Biology subjects

Santos da Silva, V. C.

Publications and source records attributed to Santos da Silva, V. C..

7 recordsLinked to original sources

bioRxiv2025

Transcriptional Signatures of Field Cancerization in Gastric Cancer

The high rate of local recurrence in gastric adenocarcinoma (GA) suggests that carcinogenesis is not a focal event but a field-wide process. This phenomenon, known as "field cancerization," posits that histologically normal peritumoral tissue is, in fact, a pre-neoplastic field harboring incipient molecular alterations that confound genomic studies using it as a normal control. To overcome this limitation, we performed a three-way comparative transcriptomic analysis of tumor, peritumoral, and true-normal gastric tissues using a deep learning framework. We identified a stable 138-gene signature established within the peritumoral field and conserved in the tumor, which was absent in healthy controls. Within this signature, three key COSMIC-listed driver genes were highlighted: the Hippo pathway component FAT4 and the p53-inhibitor MDM4 were upregulated, while the EMT-suppressor NDRG1 was repressed. Co-expression analysis revealed a dynamic rewiring of these drivers, with a significant positive correlation between FAT4 and MDM4 emerging exclusively in the peritumoral field. In contrast, a negative correlation between FAT4 and NDRG1 was observed specifically in the tumor context. In public cohorts, high expression of FAT4 and MDM4 was significantly associated with poor patient prognosis, whereas NDRG1 showed no prognostic association. Critically, the prognostic power of MDM4 was validated in our local patient cohort. Our findings demonstrate that the peritumoral field is a molecularly distinct state in gastric carcinogenesis, characterized by a metabolic shift, and identify FAT4 and MDM4 as key drivers of this early transition, with significant potential as prognostic biomarkers.

genetics↗

bioRxiv2025

Dietary Patterns and Gene Expression Profiles in Gastric Adenocarcinoma Patients from the Northern Region of Brazil

BackgroundGastric adenocarcinoma (GA) remains a major public health concern worldwide, with incidence influenced by demographic, socioeconomic, and lifestyle factors. Diet is a modifiable risk factor that can shape tumor biology, potentially affecting gene expression and the tumor microenvironment. Understanding how dietary patterns correlate with molecular signatures in GA may provide insights for preventive and therapeutic strategies. MethodsThis retrospective, cross-sectional, analytical study included 60 patients diagnosed with gastric adenocarcinoma and treated at the Joao de Barros Barreto University Hospital, Para, Brazil. Structured questionnaires collected sociodemographic, lifestyle (smoking and alcohol), clinical, and dietary data. Dietary patterns were analyzed according to the Brazilian Ministry of Health guidelines. A subset of 16 patients was selected for gene expression profiling to evaluate correlations between dietary exposure and molecular alterations. ResultsThe patient cohort exhibited a predominance of males (56.7%) and older adults (>60 years), often from socioeconomically disadvantaged backgrounds. Dietary analysis revealed insufficient intake of fruits, vegetables, and legumes, alongside high consumption of ultraprocessed foods, especially sugar-sweetened beverages. Gene expression analysis identified 48 differentially expressed genes between patients with lower (LEDRF) and higher (HEDRF) dietary risk exposure. Six genes with potential biological relevance were highlighted: MAGEA3, IL6, HCAR2, NLRP4, PGA3, and CTCFL. MEFDR patients showed overexpression of MAGEA3, IL6, and HCAR2, associated with cell proliferation, inflammation, and tumor microenvironment remodeling. DiscussionThe results suggest that dietary patterns may modulate gene expression and influence the tumor microenvironment in gastric adenocarcinoma. Diets rich in ultraprocessed foods and sugar may promote a pro-inflammatory and pro-oxidant microenvironment, while consumption of fruits, vegetables, and bioactive compounds appears protective, potentially regulating epigenetic, metabolic, and immunological pathways. The study underscores the importance of integrated approaches combining nutritional intervention and molecular profiling to better understand GA progression and identify potential therapeutic targets.

cancer biology↗

bioRxiv2025

Transcriptomic Mutational Profiling of Gastric Adenocarcinoma in Northern Brazil

Gastric cancer (GC) remains among the neoplasms with the worst prognosis, partly due to its biological heterogeneity and the scarcity of robust biomarkers. The characterization of mutational profiles from transcripts can reveal specific tumor signatures and point to therapeutic targets. This study investigated the landscape of mutations expressed in 102 samples of gastric adenocarcinoma from northern Brazil, which were sequenced using NGS. Readings were aligned to the reference genome using STAR (two-pass mode), and variants were called with GATK and VarDict. Annotations and impact predictions were generated using VEP, SIFT, and PolyPhen. We identified >90,000 variants; among the most frequently mutated genes, FTH1 stood out. The mutational profile was described using maftools, and signatures were inferred with MutationalPatterns. We observed a predominant distribution of SNVs, with C>T transitions as the most common event, in addition to patterns compatible with signatures related to replication damage and DNA repair. To mitigate biases inherent to RNA-seq, we applied filters for coverage, strand bias, and RNA editing hotspots. Together, the data outline a regional landscape of mutations expressed in GC and reinforce the usefulness of the transcriptome for prioritizing biomarkers and functional hypotheses that may guide genomic validations and subsequent clinical studies.

