Inhibition of human telomerase reverse transcriptase by nonsteroidal antiinflammatory drugs in colon carcinoma.

BACKGROUND: Telomerase activation, which is observed in most human cancers, plays an important role in carcinogenesis. Human telomerase reverse transcriptase (hTERT) is a subunit of telomerase that is essential for telomerase activity. The aim of the study was to investigate whether nonsteroidal antiinflammatory drugs (NSAIDs) inhibit telomerase activity and hTERT.

METHODS: Four colon carcinoma cell lines, HT-29, COLO205, CRL-2134, and SW1116, were used in the experiments. Polymerase chain reaction-based telomeric repeat amplification (TRAP) enzyme-linked immunosorbent assay (ELISA) was used to measure telomerase activity in the cells after treatment with aspirin, indomethacin, or SC-236 (a specific cyclooxygenase-2 [COX-2] inhibitor). Expression of hTERT mRNA and protein was detected by reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting, respectively. The dual luciferase reporter assay was performed to identify the potential cis-response elements to NSAIDs in the promoter region of hTERT.

RESULTS: Aspirin, indomethacin, and SC-236 inhibited telomerase activity in HT-29, COLO205, and CRL-2134 cell lines, but not in the SW1116 cell line. NSAIDs inhibited hTERT mRNA and protein expression through suppression of hTERT transcriptional activity. The hTERT promoter fragment -145 to -330 basepairs (bp) upstream of the ATG starting site was sufficient to respond to the NSAID-induced inhibitory effect and the inhibition was COX-2-independent.

CONCLUSION: NSAIDs inhibit telomerase activity at hTERT transcriptional, mRNA, and protein levels in colon carcinoma cells. The hTERT promoter fragment -145 to -330 bp may be the cis-response element to NSAIDs.