Abstract

 
 
 
 Purpose: To study the effect of CBX4/miR-137/Notch1 signaling axis on the migration and proliferative capacity of breast cancer.
 Methods: Breast cancer MCF7 cell lines were cultured in vitro and transfected with CBX4- overexpressed plasmid and interfering plasmid, which served as CBX4 over-expressing group and CBX4 interfering group, respectively. A control group (blank plasmid transfection) was set up. The MCF7 cells were transfected with miR-137 over-expressed plasmid, miR-137 interfering plasmid and Notch1 interfering plasmid, which served as miR-137 over-expressing, miR-137 interference and Notch1 interference groups, respectively. Cell proliferation and migration capacity were determined with methylthiazolyldiphenyl-tetrazolium (MTT) method and Transwell migration assay, respectively, while reverse transcription-polymerase chain reaction (RT-PCR) and immunoblotting were used to assay related gene expressions.
 Results: Cell migration in CBX4 over-expressing group was significantly raised (p < 0.05). The expression of miR-137 in CBX4 over-expressing group was markedly decreased (p < 0.05). Compared with the control group, mRNA and protein expressions of Notch1 (NICD), Hey2 and Jag1 in miR-137 over-expressing cells were increased in the miR-137 interfering group (p < 0.05).
 Conclusion: CBX4 level is increased in mammary cancer cells. Moreover, CBX4 enhances cell proliferation and migration through induction of Notch1 signaling route by inhibiting miR-137 expression. These findings provide a new strategy for clinical therapy of mammary cancer.
 
 
 
Highlights
Breast cancer is the most common cancerous disease in women
The results of MTT assay showed that cell proliferation activity of MCF7 cells in CBX4 overexpressing group were significantly increased, while the cell proliferation activity of MCF7 cells in CBX4 interference group were markedly reduced, relative to control (p < 0.05)
When Notch1 interfering plasmid was transfected into MCF7 cells, clonal formation experiment and Transwell migration experiment revealed that the population of cell clones and cell migration in the Notch1 interfering + CBX4 and miR-137 + CBX4 groups were markedly decreased
Summary
Breast cancer is the most common cancerous disease in women. In developing countries, breast cancer ranks second in the number of female deaths caused by cancer [1]. Polycomb gene protein family comprises transcription factors that participate in several biological events. Liposome 2000 reagent was used to transfect CBX4 over-expressed plasmid and interfering plasmid into breast cancer cell lines. These served as CBX4 over-expressing group and CBX4 interference group, respectively. Thereafter, the medium was discarded, and following PBS-rinsing (thrice), the cells were fixed in methanol for 20 min. They were incubated with 0.1 % crystal violet for 20 min, rinsed thrice with PBS and dried. The upper chamber was rinsed with PBS, fixed with methanol for 15 min, soaked in 0.1 % crystal violet solution for 10 min, and washed 3 times with PBS. Electrochemical luminescence reagent was used for color development and exposure, and the protein bands were scanned, developed and quantified
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