Gastric adenocarcinoma outside the esophagogastric junction is linked to Helicobacter pylori infection in 93% of cases, but it is now recognized that environmental factors such as the digestive microbiota influence carcinogenesis. The digestive microbiota is defined by all the microorganisms that colonize the digestive system. The improvement of sequencing techniques has made it possible to show that certain tumors contain intracellular bacteria and that these are specific to the origin of the tumours. A study describing the existence of intratumoral bacteria focused on 7 different types of tumors excluding gastric cancer. Gastric adenocarcinoma is a cancer with a poor prognosis whose treatment, based essentially on surgery associated with conventional chemo/radiotherapy, is not very effective with a 5-year survival rate of less than 20%. It is therefore essential to develop targeted and effective treatments. The objective of this project is to define whether there are intratumoral bacteria in gastric cancer. To carry out this project, tumors as well as the adjacent healthy mucosa of patients with gastric cancer will be collected. A tube of blood allowing the isolation of any circulating tumor cells will also be taken. From this material, the presence of intratumoral bacteria will be determined by immunohistochemistry targeting components of the bacterial wall and by real-time quantitative PCR targeting the gene coding for 16S ribosomal RNA. In a second step, the characterization of the intratumoral microbiota will be carried out by multiplexed sequencing of the gene coding for 16S rDNA. The main judgment criterion will correspond to the observation of differences between the tumor microbiota and that of the adjacent healthy tissue. The different bacterial signatures that we will characterize could serve as biomarkers, especially if a particular microbiota is identified in circulating tumor cells. Biomarkers may also be useful in healing if a specific microbiota is identified based on tumor classification. Ultimately, this study will allow the characterization of the intratumoral microbiota in gastric cancer. We will obtain data that will allow us to set up the use of microbiota analysis as biomarkers and as a tool for personalized medicine in gastric cancer.

Gastric cancer (GC) is the 4th leading cause of cancer death worldwide. Team 1 identified and characterized cancer stem cells (CSCs) driving tumor initiation and chemoresistance in GC, including a mesenchymal subpopulation of CSCs detected as circulating tumor cells (CTCs) and metastatic. Dissemination of CTCs is particularly inefficient, and only a fraction can survive and act as metastasis initiating cells (MIC). These CTCs are detected alone or associated with pro-tumor immune cells such as neutrophils and/or immunosuppressive myeloid cells (MDSC). Team 2 extensively investigated the multiple tumor promoting functions of MDSCs.

Our hypothesis is that MDSCs can associate with CTCs, promote the properties of CSCs, protect MICs in the blood and promote their metastatic seeding. This project aims: 1) to identify biomarkers and signaling pathways of CSCs/MICs and 2) to explore, model and target CTCs/myeloid cell interactions and their impacts on the phenotype, tumorigenic, metastatic and resistance properties of CSCs/ MIC. Methods: cell lines and xenografts, liquid biopsies (CTC), myeloid cell/CSC cocultures, omics, bioinformatics, in vitro functional studies and xenografts, patient tissues.

The results of this project will lead to 1) the identification of new markers of GC CSCs/MICs for diagnostic, prognostic and therapeutic purposes, 2) the characterization of immune cells forming clusters with CTCs allowing to decipher and target their promoting action of CSC/MIC properties, 3) identifying new diagnostic and prognostic tools and developing innovative therapeutic strategies targeting CSC/MIC-MDSC interactions in the GC.

This project is carried out in collaboration with the team of Pr. Nicolas Larmonier, ImmunoConcEpt CNRS 5134, University of Bordeaux, and is financially supported by the Impulsion Newmoon network and the ITMO Cancer Aviesan Inserm.

1. pylori can induce gastric MALT lymphoma because of constant stimulation of antigen presentation leading to B cell expansion. Our working hypothesis is that a Helicobacter/Escherichia coli-coinfection promotes gastric lymphomagenesis.

The gastric and intestinal microbiota will be explored. Bacteriological, histological, molecular and metagenomic analyzes will allow us to answer several questions:

-does E. coli infection favor Helicobacter-induced gastric lymphomagenesis?

-does E. coli infection influence the gastric inflammatory response?

-are the virulence factors of E. coli, in particular colibactin, involved in these processes?

Our experimental approaches by metagenomics will allow to identify the nature of taxa and or functions associated with these microbiota modifications.

In perspective, it will be of major interest to validate the taxonomic and functional modifications observed within the microbial community in murine model, in biopsies of patients suffering from gastric MALT lymphoma.

