Tumor-Associated Macrophages are Correlated with Tamoxifen Resistance in the Postmenopausal Breast Cancer Patients

Tumor-associated macrophages (TAMs) have been correlated with increased angiogenesis and poor prognosis in breast cancer. However, the precise role of TAMs in tamoxifen resistance remains unclear. We used immunohistochemical method to examine the expression of epidermal growth factor receptor (EGFR) and CD163+ macrophages in 100 breast cancer tissues. The clinical and biological features of 100 patients were estrogen receptor (ER)-positive and human epidermal growth factor receptor 2(Her-2)-negative tumors. The tamoxifen resistant tissues (n = 48) were the surgical excision samples from patients who developed recurrence or metastasis at the time of adjuvant tamoxifen treatment. The tamoxifen resistant tissues were contrast to tamoxifen sensitive tissues (n = 52). Positive staining for EGFR and CD163+ macrophages were observed in 21 samples (43.8 %) and in 26 samples (54.2 %) respectively in tamoxifen resistance group, which were higher than that of tamoxifen sensitive group (P = 0.001 and P = 0.000279 respectively). Significant positive correlations were found between the expression of EGFR and CD163+ macrophages (r = 0.567, P < 0.01). CD163+ macrophages were positively correlated with tumor size, lymph node metastasis and obesity. Obesity was also related to tamoxifen resistance (P < 0.05). The patients with higher density of CD163+ macrophages infiltration suffered from shorter time to develop recurrence or metastasis (P < 0.05). TAMs may be associated with tamoxifen resistance. Further studies are needed to investigate the potential mechanism between TAMs and tamoxifen resistance.