Lumican and decorin are differentially expressed in human breast carcinoma

Previous studies have shown that lumican is expressed and increased in the stroma of breast tumours. Lumican expression has now been examined relative to other members of the small leucine-rich proteoglycan gene family in nor mal and neoplastic breast tissues, to begin to determine its role in breast tumour progression. Western blot study showed that lumican protein is high ly abundant relative to decorin, while biglycan and fibromodulin are only d etected occasionally in breast tissues (n = 15 cases). Further analysis of lumican and decorin expression performed in matched normal and tumour tissu es by in situ hybridization showed that both mRNAs were expressed by simila r fibroblast-like cells adjacent to epithelium. However, lumican mRNA expre ssion was significantly increased in tumours (n = 34, p<0.0001), while deco rin mRNA was decreased (p = 0.0002) in neoplastic relative to adjacent norm al stroma. This was accompanied by a significant increase in lumican protei n (n = 12, p = 0.0122), but not decorin. Further evidence of altered lumica n expression in breast cancer was manifested by discordance between lumican mRNA and protein localization in some regions of tumours but not in adjace nt morphologically normal tissues. It is concluded that lumican is the most abundant of these proteoglycans in breast tumours and that lumican and dec orin are inversely regulated in association with breast tumourigenesis. Cop yright (C) 2000 John Whey & Sons, Ltd.