Quirks & Quarks

Chemotherapy eating bacteria defend cancer

Bacteria living inside cancer tumours can actually eat chemotherapy drugs
Pancreatic cancer cells with bacteria (in fluorescent green) within them. (Leore Geller)

The discovery
Researchers have found that bacteria live inside cancerous tumours they've studied, and these bacteria can suck in and neutralize a common chemotherapy drug, effectively defending the cancer against our medications. In follow up lab experiments, they found that if they eliminated the bacteria with antibiotics, the cancer was once again vulnerable to the chemotherapy drug. The work was done by a team led by Dr. Ravid Straussman, a Senior Scientist in the Department of Molecular Cell Biology at the Weitzmann Institute of Science in Rehovot, Isreal.

We can find bacteria both inside the cancer cells themselves, as well as between cancer cells, and even in some other cell types inside the tumour.This whole thing is new for us... Finding bacteria living inside pancreatic cancers was very novel to us.We didn't expect it at all.- Dr. Ravid Straussman

Why this matters
One of the important reasons cancer treatments can fail is that cancers can develop reisistance to chemotherapy drugs - the drugs lose efficacy and can ultimately stop working. Researchers have traditionally thought the reason for this was the cancer mutating and evolving new ways to fight off the drug. This discovery suggests that bacteria could be playing an important role in resistance, which might lead to new ways to defeat that resistance, and successfully treat cancers. 

Even though we did trace these bacteria inside the tumours, and even though these bacteria can degrade gemcitabine [the chemotherapy drug], we still didn't really prove how important are these bacteria in conferring resistance in patients.- Dr. Ravid Straussman

What they still don't know
Because this discovery is so new, there's a lot more to learn. They don't know ultimately how many kinds of cancers or individual tumours may harbour bacteria, though early results suggest it may be common. The researchers found bacterial resistance to one commonly used chemotherapy drug, and have some data on a second, but they don't know how many other drugs bacteria may be able to neutralize. They also don't know how important this is as a resistance mechanism in humans with cancer - there are likely other factors. Finally, this is all lab research, so it will take time and thorough clinical trials to determine if, and then how, we may be able to attack defensive bacteria to make chemotherapy more effective.