Abstract 1898: TIMP-2 function is regulated by the composition of the cellular microenvironment

Abstract The activity of mammalian matrix metalloproteinases (MMPs) is regulated by a family of four endogenous inhibitors known as the tissue inhibitor(s) of metalloproteinases (TIMPs). Since their original discovery and characterization several additional biological roles have been ascribed to TIMP family members, such as regulation of receptor tyrosine kinase-dependent cell growth and migration. TIMP-2 is abundantly expressed in normal tissues with low or absent MMP expression. In addition to this unique expression pattern TIMP-2 demonstrates broad spectrum inhibition of MMPs in vitro. Recent studies in our lab have shown that TIMP-2 is a promising candidate for biological cancer therapy. However, the role of TIMP-2 in cancer progression has been subject to debate with conflicting reports correlating enhanced TIMP-2 expression levels with both good and poor clinical outcomes. TIMP-2 exhibits multiple interactions with components of the extracellular matrix (ECM). Our working hypothesis is that TIMP-2 acts as a homeostatic mediator via modulation of ECM and cellular activities. Analysis of expression levels in tumor samples shows that TIMP-2 displays a strong positive correlation with a number of genes involved in regulation of the ECM. Using sample datasets from The Cancer Genome Atlas, we have identified a multi-gene expression pattern suggesting that the MMP-independent activities of TIMP-2 are sequestered in the tumor microenvironment. Using fluorescent labeled TIMP-2, we have conducted live cell imaging to visualize TIMP-2 localization in vitro. Our data reveals that TIMP-2 is highly dynamic both within the extracellular microenvironment and intracellular compartments. In addition, TIMP-2 displays a diverse pattern of localization within homogeneous cell populations and between cells of epithelial or mesenchymal lineages. Other in vitro observations highlight an inconsistent cellular response following TIMP-2 treatment. We speculated that these variations are a result of irregularities in ECM deposition by target cells. To obviate these inconsistencies, we have 1) generated TIMP-2 knockout cell lines; 2) cultured these cells on purified ECM in the presence or absence of exogenous TIMP-2 and/or mitogenic factors; 3) analyzed cell signaling response under these well-defined culture conditions. Our results show that TIMP-2 can differentially modulate intracellular signaling in a manner that is dependent on specific ECM components and the additional presence or absence of a mitogenic stimulus. Current work focuses on details of extracellular TIMP-2 molecular interactions and cellular uptake/signaling. Through further understanding of the extracellular molecular interactions of TIMP-2, and the factors that regulate its cellular functions, researchers will be able to more effectively target the aberrant extracellular environment that is associated with many human diseases. Citation Format: David Peeney. TIMP-2 function is regulated by the composition of the cellular microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1898.