Follicle-like structures formed by intestinal cell lines derived from the HT29-D4 adenocarcinoma cell line: Morphological and functional characterization

When cultured in high glucose containing medium, the human colon carcinoma cell line HT29-D4 and a clone derived by transfection with the MDR1 cDNA (M DR31) form multilayers of unorganized cells which are not polarized and are linked by desmosomes. Within these multilayers appear spontaneously large multicellular follicle-like-structures (FLS) where polarized cells linked b y tight junctional complexes surround a lumen. Electron microscopy showed t hat some FLS display well developed brush borders with densely packed micro villi. Others have irregularly oriented microvilli of various lengths or ar e even completely devoid of apical differentiation. The lumen contains a va riable amount of amorphous osmiophilic material. The apical surface of FLS forming cells express dipeptidylpeptidase TV, carcinoembryonic antigen, the mucin MUC1 and for the transfected cells the gp-170 protein. The organic a nion fluorescein is transported from the cell to the lumen of FLS. Rhodamin e 123, a substrate of the gp-170 ABC transporter is also concentrated in th e lumen formed by MDR31 cells. Verapamil and cyclosporine A inhibited this last transport. Cyclic AMP stimulates the formation of these structures sin ce treatment of post-confluent multilayers dramatically increased the numbe r of FLS in HT29-D4 and MDR31 cell cultures within 24 h. The spontaneous fo rmation of these morphologically and functionally polarized structures appe ared at random and might respond to the coincidence of fluctuating paramete rs of the regulatory pathways (cAMP, Ca2+). (C) Elsevier, Paris.