bioinformatics↗

bioRxiv2025

Interspecies Functional Divergence: The Microbiome's Role in FLOT Response e Across Gastric Cancer Subtypes

BackgroundGastric adenocarcinoma exhibits marked molecular and histological heterogeneity, which is reflected in distinct patterns of progression, therapeutic response, and prognosis. Although the FLOT regimen (5-fluorouracil, leucovorin, oxaliplatin, and docetaxel) represents the current standard for perioperative chemotherapy, its systemic effects on the tumor microenvironment, including the associated bacterial microbiome and host gene expression, remain poorly understood. MethodsThis study investigated the effects of FLOT on the functional and ecological structure of intestinal and diffuse subtype gastric tumors by assessing its simultaneous influence on the human transcriptome, the bacterial transcriptome, and inter-kingdom interactions. We analyzed 55 tumor samples (37 intestinal subtype; 18 diffuse subtype) and explored potential genetic-functional interactions between the bacterial microbiome and the human genome. ResultsThe results reveal a highly specific functional pattern in the diffuse subtype, absent in the intestinal subtype, demonstrating a unique ecological-transcriptional plasticity mediated by the microbiota under chemotherapeutic pressure. The interaction network was dominated by high-magnitude positive correlations. Notably, the bacterial gene leuS showed a robust association with the human gene HCN1 and processes such as potassium ion transmembrane transport, membrane depolarization, and regulation of postsynaptic membrane potential, indicating a coordinated activation of ion channels and neuroepithelial circuits. Bacterial species including Bacteroides uniformis, Faecalibacterium prausnitzii, Butyrivibrio crossotus, Prevotella copri, and Simiaoa sunii also converged functionally on HCN1. Additionally, bacterial genes mfd, nifJ, secY, rplF, and tet(Q) were associated with pathways related to cell adhesion, epithelial proliferation, membrane potential control, and synaptic transduction. DiscussionIntegrative analysis reveals that the FLOT regimen acts as a systemic remodeler of the gastric tumor microenvironment, exerting distinct effects according to the histological subtype. While the intestinal subtype responds more aligned with the cytotoxic goals of chemotherapy, the diffuse subtype exhibits a functional plasticity that favors the emergence of adaptive and possibly pro-tumoral phenotypes. We propose a mechanistic model where in chemotherapy selectively reshapes the microbial ecosystem, which in turn modulates host functional circuits, directly influencing tumor behavior. These findings open perspectives for combined therapeutic strategies that include targeted modulation of the microbiome as an adjuvant to chemotherapy.

cancer biology↗

bioRxiv2025

FERROPTOSIS GENE SIGNATURES REVEAL DISTINCT REGULATORY LANDSCAPES IN GASTRIC ADENOCARCINOMA AND OTHER TISSUES

BackgroundGastric adenocarcinoma (GAC) remains one of the most lethal malignancies worldwide, with late-stage diagnosis and limited therapeutic options. Ferroptosis, a regulated form of cell death driven by iron-dependent lipid peroxidation, has emerged as a promising target for overcoming tumor resistance mechanisms. This study aimed to characterize the transcriptional landscape of ferroptosis-related genes in GAC, comparing tumor, peritumoral, metaplastic, and normal gastric tissues. MethodsRNA-Seq was performed on 385 biopsied samples from patients treated at the Joao de Barros Barreto University Hospital. Differential expression analysis was conducted using DESeq2, and genes related to ferroptosis were identified based on FerrDb V2 annotations. Visualization included volcano plots, DAPC clustering, heatmaps, and gene dominance scoring. ResultsGAC samples showed a distinct ferroptotic expression signature, with simultaneous upregulation of key promoters (e.g., CDKN2A, NOX4, EGFR, IL6) and suppressors (e.g., HSPB1, SCD, NUPR1, GDF15). Notably, the tumor tissue exhibited a net dominance of ferroptosis-inhibitory genes, suggesting an adaptive response to oxidative stress. Adjacent tissues showed partial overlap with tumor profiles, while metaplastic tissue displayed a hybrid signature with selective suppression of ferroptosis. Normal mucosa exhibited dominant expression of promoters, contrasting with the tumors anti-ferroptotic phenotype. ConclusionThe transcriptional heterogeneity and regulatory imbalance of ferroptosis-related genes in GAC support its role as a potential therapeutic axis. These findings provide molecular insights for biomarker discovery and ferroptosis-targeted strategies in gastric cancer.

cancer biology↗

bioRxiv2025

Integrated Expression Analysis of C-MYC Oncogene-Associated Pathways in Gastric Adenocarcinoma and its Correlation with Clinicopathological Factors

