Results of hyperamplification of centrosomes in naturally developing tumors of dogs

Objective-To evaluate results of centrosome hyperamplification in naturally developing tumors of dogs. Sample Population-Tumor specimens from 9 dogs with tumors (rhabdomyosarcoma , osteosarcoma, chondrosarcoma, myxosarcoma, and mammary gland tumor) and 2 canine osteosarcoma cell lines. Procedure-3 antibodies for centrosome proteins (ie, anti-gamma -tubulin, an ti-BRCA1, and anti-pericentrin) were used for immunohistochemical analysis. Double immunostaining for centrosomes was used to confirm the specificity of these antibodies for centrosomes. Mutational analysis of the canine p53 gene was carried out by polymerase chain reaction-single-strand conformatio n polymorphism analysis, and expression of canine MDM2 protein was evaluate d by use of immunohistochemical analysis, using anti-MDM2 antibody. Results-Immunohistochemical analysis of dog osteosarcoma cell lines with ap parent aneuploidy revealed frequent hyperamplification of centrosomes in th e osteosarcoma cell lines. Similar hyperamplified centrosomes were detected in the tumor tissues from all of the 9 tumors. The frequency of cells with hyperamplified centrosomes (3 to 20/cell) in each tumor tissue ranged from 9.50 to 48.1%, whereas centrosome hyperamplification was not observed in n ormal lymph nodes from these dogs. In 8 of the 9 tumors, mutation of p53 ge ne or overexpression of MDM2, or both, was detected. Conclusions and Clinical Relevance-Various types of naturally developing tu mors in dogs often have hyperamplification of centrosomes associated with c hromosome instability. Hyperamplification of centrosomes is a novel tumor m arker for use in cytologic and histologic examinations of clinical specimen s obtained from dogs.