UP-REGULATION OF LYSOZYME PRODUCTION IN COLONIC ADENOMAS AND ADENOCARCINOMAS

Aims: The presence of lysozyme protein in some gastric adenomas and ad enocarcinomas has been well documented, There have been relatively few studies investigating the presence of lysozyme in tumours of the larg e intestine and they show contrasting results, We aim to investigate t he cellular source and expression of lysozyme in colonic adenomas and adenocarcinomas. Methods and results: We randomly selected 29 and 27 c olonic adenomas and adenocarcinomas, respectively, Using in-situ hybri dization (ISH) and immunohistochemistry (MC), we found an up-regulatio n of lysozyme in the dysplastic epithelium of all the adenomas studied , with more than 80% of cases expressing moderate to strong signals, A lthough the up-regulation of lysozyme was also observed in adenocarcin omas, only 30% of the cases showed moderate to strong signals, mostly with an uneven distribution, Down-regulation of lysozyme in the severe ly dysplastic and invasive foci were noted in some cases of adenoma wi th malignant transformation. Normal colonic glands were consistently n egative for lysozyme at both the mRNA and the protein level, but infla med and immature regenerative colonic epithelium at the crypt base sho wed positive signals in a similar pattern to those observed in the dys plastic epithelium of the adenomas. Conclusions: Our results confirm t hat colonic epithelium can produce lysozyme and its expression is up-r egulated in the dysplastic epithelium in adenomas and in invasive canc er cells. It is interesting that regenerative colonic epithelium showe d a similar pattern of lysozyme expression as in adenomas, The loss of lysozyme secreting phenotype in most of the invasive tumours suggests that lysozyme may not confer an advantage to tumour progression.