resistance in gastric cancer. We also review potential therapeutic approaches to prevent the development and activation of cancer-associated fibroblasts via inhibition of CAF inducers and CAF markers in cancer.

Integrated single-cell sequencing, spatial transcriptome sequencing and bulk RNA sequencing highlights the molecular characteristics of parthanatos in gastric cancer.

Parthanatos is a novel programmatic form of cell death based on DNA damage and PARP-1 dependency. Nevertheless, its specific role in the context of gastric cancer (GC) remains uncertain. In this study, we integrated multi-omics algorithms to investigate the molecular characteristics of parthanatos in GC. A series of bioinformatics algorithms were utilized to explore clinical heterogeneity of GC and further predict the clinical outcomes. Firstly, we conducted a comprehensive analysis of the omics features of parthanatos in various human tumors, including genomic mutations, transcriptome expression, and prognostic relevance. We successfully identified 7 cell types within the GC microenvironment: myeloid cell, epithelial cell, T cell, stromal cell, proliferative cell, B cell, and NK cell. When compared to adjacent non-tumor tissues, single-cell sequencing results from GC tissues revealed elevated scores for the parthanatos pathway across multiple cell types. Spatial transcriptomics, for the first time, unveiled the spatial distribution characteristics of parthanatos signaling. GC patients with different parthanatos signals often exhibited distinct immune microenvironment and metabolic reprogramming features, leading to different clinical outcomes. The integration of parthanatos signaling and clinical indicators enabled the creation of novel survival curves that accurately assess patients' survival times and statuses. In this study, the molecular characteristics of parthanatos' unicellular and spatial transcriptomics in GC were revealed for the first time. Our model based on parthanatos signals can be used to distinguish individual heterogeneity and predict clinical outcomes in patients with GC.

Biological Clock Genes are Crucial and Promising Biomarkers for the Therapeutic Targets and Prognostic Assessment in Gastric Cancer.

Gastric cancer is one of the major public health problems worldwide. Circadian rhythm disturbances driven by circadian clock genes play a role in the development of cancer. However, whether circadian clock genes can serve as potential therapeutic targets and prognostic biomarkers for gastric cancer remains elusive. In this study, we comprehensively analyzed the potential relationship between circadian clock genes and gastric cancer using online bioinformatics databases such as GEPIA, cBioPortal, STRING, GeneMANIA, Metascape, TIMER, TRRUST, and GEDS. Biological clock genes are expressed differently in human tumors. Compared with normal tissues, only PER1, CLOCK, and TIMELESS expression differences were statistically significant in gastric cancer (p < 0.05). PER1 (p = 0.0169) and CLOCK (p = 0.0414) were associated with gastric cancer pathological stage (p < 0.05). Gastric cancer patients with high expression of PER1 (p = 0.0028) and NR1D1 (p = 0.016) had longer overall survival, while those with high expression of PER1 (p = 0.042) and NR1D1 (p = 0.016) had longer disease-free survival. The main function of the biological clock gene is related to the circadian rhythms and melatonin metabolism and effects. CLOCK, NPAS2, and KAT2B were key transcription factors for circadian clock genes. In addition, we also found important correlations between circadian clock genes and various immune cells in the gastric cancer microenvironment. This study may establish a new gastric cancer prognostic indicator based on the biological clock gene and develop new drugs for the treatment of gastric cancer using biological clock gene targets.

Uncovering the potential of APOD as a biomarker in gastric cancer: A retrospective and multi-center study

Gastric cancer (GC) poses a significant health challenge worldwide, necessitating the identification of predictive biomarkers to improve prognosis. Dysregulated lipid metabolism is a well-recognized hallmark of tumorigenesis, prompting investigation into apolipoproteins (APOs). In this study, we focused on apolipoprotein D (APOD) following comprehensive analyses of APOs in pan-cancer. Utilizing data from the TCGA-STAD and GSE62254 cohorts, we elucidated associations between APOD expression and multiple facets of GC, including prognosis, tumor microenvironment (TME), cancer biomarkers, mutations, and immunotherapy response, and identified potential anti-GC drugs. Single-cell analyses and immunohistochemical staining confirmed APOD expression in fibroblasts within the GC microenvironment. Additionally, we independently validated the prognostic significance of APOD in the ZN-GC cohort. Our comprehensive analyses revealed that high APOD expression in GC patients was notably associated with unfavorable clinical outcomes, reduced microsatellite instability and tumor mutation burden, alterations in the TME, and diminished response to immunotherapy. These findings provide valuable insights into the potential prognostic and therapeutic implications of APOD in GC.

Prognostic implications of tumor-infiltrating lymphocytes within the tumor microenvironment in gastric cancer

