siRNA-mediated silencing of integrin β3 expression inhibits the metastatic potential of B16 melanoma cells.

Integrins comprise a large family of αβ heterodimeric cell-surface receptors that mediate diverse processes involved in cell-cell and cell-matrix interactions such as cellular adhesion and migration, cell survival and differentiation. It is now well documented that integrins play a crucial role in cancer metastasis and angiogenesis. The β3 integrins appear to have an important stimulatory role in tumour progression and metastasis and, thus, have been often proposed as potential targets for cancer diagnosis and therapy. In this study, we evaluated the in vitro and in vivo properties of B16 mouse melanoma cells with low expression of integrin β3. Proliferation rate, adhesive properties and the ability to migrate and metastasize were studied. Over 90% inhibition of integrin β3 expression was achieved as a result of the transfection with siRNA. No changes in the proliferation rate were observed in siRNA-transfected B16 cells; however, they showed impaired ability to bind to fibronectin. Moreover, inhibition of integrin β3 expression caused almost complete impairment of the ability of B16 cells to migrate through matrigel and metastasize. The mean number of lung metastatic colonies in mice inoculated intravenously with B16 expressing low levels of integrin β3 was decreased to 14 colonies compared to 101 in the control group. These results provide evidence for a direct role of integrin β3 in the adhesion, migration and metastasis processes of mouse melanoma cells and point to the potential therapeutic advantages of siRNAs.