Combination of Suicide and Cytokine Gene Therapies as Surgery Adjuvant for Canine Mammary Carcinoma

The incidence of canine mammary carcinoma varies with age, breed, and spay status, being among the main tumors appearing in intact female dogs. Thirty-six canine mammary carcinoma patients received injections of canine interferon-β (cIFN-β) and HSV-thymidine kinase/ganciclovir (HSV-tk/GCV) carrying lipoplexes, into the tumor bed, immediately after surgery. Next, they started periodic subcutaneous injections of lipoplexes carrying a human granulocyte-macrophage colony stimulating factor and interleukin-2 mixed with allogeneic mammary carcinoma extracts. This combined strategy was safe and well tolerated. In addition, only two out of 26 patients treated with complete surgery developed a local relapse, and 0 out of 29 stage II and III patients displayed distant metastases, suggesting both local and systemic antitumor activities. The most encouraging result was the long survival times: 22 > 1 year (where 13 > 2 and 4 > 3 years), while maintaining a good quality of life. The preliminary results in five patients presenting with local disease, an additional HSV-tk/GCV plus cIFN-β gene treatment induced local antitumor activity, evidenced by four objective responses (one complete, three partial) and one stable disease. This successful outcome supports further studies to validate this approach not only for canine veterinary patients, but also for translation to human patients.