title: Cytotoxic activity and mechanism of action of 5-Aza-2'-deoxycytidine in human CML cells.
abstract: We investigated the cytotoxic activity and some aspects of the mode of action of 5-aza-2'-deoxycytidine (Aza-dC) in 21 primary cultures of leukemic cells freshly obtained from patients with chronic myeloid leukemia (CML) in blast crisis. The cytotoxic potency of Aza-dC was comparable or even greater than that of 1-beta-D-arabinofuranosylcytosine (Ara-C) in most cases, suggesting that this drug has potential in the therapy of blast crisis of CML. Drug incorporation into DNA was evaluated by exposing leukemic cells simultaneously to 3H-Aza-dC at the concentration of 0.1 micrograms/ml and 14C-thymidine (TdR) used as internal standard. Incorporation of Aza-dC into DNA was detectable in all cases. In 17 samples we evaluated the DNA integrity of leukemic cells exposed to Aza-dC using alkaline elution techniques. The drug caused a detectable amount of DNA alkali labile sites (ALS). DNA-ALS increased in cells exposed to Aza-dC concentrations from 0.1 to 1 microgram/ml but did not further increase at 10 micrograms/ml. A plateau in the levels of DNA-ALS was also seen in human K562 cells exposed to increasing concentrations of Aza-dC from 5 to 10 micrograms/ml, whereas in these cells Aza-dC incorporation into DNA increased with increasing Aza-dC concentrations. Therefore, DNA-ALS caused by Aza-dC are not simply the result of the chemical decomposition of azacytosine molecules incorporated into DNA, but are presumably the result of a saturable DNA repair mechanism (e.g., glycosylases) leading to formation of the apyrimidinic sites.
authors.affiliation: Istituto di Ricerche Farmacologiche Mario Negri, Milano, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Limonta
authors.forename: T
authors.initials: T
authors.lastname: Colombo
authors.forename: G
authors.initials: G
authors.lastname: Damia
authors.forename: C V
authors.initials: CV
authors.lastname: Catapano
authors.forename: V
authors.initials: V
authors.lastname: Conter
authors.forename: M
authors.initials: M
authors.lastname: Gervasoni
authors.forename: G
authors.initials: G
authors.lastname: Masera
authors.forename: V
authors.initials: V
authors.lastname: Liso
authors.forename: G
authors.initials: G
authors.lastname: Specchia
authors.forename: G
authors.initials: G
authors.lastname: Giudici
mesh_terms: D000970:Antineoplastic Agents / Q000378:metabolism / Q000494:pharmacology* / Q000627:therapeutic use; D001374:Azacitidine / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D001752:Blast Crisis; D003561:Cytarabine / Q000494:pharmacology; D004273:DNA, Neoplasm / Q000378:metabolism; D000077209:Decitabine; D006801:Humans; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000188:drug therapy*; D013997:Time Factors; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D004273:DNA, Neoplasm; D003561:Cytarabine; D000077209:Decitabine; D001374:Azacitidine