Detecting p53 protein in dog skin hemangiomas and hemangiosarcomas

Abstract

BACKGROUND: p53 protein is essential for the regulation of cell proliferation. Aberrant accumulation of it usually occurs in cutaneous malignancies. Mutant p53 is detected by immunohistochemistry because it is more stable than the wild-type p53. However, post-translational modifications of p53 in response to ultraviolet radiation are important mechanisms of wild-type p53 stabilization, leading to positive staining in the absence of mutation. The aims were: 1) to analyze the immunohistochemical expression of p53 and phospho-p53 Serinein canine skin endothelial tumours; and 2) to determine if any relationship exists between p53 and phospho-p53 Serineoverexpression and cell proliferation. RESULTS: p53 and phospho-p53 Serineimmunolabeling was examined in 40 canine cutaneous endothelial tumours (13 hemangiomas and 27 hemangiosarcomas). Their expression was associated with tumour size, hemangiosarcoma stage (dermal versus hypodermal), histological diagnosis and proliferative activity (mitotic count and Ki-67 index). Statistical analysis revealed a significant increase of p53 immunoreactivity in hemangiosarcomas (median, 74.61%; interquartile range [IQR], 66.97-82.98%) versus hemangiomas (median, 0%; IQR, 0-20.91%) (p&#x2009;<&#x2009;.001) and in well-differentiated hemangiosarcomas (median, 82.40%; IQR, 66.49-83.17%) versus hemangiomas (p&#x2009;=&#x2009;.002). Phospho-p53 Serineimmunoreactivity was significantly higher in hemangiosarcomas (median, 53.80%; IQR, 0-69.50%) than in hemangiomas (median, 0%; IQR, 0.0%) (p&#x2009;<&#x2009;.001). Positive correlation of the overexpression of p53 and phospho-p53 Serinewith mitotic count and Ki-67 index was found in the cutaneous vascular tumours (p&#x2009;<&#x2009;.001). The Ki-67 index of the hemangiomas (median, 0.50%; IQR, 0-2.80%) was significantly lower than that of the hemangiosarcomas (median, 34.85%; IQR, 23.88-42.33%) (p&#x2009;<&#x2009;.001), and that specifically of well-differentiated hemangiosarcomas (median, 24.60%; IQR, 15.45-39.35%) (p&#x2009;=&#x2009;.001). Immunolabeling of 18 visceral hemangiosarcomas showed that the p53 (median, 41.59%; IQR, 26.89-64.87%) and phospho-p53 Serine392 (median, 0%; IQR, 0-22.53%) indexes were significantly lower than those of skin (p&#x2009;=&#x2009;.001; p&#x2009;=&#x2009;.006, respectively). CONCLUSIONS: The p53 and phospho-p53 Serineoverexpression together with high proliferative activity in hemangiosarcomas versus hemangiomas indicated that p53 might play a role in the acquisition of malignant phenotypes in cutaneous endothelial neoplasms in dogs. The Ki-67 index may be useful in distinguishing canine well-differentiated hemangiosarcomas from hemangiomas.