Myeloid-derived suppressor cells and associated events in urethane-induced lung cancer

OBJECTIVES Myeloid-derived suppressor cells contribute to the immunosuppressive microenvironment during tumor development and limit the efficacy of cancer immunotherapy. Identifying myeloid-derived suppressor cells and associated factors is the first step in creating strategies to reverse the suppressive effects of these cells on the immune system. METHODS To induce lung cancer, we administered 2 doses of urethane to BALB/c mice and observed these animals for 120 days. After this period, we evaluated the percentage of myeloid-derived suppressor cells in the blood, lung and bone marrow. The expression of alpha-smooth muscle actin, transforming growth factor-β, Toll-like receptor 2, Toll-like receptor 4, and interleukin-6 was also determined in the lung tissue. RESULTS Myeloid-derived suppressor cells were increased in all evaluated tissues after lung cancer development in association with increased Toll-like receptor 4 expression and decreased interleukin-6 expression in the lung. We observed alpha-smooth muscle actin and transforming growth factor-β expression in lung nodules. CONCLUSIONS We believe that the early diagnosis of cancer through determining the blood levels of myeloid-derived suppressor cells followed by the depletion of these cells should be further investigated as a possible approach for cancer treatment.