Expression of lysosome-associated membrane proteins in human colorectal neoplasms and inflammatory diseases

The lysosome-associated membrane proteins (LAMPs)-1 and -2 are major consti tuents of the lysosomal membrane. These molecules are known to be among the most glycosylated proteins of several types of cells and cancer cells, and their expression in cancer cells is marked by a distinct difference in the structures of the oligosaccharides as compared to nonmalignant cells. We a nalyzed by immunohistochemistry the intensity and distribution of LAMP-1 an d LAMP-2 in 9 human colorectal cancer cases and in 16 control cases, includ ing inflammatory diseases (diverticulitis, ulcerative colitis, and Crohn's disease). LAMP proteins were expressed more intensely in the epithelium of colorectal neoplasms than in normal mucosa. (P < 0.05), and no significant differences were found between adenoma and cancer cells (P > 0.05) in the s ame tissue section. Further, in sites of inactive inflammatory diseases and nonneoplastic areas in cancer specimens, no significant increases in epith elial LAM:P proteins were observed, even in the proliferative zone of the l ower crypt epithelium. Northern blot analysis showed increased expression o f LAMP-1 and LAMP-2A in two of three colorectal cancers examined and increa sed LAMP-2B in all three cancers. Our findings suggest that LAMPs are relat ed to neoplastic progression, but there is no direct association between th e expression of LAMP molecules and cell proliferation.