Biological effects of a relatively low concentration of 1-beta-D-arabinofuranosylcytosine in K562 cells: alterations of the cell cycle, erythroid-differentiation, and apoptosis.
Therapeutic strategies for leukemia are directed to induction of differentiation and apoptosis as well as growth inhibition. One of the key antileukemic agents, 1-beta-D-arabinofuranosylcytosine (ara C), is clinically applied according to these therapeutic aims. However, the molecular effects of 0.1 microg/ml of ara C, a concentration that corresponds to the serum level in leukemic patients on a conventional dose of ara C, have not been well disclosed. Here, we addressed these issues using K562 cells which derived from a blastic crisis of chronic myeloid leukemia. DNA synthesis of treated cells was suppressed from 1-6 h. But, it recovered at 12 h and no further inhibition was observed. The number of cells was not decreased but DNA fragmentation was observed at 72 h. The number of erythroid-differentiated cells also increased to 30% at 72 h. Along with treatment, no marked alteration of mRNAs for cell cycle-regulating genes was found and the retinoblastoma gene product remained hyperphosphorylated throughout treatment. The expression of mRNAs for apoptosis-regulating genes also remained unchanged, except for slight down-regulation of Bax. c-myc protein was not found later than 48 h, and Max mRNA was downregulated. c-jun was immediately induced, followed by the fluctuated expression level along with treatment. These findings suggest that the 0.1 microg/ml ara C changed the proliferation, differentiation and death of K562 cells in a biphasic manner. In the early phase, DNA synthesis was inhibited without altering the expression of cell cycle regulating-genes. In the latter phase, cell death and erythroid- differentiation occurred in accordance with the down-regulation of c-myc.
Yamada
H
H
Department of Internal Medicine (IV), Aoto Hospital, Institute of DNA Medicine, The Jikei University School of Medicine, Tokyo, Japan.
Horiguchi-Yamada
J
J
Nagai
M
M
Takahara
S
S
Sekikawa
T
T
Kawano
T
T
Itoh
K
K
Fukumi
S
S
Iwase
S
S
D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D001560:Benzidines / Q000032:analysis; D015153:Blotting, Western; D002453:Cell Cycle / Q000187:drug effects*; D002454:Cell Differentiation / Q000187:drug effects; D003561:Cytarabine / Q000494:pharmacology* / Q000627:therapeutic use; D004247:DNA / Q000096:biosynthesis; D053938:DNA Fragmentation / Q000187:drug effects; D004912:Erythrocytes / Q000166:cytology* / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects; D018816:Genes, cdc / Q000235:genetics; D016758:Genes, jun; D016259:Genes, myc; D006801:Humans; D020014:K562 Cells; D010766:Phosphorylation; D016160:Retinoblastoma Protein / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
D001560:Benzidines; D016160:Retinoblastoma Protein; D003561:Cytarabine; C029876:benzidine; D004247:DNA