Collaborations: Pr MJ Blaser, Rutgers University, New Jersey; Pr R Bonnet, CHU Clermont Ferrand ;  Pr A Amiot, Hôpital Henri Mondor, Créteil, and Hôpital Saint Antoine, Paris-APHP; Pr B Huard, TRAIG, TIMC-IMAG, UMR 5525, university Grenoble-Alpes, La Tronche, France.

Gastric cancer is the 5th most common diagnosed cancer and the 4th cause of cancer-related deaths worldwide according to the latest report of the International Agency for Research on Cancer . Gastric carcinoma are more often diagnosed at an advanced stage, with limited therapeutic options and a high rate of recurrence post treatment, leading to a poor 5-years overall survival. Helicobacter pylori (H. pylori) is a gram-negative bacterium that colonizes the human stomach. Epidemiological surveys estimate that chronic infection by this bacteria constitutes is the main causative agent of gastric cancer . Helicobacter infection induces changes of the gastric mucosa leading over time to invasive carcinoma in approximately 1% of the cases. A better understand of the early phases of mucosal changes caused by chronic Helicobacter infection and leading to carcinogenesis is essential to inhibit or reverse such changes and prevent transformation. The recent characterization of gastro-intestinal tuft cells has opened up novel opportunities in the field of gastric cancer biology. The team of P Jay (IGF Montpellier) discovered, together with others, the first function of intestinal tuft cells and their immune regulatory properties. More recently, Team 4 and P. Jay’s team established a collaboration to investigate the role of tuft cells in the gastric physiopathology following Helicobacter infection, using a mouse model that specifically lacks tuft cells. The main objectives of this collaborative project are (1) to discover the mechanisms involved in the pro-inflammatory and pro-tumoral properties of gastric tuft cells using relevant innovative mouse models, and (2) to establish how our findings apply to the human disease, and whether the mechanisms identified in mouse models may constitute attractive drug targets or useful biomarkers. This collaborative project involving P. Jay’s team in Montpellier and C. Varon’s team 4 in Bordeaux is supported by a national grant from the Association pour la Recherche contre le Cancer (labellisation de programme ARC 2021-2024).

We are frequently exposed to infection with genotoxin-producing bacteria from the gut microbiota, such as cytolethal distending toxin (CDT) and colibactin.

These toxins cause severe DNA damage in host cells, well-known risk factor of cancer development and progression.

We are investigating the role of the bacterial genotoxin CDT in digestive carcinogenesis: epithelial to mesenchymal transition, autophagy, and cytoskeleton remodeling to establish the proof of the causal role of CDT in cancer to prove its carcinogenicity.

Gastric adenocarcinoma is a cancer with a poor prognosis whose treatment, based essentially on surgery associated with conventional chemo/radiotherapy, is not very effective with a 5-year survival rate of less than 20%. Gastric tumors are heterogeneous and composed of cancer stem cells (CSC) responsible for tumor initiation, growth, dissemination and resistance to treatment. It is crucial to be able to find targeted therapies in order to increase the effectiveness of treatments. The main cause of gastric cancer is chronic infection with the bacterium Helicobacter pylori, which induces a series of pre-neoplastic changes in the gastric mucosa leading to the emergence of CSC. It has recently been demonstrated that the Hippo/YAP/TEAD signaling pathway is involved in controlling the properties of CSCs in breast and colon cancers. This signaling pathway is controlled by various upstream factors, including the Leukemia Inhibitory Factor (LIF) receptor (LIFR). The Hippo/YAP/TEAD pathway has recently been described in gastric cancer and we demonstrated that oncogenic effectors YAP/TAZ/TEAD are activated in response to H. pylori infection and lead to the emergence of gastric SCCs ( Molina-Castro et al, CMGH 2019, Tiffon et al, Cells 2020) and control their tumorigenic properties. We recently demonstrated that LIF treatment suppresses the ability of LIFR-expressing gastric cancer cells to form tumorspheres in vitro and decreases CD44 expression. This effect involves the activation of Hippo pathway kinases, repressing YAP1/TEAD transcriptional activity (Seeneevassen et al, Cancers 2020). We also showed that treatment with Verteporfin, a pharmacological inhibitor of YAP/TAZ interaction with the TEAD transcription factors, efficiently inhibits CSC phenotype and properties as well as tumor growth in xenograft models (Giraud et al, Int J Cancer 2019). Ongoing projects aim to determine whether targeting the Hippo pathway and YAP/TAZ/TEAD by different strategies can reduce the invasive and metastatic properties of gastric CSCs in vivo.