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Bacteria in tumours can prevent chemotherapy from working

15 September 2017

Researchers in Israel have discovered a reason why gemcitabine chemotherapy does not work very well for patients with pancreatic cancer.

The research team at the Weizmann Institute of Science found that bacteria inside cancer cells can destroy the drug. They also found that that these bacteria were present in three quarters of biopsies taken from over 100 pancreatic cancer patients.

The team made the discovery while investigating why some healthy cells can be forced to help cancer cells to become resistant to drugs. They saw that a particular group of skin cells prevented gemcitabine from killing neighbouring cancer cells and noticed that the skin cells were infected with bacteria called Mycoplasma.

Further research showed that the bacteria internalised the gemcitabine and degraded it by producing an enzyme called cytidine deaminates, which effectively deactivated the drug.

Analysing 113 pancreatic cancer biopsies, they found that 86 were infected with types of bacteria that could produce this enzyme, including common bacteria such as E. coli and salmonella.

The discovery matches other research which found that bacterial infections can hamper chemotherapy.

The team then conducted tests on mice and were able to show that antibiotics prevented the bacteria from destroying the gemcitabine.

The discovery suggests that using antibiotics alongside cancer drugs is something that warrants further investigation; however, researcher Dr Ravid Straussman warned that this could cause some of the bacteria to develop resistance to antibiotics. 

Instead, he suggests that a better strategy could be to develop drugs to block the specific activity of the enzyme that destroys the gemcitabine.

Gemcitabine is also used to treat colon and bladder cancer, and the same effect may play a role in people with those cancers too, he said.

He also explained that further research may show that the bacteria can deactivate other anti-cancer drugs, and his team is currently investigating this effect in a drug called oxaliplatin.  

The research is published in the journal Science.

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