In the version of this Letter initially published, there was an error in Fig. 2b. Two image panels in the top row for CD31 were inadvertent duplicates of Figure 4 of Kamat, A.A. et al. Cancer Res. https://doi.org/10.1158/0008-5472.CAN-06-3282 (2007). Specifically, the second image, isoproterenol group, and fifth image, isoproterenol + propranolol group, were duplicates. The representative images are corrected below. The underlying data and conclusions presented in this Letter are not affected by the errors.