Abstract 4995: Role of MICAL1 in NEDD9 invasive signaling

Abstract

Metastasis is the final step leading to patient death in most solid tumors, including head and neck squamous cell carcinoma (HNSCC). For metastasis to proceed, tumor cells must become mobile and invasive, losing their communal behavior. A goal of our work is to delineate the downstream effectors of growth factor signaling pathways that contribute to invasion. Using a phosphotyrosine proteomics screen we previously identified neural precursor cell expressed, developmentally down-regulated 9 (NEDD9; CasL) as a mediator of VEGF and IGF-1 signaling to invasion in HNSCC cells. NEDD9 tyrosine phosphorylation led to matrix metalloproteinase9 (MMP9) expression and secretion, invadopodia formation and enhanced invasion. To determine the molecular details of NEDD9 protein:protein interactions leading to invasion, we have generated a series of NEDD9 substrate domain tyrosine (Y to F, YXXP) and SH3 domain mutants. Mutation of all 13 YXXP motifs to FXXP blocked NEDD9 tyrosine phosphorylation, MMP9 expression and invadopodia formation. Of note, we found that NEDD9 co-immunoprecipitated with Molecule Interacting with CasL 1 (MICAL1). To further define this interaction and its downstream impact, stable NEDD9 or MICAL1 silenced HNSCC cell lines expressing select shRNAs were generated, with each exhibiting reduced migration and invasion. MICAL shRNA transfected cell lines also exhibited decreased MMP9 secretion, consistent with our findings that lack of MICAL1 decreases cell invasion and with findings of other labs that MICALs interact with Rab proteins altering intracellular trafficking. Further, we have verified that MICAL1 and NEDD9 form complexes in cells based on coimmunoprecipitation analyses. Better understanding of this pathway will undoubtedly lead to the identification of novel therapeutics for the prevention of invasion and metastasis. Supported by NIH R01CA134845 (SAR), P30 CA138313 and NIH/NCRR UL1 TR000062/TL1 TR000061 from the South Carolina Clinical & Translational Research Institute (COH). Citation Format: Casey O. Holmes, Amanda M. Brock, Philip T. Sobash, Jessica A. Tiedeken, Steven A. Rosenzweig. Role of MICAL1 in NEDD9 invasive signaling. [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 4995. doi:10.1158/1538-7445.AM2014-4995