Abstract 780: In vitro screening of individual human neuroendocrine tumors for their angiogenic response to tyrosine kinase inhibitors
Authors: Milosavljevic Tanja , Chouest Elise J. , Anthony Catherine E. , Dirige Ariana , Wang Yi-Zarn , Boudreaux Philip J. , Ramcharan Thiagarajan , Woltering Eugene A. 
Published: July 2017

Background: Human neuroendocrine tumors (NETs) are highly vascular in nature and reliant on multiple receptor tyrosine kinases (TKs) for their neovascularization, growth, and, metastasis. These tumors most commonly originate in the small bowel (SB) and frequently metastasize to the lymph nodes and other organs. Current treatment of metastatic NETs involves a variety of approaches including antiangiogenesis therapies. In this study we tested effectiveness of six TK inhibitors (TKIs) [Dovitinib lactate, Regorafenib, Erlotinib, Imatinib, Vatalanib, and Sunitinib] on individual NETs angiogenic response in vitro.

Methods: Specimens were obtained from NET patients who underwent removal of their primary tumor (small bowel/pancreas/stomach), nodal, and organ (i.e. liver/ovary/omentum/mesentery) metastasis. Fresh tumors were minced, embedded in a fibrin-thrombin clot and supplemented with nutrient culture media per the in vitro human tumor angiogenesis model protocol. Neovessels were visually scored and evaluated for angiogenic parameters: percent initiation (%I), angiogenic growth (AI), and overall angiogenic response (OAR). All TKIs were prepared consistent with manufacturer’s instructions and their effective concentration was determined by dose response experiments. The selected TKI dose reflected the clinically achievable plasma level. A large group of NETs was tested for their antiangiogenic response to six TKIs [Dovitinib lactate (D): n=164, Regorafenib (R): n=163, Erlotinib (E): n=35, Imatinib (I): n=51, Vatalanib (V): n=163, Sutent (S): n=164)]. Paired samples t-test was used to compare TKI to control results for each angiogenic parameter, and independent samples t-test to compare TKI-response of primary and metastatic sites (MedCalc).

Results: Each selected dose [D: 82nM, R: 1100nM, E: 100µM, I: 2.5µM, V: 20µM, S: 188nM] achieved statistically significant inhibition of OAR (D:94.23%, R:35.58%, E:52.07%, I:59.77%, V:76.65%, S:64.79%) in all NETs (p&lt;0.0001). This is accomplished by the simultaneous statistically significant decrease of %I by at least 3.47% (p=0.0164) and AI by at least 34.03% (p&lt;0.0001). Comparison of OAR between the primary and metastatic tumor sites revealed no differences in their response to each tested TKI (p&gt;0.2119). In all NETs, TKIs inhibited both mechanisms of angiogenesis, but preferentially targeted growth (all TKIs: p&lt;0.0001) over %I (D, I, V, S: p&lt;0.0001; E: p=0.0072; R: p=0.0164).

Conclusions: In vitro screening of individual tumors revealed that TKIs effectively inhibited all parameters of angiogenesis in all NETs, primary and metastatic tumors. Selected TKIs preferentially inhibited angiogenic growth rather than initiation in all NETs. Our preclinical results show that Dovitinib inhibits angiogenesis most effectively in human NETs compared to other TKIs in vitro.

Citation Format: Tanja Milosavljevic, Elise J. Chouest, Catherine E. Anthony, Ariana Dirige, Yi-Zarn Wang, Philip J. Boudreaux, Thiagarajan Ramcharan, Eugene A. Woltering. In vitro screening of individual human neuroendocrine tumors for their angiogenic response to tyrosine kinase inhibitors [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 780. doi:10.1158/1538-7445.AM2017-780