The role of bacteria in the treatment of cancer: A comprehensive review

Cancer is an important public health issue worldwide and is the main cause of death in the developed countries and the second cause of death in the developing countries. There are several treatments for cancer such as photodynamic therapy, surgery, chemotherapy, hormonal therapy, radiotherapy and immunotherapy. Current cancer treatments have various side effects, including the gradual resistance of cancer cells to treatment. The era of targeted cancer therapy has brought about new clinical approaches such as antibodies, small molecules, antiangiogenics, and antivirals. Yet even these strategies remain limited in their ability to accumulate in tumors and tumor penetration, which are the main obstacles in the treatment of cancer. Historic efforts to harness living organisms to fight cancer have recently been revived in the field of synthetic biology. Certain circulating bacteria can intrinsically home in on tumors, and can be engineered to controllably induce local cytotoxicity while remaining unobtrusive to the host system. Due to the ineffectiveness of conventional treatments such as chemotherapy and radiation therapy in advanced tumor stages, resistance to treatment and non-specificity of these treatments, with the advancement of studies in this field, it is hoped that bacterial therapy will add a new dimension to cancer treatment.