目的 研究肿瘤类器官培养体系下，ADC药物维迪西妥单抗（RC-48）对不同HER-2表达水平乳腺癌细胞的抑制作用。 方法 在肿瘤类器官培养体系下，对乳腺癌HER-2低表达细胞系MCF-7（Luminal A型）、高表达细胞系BT-474（HER-2型）以及二者不同混合比例组进行培养；对形成的类器官进行组织学表征，并通过免疫组化和免疫荧光技术检测HER-2在MCF-7与BT-474类器官中的表达水平及空间分布；使用维迪西妥单抗（RC-48）、迪西妥单抗（Disitamab）和甲基澳瑞他汀E（MMAE）分别处理MCF-7和BT-474类器官以及对不同比例MCF-7和BT-474混合培养及患者来源的乳腺癌类器官进行RC-48的药敏试验，通过3D-Glo法评估药物敏感性。 结果 在肿瘤类器官培养体系下，免疫组化及免疫荧光检测显示，HER-2主要定位于细胞膜，BT-474类器官中HER-2表达为强阳性，MCF-7类器官则呈现低表达状态；相较于MCF-7类器官，RC48-ADC对BT-474类器官表现出更显著的抑制效应（IC₅₀：109.7 μg/mL vs. 2.792 μg/mL）；共培养模型进一步验证了RC-48的旁观者效应，HER-2阳性细胞与阴性细胞的比例显著影响药物杀伤效果。此外，RC-48处理后，不同HER-2表达水平的乳腺癌类器官中HER-2的表达量均呈下降趋势。 结论 肿瘤类器官模型能有效反映靶向药物的敏感性和旁观者效应。RC-48在类器官模型中对HER-2高表达乳腺癌细胞具有显著抑制作用，并通过旁观者效应增强杀伤效应，同时可下调HER-2表达，显示出针对HER-2相关乳腺癌的治疗潜力。

Objective The present study was designed to explore the inhibitory effects of the ADC drug Disitamab Vedotin （RC-48） on breast cancer cells with different HER-2 expression levels by utilizing a tumor organoid culture system. Methods Within the framework of the tumor organoid culture system， the breast cancer cell lines MCF-7 （characterized by low HER-2 expression， Luminal A subtype） and BT-474 （exhibiting high HER-2 expression， HER-2 positive subtype） were cultured independently and in various mixed ratios. The histological characteristics， as well as the expression levels and distribution of HER-2 in MCF-7 and BT-474 organoids， were analyzed via immunohistochemistry and immunofluorescence techniques. MCF-7 and BT-474 organoids were separately treated with Vedotin （RC-48）， Disitamab， and Monomethyl auristatin E （MMAE）. Additionally， a drug sensitivity test of Disitamab Vedotin （RC-48） was carried out on mixed MCF-7 and BT-474 cell ratios and on patient-derived breast cancer organoids， with the assessment conducted using the 3D-Glo method. Results In the tumor organoid culture system， immunohistochemistry and immunofluorescence analyses demonstrated that HER-2 was predominantly localized in the cell membrane. Specifically， BT-474 organoids exhibited robust HER-2 expression， while MCF-7 organoids displayed relatively low expression levels. When compared with MCF-7 organoids， RC48-ADC exerted a more pronounced inhibitory effect on BT-474 organoids， with IC₅₀ values of 109.7 μg/mL and 2.792 μg/mL， respectively. The co-culture model further confirmed the bystander effect of RC-48， revealing that the ratio of HER-2-positive to HER-2-negative cells significantly influenced drug efficacy. Additionally， treatment with RC-48 led to a reduction in HER-2 expression in breast cancer organoids with diverse HER-2 expression levels. Conclusions The tumor organoid model can accurately mirror drug sensitivity and bystander effects. Within this model， RC-48 effectively inhibited HER-2 highly-expressing breast cancer cells， augmented the killing effect through the bystander mechanism， and downregulated HER-2 expression， thereby suggesting its potential for targeting HER2-associated breast cancer.