Canine transmissible venereal tumor

Canine transmissible venereal tumor (CTVT), also called transmissible venereal tumor (TVT), Sticker tumor and infectious sarcoma is a tumor of the dog and other canids that mainly affects the external genitalia, and is transmitted from animal to animal during copulation.

History

Canine TVT was initially described by Russian veterinarian M.A. Novinsky (1841–1914) in 1876, when he demonstrated that the tumor could be transplanted from one dog to another by infecting them with tumor cells.cite web|author=Mello Martins, M.I.; de Souza, F. Ferreira; Gobello, C.|year=2005|title=Canine transmissible venereal tumor: Etiology, pathology, diagnosis and treatment|work=Recent Advances in Small Animal Reproduction|url=http://www.ivis.org/advances/Concannon/gobello2/chapter.asp?LA=1|accessdate=2006-05-25]

It has been proposed that the tumor cells responsible for canine transmissible venereal tumor be considered a parasitic cancer. It has been estimated that the tumour cell line originated 200 to 2,500 years ago in a wolf, coyote, or old Asian dog breed such as a Husky or Shih Tzu. The tumour cells are themselves the infectious agents. [cite journal |last=Murgia |first=C |coauthors=Pritchard JK, Kim SY, Fassati A, Weiss RA |title=Clonal Origin and Evolution of a Transmissible Cancer |journal=Cell |volume=126 |issue=3 |pages=477–87 |date=2006-08-11 | pmid=16901782 | doi=10.1016/j.cell.2006.05.051 ] cite web |last=Choi |first=Charles Q. |title=Contagious Canine Cancer Spread by Parasites |publisher=LiveScience |date=2006-08-10 |url=http://www.livescience.com/animalworld/060810_dog_cancer.html |accessdate=2006-08-11]

Biology

CTVT cells have fewer chromosomes than normal cells. Dog cells normally have 78 chromosomes; CTVT tumor cells contain 57–64 chromosomes that are very different in appearance from normal dog chromosomes. All dog chromosomes except X and Y are acrocentric, having a centromere very near to the end of the chromosome, while many of the CTVT chromosomes are metacentric or submetacentric, having a centromere nearer to the middle.cite journal |author=Hasler A, Weber W |title=Theriogenology question of the month. Transmissible venereal tumor (TVT) |journal=J. Am. Vet. Med. Assoc. |volume=216 |issue=10 |pages=1557–9 |year=2000 |pmid=10825939] There is no evidence that the tumor is caused by a virus or virus-like organism. All tumor cells of this type of cancer share extremely similar genetic code, often if not always unrelated to the DNA of their host. Specifically, the LINE-1 (Long interspersed nuclear element) element in the tumor cells is in a different location than in normal canine DNA.cite journal|author=Murgia, et al.;|title=Clonal Origin and Evolution of a Transmissible Cancer |journal=Cell |volume=126 |pages=477–487 |pmid=16901782 |accessdate= |doi=10.1016/j.cell.2006.05.051 |year=2006] This demonstrates that the tumors do not arise from separate cancerous transformation in individual animals. Rather, the malignant tumor cells from one dog are transferred to another dog via coitus, licking, biting, and sniffing tumor-affected areas. [ Murgia C, Pritchard JK, Kim SY, Fassati A, Weiss RA. Clonal origin and evolution of a transmissible cancer. Cell. 2006 Aug 11;126(3):477-87.] [ Dingli D, Nowak MA. Cancer biology: infectious tumour cells. Nature. 2006 Sep 7;443(7107):35-6. B). ]

