Investigating the clinical and molecular significance of <i>Fusobacterium nucleatum</i> in breast cancer

Greater understanding of the factors which promote tumour progression and metastatic development is required to improve mortality from this disease. In recent years, a distinct microbiome has been detected in the breast (2).

The oral anaerobic bacterium, <i>Fusobacterium nucleatum</i> is enriched in breast tumour tissue compared to matched healthy tissue and is associated with mammary tumour growth and metastatic progression in mouse models (2, 3). Additionally, in colorectal and oral cancers, <i>F. nucleatum</i> is shown to modulate metastasis, immune escape and inflammation within the tumour microenvironment (4, 5). This thesis aimed to investigate the clinical and molecular implications of <i>F. nucleatum</i> on the tumour microenvironment and progression of breast cancer.<br><br>Here, the prevalence, location, and clinicopathological characteristics of <i>F. nucleatum</i> was investigated using an RNA in situ hybridisation technology (RNA-scope®) and using RNA-sequencing data in 3 different breast cancer cohorts, confirming the presence of the bacterium within the tumour tissue. <i>F. nucleatum</i> presence within the breast cancer cohorts was correlated with clinicopathological features, identifying a significant association between<i> F. nucleatum</i> and higher grade tumours.