Modulation of HT-29 human colonic cancer cell differentiation with calmidazolium and 12-O-tetradecanoylphorbol-13-acetate.
The effects of a protein kinase C activator, 12-O-tetradecanoylphorbol-13-acetate (TPA), and of a calmodulin antagonist calmidazolium (CZ), on a human colonic cancer cell line HT-29 were analyzed. HT-29 cells are undifferentiated in standard culture conditions (HT-29 G+) and display an enterocytic differentiation when cultured in glucose-deprived medium (HT-29 G-). Early effects of TPA and CZ on the localization of cytoskeletal proteins (caldesmon, alpha-actinin and vinculin) and on cell proliferation were examined. Differentiation of the cells was assessed after 4 weeks on the basis of ultrastructural and functional characteristics of enterocytic polarity, presence of apical brush borders, expression of brush border membrane antigens (Caco 5/50 and sucrase-isomaltase), and segregation of calmodulin to the brush border cytoskeleton. TPA treatment of HT-29 G+ or G- cells induced early morphological and cytoskeletal alterations: the cells rounded up and lost their stress fibers with the associated caldesmon, alpha-actinin, and vinculin. TPA did not modify the differentiation of G- cells, but induced in G+ cells the expression, although limited, of enterocytic differentiation characteristics. Addition of CZ to HT-29 G- cells enhanced their differentiation state but did not provoke any early morphological or cytoskeletal alterations. No effects of CZ on HT-29 G+ cells were obvious. The results suggest that protein kinase C, the TPA receptor, is involved in the triggering of HT-29 G+ cell differentiation whereas calmodulin-dependent functions would be implicated in HT-29 G- cell maturation.
D000951:Antigens, Neoplasm / Q000032:analysis; D002147:Calmodulin / Q000032:analysis / Q000037:antagonists & inhibitors*; D002148:Calmodulin-Binding Proteins / Q000032:analysis; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D003110:Colonic Neoplasms / Q000473:pathology*; D003599:Cytoskeleton / Q000187:drug effects; D005455:Fluorescent Antibody Technique; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D010766:Phosphorylation; D013394:Sucrase-Isomaltase Complex / Q000032:analysis; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
D000951:Antigens, Neoplasm; D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; D007093:Imidazoles; C031938:calmidazolium; D013394:Sucrase-Isomaltase Complex; D013755:Tetradecanoylphorbol Acetate