Preventing chemoresistance of human breast cancer cell line, MCF-7 with celecoxib

To investigate the preventive effect of celecoxib, a specific cyclooxygenase-2 (Cox-2) inhibitor, on the development of chemoresistance in breast cancer cell line, MCF-7, and explore the mechanism of the action.

Chemoresistance phenotype was established by treating MCF-7 cells with 0.05 μg/ml doxorubicin for 7 days, and then the effect of preventive chemoresistance was investigated by the combination of same dose of doxorubicin with 10 μM celecoxib. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide assay was used to assess cytostatic efficacy of doxorubicin and 50% inhibiting concentration (IC₅₀) of MCF-7 cells. RT-PCR was performed to examine mRNA expression of multidrug resistance gene 1 (MDR1) and its transcription factors c-Jun and NF-κB. Western blotting analysis was performed to detect the expression of protein. Flow cytometry (FCM) was applied to analyze the expression and function of P-glycoprotein (P-gp). Electrophoretic gel mobility shift assay (EMSA) was performed to determine the DNA-binding activity of nuclear transcription factors AP-1 and NF-κB.

Compared with sensitive MCF-7 cells, MDR1 and its transcription factors c-Jun and NF-κB were up-regulated at both mRNA level (P < 0.01) and protein level (P < 0.01) by treatment with 0.05 μg/ml doxorubicin for 7 days. After co-incubation with both the same dose of doxorubicin and 10 μM celecoxib for 7 days, both mRNA level and protein level of MDR1, c-Jun and NF-κB up-regulated by doxorubicin were partly reversed (P < 0.01); DNA-binding activity of nuclear transcription factors AP-1 and NF-κB were inhibited; and the function of P-gp was decreased (P < 0.01). When MCF-7 cells were treated with increasing doses of doxorubicin in the presence of 10 μM celecoxib, IC50 value of doxorubicin and doxorubicin plus 10 μM celecoxib was 0.67 ± 0.03 and 0.38 ± 0.04 μg/ml, respectively (P < 0.01).

Celecoxib effectively prevents the development of chemoresistance in breast cancer cell line MCF-7 induced by doxorubicin, which was partly involved in inhibiting the expression and DNA-binding activity of nuclear transcription factors AP-1 and NF-κB and downstream expression and function of P-gp. Furthermore, cytostatic efficacy of celecoxib and doxorubicin on MCF-7 cell was synergistic.