Abstract 4979: A6B1 integrin internalization is increased by loss of A3B1 expression and promotes migration of human prostate cancer cells
Authors: Das Lipsa , Anderson Todd A. , Gard Jaime M.c. , Sroka Isis C. , Strautman Stephanie R. , Nagle Raymond B. , Knudsen Beatrice S. , Cress Anne 
Published: May 2015

Abstract
Laminin binding integrins, A3B1 and A6B1 drive in part, cancer cell migration and metastasis. Cell migration requires dynamic internalization and recycling of surface integrins. However, whether laminin binding integrin internalization is coordinately or independently controlled is not known. In this study, we quantitated the internalization of integrin A3 and A6 and whether crosstalk influences their respective internalization and subsequent cancer cell migration.
We quantitated the internalization of A6 and A3 integrins, using fluorophore conjugated antibody based internalization assays and flow cytometry. In the prostate cancer cell line DU145, we observed constitutive internalization of integrin A6 with a surface half-life of approximately 30 minutes as compared to &gt;70 minutes for integrin A3, 45 minutes for unrelated integrin Av or 10 minutes for the unrelated transferrin receptor. Silencing A3 integrin expression resulted in a 10 percent increase in the total amount of internalized A6 integrin, with a decreased surface half-life of 20 minutes. The internalized A6 integrin showed intracellular punctate staining colocalized with the early endosome marker EEA1 and Rab4 containing vesicles. Increased integrin A6 internalization led to 40% increase in migration which was dependent on A6B1 integrin. Silencing integrin A6 expression, however, did not affect the internalization of A3 integrin indicating a unidirectional regulation of integrin internalization. The changes in the integrin internalization could be clearly ascribed to alpha subunits, as the obtained half-life of A6 and A3 integrins were independent of antibody used or integrin engagement by ligand mimetic peptides. Taken together, these data indicate that A6B1 and A3B1 integrins have different internalization kinetics and the presence of integrin A3 decreased integrin A6 internalization and ensuing cell migration. These data are consistent with previous observations in normal systems suggesting that A3B1 provides a provisional matrix during early stages of wound healing, requiring subsequent stable adhesion complexes and integrin A6 function. In cancer, the loss of A3 integrin and the increased internalization of A6 integrin may account for the “wounds that won't heal” phenotype and provide a strategy for biological intervention to block tumor progression.
(Supported in part by NIH Grants CA23074 and CA159406 and the TACMASS core service of the Arizona Cancer Center)
Citation Format: Lipsa Das, Todd A. Anderson, Jaime M.c. Gard, Isis C. Sroka, Stephanie R. Strautman, Raymond B. Nagle, Beatrice S. Knudsen, Anne Cress. A6B1 integrin internalization is increased by loss of A3B1 expression and promotes migration of human prostate cancer cells. [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 4979. doi:10.1158/1538-7445.AM2014-4979