Abstract:

OBJECTIVE: To establish a mitoxantrone-resistant MCF-7 breast cancer cell line，and to explore the relationship between breast cancer cells developing drug resistance and their genomic methylation levels. METHODS：Using cells infected with 0，0.005，0.010 and 0.020 μmol/L mitoxantrone，different levels of drug resistance of MCF-7/Mit cell line was established. Flow cytometer was used to detect the accumulation of mitoxantrone in MCF-7 cells to confirm drug resistant cell lines. Then，we used capillary electrophoresis to evaluate genomic DNA methylation levels of wide type and cells with different degrees of resistance. RESULTS：Compared with the control group，with increasing mitoxantrone concentration，drug accumulation gradually decreased in MCF-7 cells. In the wild-type control group，0.005，0.010 and 0.020 μmol/L -treated groups the drug D(755) values were 16.1±0.04， 14.3± 0.12，13.3±0.07 and 9.7±0.08，respectively. The 0.02 μmol/L exposure group was significantly reduced compared with the control group，indicating that drug resistance was significantly increased (P<0.05). In the wild-type control group，0.005，0.010 and 0.020 μmol/L -treated groups，the DNA methylation levels were 42.25%± 0.64%，37.97%± 1.18%，34.27%±0.14% and 31.16%±0.80%， respectively. Compared with the control group， genomic DNA methylation levels in each group of treated cells gradually decreased (P<0.05)，with significant differences between each two groups (P<0.05). CONCLUSION：Mit drug-resistant MCF-7 cell line was successfully set up. The separation condition of capillary electrophoresis when measuring genomic DNA methylation levels was determined.

Key words: capillary electrophoresis, DNA methylation, MCF-7 cell, flow cytometer