Abstract 1608: Angiopoietin 2 is elevated in patients with RCC, and Ang2 inhibition improves antiantiogenic activity of sunitinib in a mouse model of RCC.
Authors: Wang Xiaoen , Bullock Andrea , Zhang Liang , Yu Dongyin , Wei Lin , Song Jiaxi , Bhasin Manoj , Signoretti Sabina , Alsop David C. , Mier James W. , Atkins Michael B. , Coxon Angela , Oliner Jon , Bhatt Rupal S. 
Published: August 2014

Background: Several small molecules targeting angiogenic receptor tyrosine kinases (TKIs) are approved for treatment of advanced RCC. While many patients (pts) respond to TKIs, resistance develops in all. Ang2 is a secreted glycoprotein that is upregulated at sites of angiogenesis and has been implicated in cancer neovascularization. Ang2 is elevated in many cancer states, and higher levels are associated with poor prognosis. Recent studies have also suggested efficacy of combined Ang and VEGFR inhibition as therapy in RCC.

Mehtods: A panel of angiogenic genes was analyzed by RT-PCR in several tumor vs normal tissues. Plasma Ang2 levels in pts with RCC were measured in duplicate at baseline, on treatment with sunitinib (median 34.5 days after starting sunitinib), and at resistance to sunitinib. Finally, dual Ang1/2 (AMG 386) or Ang2 (L1-7) inhibition was also tested in a murine RCC xenograft model of resistance to VEGFR inhibition. Tumors were assessed for blood flow by arterial spin labeled (ASL) MRI.

Results: Among the genes studied, Ang2 levels were 6.7 fold higher in human tumors vs normal (nl) tissues, and 12.6 fold higher in RCC vs nl. RCC ranked highest for Ang2 expression across all the tumor types tested, with Ang2 levels in RCC being 2.8 fold higher than in all other tumor types. VEGF and KDR showed similar results, with both exhibiting higher levels in tumors vs nl tissues (7.5 fold for VEGF and 2 fold for KDR). VEGF was 25.5 fold higher in RCC vs nl, and KDR was 6 fold higher in RCC vs nl. VEGF and KDR were also higher in RCC than all other tumor types (7.0 fold for VEGF and 6.5 fold for KDR).

Plasma Ang2 was significantly higher in pts with metastatic RCC (n=50) compared to controls (n=26) and pts with stage I disease (n=39) (P&lt;0.001). Ang2 was also measured in pts at baseline, day 28 and at time of progression on sunitinib. Plasma Ang2 decreased at day 28 (n=39 pairs) and increased at the time of disease progression (n=28 pairs) (P&lt;0.001). In our mouse model of RCC, dual Ang1/2 (AMG 386) or Ang2 (L1-7) inhibition improved the activity of sunitinib (su) (time to progression on su, su+AMG 386, su+L1-7 = 25.6±12.4, 48.2±13.5, or 51.9±17.2 days, respectively (P&lt;0.05). Treatment with these agents exhibited a trend towards reduction in residual viable tissue after combination treatment and prevented the resumption of blood flow as measured with ASL MRI with sunitinib alone (tumor perfusion on day 50 post-treatment with su, su+AMG 386, su+L1-7 = 36.7±15.0, 18.4±11.1, or 16.0±7.3 ml/100g/min, respectively, P&lt;0.01).

Conclusion: Ang2 inhibition is elevated in pts with RCC, and Ang2 inhibition improves the activity of sunitinib in our mouse model of resistance. Plasma Ang2 levels increase in pts treated with sunitinib and may contribute to resistance to therapy. It is possible that the subset of pts with the highest Ang2 at resistance may be the optimal candidates for combination of these antiangiogenic agents.

Citation Format: Xiaoen Wang, Andrea Bullock, Liang Zhang, Dongyin Yu, Lin Wei, Jiaxi Song, Manoj Bhasin, Sabina Signoretti, David C. Alsop, James W. Mier, Michael B. Atkins, Angela Coxon, Jon Oliner, Rupal S. Bhatt. Angiopoietin 2 is elevated in patients with RCC, and Ang2 inhibition improves antiantiogenic activity of sunitinib in a mouse model of RCC. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1608. doi:10.1158/1538-7445.AM2013-1608