Researchers at Columbia University have engineered bacteria to dive into tumors and explode, releasing a tiny antibody. The study, published in Nature Medicine, is part of a larger trend in synthetic biology, a field of research that aims to genetically modify living organisms for human benefit.

In the study, E. coli, a microbe that normally resides in the human gut, was engineered to create and release the therapeutic nanobody inside of tumors. The team tested their “cancer-killing” microbe in mice with B-cell lymphoma and observed that tumors injected with the engineered microbes rapidly shrank.

But this isn't the coolest part of the study.

The mice had tumors in both of their legs, but when just one of their legs was injected with the programmed bacteria, both tumors began to shrink. This observation supports an old idea in cancer biology called the abscopal effect. The hypothesis underlying this effect posits that that untreated tumors will shrink when a different tumor is treated due to peripheral actions by the immune system.

While these engineered microbes will not be used in hospitals any time soon, this study offers an intriguing glimpse into the amazing, ongoing interactions between the immune system, bacteria, and metastatic cancer.