There are significant differences in pathology, etiology, clinical features, and treatment options between small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). However, the differences of macrophage distribution and its associated function between SCLC and NSCLC are not fully investigated. Through methods of flow cytometry and cytometric bead array, we examined the levels of various subtypes of macrophages, monocytes, and regulatory T cells (Tregs) as well as interleukin (IL)-10 in bronchoalveolar lavage fluid (BALF) of patients with SCLC or NSCLC. Our study showed that the frequency of CD14+, CD206+CD14+ and IL-10+CD206+CD14+M2-like macrophages were significantly increased, with simultaneously elevated IL-10 in BALF of SCLC patients, as compared to those in BALF of NSCLC patients. Furthermore, the increased frequency of IL-10+CD206+CD14+M2-like macrophages and elevated level of IL-10 in BALF of SCLC patients were positively correlated with advanced tumor stage, but negatively correlated with their survival time. On the other hand, the level of supernatant IL-10 and frequency of IL-10+CD206+CD14+M2-like macrophages in SCLC patients were positively correlated. The frequency of above mentioned macrophages was also positively correlated with that of Foxp3+CD25+CD4+Tregs. Compared to NSCLC patients, the level of circulating IL-10+CD206+CD14+M2-like monocytes in SCLC patients were significantly increased after chemotherapy. Overall, increased IL-10+CD206+CD14+M2-like macrophages were an important feature of SCLC, rather than NSCLC, and it is associated with development of SCLC.
Keywords: IL-10; Macrophage; Monocytes; Regulatory T cells; Small cell lung cancer.