Abstract B57: Quantifying the contribution of matrix metalloproteinases to the development of the pre-metastatic niche in the lung and liver microenvironments

Abstract

Abstract The leading cause of cancer mortality is metastasis of a primary tumor to distant organs. It is thought that stromal micro-environmental changes occur at these secondary sites before the arrival of tumor cells, which facilitate future colonization and outgrowth. This occurrence is commonly termed as the formation of the “pre-metastatic niche.” Specific factors altered at pre-metastatic niches have already been described in literature (Nature. 2005 Dec 8;438(7069):820-7). These include VEGFR-1, VLA-4 and Fibronectin. Matrix Metalloproteinases (MMPs), known for their involvement in tumor invasion and metastasis, have also been implicated in niche formation. Our goals are to (1) determine the roles of MMPs in generation of the pre-metastatic niche and (2) develop a method of quantification for these niches in the lung utilizing a malignant breast cancer type. In a distant murine LLC-implantation model, we developed immunofluorescent (IF) staining techniques to define pre-metastatic niches within the lung based on the molecules identified by Kaplan et al. Within this same model, qRT-PCR indicated a substantial increase in lung MMP9 (Gelatinase B) gene expression. This led us to reproduce the pre-metastatic niche within a breast cancer model using a time-coursed malignant murine 4T1-GFP implantation model within Balb/c mammary glands. Visualization was again achieved by IF staining of known factors obtained from Kaplan et al. We utilized these models and the clusters formed to create an algorithm for quantifying the pre-metastatic niche. To confirm this algorithm is specific for premetastatic niches in metastatic tumor models, we also implanted 4T1-GFP cells into MMP9-/- Balb/c mice. These mice result in unorganized protein expression and lack of cluster formation. In addition we utilized a non-metastatic mammary tumor model, 67NR also implanted in Balb/c mice to serve as a negative control for our algorithm. Thus, to confirm the pre-metastatic niche is specific to metastatic tumor models. Eventually, pre-metastatic MMP activity may indicate potential roles and markers for metastatic spread. Further, this algorithm will provide a new quantitative standard for the field. Thus, this algorithm has translational potential as a test for specific drug efficacy. Citation Format: Miranda A. Hallett, E. Ashley Dozier, Joseph T. Roland, Barbara Fingleton. Quantifying the contribution of matrix metalloproteinases to the development of the pre-metastatic niche in the lung and liver microenvironments. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr B57. doi:10.1158/1538-7445.CHTME14-B57