ErbB3 Human

What is ErbB3/HER3 and how does it differ from other ERBB family members?

ErbB3 (also known as HER3, human epidermal growth factor receptor 3) is a membrane-bound protein encoded by the ERBB3 gene in humans . It belongs to the epidermal growth factor receptor (EGFR/ERBB) family of receptor tyrosine kinases, which serves as receptors for the epidermal growth factor (EGF) family .

What makes ErbB3 unique among the four ERBB family members is its functionally defective tyrosine kinase domain . It contains several nonconserved regions in the kinase domain, particularly at positions 740 (Ala instead of conserved Cys), 759 (His instead of Glu), and 834 (Asn instead of Asp) . This impairment results in approximately 100-fold reduction in capacity for autophosphorylation and substrate phosphorylation compared to other family members .

Despite this impairment, recent research indicates that ErbB3 retains sufficient kinase activity to robustly trans-autophosphorylate its intracellular region, although it is substantially less active than EGFR and does not phosphorylate exogenous peptides . This residual activity may be crucial for its signaling functions.

How is the ERBB3 gene expressed during development and in adult tissues?

The human ERBB3 gene is located on the long arm of chromosome 12 (12q13) and consists of 28 exons spanning approximately 23.2 kb . It encodes a protein of 1342 amino acids .

During human development, ERBB3 expression follows a specific pattern. It is expressed from the earliest stages of development, being detected throughout spermatogenesis and in ejaculated human sperm . During organogenesis, ERBB3 mRNA levels and distribution are distinct from other ERBB receptors, suggesting unique developmental functions . In human fetuses, ERBB3 transcripts are detected in liver, kidney, and brain but not in heart or lung fibroblasts .

In adult human tissues, ERBB3 shows widespread expression. It is consistently detected in skin, bone, muscle, nervous system, heart, lungs, and intestinal epithelium . Additionally, it is expressed in the gastrointestinal tract, reproductive system, urinary tract, and endocrine system . This broad expression pattern suggests diverse physiological roles in various tissues.

What methodologies can be used to study ErbB3 kinase activity despite its impaired catalytic domain?

Studying ErbB3 kinase activity requires specialized approaches due to its unique properties:

• ATP binding assays: ErbB3 kinase domain binds ATP with a Kd of approximately 1.1 μM, which can be measured using techniques like isothermal titration calorimetry or fluorescence-based assays .

• Structural analysis: X-ray crystallography can be used to determine the structure of ErbB3 kinase bound to ATP analogues, revealing its conformational features . The crystal structure resembles inactive EGFR and ErbB4 kinase domains but with a shortened αC-helix .

• Trans-autophosphorylation assays: Despite having impaired kinase activity, ErbB3 can robustly trans-autophosphorylate its intracellular region, which can be detected using phospho-specific antibodies or mass spectrometry .

• Computational approaches: Quantum mechanics/molecular mechanics (QM/MM) simulations can be used to delineate reaction pathways for ErbB3-catalyzed phosphoryl transfer that do not require the conserved catalytic base .

• Mutational analysis: Introducing mutations at key positions (740, 759, and 834) can help understand the unique aspects of ErbB3 kinase function. Interestingly, mutations that activate EGFR and ErbB4 conversely inactivate ErbB3 .

What is the structure of the ErbB3 receptor and how does it contribute to its function?

The ErbB3 receptor, like other members of the ERBB family, consists of three main domains:

• Extracellular domain: Contains four subdomains (I-IV)

  • Subdomains I and III are leucine-rich and primarily involved in ligand binding

  • Subdomains II and IV are cysteine-rich and contribute to protein conformation and stability through disulfide bond formation

  • Subdomain II contains the dimerization loop required for dimer formation

• Transmembrane domain: A single membrane-spanning region

• Intracellular domain: Consists of

  • A juxtamembrane segment

  • A kinase domain with impaired catalytic activity

  • A C-terminal domain containing phosphorylation sites

In its unliganded state, ErbB3 adopts a conformation that inhibits dimerization . Binding of neuregulin to the ligand binding subdomains (I and III) induces a conformational change that causes the protrusion of the dimerization loop in subdomain II, activating the protein for dimerization .

