EDITORIALS Angiogenic Heterogeneity: Regulation of Neoplastic

Cells cannot survive if they lack adequate oxygen and nutri-ent supply or cannot dispose of toxic molecules. Oxygen can diffuse from capillaries for only 150–200 m. When distances of cells from a blood supply exceed this, cell death follows (1,2). Thus, the growth and survival of tumor masses beyond 0.5 mm in diameter require neovascularization, i.e., angiogenesis (3). In this issue of the Journal, Achilles et al. (4) injected human liposarcoma cells (tumor fragments or cells) into the subcutis of severe combined immunodeficient mice. The different tumor fragments and liposarcoma cells gave rise to fast-growing, slow-growing, or small dormant tumors. The growth rate of the tu-mors correlated directly with microvessel density and correlated inversely with tumor cell apoptosis. The authors concluded that human liposarcomas are heterogeneous for induction of angio-genesis and suggest that the failure to induce angiogenesis ca