GK-1 peptide reduces tumor growth, decreases metastatic burden, and increases survival in a murine breast cancer model D. Torres-García a , A. Pérez-Torres b , K. Manoutcharian a , U. Orbe b , R. Servín-Blanco a , G. Fragoso a , E. Sciutto a,⇑ a Departamento de Inmunología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Av. Universidad 3000, 04510 Mexico City, Mexico b Departamento de Biología Celular y Tisular, Facultad de Medicina, Universidad Nacional Autónoma de México, Av. Universidad 3000, 04510 Mexico City, Mexico article info Article history: Received 7 June 2017 Received in revised form 10 August 2017 Accepted 19 August 2017 Available online xxxx Keywords: Breast cancer Metastasis Immunotherapy Primary tumor GK-1 abstract GK-1 is a parasite-derived peptide adjuvant of 18 amino acid-length that enhances T-cell function and increases survival in B16-F10 melanoma tumor-bearing mice. This study was designed to evaluate in vivo the antitumor efficacy of GK-1 on 4T1 mouse mammary carcinoma. BALB/c mice with palpable primary tumors were weekly intravenously injected three times with saline solution or three different concentrations (10, 50, or 100 lg per mouse) of GK-1. GK-1 significantly increased lifespan (p < 0.0001) and reduced the primary tumor weight (p = 0.014) and volume (p < 0.0001) with respect to control mice, with no statistically significant differences among GK-1 doses. At the primary tumor, we found increased necrotic areas associated with a reduction in tumor mass, as well as an increase in the antitumor cytokine IL-12. Especially encouraging is the ability of GK-1 to reduce the number of lung metastasis (p = 0.006) disregarding the dose used. The participation of IL-6 in metas- tasis development and the decreased levels of CCL-2, CCL-3, TNF-a, CXCL-9, GM-CSF, and b-FGF found in lungs of GK-1-treated mice is discussed. Our study supports the effectiveness of GK-1 as an antineoplastic agent that merits further exploration in combination with other therapeutic approaches in future translational studies. Ó 2017 Elsevier Ltd. All rights reserved. 1. Introduction Breast cancer (BC) is the most common form of cancer that affects women worldwide [1]. In the last decades, the mortality rate of BC patients has been declining due to improvements in early diagnosis and more effective treatments [2]. Unfortunately, some BC forms are resistant to conventional therapies, a fact that points to the need for more effective therapies. Many efforts have been thriving in recent years to enhance tumor immunity and control cancer progression. However, the development of effective cancer immunotherapies has been ham- pered by a high epitope mutation rate derived from the antigenic variability of cancer cells, which promotes escape from immune surveillance, immune tolerance and immune escape, an immuno- suppressive tumor microenvironment, and the generation of new tumor cells from cancer stem cells [3]. However, several preclinical and clinical studies have demon- strated the potential of immunotherapy to improve the clinical outcome for cancer patients through vaccination, adoptive T cell transfer, cytokine therapy, and other approaches. Some examples of these therapies are trastuzumab [4], lapatinib [5,6], and everoli- mus [7], whose targets are cancer stem cells. Nowadays, perhaps the most encouraging results have come from immunomodulatory therapies like IFN-a, IL-2, IL-15, IL-21, anti-CD25, anti-PD-1, and anti-CTLA-4, among others [8–11]. Unfortunately, these drugs may have side effects such as diarrhea, pruritus, constipation, fati- gue, skin eruption dermatitis, and follicular eruption, [11–14] as well as an increased risk of autoimmune diseases like enterocolitis, lupus, nephritis, arthritis, uveitis, and hepatitis [15–20]. In spite of these considerations, the pivotal role of the host immune response in the natural history of breast cancer offers a target for new treatment approaches. In particular, the disrupted immunity promoted by BC itself offers a therapeutic opportunity to deal with the tumor by reversing those immunity conditions. Thus, the goal of this study was to improve the immunity against http://dx.doi.org/10.1016/j.vaccine.2017.08.060 0264-410X/Ó 2017 Elsevier Ltd. All rights reserved. Abbreviations: BC, breast cancer; aa, amino acid; SS, saline solution; H&E, hematoxylin and eosin; SD, standard deviation; MAM, metastasis-associated macrophages; MDSC, myeloid-derived suppressor cells. ⇑ Corresponding author. E-mail address: edda@unam.mx (E. Sciutto). Vaccine xxx (2017) xxx–xxx Contents lists available at ScienceDirect Vaccine journal homepage: www.elsevier.com/locate/vaccine Please cite this article in press as: Torres-García D et al. GK-1 peptide reduces tumor growth, decreases metastatic burden, and increases survival in a mur- ine breast cancer model. Vaccine (2017), http://dx.doi.org/10.1016/j.vaccine.2017.08.060