Shimauchi Atsushi, Iwama Eiji, Ibusuki Ritsu, Tsutsumi Hirono, Shibahara Daisuke, Otsubo Kohei, Yoneshima Yasuto, Tanaka Kentaro, Okamoto Isamu
Department of Respiratory Medicine, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
Department of Pulmonary Medicine, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan.
Br J Cancer. 2025 Jul 28. doi: 10.1038/s41416-025-03126-x.
HER2-targeted antibody-drug conjugates (ADCs) have shown marked efficacy for HER2 mutation-positive non-small cell lung cancer (NSCLC). The intracellular trafficking of mutant HER2 has remained to be fully elucidated, however.
HER2 dynamics were examined in cells expressing wild-type (WT) or mutant HER2 with the use of live cell imaging and an in situ proximity ligation assay. Proteins related to mutant HER2 trafficking were identified by liquid chromatography and tandem mass spectrometry.
HER2 internalization was enhanced in NSCLC cells expressing mutant HER2 compared with those expressing HER2(WT). Homodimers of HER2(WT) were localized mainly at the cell surface, whereas those of mutant HER2 were present mostly in the cytoplasm. Knockdown of EGFR or HER3 suppressed internalization of HER2(WT) but not that of mutant HER2. The enhanced internalization of mutant HER2 was mediated by clathrin-dependent endocytosis, as was reflected by increased binding of the ubiquitin ligase c-Cbl to mutant HER2 and its consequent ubiquitination, and was attenuated by treatment with zongertinib, a HER2-specific tyrosine kinase inhibitor.
Upregulation of HER2 phosphorylation promotes internalization of mutant HER2 mediated by clathrin-dependent endocytosis, likely contributing to the efficacy of HER2-targeted ADCs in NSCLC positive for HER2 mutations.
人表皮生长因子受体2（HER2）靶向抗体药物偶联物（ADC）已显示出对HER2突变阳性非小细胞肺癌（NSCLC）具有显著疗效。然而，突变型HER2的细胞内运输机制仍有待充分阐明。
利用活细胞成像和原位邻近连接分析，检测表达野生型（WT）或突变型HER2的细胞中HER2的动态变化。通过液相色谱和串联质谱鉴定与突变型HER2运输相关的蛋白质。
与表达HER2（WT）的非小细胞肺癌细胞相比，表达突变型HER2的细胞中HER2内化增强。HER2（WT）的同源二聚体主要定位于细胞表面，而突变型HER2的同源二聚体大多存在于细胞质中。表皮生长因子受体（EGFR）或HER3的敲低抑制了HER2（WT）的内化，但不影响突变型HER2的内化。突变型HER2内化增强是由网格蛋白依赖的内吞作用介导的，这表现为泛素连接酶c-Cbl与突变型HER2的结合增加及其随后的泛素化，并且用HER2特异性酪氨酸激酶抑制剂宗格替尼处理可使其减弱。
HER2磷酸化上调促进了网格蛋白依赖的内吞作用介导的突变型HER2内化，这可能有助于HER2靶向ADC对HER2突变阳性NSCLC的疗效。
