Resistance to methotrexate is associated with selective changes of alpha 2,6- and alpha 2,3-sialyltransferase activities toward N-acetyllactosaminic sequences in human colon cancer cell line HT-29.
In previous works we established that the alpha 2,6-sialyltransferase acting on N-acetyllactosaminic sequences [alpha 2,6(N)ST, E.C. 2.4.99.1] behaves, in colonic cells, as an oncodevelopmentally regulated enzyme. Subpopulations of the human colon cancer cell line HT-29 adapted to grow in 10(-5) M methotrexate (MTX), permanently retain the ability to differentiate as mucus-secreting cells when kept confluent for extended periods of time [Lesuffleur et al. (1991) J. Cell Biol. 115, 1409-1418]. In this study we have compared the activities of five sialyltransferases acting on N- or O-linked chains of glycoproteins in parental HT-29 and in the 10(-5) M MTX-resistant variant. Both cell lines were studied during the exponential phase of growth as well as after a long period of postconfluent culture (28-30 days). Regardless the culture conditions, resistance to 10(-5) M MTX is associated with a virtual disappearance of alpha 2,6(N)ST activity. This change results in a dramatic reduction of the reactivity of cell membranes with the fluorescent lectin from Sambucus nigra, specific for alpha 2,6-sialylated structures. The activity of the alpha 2,3-sialyltransferase which acts on N-acetyllactosaminic sequences increases about two times in postconfluent cultures of 10(-5) M MTX-resistant cells, suggesting a close relationship with the differentiation degree. No significative changes were observed in the activity of other sialyltransferases.
Dall'Olio
F
F
Dipartimento di Patologia Sperimentale, Università di Bologna, Italy.
Malagolini
N
N
Guerrini
S
S
Serafini-Cessi
F
F
D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D003110:Colonic Neoplasms; D004351:Drug Resistance / Q000502:physiology*; D005434:Flow Cytometry; D006801:Humans; D007700:Kinetics; D037102:Lectins; D008727:Methotrexate / Q000633:toxicity*; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000096:biosynthesis; D037121:Plant Lectins; D054788:Ribosome Inactivating Proteins; D012799:Sialyltransferases / Q000378:metabolism*; D013379:Substrate Specificity; D014407:Tumor Cells, Cultured; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase; D000094663:beta-Galactoside alpha-2,3-Sialyltransferase
D037102:Lectins; D009844:Oligosaccharides; D037121:Plant Lectins; C050600:Sambucus nigra lectins; D012799:Sialyltransferases; D054788:Ribosome Inactivating Proteins; D008727:Methotrexate; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase; D000094663:beta-Galactoside alpha-2,3-Sialyltransferase; C000722087:ST3GAL1 protein, human