Background. Tissue-resident macrophages can be educated to tumor-associated macrophages (TAMs) by the tumor microenvironment and many types of macrophages express erythropoietic receptor (EPOR); However, little is known about the expression of EPOR on TAMs and the identity of EPOR⁺ TAMs in osteosarcoma lung metastasis has thus far remained elusive. Methods. EPOR-eGFPcre mice were used to determine the expression of EPOR on lung tissue-resident macrophages. Flow cytometry, RT-PCR, and Western blot were examined to define the identity of EPOR⁺ TAMs in 106 osteosarcoma lung metastasis specimens. Moreover, the clinicopathologic factors and prognosis of patients with CD163⁺EPOR⁺ macrophages were compared. Results. We found that a subpopulation of mouse lung tissue-resident macrophages express EPOR and EPO enhances the proliferation of EPOR⁺ macrophages in mouse lung. A subpopulation of CD163⁺ macrophages expresses EPOR in human osteosarcoma lung metastasis specimens. CD163⁺EPOR⁺TAMs increase 2.5 times in human osteosarcoma lung metastasis tissues; CD206, CD163, and PD1, which are known to have a significant role in TAM function had high expression in CD163⁺EPOR⁺ TAMs compared with CD163⁺EPOR^- TAMs. Furthermore, CD163⁺EPOR⁺ TAMs had higher M2 marker and cytokine expression in osteosarcoma tissues compared with para-osteosarcoma tissues. EPO enhanced the expression of M2 cytokines in primary CD163⁺EPOR⁺ TAMs. Importantly, the percentage of CD163⁺EPOR⁺ TAMs had a positive linear association with malignant phenotypes as well as poor disease-free survival and overall survival time. Conclusions. We have characterized TAMs expressing EPOR and CD163⁺EPOR⁺ macrophages as TAMs in osteosarcoma lung metastasis patients, which are highly associated with tumor aggressiveness.

中文翻译：

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EPOR+ 肿瘤相关巨噬细胞在人骨肉瘤肺转移中的鉴定和功能分析。

背景。肿瘤微环境可以将组织驻留巨噬细胞培养成肿瘤相关巨噬细胞（TAM），并且许多类型的巨噬细胞表达红细胞生成受体（EPOR）；然而，关于 EPOR 在 TAM 上的表达知之甚少，而 EPOR ⁺ TAM 在骨肉瘤肺转移中的身份迄今仍难以捉摸。方法。EPOR-eGFPcre 小鼠用于确定肺组织驻留巨噬细胞上 EPOR 的表达。检查流式细胞术、RT-​​PCR 和蛋白质印迹以确定106 例骨肉瘤肺转移标本中 EPOR ^{+ TAM 的身份。此外，CD163 +} EPOR ⁺患者的临床病理因素和预后比较巨噬细胞。结果。我们发现小鼠肺组织中的巨噬细胞亚群表达 EPOR，EPO 增强了小鼠肺中 EPOR ⁺巨噬细胞的增殖。^{CD163 +}巨噬细胞亚群在人骨肉瘤肺转移标本中表达 EPOR。CD163 ⁺ EPOR ⁺ TAMs 在人骨肉瘤肺转移组织中增加 2.5 倍；^{与 CD163 +} EPOR ^- TAM相比，已知在 TAM 功能中起重要作用的 CD206、CD163 和 PD1 在 CD163 ⁺ EPOR ⁺ TAM 中具有高表达。此外，CD163 ⁺ EPOR ⁺与骨肉瘤组织相比，TAM 在骨肉瘤组织中具有更高的 M2 标志物和细胞因子表达。EPO 增强了原代 CD163 ⁺ EPOR ⁺ TAM 中 M2 细胞因子的表达。重要的是，CD163 ⁺ EPOR ⁺ TAM 的百分比与恶性表型以及较差的无病生存期和总生存期呈正线性相关。结论。我们已经将表达 EPOR 和 CD163 ⁺ EPOR ⁺巨噬细胞的 TAM 表征为骨肉瘤肺转移患者中的 TAM，这与肿瘤侵袭性高度相关。