title: Overexpression of folate binding protein alpha is one of the mechanism explaining the adaptation of HT29 cells to high concentration of methotrexate.
abstract: The human colon adenocarcinoma cell line HT29 can be adapted to 10(-7)- 10(-4) M concentrations of methotrexate (MTX). Cells adapted to 10(-4) M MTX have an enterocyte-like phenotype with DHFR gene amplification. Presently, we hypothetized that an increased expression of folate binding protein (FBP) may participate to the MTX resistance of 10(-4) MTX HT29 cells. The cDNA FBPalpha/beta-actin ratio of amplified transcripts was 4.8- and 1.5- fold higher in 10(-4) and in 10(-7) M MTX HT29 respectively, than in standard type HT29 cells. An increase of transcript level was observed when decreasing folic acid concentration. PI-PLC cleaved 7.7 times more membrane FBP in 10(-4) M than in 10(-7) M MTX and wild type HT29 cells. In contrast to 10(-7) M MTX cells, growth of 10(-4) M MTX cells was dependent on folic acid concentration and abolished at a concentration lower than 0.9 microM. In conclusion, the adaptive mechanism of HT29 cells resistant to 10(-4) M MTX is the result of the synergistic overexpression of both DHFR and FBPalpha. Overexpression of FBPalpha may be related to the enterocyte-like phenotype of the cells.
authors.affiliation: Laboratory of Cell and Molecular Pathology in Nutrition. INSERM EMI 0014 Medical Faculty, University of Nancy I-54505, Vandoeuvre les Nancy cedex, France.
authors.forename: M
authors.initials: M
authors.lastname: de Nonancourt-Didion
authors.forename: J L
authors.initials: JL
authors.lastname: Guéant
authors.forename: C
authors.initials: C
authors.lastname: Adjalla
authors.forename: C
authors.initials: C
authors.lastname: Chéry
authors.forename: R
authors.initials: R
authors.lastname: Hatier
authors.forename: F
authors.initials: F
authors.lastname: Namour
mesh_terms: D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D002352:Carrier Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D019008:Drug Resistance, Neoplasm; D058973:Folate Receptors, GPI-Anchored; D005492:Folic Acid / Q000494:pharmacology; D019073:HT29 Cells / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D006801:Humans; D008727:Methotrexate / Q000494:pharmacology*; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D054801:Phosphoinositide Phospholipase C; D011485:Protein Binding / Q000187:drug effects; D020033:Protein Isoforms / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D011956:Receptors, Cell Surface; D013762:Tetrahydrofolate Dehydrogenase / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: D000964:Antimetabolites, Antineoplastic; D002352:Carrier Proteins; D058973:Folate Receptors, GPI-Anchored; D020033:Protein Isoforms; D011956:Receptors, Cell Surface; D005492:Folic Acid; D013762:Tetrahydrofolate Dehydrogenase; D010738:Type C Phospholipases; D054801:Phosphoinositide Phospholipase C; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D008727:Methotrexate