Abstract 5315: WAVE3 modulates the invasion-metastasis cascade by regulating invadopodia structures, MMP activity and ECM degradation

Abstract

Abstract Invadopodia are dynamic membrane structures enriched in actin that form on the ventral side of invasive cancer cells and are required for the degradation of the extracellular matrix (ECM), therefore, allowing the invasion of the tumor-surrounding tissue and subsequent colonization and metastasis. Invadopodia are the site of assembly of a multitude of proteins, including the actin regulators cortactin and members of WASP/WAVE proteins family. In our previously published studies we have identified WAVE3 as a key player in modulating the invasion-metastasis cascade in breast cancer (BC), where WAVE3 expression levels are significantly increased in metastatic BC cell lines and tumors. We have also shown that the metastasis-promoting activity of WAVE3 is achieved in part by affecting the activity of several matrix metalloproteinases (MMPs), including MMP1, MMP3 and MMP9. These MMPs, which are integral constituents of invadopodia, are required for the degradation of the ECM. More importantly, we have shown that phosphorylation of WAVE3 by Abl tyrosine kinase at specific tyrosine residues is required for the WAVE3-mediated modulation of BC metastasis. Here we present evidence that WAVE3 phosphorylation regulates the metastatic phenotype of BC by affecting the formation of invadopodia, MMPs activity and ECM degradation. First we show that loss of WAVE3 in the metastatic MDA-MB-231 BC cells results in a significant reduction in the number of invadopodia. Loss of WAVE3 expression also results in a significant decrease in MMP expression and activity in the zymography assay, loss of the ability of MDA-MB-231 cells to degrade gelatin in the ECM degradation assay, and consequently, a dramatic decrease in the invasive potential of these cells. Mechanistically, our data have now established a new link between WAVE3 and invadopodia, where WAVE3 phosphorylation downstream of Abl is critical for the formation of invadopodia structures as well as for MMP activity and for the degradation of the ECM. Loss of WAVE3 phosphorylation either by site directed mutagenesis or by pharmacological inhibition of Abl kinase activity leads to a significant decrease in invadopodia formation, MMP2 and MMP9 activity as well as ECM degradation, as a direct result of the inability of phospho-mutant WAVE3 to localize to invadopodia. In an independent study, we have found that WAVE3 is involved in a different molecular pathway, where WAVE3 phosphorylation is also required for the nuclear translocation of NFkB and the activation of MMP9, downstream of TNFα. The WAVE3-mediated NFkB nuclear translocation to activate MMP9 is facilitated through a WAVE3-Importin interaction, either directly or within a protein complex. Together, our data indentify two independent pathways whereby WAVE3 modulates the cancer invasion-metastasis cascade through its regulation of invadopodia structures and the NFkB-mediated activation of MMPs. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5315. doi:1538-7445.AM2012-5315