Tumor Microenvironment Of Gastric Cancer Research Articles

Immunotherapy and pan-apoptotic characterization of the tumor microenvironment in gastric cancer (STAD): a single-cell multidimensional analysis

BackgroundThe aim of this study was to elucidate the critical role of autophagy-related gene aggregation in gastric cancer tumor microenvironment cells and to investigate their major roles in cellular functions. In particular, the expression of these genes in tumor-associated fibroblast subtypes was scrutinized in an attempt to explain their cell-subpopulation-specific roles in cell–cell communication and regulation of cellular functions.MethodsIn this study, single-cell RNA sequencing data were first analyzed in multiple steps, including data preprocessing, cell clustering, and cell classification. Cell subpopulations and gene expression patterns were identified and analyzed using unsupervised non-negative matrix factorization (NMF) techniques. The dynamic expression of autophagy-related gene aggregates in various cell types was deciphered by pseudotime trajectory analysis (PTA). Intercellular communication analysis was performed using the CellChat R software package, revealing the intricate communication patterns and exchange of key signaling molecules between cell subpopulations, and SCENIC analysis was used to identify gene regulatory networks and reveal the mechanisms behind cellular heterogeneity.ResultCell subpopulations associated with pan-apoptosis were identified by NMF decomposition and SCENIC analysis. Cell–cell communication analysis revealed intricate communication patterns and exchange of key signaling molecules between cell subpopulations. Dynamic expression of autophagy-related genes aggregated in the pseudotemporal trajectory of STAD was observed by PTA. In the fibroblast subtype, different ligand-receptor interactions and their key roles in immunomodulation were observed.ConclusionBy deeply analyzing and comparing gene expression patterns within cellular subpopulations and intercellular communication, this study provides new insights into the role of pan-apoptosis-related genes in regulating immune responses and cellular functions in gastric cancer. These findings pave the way for further exploration of the role of these genes in tumorigenesis and immune regulation, as well as laying the foundation for potential therapeutic strategies.

Overexpression of ELF1 combined with MMP9 is associated with prognosis and tumor microenvironment in gastric cancer

Overexpression of ELF1 combined with MMP9 is associated with prognosis and tumor microenvironment in gastric cancer

Roles of the tumor microenvironment in the resistance to programmed cell death protein 1 inhibitors in patients with gastric cancer.

Despite the continuous developments and advancements in the treatment of gastric cancer (GC), which is one of the most prevalent types of cancer in China, the overall survival is still poor for most patients with advanced GC. In recent years, with the progress in tumor immunology research, attention has shifted toward immunotherapy as a therapeutic approach for GC. Programmed cell death protein 1 (PD-1) inhibitors, as novel immunosuppressive medications, have been widely utilized in the treatment of GC. However, many patients are still resistant to PD-1 inhibitors and experience recurrence in the advanced stages of PD-1 immunotherapy. To reduce the occurrence of drug resistance and recurrence in GC patients receiving PD-1 immunotherapy, to maximize the clinical activity of immunosuppressive drugs, and to elicit a lasting immune response, it is essential to research the tumor microenvironment mechanisms leading to PD-1 inhibitor resistance in GC patients. This article reviews the progress in studying the factors influencing the resistance to PD-1 inhibitors in the GC tumor microenvironment, aiming to provide insights and a basis for reducing resistance to PD-1 inhibitors for GC patients in the future.

High levels of tumor cell-intrinsic STING signaling are associated with increased infiltration of CD8+ T cells in dMMR/MSI-H gastric cancer

Mismatch repair deficient (dMMR)/microsatellite instability-high (MSI-H) gastric cancer (GC) exhibits an immune-active tumor microenvironment (TME) compared to MMR proficient (pMMR)/microsatellite stable/Epstein-Barr virus-negative [EBV (−)] GC. The tumor cell-intrinsic cyclic GMP–AMP synthase (cGAS)–stimulator of interferon genes (STING) pathway has been considered a key regulator of immune cell activation in the TME. However, its significance in regulating the immune-active TME in dMMR/MSI-H GC remains unclear. Here, we demonstrated that tumor cell-intrinsic cGAS–STING was highly expressed in dMMR GC compared to pMMR/EBV (−) GC. The expression of tumor cell-intrinsic STING was significantly and positively associated with the number of CD8+ tumor-infiltrating lymphocytes in GC. Analysis of TCGA datasets revealed that the expression of interferon-stimulated genes and STING downstream T-cell attracting chemokines was significantly higher in MSI-H GC compared to other subtypes of GC with EBV (−). These results suggest that tumor cell-intrinsic STING signaling plays a key role in activating immune cells in the dMMR/MSI-H GC TME and might serve as a novel biomarker predicting the efficacy of immunotherapy for GC treatment.

