Intratumoral microbiota composition regulates tumor progression in clear cell renal cell carcinoma

Introduction & Objectives

As an emerging area of research, intratumoral microbiota has recently been shown to be closely associated with the progression of solid tumors. However, the relevance of intratumoral microbiota in renal tumors remains unexplored. This study aims to confirm the presence of intratumoral microbiota in renal tumors and to elucidate the compositional characteristics and distributional differences of tumor microbiota in benign renal tumors (angiomyolipoma, AML) versus malignant tumors (clear cell renal cell carcinoma, ccRCC). Additionally, we seek to explore the potential relationship between intratumoral microbiota and ccRCC progression and to reveal the specific mechanisms underlying microbiota-tumor interactions.

Materials & Methods

1. Through 16S rRNA fluorescence in situ hybridization (FISH), immunohistochemical(IHC) staining , transmission electron microscopy, and tissue culture, we identified viable bacteria within tumor tissues, with most bacteria located inside tumor cells.
2. To clarify the correlation between intratumoral microbiota and tumor progression, we utilized a patient-derived xenograft (PDX) model that retains the microbiota composition of tumor tissues, along with the antibiotic doxycycline, which can specifically eliminate the intratumoral microbiota.
3. Using the novel 2b Restriction site-Associated DNA sequencing for Microbiome (2bRAD-M sequencing) and metagenomic sequencing data, we defined the proportion and distributional characteristics of microbiota within ccRCC and AML tumor tissues.
4. Through phenotypic assays and in vivo experiments in mice, we confirmed that Burkholderia vietnamiensis (B. vietnamiensis), present at high relative abundance in high-grade malignant tumors, promotes tumor progression.
5. Using transcriptome sequencing, metabolomic sequencing, single cell sequencing and related molecular assays, we explored the specific mechanisms of interaction between B. vietnamiensis and tumor cells.

Results

1. We confirmed the presence of culturable viable bacteria within renal tumor tissues. Electron microscopy revealed that most bacteria are located inside tumor cells.
2. The results of the PDX models indicated a correlation between the intratumoral microbiota and its progression.
3. The results of high-throughput sequencing revealed the composition and distribution characteristics of the microbiota within renal tumors and identified a high abundance of B. vietnamiensis in high-grade malignant tumor tissues of ccRCC.
4. B. vietnamiensis can activate the “MAPK signaling pathway” within tumor cells to promote tumor progression. Additionally, B. vietnamiensis can enhance “tryptophan metabolism” within tumor cells, which may further facilitate tumor immune escape.

Conclusions

Viable bacteria are present in renal tumor tissue cells, and the existence of intratumoral microbiota is associated with tumor progression.