Activation of kinin B1 receptor increases the release of metalloproteases-2 and -9 from both estrogen-sensitive and -insensitive breast cancer cells

The kinin B1 receptor (B1R) agonist Lys-des[Arg9]-bradykinin (LDBK) increases proliferation of estrogen-sensitive breast cancer cells by a process involving activation of the epidermal growth factor receptor (EGFR) and downstream signaling via the ERK1/2 mitogen-activated protein kinase pathway. Here, we investigated whether B1R stimulation induced release of the extracellular matrix metalloproteases MMP-2 and MMP-9 via ERK-dependent pathway in both estrogen-sensitive MCF-7 and -insensitive MDA-MB-231 breast cancer cells. Cells were stimulated with 1–100 nM of the B1R agonist for variable time-points. Western blotting and gelatin zymography were used to evaluate the presence of MMP-2 and MMP-9 in the extracellular medium. Stimulation of B1R with as little as 1 nM LDBK induced the accumulation of these metalloproteases in the medium within 5–30 min of stimulation. In parallel, immunocytochemistry revealed that metalloprotease levels in the breast cancer cells declined after stimulation. This effect was blocked either by pre-treating the cells with a B1R antagonist or by transfecting with B1R-specific siRNA. Activation of the ERK1/2 pathway and EGFR transactivation was required for release of metalloproteases because both the MEK1 inhibitor, PD98059, and AG1478, an inhibitor of the EGFR-tyrosine kinase activity, blocked this event. The importance of EGFR-dependent signaling was additionally confirmed since transfection of cells with the dominant negative EGFR mutant HERCD533 blocked the release of metalloproteases. Thus, activation of B1R is likely to enhance breast cancer cells invasiveness by releasing enzymes that degrade the extracellular matrix and thereby favor metastasis.