Objective    To investigate the effects of quercetin on the growth of lung cancer cell line A549 and the expression of  hTERT gene.      Methods    The number of viable cells was ascertained by trypan blue dye exclusion test. Morphological changes of apoptotic cells were observed by electronic microscopy and DNA ladder assay. The telomerase activity was analyzed by PCR-TRAP assay and hTERT mRNA expression was detected by quantitative RT-PCR.     Results    Quercetin had a significant inhibition on the proliferation of  A549 cells  in a dose-dependent manner. The IC

50

was 22.5  μmol/L after exposure to quercetin for 48 h.  The resu

lts from electron microscopy and DNA ladder showed that apoptosis occurred in the A549 cells of treatment groups. The results of quantitative RT-PCR and PCR-TRAP revealed that the expression of hTERT mRNA was significantly inhibited by quercetin and telomerase activity was decreased.     Conclusion    Quercetin inhibits the growth of lung cancer cell line A549 in a dose-dependent manner

and induce their apoptosis. The down-regulated expression of hTERT

suppression of telomerase activity and destruction of telomere stability may all contribute to the mechanism of apoptosis induction.