乳腺癌干细胞（BCSC）在乳腺癌治疗和疾病复发的治疗耐药性中发挥着关键作用。本研究旨在开发一种装载 pH 敏感脂质体的联合疗法，使用曲妥珠单抗敏感且耐药的人表皮生长因子受体 2 阳性 (HER2) 乳腺癌细胞模型杀死 BCSC 和 okbulk 癌细胞。在 HER2 细胞系 BT-474 和经过验证的曲妥珠单抗耐药细胞系 BT-474R 中，比较了全反式视黄酸、盐霉素和蟾毒灵单独使用或与阿霉素联合使用的抗 BCSC 效果和细胞毒性。选择最有效的抗 BCSC 剂并将其装入 pH 敏感的脂质体系统中。评估了脂质体组合对 BCSC 和大量癌细胞的影响。与 BT-474 相比，BT-474R 中乙醛脱氢酶阳性 BCSC 群体升高（3.9% vs. 23.1%）。蟾蜍灵是最有效的药物，可抑制 BCSC 的肿瘤发生约 50%，并且在 BT-474 和 BT-474R 细胞系中与多柔比星表现出强烈的协同作用。蟾蜍灵和阿霉素的脂质体组合显着减少了 BCSC 群体大小 85%，并抑制肿瘤发生和自我更新，尽管对迁移和侵袭力影响不大。在两种细胞系中，与单独使用任一制剂相比，脂质体组合也增强了针对大量癌细胞的细胞毒性（p<<0.001）。脂质体蟾蜍灵和阿霉素联合疗法可以有效地靶向 BCSC 和大量癌细胞，从而在曲妥珠单抗耐药的 HER2 乳腺癌中获得更好的结果。

Breast cancer stem cells (BCSCs) play a key role in therapeutic resistance in breast cancer treatments and disease recurrence. This study aimed to develop a combination therapy loaded with pH-sensitive liposomes to kill both BCSCs and the okbulk cancer cells using trastuzumab-sensitive and resistant human epidermal growth factor receptor 2 positive (HER2+) breast cancer cell models. The anti-BCSCs effect and cytotoxicity of all-trans retinoic acid, salinomycin, and bufalin alone or in combination with doxorubicin were compared in HER2+ cell line BT-474 and a validated trastuzumab-resistant cell line, BT-474R. The most potent anti-BCSC agent was selected and loaded into a pH-sensitive liposome system. The effects of the liposomal combination on BCSCs and bulk cancer cells were assessed. Compared with BT-474, the aldehyde dehydrogenase positive BCSC population was elevated in BT-474R (3.9 vs. 23.1%). Bufalin was the most potent agent and suppressed tumorigenesis of BCSCs by ∼50%, and showed strong synergism with doxorubicin in both BT-474 and BT-474R cell lines. The liposomal combination of bufalin and doxorubicin significantly reduced the BCSC population size by 85%, and inhibited both tumorigenesis and self-renewal, although it had little effect on the migration and invasiveness. The cytotoxicity against the bulk cancer cells was also enhanced by the liposomal combination than either formulation alone in both cell lines (p < 0.001). The liposomal bufalin and doxorubicin combination therapy may effectively target both BCSCs and bulk cancer cells for a better outcome in trastuzumab-resistant HER2+ breast cancer.