The oncogenic roles of bacterial infections in development of cancer

Initiation of cancer is interconnected with different factors like infections. It has been estimated that infections, particularly viruses, participate in about 20% of all cancers. Bacteria as the most common infectious agents are also reported to be emerging players in the establishment of malignant cells. Microbial infections are able to modulate host cell transformation for promoting malignant features through the production of carcinogenic metabolites participating in inflammation responses, disruption of cell metabolism, and integrity and also genomic or epigenetic manipulations. It seems that the best example of the role of bacteria in cancer promotion is Helicobacter pylori infection, which is related to gastric cancer. World Health Organization (WHO) describes bacterium as class I carcinogens. Several bacterial infections have been reported in association with prevalent cancers. In this review, we will summarize the role of known bacterial infections in the initiation of the main common cancers, which show high mortality in the world. Examining the microbiomes in cancer patients is important and necessary to better understand the pathogenesis of this disease and also to plan therapeutic interventions.