CHARACTERISATION OF THE GUT MICROBIOME AND FUNCTIONAL PROFILE IN ESTROGEN RECEPTOR-POSITIVE BREAST CANCER PATIENTS IN LAGOS, NIGERIA

Abstract

Estrogen receptor-positive (ER+) breast cancer is the most prevalent molecular subtype globally, yet its association with gut microbial composition, functional potential and inflammatory drivers remains uncharacterised in sub-Saharan Africa. Employing the intersection of microbiology, oncology, and genomics, this study investigated the gut microbiome, predicted functional profiles, and systemic inflammatory markers in treatment-naïve ER+ breast cancer patients compared to healthy controls in Lagos, Nigeria. Faecal DNA samples from participants were extracted and analysed using 16S rRNA sequencing on the Illumina MiSeq platform using the QIIME2 pipeline. Microbial diversity was assessed through alpha (Shannon index) and beta diversity (NMDS, PCoA) metrics, and the group differences were tested using the Mann–Whitney test and Kruskal–Wallis, while PICRUSt2 predicted functional pathways with on focus on β-glucuronidase. Concurrently, systemic inflammation was evaluated through the quantification of Interleukin-6 (IL-6) and C-reactive protein (CRP) from blood serum. Analysis revealed no significant differences in alpha diversity between groups (p > 0.05). However, beta diversity demonstrated substantial compositional divergence (PERMANOVA R²=0.11, p=0.02), with cases showing an elevated Firmicutes/Bacteroidota ratio and depletion of Actinobacteriota, including Bifidobacterium and Collinsella. Functional prediction indicated heightened β-glucuronidase activity in ER+ cases, suggesting enhanced estrogen reactivation potential. Inflammatory markers displayed a complex profile, with significantly reduced IL-6 levels in patients despite stable CRP concentrations. These findings characterise distinct gut microbial dysbiosis and functional alterations in Nigerian ER+ breast cancer patients, revealing an estrobolome configuration potentially contributing to pathogenesis. The results underscore the necessity of population-specific microbiome studies and highlight potential biomarkers for early detection and targeted interventions in this understudied population.