CAA 衍生的 IL-6 通过激活 STAT3 诱导 M2 巨噬细胞极化。

BACKGROUND: Tumor-associated macrophages (TAMs) are the most abundant types of immune cells in the tumor microenvironment (TME) of breast cancer (BC). TAMs usually exhibit an M2 phenotype and promote tumor progression by facilitating immunosuppression. This study aimed to investigate the effect of CAA-derived IL-6 on macrophage polarization in promoting BC progression. METHODS: Human BC samples and adipocytes co-cultured with 4T1 BC cells were employed to explore the properties of CAAs. The co-implantation of adipocytes and 4T1 cells in mouse tumor-bearing model and tail vein pulmonary metastasis model were constructed to investigate the impact of CAAs on BC malignant progression in vivo. The functional assays, qRT-PCR, western blotting assay and ELISA assay were employed to explore the effect of CAA-derived IL-6 on macrophage polarization and programmed cell death protein ligand 1 (PD-L1) expression. RESULTS: CAAs were located at the invasive front of BC and possessed a de-differentiated fibroblast phenotype. CAAs facilitated the malignant behaviors of 4T1 cells in vitro, and promoted 4T1 tumor growth and pulmonary metastasis in vivo. The IHC staining of both human BC specimens and xenograft and the in vitro experiment indicated that CAAs could enhance infiltration of M2 macrophages in the TME of 4T1 BC. Furthermore, CAA-educated macrophages could enhance malignant behaviors of 4T1 cells in vitro. More importantly, CAAs could secret abundant IL-6 and thus induce M2 macrophage polarization by activating STAT3. In addition, CAAs could upregulate PD-L1 expression in macrophages. CONCLUSIONS: Our study revealed that CAAs and CAA-educated macrophages enhanced the malignant behaviors of BC. Specifically, CAA-derived IL-6 induced migration and M2 polarization of macrophages via activation STAT3 and promoted macrophage PD-L1 expression, thereby leading to BC progression.

背景：肿瘤相关巨噬细胞（TAMs）是乳腺癌（BC）肿瘤微环境（TME）中最丰富的免疫细胞类型。TAMs 通常表现出 M2 表型，并通过促进免疫抑制来促进肿瘤进展。本研究旨在探讨 CAA 衍生的 IL-6 对促进 BC 进展的巨噬细胞极化的影响。

方法：采用人 BC 样本和与 4T1 BC 细胞共培养的脂肪细胞来研究 CAA 的特性。构建脂肪细胞和 4T1 细胞共植入小鼠荷瘤模型和尾静脉肺转移模型，以研究 CAA 对体内 BC 恶性进展的影响。采用功能测定、qRT-PCR、western blot 分析和 ELISA 分析来探讨 CAA 衍生的 IL-6 对巨噬细胞极化和程序性细胞死亡配体 1（PD-L1）表达的影响。

结果：CAA 位于 BC 的浸润前沿，具有去分化成纤维细胞表型。CAA 在体外促进了 4T1 细胞的恶性行为，并在体内促进了 4T1 肿瘤的生长和肺转移。人 BC 标本和异种移植的免疫组化染色以及体外实验表明，CAA 可以增强 4T1 BC 肿瘤微环境中 M2 巨噬细胞的浸润。此外，CAA 教育的巨噬细胞可以增强 4T1 细胞在体外的恶性行为。更重要的是，CAA 可以分泌大量的 IL-6，通过激活 STAT3 诱导 M2 巨噬细胞极化。此外，CAA 可以上调巨噬细胞中 PD-L1 的表达。

结论：本研究揭示了 CAA 和 CAA 教育的巨噬细胞增强了 BC 的恶性行为。具体而言，CAA 衍生的 IL-6 通过激活 STAT3 诱导巨噬细胞迁移和 M2 极化，并促进巨噬细胞 PD-L1 表达，从而导致 BC 进展。