New insights into ErbB3 function and therapeutic targeting in cancer

Circ_0098823 binding with IGF2BP3 regulates DNM1L stability to promote metastasis of hepatocellular carcinoma via mitochondrial fission

Hepatocellular carcinoma (HCC) is highly metastatic and invasive. CircRNA participates in gene regulation of multiple tumor metastases, but little is known whether it is a bystander or an actual player in HCC metastasis. We aim to explore the molecular mechanisms of novel circRNAs in HCC metastasis. RT-qPCR was used to detect the expression of 13 circRNAs derived by the ERBB3 gene. The function of circ_0098823 and DNM1L in HCC cells were estimated by CCK-8, transwell assays, flow cytometry, electron microscope, and in vivo experiments. RNA binding protein of circ_0098823 was confirmed by RNA pull-down, mass spectrometry, and RNA immunoprecipitation. The expression of DNM1L after IGF2BP3 knockdown was detected by RT-qPCR and western blot. Circ_0098823 was significantly up-regulated both in HCC tissues and HGF induced cell lines. Circ_0098823 overexpression significantly enhanced proliferation, migration, and invasion but decreased apoptosis of HCC cells, particularly promoted mitochondrial fission. Compared with the control group, the tumors in the circ_0098823 knockdown mice were significantly smaller and lighter. Circ_0098823 silencing suppressed DNM1L expression, a key molecule for fission, which enhanced proliferation, migration and invasion, and inhibited apoptosis of HCC cell. IGF2BP3 was a binding protein of circ_0098823. The expression and mRNA stability of DNM1L were down-regulated by IGF2BP3 knockdown. IGF2BP3 knockdown significantly alleviated the excessive migration, invasion and apoptosis of HCC cells caused by circ_0098823 overexpression. This study uncovered a novel circ_0098823 with tumor-promoting effect, and the mechanism by which circ_0098823 participates in HCC progression through IGF2BP3-guided DNM1L. Our study broadens molecular understanding of HCC progression.

The novel antibody fusion protein rhNRG1-HER3i promotes heart regeneration by enhancing NRG1-ERBB4 signaling pathway

Stimulating cardiomyocyte proliferation in the adult heart has emerged as a promising strategy for cardiac regeneration following myocardial infarction (MI). The NRG1-ERBB4 signaling pathway has been implicated in the regulation of cardiomyocyte proliferation. However, the therapeutic potential of recombinant human NRG1 (rhNRG1) has been limited due to the low expression of ERBB4 in adult cardiomyocytes. Here, we investigated whether a fusion protein of rhNRG1 and an ERBB3 inhibitor (rhNRG1-HER3i) could enhance the affinity of NRG1 for ERBB4 and promote adult cardiomyocyte proliferation. In vitro and in vivo experiments were conducted using postnatal day 1 (P1), P7, and adult cardiomyocytes. Western blot analysis was performed to assess the expression and activity of ERBB4. Cardiomyocyte proliferation was evaluated using Ki67 and pH 3 immunostaining, while fibrosis was assessed using Masson staining. Our results indicate that rhNRG1-HER3i, but not rhNRG1, promoted P7 and adult cardiomyocyte proliferation. Furthermore, rhNRG1-HER3i improved cardiac function and reduced cardiac fibrosis in post-MI hearts. Administration of rhNRG1-HER3i inhibited ERBB3 phosphorylation while increasing ERBB4 phosphorylation in adult mouse hearts. Additionally, rhNRG1-HER3i enhanced angiogenesis following MI compared to rhNRG1. In conclusion, our findings suggest that rhNRG1-HER3i is a viable therapeutic approach for promoting adult cardiomyocyte proliferation and treating MI by enhancing NRG1-ERBB4 signaling pathway.

