Injecting a Type of Bacteria Destroys Tumors in Animals and Humans: Study

Study finds modified form of bacteria injected in to rats, dog and even humans can destroy and inhibit growth of tumors.

Clostridium novyi or C.novyi is a micro-organism that lives in oxygen deprived conditions in soil and causes serious infections in cattle and humans. Experts at the Johns Hopkins Kimmel Cancer Center found the bacterium can be used in treating cancer as it helps target tumor cells without oxygen that are difficult to get rid of by conventional methods like chemotherapy and radiation. For the trial, researchers suppressed a specific gene that releases toxins and injected C.novyi NT spores to 16 pet dogs with tumors. 

It was observed that six dogs experienced positive responses within 21 days after receiving injections and half of these dogs had complete shrinkage of tumors. The overall reduction of tumor size and diameter was 30 percent more than that of other three dogs who were also treated with C. novyi NT injections. However, a majority of the dogs suffered negative-side reactions like bacterial infection, formation of abscess, tumor inflammation and fever.

"One advantage of using bacteria to treat cancer is that you can modify these bacteria relatively easily, to equip them with other therapeutic agents, or make them less toxic as we have done here," said Shibin Zhou,study author and associate professor of oncology at the Cancer Center in a news release.

The next stage of the experiment, scientists tested the bacterium on human subject with tumor growth in abdomen. The C.novyi was delivered directly through metastatic tumor in her arm that drastically reduced. The patients also underwent similar side-effects and symptoms of bacterial infection. But the authors are not certain if these reactions would normally occur to everyone treated with C.novyi NT spores. Their past clinical study conducted a decade ago also noted many patients contracted infections and the cancer tumor reappeared.

In addition, the research team also assessed the safety and efficacy of this method on rats that were implanted with gliomas or brain tumors. The C.novyi NT attacked only tumor infested region and did not harm healthy tissue cells. Rats that were injected with bacteria had increased survival rate.

The authors hope their new method combined with existing cancer treatment techniques helps eradicate tumors and builds resistance against new tumor formation.

"We expect that some patients will have a stronger response than others, but that's true of other therapies as well. Now, we want to know how well the patients can tolerate this kind of therapy.Another good thing about using bacteria as a therapeutic agent is that once they're infecting the tumor, they can induce a strong immune response against tumor cells themselves," added Zhou. 

More information is available online in the journal Science Translation Medicine.