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Published on: June 18, 2013
Enhanced HER2 internalization by clathrin-dependent endocytosis in non-small cell lung cancer positive for HER2
Atsushi Shimauchi1, Eiji Iwama2, Ritsu Ibusuki1
1Department of Respiratory Medicine, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
Background:
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.
Methods:
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.
Results:
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.
Conclusions:
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.
Insights
Enhanced HER2 (human epidermal growth factor receptor 2) internalization in non-small cell lung cancer (NSCLC) with mutations is driven by clathrin-dependent endocytosis, explaining antibody-drug conjugate efficacy.
Area of Science:
- Oncology
- Molecular Biology
- Cellular Biology
Background:
- HER2-targeted antibody-drug conjugates (ADCs) demonstrate significant efficacy in HER2 mutation-positive non-small cell lung cancer (NSCLC).
- The intracellular trafficking mechanisms of mutant HER2 remain incompletely understood.
Purpose of the Study:
- To elucidate the intracellular trafficking dynamics of mutant HER2 in NSCLC.
- To investigate the mechanisms underlying enhanced HER2 internalization in mutant NSCLC cells.
Main Methods:
- Live cell imaging and in situ proximity ligation assays were employed to study HER2 dynamics in cells expressing wild-type (WT) or mutant HER2.
- Proteins involved in mutant HER2 trafficking were identified using liquid chromatography-tandem mass spectrometry.
Main Results:
- Mutant HER2 exhibited enhanced internalization in NSCLC cells compared to HER2(WT).
- HER2(WT) homodimers localized primarily at the cell surface, while mutant HER2 homodimers were predominantly cytoplasmic.
- EGFR or HER3 knockdown affected HER2(WT) internalization but not mutant HER2 internalization.
- Enhanced mutant HER2 internalization involved clathrin-dependent endocytosis, increased c-Cbl binding and ubiquitination, and was reduced by the HER2 inhibitor zongertinib.
Conclusions:
- Upregulated HER2 phosphorylation promotes clathrin-dependent endocytosis of mutant HER2.
- This enhanced internalization mechanism likely contributes to the therapeutic effectiveness of HER2-targeted ADCs in HER2-mutated NSCLC.
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