Predominance of M2-polarized macrophages in bladder cancer affects angiogenesis, tumor grade and invasiveness.

Tumor-associated macrophages (TAMs) often assume an immunoregulatory M2 phenotype. Thus, the aim of the present study was to clarify the correlation of vascularity and TAMs, in particular the M2 phenotype in the stroma and tumor areas, with the clinical and pathological outcomes of patients with bladder cancer. The TAM counts and microvessel counts (MVCs) were determined immunohistochemically in 21 patients with bladder cancer. The number of infiltrating TAMs was measured using immunohistochemistry with anti-cluster of differentiation (CD)68 and anti-CD163 antibodies, to identify a macrophage lineage marker and an M2-polarized-specific cell surface receptor, respectively. CD68+ and CD163+ macrophages were evaluated in the stroma and tumor areas, and areas with a high density of infiltrating cell spots were counted. MVCs were determined using immunohistochemistry with anti-CD34 antibodies. The results revealed that the higher ratio of CD163+/CD68+ macrophages in the stroma, tumor and total tumor tissues were correlated with a higher stage and grade (P<0.05). In addition, the low ratio of CD68+/CD34+ microvessels was correlated with a higher stage (P<0.05). There was also a positive correlation between TAMs and MVC (r2=0.25; P<0.05). These results suggest that the TAM polarized M2 phenotype affects microvessels, pathological outcome, tumor grade and invasiveness.