Dang Cao Thuy Linh, Kawanishi Kunio, Hashimoto Sachie, Hengphasatporn Kowit, Nagai-Okatani Chiaki, Kimura Takaharu, Abdelaziz Mohammed, Shiratani Rie, Poullikkas Thanasis, Azmi Nuriza Ulul, Baba Masaki, Okita Yukari, Watanabe Yukihide, Bando Hiroko, Yamazaki Satoshi, Shigeta Yasuteru, Kuno Atsushi, Kato Mitsuyasu
Department of Experimental Pathology, Institute of Medicine, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan.
Department of Anatomy, Showa Medical University School of Medicine, Shinagawa-ku, Tokyo 142-8555, Japan.
Proc Natl Acad Sci U S A. 2025 Sep 9;122(36):e2503081122. doi: 10.1073/pnas.2503081122. Epub 2025 Sep 2.
Metastasis remains the leading cause of cancer-related mortality, driven by complex interactions within the tumor microenvironment (TME). Tumor-associated macrophages (TAMs) play a pivotal role in metastatic progression, yet their molecular diversity and upstream regulators remain poorly defined. Glycoprotein nonmetastatic melanoma protein B (GPNMB), overexpressed in subsets of tumors including triple-negative breast cancer (TNBC), is implicated in epithelial-mesenchymal transition (EMT) and cancer stemness. Recent single-cell RNA sequencing (scRNA-seq) identified GPNMB as a marker of immunosuppressive TAMs associated with poor prognosis, but its mechanistic role in TNBC has remained unclear. Coculturing monocytic cells with three-dimensional TNBC spheres induced GPNMB TAMs expressing sialic acid-binding immunoglobulin-like lectin 9 (Siglec-9). Tumor-expressed GPNMB promotes monocyte-to-TAM polarization by inducing secondary GPNMB expression in monocytes, establishing a feed-forward amplification loop. GPNMB knockdown in TNBC cells inhibited immunosuppressive TAM subsets, including Siglec-9 and EMT-associated populations, as determined by deconvolution of bulk RNA-seq data using a custom TAM signature matrix derived from publicly available TNBC scRNA-seq datasets. TNBC-derived GPNMB carried α2,3-sialylation, whereas macrophage-derived GPNMB carried α2,6-sialylation, enabling differential Siglec-9 recognition. Elevated GPNMB and Siglec-9 correlated with poor prognosis in TNBCcohorts. Importantly, dual inhibition of Siglec-E (murine Siglec-9 ortholog) and PD-1 reduced tumor stemness, suppressed IL-6-dependent EMT, and limited lung metastasis in vivo. The GPNMB-Siglec-9 axis thus represents a critical glyco-immunological checkpoint driving TAM-mediated metastasis, providing a promising therapeutic target in TNBC.
转移仍然是癌症相关死亡的主要原因，这是由肿瘤微环境（TME）内的复杂相互作用驱动的。肿瘤相关巨噬细胞（TAM）在转移进展中起关键作用，但其分子多样性和上游调节因子仍不清楚。糖蛋白非转移性黑色素瘤蛋白B（GPNMB）在包括三阴性乳腺癌（TNBC）在内的部分肿瘤中过表达，与上皮-间质转化（EMT）和癌症干性有关。最近的单细胞RNA测序（scRNA-seq）将GPNMB鉴定为与预后不良相关的免疫抑制性TAM的标志物，但其在TNBC中的机制作用仍不清楚。将单核细胞与三维TNBC球体共培养可诱导表达唾液酸结合免疫球蛋白样凝集素9（Siglec-9）的GPNMB TAM。肿瘤表达的GPNMB通过诱导单核细胞中二级GPNMB表达促进单核细胞向TAM极化，建立前馈放大环。使用源自公开可用的TNBC scRNA-seq数据集的定制TAM特征矩阵对批量RNA-seq数据进行反卷积分析，结果表明TNBC细胞中GPNMB的敲低抑制了免疫抑制性TAM亚群，包括Siglec-9和与EMT相关的群体。TNBC来源的GPNMB携带α2,3-唾液酸化，而巨噬细胞来源的GPNMB携带α2,6-唾液酸化，从而实现对Siglec-9的差异性识别。在TNBC队列中，GPNMB和Siglec-9升高与预后不良相关。重要的是，对Siglec-E（小鼠Siglec-9直系同源物）和PD-1的双重抑制降低了肿瘤干性，抑制了IL-6依赖性EMT，并在体内限制了肺转移。因此，GPNMB-Siglec-9轴代表了驱动TAM介导的转移的关键糖免疫检查点，为TNBC提供了一个有前景的治疗靶点。
