Angiogenic activity of human tumor plasma membrane components

Plasma membranes from the human colon adenocarcinoma cell line HT-29 have been isolated and examined for the presence of angiogenic activity. Membrane-associated macromolecules extracted with Triton X-100 were fractionated on immobilized wheat germ agglutinin. The fraction which bound specifically (about 200 ng of protein/mL packed cells) was highly angiogenic when assayed on the chick embryo chorioallantoic membrane. As little as 0.2 ng of this human tumor derived material consistently induced neovascularization. Similarly, 1-2 ng of this material implanted into the rabbit cornea induced new vessel growth (5-8 mm) within 10 days. The plasma membranes of eight other human tumor lines were examined for angiogenic activity. For each, the wheat germ agglutinin bound material induced neovascularization at the low nanogram level. In contrast, the wheat germ agglutinin bound material derived from purified plasma membranes of two normal human diploid fibroblast cell lines failed to induce an angiogenic response on the chick chorioallantoic membrane, even at microgram levels.