Prolonged tumor dormancy by prevention of neovascularization in the vitreous.

Tumors release a diffusible substance that stimulates neovascularization. To study the neovascularization that occurs in diabetic retinopathy, we implanted V2 carcinomas and mouse ependymoblastomas into the vitreous of experimental animals. In the vitreous, unlike previous sites, the tumors failed to stimulate neovascularization. They grew for weeks as small, unvascularized, three-dimensional aggregates of cells. Explosive growth into a large,...