Abstract 1988: MenaINV interaction with α5β1 promotes tumor cell invasion in response to gradients of growth factors and fibronectin

Abstract

Abstract To metastasize and disseminate, carcinoma cells must invade the surrounding extracellular matrix (ECM) and migrate to reach blood or lymphatic vessels. Collagen (CN) and fibronectin (FN), two components of the ECM surrounding tumors, are highly expressed in metastatic tumors and their patterns of expression can correlate with metastatic outcome in patient samples. Mena, an actin regulatory protein, is upregulated in breast cancer and is alternatively spliced to produce protein isoforms with distinct functions during tumor progression. The invasion-specific MenaINV isoform increases metastasis by potentiating tumor cell motility and invasion responses to various growth factors. All Mena isoforms bind directly to the α5 subunit of the α5β1 integrin, an FN receptor. We hypothesized that the interaction between MenaINV and α5β1 plays an important role in integrating signals from the ECM as well as growth factors to drive invasion. MDA-MB-231 breast cancer cells expressing MenaINV showed increased adhesion to FN alone as well as mixture of FN and CN, compared to control cells. MenaINV cells also had an increased number of α5-positive adhesions as well as increased signalling at focal adhesions as measured by phospho-Paxilin, compared to control. In 3D invasion assays, addition of FN to a CN gel drove invasion of MenaINV-expressing cells even in the absence of any growth factor ligand, an effect driven by its interaction with α5 and dependent on signalling via EGFR and Met. Furthermore, addition of FN caused an even greater potentiation of EGF-induced invasion by MenaINV, an effect that was dependent upon its interaction with α5. Next, we examined how MenaINV affects tumor cell responses to a gradient of FN within a 3D collagen gel. Control cells failed to respond to an FN gradient, while cells expressing MenaINV migrated preferentially towards FN and significantly reorganized both the collagen and FN surrounding them. Deletion of the α5 binding site or treatment with an α5 function blocking antibody ablated the effects MenaINV on movement towards a FN gradient as well ECM reorganization. Overall, these results suggest that some aspects of the pro-metastatic effects of MenaINV involve its ability to bind α5 and regulate bidirectional signaling with FN and growth factors in the tumor microenvironment. Citation Format: Madeleine J. Oudin, Liliane C. Broye, Alisha Lussiez, Sreeja B. Asokan, Miles A. Miller, Douglas A. Lauffenburger, James E. Bear, Frank B. Gertler. MenaINV interaction with α5β1 promotes tumor cell invasion in response to gradients of growth factors and fibronectin. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1988. doi:10.1158/1538-7445.AM2014-1988