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Altered deposition of basement‐membrane molecules in co‐cultures of colonic cancer cells and fibroblasts

Two human colon carcinoma cell lines, HT29 and Caco‐2 were co‐cultured with fetal rat or human skin fibroblasts. Their morphological features, ultra‐structural characteristics at the heterologous cell interface, and the deposition of basement‐membrane molecules [laminin, type‐IV collagen, heparan sulfate proteoglycan (HSPG)] at the epithelialstromal junction were analyzed. The 2 cell lines behaved differently. HT29 cells did not spread on the fibroblasts and grew as clusters, while Caco‐2 cells formed a monoiayer over the fibroblastic feeder layer. Only the latter carcinoma cells exhibited cytoplasmic processes towards the fibroblasts and, after 5 days in co‐cultures, a structured basement membrane (BM). The immunocytochemicai analysis of the BM constituents revealed the absence of the molecules studied at the sites of heterologous contacts in the case of HT29 cells. In contrast, in the co‐cultures comprising Caco‐2 cells, laminin and type‐IV collagen were progressively deposited in a polar fashion at the epithelial‐fibroblastic interface which, however, remained devoid of HSPG molecules. Together with earlier data indicating a dual origin of the BM molecules located at the epithelial‐fibroblastic interface in normal intestine, the present study shows that the cancer cells as well as the fibroblastic ones under the influence of carcinoma cells display an altered capacity to synthesize and/or secrete BM molecules. The extent of such abnormalities correlates with the differentiation of the cells. Finally, these modifications occur concomitantly with alterations in cell interactions which vary among cell lines.