The unique structural features of ErbB3's kinase domain—including substitutions at positions 740, 759, and 834—contribute to its impaired but not abolished kinase activity, allowing it to function primarily as an allosteric activator while maintaining some catalytic capability .

How does ErbB3 interact with other ERBB family members, particularly ErbB2/HER2?

ErbB3 can heterodimerize with any of the other three ErbB family members, but its interaction with ErbB2/HER2 is particularly significant . Key aspects of these interactions include:

• Preferential heterodimer formation: The ErbB2-ErbB3 dimer is considered the most active of the possible ErbB dimers . This is because:

  • ErbB2 is the preferred dimerization partner of all ErbB family members

  • ErbB3 is the preferred partner of ErbB2

• Activation mechanism: ErbB3 binds ligands like heregulin and NRG-2, causing a conformational change that allows for dimerization, phosphorylation, and activation of signal transduction . When heterodimerized with ErbB2, which lacks a known ligand, the complex can still be activated through ErbB3's ligand binding .

• Signaling pathways: The ErbB2-ErbB3 heterodimer activates multiple pathways including MAPK, PI3K/Akt, and PLCγ .

• Ligand-independent activation: ErbB2 overexpression may promote the formation of active heterodimers with ErbB3 without the need for ligand binding, resulting in weak but constitutive signaling activity . This is particularly relevant in cancer cells with ErbB2 amplification.

• Therapeutic implications: The potent signaling capabilities of ErbB2-ErbB3 heterodimers make them important targets for cancer therapy, with resistance to ErbB2-targeted therapies often involving compensatory ErbB3 signaling .

What role does ErbB3 play in cancer development and progression?

Although ErbB3 overexpression, constitutive activation, or mutation alone has not been found to be oncogenic, it plays crucial roles in cancer as a heterodimerization partner, particularly with ErbB2 . ErbB3's involvement in cancer includes:

• Survival and proliferation signaling: ErbB3 activates the PI3K/Akt pathway through its six recognition sites for the SH2 domain of the p85 subunit of PI3K, promoting cancer cell survival and proliferation .

• Therapeutic resistance: ErbB3 is associated with resistance to targeted therapies in numerous cancers, including :

  • HER2 inhibitors in HER2+ breast cancers

  • Anti-estrogen therapy in ER+ breast cancers

  • EGFR inhibitors in lung and head and neck cancers

  • Hormones in prostate cancers

  • IGF1R inhibitors in hepatomas

  • BRAF inhibitors in melanoma

• Metastasis promotion: ErbB3 is implicated in promoting invasion and metastasis through various signaling pathways .

• Expression in multiple cancer types: High expression of ErbB3 has been observed in breast, ovary, prostate, brain, retina, melanoma, colon, pancreas, stomach, oral cavity, and lung cancers .

• Heterodimer formation: ErbB2 overexpression may promote the formation of active heterodimers with ErbB3 without the need for ligand binding, resulting in constitutive signaling activity that drives cancer growth .

Understanding these roles has led to increasing recognition of ErbB3 as a potential therapeutic target in various cancers .

How does ErbB3 contribute to resistance against therapies targeting other ERBB receptors?

Recent evidence indicates that ErbB3 plays a critical role in tumor resistance to therapeutic agents targeting EGFR or ErbB2 . This resistance occurs through several mechanisms:

• Compensatory signaling: When EGFR or ErbB2 are inhibited, cancer cells can upregulate ErbB3 expression or activation to maintain downstream signaling, particularly through the PI3K/Akt pathway .

• Heterodimer reconfiguration: Inhibition of one ERBB receptor can lead to formation of alternative heterodimers involving ErbB3, which may not be affected by the therapeutic agent .

• Ligand-dependent activation: Increased production of ErbB3 ligands (neuregulins) can enhance ErbB3 signaling to compensate for inhibition of other receptors .

• Bypass signaling: ErbB3 can interact with non-ERBB receptors and other kinases to activate downstream pathways even when other ERBB receptors are blocked .

• Reduced drug sensitivity: ErbB3-mediated activation of the PI3K/Akt survival pathway can counteract the pro-apoptotic effects of EGFR or ErbB2 inhibitors .

These resistance mechanisms have been observed in multiple cancer types, including lung, breast, prostate, and melanoma . Understanding ErbB3's role in therapeutic resistance has led to the development of combination strategies that simultaneously target multiple ERBB family members or downstream pathways .

