Abstract
OBJECTIVE: This study aimed to explore the characteristics intratumoral microbiome in oral squamous cell carcinoma, and elucidate the interplay between intratumoral microbial profiles (relative abundance/absolute load) and tumor-infiltrating lymphocytes markers (CD4(+)/CD8(+)/FOXP3) and PD-L1 in oral squamous cell carcinoma. METHODS: We analyzed 45 OSCC tissue samples alongside paired paracancerous (n=10) and normal oral microbiota controls (n=8). Microbial composition was characterized by 16S rRNA sequencing (V3-V4 regions), with bacterial load quantified via qPCR targeting the V4-1 region. Tumor-infiltrating lymphocytes markers were assessed by immunohistochemistry. RESULTS: Spirochaetota was concentrated in the CD4(+) as well as CD8(+) low infiltration groups, Proteobacteria in the CD8(+) high infiltration group and Actinobacteriota in the FOXP3 low infiltration group. Tumor microbial load was negatively correlated with CD4(+), CD8(+), and FOXP3, but of these, only the correlation coefficient of -0.309 for CD4(+) was statistically significant. However, no significant correlation was observed in the analysis of PD-L1 expression with the relative abundance of intratumoral microbiome, α-diversity, and intratumoral microbial load values. CONCLUSION: Changes in the abundance of specific intratumoral microbiome affect the infiltration of TILs markers, and there is a negative relationship between intratumoral microbial load and T-cell infiltration, suggesting that intratumoral microbiome contribute to the processes of the tumor immunosuppressive microenvironment.