Brain tumors are frequently diagnosed diseases in which etiology and progression largely
depend on mutations and genetic factors. Additionally, recent reports document that
the microbiome may influence tumor growth, tumor microenvironment, and response to
therapy. Our goal was to examine the extent to which the bacterial composition—microbiota—and
fungal composition—mycobiota—characteristic of the tumor and its microenvironment
correlate with the composition of the gut and blood microbiota and mycobiota in five
randomly selected brain tumor patients. The bacterial composition of the tumor, tumor-adjacent
tissue (TAT), blood, and gut samples of the five patients were analyzed by 16S rRNA
and ITS-based sequencing in order to determine the bacterial and fungal composition.
The gut microbiome and mycobiome composition showed individual and tissue-specific
signatures in each patient. The microbiome composition of the blood, TAT, and tumor
tissue was very similar in each patient, dominated by Klebsiella, Enterococcus, Blautia,
and Lactobacillus spp. In contrast, the mycobiome composition of the blood, TAT, and
tumor showed a diverse, individual picture. The most common fungal species in the
blood and TAT were Tomentella, Didymosphaeria, Alternaria, Penicillium, Mycosphaerella,
and Discosia. The blood and TAT mycobiome were similar to each other but unique and
characteristic of the patients. In contrast, in the tumor tissues, Alternaria, Malassezia,
Schizophyllum, and Tomentella genus were the most common fungi genus. Our results
showed that the presence of fungi in tumors shows a unique pattern that is independent
of the pattern observed in the gut, blood, and tumor environment and that the effects
of the mycobiome are distinct and cannot be associated with those of the microbiome.
Elucidating the role of fungi in tumors and exploring the relationship between fungi
and brain tumor types may open up further therapeutic options.
