Various naturally developing tumors in dogs often have inactivation of the p53 tumor suppressor gene, which may be 1 of the multiple step-wise genetic changes during tumorigenesis. This study indicates that p53 gene can be a target for gene therapy for tumors in dogs.

ABSTRACT. Telomeres are specific structures present at the end of liner chromosomes. DNA polymerase can not synthesize the end of liner DNA and, as a result, the telomeres become progressively shortened by successive cell divisions. To overcome the end replication problem, telomerase adds new telomeric sequences to the end of chromosomal DNA. The enzyme activity is undetectable in most normal human adult somatic cells, in which shortening of the telomere is thought to limit the somatic-cell life span. In contrast to normal somatic cells, many human tumors possess telomerase activity. The present study looked at whether telomerase activity might serve as a marker for canine tumors. Telomerase activity was measured using the telomeric repeat amplification protocol assay. Normal dog somatic tissues showed little or no telomerase activity, while normal testis exhibited a high level of telomerase activity. We measured telomerase activity in tumor samples from 45 dogs; 21 mammary gland tumors, 16 tumors developed in the skin and oral cavity, 7 vascular tumors and 1 Sertoli cell tumor. Greater than 95% of the tumor samples contained telomerase activity (3~924 U/2 µg protein). The results obtained in this study indicated that telomerase should be a useful diagnostic marker for a variety of dog tumors, and it may serve as a target for antitumor chemotherapy.-KEY WORDS: canine, telomerase, tumor, tumor marker.

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.

ABSTRACT. Eight new feline mammary adenocarcinoma cell lines derived from either primary or metastatic lesions were established. The morphology of all the cell lines was epithelioid and round to spindle in shape, with cell growth occurring in a monolayer fashion. On immunohistochemistry, these cells reacted with anti-keratin and anti-vimentin antisera. The doubling time of these cells was between 19 and 54 hr. Tumor masses were developed in nude mice by subcutaneous inoculation of the cells that were histologically identical to their original mammary tumor lesions. Telomerase activities measured using the telomeric repeat amplification protocol assay revealed high telemetric activity in all of the cells. KEY WORDS: feline, mammary tumor cell line, primary and metastatic lesion.J. Vet. Med. Sci. 67(12): 1273-1276, 2005 Feline mammary cancer (FMC) is the third most common neoplasm following hematopoietic and skin tumors [1,6]. Most cases of FMC are histologically adenocarcinoma [3]. This tumor shows local infiltrative-destructive growth and frequently metastasizes to the regional lymph nodes, lung and pleura in the early stages of disease [6,15]. Establishment of cell lines from FMC has been conducted, however the number of established cells has been limited [2,8,10], suggesting that the establishment of FMC cell lines is difficult compared to those of other animal species. FMC has many features, including specific biological behaviors and histopathological appearance as well as poor prognosis, and may be an attractive model for research on human breast cancer [7,9,15]. We report herein the establishment and characterization of eight FMC cells derived from either primary or metastatic lesions of five cats with spontaneous FMC.Tissue samples were obtained from 13 cats with FMC admitted to the Veterinary Hospital at the University of Tokyo (Fig. 1). Tumor cells were collected from the surgical specimen or by thoracocentesis in the cats with thoracic metastasis. Tissue samples were placed in 50-ml tubes with phosphate buffer solution (PBS) supplemented with 0.2-mg/ ml gentamycin sulfate (Sigma Chemical Co., St. Louis, MO, U.S.A.) and kept overnight at 4°C. They were then minced into 1-to 2-mm 3 pieces and digested with collagenase mixed solution of DNase and pronase (Sigma Chemical Co.) for 1 hr at 37°C under constant stirring. The digested cells were then incubated in RPMI 1640 (Nissui Pharmaceutical Co., Tokyo, Japan) supplemented with 20% fetal bovine serum (FBS) (Equitech-Bio Inc., Ingram, TX, U.S.A.), 0.01 mg/ml L-glutamine (Nissui Pharmaceutical Co.), fungizone (Gibco BRL., Grand Island, N.Y., U.S.A.) and 5 mg/l gentamycin sulfate (Sigma Chemical Co.), and incubated at 37°C in a humidified atmosphere of 5% CO 2 . Cells collected from pleural effusion were centrifuged and washed with PBS, then cultured under the same conditions described above. After the 10th passages, when cell growth seemed to be stable, the concentrations of FBS in the culture medium were decreased from 20% to 10%.Eight feline mammary adenoca...

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.