Background: The mucus layer coating the gastrointestinal tract is the front line of innate host defense. MUC2 is the major secretory mucin synthesized and secreted by goblet cells, whereas goblet and absorptive cells express membrane-bound mucins such as MUC1 in the apical membrane. MUC1 plays a role in tumorigenesis through changes in intracellular signaling, adhesion and migration and by increasing resistance to apoptosis. MUC2 gene product either functions as a tumor suppressor or contributes to the function of a tumor suppressor.
Aim: To investigate the expression profile of MUC1 and MUC2 in normal, inflammed and neoplastic lesions of the colon and also to analyze the immunohistochemical expression of MUC1 and MUC2 and their relationship to the site, histological differentiation and stage of colorectal carcinoma.
Patients and Methods: Thirty patients with colorectal carcinomas underwent surgical resections, 15 patients underwent endoscopically resected colorectal adenoma, 15 patients subjected to endoscopic biopsy specimens of ulcerative colitis and a 10 control cases of colorectal specimens taken from the free resection margins of colectomy specimens were included in this study.All tissue specimens were subjected to MUC1 and MUC2 immunohistochemical staining using monoclonal antibodies.
Results:The positive expression rates of MUC1 and MUC2 in colorectal carcinoma were 76.7% and 60% respectively.MUC1 immunoreactivity was detected in 33.3% of colorectal adenomas whereas MUC2 expression was observed in 93.3% of cases.MUC2 expression was noted in all cases of ulcerative colitis(100%), while MUC1 was expressed in 40% of cases.The expression rates of MUC1 and MUC2 in control cases were zero and 100% respectively.MUC1 expression was significantly higher in carcinomas as compared with UC and adenomas, while MUC2 expression was significantly lower in carcinomas as compared with UC and adenomas.MUC1 expression was significantly higher in colorectal adenocarcinomas, whereas MUC2 was significantly expressed in mucinous carcinomas ( P≤0.05).No significant correlation was found between expression of MUC1 or MUC2 and histological grade ( P˃0.05).High significant association was found between advanced tumor stage and MUC1 expression ( P≤0.05), while MUC2 expression was significantly correlated with lower tumor stages.No significant correlation was found between expression of MUC1or MUC2 and tumor location ( P˃0.05)
Conclusion:We conclude that, Up-regulation of MUC1 and down-regulation of MUC2 expression could be involved in carcinogenesis and progression in colorectal tumors and reflect the prognosis to a certain extent. However, further studies of mucin changes in cancer and inflammation are warranted not only as diagnostic and prognostic markers but also as therapeutic targets.