MafB silencing in macrophages does not influence the initiation and growth of lung cancer induced by urethane.

An increased number of tumor-associated macrophages (TAMs) that exhibit the M2 macrophage phenotype is related to poorer prognosis in cancer patients. MafB is a transcription factor regulating the differentiation of macrophages. However, involvement of MafB for the development of TAMs is unknown. This study was designed to investigate the role of MafB in a murine urethane-induced lung cancer model. Urethane was injected intraperitoneally into wild-type and dominant-negative MafB transgenic mice. Twenty-four weeks later, mice were sacrificed and their lungs removed for pathological analysis. The numbers and mean areas of lung cancer were evaluated. In addition, the numbers of Mac-3-positive macrophages were evaluated in each tumor. The numbers and mean areas of lung cancer induced by urethane administration were not significantly different between wild-type and dominant- negative MafB transgenic mice. The numbers of TAMs in lung cancer tissue were not significantly different between the two groups. MafB silencing using dominant-negative MafB did not influence the initiation and growth of lung cancer in mice exposed to urethane. These data suggest that MafB may not be related to the development of TAMs.