Tumour microbiota activities associated with local recurrence in ER + PR + breast cancer

PurposeThis study aimed to compare tumour microbiota characteristics as potential recurrence predictors in estrogen receptor-positive (ER+) and progesterone receptor-positive (PR+) breast cancer.MethodsFormalin-fixed paraffin-embedded (FFPE) tumour tissues were obtained from 52 patients with ER + PR + breast cancer, and patients were retrospectively followed up for over 7 years. Patients were categorized into three groups: local recurrence (n = 13), distant metastasis (n = 17), and no recurrence (n = 22). Gene expression profiles and microbial activity in tumour tissues were analyzed by microarray and 16S rRNA sequencing, respectively, from the same total RNA extracted from FFPE samples.ResultsCompared to nonrecurrent tumours, the ratio of strict anaerobic bacteria Muribaculaceae to aerobic bacteria Pseudomonas activity was significantly upregulated in tumours with local recurrence, while no significant difference was observed in the distant metastasis group. Furthermore, the Muribaculaceae/Pseudomonas activity ratio showed a significant correlation with the cancer relating genes expression of PLA2G5, MSMO1, and three small nuclear RNAs across all 52 tumours.ConclusionThis study provided the first evidence of distinctive features of tumor-associated microbiota in ER+/PR + breast cancer patients with local recurrence, suggesting their potential as predictive biomarker for local recurrence. However, these findings require further validation in larger cohorts due to the limited sample size.