ADAM-9 is a member of the metalloproteinase protein family with a disintegrin domain that plays key roles in many physiological processes such as in fertilization, migration, and cell survival, and in diseases as well including cancer (1). ADAM9 is highly expressed in metastatic cancer tissues and was suggested to be involved in metastatic dissemination (2). We have previously demonstrated that the recombinant disintegrin domain of ADAM-9 (ADAM9D) inhibits the adhesion of both platelets and MDA-MB-231 breast tumor cells to type I collagen, a major component of the extracellular matrix (3). Here we provide additional evidence for a role of ADAM9D in metastasis. ADAM9 expression correlated with metastatic potential in a series of human breast tumour lines. Moreover, silencing of ADAM-9 inhibited MDA-MB-231 Matrigel invasion by approximately 72% compared to control cells without affecting the rate of cell proliferation. For trans-endothelial migration assays, MDA-MB-231 cells (7x104 cells/chamber) were placed in the upper chamber covered with a monolayer of HMEC (Human Dermal Microvascular Endothelial Cells) or HUVEC (Human Umbilical Vein Endothelial Cells) and incubated for 16 hours at 37oC and 5% CO2. The effect of siADAM9 and ADAM9D on the adhesion of tumor cells was also analyzed by flow adhesion assay. 2x106 MDA-MB-231 cells (siADAM9 or control) were stimulated in a dynamic flow (5 dynes - 5 minutes) through a monolayer of HMEC cells. Transient ADAM9 silencing reduced MDA-MB-231 cell transmigration through HUVEC or HMEC. In addition, ADAM9D (1000nM) inhibited tumor cells transmigration through endothelial cells. Taken together, these results suggest that ADAM9 is involved in the processes of adhesion and transmigration and that its disintegrin domain could be an important target for anti-metastatic therapy.
Financial Support: FAPESP, CNPq and CAPES (Brazil).