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• VEGF expression / angiogenic switch

VEGF expression / angiogenic switch

The angiogenic switch can be represented as a balance, which tips toward neovascularization when pro-angiogenic factors outweigh anti-angiogenic factors.¹

Angiogenesis is tightly regulated by a number of pro- and anti-angiogenic molecules. Under normal conditions, there is a delicate balance between pro- and anti-angiogenic factors, and angiogenesis does not occur. However, during tumor growth, a variety of environmental and cellular triggers leads to overexpression of pro-angiogenic factors. These factors, including vascular endothelial growth factor (VEGF), can tip the balance toward angiogenesis.⁶

The moment at which a tumor begins to overexpress pro-angiogenic factors, such as VEGF, is generally referred to as the angiogenic switch. The switch overwhelms the delicate balance of pro- and anti-angiogenic factors to grow new vasculature, thereby facilitating the growth of the tumor.⁶

Visualizing the angiogenic switch

The images below depict the switch from nonangiogenic to angiogenic tumor phenotype.

Panels A and B represent microscopic tumors generated from a nonangiogenic tumor cell line. Panel C represents a macroscopic tumor (also from a nonangiogenic cell line) that has undergone a spontaneous switch from tumor dormancy to an angiogenic phenotype.
Images reproduced from Naumov GN, Bender E, Zurakowski D, et al. J Natl Cancer Inst. 2006;98:316-325.

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