Abstract 1825: Angiopoietin-Tie-2 functional axis in colorectal cancer liver metastasis (CRCLM) provides a new marker for stratification and evaluation of tumor progression

Abstract

Abstract Colorectal cancer (CRC) is the third leading cause of cancer in Canadians, with liver metastases being the major cause of death from this disease. Tumors induce angiogenesis, a phenomenon known as the ‘angiogenic switch’, which is an essential step in tumor progression whereby the balance of pro- and anti-angiogenic factors are important for active angiogenesis. Clinical efficacy of targeted VEGF (anti-angiogenic) treatment has been validated as a cancer therapy. Our group, together with others, has identified unique histological growth patterns HGPs (desmoplastic, replacement and pushing) within liver metastases that have different responses to anti-angiogenic therapy. The patients with Desmoplastic HGP (DHGP) that received anti-angiogenic plus chemotherapy prior to resection had a significantly better pathologic response and survival than patients with Replacement HGP (RHGP). The aim of this study was to explore the role of Ang-1, Ang-2, Tie-2 and VEGF in the development and progression of CRCLM tumors with distinct HGPs. Here, human CRCLM tumor samples were analyzed by quantitative real-time PCR (Q-PCR) and immunohistochemistry (IHC) staining. The Q-PCR results demonstrated that the expression of Ang-2 was lower in RHGP tumor samples compared with DHGP tumor samples. This data was validated by IHC, were IHC scoring results showed that the ratio of Ang-2: Ang-1 expression in DHGP tumors was higher compared to RHGP tumors. VEGF and Tie2 proteins were expressed in both tumor patterns. Thus vascular quiescence maintained by constitutive Ang-1/Tie-2 signaling, found in RHGP tumors, prevails over destabilization and pro-inflammatory Ang-2/Tie-2 signaling, which is higher in the DHGP tumor samples. Since vascular remodelling is driven by Ang-2/Tie-2 in DHGP, which is dependent on VEGF we would expect anti-angiogenic therapy to be effective on DHGP. Furthermore, the RHGP had low levels of Ang-2 and high levels of Ang-1, together with the presence of Tie-2, and then one would predict that VEGF is not required for the growth of these tumors and thus would not respond to anti-angiogenic therapy, as has been shown in our patients’ cohort. Taken together, these data suggest that the Angiopoietin/Tie-2 functional axis is an important player in CRCLM tumor progression and can be a potential target for CRCLM cancer therapy with stratification of patients by HGPs. Citation Format: Nisreen S. Ibrahim. Angiopoietin-Tie-2 functional axis in colorectal cancer liver metastasis (CRCLM) provides a new marker for stratification and evaluation of tumor progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1825. doi:10.1158/1538-7445.AM2017-1825