Department of Oncology, Hebei Medical University, Shijiazhuang, 050017, Hebei, China.
Department of Medical Oncology, Bethune International Peace Hospital, Shijiazhuang, 050082, Hebei, China.
Gastric Cancer. 2024 May;27(3):495-505. doi: 10.1007/s10120-024-01478-6. Epub 2024 Feb 22.
HER2-targeted therapies have improved the outcomes of HER2-positive gastric cancer (GC), yet resistance remains a challenge. We sought to explore the effects of reversible and irreversible HER2 tyrosine kinase inhibitors (TKIs) alone or in combination with the HER2-targeting antibody drug conjugate trastuzumab deruxtecan (T-Dxd).
The effects of HER2-TKIs on HER2 and downstream signaling were evaluated via Western blotting. Proteasomal inhibitors and co-immunoprecipitation assays were performed to explore the role of proteasomal degradation in HER2 expression modulation, and immunofluorescence assays were employed to explore mechanisms of HER2 internalization. The synergistic potential of the irreversible HER2-TKI pyrotinib in combination with T-Dxd was validated using growth and viability assays in anti-HER2-positive GC cell cultures and tumor growth and immunohistochemical staining assays in a mouse xenograft model.
Our study revealed that reversible HER2-TKIs elevated HER2 protein levels, whereas irreversible HER2-TKIs decreased them. Pyrotinib triggered HER2 degradation within the proteasome by promoting ubiquitination and dissociation from HSP90. Furthermore, pyrotinib substantially induced HER2 internalization, which led to improved cellular uptake of T-Dxd. The increased T-Dxd uptake was accompanied by greater efficacy in suppressing the growth of GC cells and enhanced anti-tumor effects in an animal model.
In summary, our research reveals the molecular mechanisms of irreversible HER2-TKIs in regulating HER2 protein expression by promoting HER2 internalization. These findings advance our comprehension of targeted therapy for GC and provide a promising therapeutic combination strategy with enhanced efficacy against HER2-positive GC.
HER2 靶向治疗改善了 HER2 阳性胃癌（GC）的预后，但耐药仍然是一个挑战。我们试图探讨可逆和不可逆 HER2 酪氨酸激酶抑制剂（TKI）单独或联合 HER2 靶向抗体药物偶联物曲妥珠单抗 deruxtecan（T-Dxd）的作用。
通过 Western blot 评估 HER2-TKI 对 HER2 和下游信号的影响。进行蛋白酶体抑制剂和共免疫沉淀测定，以探讨蛋白酶体降解在 HER2 表达调控中的作用，并用免疫荧光测定探索 HER2 内化的机制。使用生长和活力测定在抗 HER2 阳性 GC 细胞培养物中以及在荷瘤小鼠模型中的肿瘤生长和免疫组织化学染色测定中验证不可逆 HER2-TKI 吡咯替尼与 T-Dxd 的联合增效潜力。
我们的研究表明，可逆 HER2-TKI 升高了 HER2 蛋白水平，而不可逆 HER2-TKI 则降低了其水平。吡咯替尼通过促进泛素化和与 HSP90 的解离，在蛋白酶体中触发 HER2 降解。此外，吡咯替尼可显著诱导 HER2 内化，从而改善 T-Dxd 的细胞摄取。增加的 T-Dxd 摄取伴随着 GC 细胞生长抑制作用的增强和动物模型中抗肿瘤作用的增强。
总之，我们的研究揭示了不可逆 HER2-TKI 通过促进 HER2 内化来调节 HER2 蛋白表达的分子机制。这些发现增进了我们对 GC 靶向治疗的理解，并提供了一种有前途的治疗联合策略，可增强对 HER2 阳性 GC 的疗效。
