KDR and Kaposi's sarcoma: Immunofluorescence analysis revealed that mECKnull.rK133 tumor cells expressed markers implicated in KS pathogenesis such as the vascular marker VEGF-R2 (Figure 4D, middle panels) and podoplanin, a lymphatic endothelial KS marker, (Figure 4D, bottom panels) but they did not express the EPC marker, CD133 (data not shown).