Abstract 2388: Interaction between connective tissue growth factor and a disintegrin and metalloproteinase with thrombospondin type I repeats 7 during cancer development

Abstract

Abstract Introduction: Connective tissue growth factor (CTGF) is a secreted pro-angiogenic protein within the CCN (Cyr61/CTGF/Nov) family and modulates multiple angiogenic pathways through its broad binding ability to cysteine knot motifs presents in key angiogenic factors including vascular endothelial growth factor (VEGF)-A. Overexpression of CTGF has been found in many cancers such as Lewis lung carcinoma (LLC), cholangiocarcinoma (CC), and hepatocellular carcinoma (HCC). In an effort to understand the molecular action of CTGF, we identified a disintegrin and metalloproteinase with thrombospondin type I repeat 7 (ADAMTS7) as a CTGF binding protein in yeast two-hybrid analysis. This enzyme belongs to the ADAMTS family capable of cleaving extracellular matrix (ECM) components and extracellular regulatory molecules. Here, we show that ADAMTS7 binds to and degrades CTGF during cancer development. Methods: Adamts7 knockout mice were used to investigate the importance of ADAMTS7 in CTGF interaction and cleavage during LLC development. Adamts7+/+ and Adamts7−/− mice were subcutaneously implanted with LLC cells. Tumor growth was quantitatively measured within two weeks after implantation. Tumor angiogenesis was assessed utilizing a microvascular density assay. In addition, Adamts7 expression was tracked via X-gal staining of LLC tumors grown in Adamts7−/− mice that contained a LacZ trap-in cassette in the targeted Adamts7 allele. VEGF-A, CTGF, and ADAMTS7 were determined at both the mRNA and protein levels. Results: Adamts7 induction as indicated by the β-galactosidase activity in X-gal staining was found in intra-tumor stromal cells of LLC tumors grown in Adamts7−/− mice. The association of CTGF and ADAMTS7 proteins in protein lysates of LLC tumors grown in Adamts7+/+ mice was confirmed in immunoprecipitation assays. Higher levels of VEGF-A, CTGF and ADAMTS7 mRNAs were found in LLC tumors from Adamts7−/− animals as compared to Adamts7+/+ controls. Slower rate of CTGF turnover, faster growth of LLC tumors, and higher microvascular density were also found in Adamts7−/− animals than controls. Conclusion: These observations confirmed the binding and processing of CTGF by ADAMTS7 during LLC growth. The host-derived ADAMTS7 appears to regulate CTGF turnover and provides a protective effect towards aberrant LLC tumorigenesis and angiogenesis. Citation Format: Liya Pi, Bryon E. Petersen. Interaction between connective tissue growth factor and a disintegrin and metalloproteinase with thrombospondin type I repeats 7 during cancer development. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2388. doi:10.1158/1538-7445.AM2015-2388