Abstract 2810: Evaluating MMP contribution to pre-metastatic niche formation.

Abstract

Abstract Metastasis, the fatal progression of solid malignancies, consists of a complex and multistep process characterized by a series of ordered biological events. One step in this process occurs when stromal microenvironmental changes take place at secondary sites before the arrival of tumor cells. These modified tissue-specific sites are induced by signals from the primary tumor and further supported by recruitment of progenitor bone marrow derived cells and are commonly referred to as “pre-metastatic niches.” Matrix metalloproteinases (MMPs) are crucially involved in many pathological processes including tumor invasion and metastasis. Our goal is to determine the roles of MMPs in generation of a pre-metastatic niche in different target organs, specifically the lung and liver. Using an MMP proteolytic beacon capable of detecting MMP activity in situ, we observed increased signal in lungs of mice carrying pre-metastatic mammary tumors. In a LLC-implantation model, qPCR was used to profile MMP expression in pre-metastatic tissues versus controls and indicated that in the lung, MMP9 (gelatinase B) was increased. Further, we have developed staining and quantitation techniques to define pre-metastatic niches. These were also based on molecules identified by Kaplan et al such as VEGFR-1, VLA-4 and fibronectin. Immunofluorescent analysis of mouse lungs subcutaneously implanted with LLC cells demonstrated clusters of cells that positively co-stained for VEGFR-1, VLA-4 and Fibronectin. We also tested whether soluble factors from metastatic cell lines could induce changes in lungs of mice. Analysis of MMP-9 levels as well as localization of the known markers both failed to show any significant changes in the lung, leading us to believe that the presence of a primary tumor in vivo is required for pre-metastatic niche formation. We are now working with the well-characterized metastatic mammary tumor line 4T1 to test whether the changes we have seen with LLC cells are reproducible in a different cancer type and mouse strain. Additionally we are testing whether the absence of host MMP-9 affects the formation of a pre-metastatic niche in either model. The increased presence of MMP-9 and mentioned factors before tumor cell arrival could indicate potential roles and markers for metastatic spread, possibly leading to potential therapeutics for preventing metastasis and increasing overall cancer survival. Egeblad et al. Journal of Biochemistry and Molecular Biology, Vol. 36, No. 1, January 2002, pp. 128-137 Kaplan et el. Nature, Vol. 438, No. 7069, December 2005, pp 820-827 Citation Format: Elizabeth A. Dozier, J. Oliver McIntyre, Conor Lynch, Lynn Matrisian, Barbara Fingleton. Evaluating MMP contribution to pre-metastatic niche formation. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2810. doi:10.1158/1538-7445.AM2013-2810