CD16+ monocytes in breast cancer patients: expanded by monocyte chemoattractant protein-1 and may be useful for early diagnosis

Human peripheral blood monocytes are a heterogeneous population, including CD14⁺CD16^‐‘classical’ monocytes and CD14⁺CD16⁺‘proinflammatory’ monocytes. CD16⁺ monocytes are expanded in various inflammatory conditions. However, little is known about the CD14⁺CD16⁺ monocytes in patients with breast cancer. We detected CD14⁺CD16⁺ monocytes in 96 patients with breast cancer and 54 control subjects using flow cytometry. Receiver‐operating characteristic (ROC) curve analysis was used to determine the feasibility of CD14⁺CD16⁺ monocytes as an indicator for diagnosis of breast cancer. We found that the frequency of CD14⁺CD16⁺ monocytes showed a significantly greater increase in breast cancer patients than in controls (16·96% versus 10·84%, P < 0·0001). The area under the ROC curve for CD14⁺CD16⁺ monocytes was 0·805 [95% confidence interval (95% CI): 0·714–0·877, P = 0·0001]. Furthermore, the levels of CD16⁺ monocytes were significantly negatively associated with the tumour size and pathological staging. In vitro, we showed that CD14⁺CD16⁺ monocytes were expanded significantly when the purified CD14⁺ monocytes were exposed to Michigan Cancer Foundation (MCF)‐7 cells‐conditioned medium (MCF‐CM) or, separately, to monocyte chemotactic protein 1 (MCP‐1). Neutralizing antibodies against MCP‐1 inhibited the expansion of CD14⁺CD16⁺ monocytes by MCF‐CM. Collectively, our findings indicated that MCP‐1 can expand CD14⁺CD16⁺ monocytes in patients with breast cancer. Furthermore, the CD14⁺CD16⁺ monocyte may be a useful indicator in early diagnosis of breast cancer.