CD44s and CD44v8-10 isoforms confer acquired resistance to osimertinib by activating the ErbB3/STAT3 signaling pathway

AIMS

Although epidermal growth factor receptor (EGFR)-mutant lung cancers respond well to osimertinib, acquired resistance to osimertinib eventually develops through EGFR-dependent and EGFR-independent resistance mechanisms. CD44 splicing variants are widely expressed in lung cancer tissues. However, it remains unclear whether specific splicing variants are involved in acquired resistance to osimertinib.

MAIN METHODS

The real-time PCR was performed to measure the expression levels of total CD44 and specific CD44 splicing variants (CD44s or CD44v). Gene knockdown and restoration were performed to investigate the effects of CD44 splicing variants on osimertinib sensitivity. Activation of the signaling pathway was evaluated using receptor-tyrosine-kinase phosphorylation membrane arrays, co-immunoprecipitation, and western blotting.

KEY FINDINGS

Clinical analysis demonstrated that the expression level of total CD44 increased in primary cancer cells from lung adenocarcinomas patients after the development of acquired resistance to osimertinib. Furthermore, osimertinib-resistant cells showed elevated levels of either the CD44s variant or CD44v variants. Manipulations of CD44s or CD44v8-10 were performed to investigate their effects on treatment sensitivity to osimertinib. Knockdown of CD44 increased osimertinib-induced cell death in osimertinib-resistant cells. However, restoration of CD44s or CD44v8-10 in CD44-knockdown H1975/AZD-sgCD44 cells induced osimertinib resistance. Mechanically, we showed that ErbB3 interacted with CD44 and was transactivated by CD44, that consequently triggered activation of the ErbB3/STAT3 signaling pathway and led to CD44s- or CD44v8-10-mediated osimertinib resistance.

SIGNIFICANCE

CD44 is a co-receptor for ErbB3 and triggers activation of the ErbB3 signaling axis, leading to acquired resistance to osimertinib. CD44/ErbB3 signaling may represent a therapeutic target for overcoming osimertinib resistance.

Exploration and validation of key genes associated with early lymph node metastasis in thyroid carcinoma using weighted gene co-expression network analysis and machine learning

Background

Thyroid carcinoma (THCA), the most common endocrine neoplasm, typically exhibits an indolent behavior. However, in some instances, lymph node metastasis (LNM) may occur in the early stages, with the underlying mechanisms not yet fully understood.

Materials and methods

LNM potential was defined as the tumor's capability to metastasize to lymph nodes at an early stage, even when the tumor volume is small. We performed differential expression analysis using the 'Limma' R package and conducted enrichment analyses using the Metascape tool. Co-expression networks were established using the 'WGCNA' R package, with the soft threshold power determined by the 'pickSoftThreshold' algorithm. For unsupervised clustering, we utilized the 'ConsensusCluster Plus' R package. To determine the topological features and degree centralities of each node (protein) within the Protein-Protein Interaction (PPI) network, we used the CytoNCA plugin integrated with the Cytoscape tool. Immune cell infiltration was assessed using the Immune Cell Abundance Identifier (ImmuCellAI) database. We applied the Least Absolute Shrinkage and Selection Operator (LASSO), Support Vector Machine (SVM), and Random Forest (RF) algorithms individually, with the 'glmnet,' 'e1071,' and 'randomForest' R packages, respectively. Ridge regression was performed using the 'oncoPredict' algorithm, and all the predictions were based on data from the Genomics of Drug Sensitivity in Cancer (GDSC) database. To ascertain the protein expression levels and subcellular localization of genes, we consulted the Human Protein Atlas (HPA) database. Molecular docking was carried out using the mcule 1-click Docking server online. Experimental validation of gene and protein expression levels was conducted through Real-Time Quantitative PCR (RT-qPCR) and immunohistochemistry (IHC) assays.

