Authors

Long Sun, Biao Qian, Shenghong Shi, Wei Zhang, Jing Jiang, Xujun Li#

Departments

Department of Breast Surgery, Hwa Mei Hospital, University of Chinese Academy of  Sciences, Ningbo, PR China

Abstract

Objective: To discuss the influences of beclin 1 on the sensitivity of tamoxifen of oestrogen-receptor-positive breast cancer by regulating the HER2 expression level. 

Methods: Oestrogen-receptor-positive tissues were selected. MCF-7 cells were placed into culture medium containing 10% foetal calf serum and 5% carbon dioxide and cultured at 37 °C. Culture medium containing 1 uM tamoxifen was used to culture the cells for 5 months, then MECF-7R with secondary tamoxifen resistance was produced. Staining methods containing HE were used to observe the changes of MCF-7R and MCF-7 cell morphology. Western blots were used to observe the expressions of Beclin 1 and HER2 in MCF-7R and MCF-7 cells. siRNA interference fragments were used to transfect MCF-7R and MCF-7 cells. Expressions of MCF-7R and MCF-7 of Beclin 1 and HER2 in non-siRNA interference fragment (A group), siRNA transfection (B group), Beclin 1 siRNA 1 transfection (C group) and Beclin1 siRNA transfection (D group) groups were observed. Cell proliferation was detected using an MTT method, and cell clone formation ability was observed. Apoptosis of breast cancer cells was noted after down-regulation of Beclin 1 using flow cytometry. 

Results: MCF-7 cells: cells were arranged well, with even size and cluster growth; MCF-7R cells: cells were in a disordered arrangement with a larger volume. Compared with MCF-7 cells, Beclin 1 and HER 2 expression in MCF-7R cells were significantly improved. After Beclin 1 si RNA interference fragment transfection, Beclin 1 expressions of MCF-7R and MCF-7 cells in C and D groups were significantly decreased compared with those of A and B groups (P<0.05). After Beclin down-regulation, compared with A and B groups, HER2 expression of MCF-7R and MCF-7 cells in C and D groups were clearly decreased (P<0.05). After siRNA interference fragment transfection, compared with A and B groups, MCF-7R and MCF-7 cell proliferation ability in C and D groups notably decreased, and cell proliferation ability clearly decreased with the increase of tamoxifen concentration (P<0.05). Compared with the siRNA transfection group, MCF-7R and MCF-7 cell clone formation ability in BEclin 1 siRNA transfection group was notably decreased. MCF-7R and MCF-7 cell clone formation ability under 3uM tamoxifen were clearly decreased compared with those under 0uM tamoxifen (P<0.05). Compared with the siRNA transfection group, MCF-7R and MCF-7 cell apoptosis in the Beclin 1 siRNA transfection group were obviously aggravated. MCF-7R and MCF-7 cell apoptosis under 3uM tamoxifen were clearly enhanced compared with those under 0 uM (P<0.05). 

Conclusion: Beclin 1 and HER2 expressions were correlated in oestrogen-receptor-positive breast cancer patients. Beclin 1 and HER 2 expressions in MCF-7R cells were demonstrably higher than those of MCF-7 cells. In MCF-7R and MCF-7 cells, down-regulating Beclin 1 expression will increase the sensitivity of cells to tamoxifen, which may be achieved by down-regulating HER2 expression. 

Keywords

Beclin 1, oestrogen-receptor-positive, breast cancer, tamoxifen sensitivity, mechanism.

DOI:

10.19193/0393-6384_2020_3_324