Ets2 binding site single nucleotide polymorphism at the hTERT gene promoter - effect on telomerase expression and telomere length maintenance in non-small cell lung cancer

The aim of this study was to elucidate the occurrence of DNA sequence changes in the promoter region of hTERT gene, and its effect on telomerase expression and telomere length maintenance in non-small cell lung cancer (NSCLC). Between January 2002 and December 2003, 66 NSCLC patients were studied. The expression of hTERT, telomerase activity (TA), and c-Myc were examined, and the terminal restriction fragment length (TRFL) was measured. A t/n-TRFLR was obtained by dividing the TRFL of the tumour tissue by TRFL of the paired normal tissue. PCR products were sequenced and compared with known hTERT gene promoter sequence for a length of 716 bp upstream of the transcription starting code. The changes of any known sequence and/or c-Myc expression with their impact on telomerase activity and TRFL maintenance were measured. Positive hTERT, TA and c-Myc expression was observed in 43 (65.2%), 39 (59.1%) and 59 (89.4%) of the tumour tissue samples, respectively. Except for one patient who had C/C (in normal tissue) homozygotes to T/C (in tumour tissue) heterozygotes point mutation, a novel single nucleotide polymorphism (SNP) −245kb upstream (Ets2 binding site) of the hTERT gene was observed in all normal and tumour tissues, including C/C in 9, T/C in 35, and T/T in 22 of the tumour tissues. The TA of C/C homozygotes was lower than that of T/T homozygotes (P = 0.0331), while the t/n-TRFLR of C/C homozygotes was higher than that of T/T homozygotes (P = 0.0621). The latter was even more obvious when c-Myc were positive (P = 0.0185). Our data shows that T/T homozygotes have a lower t/n-TRFLR, but a stronger TA expression, suggesting that the studied Ets2 binding site is a positive regulator of hTERT gene. SNP may interfere with Ets2 binding and lower TA expression in T/C heterozygotes and C/C homozygotes.