M2 macrophages reduce the radiosensitivity of head and neck cancer by releasing HB­EGF.

ABSTRACT

The aim of the present study was to examine the potential role of human heparin­binding epidermal growth factor (HB­EGF) secreted by M2 macrophages in the development of radioresistance in head and neck squamous cell carcinoma (HNSCC). Immunohistochemistry was used to detect radiosensitivity in human papilloma virus (HPV)­positive and HPV­negative HNSCC tissues and immunohistochemical staining with specific antibodies for macrophage surface markers was used to assess the infiltration of M1 and M2 macrophages in HPV­positive and ­negative HNSCC tissues. The expression of HB­EGF in HPV­positive and ­negative HNSCC tissues was determined by multi­cytokine detection in order to determine the relationship between HB­EGF and radiosensitivity. M1 and M2 macrophages were co­cultured with the HNSCC cell line CAL27 and treated with HB­EGF and its neutralizing antibodies to assess radiation sensitivity. Finally, the major DNA double­strand break repair pathways required for the activation of HB­EGF and promotion of epidermal growth factor receptor (EGFR) were identified. The results revealed that radiosensitivity was higher in HPV­positive HNSCC compared with HPV­negative. There was a higher infiltration of M2 macrophages in HPV­negative HNSCC, which were revealed as the main source of HB­EGF secretion. Furthermore, it was determined that overexpression of HB­EGF induced radioresistance in HPV­negative HNSCC. HB­EGF promoted the activation of the non­homologous end­joining pathway by activating EGFR. To the best of our knowledge, this is the first study to demonstrate the association between HB­EGF and radiosensitivity in HNSCC. These results indicated that the secretion of HB­EGF by M2 macrophages could induce radioresistance of HPV­negative HNSCC.