Cancer-Associated Fibroblasts in Gastric Cancer Regulate Macrophage Polarization through RCN3 Pathway.

To explore the role and molecular mechanism of cancer-associated fibroblasts (CAFs) in the tumor microenvironment of gastric cancer (GC). The expression of CAFs in GC patients was first assessed for abundance, and survival analysis was performed. Subsequently, The Cancer Genome Atlas (TCGA) data were used for differential analysis, survival analysis, and EPIC analysis, while single-cell data (GSE183904) were downloaded for differential analysis of CAFs. Clinical data pooling, univariate and multivariate Cox analysis, and immunofluorescence were carried out on clinical GC tissue samples to explore RCN3 expression within patient CAFs. Western blot and quantitative polymerase chain reaction (qPCR) were used to detect the expression of RCN3. The relationship between RCN3, PCSK6, and STAT1 was explored by chromatin immunoprecipitation (CHIP) experiments, and the effects of the genes on macrophage polarization were detected by detecting biomarkers of biological M1/M2. CAFs in GC were found to be significantly higher compared to the normal group. Revealing the results of TCGA differential analysis, it was observed that GC exhibited a substantial upregulation in the expression levels of RCN3. The clinical statistics indicate a positive correlation between an elevated level of RCN3 expression and the T-stage classification of tumor size. In addition, RCN3 was found to have a significant impact on the overall survival of patients with gastric cancer, acting as an independent prognostic indicator. Analysis of single-cell data showed high expression of PCSK6 in macrophages, and immunofluorescence staining of samples from GC patients showed increased expression of PCSK6 on the cell membranes of macrophages in GC tissues. The subsequent cellular experiments confirmed RCN3 protein can regulate the expression of PCSK6, and PCSK6 regulates macrophage polarization through STAT1. CAFs regulate macrophage polarization through the RCN3/PCSK6/STAT1 pathway in GC.

Comprehensive landscape of integrator complex subunits and their association with prognosis and tumor microenvironment in gastric cancer.

The integrator complex (INT) is a multiprotein assembly in gene transcription. Although several subunits of INT complex have been implicated in multiple cancers, the complex's role in gastric cancer (GC) is poorly understood. The gene expressions, prognostic values, and the associations with microsatellite instability (MSI) of INT subunits were confirmed by GEO and The Cancer Genome Atlas (TCGA) databases. cBioPortal, GeneMANIA, TISIDB, and MCPcounter algorithm were adopted to investigate the mutation frequency, protein-protein interaction network, and the association with immune cells of INT subunits in GC. Additionally, in vitro experiments were performed to confirm the role of INTS11 in pathogenesis of GC. The mRNA expression levels of INTS2/4/5/7/8/9/10/11/12/13/14 were significantly elevated both in GSE183904 and TCGA datasets. Through functional enrichment analysis, the functions of INT subunits were mainly associated with snRNA processing, INT, and DNA-directed 5'-3' RNA polymerase activity. Moreover, these INT subunit expressions were associated with tumor-infiltrating lymphocytes and MSI in GC. In vitro experiments demonstrated that knockdown of the catalytic core INTS11 in GC cells inhibits cell proliferation ability. INTS11 overexpression showed opposite effects. Our data demonstrate that the INT complex might act as an oncogene and can be used as a prognosis biomarker for GC.

Adipocytes impact on gastric cancer progression: Prognostic insights and molecular features.

Adipocytes, especially adipocytes within tumor tissue known as cancer-associated adipocytes, have been increasingly recognized for their pivotal role in the tumor microenvironment of gastric cancer (GC). Their influence on tumor progression and patient prognosis has sparked significant interest in recent research. The main objectives of this study were to investigate adipocyte infiltration, assess its correlation with clinical pathological features, develop a prognostic prediction model based on independent prognostic factors, evaluate the impact of adipocytes on immune cell infiltration and tumor invasiveness in GC, and identify and validate genes associated with high adipocyte expression, exploring their potential diagnostic and prognostic value. To explore the relationship between increased adipocytes within tumor tissue and prognosis in GC patients as well as the associated mechanisms and potential biomarkers, using public databases and clinical data. Using mRNA microarray datasets from the Gene Expression Omnibus database and clinical samples from Jiangsu Provincial Hospital, survival and regression analyses were conducted to determine the relevant prognostic factors in GC. Feature gene selection was performed using least absolute shrinkage and selection operator and support vector machine recursive feature elimination algorithms, followed by differential gene expression analysis, gene ontology, pathway analysis, and Gene Set Enrichment Analysis. Immune cell infiltration was analyzed using the CIBERSORT algorithm. Tumor adipocyte infiltration correlated with poor prognosis in GC, leading to the development of a highly accurate and discriminative prognostic prediction model. Key genes, ADH1B, SFRP1, PLAC9, and FABP4, were identified as associated with high adipocyte expression in GC. The diagnostic and prognostic potential of these identified genes was validated using independent datasets. Downregulation of immune cells was observed in GC with high adipocyte expression. GC with high intratumoral adipocyte expression demonstrated aggressive tumor biology and a poorer prognosis. The genes ADH1B, SFRP1, PLAC9, and FABP4 have been identified as holding diagnostic and prognostic significance in GC. These findings strongly support the use of adipocyte expression as a valuable indicator of tumor invasiveness and anticipated patient outcomes in GC.

