The intratumor microbiome is associated with microsatellite instability.

Area of Science:

• Oncology
• Microbiology
• Genomics

Background:

• Intratumoral microbes may influence cancer development and progression.
• Microsatellite instability (MSI) is linked to increased tumor immunity and mutational burden.

Purpose of the Study:

• To investigate the associations between intratumoral microbes, MSI status, patient survival, and tumor molecular characteristics.
• To explore the role of microbial communities within tumors across various cancer types.

Main Methods:

• Whole transcriptome and whole genome sequencing were used to analyze microbial abundance.
• Associations between microbial genera, MSI, survival, and tumor molecular features were examined in colorectal cancer (CRC), stomach adenocarcinoma, and endometrial carcinoma patients.

Main Results:

• In CRC patients, genera Dialister and Casatella showed strong associations with MSI and improved overall survival.
• Multiple intratumoral microbes correlated with immune gene expression and tumor mutational burden.
• Oral cavity-originating microbial diversity was associated with MSI in CRC and stomach adenocarcinoma.

Conclusions:

• Intratumoral microbiota composition may differ based on MSI status.
• Specific intratumoral microbes are associated with improved survival and may influence the tumor microenvironment and host immunity.