To investigate the effect of specificity protein 1 (SP1) on proliferation, apoptosis and β-catenin signaling pathway in triple negative breast cancer HCC1806 celld.

Human normal breast epithelial cell line MCF10A and triple negative breast cancer cell line HCC1806 were purchased from Shanghai Institute of Cell Science, Chinese Academy of Sciences. The expression of SP1 was detected by real-time quantitative reverse transeriptase-polymerase chain reaction (RT-qPCR) and Western blotting in MCF10A and HCC1806. HCC1806 cells were transfected with SP1 small interfering RNA (siRNA) and scrambled control siRNA by Lipofectamine 2000. The effect of SP1 on cell proliferation and apoptosis was detected by methyl thiazolyl tetrazolium (MTT) assay and flow cytometry. The expression levels of β-catenin signaling pathway and downstream related proteins [β-catenin, glycogen synthase kinase 3β (Gsk3β), Cyclin D1, p53 and cysteinyl aspartate-specific protease (Caspase)-3] in the HCC1806 cells were detected by Western blotting. SPSS 19.0 statistical software was used for analysis.

The expression of SP1 in HCC1806 cells (3.09±0.26) was significantly higher than that in MCF10A (1.06±0.09, t=0.008, P<0.01). The relative expression of SP1 mRNA of HCC1806 cells transfected with SP1 siRNA in the experimental group was (0.37±0.10), SP1 expression of HCC1806 cells transfected with SP1 siRNA significantly decreased (t=0.002, P<0.05), by (66.90±3.79)% compared with the control group. After transfection with SP1 siRNA, the proliferation rate of the experimental group was (40.82±2.67)%, significantly lower than that of the control group [(72.72±5.90)%,t=0.000, P<0.05], and the apoptosis rate of the experimental group was (42.14±4.54)%, significantly higher than that of the control group [(22.25±3.07)%,t=0.002, P<0.05], and increased (19.89±5.52)%. The protein expression levels of β-catenin and Cyclin D1 in the experimental group were (0.21±0.08) and (0.70±0.04), respectively; the protein expression levels of β-catenin and Cyclin D1 in the control group were (0.61±0.09) and (0.92±0.03), respectively. The protein expression levels of β-catenin and Cyclin D1 in the experimental group were significantly decreased (t=0.002, 0.001, P<0.05). In the experimental group, the protein expression levels of β-catenin and Cyclin D1 were decreased to (65.80±7.76)% and (23.88±4.99)%. The protein expressions of Gsk3, p53 and Caspase-3 in the experimental group were (0.73±0.05), (0.74±0.05) and (0.62±0.11), respectively. The expression levels of Gsk3, p53 and Caspase-3 in the control group were (0.48±0.03), (0.25±0.03) and (0.36±0.05), respectively. The expression levels of Gsk3, p53 and Caspase-3 in the experimental group were significantly increased (t=0.001, 0.001, 0.010, P<0.05). The expression levels of Gsk3, p53 and Caspase-3 in the experimental group were increased to (52.79±11.29)%, (202.60±39.41)% and (77.12±35.20)%, respectively.

SP1 expression is highly up-regulated in the triple negative breast cancer HCC1806 cells, and downregulation of SP1 expression can effectively inhibit the growth of HCC1806 cells and promote apoptosis through the β-catenin signaling pathway.

Breast cancer; Specificity protein 1; Proliferation; Apoptosis; β-catenin signaling pathway