Vessel formation in subcutaneous tumors in xenografts of MDA MB231 in presence or absence of PICP. Immunohistochemistry and immunofluorescence identify CD31- and CD34-expressing endothelial cells. Exemplary micrographs of tumors are shown out of 3 to 9 tumors examined for each time point. Left: Sections from criopreserved tumors dissected after 14, 21 and 28 days are processed for immunohistochemistry with CD31 antibody, followed by a secondary antibody conjugated either with TRITC (A, B and G, H) or biotin (C-F). Bar is 50 μm for A-D and G-H, and 25 μm for E-F. Sections from paraffin embedded tumors dissected after 24 and 38 days are decorated with antibody to CD34 and revealed by Immunoperoxidase.100× Bar is 50 μm.