Prognostic Significance of CD169+ Lymph Node Sinus Macrophages in Patients with Malignant Melanoma

CD169 (sialoadhesin) is a sialic acid receptor that is specifically expressed on macrophages, including lymph node sinus macrophages. Animal studies suggest that CD169(+) macrophages in lymph nodes have properties in preventing cancers. In order to determine the significance of CD169(+) macrophages in patients with malignant melanoma, we evaluated tissue samples from 93 patients to investigate CD169 expression in regional lymph nodes (RLN) and determine the relationship of this expression with overall survival and various clinicopathologic factors. Higher densities of CD169(+) cells were significantly associated with longer overall survival (P = 0.001). A multivariate analysis showed that the density of CD169(+) cells was an independent prognostic factor, with higher densities correlating with higher density of CD8(+) cytotoxic T cells within tumor sites. High CD169 expression in macrophages could be stimulated by IFNα in vitro, and in RLNs, IFNα-producing macrophages and CD303(+) plasmacytoid dendritic cells were identified surrounding CD169(+) macrophages. These data suggest that IFNα-stimulated CD169(+) macrophages in RLNs are closely involved in T-cell-mediated antitumor immunity and may be a useful marker for assessing the clinical prognosis and monitoring antitumor immunity in patients with malignant melanoma.