The anaerobic oral microbe Fusobacterium nucleatum has recently gained attention for its ability to colonize tumors in distal sites from its primary niche. Its presence in the tumor tissue is linked to tumor growth, metastasis, and resistance to chemotherapy. While bacterial removal reduces tumor burden, sustained systemic antibiotic treatment has severe side effects. To interfere with tumor colonization in a more selective manner, it is essential to understand the molecular host factors that enable fusobacterial colonization of the tumor environment.
In order to address this question, we established a hypoxic colonization protocol using three different colon cancer cell lines (Caco-2, HT-29, and HCT116) and GFP-expressing fusobacteria in physiological 1 % O2 conditions. Interestingly, we observed different colonization rates for each cell line. This might be due to distinct cellular properties such as observed differences in cytokine profiles that could affect the colonization of fusobacteria. To further dissect host and bacterial gene expression changes upon colonization, we separated bystander from colonized cells using fluorescence-activated cell sorting and performed dual RNA-seq. This method allows monitoring gene expression changes of both organisms in parallel as the separation of host and bacterial transcripts is done in silico, which increases the sensitivity for detecting bacterial-induced responses in colonized cells. We will be focusing further analysis on differentially expressed genes to determine key factors that facilitate successful colonization by F. nucleatum, with the ultimate goal of defining new targets for specific intervention.