HER2 protein: A core target of receptor tyrosine kinase signaling-driven and tumor-targeted therapy

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This article focuses on the molecular characteristics and signal transduction functions of human epidermal growth factor receptor 2 (HER2), systematically elaborating its molecular mechanism as a member of the epidermal growth factor receptor family in initiating downstream proliferation signaling pathways through receptor dimerization and tyrosine residue phosphorylation, analyzing the roles of two types of abnormalities—c-erbB-2 gene mutation, deletion, and amplification, as well as HER2 protein overexpression—in tumor occurrence and development, and exploring the differentiated therapeutic value of HER2 gene mutations in lung cancer versus HER2 protein amplification in breast cancer and gastric cancer.

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HER2 Protein: A Core Target of Receptor Tyrosine Kinase Signaling-Driven Tumor Targeted Therapy

Brief Introduction: This article focuses on the molecular characteristics and signal transduction functions of human epidermal growth factor receptor 2 (HER2), systematically elaborating the molecular mechanism by which it, as a member of the epidermal growth factor receptor family, initiates downstream proliferative signaling pathways through receptor dimerization and phosphorylation of tyrosine residues. It analyzes the roles of two types of abnormalities——c-erbB-2 gene mutation, deletion and amplification, and HER2 protein overexpression——in tumor initiation and development, and discusses the differentiated therapeutic value of HER2 gene mutations in lung cancer and HER2 protein amplification in breast cancer and gastric cancer.

I. Molecular Localization and Receptor Family Classification of HER2.

Human epidermal growth factor receptor 2 is a member of the epidermal growth factor receptor family with tyrosine kinase activity. This family includes four members——EGFR (HER1), HER2, HER3 and HER4——which together constitute a core signaling network regulating cell proliferation, differentiation and survival. HER2 has a unique structural feature within the family: its extracellular domain can adopt a conformation resembling ligand-activated states even in the absence of ligand binding, making it the receptor most prone to forming heterodimers with other family members. No direct high-affinity ligand has yet been identified for HER2 itself; its main function is to amplify and transmit signals through dimerization with other family members. This role as a "signal amplifier without a ligand" determines the special position of HER2 in normal physiology and tumor pathology.

II. HER2 Receptor Dimerization and Activation of Downstream Signaling Pathways.

Dimerization of HER2 receptors leads to phosphorylation of receptor tyrosine residues, initiating multiple signaling pathways that result in cell proliferation and tumor initiation and development. From a molecular mechanism perspective, after HER2 forms homodimers or heterodimers with family members, the intracellular kinase domains undergo trans-autophosphorylation; the phosphorylated tyrosine residues provide docking sites for adaptor proteins containing SH2 domains, thereby activating the two core signaling pathways PI3K/AKT and RAS/RAF/MEK/ERK. The former mainly mediates cell survival and anti-apoptosis, while the latter mainly drives cell cycle progression and proliferation. The synergistic activation of both pathways makes HER2 a key hub connecting extracellular growth signals with intracellular proliferation programs. When HER2 is persistently activated due to genomic abnormalities, this signaling hub transforms from a normal regulatory node into a tumor driver.

III. Two Types of HER2 Abnormalities: Gene Alterations and Protein Overexpression.

HER2 abnormalities are present in numerous tumors, including c-erbB-2 gene mutation, deletion and amplification, as well as HER2 protein overexpression. Distinguished at the molecular level, gene amplification leads to massive expression of HER2 protein on the cell membrane surface, creating a high-density receptor state that significantly increases the probability of dimerization and generates persistent signals; gene mutations alter the amino acid sequence of the kinase domain or extracellular domain, enabling the receptor to maintain an activated conformation even without a dimerization partner; gene deletions may affect functional regulation by altering protein structure. The two types of abnormalities differ fundamentally in detection methods and therapeutic strategies——protein overexpression is mainly detected by immunohistochemistry, gene amplification is mainly detected by in situ hybridization, and gene mutations require sequencing technology for identification. Understanding this distinction is a prerequisite for understanding the differentiated application of HER2-targeted therapy across different cancer types.

IV. Cancer Type-Specific Therapeutic Value of HER2 Abnormalities.

Current clinical trial evidence suggests that HER2 gene mutations have important therapeutic value in lung cancer, while HER2 protein amplification has important therapeutic value in breast cancer and gastric cancer. This cancer type-specific difference reflects differences in the mechanisms of occurrence and biological consequences of HER2 abnormalities across different tumors. In breast cancer and gastric cancer, HER2 protein overexpression is mainly driven by gene amplification, with extremely high receptor density on the cell membrane surface; anti-HER2 antibodies and antibody-drug conjugates can exert therapeutic effects by binding to membrane-surface receptors. In lung cancer, however, HER2 abnormalities more often manifest as gene mutations in the kinase domain, and tumor cells depend on the persistent kinase activity of mutant HER2 to maintain growth, making small-molecule tyrosine kinase inhibitors a more matched intervention approach. This pattern of "same target, different abnormality types, different cancer types, different drug modalities" embodies the core principle of target-abnormality-drug matching in precision medicine.

V. Conclusion.

As a core member of the epidermal growth factor receptor family with tyrosine kinase activity, HER2 has become one of the most representative targets in the field of tumor precision therapy, owing to its molecular mechanism of initiating PI3K/AKT and RAS/RAF/MEK/ERK signaling pathways through receptor dimerization and tyrosine residue phosphorylation to drive cell proliferation, the widespread presence of two types of abnormalities——c-erbB-2 gene mutation, deletion and amplification, and HER2 protein overexpression——in multiple tumors, and clinical evidence of the differentiated therapeutic value of HER2 gene mutations in lung cancer and HER2 protein amplification in breast cancer and gastric cancer.

In HER2-related basic research and targeted drug development, high-quality recombinant HER2 protein is a core tool for dissecting its receptor dimerization mechanisms, evaluating the binding activity of targeted drugs, and developing detection methods. To meet the needs of HER2 functional research and tumor-targeted therapeutic drug development, Ulove provides HER2 Protein. This product is suitable for applications including binding activity analysis of HER2 with targeted antibodies and antibody-drug conjugates, in vitro studies of HER2 receptor dimerization and signaling pathway activation mechanisms, screening and activity evaluation of HER2-targeted drugs, and establishment and validation of HER2 immunoassay methods.

This article is reviewed and published by the technical expert team of UA

Disclaimer: This article partially utilizes artificial intelligence assistance in its creation. If any content involves copyright or intellectual property issues, please let us know and we promise to verify and remove it as soon as possible.

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