Ye et al. performed five region-based amplification and bacterial 16 S rRNA sequencing to identify the microbiome of pituitary neuroendocrine tumor (PitNET) tissues across four clinical phenotypes. Multiple filter procedures were performed to inhibit the risk of contamination with bacteria and bacterial DNA. Histological analysis was also conducted to validate the localization of bacteria in the intra-tumoral region.

They identified common and diverse bacterial types across the four clinical phenotypes of PitNET. They also predicted the potential functions of these bacteria in tumor phenotypes and found that these functions were reported in certain previous mechanistic studies. The data indicate that the pituitary neuroendocrine tumor pathogenesis and development of tumors may correlate with the behavior of intra-tumoral bacteria. Histological results, including lipopolysaccharide (LPS) staining and fluorescence in situ hybridization (FISH) for bacterial 16 S rRNA clearly demonstrated the localization of bacteria in the intra-tumoral region. Staining for Iba-1 suggested that the proportion of microglia was more abundant in FISH-positive regions than in FISH-negative regions. Furthermore, in FISH-positive regions, the microglia exhibited a longitudinally branched morphology that was different from the compact morphology observed in FISH-negative regions.

They provide evidence for the existence of intra-tumoral bacteria in PitNET ¹⁾