Mechanisms of Receptor Tyrosine-Protein Kinase ErbB-3 (ERBB3) Action in Human Neoplasia

The role of MAPK, notch and Wnt signaling pathways in papillary thyroid cancer: Evidence from a systematic review and meta-analyzing microarray datasets employing bioinformatics knowledge and literature

Papillary thyroid cancer (PTC) is a prevalent kind of thyroid cancer (TC), with the risk of metastasis increasing faster than any other malignancy. So, understanding the role of PTC in pathogenesis requires studying the various gene expressions to find out which particular molecular biomarkers will be helpful. The authors conducted a comprehensive search on the PubMed microarray database and a meta-analysis approach on the remaining ones to determine the differentially expressed genes between PTC and normal tissues, along with the analyses of overall survival (OS) and recurrence-free survival (RFS) rates in patients with PTC. We considered the associated genes with MAPK, Wnt, and Notch signaling pathways. Two GEO datasets have been included in this research, considering inclusion and exclusion criteria. Nineteen genes were found to have higher differences through the meta-analysis procedure. Among them, ten genes were upregulated, and nine genes were downregulated. The expression of 19 genes was examined using the GEPIA2 database, and the Kaplan-Meier plot statistics were used to analyze RFS and the OS rates. We discovered seven significant genes with the validation: PRICKLE1, KIT, RPS6KA5, GADD45B, FGFR2, FGF7, and DTX4. To further explain these findings, it was discovered that the mRNA expression levels of these seven genes and the remaining 12 genes were shown to be substantially linked with the results of the experimental literature investigations on the PTC. Our research found nineteen panels of genes that could be involved in the PTC progression and metastasis and the immune system infiltration of these cancers.

Neural-specific alterations in glycosphingolipid biosynthesis and cell signaling associated with two human ganglioside GM3 synthase deficiency variants

GM3 Synthase Deficiency (GM3SD) is a neurodevelopmental disorder resulting from pathogenic variants in the ST3GAL5 gene, which encodes GM3 synthase, a glycosphingolipid (GSL)-specific sialyltransferase. This enzyme adds a sialic acid to the terminal galactose of lactosylceramide (LacCer) to produce the monosialylated ganglioside GM3. In turn, GM3 is extended by other glycosyltransferases to generate nearly all the complex gangliosides enriched in neural tissue. Pathogenic mechanisms underlying the neural phenotypes associated with GM3SD are unknown. To explore how loss of GM3 impacts neural-specific glycolipid glycosylation and cell signaling, GM3SD patient fibroblasts bearing one of two different ST3GAL5 variants were reprogrammed to induced pluripotent stem cells (iPSCs) and then differentiated to neural crest cells (NCCs). GM3 and GM3-derived gangliosides were undetectable in cells carrying either variant, while LacCer precursor levels were elevated compared to wildtype (WT). NCCs of both variants synthesized elevated levels of neutral lacto- and globo-series, as well as minor alternatively sialylated GSLs compared to WT. Ceramide profiles were also shifted in GM3SD variant cells. Altered GSL profiles in GM3SD cells were accompanied by dynamic changes in the cell surface proteome, protein O-GlcNAcylation, and receptor tyrosine kinase abundance. GM3SD cells also exhibited increased apoptosis and sensitivity to erlotinib-induced inhibition of epidermal growth factor receptor signaling. Pharmacologic inhibition of O-GlcNAcase rescued baseline and erlotinib-induced apoptosis. Collectively, these findings indicate aberrant cell signaling during differentiation of GM3SD iPSCs and also underscore the challenge of distinguishing between variant effect and genetic background effect on specific phenotypic consequences.

Expression of Soluble Form of Aurora A as a Predictive Factor for Neoadjuvant Therapy in Breast Cancer Patients: A Single-Center Pilot Study

PURPOSE

To search for new predictive breast cancer biomarkers. We analyzed the serum concentrations of biomarkers involved in carcinogenesis, which can also be targeted by therapy.

METHODS

In a single-center prospective study, the serum levels of Aurora A, thymidine kinase 1, and human epidermal growth factor receptor type 3 (HER3) were determined in 119 women with BC before neoadjuvant treatment using ELISA kits.

