Methods for the development of tumor-targeting bacteria

Introduction: For at least two centuries, there have been reports that cancer patients infected with various bacteria had what appeared to be spontaneous remission. In the late nineteenth and early twentieth centuries, W.B. Coley, of what is now the Memorial Sloan-Kettering Cancer Center, pioneered bacterial therapy of cancer in the clinic with considerable success. After Coley died in 1936, bacterial therapy of cancer started to go out of favor. In the current twenty-first century, there is great resurgent interest in developing bacterial therapy for treating cancer using either obligate or facultative anaerobic bacteria. There is also controversy about which bacteria are optimum for cancer treatment and whether bacteria should be used as tumor-targeting vectors, immune stimulators, or for direct tumor killing. Areas covered: This review covers various types of bacteria currently used for tumor targeting. It also covers methods used to develop maximal tumor targeting and minimally attenuated bacteria, which grow in viable as well as necrotic areas of tumors and directly kill cancer cells. Expert opinion: The current paradigm of cancer chemotherapy lacks sufficient efficacy, and a new paradigm is needed. Bacterial therapy is a candidate for a 'new' approach to cancer treatment. In the authors' opinion, the current revival of bacterial therapy of cancer is one of the most promising approaches to treatment.