What experimental approaches are being developed to target ErbB3 in cancer therapy?

Several approaches for targeting ErbB3 in cancer therapy have been developed or are under investigation:

• Monoclonal antibodies: Human antibodies like IgG 3-43 have been developed to recognize unique epitopes on ErbB3's extracellular region . These antibodies can bind with subnanomolar affinity in the IgG format and inhibit HER3 activation and tumor growth .

• Recombinant proteins: Recombinant human ErbB3 fragments (rhErbB3-f) can induce specific antibody production in vivo to inhibit tumor cell growth . This approach is classified as a therapeutic cancer vaccine and has been used to treat breast cancer patients with ErbB2 overexpression .

• Small interfering RNA (siRNA): siRNA targeting ErbB3 or its downstream effector AKT has shown promise as a therapeutic approach to treatment of lung adenocarcinoma . This approach directly reduces ErbB3 expression at the mRNA level.

• Combination therapies: Targeting ErbB3 in combination with inhibitors of other ERBB family members (EGFR, ErbB2) has shown enhanced efficacy in preclinical models of various cancers .

• Bispecific antibodies: Antibodies designed to simultaneously target ErbB3 and another receptor (like ErbB2) can potentially overcome resistance mechanisms by blocking multiple signaling pathways .

• Targeting downstream pathways: Inhibitors of pathways activated by ErbB3, particularly the PI3K/Akt pathway, can complement direct ErbB3 targeting strategies .

These approaches represent promising strategies for overcoming ErbB3-mediated cancer growth and therapeutic resistance .

How do the nonconserved regions in ErbB3's kinase domain contribute to its unique signaling properties?

The nonconserved regions in ErbB3's kinase domain at positions 740 (Ala instead of conserved Cys), 759 (His instead of Glu), and 834 (Asn instead of Asp) contribute significantly to its unique signaling properties :

• Alternative catalytic mechanism: Despite lacking the canonical catalytic base (Asp834), ErbB3 can utilize an alternative reaction pathway for phosphoryl transfer, as demonstrated by quantum mechanics/molecular mechanics simulations . This allows it to maintain some catalytic activity despite its "inactive-like" configuration.

• ATP binding capacity: Despite these substitutions, the ErbB3 kinase domain retains the ability to bind ATP with a Kd of approximately 1.1 μM . The consensus sequence for the ATP-binding site (GlyXGlyXXGly at positions 716-721) is conserved in ErbB3 .

• Trans-autophosphorylation capability: ErbB3 retains sufficient kinase activity to robustly trans-autophosphorylate its intracellular region, although it is substantially less active than EGFR and does not phosphorylate exogenous peptides .

• Enhanced downstream interactions: Studies with rat Erbb3 showed that the presence of Asn at position 834 (equivalent to human ErbB3) actually enhanced interaction with downstream targets like Ptpn11 (Syp) and PI3K compared to the "normal" Asp found in other receptors . This suggests these substitutions optimize ErbB3 for its signaling role rather than simply rendering it inactive.

• Structural implications: The crystal structure of ErbB3 kinase resembles inactive EGFR and ErbB4 kinase domains but with a shortened αC-helix . Interestingly, mutations that activate EGFR and ErbB4 conversely inactivate ErbB3, indicating that its "inactive-like" configuration is actually its functional state .

These findings suggest that ErbB3's kinase domain has evolved to optimize it for its unique role in heterodimerization and downstream signaling, rather than simply representing a loss of function .

What role does ErbB3 play in normal developmental processes?

ErbB3 plays critical roles in several normal developmental processes, distinct from its functions in cancer:

• Cardiovascular development: ERBB3 is expressed in the mesenchyme of the endocardial cushion, which later develops into heart valves . ErbB3 null mouse embryos show severely underdeveloped atrioventricular valves, leading to death at embryonic day 13.5 . This function depends on neuregulin but interestingly does not require ErbB2, which is not expressed in this tissue .

• Neural development: ErbB3 is required for neural crest differentiation and the development of the sympathetic nervous system . It also plays a role in the development of neural crest derivatives such as Schwann cells .

• Reproductive system: ERBB3 mRNA is present throughout spermatogenesis and in the nucleus of ejaculated human sperm, suggesting roles in gamete development . It is also expressed in bovine oocytes at all stages .

