Antioxidant oils and Salmonella enterica Typhimurium reduce tumor in an experimental model of hepatic metastasis

Diet, Microbes, and Cancer Across the Tree of Life: a Systematic Review

PURPOSE OF REVIEW

Cancers are a leading cause of death in humans and for many other species. Diet has often been associated with cancers, and the microbiome is an essential mediator between diet and cancers. Here, we review the work on cancer and the microbiome across species to search for broad patterns of susceptibility associated with different microbial species.

RECENT FINDINGS

Some microbes, such as Helicobacter bacteria, papillomaviruses, and the carnivore-associated Fusobacteria, consistently induce tumorigenesis in humans and other species. Other microbes, such as the milk-associated Lactobacillus, consistently inhibit tumorigenesis in humans and other species. We systematically reviewed over a thousand published articles and identified links between diet, microbes, and cancers in several species of mammals, birds, and flies. Future work should examine a larger variety of host species to discover new model organisms for human preclinical trials, to better understand the observed variance in cancer prevalence across species, and to discover which microbes and diets are associated with cancers across species. Ultimately, this could help identify microbial and dietary interventions to diagnose, prevent, and treat cancers in humans as well as other animals.

Salmonella enterica Typhimurium engineered for nontoxic systemic colonization of autochthonous tumors

Much of the bacterial anticancer therapy being developed relies on the ability of bacteria to specifically colonise tumours. Initial attempts to translate promising Salmonella enterica Typhimurium (S. Typhimurium) preclinical results to the clinical setting failed, primarily due to lack of tumour colonisation and the significant toxicities from systemically administered Gram-negative bacteria. To address the difference in results between preclinical experiments performed in mice with transplant tumours and clinical trials in human volunteers with autochthonous tumours, a genetically engineered mouse model of breast cancer (BALB-neuT) was utilised to develop a strain of virulence-attenuated S. Typhimurium capable of robust colonisation of autochthonous tumours. Several genes that code for bacterial surface molecules, responsible for signalling a toxic immune response against the bacteria, were mutated. The resulting S. Typhimurium strain, BCT2, allowed non-toxic intravenous administration of 3 × 10⁶ colony forming units of bacteria in tumour-burdened mice when combined with a vascular disruption agent to induce intratumoral necrotic space and facilitate bacterial colonisation.

Salmonella as a vaccine delivery vehicle

Attenuated Salmonella vaccines can be administered orally to deliver recombinant antigens to mucosal surfaces inducing a protective immune response against a variety of targeted pathogens. A number of exciting new approaches and technologies for attenuated Salmonella vaccines have been developed recently. However, a disconnect remains between results obtained with mice in preclinical studies and results obtained in human clinical trials. This is due to an incomplete understanding of Salmonella Typhi interactions with human hosts and inadequate animal models available for study. In this review, the authors describe recent progress in identifying important differences underlying S. Typhi-host interactions, the development of novel approaches to vaccine design and six recent clinical trials evaluating Salmonella-vectored vaccines.