The multi-institutional study investigates the presence and biological significance of microbial elements within primary and metastatic brain tumors (gliomas and brain metastases). Researchers utilized rigorous, orthogonal methods, including fluorescence in situ hybridization (FISH), immunohistochemistry, and spatial molecular imaging (SMI), on 243 tissue samples to validate the presence of intracellular bacterial 16S rRNA and lipopolysaccharides localized to tumor, immune, and stromal cells. Although standard culture methods failed to grow cultivable bacteria, sequencing workflows identified distinct bacterial taxa, some of which showed sequence overlap with oral and gut microbiota, suggesting a distant source. Furthermore, spatial analysis demonstrated that tumor regions with high bacterial signals were enriched for antimicrobial and immunometabolic signatures, suggesting a complex host-response interaction within the tumor microenvironment.

References:

• Morad G, Damania A V, Melendez B, et al. Microbial signals in primary and metastatic brain tumors[J]. Nature Medicine, 2025, 31(11): 3675-3688.