Colorectal cancer screening could, in the future, do without stool testing. According to a study published in Nature Communicationa common and harmless bacterium capable of nesting in tumors that may be present can be modified in the laboratory to release a measurable marker in the urine and blood.

Looking for new tests

Colorectal cancer is the second leading cause of cancer death, with a worrying increase in the number of cases in young adults, a fact which in itself makes early diagnosis even more important. The most specific, sensitive and effective test for the prevention and early diagnosis of colorectal cancer is the search for occult blood, a laboratory test that allows you to identify even minimal traces of blood in the feces, even those not visible to the eye. naked. However, work has been on an alternative for some time, and researchers from the South Australian Health and Medical Research Institute (Sahmri) at the University of Adelaide and Columbia University in New York are developing a test that does not require stool collection. , but the ingestion of a “good” bacterium. Their test, which is in an early stage of development, is in fact based onEscherichia coli Nissle 1917 (EcN), already used as a probiotic supplement against intestinal disorders.

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What does he do E. coli Nissle

Escherichia coli Nissle 1917 is called this because it was isolated for the first time during the Great War by the German doctor Alfred Nissle from the intestine of a soldier who did not fall ill with dysentery, while all the others did: in the trenches of the First World War, in fact, the dysentery was rampant. Many years after its isolation, this microorganism has been shown to counteract the excessive growth of “bad” intestinal bacteria and is therefore used as a probiotic.

Bacteria capable of detecting the DNA of tumor cells have been designed

An “attraction” to cancer

But this good bacterium also does something else: EcN tends to be attracted to tumor formations in the intestine – if present – both malignant and benign. And there he nestles. In short, Escherichia coli Nissle it is a “carcinophilic” bacterium and this is the characteristic that researchers want to exploit. They first demonstrated that EcN administered orally to both laboratory mice and human patients with colorectal cancer reaches the intestine and selectively and consistently colonizes intestinal polyps, when present. “Our study – he said Georgette Radford from the University of Adelaide, among the authors of the research – indicates that after an oral dose, these bacteria live selectively in the benign precursor lesions of intestinal cancer, i.e. in polyps, and in intestinal tumors”.

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The test with the modified bacterium

The next step was to engineer the bacterium: the researchers, by intervening on its DNA, made the microorganism capable of producing salicylate once it came into contact with intestinal tumor tissue, even when the lesion was in its initial stages. Salicylate is a safe and easily recoverable molecule in urine, feces and body fluids. They then administered an oral dose of the engineered bacterium to experimental mice and after 48 hours they saw that salicylate was present in the urine of the animals with tumors in an amount 5 times higher than that measured in healthy control mice. “We exploited the natural attraction of this bacterium for tumors – Radford specified – and we modified it to release molecules that highlight tumors already at an early stage”.

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The next steps

“In the future – he added Susan Woodsalso from the University of Adelaide and co-author of the study – we aim to be able to detect this marker with a blood test”. But not only that: the research group believes that this attraction of EcN for tumors could be exploited also for treatment. In fact, the bacterium could be manipulated to deliver a targeted therapy.

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