[Azidothymidine inhibition of telomerase activity and proliferation of TJ905 human glioblastoma cells].
OBJECTIVE
To investigate the pharmacological effects and underlying mechanism of azidothymidine (AZT) on human glioblastoma cells in vitro.


METHODS
The telomerase activity of human glioblastoma TJ905 cells was determined by TRAP assay after 24 hrs' incubation with 50, 100, 200 micromol/L AZT and control vehicle solution. Colony formation efficiencies of the cells were recorded. Cells of the 1st, 3rd and 6th generations were harvested, followed by evaluations of cyclin A protein expression by Western blot, cell cycle distribution by flow cytometry, apoptotic level by single cell gel electrophoresis and proliferation index by Ki-67 immunocytochemical staining.


RESULTS
AZT inhibited telomerase activity of TJ905 cells. Cyclin A expression levels in the cells treated with 50 and 100 micromol/L AZT were significantly lower than controls (P < 0.01), and down-regulation of the expression was in a dose- and time-dependent manner. Compared with controls, G(0)/G(1) phase cells were obviously decreased (P < 0.05 approximately 0.01) and S phase cells significantly increased (P < 0.05 approximately 0.01) after treatment with 50, 100 and 200 micromol/L AZT. The cell numbers of G(0)/G(1) and S phases at the 1st generation of above three treated groups changed in a dose-dependent manner, whereas S phase cells increases in all AZT treatment groups and G(0)/G(1) phase cell decrease in group treated with 50 micromol/L AZT were also in a time-dependent manner. Both the apoptotic cells of the 1st and 6th generations of all AZT treatment groups were significantly more than controls (P < 0.05 approximately 0.01), their numbers of the 6th generations of the three groups increased with AZT concentration (P < 0.05 approximately 0.01), and all of them were more than the 1st and 3rd generations of the same dosage group (P < 0.05 approximately 0.01). Colony formation efficiencies and Ki-67 labeling indexes of the three AZT treatment groups were distinctly lower than controls (P < 0.01), and they were also decreased with the elevation of AZT concentration and/or the elongation of the incubating time. The difference of any above parameter had no significance among the 1st, 3rd and 6th generations of control group (P > 0.05).


CONCLUSIONS
AZT blocks S/G(2) conversion of TJ905 cells by inhibition of telomerase activity and cyclin A expression, leading to an enhancement of apoptosis and suppression of cell proliferation.
Liu
Jing
J
Department of Neuropathology, Neurological Institute of Tianjin Medical University General Hospital, Tianjin, China.
Wang
Qian
Q
Yu
Shi-zhu
SZ
Zhao
Wen-juan
WJ
Sun
Cui-yun
CY
An
Tong-ling
TL
Wang
Li-li
LL
Chen
Xiu-ju
XJ
D017209:Apoptosis / Q000187:drug effects; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D019925:Cyclin A / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D015972:Gene Expression Regulation, Neoplastic; D005909:Glioblastoma / Q000378:metabolism / Q000473:pathology; D006801:Humans; D019394:Ki-67 Antigen / Q000378:metabolism; D018894:Reverse Transcriptase Inhibitors / Q000008:administration & dosage / Q000494:pharmacology; D019098:Telomerase / Q000378:metabolism*; D015215:Zidovudine / Q000008:administration & dosage / Q000494:pharmacology*
D019925:Cyclin A; D019394:Ki-67 Antigen; D018894:Reverse Transcriptase Inhibitors; D015215:Zidovudine; D019098:Telomerase