Association of Fusobacterium nucleatum in the Progression of Colorectal Cancer

Abstract

ƒThis is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/ license/by-nc/3.0/). Colorectal cancer (CRC) is recognized as the third most common malignancy worldwide. Previous studies indicated several genetic and environmental factors that potentiate CRC. However, the role of microbiota in the etiology of CRC is becoming a major concern nowadays. Fusobacterium nucleatum (F. nucleatum), an anaerobic bacterium, mostly resides in the oral cavity and is a causative agent of various oral inflammatory diseases. It is evident from the recent studies that F. nucleatum is present in abundance in the CRC tissues as compared to the adjacent normal tissues. F. nucleatum has certain virulence factors like FadA and Fap2 which help in its adhesion to the mucosal cells and promotes carcinogenesis. Besides that, these virulence factors induce cytokine production and recruitment of inflammatory cells, hence it creates an environment favorable for neoplastic growth. Furthermore, F. nucleatum can suppress the host immune system by interfering with normal functions of macrophages, dendritic cells, T cells, tumor-associated neutrophils and natural killer cells. It was also revealed that CRC patients with high numbers of F. nucleatum showed drug resistance and cancer recurrence. From the previous investigations, it was concluded that F. nucleatum has a diagnostic as well as prognostic value for CRC patients. In the present study, we have outlined the current data on the detection methods, pathogenic mechanisms, immunosuppression effects and clinical management of F. nucleatum-associated CRC.