Bacteria and Cancer

Microbial infections are the major contributor of almost 20–30% of cancer cases, and dysbiosis of the gut microbiota is progressively considered a hallmark of cancer. According to the WHO, a number of bacterial infections are linked with common malignancies, and a variety of bacteria are classified as class I carcinogens. Despite the lack of clarity in the mechanisms involved in bacterial carcinogenesis, chronic inflammation and the creation of carcinogenic compounds have been identified as key pathways that develop association between cancer and bacteria. Surprisingly, microbes are capable of eradicating tumor cells. Even though chemotherapy, surgery, radiation, and immunotherapy are effective treatments against cancer, these treatments also have drawbacks such as toxicity and tumor resistance. This chapter focuses on the dual nature of bacteria as cancer progressor as well as cancer suppressor. The chapter highlights the role of bacteria in cancer development specifically colorectal, gastric, lung, gall bladder, and breast cancers with reference to association of bacteria with various types of cancers along with oncogenic molecular pathways together with bacterial therapeutics to improve outcomes and minimize adverse effects. Promising both on their own and in combination with chemotherapy, bacteria can elicit anticancer responses and act as carriers of medicines or genes. This chapter also highlights clinical studies involving bacteria-based cancer treatments and tumor regression induced by bacteria.