RESUMO
BACKGROUND: Chronic inflammation is considered to be a risk factor for carcinogenesis, tumor development and metastasis by providing tumor-related factors. OBJECTIVES: We aimed to evaluate the effect of cytokine interleukin-1ß (IL-1ß) as a key mediator of inflammation on multidrug resistance associated protein 2 (MRP2) expression and tamoxifen toxicity in estrogen receptor positive (ER+) MCF-7 breast cancer cells. METHODS: The effects of IL-1ß on tamoxifen toxicity following 20-day treatment of MCF-7 cells with IL-1ß and/or 17ß-estradiol (E2) were measured by MTT assay. Furthermore, the effects of IL-1ß and/or E2 on the mRNA expression and protein levels of MRP2 and NF-κB (p65) in breast cancer cells were evaluated by QRT-PCR and Western blot analysis, respectively. RESULTS: Treatment of breast cancer cells with IL-1ß+ E2 decreased the sensitivity to 4-OH tamoxifen compared to both E2-treated and untreated cells. The mRNA expression levels of MRP2 and NF-κB (p65) were significantly increased following treatment with IL-1ß+ E2, compared to control. In addition, breast cancer cells treatment with IL-1ß+ E2 increased protein expression of MRP2 and it had no significant effect on NF-κB/p65 protein expression in these cells. CONCLUSION: Increased expression of mRNA and protein level of MRP2 following 20-day treatment of MCF-7 cells with IL-1ß + E2 might be a possible elucidation for the increased tamoxifen resistance which was observed in these cells. More researches are essential to clarify the molecular mechanisms of inflammation on drug-resistance in the tumor environment in order to reducing or eliminating chemotherapy resistance and developing more effective treatment strategies.