• Implantation: Erbb3 is expressed and active in epithelial cells of mouse uterus during implantation . ERBB3 mRNA is detected in both cyto- and syncytiotrophoblast at the time of implantation in rabbits, with a pattern distinct from other ERBB receptors .

• Organogenesis: ERBB3 shows unique expression patterns during the development of structures like teeth in mice and fetal rat brain, suggesting specific developmental functions .

These developmental roles highlight the importance of ErbB3 in normal physiological processes beyond its involvement in cancer, and may provide insights into potential side effects of ErbB3-targeted therapies .

How can researchers effectively study ErbB3 heterodimers in experimental systems?

Studying ErbB3 heterodimers requires specialized experimental approaches due to their dynamic nature and context-dependent signaling:

• Structural analysis techniques:

  • X-ray crystallography of ErbB3-containing heterodimer complexes

  • Cryo-electron microscopy for visualization of intact heterodimers

  • Hydrogen-deuterium exchange mass spectrometry to map interaction interfaces

• Protein-protein interaction assays:

  • Co-immunoprecipitation with specific antibodies against ErbB3 and its dimerization partners

  • Förster resonance energy transfer (FRET) using fluorescently tagged receptors to detect close associations

  • Proximity ligation assays for visualizing protein interactions in fixed cells

  • Crosslinking studies to capture transient interactions

• Functional signaling assays:

  • Phospho-specific antibodies to detect activation of ErbB3 and its partners

  • Downstream pathway activation analysis (e.g., PI3K/Akt, MAPK)

  • Inhibitor studies with selective targeting of specific heterodimer pairs

  • Ligand-induced activation studies using neuregulins and other ErbB ligands

• Genetic manipulation approaches:

  • CRISPR/Cas9-mediated mutation of specific residues in dimerization interfaces

  • Expression of dominant-negative mutants to disrupt specific heterodimers

  • siRNA or shRNA knockdown to reduce levels of specific ERBB family members

  • Creation of chimeric receptors to study specific domain contributions

• Single-molecule techniques:

  • Single-molecule imaging to track receptor dynamics and interactions

  • Super-resolution microscopy to visualize receptor clustering and organization

These methodological approaches, often used in combination, can provide comprehensive insights into the formation, stability, and signaling properties of ErbB3-containing heterodimers in different cellular contexts .

What biomarkers can be used to identify patients likely to benefit from ErbB3-targeted therapies?

While the search results don't directly address biomarkers for ErbB3-targeted therapies, we can infer potential biomarkers based on ErbB3 biology:

• ErbB3 expression levels: Immunohistochemistry or RNA sequencing could be used to quantify ErbB3 expression in tumor samples . Higher expression levels might predict better response to ErbB3-targeted therapies.

• ErbB3 phosphorylation status: Phospho-specific antibodies against key tyrosine residues in ErbB3 could identify tumors with active ErbB3 signaling .

• ErbB2/ErbB3 co-expression: Since ErbB2-ErbB3 heterodimers form particularly potent signaling complexes, quantifying both receptors might better predict response than assessing either alone .

• Neuregulin expression: Levels of ErbB3 ligands (neuregulins) in tumor or plasma samples could indicate activation potential of the ErbB3 pathway .

• PI3K/Akt pathway activation: Downstream markers of ErbB3 signaling (e.g., phospho-Akt, PTEN status) might indicate tumors dependent on ErbB3-mediated signaling .

• Resistance to other therapies: Development of resistance to EGFR or ErbB2-targeted therapies might identify tumors that have become dependent on ErbB3 signaling as a bypass mechanism .

• Specific mutations: Although not well characterized yet, mutations in ErbB3 or its signaling partners could potentially predict response to targeted therapies.

These potential biomarkers would need rigorous validation in clinical studies of ErbB3-targeted therapies to establish their predictive value .

How might ErbB3-targeted therapies be optimally combined with other treatment modalities?

