Abstract 2322: Knockdown of the beta 1 integrin subunit inhibits tumor growth and metastasis in an orthotopic mouse model of pancreatic cancer

Integrins are a family of heterodimeric transmembrane receptor proteins that mediate cell interactions with the extracellular matrix (ECM), components of which are highly up-regulated in pancreatic cancer and thought to promote malignancy in vivo. Using lentiviral-based shRNA methodology targeting the beta 1, alpha 2, and alpha 3 integrin subunits, human FG-RFP pancreatic cancer cells were infected, and stable puromycin-resistant clones were selected. Clones (n=5 for each group) were subsequently screened for integrin subunit expression at the mRNA and protein levels by quantitative PCR and immunoprecipitation, respectively. Selected clones were further characterized for function in cell adhesion, proliferation, and migration assays on types I and IV collagen, fibronectin, laminin, and vitronectin. The clones resulting in the greatest reduction in expression and functional activity for each targeted integrin-subunit were then injected orthotopically into the pancreas of nude mice and analyzed for growth and metastasis over a six-week period. The mRNA levels for the beta 1, alpha 2, and alpha 3 integrin subunit knockdown clones selected for use in vivo were reduced by 99.9, 98.4, and 95%, and protein expression levels were reduced by 89.1, 91.6, and 92.6%, respectively, compared to the non-target control clone. Significant inhibition of adhesion on types I and IV collagen, fibronectin, and laminin was observed for the beta 1 subunit knockdown clone, and on types I and IV collagen, laminin, and vitronectin for the alpha 2 subunit knockdown clone, relative to the alpha 3 subunit and non-target control clones. Significant decreases in cell proliferation were observed on types I and IV collagen as well as vitronectin for the alpha 2 subunit knockdown clone and on all tested ECM proteins for the beta 1 subunit knockdown clone, relative to the alpha 3 subunit and non-target control clones. Significant decreases in cell migration were noted on types I and IV collagen for the alpha 2 subunit knockdown clone and on types I and IV collagen and fibronectin for the beta 1 subunit knockdown clone, compared to the alpha 3 subunit and non-target control clones. In a fluorescent orthotopic mouse model of pancreatic cancer, knockdown of the beta 1 integrin subunit significantly inhibited tumor growth, with no ascites formation and no metastasis observed (n=9), compared to the alpha 2 and alpha 3 integrin subunit knockdowns, and non-target control clones. Collectively, these data demonstrate a crucial role for the beta 1 integrin subunit in the progression of pancreatic cancer and suggest the beta 1 integrin subunit as a potential therapeutic target for this recalcitrant disease. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2322.