Human epidermal growth factor receptor 2 (HER2)

Overview

Human epidermal growth factor receptor 2 (HER2) is a transmembrane receptor tyrosine kinase of the ErbB/HER family, encoded by the ERBB2 gene on chromosome 17q12 and expressed as an approximately 185 kDa glycoprotein with an extracellular region, a single membrane-spanning segment, and an intracellular kinase domain. Unlike its relatives, HER2 binds no known ligand and holds its extracellular region permanently in the open, dimerization-ready conformation the others adopt only after ligand binding — which makes it the preferred partner for epidermal growth factor receptor (EGFR/HER1), HER3 and HER4. Heterodimerization, most potently with HER3, activates the kinase and drives RAS/MAPK, PI3K/protein kinase B (PKB/AKT) and JAK/STAT3 signaling for proliferation, survival and migration. When ERBB2 is amplified, the resulting overexpression pushes dimerization by mass action and signals without ligand at all, an established oncogenic event in breast, gastric and gastroesophageal junction Cancers associated with aggressive biology and higher recurrence risk.

Clinically HER2 is both a biomarker and a target. Immunohistochemistry and in situ hybridization classify tumors as HER2-positive, HER2-low or HER2-negative, and that status — assessed alongside estrogen and progesterone receptor expression in breast cancer, and alongside PD-L1 scoring in gastric and gastroesophageal junction disease, where HER2-negative patients are candidates for PD-1/PD-L1 checkpoint inhibitors such as pembrolizumab or tislelizumab plus chemotherapy — determines first-line treatment. The HER2-low category exists because antibody-drug conjugates changed what counts as actionable: tumors below the threshold for antibody therapy still respond to a conjugate, since the receptor need only deliver a payload rather than carry the tumor's growth signal.

The therapeutic classes act at different points. The antibody trastuzumab binds domain IV, inhibiting signaling and shedding of the extracellular domain and recruiting antibody-dependent cellular cytotoxicity, while pertuzumab binds domain II to block dimerization directly, which is why the two are combined rather than substituted. Small-molecule tyrosine kinase inhibitors act on the intracellular kinase domain and, being small, reach brain metastases that antibodies do not. Antibody-drug conjugates such as ado-trastuzumab emtansine (T-DM1) and trastuzumab deruxtecan (T-DXd) use HER2 binding to deliver a cytotoxic payload, the latter with a membrane-permeable drug that also kills neighboring antigen-negative cells. Because HER2 is expressed in cardiomyocytes, blocking it carries a characteristic risk of usually reversible cardiac dysfunction that requires monitoring. Poor penetration of full-length immunoglobulins into solid tumors motivates smaller engineered formats — radiolabeled or site-specifically conjugated fragments, often fused to albumin-binding domains — and HER2-directed chimeric antigen receptor T cells. Acquired resistance through compensatory signaling and heterogeneity within the tumor microenvironment remains the central limitation of all of it.

Recent Publications Summary (latest 30 papers)

Recent publications on human epidermal growth factor receptor 2 (HER2) span therapeutic, diagnostic, and mechanistic studies across multiple cancer types. In HER2-positive gastroesophageal cancer, zanidatamab-based first-line regimens with chemotherapy, with or without tislelizumab, showed encouraging efficacy and safety in phase 2 studies 42202319May. In HER2-negative advanced gastric or gastroesophageal junction adenocarcinoma, a post-hoc and pooled individual patient-level analysis found that adding a PD-1 antibody to chemotherapy improved overall survival mainly in patients with intermediate PD-L1 expression, while benefit was marginal in some low-intermediate subgroups and absent in CPS <1 disease 42477829Jul. Real-world studies also examined HER2 testing practices and outcomes in HER2-positive locally advanced or metastatic gastric/gastroesophageal junction cancer in China 42217113May.

Several studies focused on HER2-targeted drug delivery and radiotherapy engineering. A HER2-directed 177Lu-labeled Fab radioconjugate with an albumin-binding domain improved pharmacokinetics, tumor dosimetry, and therapeutic efficacy in HER2 tumor models while reducing off-target radiation and hematologic toxicity compared with full-length 177Lu-DOTA-pertuzumab 42467791Jul. Similarly, a site-specific trastuzumab Fab-DM1 conjugate generated by butelase-1 ligation and fused to an albumin-binding domain produced a homogeneous ADC with selective killing of HER2-positive cells and superior tumor growth inhibition in xenografts versus the non-ABD analogue 42384122Jul. Another modular platform used cathepsin S-cleavable linkers in MMAE-based ADCs targeting HER2 or TROP-2, enabling cathepsin S-dependent cytotoxicity across breast cancer models and suggesting that cathepsin S coexpression with HER2 may inform future stratification 42381118Jul. A separate plug-and-play degrader platform achieved simultaneous degradation of EGFR/c-met/HER2, illustrating broader membrane-protein targeting strategies that include HER2 42138807May.

