Immunohistochemical analysis of ocular hemangiomas and hemangiosarcomas in dogs

Purpose  To determine if molecular markers typically associated with ultraviolet exposure could be detected in canine ocular hemangiomas (HA) and hemangiosarcomas (HSA).
Methods  Paraffin-embedded samples of canine ocular HA ( n  = 6) and HSA ( n  = 6) were examined for the presence of p53, p21, p16, cyclin D, PCNA, pAkt, telomerase, and estrogen receptor (ER)-α using immunohistochemistry.
Results  p53 and cyclin D protein were not detected in any of the canine HA or HSA samples. The majority of the HA and HSA were negative for both p21 and telomerase. pAkt immunoreactivity was absent in one HA, one HSA, but was present in five HA and five HSA. All of the HA or HSA samples were strongly positive for p16 and PCNA. ERα was expressed in all of the samples examined; there was more intense staining in the HSA samples compared to the HA samples.
Conclusions  Results from this study describe the protein expression, via immunohistochemistry, that might be altered in UV exposure in HA and HAS formation. p53 may not play an important role in tumor development; rather, in the tumors examined, expression of cell cycle regulators independent of the p53 pathway appear central in HA and HSA formation and progression. In addition, this study finds that ERα may be involved in promoting the invasive behavior associated with HSA.