Results

Through WGCNA and PPI network analysis, we identified twelve hub genes as the most relevant to LNM potential from these two modules. These 12 hub genes displayed differential expression in THCA and exhibited significant correlations with the downregulation of neutrophil infiltration, as well as the upregulation of dendritic cell and macrophage infiltration, along with activation of the EMT pathway in THCA. We propose a novel molecular classification approach and provide an online web-based nomogram for evaluating the LNM potential of THCA (http://www.empowerstats.net/pmodel/?m=17617_LNM). Machine learning algorithms have identified ERBB3 as the most critical gene associated with LNM potential in THCA. ERBB3 exhibits high expression in patients with THCA who have experienced LNM or have advanced-stage disease. The differential methylation levels partially explain this differential expression of ERBB3. ROC analysis has identified ERBB3 as a diagnostic marker for THCA (AUC=0.89), THCA with high LNM potential (AUC=0.75), and lymph nodes with tumor metastasis (AUC=0.86). We have presented a comprehensive review of endocrine disruptor chemical (EDC) exposures, environmental toxins, and pharmacological agents that may potentially impact LNM potential. Molecular docking revealed a docking score of -10.1 kcal/mol for Lapatinib and ERBB3, indicating a strong binding affinity.

Conclusion

In conclusion, our study, utilizing bioinformatics analysis techniques, identified gene modules and hub genes influencing LNM potential in THCA patients. ERBB3 was identified as a key gene with therapeutic implications. We have also developed a novel molecular classification approach and a user-friendly web-based nomogram tool for assessing LNM potential. These findings pave the way for investigations into the mechanisms underlying differences in LNM potential and provide guidance for personalized clinical treatment plans.

Taking early preventive interventions to manage the challenging issue of acquired resistance to third-generation EGFR inhibitors

Although the clinical efficacies of third-generation epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) such as osimertinib in the treatment of non-small cell lung cancer (NSCLC) with EGFR-activating mutations are promising, drug-acquired resistance inevitably occurs whether they are used as first-line or second-line treatment. Therefore, managing the acquired resistance to third-generation EGFR-TKIs is crucial in the clinic for improving patient survival. Great efforts have been made to develop potentially effective strategies or regimens for the treatment of EGFR-mutant NSCLC patients after relapse following these TKIs therapies with the hope that patients will continue to benefit from treatment through overcoming acquired resistance. Although this approach, which aims to overcome drug-acquired resistance, is necessary and important, it is a passive practice. Taking preventive action early before disease progression to manage the unavoidable development of acquired resistance offers an equally important and efficient approach. We strongly believe that early preventive interventions using effective and tolerable combination regimens that interfere with the process of developing acquired resistance may substantially improve the outcomes of EGFR-mutant NSCLC treatment with third-generation EGFR-TKIs. Thus, this review focuses on discussing the scientific rationale and mechanism-driven strategies for delaying and even preventing the emergence of acquired resistance to third-generation EGFR-TKIs, particularly osimertinib.

Identification of Novel Plasma Biomarkers for Abdominal Aortic Aneurysm by Protein Array Analysis

Abdominal aortic aneurysm (AAA) is a potentially life-threatening disease that is common in the aging population. Currently, there are no approved diagnostic biomarkers or therapeutic drugs for AAA. We aimed to identify novel plasma biomarkers or potential therapeutic targets for AAA using a high-throughput protein array-based method. Proteomics expression profiles were investigated in plasma from AAA patients and healthy controls (HC) using 440-cytokine protein array analysis. Several promising biomarkers were further validated in independent cohorts using enzyme-linked immunosorbent assay (ELISA). Thirty-nine differentially expressed plasma proteins were identified between AAA and HC. Legumain (LGMN) was significantly higher in AAA patients and was validated in another large cohort. Additionally, "AAA without diabetes" (AAN) patients and "AAA complicated with type 2 diabetes mellitus" (AAM) patients had different cytokine expression patterns in their plasma, and nine plasma proteins were differentially expressed among the AAN, AAM, and HC subjects. Delta-like protein 1 (DLL1), receptor tyrosine-protein kinase erbB-3 (ERBB3), and dipeptidyl peptidase 4 (DPPIV) were significantly higher in AAM than in AAN. This study identified several promising plasma biomarkers of AAA. Their role as therapeutic targets for AAA warrants further investigation.