RESULTS

The following clinical data were analyzed: age; TNM; the expression of ER, PGR, HER2, and Ki67; histological grade (G); and the response to neoadjuvant treatment (NAT) in the residual tumor burden classification (RCB). A complete pathological response (pCR) was achieved after NAT in 41 patients (34%). The highest proportion of the patients with a confirmed pCR was found for triple negative breast cancer (TNBC) (62.5%); non-luminal HER2-positive (52.6%) cancer subtypes (p = 0.0003); and in the G3 group (50%; p = 0.0078). The patients with higher levels of Aurora A were more likely to achieve pCR (p = 0.039). In the multivariate analysis, the serum Aurora A levels ≥ 4.75 ng/mL correlated with a higher rate of pCR (OR: 3.5; 95% CI: 1.2-10.1; p = 0.023).

CONCLUSIONS

We showed that in a biologically heterogeneous group of BC patients, the pretreatment serum Aurora A levels were of significant value in predicting the response to NAT.

Dimethyl fumarate inhibits ZNF217 and can be beneficial in a subset of estrogen receptor positive breast cancers

PURPOSE

The oncogenic factor ZNF217 promotes aggressive estrogen receptor (ER)+breast cancer disease suggesting that its inhibition may be useful in the clinic. Unfortunately, no direct pharmacological inhibitor is available. Dimethyl fumarate (DMF) exhibits anti-breast cancer activities, in vitro and in pre-clinical in vivo models. Its therapeutic benefits stem from covalent modification of cellular thiols such as protein cysteines, but the full profile of molecular targets mediating its anti-breast cancer effects remains to be determined.

METHODS

ER+breast cancer cells were treated with DMF followed by cysteine-directed proteomics. Cells with modulated ZNF217 levels were used to probe the efficacy of DMF.

RESULTS

Covalent modification of ZNF217 by DMF identified by proteomics was confirmed by using a DMF-chemical probe. Inhibition of ZNF217's transcriptional activity by DMF was evident on reported ZNF217-target genes. ZNF217 as an oncogene has been shown to enhance stem-like properties, survival, proliferation, and invasion. Consistent with ZNF217 inhibition, DMF was more effective at blocking these ZNF217-driven phenotypes in cells with elevated ZNF217 expression. Furthermore, partial knockdown of ZNF217 led to a reduction in DMF's efficacy. DMF's in vivo activity was evaluated in a xenograft model of MCF-7 HER2 cells that have elevated expression of ZNF217 and DMF treatment resulted in significant inhibition of tumor growth.

CONCLUSION

These data indicate that DMF's anti-breast cancer activities in the ER+HER2+models, at least in part, are due to inhibition of ZNF217. DMF is identified as a new covalent inhibitor of ZNF217.

Dual targeting pH responsive chitosan nanoparticles for enhanced active cellular internalization of gemcitabine in non-small cell lung cancer

Lung cancer (LC), related with the enhanced expression of epidermal growth factor receptor (EGFR) and sialic acid binding receptors (glycan) brought about the development of EGFR and glycan receptor specific anticancer therapeutics. The current study assessed the formulation, physiochemical characterization, in vitro and in vivo effects of sialic acid (SA) and cetuximab (Cxmab) decorated chitosan nanoparticles (CSN-NPs) loaded with gemcitabine (GMC) targeted to glycan and EGFR over-expressing non-small-cell lung-cancer (NSCLC) A-549 cells. Chitosan (CSN) was conjugated with sialic acid via EDC/NHS chemistry followed by gemcitabine loaded sialic acid conjugated chitosan nanoparticles (GMC-CSN-SA-NPs) were prepared by ionic gelation method decorated with Cxmab by electrostatic interaction. In vitro cytotoxicity of NPs quantified using cell based MTT, DAPI and Annexing-V/PI apoptosis assays showed superior antiproliferative activity of targeted nanoformulations (GMC-CSN-SA-Cxmab-NPs ≫ GMC-CSN-SA-NPs, GMC-CSN-Cxmab-NPs) over non-targeted nanoformulation (GMC-CSN-NPs) against A-549 cells. In vivopharmacokinetic study showed superior bioavailability and in vivo therapeutic efficacy investigation exhibited strongest anticancer activity of glycan and EGFR targeted NPs (GMC-CSN-SA-Cxmab-NPs). GMC-CSN-SA-Cxmab-NPs demonstrated enhanced cellular internalization and better therapeutic potential, by specifically targeting glycan and EGFR on NSCLC A-549 cells and B[a]P induced lung cancer mice model, hence it might be a good substitute for non-targeted, conventional chemotherapy.

