A Preliminary Study Of Role Of PRMT2 In Tamoxifen Resistant Breast Cancer Cells

Objective: To investigate the effect of PRMT2 on TAM resistance in breast cancer cells and to explore the underlying mechanisms, in order to provide new insights into therapy of drug resistant breast cancer.Methods: MDA-MB-231 cells and MCF-7 cells cultured in vitro were utilized in the present study to investigate the role of PRMT2 in TAM induced cell apoptosis. Our experiments included three parts:(1) Flow Cytometry was carried out to analyze the effect of TAM on breast cancer cell apoptosis at the cell level;(2) To reveal the subcellular localization of PRMT2 and ER-ɑ36 through confocal microscopy;(3) Western Blotting analysis was used to detect the effect of TAM on PRMT2、ER-ɑ36 and P-Akt expression in breast cancer cells at the protein level.Results: 1. MCF-7 cell lines were treated with different concentrations of TAM for 4 hours, flow cytometry results showed that compared with the control group, 2μM、5μM、7.5μM TAM concentration group had an increasing apoptosis rate, and TAM could enhance the apoptosis rate in a dose-dependent manner, with statistical significance(P<0.001). However, MDA-MB-231 cells had a relatively lower apoptosis rate when treated with the same concentration of TAM, indicating that MDA-MB-231 cells were resistant to the TAM.2. Immunofluorescence combined with CLSM observation revealed that in MDA-MB-231 breast cancer cells, PRMT2 and ER-ɑ36 were localized to the cell nucleus and cytoplasm, and PRMT2 was found to co-localize with the ER-ɑ36 protein in this cell line.3. Western blot analysis revealed that in the MCF-7 cell line which was more sensitive to TAM, after treated cells with TAM at the indicated doses(0μM、2μM、5μM、7.5μM) for 4 hours, the protein levels of p-Akt were downregulated by TAM in a dose-dependent manner, and the protein levels of ER-ɑ36 and PRMT2 in this cell line had no obvious change. However, in the MDA-MB-231 cell line which was resistant to TAM, the protein levels of PRMT2 were downregulated by TAM, and it was associated with significant upregulation of ER-ɑ36 and p-Akt, all of them changed in a dose-dependent manner. Further time effect study showed that in both breast cancer cell lines, these protein levels changed corresponded to their dose effect group respectively.Conclusion: 1. PRMT2 was co-localized with ER-ɑ36 in MDA-MB-231 cells.2. In MDA-MB-231 cells, PRMT2 may involved in TAM resistance, the mechanism related to that TAM could down regulate the expression of PRMT2, increase the expression of ER-ɑ36 and the phosphorylation level of Akt.