At Children’s Hospital in Boston in the 1990s, the surgeon-scientist Judah Folkman demonstrated that certain activated signaling pathways within cancer cells, ras among them, could also induce neighboring blood vessels to grow. A tumor could thus “acquire” its own blood supply932 by insidiously inciting a network of blood vessels around itself and then growing, in grapelike clusters, around those vessels, a phenomenon that Folkman called tumor angiogenesis.
