Abstract: AIM: To study transfected shRNA of c-myc as therapeutic agents into target cell Colo320 which expressed more tolomerase activity to investigate the effect of inhibition on telomerase activity and te-lomere lengths and tumor cell growth. METHODS: A plasmid-based polymerase III promoter system was used to deliver and express short interfering RNA (siRNA) targeting c-myc in Colo320 cells.The c-myc and hu-man telomerase reverse transeriptase (hTERT) mRNA level was monitored by fluorescence real time reverse transcription-polymerase chain reaction, the protein level of c-myc, hTERT were examined by western blot analysis. Meanwhile, telomere lengths and telomerase activity were measured by Southern analysis of telomere restriction fragment (TRF) length and PCR-ELISE. We also assessed the effects of c-myc silencing on tu-mor growth by DNA synthesis (³H-thymidine).RESULTS: The data showed that expression of c-myc and hTERT decreased in shRNA-transfected cells, down-regμlation of c-myc and hTERT inhibited cell growth, reduced cell telomere lengths and telomerase activity . CONCLUSION: shRNA of c-myc had the ability to inhibit telomerase activity and telomere lengths and cell growth and was dose dependent .

Key words: c-myc, small hairpin RNA, prolifera-tion, human telomerase reverse transeriptase