Tumor-infiltrating lymphocytes (TILs) play a regulatory role in the tumor-associated immune response and are important in the prognosis and treatment response of several cancers. However, because of its heterogeneity, the prognostic value of TILs in gastric cancer (GC) is still controversial. Thus, this study aimed to investigate the association between the density of TILs and patients' outcomes in GC. Patients with gastric adenocarcinoma who underwent curative intent gastrectomy were retrospectively investigated. The groups for analysis were determined on the basis of TIL intensity and percentage of CD3+T-cell infiltration by immunohistochemical. Furthermore, Epstein-Barr virus (EBV), microsatellite instability (MSI), T-cell ratio of CD4 to CD8, and programmed death protein ligand 1 (PD-L1) status were evaluated. A total of 345 patients were enrolled: 124 patients with GCs (35.9%) were classified as the low-CD3+TIL group, and 221 patients with GCs (64.1%) were classified as the high-CD3+TIL group. Poorly differentiated histology (P=.014), EBV-positive status (P<.001), PD-L1-positive status (P=.001), and CD4<CD8 (P<.001) were associated with high-CD3+GC. There was no difference regarding MSI status, the degree of tumor invasion (pT), the presence of lymph node metastasis, and pTNM stage between low- and high-CD3+groups. In survival analysis, the high-CD3+group had better disease-free survival and overall survival rates than had the low-CD3+group (P=.055 and P=.041, respectively). In the multivariate analysis, total gastrectomy, lymph node metastasis, advanced pT stage, and low CD3+levels were independent factors related to worse survival. High CD3+TILs levels were significantly associated with improved survival and could serve as prognostic biomarkers in GC. In addition, CD3+T-cell infiltration was related to both EBV-positive and PD-L1-positive GC and may assist in the investigation of targets in immunotherapy.

The integration of bulk and single-cell sequencing data revealed the function of FKBP10 in the gastric cancer microenvironment.

Due to the implementation of individualized treatment, the majority of gastric cancer patients have a favorable prognosis, but advanced gastric cancer with recurrence and distant metastasis still plagues some patients. As a member of the FK506-binding protein (FKBP65) family, there is growing evidence that FKBP10 plays a crucial role in tumorigenesis. However, the role of FKBP10 in the tumor microenvironment (TME) has been a prominent issue. The FKBP10 knockdown efficiency in gastric cancer cells was determined by quantitative real-time polymerase chain reaction (qRT-PCR). Wound healing and transwell analysis were performed to detect variations in cell invasion and migration. We integrated single-cell and bulk sequencing data to further elaborate the impact of FKBP10 and FKBP10-coexpressed genes (FCGs) in the TME via a variety of bioinformatics approaches. Here, we found that FKBP10 knockdown inhibited cell invasion and metastasis. FKBP10 was chiefly expressed in inflammatory cancer-associated fibroblasts (iCAFs), and FCGs principally mediated alterations in extracellular matrix (ECM) organization. Besides, according to nine prognosis-related FCGs, two disparate clusters were identified, and differences in tumor immune infiltration characteristics and immunotherapy response between different clusters were investigated. Our study provides insights into the expression and function of FKBP10 in the microenvironment of gastric cancer.

Ganodermanontriol regulates tumor-associated M2 macrophage polarization in gastric cancer.

We focused on investigating the role and mechanism of ganodermanontriol (GAN) in regulating the M2 polarization of tumor-associated macrophages in the gastric cancer microenvironment. M2 polarization of RAW264.7 macrophages was induced by IL-4 or co-culture with MFC, and the expression levels of M1 macrophage markers (TNF-α, IFN-γ, IL-1β) and M2 macrophage markers (IL-10, TGF-β, Arg-1) were detected by enzyme-linked immunosorbed assay (ELISA). The protein expression was assayed by Western-Blotting. For in vitro experiments, a tumor-bearing mouse model was established, with which the CD206 level was detected by histochemistry, and the binding mode between GAN and STAT6 was simulated through molecular dynamics. Both IL-4 and MFC could induce the M2 polarization of macrophages. GAN could inhibit such polarization, which produced unobvious effects on M1 markers, but could suppress the levels of M2 markers. GAN could inhibit the phosphorylated expression of STAT6, and M2 macrophages treated by it had a weakened ability to promote malignant behavior of MFC. According to the results of in vitro experiments, GAN could inhibit tumor growth, suppress the tissue infiltration of CD206 cells, and inhibit the phosphorylated expression of STAT6. Our results show that GAN can inhibit the M2 macrophage polarization in gastric cancer microenvironment, whose mechanism of action is associated with the regulation of STAT6 phosphorylation.

Tumor-infiltrating monocytic myeloid-derived suppressor cells contribute to the development of an immunosuppressive tumor microenvironment in gastric cancer.

Gastric cancer (GC) is characterized by an immunosuppressive and treatment-resistant tumor immune microenvironment (TIME). Here, we investigated the roles of different immunosuppressive cell types in the development of the GC TIME. Single-cell RNA sequencing (scRNA-seq) and multiplex immunostaining of samples from untreated or immune checkpoint inhibitor (ICI)-resistant GC patients were used to examine the correlation between certain immunosuppressive cells and the prognosis of GC patients. The results of the scRNA-seq analysis revealed that tumor-infiltrating monocytic myeloid-derived suppressor cells (TI-M-MDSCs) expressed higher levels of genes with immunosuppressive functions than other immunosuppressive cell types. Additionally, M-MDSCs in GC tissues expressed significantly higher levels of these markers than adjacent normal tissues. The M-MDSCs were most enriched in GC tissues relative to adjacent normal tissues. Among the immunosuppressive cell types assessed, the M-MDSCs were most enriched in GC tissues relative to adjacent normal tissues; moreover, their presence was most strongly associated with a poor prognosis. Immediate early response 3 (IER3), which we identified as a differentially expressed gene between M-MDSCs of GC and adjacent normal tissues, was an independent poor prognostic factor in GC patients (P = 0.0003). IER3+ M-MDSCs expressed higher levels of genes with immunosuppressive functions than IER3- M-MDSCs and were abundant in treatment-resistant GC patients. The present study suggests that TI-M-MDSCs, especially IER3+ ones, may play a predominant role in the development of the immunosuppressive and ICI-resistant GC TIME.