Association of Fusobacterium nucleatum infection with the clinicopathological characteristics in colorectal cancer patients

Background Colorectal cancer (CRC) is a global health problem. The gut microbiome is now recognized as an important underlying factor to the initiation and progression of CRC. Fusobacterium nucleatum (FN) is one of the most studied bacteria in the aetiology of CRC. This study provided cohort evidence on the association of FN infection with clinicopathologic features in CRC patients.Methods We analysed the cancerous and adjacent non-cancerous formalin-fixed paraffin embedded (FFPE) tissue of 83 CRC patients from a single medical centre in Malaysia. TaqMan probe-based qPCR targeting the 16S rRNA gene was used to detect the presence of FN in the extracted FFPE DNA. The differences in FN expression between cancer and non-cancer tissues were evaluated. Association studies between FN infection in the tumour and relative FN abundance with available clinical data were conducted.Results FN was more abundant in the cancerous tissue compared to non-cancerous tissue (p = 0.0025). FN infection in the tumour was significantly associated with lymph node metastasis (p = 0.047) and cancer staging (p = 0.032), but not with other clinicopathologic variables. In double-positive patients where FN was detected in both cancerous and non-cancerous tissue, the expression fold-change of FN, calculated using 2-Delta &Delta CT formula, was significantly higher in patients with tumour size equal to or greater than 5 cm (p = 0.033) and in KRAS-mutated patients (p = 0.046).Conclusions FN is enriched in CRC tumour tissue and is associated with tumour size, lymph node metastasis, cancer staging, and KRAS mutation in this single-centre small cohort study.