CTVT is most commonly seen in sexually active dogs in tropical and subtropical climates. The disease is spread when dogs mate, and it can even be transmitted to other canine species, such as foxes and coyotes. [cite journal |author=Mukaratirwa S, Gruys E |title=Canine transmissible venereal tumour: cytogenetic origin, immunophenotype, and immunobiology. A review |journal=The Veterinary quarterly |volume=25 |issue=3 |pages=101–11 |year=2003 |pmid=14535580] Spontaneous regression of the tumor can occur, probably due to a response from the immune system.cite journal |author=Stettner N, Brenner O, Eilam R, Harmelin A |title=Pegylated liposomal doxorubicin as a chemotherapeutic agent for treatment of canine transmissible venereal tumor in murine models |journal=J. Vet. Med. Sci. |volume=67 |issue=11 |pages=1133–9 |year=2005 |pmid=16327225 |doi=10.1292/jvms.67.1133] CTVT undergoes a predictable cycle: the initial growth phase of four to six months (P phase), a stable phase, and a regression phase (R phase), [cite journal |author=Liao K, Hung S, Hsiao Y, Bennett M, Chu R |title=Canine transmissible venereal tumor cell depletion of B lymphocytes: molecule(s) specifically toxic for B cells |journal=Vet. Immunol. Immunopathol. |volume=92 |issue=3–4 |pages=149–62 |year=2003 |pmid=12730015 |doi=10.1016/S0165-2427(03)00032-1] although not all CTVTs will regress. The tumor does not often metastasize (occurring in about 5 percent of cases), [cite web |title=Canine Transmissible Venereal Tumor: Introduction |work=The Merck Veterinary Manual |date=2006 |url=http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/112500.htm |accessdate=2007-04-24 ] except in puppies and immunocompromised dogs. Metastasis is most commonly to regional lymph nodes, but can also be seen in the skin, brain, eye, liver, spleen, testicle, and muscle.cite journal |author=Rogers K, Walker M, Dillon H |title=Transmissible venereal tumor: a retrospective study of 29 cases |journal=Journal of the American Animal Hospital Association |volume=34 |issue=6 |pages=463–70 |year=1998 |pmid=9826280] Biopsy is necessary for diagnosis.

igns and symptoms

In male dogs, the tumor affects the penis or prepuce. In females, it affects the vagina or labia. Rarely, the mouth or nose are affected.cite book|author=Morrison, Wallace B.|title=Cancer in Dogs and Cats|edition=1st ed.|publisher=Williams and Wilkins|year=1998|id=ISBN 0-683-06105-4] The tumor often has a cauliflower-like appearance. Signs of genital TVT include a discharge from the prepuce and in some cases urinary retention, from blockage of the urethra. Signs of nasal TVT include oronasal fistulae, nosebleeds and other nasal discharge, facial swelling, and enlargement of the submandibular lymph nodes. [cite journal |author=Papazoglou L, Koutinas A, Plevraki A, Tontis D |title=Primary intranasal transmissible venereal tumour in the dog: a retrospective study of six spontaneous cases |journal=Journal of veterinary medicine. A, Physiology, pathology, clinical medicine |volume=48 |issue=7 |pages=391–400 |year=2001 |pmid=11599677]

Treatment

Chemotherapy is very effective for TVT, but surgery alone often leads to recurrence. Surgery may be difficult due to the location of these tumors. The prognosis for complete remission with chemotherapy is excellent.cite book |author=Ettinger, Stephen J.;Feldman, Edward C. |title=Textbook of Veterinary Internal Medicine |edition=4th ed. |publisher=W.B. Saunders Company |year=1995 |id=ISBN 0-7216-6795-3] The most common chemotherapy agents used for TVT are vincristine, vinblastine, and doxorubicin. Radiation therapy may be effective when chemotherapy does not work.

References

External links

* [http://www.veterinarypartner.com/Content.plx?P=A&S=0&C=0&A=1650 "Transmissible Venereal Tumor" from The Pet Health Library]
*IVIS — http://www.ivis.org/docarchive/A1233.0405.pdf
*Israel Veterinary Medical Association — [http://www.isrvma.org/article/57_1_5.htm Transmissible Venereal Tumors]
*New Scientist — [http://www.newscientist.com/article.ns?id=dn9713&feedId=online-news_rss20 Riddle of infectious dog cancer solved]
*ScienceDaily — [http://www.sciencedaily.com/releases/2006/08/060811075902.htm Contagious Cancer In Dogs Confirmed; Origins Traced To Wolves Centuries Ago] August 11, 2006 University College London
*LiveScience — [http://www.livescience.com/animalworld/060810_dog_cancer.html Contagious Canine Cancer Spread by Parasites] 10 August 2006 10:34 am ET (Charles Q. Choi)
*News @ Nature.com — [http://www.nature.com/news/2006/060807/full/060807-13.html Dog cancer traced back to wolf roots] — 200-year-old tumour has mellowed with age Published online: 10 August 2006; | doi:10.1038/news060807-13 (Narelle Towie)
*Veterinary Pathology — [http://www.vetpathology.org/cgi/content/abstract/33/3/257 Immunohistochemical characterization of canine transmissible venereal tumor] Mozos E, Mendez A, Gomez-Villamandos JC, Martin De Las Mulas J, Perez J.Vet Pathol. 1996 May;33(3):257-63.

ee also

*Devil facial tumour disease — a similarly transmissible "immortal cell" cancer in the Tasmanian Devil.
*HeLa cells — immortal cell line used in biomedical research