Based on ErbB3's biology and role in therapeutic resistance, several rational combination strategies can be proposed:

• Combination with other ERBB inhibitors:

  • ErbB3 targeting combined with EGFR inhibitors could prevent resistance in lung and head and neck cancers

  • ErbB3 targeting combined with ErbB2 inhibitors could enhance efficacy in HER2+ breast cancers and overcome resistance mechanisms

• Combination with downstream pathway inhibitors:

  • PI3K/Akt pathway inhibitors would block the primary signaling output of ErbB3 activation

  • MEK/ERK inhibitors could complement PI3K/Akt inhibition by targeting another important downstream pathway

• Combination with hormonal therapies:

  • ErbB3 targeting could overcome resistance to anti-estrogen therapy in ER+ breast cancers

  • Similar strategies might apply to hormonal therapies in prostate cancer

• Combination with immunotherapy:

  • ErbB3 inhibition might modulate the tumor microenvironment and enhance responses to immune checkpoint inhibitors

  • Therapeutic cancer vaccines using recombinant ErbB3 fragments could synergize with other immunotherapeutic approaches

• Combination with conventional chemotherapy:

  • ErbB3 inhibition could sensitize cancer cells to conventional cytotoxic agents by blocking survival signaling

  • Sequential treatment approaches might be particularly effective (e.g., ErbB3 inhibition to sensitize followed by chemotherapy)

• Based on resistance mechanisms:

  • In BRAF-mutant melanoma, combining ErbB3 inhibitors with BRAF inhibitors could prevent resistance development

  • In hepatomas, combining ErbB3 and IGF1R inhibitors might be effective

Optimal combination strategies would need to be determined through preclinical studies and carefully designed clinical trials that consider tumor type, molecular characteristics, and potential toxicities .

What are the most promising future directions in ErbB3 research?

Based on current understanding of ErbB3 biology, several promising research directions emerge:

• Developing more effective ErbB3-targeted therapeutics:

  • Novel antibodies with improved specificity and affinity, like IgG 3-43

  • Small molecules that can disrupt ErbB3 heterodimer formation or signaling

  • siRNA-based approaches to directly reduce ErbB3 expression

  • Therapeutic vaccines using recombinant ErbB3 fragments

• Understanding ErbB3's kinase activity:

  • Further characterization of its non-canonical catalytic mechanism

  • Development of ATP-competitive inhibitors specific for ErbB3's unique kinase domain

  • Exploration of the functional significance of its trans-autophosphorylation activity

• Elucidating resistance mechanisms:

  • Identifying how tumors might develop resistance to ErbB3-targeted therapies

  • Understanding the compensatory signaling networks activated when ErbB3 is inhibited

  • Developing rational combination strategies to prevent or overcome resistance

• Biomarker discovery:

  • Identifying predictive biomarkers for response to ErbB3-targeted therapies

  • Developing companion diagnostics for patient selection

  • Creating monitoring tools to track ErbB3 activity during treatment

• Expanding applications:

  • Investigating ErbB3's role in additional cancer types like glioblastoma

  • Exploring the potential of ErbB3 as a target in non-cancer diseases where it plays a role

• Basic science discoveries:

  • Further characterizing nuclear localization and functions of ErbB3

  • Understanding the significance of secreted ErbB3 isoforms

  • Elucidating the complete interactome of ErbB3 in different cellular contexts

These research directions hold promise for translating our growing understanding of ErbB3 biology into effective therapeutic strategies for cancer and potentially other diseases .

What methodological challenges remain in studying ErbB3 function and targeting it therapeutically?

Several methodological challenges persist in ErbB3 research:

• Studying heterodimer dynamics:

  • Capturing the transient nature of ErbB3 heterodimers in living cells

  • Distinguishing between different heterodimer pairs in complex systems

  • Developing tools to selectively disrupt specific heterodimer combinations

• Measuring ErbB3 kinase activity:

  • Developing sensitive assays to detect the relatively weak kinase activity

  • Distinguishing ErbB3 autophosphorylation from phosphorylation by partner kinases

  • Creating specific inhibitors for ErbB3's unique catalytic mechanism

• Therapeutic targeting:

  • Overcoming potential compensatory upregulation of other receptors

  • Achieving sufficient target inhibition in tumor tissue

  • Developing therapies that can cross the blood-brain barrier for CNS tumors

  • Balancing efficacy with toxicity, given ErbB3's roles in normal physiology

• Model systems:

  • Creating physiologically relevant models that recapitulate human tumor heterogeneity

  • Developing animal models that accurately reflect ErbB3 biology across species

  • Establishing patient-derived models to study individual variations in ErbB3 signaling

• Clinical translation:

  • Identifying reliable biomarkers for patient selection

  • Designing clinical trials that can detect ErbB3-specific effects

  • Determining optimal combination strategies and sequencing of therapies

• Technical limitations:

  • Visualizing receptors at the molecular level in native membranes

  • Tracking receptor trafficking and recycling in real-time

  • Developing tools to study nuclear ErbB3 functions

Addressing these methodological challenges will be crucial for advancing our understanding of ErbB3 biology and developing effective therapeutic strategies targeting this important receptor .

