Matrix metalloproteinase-7 (MMP-7) is a small secreted proteolytic enzyme with broad substrate specificity. Its expression is associated with tumor invasion, metastasis, and survival in a variety of cancers including breast cancer. Using bioinformatics analysis, a conserved LEF-1 binding site became obvious that is mapped at the promoter region of the genomic MMP-7 locus. Consequently, electrophoretic mobility shift assay demonstrated in vitro binding of LEF-1 to the predicted MMP-7 promoter binding site. Here, we demonstrate that lymphoid enhancer binding factor-1 (LEF-1) is associated with regulation of the proliferation-associated cyclin D1 and a gene encoding MMP-7 in breast cancer cells. Thus, a decrease of LEF-1 expression using LEF-1 siRNA resulted in down-regulation of cyclin D and MMP-7 expression, respectively. Moreover, cell cycle analysis of LEF-1 siRNA-transfected human breast cancer cells revealed a significant arrest in G2/M phase. Taken together, our results indicate a pivotal role of LEF-1 in the regulation of proliferation and MMP-7 transcription in breast cancer cells.