The Local Microbiota as an Emerging Feature of the Tumor Microenvironment

According to the most recent data, cancer is one of the most impacting diseases worldwide, scoring an impressive 26.3 million cases across 204 territories and accounting for about 10 million deaths. When scientists discovered that humans and bacteria walk on Earth together as what is defined as a holobiont, a meta-organism constituted by the host human organism and the so-called microbiome, a densely populated community mainly composed of bacteria, some hypothesized that these microorganisms could be considered as a component of the tumor microenvironment and in some way participate to tumor progression. Further research led to confirm this hypothesis and finally include the microbiome among the hallmarks of cancer. This thesis work aims at providing an overview over some recent advances in the field of cancer microbiota studies. In particular, the focus is going to be on the local microbiota as a fundamental component of the tumor microenvironment of the most relevant solid tumors. Considering the prolific production on the topic that has been registered in the last few years, three papers have been selected as deemed to be particularly relevant, high-quality examples, describing the characterization of the local microbiota and the mechanistical role it plays in tumor development, from initial growth to metastasis.