Effect of the selective aromatase inhibitor letrozole on the interaction between ERs and the hTERT-ERE and on telomerase activity. (a) LNCaP cells were cultured for 16 hours in the absence (lanes 2 and 3) or the presence of E2 (10–7 M, lanes 4 and 5) or T (10–7 M) (lanes 6–9) with (lanes 3, 5, and 9) or without the nonsteroidal aromatase inhibitor letrozole (1 μM) added 1 hour before hormone addition. Nuclear extracts (5 μg) were then prepared and incubated with a 32P-labeled oligonucleotide encompassing the proximal hTERT-ERE. Reaction in the presence of anti-AR (αAR) or anti–ER-β (αERβ) Ab’s are shown in lanes 7 and 8, respectively. Lane 1 corresponds to probe incubated without nuclear extracts. Migration of a slower migrating complex is indicated (arrow). (b) Extracts (0.1 μg) from LNCaP cells treated for 4 hours with R1881 (10–8 M) or T (10–7 M) with or without the nonsteroidal aromatase inhibitor letrozole (1 μM) added 1 hour before ligand addition were assayed for telomerase activity by TRAP.