Cancers evade destruction by convincing some immune cells to suppress others, but a surprising interlocutor can persuade the suppressors to defect, and the destroyers to redouble. A review published in Frontiers in Oncology explains how bacteria can rally immune cells to attack tumors, via ancient lines of chemical communication with our immune system. Decoding these molecular signals is key to developing bacteria as a safe, targeted, and effective treatment for cancer.
More than a century ago, surgeon William Coley successfully treated a variety of cancers with injections of heat-killed bacteria. Shocked?--his contemporaries certainly were. Soon, the rise of radiotherapy and stricter drug safety laws confined "Coley's toxins" to the laboratory.
However, scientists continue to test bacteria like salmonella, clostridium and listeria--which replicate inside host cells--on mice bearing tumors from breast, colon, skin, and other cancers. After injection into the blood or tissues, these bacteria preferentially accumulate within tumors, arresting their growth and spread and prolonging survival.
Now, bacterial immunotherapy soon may return to the oncology clinic, says a review of these studies. According to senior author Basel al-Ramadi, professor of immunology at United Arab Emirates University, they show how "bacteria can reprogram the immune response to cancer" via targets in innate immunity. Serviced primarily by "myeloid cells," this is the body's evolutional* ancient first line of defense.
Tumors produce signals that compel myeloid cells to suppress immune attack, help feed the cancer through new blood vessels, and even pave its way to spread around the body, but many bacterial...