Small tumors need blood vessels for growth but it is not clear whether aggregates of malignant cells can induce vascularization or whether these cells grow by co-opting preexisting vessels. In March 15 Journal of Clinical Investigation Peter Vajkoczy and colleagues from University of Heidelberg, Germany, show that new vessels occur as a continuing process of growth and remodeling, starting very early in tumor progression (J Clin Invest 2002, 109:777-785).

Vajkoczy et al. used intravital epifluorescence microscopy and confocal microscopy to visualize C6 microglioma vascularization and tumor cell behavior. They found that multicellular aggregates (< 1 mm³) initiate vascular growth by angiogenic sprouting via the simultaneous expression of VEGFR-2 and Ang-2 by host and tumor endothelium. In addition, they provide evidence that host blood vessels are not co-opted by the tumor cells but rather are used as trails for glioma cell invasion of the adjacent host...