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.

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.

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 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 < 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 < 0.25 and p < 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 < 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.

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.

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.

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.

Enhanced Photodynamic Therapy Synergizing with Inhibition of Tumor Neutrophil Ferroptosis Boosts Anti-PD-1 Therapy of Gastric Cancer.

For tumor treatment, the ultimate goal in tumor therapy is to eliminate the primary tumor, manage potential metastases, and trigger an antitumor immune response, resulting in the complete clearance of all malignant cells. Tumor microenvironment (TME) refers to the local biological environment of solid tumors and has increasingly become an attractive target for cancer therapy. Neutrophils within TME of gastric cancer (GC) spontaneously undergo ferroptosis, and this process releases oxidized lipids that limit T cell activity. Enhanced photodynamic therapy (PDT) mediated by di-iodinated IR780 (Icy7) significantly increases the production of reactive oxygen species (ROS). Meanwhile, neutrophil ferroptosis can be triggered by increased ROS generation in the TME. In this study, a liposome encapsulating both ferroptosis inhibitor Liproxstatin-1 and modified photosensitizer Icy7, denoted LLI, significantly inhibits tumor growth of GC. LLI internalizes into MFC cells to generate ROS causing immunogenic cell death (ICD). Simultaneously, liposome-deliver Liproxstatin-1 effectively inhibits the ferroptosis of tumor neutrophils. LLI-based immunogenic PDT and neutrophil-targeting immunotherapy synergistically boost the anti-PD-1 treatment to elicit potent TME and systemic antitumor immune response with abscopal effects. In conclusion, LLI holds great potential for GC immunotherapy.

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.

Regulation of regulatory T cells and tumor-associated macrophages in gastric cancer tumor microenvironment.

Despite advancements in the methods for prevention and early diagnosis of gastric cancer (GC), GC continues to be the fifth in incidence among major cancers and the third most common cause of cancer-related death. The therapeutic effects of surgery and drug treatment are still unsatisfied and show notable differences according to the tumor microenvironment (TME) of GC. Through screening Pubmed, Embase, and Web of Science, we identified and summarized the content of recent studies that focus on the investigation of Helicobacter pylori (Hp) infection, regulatory T cells (Tregs), and tumor-associated macrophages (TAMs) in the TME of GC. Furthermore, we searched and outlined the clinical research progress of various targeted drugs in GC treatment including CTLA-4, PD-1\PD-L1, and VEGF/VEGFR. In this review, the findings indicate that Hp infection causes local inflammation and leads to immunosuppressive environment. High Tregs infiltration in the TME of GC is associated with increased induction and recruitment; the exact function of infiltrated Tregs in GC was also affected by phenotypes and immunosuppressive molecules. TAMs promote the development and metastasis of tumors, the induction, recruitment, and function of TAMs in the TME of gastric cancer are also regulated by various factors. Discussing the distinct tumor immune microenvironment (TIME) of GC can deepen our understanding on the mechanism of cancer immune evasion, invasion, and metastasis, help us to reduce the incidence of GC, and guide the innovation of new therapeutic targets for GC eventually.

Cross-talk of Three Molecular Subtypes of Telomere Maintenance Defines Clinical Characteristics and Tumor Microenvironment in Gastric Cancer.

