三阴性乳腺癌(TNBC)由于细胞标志物缺乏作为药物靶点，具有高度侵袭性和不良预后。α9-烟碱乙酰胆碱受体(nAChR)在TNBC中广泛表达；因此，它是TNBC检测和治疗的有价值的生物标志物。在本研究中，我们利用热力学稳定的三路交叉(3WJ)RNA包装(pRNA)作为核心构建了RNA纳米颗粒，其中α9-nAChR RNA适配体作为靶向配体，反-miR-21作为治疗模块。我们比较了这两种RNA纳米颗粒的构型，发现3WJ-B-α9-nAChR-适配体荧光RNA纳米颗粒(3WJ-B-α9-apt-Alexa)与3WJ-C-α9-nAChR相比在TNBC细胞中对α9-nAChR具有更好的特异性。此外，3WJ-B-α9-apt-Alexa与3WJ荧光RNA纳米颗粒(3WJ-Alexa)相比，在系统注射小鼠后更有效地结合到TNBC患者来源的异种移植瘤(PDX)肿瘤，并且在健康器官中几乎没有积累。此外，携带反-miR-21的3WJ-B-α9-nAChR-适配体RNA纳米颗粒(3WJ-B-α9-apt-anti-miR-21)通过降低miR-21基因表达并上调磷酸酯酶和Tensin同源物(PTEN)和程序化细胞死亡4(PDCD4)蛋白，显著抑制TNBC-PDX肿瘤的生长和诱导细胞凋亡。此外，在治疗小鼠的毒性检查中未发现病理变化。总之，本研究建立的3WJ-B-α9-nAChR-适配体RNA纳米颗粒能够有效运输治疗性反-miR-21，表明其作为新型TNBC治疗的潜力。© 2023作者。

Triple-negative breast cancer (TNBC) is highly aggressive with a poor prognosis because of a lack of cell markers as drug targets. α9-Nicotinic acetylcholine receptor (nAChR) is expressed abundantly in TNBC; thus, it is a valuable biomarker for TNBC detection and treatment. In this study, we utilized thermodynamically stable three-way junction (3WJ) packaging RNA (pRNA) as the core to construct RNA nanoparticles with an α9-nAChR RNA aptamer as a targeting ligand and an anti-microRNA-21 (miR-21) as a therapeutic module. We compared the configuration of the two RNA nanoparticles and found that 3WJ-B-α9-nAChR-aptamer fluorescent RNA nanoparticles (3WJ-B-α9-apt-Alexa) exhibited better specificity for α9-nAChR in TNBC cells compared with 3WJ-C-α9-nAChR. Furthermore, 3WJ-B-α9-apt-Alexa bound more efficiently to TNBC patient-derived xenograft (PDX) tumors than 3WJ fluorescent RNA nanoparticles (3WJ-Alexa) with little or no accumulation in healthy organs after systemic injection in mice. Moreover, 3WJ-B-α9-nAChR-aptamer RNA nanoparticles carrying anti-miR-21 (3WJ-B-α9-apt-anti-miR-21) significantly suppressed TNBC-PDX tumor growth and induced cell apoptosis because of reduced miR-21 gene expression and upregulated the phosphatase and tensin homolog (PTEN) and programmed cell death 4 (PDCD4) proteins. In addition, no pathological changes were detected upon toxicity examination of treated mice. In conclusion, the 3WJ-B-α9-nAChR-aptamer RNA nanoparticles established in this study efficiently deliver therapeutic anti-miR-21, indicating their potential as a novel TNBC therapy.© 2023 The Author(s).