The microbiome and risk of cancer in the stomach
Infection of H. pylori might be a necessary cause for stomach cancer. However, only a minority of all infected develops stomach cancer. We hypothesize that H. pylori genotypic variation can predict carcinogenicity.
We plan to perform a case-control study nested within a cohort of patients with gastric biopsies. For stomach cancer cases and their matched controls, the paraffin-embedded blocks from the baseline biopsies will be retrieved for metagenomic analysis of H. pylori, using our newly developed method. Based on the newly found biomarkers, a multiplex H. pylori antibody assay will be developed.
Gastric carcinogenesis is accompanied by the development of mucosal atrophy, which facilitates colonization of other microorganisms. Alternatively, we hypothesize that the degree of nitrosamine forming ability in the new microorganisms is linked to stomach cancer risk. In an endoscopy study we will collect brushing samples from a representative Swedish population, to characterize normal stomach microfloras, as well as those from subjects with a spectrum of gastric lesions. In the above-mentioned nested case-control study, stomach microbiota will also be compared between cases and controls.
Our research will help identify true carcinogenic H. pylori strains or non-H. pylori bacterial species, which in turn will help identify a subpopulation at extremely increased risk of stomach cancer. This will facilitate a cost-effective and safe primary prevention for this dreaded malignancy.