Tumor Extracellular Vesicles lncOSLMT Drives Lung Inflammatory Premetastatic Niche Formation in Osteosarcoma via m6A-Dependent hnRNPA2B1/COX-2 Axis.

Tumor-derived extracellular vesicles (EVs) play critical roles in premetastatic niche (PMN) formation. Here, we demonstrated that EVs from highly metastatic osteosarcoma cell lines preferentially localized to lung fibroblasts and induce inflammatory PMN formation. High-throughput profiling of EVs-derived long noncoding RNAs (lncRNAs) identified lncOSLMT as a candidate enriched in EVs and markedly upregulated in patient tumor and serum, with elevated levels correlating with poor prognosis. Mechanistically, in EVs, lncOSLMT directly bound the RNA-binding protein hnRNPA2B1. Following internalization by recipient lung fibroblasts, hnRNPA2B1 bound to N6-methyladenosine (m6A) -modified sites in the 3'UTR of PTGS2 mRNA, leading to transcript stabilization and increased COX-2 expression. For therapeutic intervention, we developed lactoferrin-resveratrol (LF-RES) nanoparticles, which loaded siRNA against lncOSLMT. Intravenous administration of LF-RES-siRNA in mice reduced EVs-induced lung inflammation and suppressed lung metastasis. Combination with EP2/EP4 antagonists produced enhanced anti-metastatic effects. These findings establish EVs-derived lncOSLMT as a key regulator of inflammatory PMN formation in the lung and highlight the potential of LF-RES-siRNA nanoparticles as a targeted anti-metastatic therapy in osteosarcoma. Overall design: Nude mice were injected with 143B-derived EVs or MNNG/HOS-derived EVs via the tail vein, followed by RNA sequencing of lung tissues.

肿瘤来源细胞外囊泡（extracellular vesicles, EVs）在转移前微环境（premetastatic niche, PMN）形成过程中发挥关键调控作用。本研究证实，高转移性骨肉瘤细胞系分泌的细胞外囊泡可优先靶向肺成纤维细胞，并诱导炎性转移前微环境形成。通过对细胞外囊泡来源长链非编码RNA（long noncoding RNAs, lncRNAs）开展高通量表达谱分析，我们筛选得到富集于细胞外囊泡的候选分子lncOSLMT；该分子在患者肿瘤组织与血清中显著上调，且其高表达与不良预后显著相关。机制研究显示，在细胞外囊泡中，lncOSLMT可直接结合RNA结合蛋白异质性细胞核核糖蛋白A2B1（heterogeneous nuclear ribonucleoprotein A2B1, hnRNPA2B1）；当细胞外囊泡被受体肺成纤维细胞内化后，hnRNPA2B1可结合PTGS2 mRNA 3'非翻译区的N6-甲基腺嘌呤（N6-methyladenosine, m6A）修饰位点，进而稳定该转录本并提升环氧合酶2（cyclooxygenase-2, COX-2）的表达水平。在治疗干预环节，我们构建了负载靶向lncOSLMT的小干扰RNA（small interfering RNA, siRNA）的乳铁蛋白-白藜芦醇（lactoferrin-resveratrol, LF-RES）纳米颗粒。小鼠尾静脉注射该LF-RES-siRNA纳米颗粒后，可显著抑制细胞外囊泡诱导的肺部炎症反应，并阻断肺转移进程；联合使用EP2/EP4受体拮抗剂可进一步增强抗转移效果。本研究证实，细胞外囊泡来源的lncOSLMT是肺部炎性转移前微环境形成的关键调控因子，同时揭示了LF-RES-siRNA纳米颗粒作为骨肉瘤靶向抗转移治疗手段的应用潜力。整体实验设计：通过尾静脉向裸小鼠注射143B细胞来源的细胞外囊泡或MNNG/HOS细胞来源的细胞外囊泡，随后对小鼠肺组织进行RNA测序。