Canine transmissible venereal tumor (CTVT) serves as a valuable model for studying tumor-immune system interactions due to its unique progression and regression phases. This study investigated the roles of IL-6, TGF-β1, and CD8+ T cells in CTVT progression and regression phases, evaluating their association with therapeutic response and cytological malignancy criteria. Samples from 25 untreated dogs were analyzed via cytology, confirmed via histopathology. Immunohistochemistry for IL-6 and TGF- β1, and CD8+ via flow cytometry. IL-6 and TGF-β1 expression was detected in 100% of tumor samples, with cytoplasmic localization scoring an intensity in 75% of the histological section showed positive staining. Interestingly, IL-6 was exclusively expressed by tumor cells in certain cases. CD8+ T cell density in tumors demonstrated a significant negative correlation (ρ=-0.65, P<0.05) with mitotic activity, suggesting an inverse relationship between cell proliferation and immune response. Therapeutic response was established at the 4th week of treatment for most cases, although some required up to ten weeks to achieve complete remission. Resistant cases were included in a second-line chemotherapy protocol with doxorubicin, reflecting the variability in tumor behavior. These findings propose a novel hypothesis regarding IL-6 production by neoplastic cells as a mechanism to suppress antigen presentation and immune activation. Further exploration of IL-6’s dual role in tumor progression and regression may reveal potential therapeutic targets for enhancing immune response in CTVT and other cancers.

To Cite This Article: Dinau FC, González-Zambrano CM, Jimenez JJ, Florez LMM, Oliveir R, Rocha NS, 2025. Exploring the dynamics of IL-6, TGF-β1, and CD8+ T cells in the canine transmissible venereal tumor: new perspectives. Pak Vet J. http://dx.doi.org/10.29261/pakvetj/2025.009