Many great scientific discoveries have arisen out of laboratory accidents, from the mistake that led to penicillin, to revelations of LSD's psychedelic properties after Albert Hoffman unexpectedly absorbed a dose through his fingertips in 1943. The latest serendipitous discovery comes from a cross-contamination accident that has revealed how a certain bacteria can stifle the efficacy of cancer drugs.

A team at the Weizmann Institute of Science was initially investigating how normal human skin cells could affect a cancer cell's resistance to chemotherapy. A specific sample of skin cells was observed to generate a strange resistance in pancreatic cancer cells to a commonly used chemotherapy drug called gemcitabine. The researchers subsequently discovered that a bacteria had contaminated the skin cells and, just before throwing it all in the bin, they decided to take closer look.

"We nearly threw it away," says head of the Weizmann research lab, Dr Ravid Straussman, "but then we decided to follow it up, instead."

The team discovered that a class of bacteria called Gammaproteobacteria could metabolize the chemotherapy drug, rendering it ineffective. More research revealed that a only very specific form of the bacteria, one holding a long isoform of a certain gene called CDD, could inactivate the cancer drug.

The researchers subsequently wondered, if that particular bacteria was present inside human pancreatic tumors, could it significantly hinder the efficacy of the chemotherapy treatment? The answer to both questions was a resounding yes.

Testing 113 pancreatic tumor samples the team found 76 percent of the samples contained bacteria, primarily Gammaproteobacteria. Further mouse studies showed that bacteria harboring the particular variant of the CDD gene did inhibit the efficacy of gemcitabine in attacking pancreatic tumors. Most excitingly, when the bacteria was killed off with a course of antibiotics, the mice responded to the chemotherapy drug.

"These correlative results raise the tantalizing possibility that the efficacy of an existing therapy for this lethal cancer might be improved by cotreatment with antibiotics," write the researchers in the recently published study.

This accidental discovery could yield a whole new wave of improvements to existing cancer treatments. The researchers are now examining whether this bacteria, or others with similar behavior, are present in more cancer types and what effects they could be having on the efficacy of other cancer drugs.

The research was published in the journal Science.

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