https://www.selleckchem.com/products/bi-2865.html BACKGROUND/PURPOSE Colorectal cancer (CRC) is one of the most common malignant tumours and is associated with a high mortality rate due to the lack of specific biomarkers available for early diagnosis, targeted therapies and prognostic surveillance. In the present study, we investigated the function of Numb and its underlying mechanism in colorectal cancer. METHODS Immunohistochemical staining and clinicopathological analysis were used to assess the expression of Numb and its clinical significance in patients with colorectal cancer. Quantitative real-time polymerase chain reaction, cell proliferation, western blot, wound healing, Transwell and TOP/FOP flash reporter assays were used to investigate the function of Numb and its underlying mechanism in colorectal cancer. RESULTS Numb expression was down-regulated and negatively correlated with the depth of invasion, tumour size, metastasis, TNM stage and EMT markers in colorectal cancer specimens. Numb negatively regulates the EMT, proliferation, invasion, migration and the Wnt signalling pathway in vitro, as well as tumour growth and metastasis in vivo. Furthermore, activation of the Wnt signalling pathway by Wnt-3A negated the effect of Numb overexpression, while inhibition of the Wnt signalling pathway by IWR-1 impaired the effect of the Numb knockdown on the EMT. CONCLUSION Numb downregulation is a common event in patients with colorectal cancer and is closely correlated with cancer progression and a poor prognosis. Numb functions as a tumour suppressor in colorectal cancer, and its tumour suppressor function is mediated by negative regulation of the EMT through the Wnt signalling pathway.The gastrointestinal tract houses a reservoir of bacterial-derived enzymes which can directly catalyze the metabolism of drugs, dietary elements, and endogenous molecules. Both host and environmental factors may influence this enzymatic activity, with the potential to dictate the a