What are the key considerations when designing experiments to study ErbB3 in cancer models?

When designing experiments to study ErbB3 in cancer models, researchers should consider:

• Model selection:

  • Cell line choice: Different cancer cell lines exhibit varying levels of ErbB3 expression and dependence on its signaling

  • Patient-derived models: These better represent tumor heterogeneity but may be more complex to work with

  • In vivo models: Consider species differences in ErbB3 biology; the epitope recognized by antibody IgG 3-43 is conserved between human HER3 and mouse ErbB3, making it useful for preclinical studies

• Activation conditions:

  • Ligand selection: ErbB3 binds heregulin and NRG-2 , which may have different effects

  • Serum conditions: Serum factors can influence ErbB3 activation state

  • Cell density: Affects receptor clustering and spontaneous activation

• Heterodimerization partners:

  • Expression levels of other ERBB family members will affect ErbB3 signaling

  • Consider co-expression or knockdown experiments to study specific heterodimer pairs

• Detection methods:

  • Use phospho-specific antibodies to detect ErbB3 activation

  • Consider total ErbB3 levels versus phosphorylated ErbB3

  • Assess downstream signaling (e.g., PI3K/Akt pathway activation)

• Inhibition approaches:

  • Genetic: siRNA, shRNA, CRISPR/Cas9 for ErbB3 knockout or mutation

  • Pharmacological: Antibodies, recombinant fragments, or small molecules

  • Combination strategies: To address compensatory mechanisms

• Resistance mechanisms:

  • Pre-existing versus acquired resistance

  • Compensatory upregulation of other receptors or ligands

  • Alternative pathway activation

• Functional readouts:

  • Proliferation, survival, migration, invasion assays

  • Long-term versus short-term effects

  • In vivo tumor growth and metastasis

• Clinical relevance:

  • Correlation with patient data

  • Biomarker assessment

  • Therapeutic implications

By carefully considering these factors, researchers can design more informative experiments that advance our understanding of ErbB3's role in cancer and facilitate the development of effective therapeutic strategies .

How can researchers effectively measure ErbB3 signaling activity in experimental systems?

Measuring ErbB3 signaling activity requires multiple complementary approaches:

• Receptor activation status:

  • Phospho-specific antibodies against key ErbB3 tyrosine residues

  • Immunoprecipitation followed by phosphotyrosine blotting

  • Mass spectrometry-based phosphoproteomics to identify all phosphorylation sites

  • Conformation-specific antibodies that recognize the activated state

• Dimerization assessment:

  • Proximity ligation assays to visualize specific heterodimer pairs in situ

  • Co-immunoprecipitation to detect physical associations

  • Chemical crosslinking to capture transient interactions

  • FRET or BRET to measure protein-protein interactions in living cells

• Downstream pathway activation:

  • Phosphorylation of key PI3K/Akt pathway components (p85, Akt, mTOR)

  • Activation of MAPK pathway members (Erk1/2 phosphorylation)

  • PLCγ pathway activity

  • Protein-protein interactions between ErbB3 and downstream effectors (p85, Shc, Grb2)

• Gene expression analysis:

  • RNA-seq to identify transcriptional changes downstream of ErbB3 activation

  • qRT-PCR for key target genes

  • Reporter assays for specific transcriptional responses

• Functional outcomes:

  • Cell proliferation assays (e.g., BrdU incorporation, Ki67 staining)

  • Survival/apoptosis assays (e.g., Annexin V, cleaved caspase-3)

  • Migration and invasion assays

  • 3D culture phenotypes (morphology, acini formation)

• Pharmacological manipulation:

  • Dose-response studies with ErbB3-targeting agents

  • Time-course analyses to capture signaling dynamics

  • Washout experiments to assess pathway reactivation

  • Combination studies with inhibitors of other pathways

• In vivo readouts:

  • Tumor growth measurements

  • Immunohistochemistry for phospho-ErbB3 and downstream markers

  • Ex vivo analysis of tumor material after treatment

By integrating multiple measurement approaches, researchers can gain a comprehensive understanding of ErbB3 signaling activity and how it is affected by genetic or pharmacological manipulations .

