Discovering Fusobacterium nucleatum's Impact on Breast Cancer Progression and Treatment with POx Micelle Technology

PROJECT SUMMARY Breast cancer (BC) is a complex and heterogeneous disease, further complicated by the discovery of tumor- specific microbiota, including Fusobacterium nucleatum (F. nucleatum), which has been detected in 30% of BC cases and is associated with increased malignancy. While F. nucleatum has been correlated with worse clinical outcomes in BC patients, the mechanisms underlying its effects remain unclear, partly due to limited research on how this bacterium alters tumor biology and immune responses in immunocompetent, clinically relevant BC models. Our preliminary studies reveal that F. nucleatum infection accelerates triple-negative BC (TNBC) growth. This raises the critical question of whether F. nucleatum fosters a pro-tumorigenic, immunosuppressive tumor microenvironment (TME) that diminishes the efficacy of chemotherapy in BC. We hypothesize that F. nucleatum and its metabolites drive an immunosuppressive TME, decreasing immune surveillance of the cancer by T-cells and impairing the response to chemotherapy. Targeting the infection will restore efficacy by increasing immune surveillance, transforming infected tumors into ‘hot’ tumors that are more responsive to treatment. In Aim 1, we will characterize the relationship between F. nucleatum infection and changes in the TME, and their collective role in promoting disease progression in BC. We will use two immunocompetent models of TNBC, 4T1 and T11-APOBEC (T11-AB), which have been comprehensively profiled and demonstrate strong genomic and genetic similarities to human TNBC. We will quantify the TME metabolome, transcriptome, and immune cell populations, alongside primary tumor growth, metastatic spread, and lifespan. We will perform the most extensive immunophenotyping of F. nucleatum-infected BC to date using spectral flow cytometry. Given the limited research on F. nucleatum’s role in BC, our study will address a critical gap by generating a detailed profile of the functional and immune alterations caused by this infection and its relation to disease outcomes. In Aim 2, we will tackle the challenge of eradicating F. nucleatum without disrupting the gut microbiota, which is crucial for maintaining immune function and overall health. Conventional antibiotic treatment can lead to dysbiosis, impair immune responses, and potentially promote tumor progression. To avoid this, we will use a novel combination therapy involving multi-drug polymeric micelles (MDPMs) to co-deliver anticancer drug, paclitaxel and the antibacterial antibiotic metronidazole directly to the tumors via intravenous administration. This approach aims to bypass the gastrointestinal tract, targeting both cancer and bacteria in the TMBC tumor while minimizing off- target antibiotic effects and preserving beneficial gut microbiota. By integrating these strategies, our study will provide critical insights into how F. nucleatum contributes to BC progression and offer a promising, microbiome- sparing therapeutic strategy for treating bacteria-infected tumors.