Abstract 207: CMG2 regulates angiogenesis through interactions with extracellular matrix
Authors: Garrard Samuel R. , Gold Mark , Tsang Tsz Ming , Lee Sai Lun , Fogg David , Dannenberg Rachael , Rogers Michael S. , Christensen Kenneth A. 
Published: August 2019

Abstract
Angiogenesis is a critical process in cancer progression, facilitating initial tumor growth and allowing for metastasis into other tissues. Though several therapeutic agents are now available that reduce angiogenesis in vivo, all exhibit undesirable side effects, and none target more than one signaling pathway. This minimizes the potential to block additional signaling pathways and hence therapeutic applications, especially in cancers, which often utilize multiple signaling pathways. Capillary morphogenesis gene protein 2 (CMG2) is an integrin-like cellular receptor whose gene is highly upregulated during angiogenesis. Previously, we have demonstrated that CMG2 function is critical to neovascularization in vivo, and that CMG2 regulates angiogenesis through multiple signaling pathways, marking CMG2 as an effective target in development of multi-pathway antiangiogenic therapeutic agents.
CMG2 is also known to function as an anthrax toxin receptor, the mutation target in the rare genetic disease hyaline fibromatosis syndrome (HFS), and an interactor with extracellular matrix. Regarding HFS, it was recently shown that CMG2 knockouts lead to accumulation of extracellular matrix, especially collagen VI (Col-VI). To investigate a link between HFS and angiogenesis, we probed CMG2 affinity for several intact matrix proteins by ELISA, including laminin-111, fibronectin, and collagens I, IV, and VI. We discovered that CMG2 bound all these matrix proteins with similar affinity (Kd = 500-1000 nM). We then constructed a peptide array, containing the entire sequences of the collagen IV α1/α2 chains; fibronectin; and laminin-111 to identify CMG2-binding regions, using a 10-amino acid sliding window. We thereby identified a small peptide, designated S16, which binds CMG2 with high affinity and which inhibts angiogenic processes ex vivo. Since the integrin family of proteins regulate cell signaling and angiogenesis and are homologs of CMG2, we suspected that CMG2 may also function to regulate angiogenesis through matrix interactions. Consequently, we ran a higher resolution peptide array (2-amino acid sliding window) to identify specific matrix epitopes. In this expanded peptide array, we covered the sequences of the collagen IV α1 and α2 chains, collagen IV α3- α6 non-collagenous domains, collagen VI α1 and α2 chains, and portions of the collagen VI α3 chain and fibronectin. We noted several hits in each matrix protein on the array, including several in Col-VI, whose sequences map to specific vWFA domains in that matrix protein. We have now confirmed that CMG2 binds these collagen VI-derived peptides and their respective domains with high affinity. This has significant implications for the role of these domains in angiogenic phenotypes such as cell migration and adhesion. We anticipate that the interactions between these peptides and CMG2 can be exploited to develop multi-pathway inhibitors of angiogenesis.
Citation Format: Samuel R. Garrard, Mark Gold, Tsz Ming Tsang, Sai Lun Lee, David Fogg, Rachael Dannenberg, Michael S. Rogers, Kenneth A. Christensen. CMG2 regulates angiogenesis through interactions with extracellular matrix [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 207.