CircEPSTI1 Promotes the Proliferation of HER2-Positive Breast Cancer Cells via circEPSTI1/miR-145/ERBB3 Axis

Breast cancer is the most common type of cancer worldwide. There are great challenges in the prevention and treatment of breast cancer. In this study, we explored the molecular and biological mechanisms of circular RNA circEPSTI1 (has_circ_0000479) in the regulation of HER2-positive breast cancer cells. The expression of CircEPSTI1, microRNA miR-145, and ERBB3 in HER2-positive breast cancer cells was evaluated by qRT-PCR and western blot assays. Cell proliferation was assessed by CCK-8. Wound-healing and transwell migration assays were performed to evaluate cell migration. A transwell invasion assay was performed to detect cell invasion. The interaction of miR-145, circEPSTI1, and ERBB3 was confirmed bydual-luciferase reporter and RIP assays. CircEPSTI1 was upregulated in the HER2-positive breast cancer tissues and cells. Knockdown of circEPSTI1 inhibited SKBR3 and BT474 cell proliferation, migration, and invasion. Mechanistically, circEPSTI1 directly targeted miR-145, and miR-145 was a downstream mediator of circEPSTI1 in modulating the proliferation, migration, and invasion of SKBR3 and BT474 cells. ERBB3 was identified as a direct and functional target of miR-145 in HER2-positive breast cancer cells. Our findings demonstrate that circEPSTI1, an overexpressed circRNA in HER2-positive breast cancer, promotes the proliferation, migration, and invasion of SKBR3 and BT474 cells through the miR-145/ERBB3 axis.

The molecular, immune features, and risk score construction of intraductal papillary mucinous neoplasm patients

Intraductal papillary mucinous neoplasm (IPMN) is a common pancreatic precancerous lesion, with increasing incidence in recent years. However, the mechanisms of IPMN progression into invasive cancer remain unclear. The mRNA expression data of IPMN/PAAD patients were extracted from the TCGA and GEO databases. First, based on GSE19650, we analyzed the molecular alterations, tumor stemness, immune landscape, and transcriptional regulation of IPMN progression. The results indicated that gene expression changed dramatically, specifically at the intraductal papillary-mucinous adenoma (IPMA) stage. Gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Kyoto Encyclopedia of Genes and Genomes (GSEA) pathway analyses showed that glycoprotein-related, cell cycle, and P53 pathways displayed the most significant changes during progression. With IPMN progression, tumor stemness increased continuously, and KRAS, ERBB3, RUNX1, and ELF3 are essential driver genes affecting tumor stemness. Motif analysis suggested that KLF4 may be a specific transcription factor that regulates gene expression in the IPMA stage, while MYB and MYBL1 control gene expression in the IPMC and invasive stages, respectively. Then, GSE19650 and GSE71729 transcriptome data were combined to perform the least absolute shrinkage and selection operator (LASSO) method and Cox regression analysis to develop an 11-gene prediction model (KCNK1, FHL2, LAMC2, CDCA7, GPX3, C7, VIP, HBA1, BTG2, MT1E, and LYVE1) to predict the prognosis of pancreatic cancer patients. The reliability of the model was validated in the GSE71729 and TCGA databases. Finally, 11 additional IPMN patients treated in our hospital were included, and the immune microenvironment changes during IPMN progression were analyzed by immunohistochemistry (IHC). IHC results suggest that Myeloid-derived suppressor cells (MDSCs) and macrophages may be key in the formation of immunosuppressive microenvironment of IPMN progression. Our study deepens our understanding of IPMN progression, especially the changes in the immune microenvironment. The findings of this work may contribute to the development of new therapeutic strategies for IPMN.

