canine transmissible venereal tumor

In male dogs, the tumor affects the penis and foreskin. In female dogs, it affects the vulva. Rarely, the mouth or nose are affected.{{cite book|last=Morrison|first=Wallace B.|title=Cancer in Dogs and Cats|edition=1st|publisher=Williams and Wilkins|year=1998|isbn=978-0-683-06105-5}} The tumor often has a cauliflower-like appearance. Signs of genital TVT include a discharge from the prepuce and in some cases urinary retention caused by blockage of the urethra. Signs of a nasal TVT include nasal fistulae, nosebleeds and other nasal discharge, facial swelling, and enlargement of the submandibular lymph nodes.{{cite journal|vauthors=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, Series A|volume=48|issue=7|pages=391–400|year=2001|pmid=11599677|doi=10.1046/j.1439-0442.2001.00361.x}}

Canine transmissible venereal tumors are histiocytic tumors that may be transmitted among dogs through coitus, licking, biting and sniffing tumor affected areas. The concept that the tumor is naturally transmissible as an allograft came from three important observations. First, CTVTs can only be experimentally induced by transplanting living tumor cells, and not by killed cells or cell filtrates. Second, the tumor karyotype is aneuploid but has characteristic marker chromosomes in all tumors collected in different geographic regions. Third, a long interspersed nuclear element (LINE-1) insertion near the c-myc gene has been found in all tumors examined so far and can be used as a diagnostic marker to confirm that a tumor is a CTVT.{{cite journal|last1=Dingli|first1=D|last2=Nowak|first2=MA|year=2006|title=Cancer biology: infectious tumour cells|journal=Nature|volume=443|issue=7107|pages=35–6|doi=10.1038/443035a|pmid=16957717|pmc=2711443|bibcode=2006Natur.443...35D}}

Canine transmissible venereal tumors are most commonly seen in sexually active dogs in tropical, subtropical and temperate climates where there are large populations of stray dogs, but little is known about the details of transmission.{{cite journal|pmid=16901777|year=2006|last1=Vonholdt|first1=B. M|title=The singular history of a canine transmissible tumor|journal=Cell|volume=126|issue=3|pages=445–7|last2=Ostrander|first2=E. A|doi=10.1016/j.cell.2006.07.016|doi-access=free}} The disease is spread when dogs mate, and can even be transmitted to other canine species, such as foxes and coyotes.{{cite journal|vauthors=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|doi=10.1080/01652176.2003.9695151|doi-access=free}} Spontaneous regression of the tumor can occur, probably due to a response from the immune system.{{cite journal|vauthors=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|doi-access=free}} CTVT undergoes a predictable cycle: an initial growth phase of four to six months (P phase), a stable phase, and a regression phase (R phase),{{cite journal|vauthors=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 less than 5 percent of cases),{{cite web|title=Canine Transmissible Venereal Tumor: Introduction|website=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 occurs to regional lymph nodes,{{cn|date=May 2024}} but can also be seen in the skin, brain, eye, liver, spleen, testicle, rectum and muscle.{{cite journal|vauthors=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|doi=10.5326/15473317-34-6-463}} A biopsy is necessary for diagnosis.

The success of this single cell lineage, believed to be the longest continually propagated cell lineage in the world, can be attributed to the tumor's mode of transmission in a specific host system. Although direct contact is generally not a highly efficient mode of transfer, CTVTs take advantage of the popular sire effect of domestic dogs. A single male can produce dozens of litters over his lifetime, allowing the tumor to affect many more females than it could if a monogamous species were the host. Understanding the epidemiology of CTVTs could provide insights for populations that may experience CTVT exposure and information about disease prevalence.{{cn|date=January 2023}}

The CTVT cells have fewer chromosomes than normal dog cells. Dog cells normally have 78 chromosomes, while the cancer 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|vauthors=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|doi=10.2460/javma.2000.216.1557|pmid=10825939|doi-access=free}}

All tumor cells of this type of cancer share extremely similar genetic code, often if not always unrelated to the DNA of their host. In addition to the aforementioned c-myc insertion, a few other potential driver mutations have been identified.{{cite journal |last1=Belov |first1=Katherine |last2=Jones |first2=Elizabeth |last3=Cheng |first3=Yuanyuan |title=The origin, dynamics, and molecular evolution of transmissible cancers |journal=Advances in Genomics and Genetics |date=September 2015 |pages=317 |doi=10.2147/AGG.S61298|doi-access=free }}

The tumor, when treated with the chemotherapy drug vincristine, regresses as the host immune system is activated. CCL5 may play an important role in the immune response.{{cite journal|last1=Frampton|first1=D|last2=Schwenzer|first2=H|last3=Marino|first3=G|last4=Butcher|first4=LM|last5=Pollara|first5=G|last6=Kriston-Vizi|first6=J|last7=Venturini|first7=C|last8=Austin|first8=R|last9=de Castro|first9=KF|last10=Ketteler|first10=R|last11=Chain|first11=B|last12=Goldstein|first12=RA|last13=Weiss|first13=RA|last14=Beck|first14=S|last15=Fassati|first15=A|title=Molecular Signatures of Regression of the Canine Transmissible Venereal Tumor.|journal=Cancer Cell|date=9 April 2018|volume=33|issue=4|pages=620–633.e6|doi=10.1016/j.ccell.2018.03.003|pmid=29634949|url=http://discovery.ucl.ac.uk/10046739/1/PIIS1535610818300710.pdf|pmc=5896242}}

Surgery may be difficult due to the location of these tumors. Surgery alone often leads to recurrence. Chemotherapy is very effective for TVTs. The prognosis for complete remission with chemotherapy is excellent.{{cite book|last1=Ettinger|first1=Stephen J.|last2=Feldman|first2=Edward C.|title=Textbook of Veterinary Internal Medicine|edition=4th|publisher=W.B. Saunders Company|year=1995|isbn=978-0-7216-6795-9}} The most common chemotherapy agents used are vincristine, vinblastine, and doxorubicin. Use of autohaemotherapy in treatment of TVTs also showed promising results in many cases.{{Cite journal |last1=Arif |first1=S. A. |last2=Das |first2=T. |last3=Deka |first3=D. |last4=Kachari |first4=J. |last5=Barman |first5=U. |last6=Changkija |first6=B. |last7=Patgiri |first7=D. |date=2023-10-28 |title=Management of canine transmissible venereal tumour using autohaemotherapy: A vpromising approach |url=https://www.ijah.in/upload/snippet/31(172-22)-SC.pdf |journal=Indian Journal of Animal Health |volume=Online |doi=10.36062/ijah.2023.17222}} Radiotherapy may be required if chemotherapy does not work.

{{Reflist}}

• [https://veterinarypartner.vin.com/default.aspx?pid=19239&id=4952049 Transmissible Venereal Tumor] from The Pet Health Library
• [https://www.newscientist.com/article/dn9713-riddle-of-infectious-dog-cancer-solved/ Riddle of infectious dog cancer solved] at New Scientist
• [https://www.sciencedaily.com/releases/2006/08/060811075902.htm Contagious Cancer In Dogs Confirmed; Origins Traced To Wolves Centuries Ago] (2006)
• [https://www.nature.com/articles/news060807-13 Dog Cancer Traced Back to Wolf Roots] from Nature News

Transmissible venereal tumor

Category:Types of animal cancers

Category:Clonally transmissible cancers

Category:Sexually transmitted diseases and infections