exploring profilin as a target for suppressing the migration of breast cancer cells

4315 Objective: Profilin (an actin-binding protein that also interacts with several proline-rich proteins involved in the signaling pathways leading to cytoskeletal organization) has been implied as a tumor suppressor protein based on it’s reduced expression in invasive breast cancer cells and ability to reduce tumorigenicity when overexpressed in these cells. However, a direct functional relevance of reduced expression of profilin in the pathogenesis of breast cancer has not been established. The aims of the present study were to explore whether 1) loss of profilin confers neoplastic characteristics to mammary epithelial cells, and 2) perturbations of profilin alter the migration of breast cancer cells. Methods: Suppression of profilin expression was achieved via RNAi-mediated gene silencing. Other perturbations included overexpression of either fully functional or dominant negative mutants of profilin that are selectively impaired in binding to different ligands. Results: Suppression of profilin conferred several characteristics that are hallmarks for neoplastic characteristics to human mammary epithelial cells (HMEC) including increased cell proliferation and chemotactic migration, decreased cell-cell and cell-matrix adhesions. Silencing profilin expression also increased the migration of MDA-MB-231 breast cancer cells. Overexpression of profilin stimulated assembly of actin stress fibers and focal adhesions, with concomitant inhibition in cell migration. expression of dominant negative mutants of profilin that are defective in binding to either actin or it’s proline-rich ligands also suppressed the migration of MDA-MB-231 cells, but to a lesser extent compared to the action of overexpressed profilin, thus suggesting that a fully functional profilin is required for it’s maximal inhibitory effect on breast cancer cell migration. Conclusion: Our results for the first time indicate that reduced profilin expression may be functionally linked to the pathogenesis of breast cancer and that perturbation of cellular profilin could be an effective strategy to limit migration of breast cancer cells.