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Immunohistochemical detection of p53, PTEN, Rb, and p16 in canine osteosarcoma using tissue microarray.

ABSTRACT: Although inactivating mutations of tumor suppressor genes are well described in cell lines of canine osteosarcoma (OS), expression of tumor suppressor proteins in spontaneous disease is poorly characterized. We determined the immunohistochemical expression of p53, PTEN, Rb, and p16 in a large cohort of dogs with OS. Formalin-fixed, paraffin-embedded samples of canine OS were analyzed retrospectively. Primary tumor samples from 145 dogs, collected between 2003 and 2008, were evaluated by tissue microarray. Streptavidin-biotin complex immunohistochemistry was performed using monoclonal antibodies for Rb and PTEN and polyclonal antibodies for p16 and p53. The average age of dogs was 7.6 y, and 118 of 145 (81%) were purebred. Most commonly represented purebreds were Greyhound (23%), Rottweiler (11%), and Labrador Retriever (10%). Immunohistochemical detection of p53, PTEN, Rb, and p16 was 81%, 61%, 66%, and 66%, respectively. The staining pattern for p16 was primarily cytoplasmic; the predominant pattern for PTEN, Rb, and p53 was cytoplasmic and nuclear. Exclusively cytoplasmic staining was noted in 19% of samples positive for p53 and 8% of samples positive for Rb. Kaplan-Meier curves showed that protein expression was not associated with significant differences in overall survival ( p > 0.191). We documented heterogeneity in both immunostaining and subcellular localization of tumor suppressor proteins, providing further characterization of canine OS.

SUBMITTER: Russell DS

PROVIDER: S-EPMC6505918 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Backgroundp53 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 Serine392 in canine skin endothelial tumours; and 2) to determine if any relationship exists between p53 and phospho-p53 Serine392 overexpression and cell proliferation.Resultsp53 and phospho-p53 Serine392 immunolabeling 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 < .001) and in well-differentiated hemangiosarcomas (median, 82.40%; IQR, 66.49-83.17%) versus hemangiomas (p = .002). Phospho-p53 Serine392 immunoreactivity was significantly higher in hemangiosarcomas (median, 53.80%; IQR, 0-69.50%) than in hemangiomas (median, 0%; IQR, 0.0%) (p < .001). Positive correlation of the overexpression of p53 and phospho-p53 Serine392 with mitotic count and Ki-67 index was found in the cutaneous vascular tumours (p < .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 < .001), and that specifically of well-differentiated hemangiosarcomas (median, 24.60%; IQR, 15.45-39.35%) (p = .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 = .001; p = .006, respectively).ConclusionsThe p53 and phospho-p53 Serine392overexpression 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.

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Immunohistochemical detection of p53, PTEN, Rb, and p16 in canine osteosarcoma using tissue microarray.

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