CD163-positive cancer cells are potentially associated with high malignant potential in clear cell renal cell carcinoma

CD163 is preferentially expressed by monocyte/macrophages; however, recent studies using immunohistochemistry (IHC) have reported that some cancer cells also express CD163. In the present IHC study, we investigated CD163 staining of cancer cells and macrophages in clear cell renal cell carcinoma (ccRCC) tissues and determined the relationship between cancer cell CD163 expression and clinical prognosis in patients with ccRCC. IHC for CD163 was performed in ccRCC tissues from 103 patients. CD163-positive cancer cells were detected in 35% of the patients (36/103); however, the positive signals on cancer cells were significantly lower than those on macrophages. CD163-positive cancer cells were preferentially detected in patients with high T classification, and females, and were significantly associated with shortened progression-free survival and a lower overall survival ratio. Notably, a high intensity of CD163-positive macrophage infiltration was detected in the CD163-positive cancer cell-high tumor areas. Although CD163 mRNA was detected in cultured macrophages, no CD163 mRNA was detected in two cultured RCC cell lines. The detailed mechanism by which a positive signal is detected on cancer cells has not been clarified. Detection of the CD163 antigen on cancer cells might be a useful marker for evaluating the clinical course of patients with ccRCC.