Chunhui Sun

Régulation des réponses calciques et de la cytotoxicité par l’effecteur de type III IpgD durant l’invasion des cellules épithéliales par Shigella: Shigella, l’agent de la dysenterie bacillaire, envahit la muqueuse colique, causant une inflammation intense et destruction tissulaire. Afin de promouvoir l’infection, Shigella injecte des facteurs de virulence par l’intermédiaire d’un appareil de sécrétion de type III (T3SS) dans les cellules hôte, qui permettent la réorganisation du cytosquelette d’actine, régulent l’inflammation et l’intégrité du tissu. Parmi ces facteurs injectés par la bactérie, la protéine IpgD agit comme une phosphatidylinositol (PI) (4,5) bisphosphate phosphatase déphosphorylant le PIP2 en PI(5)P. L’hydrolyse du PI(4,5)P2 favorise la polymérisation de l’actine durant l’invasion des cellules épithéliales et régule négativement la migration des lymphocytes T. Il a également été démontré que le PI(5)P produit par IpgD active la voie de survie cellulaire dépendant de la PI(3) kinase et de la kinase AKT. Mon projet de thèse a pour but de caractériser le rôle d’IpgD dans les contrôles des réponses calciques durant l’invasion des cellules épithéliales par Shigella. Nous avons montré qu’IpgD limite le recrutement de récepteurs à l’inositol-triphosphate (InsP3) au site d’invasion. Des expériences d’imagerie calcique indiquent que durant les étapes précoces de l’invasion, IpgD favorise l’émission de réponses locales aux sites d’invasion de Shigella et limite celle de réponses globales. Des expériences de recouvrement de fluorescence après photo-blanchiment (FRAP) indiquent que les foyers d’invasion induits par le mutant ipgD montrent une diffusion moins restreinte que celle observée dans les foyers induits par la souche sauvage. Des études de modélisation supportent la notion qu’en limitant la production locale d’InsP3 et sa diffusion aux sites d’invasion, IpgD participe au confinement des réponses calciques locales en empêchant l’émission de réponses globales. Nous avons montré que lors de cinétiques d’infection prolongée, IpgD inhibe les réponses calciques globales dépendant de l’InsP3 induites par Shigella ou par des agonistes. L’inhibition de ces réponses conduit à un retard de l’activation de la calpaine, de la dégradation de la taline, une protéine des adhérences focales, ainsi que de la mort des cellules durant la réplication bactérienne intracellulaire. Nos résultats indiquent qu’IpgD est un effecteur critique de Shigella permettant de réguler la transition des réponses calciques locales vers des réponses globales et préservant les cellules infectées de la mort liée à une perte d’adhérence.

Gastrointestinal (GI) cancers represent a significant global health burden, characterized by high incidence, poor prognosis, and limited response to monotherapies. The advent of bispecific antibodies (BsAbs) has introduced a novel therapeutic paradigm, enabling dual targeting of tumor-associated antigens and immune effectors to enhance antitumor immunity. This review provides a comprehensive overview of recent advances in bsAb-based immunotherapy across major GI malignancies, including colorectal, gastric, pancreatic, biliary tract, esophageal, and liver cancers. We summarize key molecular targets and highlight representative clinical candidates such as CEA-TCB and RG7802. The discussion extends to innovative strategies involving BsAbs in modulating the immunosuppressive tumor microenvironment and overcoming resistance mechanisms. Furthermore, we explore promising combination therapies involving BsAbs with chemotherapy and immune checkpoint inhibitors (ICIs). The role of artificial intelligence in target prediction and structure optimization is also examined, alongside the potential of personalized immune strategies. Despite promising therapeutic potential, BsAbs face challenges including cytokine release syndrome (CRS), on-target/off-tumor toxicity, tumor heterogeneity-driven resistance, and tumor microenvironment (TME). Current strategies to improve therapeutic index encompass affinity-tuned designs, conditional activation mechanisms, biomarker-driven patient stratification, combination therapies, and artificial intelligence (AI)-guided optimization, warranting continued interdisciplinary research efforts. We conclude by outlining future research directions and emphasizing the importance of interdisciplinary, multicenter collaborations to accelerate clinical translation and maximize the therapeutic potential of BsAbs in GI oncology. In summary, the aim of this study is to critically evaluate the current landscape of BsAb-based immunotherapy in gastrointestinal cancers, synthesizing emerging molecular targets, evaluating clinical trial outcomes, identifying key challenges limiting therapeutic efficacy, and proposing evidence-based strategies to optimize future BsAb development.

Background: Sigmoid colon cancer with spinal metastases is rare in distant metastasis. In addition, the prognosis of colon cancer patients with spinal metastases is extremely poor. In order to find effective therapeutic agents, we need to know the biological characteristics of such patients from related models.Methods: We collected sigmoid colon cancer tissue from a young female subject who was diagnosed with sigmoid colon cancer with multiple spinal metastases. We successfully established a sigmoid colon cancer organoid using this tissue and investigated drug screening in the patient. HE staining, immunohistochemistry, and DNA sequencing were utilized to compare the biological characteristics between the original tumor and the organoid. Furthermore, we investigated the drug screening of the sigmoid colon cancer organoid in vitro.Results: A colon cancer organoid from sigmoid colon cancer with spinal metastases was successfully established. The organoid culture maintained the morphological features, histological features, and genomic landscape of the corresponding sigmoid colon cancer cells. Moreover, we performed drug screening tests to evaluate the effects of chemotherapeutic drugs and targeted drugs.Conclusion: The sigmoid colon cancer organoid with spinal metastases was a favorable preclinical model to explore the clinicopathologic characteristics of colon cancer patients with spinal metastases.

Gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) are highly heterogeneous neoplasms of the gastrointestinal tract and pancreas. The objective of this study was to develop and verify a prediction nomogram for determining the overall survival rate of stage IV GEP-NENs. Data from 2139 stage IV GEP-NENs patients between 2010 and 2017 were extracted from the SEER database. Concordance index (C-index), calibration curve analysis, receiver operating curve (ROC) analysis, and decision curve analysis (DCA) were used to evaluate and validate the predictive performance of the nomogram. The difference in survival rates between the low-risk and high-risk groups was analyzed using the Kaplan-Meier method. Ten risk factors were integrated into the prognostic nomogram. The C-index (0.7961 in the training set and 0.801 in the validating set) and calibration curve analysis exhibited an excellent consistency between the two groups. The AUC value was 0.879, 0.857, and 0.839, respectively, for nomograms predicting 1-, 3-, and 5-year overall survival in the training set. In the validation set, AUC values were 0.859, 0.844, and 0.831 for nomograms predicting 1-, 3-, and 5-year overall survival. According to the DCA analysis, the nomogram offered significant clinical benefits. The scatter plot of risk score demonstrated that with the increase in risk score, the proportion of death also increased. In both training and validation sets, the Kaplan-Meier analysis displayed that patients in the high-risk group with stage IV GEP-NENs had a worse overall survival rate than patients in the low-risk group. A prognostic nomogram of stage IV GEP-NENs was established by integrating age, sex, differentiation, primary site, tumor size, surgery, chemotherapy, and bone, brain, and lung metastases. With further verification, the nomogram with favorable specificity, sensitivity, and added clinical benefit could help clinicians assess prognosis and provide treatment guidance for stage IV GEP-NENs patients.

Outer membrane vesicles (OMVs) are immunogenic self-adjuvanting vesicles produced by Gram-negative bacteria such as Pseudomonas aeruginosa and Yersinia pseudotuberculosis. While the effects of OMVs on different antigens immune stimulation are not clear. In this study, we constructed recombinant Yersinia pseudotuberculosis ΔlpxL strain,with pBlue-PcrV and pBlue-OprF/I, and then purified ΔlpxL rOMV_PcrV (rOMVyp2P)and ΔlpxL rOMV_OprF/I (rOMVyp2F) and analyzed its effect on immune response and protection against Pseudomonas aeruginosa PAO1 infection. The results showed that OMV assists in eliciting similar humoral immune responses to PcrV and OprF/I antigens. ΔlpxL rOMV_PcrV and ΔlpxL rOMV_OprF/I elicited Th1/Th2 balanced immune response, and higher IgM and IgA antibodies.However, there are differences in immune protection for the pulmonary. The survival rate of mice in ΔlpxL rOMV_PcrV group was 20%, which was significantly better than that in ΔlpxL rOMV_OprF/I group. ΔlpxL OMV_PcrV is better cooperation for Pseudomonas immune protection in lung.

Introduction: Gastric cancer (GC) is the fifth most common tumor, contributing to the third-highest number of cancer-related deaths. Hypoxia is a major feature of the tumor microenvironment. This study aimed to explore the influence of hypoxia in GC and establish a hypoxia-related prognostic panel.Methods: The GC scRNA-seq data and bulk RNA-seq data were downloaded from the GEO and TCGA databases, respectively. AddModuleScore() and AUCell() were used to calculate module scores and fractions of enrichment for hypoxia-related gene expression in single cells. Least absolute shrinkage and selection operator cox (LASSO-COX) regression analysis was utilized to build a prognostic panel, and hub RNAs were validated by qPCR. The CIBERSORT algorithm was adopted to evaluate immune infiltration. The finding of immune infiltration was validated by a dual immunohistochemistry staining. The TIDE score, TIS score and ESTIMATE were used to evaluate the immunotherapy predictive efficacy.Results: Hypoxia-related scores were the highest in fibroblasts, and 166 differentially expressed genes were identified. Five hypoxia-related genes were incorporated into the hypoxia-related prognostic panel. 4 hypoxia-related genes (including POSTN, BMP4, MXRA5 and LBH) were significantly upregulated in clinical GC samples compared with the normal group, while APOD expression decreased in GC samples. Similar results were found between cancer-associated fibroblasts (CAFs) and normal fibroblasts (NFs). A high hypoxia score was associated with advanced grade, TNM stage, N stage, and poorer prognosis. Decreased antitumor immune cells and increased cancer-promoting immune cells were found in patients with high hypoxia scores. Dual immunohistochemistry staining showed high expression of CD8 and ACTA2 in gastric cancer tissue. In addition, the high hypoxia score group possessed higher TIDE scores, indicating poor immunotherapy benefit. A high hypoxia score was also firmly related to sensitivity to chemotherapeutic drugs.Discussion: This hypoxia-related prognostic panel may be effective in predicting the clinical prognosis, immune infiltrations, immunotherapy, and chemotherapy in GC.