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BackgroundAnti-VEGF therapy reduces tumor blood vessels, however, some vessels always remain. These VEGF insensitive vessels may help support continued tumor growth and metastases. Many in vitro assays examining multiple steps of the angiogenic process have been described, but the majority of these assays are sensitive to VEGF inhibition. There has been little focus on the development of high-throughput, in vitro assays to model the vessels that are insensitive to VEGF inhibition.MethodsHere, we describe a fixed end-point and kinetic, high-throughput stem cell co-culture model of cord formation.ResultsIn this system, cords develop within 24 hours, at which point they begin to lose sensitivity to VEGF inhibitors, bevacizumab, and ramucirumab. Consistent with the hypothesis that other angiogenic factors maintain VEGF-independent vessels, pharmacologic intervention with a broad spectrum anti-angiogenic antagonist (suramin), a vascular disrupting agent (combretastatin), or a combination of VEGF and Notch pathway inhibitors reduced the established networks. In addition, we used our in vitro approach to develop an in vivo co-implant vasculogenesis model that connects with the endogenous vasculature to form functional blood vessels. Similar to the in vitro system, over time these vessels become insensitive to VEGF inhibition.ConclusionTogether, these models may be used to identify novel drugs targeting tumor vessels that are not sensitive to VEGF inhibition.

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The roles of cholecystokinin 2 receptor (CCK2R) in numerous physiologic processes in the gastrointestinal tract and central nervous system are ‘well documented. There has been some evidence that CCK2R alterations play a role in cancers, but the functional significance of these alterations for tumorigenesis is unknown. We have identified six mutations in CCK2R among a panel of 140 colorectal cancers and 44 gastric cancers. We show that these mutations increase receptor activity, activate multiple downstream signaling pathways, increase cell migration, and promote angiogenesis. Our findings suggest that somatic mutations in CCK2R may promote tumorigenesis through deregulated receptor activity and highlight the importance of evaluating CCK2R inhibitors to block both the normal and mutant forms of the receptor.