Colon carcinoma cells provide a useful model to study the biochemical processes associated with cell differentiation. Undifferentiated HT29, differentiated HT29MTXϪ3 and HT29MTX Ϫ6 , and Caco2 human colon carcinoma cells have been used to study the production of proteoglycans and to characterize the glycosaminoglycan structure of the heparan sulphate chains. All the cell lines produce mainly a heparan sulphate proteoglycan that is found partly in the extracellular medium and associated to the cell membrane. The heparan sulphate proteoglycans from the media were purified by ion-exchange chromatography and subjected to structural analysis. The heparan sulphate proteoglycan from differentiated cells is larger and more homogeneous in size than the heparan sulphate proteoglycan from undifferentiated HT29 cells. No differences in protein core structure were observed when cells were labeled with [35 S]methionine and the protein cores visualized by gel electrophoresis. Nevertheless, differences in glycosaminoglycan composition were found correlated with the degree of differentiation. The heparan sulphate chains from differentiated HT29MTXϪ3 and HT29MTX Ϫ6 cells have a higher sulphation degree than those from undifferentiated HT29 cells. The heparan sulphate from Caco2 cells is the most highly sulphated species. The differences are mainly attributed to O-sulphate groups. The increase in O-sulphation was more pronounced for D-glucosamine 6-O-sulphate than for L-iduronic acid 2-O-sulphate groups.Keywords : proteoglycan ; glycosaminoglycan; colon carcinoma; perlecan; cell differentiation.Sulphated glycosaminoglycans, and particularly heparan sul-changes in protein glycosylation occur during the process of cell differentiation in the HT29 cell line (Wice et al., 1985; Ogierphate (HS), play an important role in cellϪcell and cellϪsub-strate interactions, cell attachment and spreading, growth factor Denis et al., 1988). Among the other established colon carcinoma cell lines, the Caco2 cell line has been widely used beregulation and cell transformation (Gallagher, 1989; Kjellén and Lindahl, 1991;Hardingham and Fosang, 1992; Yanagishita and cause it spontaneously expresses a very high degree of enterocytic differentiation (Rousset, 1986). Hascall, 1992). In particular, alterations in proteoglycan composition and/or structure have been described in several transHeparan sulphate proteoglycans have been implicated in a number of fundamental cell-biological phenomena. The HS side formed cells (Robinson et al., 1984;Keller et al., 1980; Lévy et al., 1990;Knudson et al., 1990;Pejler and David, 1987; Winter-chains have the ability to bind, in a more or less specific fashion, to a variety of proteins, including extracellular matrix proteins, bourne and Mora, 1981). A good model to investigate the relationship between proteoglycan structure and cell differentiation enzymes, enzyme inhibitors, growth factors and other cytokines (Gallagher, 1989;Spillmann and Lindahl, 1994; Salmivirta et would be a cell line with a wide range of phenotyp...
