Figure 2

Expression of VHL and PDGFRβ proteins in canine splenic hematoma and in canine hemangiosarcoma tissues. Serial 5-μm sections from paraffin-embedded splenic hematomas or hemangiosarcomas were stained with an irrelevant control antibody, or with antibodies against VHL or PDGFRβ as indicated on the left. Photomicrographs represent similar or contiguous regions within each tissue at 640× magnification. Two samples of splenic hematomas and eight samples of canine hemangiosarcoma were stained for VHL. Both splenic hematomas and five hemangiosarcomas were stained for PDGFRβ. One of the splenic hematomas and two hemangiosarcomas (the tumors used to derive the DD-1 and Dal-4 cell lines) are shown to illustrate the observed patterns. Expression of relevant antigens is indicated by red staining. VHL staining in the splenic hematomas was restricted to blood vessel lining cells (black arrows), whereas in the hemangiosarcomas, VHL staining was seen diffusely in the tumor cells, but not in associated inflammatory cells. In contrast, PDGFRβ staining was seen in blood vessel lining cells in the splenic hematomas, but was seen both in tumor cells and in associated inflammatory cells in the hemangiosarcomas (blue arrows). Bars = 20 μm