Scientists have found that some cancer-killing viruses (which Yu-Jin mentioned a few posts below) are even more effective at fighting cancer when paired with a bacterial enzyme. The enzyme of interest is called chondroitinase, and it comes from the Proteus vulgaris intestinal bacteria. This enzyme facilitates virus movement inside the tumor by clearing out the sugar chains of proteoglycans that normally create a barrier between cells.
The article noted two experiments in which this effect was observed. In the first, researchers injected glioblastoma cells under the skin of laboratory animals to cause tumor growth. The experimental group of animals (which received a virus-enzyme combination as treatment) lived an average of 28 days, while the control group (which received only oncolytic virus as treatment) only lived 16 days. Another experiment examined mice that had human glioblastomas transplanted into their brains. The results showed that virus-enzyme combination treatment increased survival by 52% when compared to virus-only treatment. In both of these experiments, some of the mice that received virus-enzyme treatment became tumor-free and lived for more than 80 days.
This is an interesting way in which viruses and bacteria, which we often think of as harmful to humans, may be useful in actually combating human disease.