Bacteria May Play a Role in Chemotherapy Resistance

In a study published Septemebr 2017 in Science, an international team of researchers funded in part by NCI found that several species of bacteria can break down the chemotherapy drug genncitabine (Gemzar), rendering it useless. In a mouse model where such bacteria had colonized colon cancer xenografts, the antibiotic ciprofloxacin restored tumors’ sensitivity to gemcitabine.

Because gemcitabine is commonly used in the treatment of pancreatic cancer, the researchers looked at the prevalence of bacteria in pancreatic tumor samples from patients. They found that, out of 113 samples tested, 76% tested positive for any type of bacteria. And out of a set 15 bacteria-positive samples that underwent further analysis, 93% contained bacteria that, in laboratory experiments, were found to confer complete resistance to gemcitabine.

"The presence of bacteria in human tumors may paradoxically result in drug concentrations that are lower in the tumor than in other organs," wrote the authors. Because chemotherapy sensitivity could be restored with antibiotic treatment in their experiments, they concluded that such combination therapy is worth exploring in further research.

https://www.cancer.gov/news-events/cancer-currents-blog/2017/bacteria-colorectal-cancer