Could the screening of fungi present in the human body be part of the future markers used in the diagnosis or prognosis of cancers? This new field of research is arousing the enthusiasm of microbiologists, who have coined the term “mycobiota” to designate all of the fungal communities colonizing the various ecosystems of the human body. After the revolution in the bacterial microbiota of recent years, very recent work on the role of fungi in cancerous tumors has attracted the attention of researchers.
They discovered that these microorganisms could reprogram the first lines of defense against cancer. The intratumoral mycobiota would force the immune system to tolerate the presence of the tumor instead of fighting it, allowing it to continue its progression.
On September 29, 2022, two independent teams, American and Israeli, reported, in the same issue of the journal Cell, the presence of fungi in a large number of tumor types. According to these researchers, these fungal communities are associated with the development of a wide variety of cancers. There would therefore be a link between fungi and tumorigenesis.
“These two studies are extremely important in that they attest to the presence of fungi in all major types of cancer, even if the fungal load is low”, says Françoise Botterel, president of the French Society of Medical Mycology. “From a methodological point of view, there is really nothing to sayadds the professor of parasitology and mycology, at the Henri-Mondor hospital (Créteil). These teams used an impressive number of techniques: genomic sequencing, transcriptomics to detect yeast messenger RNA, immunohistochemistry to visualize fungi using antibodies, quantitative fungal PCR to assess fungal load. The tumor tissue samples came from no less than four cohorts of cancer patients. »
Modulate host immunity
The American team observed one fungal cell, on average, for every 10,000 human tumor cells, fungal DNA being moreover found in tumor tissue in a much lower quantity than that of bacterial DNA. Indeed, intestinal bacteria (such as Bacteroides fragilis, Escherichia coli, Fusobacterium nucleatum) are implicated in the development of colorectal cancer. Similarly, it is known that one of the main risk factors for stomach cancer is chronic infection with the bacteria Helicobacter pylori. These bacteria have in common the ability to modulate the host’s immunity and cause chronic inflammation, thus contributing to the cancerous process.
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