The inhibitory effect of polysaccharide from Rhizopus nigricans on colitis-associated colorectal cancer

An extracellular polysaccharide (EPS1-1) of Rhizopus nigricans was found to enhance immunity and reduce colon cancer cell proliferation. Here, the effect of EPS1-1 on a mouse model of colitis-associated cancer (CAC) induced by azoxymethane (AOM)/dextran sodium sulfate (DSS) was investigated. Pathological symptoms, including weight loss, piloerection, hematochezia and insensitivity caused by AOM/DSS, were relieved by EPS1-1. Anatomical results showed a 100% tumor incidence, a series of neoplasms, disordered cell structure and hyperplastic glands in the model group, while the abnormal behaviors were relieved and the tumors decreased in the EPS1-1 group. Compared with the model group, the EPS1-1 group showed decreased oncogenic protein (COX-2, β-catenin, CyclinD1 and C-Myc) expression. TUNEL staining showed that EPS1-1 increased the apoptosis of colon cancer cells in mice. Furthermore, the expression of proliferative proteins (Ki-67 and PCNA) and an antiapoptotic gene transcript (Bcl-2) were significantly down regulated by EPS1-1, while apoptotic gene transcripts (p53 and Bax) were enhanced. In addition, EPS1-1 notably decreased the number of cells positive for CD68, F4/80 and NF-κB and reduced the concentrations of inflammatory factors (TNF-α and IL-6) in serum compared with those in the model group. Taken together, these results suggest that EPS1-1 may be a therapeutic option for the prevention and treatment of CAC.