ErbB3-Targeting Oncolytic Adenovirus Causes Potent Tumor Suppression by Induction of Apoptosis in Cancer Cells

Cancer is a multifactorial and deadly disease. Despite major advancements in cancer therapy in the last two decades, cancer incidence is on the rise and disease prognosis still remains poor. Furthermore, molecular mechanisms of cancer invasiveness, metastasis, and drug resistance remain largely elusive. Targeted cancer therapy involving the silencing of specific cancer-enriched proteins by small interfering RNA (siRNA) offers a powerful tool. However, its application in clinic is limited by the short half-life of siRNA and warrants the development of efficient and stable siRNA delivery systems. Oncolytic adenovirus-mediated therapy offers an attractive alternative to the chemical drugs that often suffer from innate and acquired drug resistance. In continuation to our reports on the development of oncolytic adenovirus-mediated delivery of shRNA, we report here the replication-incompetent (dAd/shErbB3) and replication-competent (oAd/shErbB3) oncolytic adenovirus systems that caused efficient and persistent targeting of ErbB3. We demonstrate that the E1A coded by oAd/shErbB, in contrast to dAd/shErbB, caused downregulation of ErbB2 and ErbB3, yielding stronger downregulation of the ErbB3-oncogenic signaling axis in in vitro models of lung and breast cancer. These results were validated by in vivo antitumor efficacy of dAd/shErbB3 and oAd/shErbB3.

Differential tumor inhibitory effects induced by HER3 extracellular subdomain-specific mouse monoclonal antibodies

PURPOSE

The therapeutic potential of targeting the human epidermal growth factor receptor-3 (ErbB3/HER3) has long been ignored due to impaired tyrosine kinase function and low expression level in tumor cells compared with EGFR and HER2. Although recent investigations have explored the potential benefit of HER3 targeting and several anti-HER3 agents have been developed, there is still a critical need to design and produce more efficient therapeutics. This study was designed to develop tumor inhibitory monoclonal antibodies (MAbs) against different extracellular subdomains of HER3.

METHODS

Distinct extracellular subdomains of HER3 (D_I+II and D_III+IV) were utilized to produce MAbs by hybridoma technology. Biochemical and functional characteristics of these MAbs were then investigated by various methodologies, including immunoblotting, flow cytometry, cell proliferation, cell signaling, and enzyme-linked immunosorbent assays.

RESULTS

Four anti-D_I+II and six anti-D_III+IV MAbs were obtained, selected based on their ability to bind recombinant full HER3 extracellular domain (ECD). Our data showed that only one anti-D_I+II and four anti-D_III+IV MAbs recognized the native form of HER3 by immunoblotting. Four MAbs recognized the membranous HER3 by flow cytometry leading to induction of different levels of receptor internalization and subsequent degradation. Results of cell proliferation assays using these MAbs indicated that they differentially inhibited proliferation of HER3-expressing cancer cells and showed considerable synergistic effects in combination with trastuzumab. Selected MAb with the highest inhibitory effect significantly inhibited the phosphorylation of AKT and ERK1/2 molecules.

CONCLUSION

Some of the anti-HER3 MAbs produced in this study displayed tumor inhibitory function and may be considered promising candidates for future HER3-targeted cancer therapy.

A human epidermal growth factor receptor 3/heregulin interaction inhibitor aptamer discovered using SELEX

The interaction of human epidermal growth factor receptor 3 (HER3) and heregulin (HRG) is involved in resistance to human epidermal growth factor receptor 2 (HER2)-targeted cancer treatment, such as therapies using anti-HER2 monoclonal antibody. Therefore, inhibition of the HER3/HRG interaction is potentially valuable therapeutic target for cancer treatment. In this study, we used in vitro selection, also known as systematic evolution of ligands by exponential enrichment (SELEX) against the extracellular domain of human HER3, and discovered a novel RNA aptamer. Pull-down and bio-layer interferometry assays showed that RNA aptamer discovered specifically bound to HER3 with a dissociation constant (K_D) of 700 nM. Pull-down assays using chemiluminescence detection also revealed that the HER3-binding RNA aptamer inhibited interactions between HER3 and human HRG. These results indicated that the novel HER3-binding RNA aptamer has potential to be used as basic tool in a range of applications involving HER3/HRG interactions, including research, therapeutic, and diagnostic applications.

