The bacterium used is a non-pathogenic strain of Escherichia coli
(called Nissle 1917 or under the trade name ‘Mutaflor’
), and one that is commonly found in the liver. Through genetic manipulation, researchers successfully re-engineered this bacterium so that it produced a luminescent signal. The signal can be picked up from a urine sample.
The re-engineering of the bacterium involved transplanting a gene called lacZ. This gene cleaves lactose into glucose and galactose. If, instead, luciferin is linked to galactose, this creates a luminescent protein (and characteristic 'glow') of the sort produced by fireflies.
The premise is that where tumors are present, the body’s immune system is weak. If there are sufficient nutrients, then bacteria can grow in higher numbers than would be expected in a healthy adult. By creating bacteria that produce a light signal, researchers can measure the population density — as expressed in luminescent units — and use this information to predict if a tumor has formed.
Studies have successfully been tried
out in mice. In the longer term researchers want to trial out the system in people (although whether the effects on rodents will be replicated remains to be seen.) The way they are proposing to do this is to administer the bacteria orally and the most effective way, they propose, is to add the bacteria to yogurt. This means that the yoghurt function as it does as a live culture, when it contains probiotic organisms.
The research is important because certain cancers, such as cancer of the pancreas or the colon, cause severe damage to the liver through metastasis. The earlier that these cancers are detected then the greater the chance there is of the cancer being treated through surgery.
The research was a joint project between MIT and the University of California at San Diego (UCSD). The findings have been reported
to Science Transitional Medicine
, in a paper headed “Programmable probiotics for detection of cancer in urine.”