Colorectal adenomas produce lysozyme

Lysozyme is an innate non-immunologic antibacterial enzyme produced by the Paneth cells of the upper intestinal tract. Lysozyme is not normally secreted in the lower intestinal tract. Previous reports indicate, however, that lysozyme may be secreted by colorectal neoplasias. The aim was to audit lysozyme expression in colorectal diseases including neoplasias. For that purpose, sections were stained with lysozyme (Muramidase), Ki67 (MIB1) and CD 68. Intense lysozyme overexpression (+++) was compared among 177 colorectal tissues: 35 having normal mucosa, 20 regenerative mucosa in inflammatory bowel disease (IBD), 2 inflammatory polyps, 3 collagenous colitis, 2 melanosis coli, 21 hyperplastic polyps, 42 tubular adenomas, 9 serrated adenomas, 30 villous adenomas and 13 invasive carcinomas. Intense lysozyme overexpression (+++) was found in 9.5% of the hyperplastic polyps, in 97.6% of the tubular adenomas, in 88.9% of the serrated adenomas, in 93.3% of the villous adenomas, in 76.9% of the carcinomas, but in none of the other tissues investigated. Neoplastic colorectal cells may acquire the capacity to produce lysozyme. The presence of that enzyme may not be a haphazard, capricious event in mutated colorectal epithelial cells but part of a more elaborate molecular behavior, not necessarily antibacterial. Recently, it was demonstrated that patients having lysozyme-secreting breast carcinomas were associated with a favorable prognosis. Whether lysozyme expression has any bearing on the biological behavior of colorectal carcinomas remains to be elucidated. Lysozyme overexpression (+++) also occurred in 2 of the 21 hyperplastic polyps, suggesting that intense lysozyme production might herald a possible dysplastic evolution in some hyperplastic polyps.