Vascularization of an engrafted patient colon tumor. A patient colon tumor was implanted in a cohort of mice and vessel development was analyzed over 8 weeks. Vessels in the original patient specimen labeled strongly for huCD31 (A) and not for msCD34 (D). Representative sections showing loss of huCD31(+) vessels (B- 4 weeks, C- 7 weeks) and presence of msCD34(+) vessels (E- 4 weeks, F- 7 weeks) are shown. The graph (G) summarizes this process; huCD31(+) vessels were rapidly lost, and by one week, mouse vessels were the predominate vessels present in the colon tumors (no data for msCD34 at 2 weeks; bars = 100 μ).