HER2 was also used as a target in multiple diagnostic and biosensing platforms. A CRISPR/Cas12a-based biosensor (“Tribos”) combined an aptamer hairpin switch, rolling circle amplification, and a hairpin-enhanced reporter to detect HER2 with a limit of detection of 1.08 fg/mL and high concordance with clinical diagnosis and ELISA in breast cancer samples 42424600Jul. A proximity-driven 3D DNA aptasensor used tetrahedral framework nucleic acids to improve spatially matched HER2 recognition in living cells and clinical specimens, addressing limitations of conventional immunohistochemistry 42060865Apr. Additional sensing approaches included a biomimetic nanozyme platform for extracellular vesicle detection that incorporated HER2-targeting aptamer probes 42083729May and an ultrasensitive dual-mode immunoassay using bifunctional signal probes and Y-shaped biopeptides 42029682Apr. A radiomics model based on 18F-FDG PET/MR was also developed and validated for noninvasive prediction of HER2 status in colorectal cancer 42060950Apr.

Beyond direct targeting, several studies explored HER2 biology and HER2-associated disease contexts. In HER2-driven mammary tumorigenesis, transcriptomic and proteomic profiling showed downregulation of mitochondrial genes despite increased mitochondrial respiration, suggesting that HER2 signaling can enhance intrinsic bioenergetics even with reduced mitochondrial content 42089475May. A biomineralized DNA nanocomplex combined HER2 silencing with cGAS-STING activation to break oncogene-driven immune suppression in HER2-positive breast cancer, promoting dendritic cell maturation, M1 macrophage polarization, and CD8+ T-cell infiltration 42114778May. A bispecific antibody targeting HER2 and CLEC5A was designed to activate macrophages and enhance anti-HER2 therapy 42055709Apr, while a tri-antigen vaccine targeting IGFBP-2, HER2, and IGF-IR was evaluated for safety and immunogenicity in non-metastatic breast cancer 42082270May. HER2 was also incorporated into a switchable CAR-T strategy using an anti-HER2 scFv fused to VEGF-A to target HER2, VEGFR1, and VEGFR2 in solid tumors 42349416Jun. Additional reports included a retrospective cohort of resected breast cancer brain metastases with substantial representation of HER2-positive disease 42474755Jul, a feasibility study of CBT-based psychological support for women with HER2-positive metastatic breast cancer 42141145May, and a breast cancer transcriptome study in which ERBB2 was downregulated in gestational diabetes placentas 42175401May.

What Changes, What Holds

1. HER2-directed first-line strategies are extending into new combinations, but the core treatment role remains unchanged
REINFORCES Zanidatamab-based regimens in HER2-positive gastroesophageal cancer and the PD-1-plus-chemotherapy analyses in HER2-negative disease mainly refine how HER2 status is used to choose among existing first-line options, rather than changing HER2’s established function as a predictive biomarker and drug target. The real-world testing study likewise speaks to implementation and outcomes, not a new biological role. 42202319May42477829Jul

2. HER2-targeted payload delivery is becoming more modular and better tolerated
REINFORCES The Fab-based radioconjugate and site-specific ADC work strengthens the existing therapeutic concept that HER2 can be exploited to deliver cytotoxic or radioactive payloads, while suggesting that smaller, albumin-binding formats may improve pharmacokinetics and reduce off-target toxicity. That is an engineering advance, not a departure from the Overview’s account of HER2-directed antibodies, ADCs, and fragment-based constructs. The degrader platform broadens membrane-protein targeting but does not alter HER2 biology itself. 42467791Jul42384122Jul

3. HER2 detection is moving toward more sensitive and spatially resolved assays
METHOD The CRISPR/Cas12a biosensor, 3D aptasensor, nanozyme EV assay, dual-mode immunoassay, and PET/MR radiomics model mainly change how HER2 is measured, not what HER2 is. They add analytical sensitivity, living-cell compatibility, or noninvasive prediction, complementing conventional immunohistochemistry and in situ hybridization without displacing them. These are useful diagnostic refinements, but they do not establish a new clinical role for HER2. 42424600Jul42060865Apr

4. HER2 signaling appears to reshape tumor metabolism and immunity in ways that could be therapeutically exploited
NEW DIRECTION The mitochondrial profiling, HER2 silencing plus cGAS-STING activation, macrophage-engaging bispecific, tri-antigen vaccine, and switchable CAR-T work all point to roles for HER2 beyond receptor-driven proliferation and survival, especially in metabolic rewiring and immune modulation. That extends the Overview’s signaling account into the tumor microenvironment and immunotherapy space rather than contradicting it. The mechanistic and preclinical nature of the evidence means these roles remain provisional and need clinical validation. 42089475May42114778May

Overview update candidates: HER2-linked metabolic rewiring; HER2-directed immune modulation strategies.