Tumour-associated macrophages correlate with microvascular bed extension in colorectal cancer patients

Tumour-associated macrophages (TAMs) represent pivotal components of tumour microenvironment promoting angiogenesis, tumour progression and invasion. In colorectal cancer (CRC), there are no conclusive data about the role of TAMs in angiogenesis-mediated tumour progression. In this study, we aimed to evaluate a correlation between TAMs, TAM immunostained area (TAMIA) microvascular density (MVD), endothelial area (EA) and cancer cells positive to VEGF-A (CCP-VEGF-A) in primary tumour tissue of locally advanced CRC patients undergone to radical surgery. A series of 76 patients with CRC were selected and evaluated by immunohistochemistry and image analysis. An anti-CD68 antibody was employed to assess TAMs and TAMIA expression, an anti-CD34 antibody was utilized to detect MVD and EA expression, whereas an anti-VEGF-A antibody was used to detect CCP-VEGF-A; then, tumour sections were evaluated by image analysis methods. The mean ± S.D. of TAMs, MVD and CCP-VEGF-A was 65.58 ± 21.14, 28.53 ± 7.75 and 63% ± 37%, respectively; the mean ± S.D. of TAMIA and EA was 438.37 ± 124.14μ(2) and 186.73 ± 67.22μ(2) , respectively. A significant correlation was found between TAMs, TAMIA, MVD and EA each other (r ranging from 0.69 to 0.84; P ranging from 0.000 to 0.004). The high level of expression of TAMs and TAMIA in tumour tissue and the significant correlation with both MVD and EA illustrate that TAMs could represent a marker that plays an important role in promoting angiogenesis-mediated CRC. In this context, novel agents killing TAMs might be evaluated in clinical trials as a new anti-angiogenic approach.