title: Effect of cytosine arabinoside on the human immunosystem: metabolism and cytotoxicity studied with mitogen-stimulated normal blood lymphocytes in vitro.
abstract: The toxicity, metabolic effects and metabolism of cytosine arabinoside (Ara-C) were studied with normal human peripheral blood PHA-stimulated mononuclear cells in vitro. Clinically relevant Ara-C concentrations were toxic against mitogen-stimulated blood lymphocytes. Dose-dependent effects included: (i) increased cell loss, (ii) decreased DNA synthesis assessed by 3H-thymidine incorporation, (iii) decreased blastic transformation, (iv) decreased protein synthesis assessed by 14C-leucine incorporation, (v) an inhibition of the production of new cells, (vi) a delay in the proceeding of the PHA-stimulated cells to the cell cycle, (vii) an arresting of the cells in the S-phase, and (viii), a dose-dependent decrease of the number of mitoses in Ara-C-treated cultures. The mode of cell death was of the delayed type. The toxicity of Ara-C was effectively reversed by an excess of deoxycytidine, but not by cytidine or other conventional nucleosides, which is highly suggestive that the molecular mechanism of Ara-C toxicity is based on its anti-metabolic role in the salvage pathway of biosynthesis of DNA deoxycytidine. In fact, we demonstrated that Ara-C is metabolized to Ara-CTP and to a lesser extent also incorporated into DNA in human PHA-stimulated lymphocytes. Ara-C significantly decreased its own uptake and DNA incorporation. On the other hand, uracil arabinoside, which was the major catabolic product of Ara-C, was not toxic to human PHA-stimulated T-cells. The antiproliferative effect of Ara-C against human T-cells resembled that previously demonstrated with various cancer cell types.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Laboratory of Molecular Hematology, University of Oulu, Finland.
authors.forename: J A
authors.initials: JA
authors.lastname: Vilpo
authors.forename: T
authors.initials: T
authors.lastname: Veromaa
authors.forename: E
authors.initials: E
authors.lastname: Eerola
mesh_terms: D002453:Cell Cycle / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D003561:Cytarabine / Q000378:metabolism / Q000494:pharmacology*; D004247:DNA / Q000096:biosynthesis; D006801:Humans; D007107:Immune System / Q000187:drug effects*; D066298:In Vitro Techniques; D008213:Lymphocyte Activation; D008214:Lymphocytes / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D010835:Phytohemagglutinins / Q000494:pharmacology; D014176:Protein Biosynthesis
chemical_list: D010835:Phytohemagglutinins; D003561:Cytarabine; D004247:DNA