We have known for some time that the bacteria found in our intestines and in other areas of our bodies (so-called microbiome) can, in certain cases, play a role in the onset or development of several forms of cancer, as well as in the effectiveness of cancer treatments (either slowing tumors down or healing them). However, a study just published in the journal Nature has gone one step further: the genetic material “lost” in the blood by these bacteria – suggest researchers from the University of California San Diego in La Jolla – could become an important tool in the future for the early detection of cancer. “Until now the complex interplay human cancer cells may have with the bacteria, viruses and other microbes that live in and on our bodies has not been widely studied”, said Rob Knight, head of the Center for Microbiome Innovation at the University of California, “In fact, the number of microbial genes (i.e. the total genetic code of microbiome, editor’s note) in our bodies vastly outnumbers the number of human genes, so it shouldn’t be surprising that they give us important clues to our health”.
The researchers from California examined a large quantity of data contained in the Cancer Genome Atlas, a vast archive of the US National Cancer Institute, and they discovered that in 17,000 samples (tumor samples, samples of tissue adjacent to tumors and blood) taken from 10,481 patients with 33 different types of cancer, distinct microbial “signatures” emerged. To be precise, 7.2% of the genetic material analyzed was not human, but belonged to a bacterial or viral species, or to archaea (forms of archeabacteria).
Several of these patterns were expected, such as the association between the human papillomavirus virus (HPV) and cervical cancer (the role played by HPV in the occurrence of endometrial cancer has been widely studied and demonstrated). The association between several types of bacteria and gastrointestinal cancers, which the researchers were already aware of, also emerged in the survey conducted by Professor Knight’s team. However, the team also identified previously unknown microbiome signatures: for example, the connection between Faecalibacterium and certain types of colon cancer.
At this point the researchers went even further, and used artificial intelligence systems to try and understand if it was possible to detect cancer in 100 patients (with different forms of cancer at varying stages) using only the microbial DNA found in their blood. And the first results seemed encouraging. In particular, by analyzing plasma samples taken from 59 people with prostate cancer, 25 with lung cancer and 16 with melanoma, and comparing them with the plasma of healthy volunteers, the Californian bioengineers were able to identify various types of cancer with up to 86% accuracy. New studies will be necessary, of course, but according to the researchers, in the future these types of tests may be able to help to accurately detect the presence of several forms of cancer in the early stages (earlier than current diagnostic systems) and to follow their development. “This new understanding of the way microbial populations shift with cancer could open a completely new therapeutic avenue,” said Sandrine Miller-Montgomery, co-author of the research published in Nature, “We now know the microbes are there, but what are they doing? And could we manipulate or mimic these microbes to treat cancer?”.
