Telomerase, hTERT and splice variants in Barrett's oesophagus and oesophageal adenocarcinoma.
OBJECTIVE
The enzyme telomerase is re-activated in most cancers but its mechanism of regulation in oesophageal carcinogenesis is unclear. The aim of this study was to determine the roles of human telomerase reverse transcriptase (hTERT) mRNA expression and hTERT mRNA splicing in the regulation of telomerase enzyme activity in Barrett's oesophagus and oesophageal adenocarcinoma.


METHODS
Paired samples from oesophageal adenocarcinoma (n=21) and adjacent macroscopically normal mucosa, and paired samples from Barrett's oesophagus (n=16) and adjacent cardia mucosa were obtained. Telomerase activity was measured by the telomeric repeat amplification protocol assay. hTERT mRNA was quantified using real-time reverse transcriptase polymerase chain reaction (RT-PCR). Splice variants within the hTERT reverse transcriptase domain (alpha, beta, alpha beta) were detected by RT-PCR.


RESULTS
In oesophageal adenocarcinoma, compared to adjacent mucosa, median telomerase activity increased significantly (from 5 to 229 total product generated (tpg), P=0.0002), but median hTERT mRNA levels were not significantly different. Similarly, median telomerase activity was significantly higher in oesophageal adenocarcinoma compared to Barrett's oesophagus (229 vs 20 tpg, P=0.001), but hTERT mRNA levels were not significantly different. There was no significant difference in telomerase activity and hTERT mRNA levels between Barrett's oesophagus and adjacent cardia. The frequency of detection of all variants increased from cardia to Barrett's oesophagus to oesophageal adenocarcinoma (P<0.05).


CONCLUSIONS
A major increase in telomerase activity occurs after the Barrett's oesophagus stage in oesophageal carcinogenesis. Levels of hTERT mRNA and hTERT mRNA splicing patterns did not correlate with telomerase activity and do not appear to regulate enzyme activity. In this cancer, an important clinical diagnostic role for the transcripts of the telomerase gene is improbable.
Barclay
Jill Y
JY
University Hospitals, Coventry and Warwickshire NHS Trust, Coventry, UK.
Morris
Alan
A
Nwokolo
Chuka U
CU
D000230:Adenocarcinoma / Q000201:enzymology* / Q000235:genetics; D017398:Alternative Splicing; D001471:Barrett Esophagus / Q000201:enzymology* / Q000235:genetics; D004268:DNA-Binding Proteins; D018450:Disease Progression; D004789:Enzyme Activation / Q000235:genetics; D004938:Esophageal Neoplasms / Q000201:enzymology* / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D011230:Precancerous Conditions / Q000201:enzymology / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D012334:RNA, Neoplasm / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D019098:Telomerase / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*
D004268:DNA-Binding Proteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D019098:Telomerase