Nck promotes breast carcinoma progression and metastasis by directing the polarized interaction of carcinoma cells with collagen fibrils, decreasing actin turnover, and enhancing the localization and activity of MMP14 at the cell surface through modulation of the spatiotemporal activation of Cdc42 and RhoA.

Glioblastoma (GBM) is a primary brain cancer that is resistant to all treatment modalities. This resistance is due, in large part, to invasive cancer cells that disperse from the main tumor site, escape surgical resection, and contribute to recurrent secondary lesions. The adhesion and signaling mechanisms that drive GBM cell invasion remain enigmatic, and as a result there are no effective anti-invasive clinical therapies. Here we have characterized a novel adhesion and signaling pathway comprised of the integrin αvβ8 and its intracellular binding partner, Spinophilin (Spn), which regulates GBM cell invasion in the brain microenvironment. We show for the first time that Spn binds directly to the cytoplasmic domain of β8 integrin in GBM cells. Genetically targeting Spn leads to enhanced invasive cell growth in pre-clinical models of GBM. Spn regulates GBM cell invasion by modulating the formation and dissolution of invadopodia. Spn-regulated invadopodia dynamics are dependent, in part, on proper spatiotemporal activation of the Rac1 GTPase. GBM cells that lack Spn showed diminished Rac1 activities, increased numbers of invadopodia and enhanced extracellular matrix (ECM) degradation. Collectively, these data identify Spn as a critical adhesion and signaling protein that is essential for modulating GBM cell invasion in the brain microenvironment.

<p>Supplementary Table 1. Peptides identified by LC-MS/MS and SEQUEST searching for integrin αv, integrin β8, and Spinophilin. Supplemental Figure 1. Analysis of β8 integrin-Spn binding and Spn protein localization in vitro and in cultured cells. Supplemental Figure 2. Spn protein is expressed in recurrent human GBM samples. Supplemental Figure 3. Spn mRNA is differentially expressed in GBM regions, but expression levels do not correlate with patient survival. Supplemental Figure 4. Experimental strategy to generate mosaic mouse models of the brain cancer astrocytoma. Supplemental Figure 5. Genetically targeting Spn in human GBM cells using RNAi leads to enhanced tumor cell invasion. Supplemental Figure 6. Microscopic analysis of Spn-dependent invasive growth in LN229 tumors. Supplemental Figure 7. Immunohistochemical analysis of xenograft tumors derived from LN229 cells expressing control or Spn shRNAs. Supplemental Figure 8. Analysis of invadopodia formation in GBM cells. Supplemental Videos 1 and 2. Imaging Rac1 GTPase activities in live cells by FRET.</p>

<p>Raich-Rac1 Imaging, video 2</p>

<p>Raich-Rac1 Imaging, video 1</p>