03 October 2018

Salmonella + immunotherapy

Injections of bacteria stop the growth of cancerous tumors

Sergey Kolenov, Hi-tech+

Trying to treat cancer with bacteria seems crazy, but it's an old enough idea. According to scientists, microorganisms are able to spur an immune response that will stop the growth of the tumor. The results of the first experiments confirm this.

About 130 years ago, oncologist William Cowley began injecting patients with inoperable cancers with a mixture of killed bacteria. He believed that it stimulates the immune system to fight the disease. Despite the skepticism of colleagues, the doctor claimed that the treatment worked. However, by the 1960s, the "Cowley toxins" were finally supplanted by chemotherapy and radiation.

However, today researchers are gradually returning to the idea of treating cancer with bacteria – however, already alive. In an experiment conducted four years ago, injections of Clostridium novyi bacteria with the toxin gene removed destroyed or reduced tumors in six out of 16 dogs. Moreover, the technique allowed to reduce the size of the tumor in a 53-year-old patient with leomyosarcoma, reports Science Magazine. The first subject was followed by others.

In total, 23 patients with various types of cancer, from sarcoma to melanoma and breast cancer, received bacterial injections during the experiments.

Each was injected with 10,000 to 3 million Clostridium spores. In 19 subjects, including the first patient, tumor growth stopped. Although the injections were local, in some cases they also affected tumors in other parts of the body. Scientists believe that the introduced spores during germination stimulated the antitumor immune response. This is evidenced by the reaction that developed in 11 patients: fever, as well as pain and swelling at the injection site. Perhaps the bacteria themselves also secreted substances that inhibit the growth of cancer cells.

The strategy was so novel that the researchers weren't sure what role the dosage played. It turned out that too high concentration of bacteria in injections leads to dangerous consequences: three patients who received the maximum doses developed life-threatening sepsis.

Nevertheless, despite the risk, scientists are confident in the prospects of the technique. Although the aim of the study was to test the safety, not the effectiveness, of bacterial injections, the experimental results are encouraging.

Currently, Filip Janku, one of the authors of the paper Intratumoral injection of Clostridium novyi-NT spores induces antitumor responses, published in 2014 in the journal Science Translational Medicine, has launched additional clinical studies. He plans to test the combination of bacterial therapy of C.novyi in combination with pembrolizumab (Keytruda).

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