Zhang Yan, Du Weiwei, Chen Zhaoliang, Xiang Cheng
Department of Oncology, The First Hospital of Shijiazhuang City, Shijiazhuang 050010, China.
Department of Oncology, Henan Province Hospital of TCM, Zhengzhou 450002, China.
Exp Cell Res. 2017 Oct 15;359(2):449-457. doi: 10.1016/j.yexcr.2017.08.028. Epub 2017 Aug 19.
Tumor-associated macrophages (TAMs) polarization represents a key regulatory process of tumor progression. However, the underlying mechanisms are unclear. This study aimed to investigate the relationship between secreted phosphoprotein 1 (SPP1) and TAMs in lung adenocarcinoma cells. THP-1 monocytes were differentiated into macrophages using PMA. PMA-treated THP-1 cells were co-cultured with human A549 cells culture supernatant. SPP1 expression in TAMs isolated from lung adenocarcinoma tissues and PMA-treated THP-1 cells were measured. Macrophage polarization was identified by flow cytometric analysis. Cell migration and apoptosis were assessed by Transwell migration assays and flow cytometric analysis, respectively. SPP1 is highly expressed in tumor tissues and TAMs isolated from patients with an advanced TNM stage, and also in PMA-treated THP-1 cells. Co-culture with A549 cells strongly induced SPP-1 expression as well as M2 polarization of THP-1 cells, but it had little effect on short hairpin SPP1 (shSPP1)-transfected THP-1 cells. Interestingly, programmed death ligand 1 (PD-L1), a critical regulator of M2 polarization, was downregulated in SPP1 knockdown THP-1 cells. Inhibition of PD-L1 induced a greater decline of the M2 markers IL-10 and Arg-1 but an increase in the M1 markers IL-12 and TNF-α. In addition, SPP1 knockdown in THP-1 cells can mitigate migration but promote apoptosis of A549 cells, and PD-L1 inhibition can further enhance this effect. THP-1 cells co-cultured with A549 cells attenuated CD4 T-cell activation, whereas SPP1 inhibition restored T-cell activation. These results highlight the importance of SPP1 in mediating macrophage polarization and lung cancer evasion, suggesting a potential therapeutic target for lung cancer.
肿瘤相关巨噬细胞（TAMs）极化是肿瘤进展的关键调控过程。然而，其潜在机制尚不清楚。本研究旨在探讨分泌磷蛋白1（SPP1）与肺腺癌细胞中TAMs之间的关系。使用佛波酯（PMA）将THP-1单核细胞分化为巨噬细胞。将经PMA处理的THP-1细胞与人A549细胞培养上清液共培养。检测从肺腺癌组织中分离的TAMs以及经PMA处理的THP-1细胞中SPP1的表达。通过流式细胞术分析鉴定巨噬细胞极化。分别通过Transwell迁移试验和流式细胞术分析评估细胞迁移和凋亡。SPP1在肿瘤组织以及从晚期TNM分期患者中分离的TAMs中高表达，在经PMA处理的THP-1细胞中也高表达。与A549细胞共培养强烈诱导THP-1细胞SPP-1表达以及M2极化，但对短发夹SPP1（shSPP1）转染的THP-1细胞影响不大。有趣的是，M2极化的关键调节因子程序性死亡配体1（PD-L1）在SPP1敲低的THP-1细胞中下调。抑制PD-L1导致M2标志物白细胞介素-10（IL-10）和精氨酸酶-1（Arg-1）的更大程度下降，但M1标志物白细胞介素-12（IL-12）和肿瘤坏死因子-α（TNF-α）增加。此外，THP-1细胞中SPP1敲低可减轻A549细胞的迁移但促进其凋亡，而抑制PD-L1可进一步增强这种作用。与A549细胞共培养的THP-1细胞减弱了CD4 T细胞活化，而抑制SPP1可恢复T细胞活化。这些结果突出了SPP1在介导巨噬细胞极化和肺癌免疫逃逸中的重要性，提示其可能是肺癌的一个潜在治疗靶点。
