Inhibiting neutrophils activation by long-term administration of 5-amino salicylic acid reduces colitis-associated colorectal tumor burden in ApcMin/+ mice

Objective The risk of ulcerative colitis (UC)-associated colorectal cancer (CRC) increases with the duration of UC. Oral 5-aminosalicylic acid (5-ASA) formulations are the first-line treatment for mild-to-moderate UC; nevertheless, preventive effect of oral 5-aminosalicylic acid (5-ASA) formulations on UC-associated CRC remains unsolved. We investigated the impact of 5-ASA to colitis-associated neoplasia in C57BL/6J-ApcMin heterozygous (ApcMin/+) mice. Design ApcMin/+ mice exposed to 1.5 w/v% dextran sulfate sodium (DSS) ad libitum for 3 days followed by 25 days of tap water to develop colitis-associated neoplasia. Mice were intracolorectally administrated with 5-ASA to evaluate the effects on the number of tumors. The mechanism of action was presumed by microarray analysis using in vivo samples and was confirmed by in vitro culture of HT-29, a human colorectal adenocarcinoma cell line with supernatant of human primary neutrophils. Results A remission between acute and recurrent episodes of diarrhea, which were ameliorated by 5-ASA treatment were observed in this model. The number of tumors was reduced by continuous 5-ASA administration in this model. This reduction was abolished by withdrawal of 5-ASA in remission period compared to continuous 5-ASA administration. Microarray analysis revealed that neutrophils were involved in the protective mechanism of 5-ASA against proliferation of tumors. Additionally, calprotectin production from human primary neutrophil as activation marker was strongly correlated with proliferation of HT-29. ApcMin/+ mice were given drinking water supplemented with 1.5 w/v% dextran sulphate sodium (DSS) for 3 days to induce colitis, and were intracolorectally administrated with 5-aminosalicylic acid (5-ASA) or Saline (Control) for 28 days. ApcMin/+ mice (Sham) were given drinking water alone for 28 day. Mice of each groups (Sham, 5-ASA and Control) were sacrified and were collected macroscopically distinguished non-tumor regions in colon on day 28.