Figure 4

Successfully engrafted tumors which had grown to a size to be passaged were primarily vascularized by vessels derived from the murine hosts. Comparison of the microvessel density (MVD) in the patient surgical specimens (ss) and engrafted tumors (-1p) showed that most of the huCD31(+) vessels were lost during tumor growth in the mouse. At the time of first passage, few remaining remnants of huCD31(+) cells were detectable and the major source of blood vessels was the recruitment of msCD34(+) vessels of murine origin. (Values shown are averages of 5 fields/tumor counted at 20×).