Induction of deoxycytidine kinase by 5-azacytidine in an HL-60 cell line resistant to arabinosylcytosine Journal Article
| Authors: | Kong, X. B.; Tong, W. P.; Chou, T. C. |
| Article Title: | Induction of deoxycytidine kinase by 5-azacytidine in an HL-60 cell line resistant to arabinosylcytosine |
| Abstract: | Induction of 2'-deoxycytidine kinase (dCK) by 5-azacytidine (5-Aza-C) in a dCK-deficient HL-60 cell line resistant to 1-β-D-arabinofuranosylcytosine (Ara-C) (HL-60/Ara-C) was examined by measurement of the incorporation of [3H]deoxycytidine ([3H] dCyd) into cellular DNA, the kinetic properties of purified dCK, the cytotoxic potency (IC50 values), and the DNA methylation patterns of 5-Aza-C-treated and untreated cells. Following a 72-hr exposure to 1 μM 5-Aza-C, the incorporation of [3H]dCyd into DNA was increased 6-fold and the total dCK activity was increased 12-fold, with a peak for both on day 6. The onset of dCK induction was dependent on the length of exposure time. The IC50 values for cell growth inhibition by Ara-C on day 3 were 0.08 μM for HL-60 cells, 12.5 μM for HL-60/Ara-C cells, and 0.55 μM for HL-60/Ara-C cells pretreated with 5-Aza-C for 40 hr. The K(m) and V(max) of dCyd for HL-60 dCK were similar to those for 5-Aza-C-induced HL-60/Ara-C dCK. The restriction enzymes HpaII, which cleaves CCGG sequences but cannot cleave at sites methylated at the internal cytosines (5'-C(Me)CGG), and MspI, which cleaves sequences with internal methylated cytosine but cannot cleave at sites methylated at external cytosines (5'(Me)CCGG), were used for DNA methylation pattern determination. The newly synthesized DNA of HL-60 wild-type cells was cleaved by MspI to a greater extent than that of HL-60/Ara-C cells. After exposure to 1 μM 5-Aza-C for 40 hr, methylation patterns of newly synthesized DNA reverted in HL-60/Ara-C cells to a clevage pattern similar to that in HL-60 wild-type cells. When compared with untreated control, DNAs from 5-Aza-C-treated resistant cells were cleaved to a greater extent by MspI than by HpaII, suggesting that internal cytosine-residue methylation was relatively uninhibited. The data given above suggest that 1) dCK in HL-60/Ara-C cells was induced by 5-Aza-C and the resistance to Ara-C in the cells was partially reversed by 5-Aza-C, 2) the induced enzyme was similar in terms of its kinetic properties to the wild-type enzyme, 3) DNA from HL-60/Ara-C cells may have more methylation at the external cytosine residues of 5'-CCGG sequences than DNA from wild-type HL-60 cells, and 4) the DNA methylation at external cytosine residues was inhibited (i.e., hypomethylation state) when dCK expression was induced by 5-Aza-C treatment. |
| Keywords: | controlled study; human cell; methylation; cytarabine; dna synthesis; drug resistance; tumor cells, cultured; dna methylation; time factors; molecular sequence data; kinetics; leukemia, myeloid; dna, neoplasm; base sequence; radioisotope; deoxycytidine; azacitidine; enzyme induction; tritium; dose time effect relation; deoxycytidine kinase; cell strain hl 60; human; priority journal; article; leukemia, experimental; support, non-u.s. gov't; support, u.s. gov't, p.h.s. |
| Journal Title: | Molecular Pharmacology |
| Volume: | 39 |
| Issue: | 2 |
| ISSN: | 0026-895X |
| Publisher: | The American Society for Pharmacology and Experimental Therapeutics |
| Date Published: | 1991-02-01 |
| Start Page: | 250 |
| End Page: | 257 |
| Language: | English |
| PUBMED: | 1705001 |
| PROVIDER: | scopus |
| DOI/URL: | |
| Notes: | Source: Scopus |
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