EFFECT OF TGF-BETA ON DIFFERENTIATED ORGANOIDS OF THE COLON-CARCINOMACELL-LINE LIM-1863

The LIM 1863 colon carcinoma cell line grows in suspension as morpholo gically and functionally organized organoids in serum-containing mediu m. Addition of TGF-beta caused the organoids to adhere and inhibited D NA synthesis. A 20 min incubation with TGF-beta was sufficient to indu ce adherence and this could be inhibited by cycloheximide. The adhesio n and DNA synthesis inhibition were demonstrated to be separate events . We were not able to detect any changes in matrix or cell membrane an tigens. Similarly there were no changes in synthesized proteins (by tw o-dimensional gel electrophoresis), and no upregulation of proteoglyca n. When adhered organoids were lysed from the tissue culture plastic s urface, untreated organoids adhered to this surface. This 'conditioned ' surface was destroyed by trypsin but not collagenase or medium from normal LIM 1863 cultures. However, the adherent phenotype was prevente d when organoids were treated with transforming growth factor-beta (TG F-beta) in the presence of medium conditioned by normal LIM 1863 cultu res rather than in fresh medium. The adhesion process was inhibited by an antibody (QE2E5) against beta(1) integrin although no quantitative changes in integrins were observed (by immunoprecipitation or RNA ana lysis). A second anti-beta(1) integrin antibody (61.2C4) inhibited LIM 1863 adhesion to collagen but not TGF-beta induced adhesion, implying that TGF-beta induced a specific conformational change or interaction of a beta(1) integrin. In this morphologically structured system TGF- beta induced a number of subtle effects including formation of new ext racellular matrix and conformational change of a beta(1), integrin, ra ther than the major quantitative changes in cell/matrix molecules repo rted previously.