Bacterial Involvement in Progression and Metastasis of Adenocarcinoma of the Stomach

Abstract

Gastric cancer metastasis is a process in which the tumor microenvironment may carry significant influence. Helicobacter pylori (H. pylori) infection is well-established as a contributor to gastric carcinoma. However, the role that these bacteria and others may play in gastric carcinoma metastasis is a current focus of study. A review of the literature was conducted to elucidate the process by which gastric adenocarcinoma metastasizes, including its ability to utilize both the lymphatic system and the venous system to disseminate. Studies that investigate the tumor microenvironment at both the primary and secondary sites were assessed in detail. H. pylori and Mycoplasma hyorhinis (M. hyorhinis) were found to be important drivers of the pathogenesis of gastric adenocarcinoma by modifying various steps in cell metastasis, including epithelial-mesenchymal transition, cell migration, and cell invasion. H. pylori is also a known driver of MALT lymphoma, which is often reversible simply with the eradication of infection. M. hyorhinis has been implicated in gastric neoplasia via β-catenin stabilization and subsequent activation of the WNT-signaling pathway, promoting gastric cancer cell motility and inciting cancer progression. Fusobacterium nucleatum (F. nucleatum) and its association with worse prognosis in diffuse-type gastric adenocarcinoma are also reviewed. Recognition of the roles that bacteria play within the metastatic cascade is vital in gastrointestinal adenocarcinoma treatment and potential reoccurrence. Further investigation is needed to establish potential treatment for metastatic gastric carcinoma by targeting the tumor microenvironment.

Keywords: bacterial infection; carcinogenesis; epithelial–mesenchymal transition; gastric cancer; gastric neoplasia; gastrointestinal neoplasm; infectious disease; malignancy; metastasis.

Figure 1

The most common metastasis sites for gastric cancer include the liver, mesentery/omentum, spleen, and bone. Figure created using biorender.com.

Figure 2

Gastric adenocarcinoma begins as superficial gastritis and can progress into atrophic gastritis, metaplasia, dysplasia, and gastric adenocarcinoma, followed by metastatic disease as the feared outcome. Superficial gastritis due to H. pylori is more likely to lead to intestinal type gastric adenocarcinoma.