Human lung microvascular cells cocultured with human diploid fibroblasts form extensive networks of tubules in response to VEGF that can be visualized by immunostaining for CD31, an endothelial cell marker. In the presence of cabozantinib (XL184), a small-molecule kinase inhibitor with potent activity toward MET and VEGF receptor 2, it was found that tubule formation was inhibited in the absence of cytotoxicity. Similarly, cabozantinib inhibited tubule formation in response to conditioned media derived from tumor cell cultures, suggesting that secreted tumor cell-derived proangiogenic growth factors are unable to circumvent inhibition of tubule formation by cabozantinib. For details, see article by Yakes and colleagues on page 2298.