BackgroundThe C-MYC oncogene is a well-established driver of gastric carcinogenesis, yet the integrated expression pattern of its complex regulatory network and its clinical implications in gastric adenocarcinoma (GAC) remain to be fully elucidated. This study aimed to perform an integrated bioinformatic analysis of C-MYC and its associated pathways in a cohort of GAC patients to delineate its expression profile, assess its potential as a biomarker, and correlate its patterns with clinicopathological factors such as Lauren classification and neoadjuvant treatment status. MethodsThe study included transcriptome data from 74 GAC tumor samples and 68 normal gastric tissue samples. Following RNA sequencing, a comprehensive bioinformatic analysis was conducted on a curated list of 21 C-MYC-associated genes. The methodology included differential expression analysis (DESeq2), unsupervised hierarchical clustering, Principal Component Analysis (PCA), and Receiver Operating Characteristic (ROC) curve analysis to evaluate diagnostic performance. Gene expression levels were also statistically correlated with Lauren histological subtypes and neoadjuvant therapy status using the Wilcoxon rank-sum test. ResultsThe analysis revealed a profound dysregulation of the C-MYC network in GAC. While MYC itself was significantly upregulated, its transcriptional antagonists, particularly MXD4 and MXD3, were the most significantly downregulated genes. This gene signature robustly separated tumor from normal tissues in both hierarchical clustering and PCA. ROC analysis demonstrated the outstanding diagnostic potential of several genes, with MXD4 achieving a perfect Area Under the Curve (AUC) of 1.00, surpassing the diagnostic value of MYC (AUC=0.86). Stratification by Lauren classification showed that MYC and its stability regulator PTBP1 were significantly more expressed in the intestinal subtype, whereas the repressors MXD3 and MXI1 were higher in the diffuse subtype. No significant expression differences were observed based on neoadjuvant treatment status. ConclusionGastric adenocarcinoma is characterized by a coordinated dysregulation of the C-MYC network, marked by both oncogene activation and a concurrent loss of its key transcriptional repressors. The profound downregulation of antagonists like MXD4 serves as an exceptionally accurate molecular signature for GAC, suggesting its potential as a diagnostic biomarker superior to MYC alone. The divergent expression patterns between Lauren subtypes highlight distinct molecular pathobiology and may have implications for targeted therapies

genetics↗

bioRxiv2025

Unmasking Epstein-Barr Role in Gastric Carcinogenesis: A Gene Expression Approach to Virus-Positive Tumors

Human gammaherpesvirus 4 or Epstein-Barr virus (EBV) is an oncogenic virus linked to malignancies like gastric adenocarcinoma. Notably, EBV infection induces genetic and epigenetic modifications that play a crucial role in oncogenesis and tumor progression, underscoring the importance of analyzing viral gene expression in the context of gastric cancer (GC) to elucidate its unique characteristics. This study aimed to perform a molecular characterization of EBV gene expression using next-generation sequencing (NGS). The analysis included human gene expression patterns in EBV-positive and EBV-negative samples and the expression of viral genes in EBV-positive samples. The study received approval from the Ethics and Research Committee of Joao de Barros Barreto University Hospital under reference number 47580121.9.0000.5634. It utilized 76 tumor tissue samples from patients with gastric cancer who had undergone surgical resection, and both fresh and paraffin-embedded samples were gathered for total RNA sequencing (RNA-seq) and in situ hybridization (ISH). The RNA-seq was conducted in a pair-end manner on the NextSeq(R) platform (Illumina(R), US). The NextSeq(R) 500 MID Output V2 kit - 150 cycles (Illumina(R)) were utilized following the manufacturers instructions. ISH targeting RNA-1 of EBER1 (Y5200, DAKO, Carpinteria) was performed using the automated Dako system. Molecular characterization was conducted using the Kraken2 software. Subsequently, to elucidate the mechanisms through which EBV may influence gastric cancer, we analyzed the patterns of human gene expression in EBV-positive and EBV-negative samples. Of the 76 samples, 8 were classified as EBV-positive according to the applied methodology. Our analysis identified approximately 834 differentially expressed genes, 92 of which exhibited an AUC > 0.85. These genes are implicated in tumor progression, cellular metabolism, and both innate and adaptive immune responses. Additionally, viral genes expressed in the positive samples were evaluated, and we found manifestations of both lytic phase and latent phase genes. Finally, our study presents an efficient strategy for molecular classification of EBV-positive gastric cancer based on NGS and shows the effects of EBV on human gene expression. Author summaryIn our study, we explored how EBV influences the development of stomach cancer. EBV is a virus known to be linked to various cancers, including gastric cancer, and it can alter the behavior of both human and viral genes within infected cells. To investigate this, we analyzed tissue samples from 76 patients with stomach cancer, focusing on differences between samples with and without EBV. Using advanced sequencing technology, we identified over 800 genes that behave differently in EBV-positive cancers. These genes are involved in critical processes like how cells grow, how the immune system responds, and how energy is produced within cells. We also examined which EBV genes were active in the cancer samples and found evidence of both dormant and active phases of the virus. Our work demonstrated how EBV may contribute to stomach cancer and suggests new ways to classify and understand this disease. By uncovering these details, we hope to pave the way for more targeted treatments in the future.

cancer biology↗