Objective: To investigate the effect of methylation status of
breast cancer metastasis suppressor gene 1 (BRMS1) on the expression of
breast cancer and the biological behavior of
cancer cells in
triple-negative breast cancer (TNBC). Methods: The expression of BRMS1 in TNBC tissues and corresponding non-malignant tissues and its relationship with clinicopathological parameters were detected by immunohistochemistry. The
mRNA and
protein expression of BRMS1 in normal breast epithelial cells and TNBC cells were detected by reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting. The methylation specific polymerase chain reaction (MSP) was used to detect the methylation status of BRMS1 in each cell. These cells were treated with demethylated preparations (5-Aza-dC) to re-activate BRMS1 expression. Using
tumor cell invasion assay to detect influence of BRMS1 demethylation on the invasion capacity of
cancer cells. The data were statistically analyzed. Results: The positive expression rate of BRMS1
protein in TNBC tissues was significantly lower than that in corresponding non-malignant tissues (χ(2)= 6.635, P<0.05). The
mRNA expression level of BRMS1 in patients with
lymph node metastasis was significantly lower than those with no
lymph node metastasis (P=0.018). The down-regulation of BRMS1 expression was related to the methylation of
DNA promoter, which was statistically significant (χ(2)=14.68, P<0.05). The
mRNA and
protein expression of BRMS1 was also correlated with
tumor size and TNM staging (P=0.000-0.003). After using 5-Aza-dC, the number of cells with invasive capacity was significantly lower than those of the control group (t=3.262-10.72, P<0.05). Conclusions: The decrease of BRMS1 expression in TNBC cells is related to the methylation of
DNA. Demethylation can inhibit the invasion of
breast cancer cells.