RESUMO
PURPOSE: The telomere binding proteins play an important role in telomere function, which contribute greatly to the radio resistant in human cancers. This research is designed to investigate the relationship among the telomere length, telomerase activity and changes of telomere binding protein PTOP and TRF1 in radio resistant breast cancer cell lines. METHODS: Irradiate MDA-MB-435 s breast cancer cell with total dose of 60 Gy delivered in 2 Gy/fraction and 6 Gy/fraction respectively, then measuring their telomere length by Southern blot analysis,telomerase activity by Telomerase PCR Elisa and detecting the expression of PTOP and TRF1 in both gene and protein levels. To further investigate the function of PTOP, using lentivirus technic to silence the PTOP gene and the detected the new silenced cells by southern blot and telomerase activity. RESULTS: 2 radio resistant breast cancer cell lines were successfully established. The MDA-MB-435 s R60/6 was (approximate 8.1-8.6 kbp) about 2-2.4 folds to the patent cell (3.6-4.2 kbp), the MDA-MB-435 s R60/2 cell (approximate 5.3-6.3 kbp) was about 1.3-1.75 fold to the parent cell line. The telomerase activity was more enhanced in radio resistant cell lines than the parent cell. The expression of PTOP and TRF1 were significant increased in radio resistant cell lines than the patent cell in both gene and protein level. Otherwise, after using lentivirus technic to silence the PTOP gene, we found the radio resistant cell lines were significant decrease their radio resistances and telomerase activities. CONCLUSION: The telomere binding protein PTOP and TRF1 were increased expressed in radio resistant breast cancer cell, PTOP was observed instinct positive correlated with telomere lengthen and telomerase activity enhancement.