Objective: To investigate the expression of long non-coding RNA CBR3-AS1 (CBR3-AS1) in breast cancer and its function.  
Methods: The expressions of CBR3-AS1 in 70 paired specimens of breast cancer tissue and adjacent tissue as well as in different breast cancer cell lines (MCF-7, MDA-MB-453 and SKBR3) and normal mammary epithelial cell line (HS578Bst) were detected by qT-PCR. The relations of CBR3-AS1 expression with the clinicopathologic variables and prognosis of the breast cancer patients were analyzed. The breast cancer SKBR3 cells were transfected with CBR3-AS1 interfering sequences (interference group), CBR3-AS1 mimics (overexpression group) and negative control sequences (negative control group) respectively, and then, the proliferative viability and apoptosis of cells of each group after transfection were determined by MTT assay and flow cytometry, respectively.
Results: The relative expression level of CBR3-AS1 was significantly increased in breast cancer tissue or each studied breast cancer cell line compared with tumor adjacent tissue or normal mammary epithelial cell line (all P<0.01). The CBR3-AS1 expression in breast cancer tissue was significantly associated with TNM stage (P=0.003), lymph node metastasis (P=0.047) and distant metastasis (P=0.024). The 3-year disease-free survival and overall survival rates in patients with high CBR3-AS1 expression were significantly lower than those in patients with the low CBR3-AS1 expression (53.3% vs. 70.7%, P=0.003 2; 62.8% vs. 78.4%, P=0.005 7). Compared with negative control group, the proliferative viability was significantly reduced and apoptosis rate was significantly increased in cells of interference group, while the proliferative viability was significantly increased and apoptosis rate was significantly reduced in cells of overexpression group (all P<0.01). 
Conclusion: The CBR3-AS1 expression is up-regulated in breast cancer and is closely related to the unfavorable clinicopathologic features and poor prognosis of breast cancer patients. The mechanism may probably be associated with its promoting proliferation and inhibiting apoptosis of breast cancer cells.