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  • Author or Editor: Kenichi Masuda x
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Abstract

Objective—To measure telomere length and telomerase activity in naturally occurring canine mammary gland tumors.

Sample Population—27 mammary gland tumor specimens obtained during resection or necropsy and 12 mammary gland tissue specimens obtained from healthy (control) dogs.

Procedure—Telomere length in tissue specimens was measured by use of restriction endonuclease digestion and Southern blot analysis. Telomerase activity was measured by use of a telomeric repeat amplification protocol assay.

Results—Telomere length in mammary gland tumors ranged from 11.0 to 21.6 kilobase pairs (kbp; mean ± SEM, 14.5 ± 0.5 kbp) but did not differ among tumor types. Telomeres in mammary gland tumors were slightly shorter than in normal tissue specimens, but telomere length could not be directly compared between groups, because mean age of dogs was significantly different between groups. Age was negatively correlated with telomere length in control dogs but was not significantly correlated with length in affected dogs. Telomerase activity was detected in 26 of 27 mammary gland tumors and in 4 of 12 normal tissue specimens. However, telomerase activity and telomere length were not correlated in tumor specimens.

Conclusion and Clinical Relevance—Telomere length is maintained in canine mammary gland tumors regardless of the age of the affected dog. Measurement of telomere length may be a useful tool for monitoring the in vivo effects of telomerase inhibitors in dogs with tumors. (Am J Vet Res 2001; 62:1539–1543)

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in American Journal of Veterinary Research

Abstract

Objective—To generate an adenoviral vector that expressed the canine p53 gene and investigate its growth-inhibiting effect on canine osteosarcoma and mammary adenocarcinoma cell lines.

Sample Population—2 canine osteosarcoma cell lines (HOS, OOS) and 3 canine mammary adenocarcinoma cell lines (CHMp, CIPm, and CNMm).

Procedure—An adenoviral vector that expressed the canine p53 gene (AxCA-cp53) was generated. p53 gene expression was examined by use of reverse transcription (RT)-polymerase chain reaction (PCR) assay and immunohistochemistry. Susceptibility of cell lines to the adenoviral vector was determined by infection with an adenoviral vector that expresses β-galactosidase (AxCA-LacZ) and 3-indolyl-β-D-galactopyranoside staining. Growth inhibitory effects were examined by monitoring the numbers of cells after infection with mock (PBS) solution, AxCA-LacZ, or AxCA-cp53. The DNA contents per cell were measured by flow cytometry analysis. Apoptotic DNA fragmentation was detected by use of a terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling assay.

Results—AxCA-cp53-derived p53 gene mRNA and P53 protein were detected by RT-PCR analysis and immunohistochemistry, respectively. Multiplicity of infection at which 50% of cells had positive 3-indolyl- β-D-galactopyranoside staining results ranged from 10 to 50. AxCA-cp53 induced growth inhibition in a dosedependent manner. Arrest of the G1-phase population and apoptotic DNA fragmentation were observed in cells infected with AxCA-cp53.

Conclusions and Clinical Relevance—AxCA-cp53 inhibits cell growth via induction of cell cycle arrest and apoptosis in canine osteosarcoma and mammary adenocarcinoma cell lines that lack a functional p53 gene. AxCA-cp53 may be useful to target the p53 gene in the treatment of dogs with tumors. (Am J Vet Res 2003;64:880–888)

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in American Journal of Veterinary Research

Abstract

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-γ-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–singlestrand 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. (Am J Vet Res 2001;62:1134–1141)

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in American Journal of Veterinary Research

Abstract

Objective—To perform molecular cloning of the canine telomerase reverse transcriptase (TERT) gene and determine its expression in neoplastic and nonneoplastic cells.

Sample Population—9 canine tumor cell lines derived from various neoplasms, 16 primary canine tumors, and tissues from 15 normal canine organs.

Procedure—Tumor cell lines were derived from canine tumors that included osteosarcoma, mammary gland adenocarcinoma, melanoma, acute lymphoblastic leukemia, lymphoma, and mastocytoma and a canine primary fibroblast culture. Canine TERT complementary DNA (cDNA) was amplified by use of polymerase chain reaction (PCR) and sequenced. Expression of TERT mRNA was examined by reverse transcription (RT)-PCR assay. Telomerase activity was measured by use of the telomeric repeat amplification protocol assay.

Results—The canine TERT cDNA clone was 237 base pairs in length and contained a central region encoding the reverse transcriptase motif 2. Expression of TERT mRNA was detected in canine tumor cell lines that had telomerase activity but not in telomerasenegative canine primary fibroblasts. The TERT mRNA was detected in 13 of 16 canine tumor tissues and several normal tissues such as liver, ovary, lymph node, and thymus. A significant correlation between TERT expression level and telomerase activity was noted.

Conclusions and Clinical Relevance—Expression of TERT mRNA was closely associated with telomerase activity in neoplastic cells as well as some non-neoplastic cells from dogs. In addition to telomerase activity, expression of TERT mRNA can be used as a marker of tumor cells. (Am J Vet Res 2003;64:1395–1400)

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in American Journal of Veterinary Research