In a feat of microbial judo, researchers from Johns Hopkins have turned a flesh-eating bacteria into a highly-effective anti-cancer agent.
Clostridium novyi is a common bacteria, found most frequently in soil and feces. The wild type consumes living cells and produces a protein known as an alpha-toxin, which disrupts the molecules that make up a cells skeleton. Without that skeleton, cells essentially fall apart, leaking their liquids into the surrounding tissue and dying. If untreated, a C. novyi infection can lead to death.
But the Johns Hopkins team realized that C. novyi’s unique traits could be exploited. In addition to causing tissue death, it thrives in low-oxygen environments like tumors, which grow so quickly that they lack adequate blood supply. So the researchers removed the deadly alpha-toxin producing gene and tested the attenuated strain on tumors in various organisms ranging from rats to dogs and humans by injecting spores directly into the tumor sites.
In each case, the modified bacteria fervently consumed tumor cells while leaving the surrounding healthy tissue in tact. C. novyi thrived in the hypoxic conditions inside the tumors but, when it strayed from the cancer site into healthy regions, it met stiff resistance from the body’s immune system. Rats with cancer that were treated with C. novyi injections lived more than twice as long, and tumors shrunk in six of the 16 dogs in the test and were eliminated in three more.
The first human patient treated with C. novyi had metastasized abdominal cancer, and researchers focused on a tumor in her shoulder, injecting spores directly into the site.
Carl Engelking, writing for Discover Magazine:
The treatment wasn’t a walk in the park: the patient experienced severe pain in the shoulder, plus a fever as her body battled the bacteria. Eventually, her tumor formed an abscess that needed to be drained of fluid and debris. Two months after treatment her tumor showed all the signs of defeat, without evidence of a persistent infection.
The patient’s other tumors, which weren’t treated with C. novyi, continued to grow, meaning the treatment was confined to the injection site. That’s both good news and bad—it means C. novyi isn’t straying beyond the tumor site and causing other problems, but it also means each individual tumor would need to be targeted.
Human trials of C. novyi are still ongoing, so scientists are holding their breath to see if it’s successful in other cases. But they’re hopeful that this surprising microbial helper could pair with existing treatments to form a combination that’s both more deadly and more targeted, potentially adding years to patients’ lives.