Department of Gastrointestinal Surgery, Changhai Hospital, Second Military Medical University, Shanghai, 200433, P. R. China.
Department of Biological Medicines & Shanghai Engineering Research Center of Immunotherapeutics, Fudan University School of Pharmacy, Shanghai, 201203, P. R. China.
Cell Death Dis. 2021 Mar 17;12(4):288. doi: 10.1038/s41419-020-03349-1.
Trastuzumab emtansine (T-DM1), an antibody-drug conjugate consisted of the HER2-targeted monoclonal antibody trastuzumab and the tubulin inhibitor emtansine, has shown potent therapeutic value in HER2-positive breast cancer (BC). However, a clinical trial indicated that T-DM1 exerts a limited effect on HER2-positive gastric cancer (GC), but the underlying mechanism is inconclusive. Our research attempted to reveal the probable mechanism and role of autophagy in T-DM1-treated HER2-positive GC. In this study, our results showed that T-DM1 induced apoptosis and exhibited potent therapeutic efficacy in HER2-positive GC cells. In addition, autophagosomes were observed by transmission electron microscopy. Autophagy was markedly activated and exhibited the three characterized gradations of autophagic flux, consisting of the formation of autophagosomes, the fusion of autophagosomes with lysosomes, and the deterioration of autophagosomes in autolysosomes. More importantly, autophagic inhibition by the suppressors 3-methyladenine (3-MA) and LY294002 significantly potentiated cytotoxicity and apoptosis in HER2-positive GC cells in vitro, while the combined use of LY294002 and T-DM1 elicited potent anti-GC efficacy in vivo. In mechanistic experiments, immunoblot analysis indicated the downregulated levels of Akt, mTOR, and P70S6K and confocal microscopy analysis clearly showed that autophagic inhibition promoted the fusion of T-DM1 molecules with lysosomes in GC cells. In conclusion, our research demonstrated that T-DM1 induced apoptosis as well as cytoprotective autophagy, and autophagic inhibition could potentiate the antitumor effect of T-DM1 on HER2-positive GC. Furthermore, autophagic inhibition might increase the fusion of T-DM1 with lysosomes, which might accelerate the release of the cytotoxic molecule emtansine from the T-DM1 conjugate. These findings highlight a promising therapeutic strategy that combines T-DM1 with an autophagy inhibitor to treat HER-positive GC more efficiently.
曲妥珠单抗-美坦新偶联物（T-DM1）由 HER2 靶向单克隆抗体曲妥珠单抗和微管抑制剂美坦新组成，在 HER2 阳性乳腺癌（BC）中显示出强大的治疗价值。然而，一项临床试验表明，T-DM1 对 HER2 阳性胃癌（GC）的作用有限，但潜在机制尚不清楚。我们的研究试图揭示自噬在 T-DM1 治疗 HER2 阳性 GC 中的可能机制和作用。在这项研究中，我们的结果表明，T-DM1 诱导凋亡，并在 HER2 阳性 GC 细胞中表现出强大的治疗功效。此外，通过透射电子显微镜观察到自噬体。自噬明显被激活，并表现出自噬流的三个特征性阶段，包括自噬体的形成、自噬体与溶酶体的融合以及自噬溶酶体中自噬体的降解。更重要的是，自噬抑制剂 3-甲基腺嘌呤（3-MA）和 LY294002 在体外显著增强了 HER2 阳性 GC 细胞的细胞毒性和凋亡，而 LY294002 和 T-DM1 的联合使用在体内产生了强大的抗 GC 疗效。在机制实验中，免疫印迹分析表明 Akt、mTOR 和 P70S6K 的下调水平，共聚焦显微镜分析清楚地表明，自噬抑制促进了 GC 细胞中 T-DM1 分子与溶酶体的融合。总之，我们的研究表明，T-DM1 诱导凋亡和细胞保护自噬，自噬抑制可以增强 T-DM1 对 HER2 阳性 GC 的抗肿瘤作用。此外，自噬抑制可能会增加 T-DM1 与溶酶体的融合，从而加速 T-DM1 偶联物中细胞毒性分子美坦新的释放。这些发现强调了一种有前途的治疗策略，即联合使用 T-DM1 和自噬抑制剂更有效地治疗 HER 阳性 GC。
