Objective To study the effects of adramycin to disturb telomeric extention reaction mediated by telomerase of Tca8113 cells by inducing oligonucleotides that contain telomeric repeats to form guanine- quadruplex （G4） structures. Methods In the presence of adriamycin, d（TTAGGG）4, d（TTAGAG）4, d（TTAGGG）5 and d（TTAGGGT） were analyzed by electrophoretic mobility shift assay. The mobility of d（TTAGGG）3, d（TTAGGG）4 and d（TTAGGG）5 in native polyacrylamide electrophoresis were observed. Methylation protection experiments were performed to investigate the effects of adriamycin on methylation of guanine in d（TTAGGG）4 and d（TTAGAG）4. The traditional telomeric repeats amplification protocol（TRAP） and modified TRAP- G4 assays were, respectively, used to analyze the different characteristcs of adriamycin′s inhibiting telomeric extension mediated by telomerase of Tca8113 cells. Results At 5.00 μg/mL of adriamycin, conversion of some of linear d（TTAGGG）4 and d（TTAGGG）5 to the new, high-mobility bands formed by complex with special second structures were found in the mobility shift assay. Adriamycin at 1.25 μg/mL protected the G in d（TTAGGG）4 from methylating. Adriamycin at 2.50 μg/mL or 1.25 μg/mL partially inhibited the telomeric extension lengthened by telomerase of Tca8113 cells in TRAP assay, but completely did so in TRAP - G4 assay. Conclusion Adriamycin is able to disturb telomeric extention mediated by telomerase of Tca8113 cells by inducing oligonucleotides that contain telomeric repeats to form intra- molecular G4 structures.
