Katayoon Nofouzi - Department of Pathobiology, Faculty of Veterinary Medicine, University of Tabriz, Tabriz, Iran
Parsa Almasi - Department of Pathobiology, Faculty of Veterinary Medicine, University of Tabriz, Tabriz, Iran
Ali Asghar Fakhri-Demeshgheieh - Department of Pathobiology, Faculty of Veterinary Medicine, University of Tabriz, Tabriz, Iran
Monireh Khordadmehr - Department of Pathobiology, Faculty of Veterinary Medicine, University of Tabriz, Tabriz, Iran
Behzad Baradaran - Immunology Research Center, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran
Milad Asadi - Immunology Research Center, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran
Parvin Sarbakhsh - Department of Statics and Epidemiology, Faculty of Health Sciences, Tabriz University of Medical Sciences, Tabriz, Iran
Gholamreza Hamidian - Department of Basic Sciences, Faculty of Veterinary Medicine, University of Tabriz, Tabriz, Iran

Breast cancer (BC) is a significant cause of global mortality in women. This study was aimed to evaluate the immune-activation of malignant BC via the administration of attenuated Mycobacterium obuense. For this purpose, an in vivo model was developed with BALB/c mice. Mice were injected with ۲.۰۰ × ۱۰۶ ۴T۱ cells with breast tumor cell line. Forty-two mice were equally divided into control as well as low dose (۰.۲۰ mg ۱۰۰ µL-۱) and high dose (۰.۵۰ mg ۱۰۰ µL-۱) groups of M. obuense to investigate gene expression in the antitumor effects of M. obuense. In one group, paclitaxel was administrated as a choice drug in BC treatment. Antitumor manners were characterized by cytotoxicity against tumor target cells, size of the tumor and the expression of some BC metastatic genes together with pathology. The MTT assay demonstrated that different concentrations of both low and a high doses of bacteria did present no cytotoxicity effect on ۴T۱ cells. According to our findings, M. obuense significantly repressed tumor growth. M. obuense downregulated the expression of collagen type I alpha ۱ (COLIA۱), cFos, alkaline phosphatase (ALP), claudin ۳ (cldn۳), and conversely, activated transcription factor ۴ (ATF۴) and Twist related protein-۱ (Twist۱). All these alternations induced a decrease in the migratory and invasive capabilities of BC. The result of pathology was indicative of tumor regression in the paclitaxel and HK- M. obuense -recipient group. Thus, it seems most likely that M. obuense might impinge upon cell growth and metastatic behavior of malignant cells exerting anti-tumor activity in BC.

Breast cancer, Gene expression, Immunotherapy, metastatic behavior, Mycobacterium obuense