A novel tumor inhibitory hybridoma monoclonal antibody with dual specificity for HER3 and HER2

BACKGROUND

The human epidermal growth factor receptor (HER/ErbB) family-targeted therapies result in a significant improvement in cancer immunotherapy. Monoclonal antibodies (MAb) against HER2 demonstrated a survival benefit for patients; however, drug resistance unavoidably occurs due to the overexpression of HER3, which leads to treatment failure. Effective inhibition of HER3 besides HER2 is thought to be required to overcome resistance and enhance therapeutic efficacy.

OBJECTIVE

The present study describes the production and characterization of a novel MAb, designated 1G5D2, which acts as a natural bispecific antibody targeting extracellular domains (ECD) of both HER2 and HER3.

METHODS

In this study, 1G5D2 was produced by hybridoma technology against HER3-ECD, and its structural and functional characteristics were studied by various methodologies, including enzyme linked-immunosorbent assays, flow cytometry, immunoblotting, cell signaling, and cell proliferation assays.

RESULTS

1G5D2 specifically binds to both HER2 (subdomain III + IV) and HER3 (subdomain I + II) expressed on tumor cells, and these receptors compete with each other for binding to this MAb. Competition flow cytometry experiments demonstrated that 1G5D2 does not compete with heregulin and recognizes an epitope out of HER3 ligand-binding site. Evaluation of 1G5D2 inhibitory effects in tumor cell lines co-expressing HER2 and HER3 showed that 1G5D2 synergizes with trastuzumab to inhibit both PI3K/AKT and MAPK/ERK pathways and potently downregulates the proliferation of these tumor cells more efficiently than each MAb alone.

CONCLUSION

1G5D2 is the first reported hybridoma antibody, which acts as a natural HER2/HER3 bispecific antibody. It might potentially be a suitable therapeutic candidate for HER2/HER3 overexpressing cancer types.

Embryonic lethality and defective mammary gland development of activator-function impaired conditional knock-in Erbb3 V943R mice

ERBB3 is a pseudokinase domain-containing member of the ERBB family of receptor tyrosine kinases (RTKs). Following ligand binding, ERBB receptors homo- or hetero-dimerize, leading to a head-to-tail arrangement of the intracellular kinase domains, where the "receiver" kinase domain of one ERBB is activated by the "activator" domain of the other ERBB in the dimer. In ERBB3, a conserved valine at codon 943 (V943) in the kinase C-terminal domain has been shown to be important for its function as an "activator" kinase in vitro. Here we report a knock-in mouse model where we have modified the endogenous Erbb3 allele to allow for tissue-specific conditional expression of Erbb3 ^V943R (Erbb3 ^CKI-V943R ). Additionally, we generated an Erbb3 ^D850N (Erbb3 ^CKI-D850N ) conditional knock-in mouse model where the conserved aspartate in the DFG motif of the pseudokinase domain was mutated to abolish any potential residual kinase activity. While Erbb3 ^D850N/D850N animals developed normally, homozygous Erbb3 ^V943R/V943R expression during development resulted in embryonic lethality. Further, tissue specific expression of Erbb3 ^V943R/V943R in the mammary gland epithelium following its activation using MMTV-Cre resulted in delayed elongation of the ductal network during puberty. Single-cell RNA-seq analysis of Erbb3 ^V943R/V943R mammary glands showed a reduction in a specific subset of fibrinogen-producing luminal epithelial cells.