Abstract 4301: Endothelial angiopoietin-2 expression correlates with tumor angiogenesis and response to sunitinib in metastatic renal cell carcinoma

Abstract

Abstract Background: Angiopoietin-2 (Ang2) is an endothelial cell derived growth factor, which promotes tumor angiogenesis, tumor growth and metastasis. Ang2 is a promising target for anti-angiogenic therapies, but its potential as a biomarker for anti-angiogenic therapies remains unknown. The purpose of this study was to evaluate expression of the Ang2-Tie2 signalling pathway components in metastatic RCC (mRCC) patients treated with sunitinib, a modern multitarget TKI. Materials and methods: We evaluated Ang2, CD31 and Ki67 expression in tumors of 136 patients with metastatic RCC (mRCC) treated with first-line sunitinib from formalin-fixed paraffin-embedded tumor samples using immunohistochemistry. Results: Ang2 was exclusively expressed in the endothelial cells of tumor blood vessels. Using a cutoff of ≥50 Ang2+ vessels/microscopic field, 38% of the samples had high Ang2 expression. High Ang2 expression correlated with high CD31+ vessel density (p = 0.002). 91% of patients with high Ang2 expression had partial response (PR) or stable disease (SD) as best response to sunitinib as compared with 76% of those with low Ang2 expression (P = 0.033). High CD31+ vessel density correlated with a high clinical benefit rate (P = 0.015), and with low levels of Ki-67+ tumor cells (P = 0.018). Combined high expression of both Ang2 and CD31 predicted even better clinical benefit rate with 100% of the patients with high Ang2 and CD31 expression (n = 25) achieving PR/SD as compared with 77% among the rest of the patients (n = 101; P = 0.007). Only one patient (8%, n = 12) with papillary RCC, but 49 (41%) patients with clear cell RCC had high Ang2 expression (P = 0.03). Conclusions: In this first study to investigate Ang2 expression and outcome in mRCC patients treated with sunitinib, high Ang2 expression in the tumor vasculature was predictive for sunitinib efficacy. Citation Format: Anita Lampinen, Juhana Rautiola, Tuomas Mirtti, Ari Ristimäki, Heikki Joensuu, Petri Bono, Pipsa Saharinen. Endothelial angiopoietin-2 expression correlates with tumor angiogenesis and response to sunitinib in metastatic renal cell carcinoma. [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 4301. doi:10.1158/1538-7445.AM2015-4301