What reagents and tools are available for studying ErbB3 in research settings?

Several reagents and tools are available for ErbB3 research:

• Antibodies:

  • Anti-ErbB3 monoclonal antibodies for various applications (WB, IP, IHC, IF)

  • Phospho-specific antibodies against key tyrosine residues

  • Therapeutic antibodies like IgG 3-43 that can be used in experimental settings

  • Conformation-specific antibodies

• Recombinant proteins:

  • Human ErbB3 extracellular domain (ECD)

  • ErbB3-Fc fusion proteins

  • Recombinant ligands (neuregulins, NRG-2)

  • Engineered ErbB3 fragments (e.g., ErbB3-f)

• Expression constructs:

  • Wild-type ErbB3 cDNA in various vectors

  • Mutant ErbB3 constructs (kinase domain mutations, phosphorylation site mutations)

  • Fluorescently tagged ErbB3 for live imaging

  • Inducible expression systems

• Genetic tools:

  • siRNA/shRNA against ErbB3

  • CRISPR/Cas9 components for ErbB3 knockout or mutation

  • Dominant-negative constructs

• Small molecules:

  • ATP-competitive inhibitors for ErbB3 kinase domain

  • Inhibitors of downstream pathways (PI3K, Akt, MEK)

  • Chemical probes for pathway analysis

• Cell and tissue resources:

  • Cell lines with varying ErbB3 expression levels

  • Patient-derived xenograft models

  • Tissue microarrays containing samples with annotated ErbB3 status

• Assay kits:

  • ELISA kits for ErbB3 quantification

  • Kinase activity assays adaptable for ErbB3

  • Dimerization assay kits

• Computational resources:

  • Structural data for ErbB3 kinase domain

  • Signaling pathway databases

  • Gene expression datasets related to ErbB3 function

These resources enable comprehensive investigation of ErbB3 biology, from basic mechanistic studies to translational research and therapeutic development .

What experimental models best represent ErbB3 biology in human disease?

Several experimental models can be used to study ErbB3 biology in human disease contexts:

• Cell line models:

  • Breast cancer cell lines with varying levels of ErbB2 and ErbB3 expression (e.g., SKBR3, BT474, MCF7)

  • Lung cancer cell lines, particularly those with EGFR mutations or that have developed resistance to EGFR inhibitors

  • Prostate, ovarian, colon, and pancreatic cancer cell lines with documented ErbB3 expression

  • Melanoma cell lines, especially those with resistance to BRAF inhibitors

  • Glioblastoma cell lines to study ErbB3 in brain tumors

• 3D culture systems:

  • Spheroid cultures that better recapitulate tissue architecture

  • Organoid models derived from patient samples

  • Co-culture systems with stromal components

• Patient-derived models:

  • Patient-derived xenografts (PDX) that maintain tumor heterogeneity

  • Patient-derived organoids

  • Ex vivo culture of patient tumor slices

• Engineered models:

  • Isogenic cell lines with CRISPR/Cas9-engineered ErbB3 mutations

  • Cells with inducible ErbB3 expression or knockdown

  • Cells with fluorescently tagged ErbB3 for live imaging

• Animal models:

  • Genetically engineered mouse models with altered ErbB3 expression or mutation

  • Xenograft models using cell lines or patient-derived material

  • Models of therapeutic resistance by long-term treatment with EGFR or ErbB2 inhibitors

• Models of specific disease contexts:

  • Breast cancer models with varying hormone receptor and ErbB2 status

  • Models of acquired resistance to targeted therapies

  • Models representing specific cancer subtypes where ErbB3 plays a key role

When selecting experimental models, researchers should consider:

• Expression levels of ErbB3 and other ERBB family members

• Presence of ErbB3 ligands in the system

• Activation state of downstream pathways

• Response to ErbB-targeting therapies

• Correlation with clinical observations in patients

The most informative approach often involves using multiple complementary models to validate findings across different systems .