Background: Telomere maintenance takes part in the regulation of gastric cancer (GC) pathogenesis and is essential for patients' clinical features. Though the correlation between a single telomere maintenance-related gene and GC has previously been published, comprehensive exploration and systematic analysis remain to be studied. Our study is aimed at determining telomere maintenance-related molecular subtypes and examining their role in GC. Methods: By analyzing the transcriptome data, we identified three telomere maintenance-associated clusters (TMCs) with heterogeneity in clinical features and tumor microenvironment (TME). Then, we screened five prognostic telomere maintenance-related genes and established corresponding TM scores. Additionally, the expression level and biological function of tubulin beta 6 class V (TUBB6) were validated in GC tissues and cells. Results: TMC1 was correlated with EMT and TGF-beta pathway and predicted low tumor mutation burden (TMB) as well as bad prognostic outcomes. TMC3 was associated with cell cycle and DNA repair. In terms of TMB and overall survival, TMC3 exhibited opposite results against TMC1. Significant heterogeneity was observed between TMCs. TUBB6 was upregulated and could promote GC proliferation, migration, and invasion. Conclusion: Altogether, combining bioinformatics and functional experiments, we identified three molecular subtypes based on telomere maintenance-associated genes in GC, which could bring new ideas and novel biomarkers to the clinic.

Prognostic analysis of patients with gastric cancer based on N6-methyladenosine modification patterns and tumor microenvironment characterization.

Cancers arise from genetic and epigenetic abnormalities that affect oncogenes and tumor suppressor genes, compounded by gene mutations. The N6-methyladenosine (m6A) RNA modification, regulated by methylation regulators, has been implicated in tumor proliferation, differentiation, tumorigenesis, invasion, and metastasis. However, the role of m6A modification patterns in the tumor microenvironment of gastric cancer (GC) remains poorly understood. In this study, we analyzed m6A modification patterns in 267 GC samples utilizing 31 m6A regulators. Using consensus clustering, we identified two unique subgroups of GC. Patients with GC were segregated into high- and low-infiltration cohorts to evaluate the infiltration proportions of the five prognostically significant immune cell types. Leveraging the differential genes in GC, we identified a "green" module via Weighted Gene Co-expression Network Analysis. A risk prediction model was established using the LASSO regression method. The "green" module was connected to both the m6A RNA methylation cluster and immune infiltration patterns. Based on "Module Membership" and "Gene Significance", 37 hub genes were identified, and a risk prediction model incorporating nine hub genes was established. Furthermore, methylated RNA immunoprecipitation and RNA Immunoprecipitation assays revealed that YTHDF1 elevated the expression of DNMT3B, which synergistically promoted the initiation and development of GC. We elucidated the molecular mechanism underlying the regulation of DNMT3B by YTHDF1 and explored the crosstalk between m6A and 5mC modification. m6A RNA methylation regulators are instrumental in malignant progression and the dynamics of tumor microenvironment infiltration of GC. Assessing m6A modification patterns and tumor microenvironment infiltration characteristics in patients with GC holds promise as a valuable prognostic biomarker.

Metabolic reprogramming involves in transition of activated/resting CD4+ memory T cells and prognosis of gastric cancer.

Little is known on how metabolic reprogramming potentially prompts transition of activated and resting CD4+ memory T cells infiltration in tumor microenvironment of gastric cancer (GC). The study aimed to evaluate their interactions and develop a risk model for predicting prognosis in GC. Expression profiles were obtained from TCGA and GEO databases. An immunotherapeutic IMvigor210 cohort was also enrolled. CIBERSORT algorithm was used to evaluate the infiltration of immune cells. The ssGSEA method was performed to assess levels of 114 metabolism pathways. Prognosis and correlation analysis were conducted to identify metabolism pathways and genes correlated with activated CD4+ memory T cells ratio (AR) and prognosis. An AR-related metabolism gene (ARMG) risk model was constructed and validated in different cohorts. Flow cytometry was applied to validate the effect of all-trans retinoic acid (ATRA) on CD4+ memory T cells. Since significantly inverse prognostic value and negative correlation of resting and activated CD4+ memory T cells, high AR level was associated with favorable overall survival (OS) in GC. Meanwhile, 15 metabolism pathways including retinoic acid metabolism pathway were significantly correlated with AR and prognosis. The ARMG risk model could classify GC patients with different outcomes, treatment responses, genomic and immune landscape. The prognostic value of the model was also confirmed in the additional validation, immunotherapy and pan-cancer cohorts. Functional analyses revealed that the ARMG model was positively correlated with pro-tumorigenic pathways. In vitro experiments showed that ATRA could inhibit levels of activated CD4+ memory T cells and AR. Our study showed that metabolic reprogramming including retinoic acid metabolism could contribute to transition of activated and resting CD4+ memory T cells, and affect prognosis of GC patients. The ARMG risk model could serve as a new tool for GC patients by accurately predicting prognosis and response to treatment.