Does microbiome shift play a role in carcinogenesis? A systematic review

Recent scientific advances have presented substantial evidence that there is a multifaceted relationship between the microbiome and cancer. Humans are hosts to multifarious microbial communities, and these resident microbes contribute to both health and disease. Circulating toxic metabolites from these resident microbes may contribute to the development and progression of cancer. The aim of this systematic review was to evaluate microbiome and microbial shift contribution to the development and progression of cancer. This systematic review provides an analytical presentation of the evidence linking various parts of the microbiota to cancer. Searches were performed in databases such as PubMed, Google Scholar, Scopus, EBSCO, E-Journals and Science Direct from the time of their establishment until May 2018 with the following search terms: cancer or human microbe or cancer and human microbiome AND shift in microbes in cancer. The merged data were assessed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Cochrane's Risk of Bias Tool was used to assess the bias. Initially, 2,691 articles were identified, out of which 60 full-text articles were screened and re-evaluated. Among them, 14 were excluded based on inclusion/exclusion criteria; eventually, 46 articles were included in the systematic review. The reports of 46 articles revealed that microbial shift involving Candida species, Fusobacterium nucleatum, Porphyromonas gingivalis, Helicobacter pylori and Human papilloma virus (HPV) 16 & 18 were most commonly involved in various human cancers. In particular, organisms, such as Candida albicans, Fusobacterium nucleatum, Porphyromonas gingivalis and HPV-16 were found to be more prevalent in oral cancer. The present systematic review emphasizes that the role and diverse contributions of the microbiome in carcinogenesis will provide opportunities for the development of effective diagnostic and preventive methods.