Tasmanian devil facial tumor disease (DFTD) and canine transmissible venereal tumor (CTVT) are the only known naturally occurring clonally transmissible cancers. These cancers are transmitted by the physical transfer of viable tumor cells that can be transplanted across histocompatibility barriers into unrelated hosts. Despite their common etiology, DFTD and CTVT have evolved independently and have unique life histories and host adaptations. DFTD is a recently emerged aggressive facial tumor that is threatening the Tasmanian devil with extinction. CTVT is a sexually transmitted tumor of dogs that has a worldwide distribution and that probably arose thousands of years ago. By contrasting the biology, molecular genetics and immunology of these two unusual cancers, I highlight the common and unique features of clonally transmissible cancers, and discuss the implications of clonally transmissible cancers for host-pathogen evolution.

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Clonally transmissible cancers in dogs and Tasmanian devils.

Publisher Summary The canine transmissible venereal tumor (TVT) is the only tumor known to be transmitted in nature by the transplantation of cells. Under natural conditions, the TVT is transmitted by coitus and experimentally, the tumor can be induced by the inoculation of living tumor cells to immunocompetent allogeneic dogs. Evidence that the tumor is transmitted by cells is derived from cytogenetic and immunological studies. Cytogenetic studies show that TVT from different geographical origins is characterized by extensive and characteristic chromosomal aberrations. With the characterization of the banding patterns of normal dog chromosomes, the background information for comparative banding pattern analysis of TVT chromosomes is now available. These studies may enable investigators to determine whether this unique tumor has a common origin or it arose repeatedly in the domestic dog. The results of immunological studies also suggest that the TVT is transmitted by the transplantation of cells. Investigations of the immune response against the TVT have clearly demonstrated that the tumor is antigenic in the dog and that immunological mechanisms are involved in the induction of the spontaneous regressions of this neoplasm.

The canine transmissible venereal tumor: a unique result of tumor progression.

Canine transmissible venereal tumour (CTVT) is the only known naturally occurring tumour that can be transplanted as an allograft across major histocompatibility (MHC) barriers within the same species, and even to other members of the canine family, such as foxes, coyotes and wolves. The progression of this tumour is unique in that, it follows a predictable growth pattern. In natural and experimental cases, the growth pattern includes progressive growth phase, static phase and regression phase, and this is followed by transplantation immunity in immunocompetent adults, while metastasis occurs in puppies and immunosuppressed dogs. Because of the uniqueness of CTVT transmission and progression, experimental investigations of various aspects of the biology of CTVT have been used to provide clues to the immunobiology of both animal and human tumours. This review examines the current state of knowledge of the aspects of the cytogenetic origin, immunophenotype, immunobiology and immunotherapy of CTVT.

https://www.tandfonline.com/doi/pdf/10.1080/01652176.2003.9695151

Canine transmissible venereal tumour: cytogenetic origin, immunophenotype, and immunobiology. A review.

The canine transmissible venereal tumour (CTVT) is a contagious cancer that is naturally transmitted between dogs by the allogeneic transfer of living cancer cells during coitus. CTVT first arose several thousand years ago and has been reported in dog populations worldwide; however, its precise distribution patterns and prevalence remain unclear. We analysed historical literature and obtained CTVT prevalence information from 645 veterinarians and animal health workers in 109 countries in order to estimate CTVT’s former and current global distribution and prevalence. This analysis confirmed that CTVT is endemic in at least 90 countries worldwide across all inhabited continents. CTVT is estimated to be present at a prevalence of one percent or more in dogs in at least 13 countries in South and Central America as well as in at least 11 countries in Africa and 8 countries in Asia. In the United States and Australia, CTVT was reported to be endemic only in remote indigenous communities. Comparison of current and historical reports of CTVT indicated that its prevalence has declined in Northern Europe, possibly due to changes in dog control laws during the nineteenth and twentieth centuries. Analysis of factors influencing CTVT prevalence showed that presence of free-roaming dogs was associated with increased CTVT prevalence, while dog spaying and neutering were associated with reduced CTVT prevalence. Our analysis indicated no gender bias for CTVT and we found no evidence that animals with CTVT frequently harbour concurrent infectious diseases. Vincristine was widely reported to be the most effective therapy for CTVT. Our results provide a survey of the current global distribution of CTVT, confirming that CTVT is endemic in at least 90 countries worldwide. Additionally, our analysis highlights factors that continue to modify CTVT’s prevalence around the world and implicates free-roaming dogs as a reservoir for the disease. Our analysis also documents the disappearance of the disease from the United Kingdom during the twentieth century, which appears to have been an unintentional result of the introduction of dog control policies.

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The changing global distribution and prevalence of canine transmissible venereal tumour

To determine the diagnostic and/or prognostic importance of chromosomal aberrations identified in dogs with malignant (non-Hodgkin's) lymphoma, clinical stages for 61 dogs with lymphosarcoma were determined, the lymph node(s) were histopathologically graded, and the malignant tissue lymphocytes were karyotyped. The results from life table survival curve analysis demonstrated that first remission length and survival time were significantly longer in 15 of 61 (25%) dogs that had a trisomy of chromosome 13 as the primary chromosomal aberration than in those dogs (46/61, 75%) with other primary chromosomal aberrations (P 0.05). Multivariate analysis did not identify a significant correlation between the prognostic groups or within the various prognostic subsets (P > 0.05). The pathogenesis of canine and human non-Hodgkin's lymphoma, as observed cytogenetically, differs.

https://journals.sagepub.com/doi/pdf/10.1177/030098589403100504

Diagnostic and Prognostic Importance of Chromosomal Aberrations Identified in 61 Dogs with Lymphosarcoma

Pathological and cytogenetic observations on the naturally occurring canine venereal tumour in Jamaica (Sticker's tumour)

M S Ragbeer

Papers

Pathological and cytogenetic observations on the naturally occurring canine venereal tumour in Jamaica (Sticker's tumour).