Abstract

Background: Immunotherapy, during which the immune system of the patient is manipulated to act against tumors has been among the most successful methods in the treatment of breast cancer, a leading cause of mortality among women worldwide. Objectives: To investigate the immunotherapeutic efficacy of Lactobacillus casei lysate as an adjuvant in combination with a heated-4T1 mammary carcinoma cell lysate in a model of breast cancer. Methods: After ethics committee approval of all animal procedures, a murine model of breast cancer was induced in BALB/c mice using 4T1 cells. These mice were immunized with a combination of lysates of heated 4T1 cells and L. casei. Subsequent changes in tumor size and weight, and the production of TNF-alpha, IL-2, IL-12, IL-17, and IL13 were measured. Lung weights were measured as an indicator of metastasis to other organs. Results: The tumor size and weight in mice immunized with the combined vaccine were significantly reduced compared with controls. The combined immunotherapy altered the pattern of cytokine production to the advantage of antitumor immunity, and was significantly more potent than immunization with heated-4T1-cell lysate or L. casei lysate alone. Conclusions: Coadministration of L. casei lysate enhanced the immunotherapeutic efficacy of the heated-4T1-cell lysate as a source of tumor-associated antigens. L. casei can potentially be used as an adjuvant combined with sources of tumor antigens in the treatment of cancers, and as a safe alternative to the current adjuvants that cause greater irritation to hosts. Further studies are required to clarify the mechanisms underlying these effects.