Immunocytochemical characterization of primary cell culture in canine transmissible venereal tumor

Canine transmissible venereal tumor - From general to molecular characteristics: A review

Cancer is a group of complex diseases resulting from the accumulation of genetic and epigenetic changes affecting control and activity of several genes, especially those involved in cell differentiation and growth processes, leading to an abnormal proliferation. When the disease reaches an advanced stage, cancer can lead to metastasis in other organs. Interestingly, recent studies have shown that some types of cancer spread not only through the body, but also can be transmitted among individuals. Therefore, these cancers are known as transmissible tumors. Among the three types of transmissible tumors that occur in nature, the canine transmissible venereal tumor (CTVT) is known as the oldest cancer in the world, since it was originated from a single individual 11 000 years ago. The disease has a worldwide distribution, and its occurrence has been documented since 1810. The CTVT presents three types of cytomorphological classification: lymphocytoid type, mixed type, and plasmacytoid type, the latter being chemoresistant due to overexpression of the ABCB1 gene, and consequently increase of the P-glycoprotein. More knowledge about the epidemiology and evolution of CTVT may help to elucidate the pathway and form of the global spread of the disease.

Epidemiological study of canine transmissible venereal tumor (CTVT) in Brazil, 2000-2020

Canine transmissible venereal tumor (CTVT) is a contagious neoplasm, mainly transmitted through coitus. This round cell mesenchymal tumor is common in Brazil, often located in the genitalia although extragenital presentations may also occur, such as cutaneous, oral, and nasal forms. The objective of this study was to perform an epidemiological analysis of CTVT from published data in the recent academic literature to systematically demonstrate the distribution of CTVT in Brazil, identify the frequency of this neoplasm and its main diagnostic tests, and characterize its main clinical manifestations in Brazil. For such purpose, it was analyzed the scientific publications with cases of CTVT in Brazil, in English or Portuguese, published between 2000-2020. The CTVT was identified in 19 Brazilian states plus the Federal District, totaling 3,622 cases across the national territory, with the largest number of cases recorded in the Southeast region. The cytological exam was the most used for the diagnosis of CTVT (89.2 %), followed by histopathological (37.8 %) and immunohistochemistry (13.5 %)¹ . Predominant epidemiological aspects of CTVT identified in the study were: Mixed breed dogs (75.2 %), females (62.5 %), in adulthood (between 2 and 7 years) and dogs with free extra outdoor access (91.1 %). Genital presentation was the most frequent in the literature (86 %), followed by cutaneous (21.8 %), nasal (10 %), oral and lymph nodes presentations (10-5 %) and less frequent manifestations as ocular and anal/perianal (< 5 %). CTVT is a neoplasm widely distributed in Brazil, highly frequent and with several forms of clinical presentation, which can be underdiagnosed if there is no adequate knowledge of this tumor and its epidemiological characteristics. The extragenital manifestations of the neoplasm need further studies for its better characterization and more precise definition of its frequencies.

Evaluation of a Canine Transmissible Venereal Tumour Cell Line with Tumour Immunity Capacity but Without Tumorigenic Property

Introduction

Canine transmissible venereal tumour (CTVT) is a sexually transmitted tumour affecting dogs worldwide, imposing a financial burden on dog owners. A stable culture cell line in continuous passages for >18 months has only been achieved once. The present study investigated a stable CTVT cell line isolated from a bitch and its potential as a vaccine.

Material and Methods

A biopsy from a 2-year-old mongrel bitch with CTVT was obtained for histopathological confirmation and isolation of tumour cells. The isolated cells were cultured to passage 55 and characterised by flow cytometry, with karyotyping by GTG-banding and by PCR detection of myc S-2 and LINE AS1. The isolated CTVT cell line was also used as a preventive vaccine in a canine model.

Results

Histopathological analysis of the isolated tumour cells revealed typical CTVT characteristics. Constant proliferation and stable morphological characteristics were observed during culture. Phenotypic analysis determined the expression of HLA-DR⁺, CD5.1⁺, CD14⁺, CD45⁺, CD83⁺, CD163⁺, and Ly-6G-Ly-6C⁺. GTG-banding revealed a mean of 57 chromosomes in the karyotype with several complex chromosomal rearrangements. LINE-c-myc insertion in the isolated CTVT cell line at 550 bp was not detected. However, a 340-bp band was amplified. Isolated CTVT cell line inoculation at a concentration of 1×10⁸ did not induce tumour growth in bitches, nor did a challenge with primary CTVT cells.

Conclusion

The present study successfully identified and isolated a stable CTVT cell line that may be useful in CTVT prevention.