Adoptive cell transfer (ACT) immunotherapy is considered the most promising treatment of cancer; however it is still limited by the use of short-lived and exhausted T cells. Recently, IL-17 producing CD4+ T lymphocytes (Th17 cells) have been shown to be superior in eradication of melanoma in mouse compared to Th1 cells. We propose to determine the expanding ex vivo protocol of Th17 cells from domestic dog in order to support comparative oncology research and improve the ACT-based immunotherapy for humans. We hypothesised that pharmacological manipulation of signaling pathways of canine Th17 cells will enhance their antitumor activity and increase the efficacy of tumor immunotherapy. We plan to evaluate the results on the tumor infiltrating lymphocytes from melanoma-bearing dogs (patients of Veterinary Clinic). The outcomes of the project will provide the rationale for designing next-generation clinical trials for human cancer patients and facilitate development of cell-based drugs.