Identification and validation of key genes associated with pathogenesis and prognosis of gastric cancer

COL1A1-positive endothelial cells promote gastric cancer progression via the ANGPTL4-SDC4 axis driven by endothelial-to-mesenchymal transition

Gastric cancer (GC) is an aggressive and heterogeneous disease with poor survival outcomes. The progression of GC involves complex, multi-step processes. Endothelial cells (ECs) play a crucial role in tumor angiogenesis, proliferation, invasion, and metastasis, particularly through the process of endothelial-to-mesenchymal transition (EndoMT). However, the specific role and mechanisms of EndoMT in gastric cancer remain unclear. Based on 6 GC single-cell RNA-sequencing (scRNA-seq) cohorts (samples = 97), we established an EndoMT-related gene signature, termed EdMTS. Leveraging this gene signature, ssGSEA was applied to calculate sample scores across multiple bulk RNA-seq datasets, which include information on immunotherapy, metastasis, GC progression, and survival. Moreover, we applied the Monocle2 method to calculate cell pseudotime and used CellChat to analyze interactions between malignant and EC cells. We verified the molecular mechanism by multiple immunofluorescence and cell function experiments. Findings In this study, we established a single-cell atlas of ECs in GC and identified a subpopulation of COL1A1+ ECs that play a critical role in tumor progression and metastasis. These COL1A1+ ECs were significantly associated with worse clinical outcomes in GC patients. Further analysis revealed that COL1A1+ ECs originated from lymphatic ECs and underwent EndoMT through the upregulation of CEBPB, driving tumor invasiveness. Moreover, COL1A1+ ECs interacted with malignant cells via ANGPTL4-SDC4 axis, enhancing invasion and migration. These findings provide a deeper understanding of the role of COL1A1+ ECs in GC progression and highlight potential therapeutic targets for disrupting the EndoMT process in these cells to provide a benefit for GC patients.

Integration of Gastric Cancer RNA-Seq Datasets Along With PPI Network Suggests That Nonhub Nodes Have the Potential to Become Biomarkers

BACKGROUND

The breakthrough discovery of novel biomarkers with prognostic and diagnostic value enables timely medical intervention for the survival of patients diagnosed with gastric cancer (GC). Typically, in studies focused on biomarker analysis, highly connected nodes (hubs) within the protein-protein interaction network (PPIN) are proposed as potential biomarkers. However, this study revealed an unexpected finding following the clustering of network nodes. Consequently, it is essential not to overlook weakly connected nodes (nonhubs) when determining suitable biomarkers from PPIN.

METHODS AND RESULTS

In this study, several potential biomarkers for GC were proposed based on the findings from RNA-sequencing (RNA-Seq) datasets, along with differential gene expression (DGE) analysis, PPINs, and weighted gene co-expression network analysis (WGCNA). Considering the overall survival (OS) analysis and the evaluation of expression levels alongside statistical parameters of the PPIN cluster nodes, it is plausible to suggest that THY1, CDH17, TGIF1, and AEBP1, categorized as nonhub nodes, along with ITGA5, COL1A1, FN1, and MMP2, identified as hub nodes, possess characteristics that render them applicable as biomarkers for the GC. Additionally, insulin-like growth factor (IGF)-binding protein-2 (IGFBP2), classified as a nonhub node, demonstrates a significant negative correlation with both groups within the same cluster. This observation underscores the conflicting findings regarding IGFBP2 in various cancer studies and enhances the potential of this gene to serve as a biomarker.

CONCLUSION

The findings of the current study not only identified the hubs and nonhubs that may serve as potential biomarkers for GC but also revealed a PPIN cluster that includes both hubs and nonhubs in conjunction with IGFBP2, thereby enhancing the understanding of the complex behavior associated with IGFBP2.

The spatial and cellular portrait of transposable element expression during gastric cancer

Gastric Cancer (GC) is a lethal malignancy, with urgent need for the discovery of novel biomarkers for its early detection. I previously showed that Transposable Elements (TEs) become activated in early GC (EGC), suggesting a role in gene expression. Here, I follow-up on that evidence using single-cell data from gastritis to EGC, and show that TEs are expressed and follow the disease progression, with 2,430 of them being cell populations markers. Pseudotemporal trajectory modeling revealed 111 TEs associated with the origination of cancer cells. Analysis of spatial data from GC also confirms TE expression, with 204 TEs being spatially enriched in the tumor regions and the tumor microenvironment, hinting at a role of TEs in tumorigenesis. Finally, a network of TE-mediated gene regulation was modeled, indicating that ~ 2,000 genes could be modulated by TEs, with ~ 500 of them already implicated in cancer. These results suggest that TEs might play a functional role in GC progression, and highlights them as potential biomarker for its early detection.

Molecular Insight into Gastric Cancer Invasion-Current Status and Future Directions

Gastric cancer (GC) is one of the most common malignancies worldwide. There has been no efficient therapy for stage IV GC patients due to this disease's heterogeneity and dissemination ability. Despite the rapid advancement of molecular targeted therapies, such as HER2 and immune checkpoint inhibitors, survival of GC patients is still unsatisfactory because the understanding of the mechanism of GC progression is still incomplete. Invasion is the most important feature of GC metastasis, which causes poor mortality in patients. Recently, genomic research has critically deepened our knowledge of which gene products are dysregulated in invasive GC. Furthermore, the study of the interaction of GC cells with the tumor microenvironment has emerged as a principal subject in driving invasion and metastasis. These results are expected to provide a profound knowledge of how biological molecules are implicated in GC development. This review summarizes the advances in our current understanding of the molecular mechanism of GC invasion. We also highlight the future directions of the invasion therapeutics of GC. Compared to conventional therapy using protease or molecular inhibitors alone, multi-therapy targeting invasion plasticity may seem to be an assuring direction for the progression of novel strategies.