Abstract 3152: Integrin α6β1 dependent collective cell migration in prostate cancer metastasis

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Investigating the metastasis tactics of cancer cells show some cancers migrate using epithelial to mesenchymal transition (EMT) while others, such as prostate cancer, use collective migration similar to embryonic tubulogenesis. In human tissue specimens, collective migration originates from pre-malignant prostate intraepithelial neoplasia (PIN), occurs in invasive adenocarcinoma and persists in prostate cancer metastatic bone lesions. Successful collective migration requires cell attachment to the surrounding extracellular matrix (ECM), via adhesion receptors, specifically integrins. In prostate cancer, the laminin binding integrins α6β1 and α3β1 are expressed throughout disease progression including metastases. The laminin receptor α6β1 has been shown to be a determinant of prostate tumor cell aggressiveness. Integrin α6β1 undergoes a post-translational modification mediated by the serine protease, urokinase plasminogen activator (uPA) and its receptor uPAR, resulting in a variant form called α6pβ1. In this study, we optimized the growth and retrieval of tumor cells from 3-dimensional matrigel cultures, to determine the role of integrin α6β1, α6pβ1 and α3β1 in DU145 prostate tumor cell collective migration. The DU145 prostate tumor cells embedded in growth factor reduced matrigel, grew robust networks within 24 hours and contained extensive branching structures. The network formation was shown to be dependent on integrin α6β1 expression as determined by specific knockdown of α6β1 over a 24 hour period using 25nM siRNA targeting. Interestingly, the knockdown of α3β1 integrin had no observable effect on the networks. The networks produced by the DU145 cells contained pericellular proteolysis activity along the branches of collective cells as well as at the leading tips of the branches. Laminin 332, its receptor integrin α6β1, and uPAR co-localized on the membranes between cells traveling collectively. Induced production of integrin α6pβ1 increased branching network formation, while blockage of integrin α6pβ1 production impaired collective migration via reduced network formation. Taken together, these observations suggest that collective cell migration through tubulogenesis requires cell adhesion to laminin via integrin α6β1 and production of the α6pβ1 structural variant facilitates this process. Ongoing work is using the model to identify candidate molecular effectors of tubulogenesis as well as pharmacological approaches to block the process and prevent tumor progression. Supported in part by NIH grants CA 23074 and CA 159406. Citation Format: Cynthia S. Rubenstein, Jaime Gard, Raymond B. Nagle, Terry H. Landowski, Anne E. Cress. Integrin α6β1 dependent collective cell migration in prostate cancer metastasis. [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 3152. doi:10.1158/1538-7445.AM2014-3152