Different cytogenetic findings in two clinically similar leukaemic dogs

RAS, FLT3, and C-KIT mutations in immunophenotyped canine leukemias

OBJECTIVE

To determine the frequency of FLT3, C-KIT, and RAS mutations in canine leukemia patients.

MATERIALS AND METHODS

Ethylenediamine tetra-acetic acid blood samples were recruited from dogs with suspected leukemia, categorized by quantitative and cytological evaluation and immunophenotyping. Flow cytometry was carried out using antibodies against CD3; CD3e; CD4; CD5; CD8; CD11a, b, c, and d; CD14; CD21; CD34; CD45 and 45RA; CD79a; CD90 (THY-1); major histocompatibility complex II; myeloperoxidase; MAC387; and neutrophil-specific antibody. Genomic DNA was extracted from whole blood and analyzed for mutations in N, H, and K-RAS, FLT3, and C-KIT genes by polymerase chain reaction and sequencing.

RESULTS

Fifty-seven (77.0%) of 74 samples submitted from dogs with suspected leukemia had cytologically and immunophenotypically confirmed leukemia. There were 36 (63.2%) acute leukemias, 16 (28.1%) chronic, 3 (5.3%) prolymphocytic, 1 natural killer cell, and 1 chronic leukemia undergoing blast transformation. N-RAS mis-sense mutations were identified in 14 (25%) dogs with acute myeloid (AML) or lymphoid (ALL) leukemia, and also in one dog in the leukemic phase of lymphoma. Mutations in K-RAS were found in two dogs with AML. There were no H-RAS mutations. FLT3 internal tandem duplications were identified in three dogs with ALL, and a mis-sense mutation was found in one dog with ALL. C-KIT mutations were identified in three dogs with AML. Sixty-one percent of dogs with acute leukemia harbored mutations in N/K-RAS, FLT3, or C-KIT.

CONCLUSION

RAS, FLT3, and C-KIT mutations, analogous to those found in human leukemia, occur commonly in acute canine leukemia.

Polysomy 13 in a canine prostate carcinoma underlining its significance in the development of prostate cancer

The dog is a well-accepted model for prostate cancer in man because of the striking similarities between both species with respect to the clinical course of the disease as well as to its similar histopathology. Cytogenetic investigations of human prostate cancers has revealed the frequent occurrence of trisomies 7, 8, and 17. In this report, we present a case of prostate carcinoma in a dog characterized by polysomy 13 as the sole cytogenetic abnormality. Along with the known homology between canine chromosome 13 and human chromosome 8 these findings suggest that a homologous area on both chromosomes plays a crucial role in subsets of prostate cancer in both species.

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, anti-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 conformation polymorphism analysis, and expression of canine MDM2 protein was evaluated by use of immunohistochemical analysis, using anti-MDM2 antibody.

RESULTS

Immunohistochemical analysis of dog osteosarcoma cell lines with apparent aneuploidy revealed frequent hyperamplification of centrosomes in the 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 normal lymph nodes from these dogs. In 8 of the 9 tumors, mutation of p53 gene or overexpression of MDM2, or both, was detected.

CONCLUSIONS AND CLINICAL RELEVANCE

Various types of naturally developing tumors in dogs often have hyperamplification of centrosomes associated with chromosome instability. Hyperamplification of centrosomes is a novel tumor marker for use in cytologic and histologic examinations of clinical specimens obtained from dogs.

Cytogenetic analysis of three oropharyngeal malignant melanomas in dogs

Three cases of histologically confirmed oropharyngeal malignant melanomas in dogs are presented including clinical examinations and cytogenetic analysis. Case one showed a hyperdiploid karyotype. Case two, a recurrent tumour, had a highly hypodiploid karyotype with supernumerary meta- and submetacentric chromosomes in all metaphases analysed. In the third case, a clonal fusion of chromosome 1 and 25 was observed. Comparing these results with another case of canine cutaneous melanoma as well as with human malignant melanomas reported in the literature, these tumours obviously often show cytogenetic aberrations like aneuploidy and centric fusions.

Trisomy 1 in a canine acute leukemia indicating the pathogenetic importance of polysomy 1 in leukemias of the dog

We report on a canine acute myeloid leukemia showing a trisomy 1 and a t(X;8) as clonal cytogenetic abnormalities. Comparing these results with similar cases of canine leukemias reported in the literature, one realizes that trisomy 1 is a recurrent cytogenetic finding in canine acute leukemia. Trisomy 1 may be a specific anomaly associated with either etiology or progression of this disease. As with comparable human neoplasms, cytogenetic investigations could be of diagnostic and prognostic significance for canine hematopoietic diseases. Moreover, as trisomies are recurrent cytogenetic findings in human leukemias, as well, comparative gene mapping in future studies may help to focus the etiologic basis of the disease to particular chromosomal segments instead of whole chromosomes.

Trisomy 18 in a canine thyroid adenoma

A canine thyroid adenoma showing trisomy 18 as the sole clonal cytogenetic abnormality (9 of 30 analyzed metaphases) is reported. Because trisomies are a recurrent cytogenetic finding in human benign thyroid tumors as well, it is suggested that the molecular relationship between these trisomies and the development of thyroid tumors can be determined by comparative gene mapping.