Abstract 2341: Functional analysis of paxillin mutations identified in lung cancer and malignant mesothelioma: Implications for cell migration/motility

Abstract

Abstract Paxillin is a 68 kDa focal adhesion protein that provides multiple docking sites at the plasma membrane for an array of signaling molecules and helps form a structural link between the extracellular matrix and the actin cytoskeleton. It is essential in actin filament assembly and focal adhesion formation. Focal adhesion complexes are the drivers of cell spreading and migration, adhesion to the extracellular matrix and matrix remodeling by fibrillar adhesions in which paxillin plays a major role. It has been shown that the modulation of tyrosine phosphorylation of paxillin regulates both the assembly and turnover of adhesion sites and phosphorylated paxillin enhances lamellipodial protrusions whereas non-phosphorylated paxillin is essential for fibrillar adhesion formation. We have previously reported that in lung cancer, paxillin was over expressed, amplified and mutated in a significant number of patient samples and the protein upregulated in higher stages of lung cancer compared with lower stages (Jagadeeswaran et al, 2008). We recently showed paxillin gene to be amplified in some pre-neoplastic lung lesions. Among the mutations we described, A127T enhanced cell proliferation, focal adhesion formation and colocalization with Bcl-2 in lung cancer cells. We have now analyzed 50 epithelioid, 16 sarcomatoid, and one mixed malignant pleural mesothelioma tissue, and compared to 40 normal adjacent lung parenchyma (pneumocytes and endothelial cells) by immunohistochemistry. Automated cellular imaging was used to calculate average staining intensity as an integrated optical density (IOD). Whereas normal lung had IODs of 45 for paxillin, epithelioid MPM had IODs of 268 and sarcomatoid 331. This demonstrates that paxillin is highly upregulated in both epithelioid as well as sarcomatoid. To further study the effects of activating mutations of paxillin, we cloned the most commonly occurring paxillin mutations in a GFP tagged vector and transiently transfect HEK-293 cells. Utilizing live-cell imaging to systematically study the effects of wild-type paxillin versus mutants, we created a mathematical model that recapitulates the salient features of the measured dynamics, and conclude that compared to wild-type, some mutant clones confer a) enhanced focal adhesion formation, b) increased filopodia and lamellipodia formation c) increased mobility and d) increased cell displacement in transiently transfected HEK-293 cells. We believe that paxillin is an important molecule in thoracic cancer including lung and malignant mesothelioma, and its therapeutic potential needs to be explored further. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2341. doi:10.1158/1538-7445.AM2011-2341