Abstract

Glucocorticoids (GCs) are widely used in the treatment of various autoimmune and inflammatory diseases, including inflammatory bowel disease (IBD). However, the effect of GCs on the progression of colitis-associated colorectal cancer (CAC) has not been well explored. In this study, we first established a colorectal cancer model induced by azoxymethane and dextran sulfate sodium (AOM/DSS) and a colitis model induced by DSS in mice. Dexamethasone (DEX) was then administered at different periods of time to determine its effect on tumorigenesis and tumor progression. Meanwhile, body weight, stool property and fecal blood of mice were recorded. At the end of this study, the number and load of tumors were evaluated, and the expression of proteins associated with cell proliferation was analyzed. To evaluate the inflammation in colon, we detected the level of pro-inflammatory cytokine TNFα, and the mucosal infiltration of inflammatory cells. Our results revealed that AOM injection followed by three cycles of drinking water containing 1.5% DSS successfully induced multiple tumor formation in mouse colon and rectum. Both early and late DEX intervention suppressed tumor growth in mouse colorectum, and downregulated the expression of PCNA and cyclin D1. Moreover, DEX treatment significantly inhibited TNFα production, mucosal infiltration of inflammatory cells, and the activity of MAPK/JNK pathway, particularly early DEX intervention. However, we also found that DEX treatment deteriorated the general state of mouse manifested by greater loss of body weight and rectal bleeding. In summary, both early and late DEX interventions significantly ameliorate colonic inflammation and inhibit the progression of AOM/DSS-induced colorectal cancer, at least partly due to the inhibition of MAPK/JNK pathway. It is noteworthy that the deleterious effect on the general condition of mouse may limit the duration of GCs treatment.