Inhibition of Erb-B2 Receptor Tyrosine Kinase 3 and Associated Regulatory Pathways Potently Impairs Malignant Peripheral Nerve Sheath Tumor Proliferation and Survival

Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive, currently untreatable Schwann cell-derived neoplasms with hyperactive mitogen-activated protein kinase and mammalian target of rapamycin signaling pathways. To identify potential therapeutic targets, previous studies used genome-scale shRNA screens that implicated the neuregulin-1 receptor erb-B2 receptor tyrosine kinase 3 (erbB3) in MPNST proliferation and/or survival. The current study shows that erbB3 is commonly expressed in MPNSTs and MPNST cell lines and that erbB3 knockdown inhibits MPNST proliferation and survival. Kinomic and microarray analyses of Schwann and MPNST cells implicate Src- and erbB3-mediated calmodulin-regulated signaling as key pathways. Consistent with this, inhibition of upstream (canertinib, sapitinib, saracatinib, and calmodulin) and parallel (AZD1208) signaling pathways involving mitogen-activated protein kinase and mammalian target of rapamycin reduced MPNST proliferation and survival. ErbB inhibitors (canertinib and sapitinib) or erbB3 knockdown in combination with Src (saracatinib), calmodulin [trifluoperazine (TFP)], or proviral integration site of Moloney murine leukemia kinase (AZD1208) inhibition even more effectively reduces proliferation and survival. Drug inhibition enhances an unstudied calmodulin-dependent protein kinase IIα phosphorylation site in an Src-dependent manner. The Src family kinase inhibitor saracatinib reduces both basal and TFP-induced erbB3 and calmodulin-dependent protein kinase IIα phosphorylation. Src inhibition (saracatinib), like erbB3 knockdown, prevents these phosphorylation events; and when combined with TFP, it even more effectively reduces proliferation and survival compared with monotherapy. These findings implicate erbB3, calmodulin, proviral integration site of Moloney murine leukemia kinases, and Src family members as important therapeutic targets in MPNSTs and demonstrate that combinatorial therapies targeting critical MPNST signaling pathways are more effective.

Cisplatin-induced increase in heregulin 1 and its attenuation by the monoclonal ErbB3 antibody seribantumab in bladder cancer

Cisplatin-based combination chemotherapy is the foundation for treatment of advanced bladder cancer (BlCa), but many patients develop chemoresistance mediated by increased Akt and ERK phosphorylation. However, the mechanism by which cisplatin induces this increase has not been elucidated. Among six patient-derived xenograft (PDX) models of BlCa, we observed that the cisplatin-resistant BL0269 express high epidermal growth factor receptor, ErbB2/HER2 and ErbB3/HER3. Cisplatin treatment transiently increased phospho-ErbB3 (Y1328), phospho-ERK (T202/Y204) and phospho-Akt (S473), and analysis of radical cystectomy tissues from patients with BlCa showed correlation between ErbB3 and ERK phosphorylation, likely due to the activation of ERK via the ErbB3 pathway. In vitro analysis revealed a role for the ErbB3 ligand heregulin1-β1 (HRG1/NRG1), which is higher in chemoresistant lines compared to cisplatin-sensitive cells. Additionally, cisplatin treatment, both in PDX and cell models, increased HRG1 levels. The monoclonal antibody seribantumab, that obstructs ErbB3 ligand-binding, suppressed HRG1-induced ErbB3, Akt and ERK phosphorylation. Seribantumab also prevented tumor growth in both the chemosensitive BL0440 and chemoresistant BL0269 models. Our data demonstrate that cisplatin-associated increases in Akt and ERK phosphorylation is mediated by an elevation in HRG1, suggesting that inhibition of ErbB3 phosphorylation may be a useful therapeutic strategy in BlCa with high phospho-ErbB3 and HRG1 levels.

Does EGFR Signaling Mediate Orexin System Activity in Sleep Initiation?

Sleep-wake cycle disorders are an important symptom of many neurological diseases, including Parkinson's disease, Alzheimer's disease, and multiple sclerosis. Circadian rhythms and sleep-wake cycles play a key role in maintaining the health of organisms. To date, these processes are still poorly understood and, therefore, need more detailed elucidation. The sleep process has been extensively studied in vertebrates, such as mammals and, to a lesser extent, in invertebrates. A complex, multi-step interaction of homeostatic processes and neurotransmitters provides the sleep-wake cycle. Many other regulatory molecules are also involved in the cycle regulation, but their functions remain largely unclear. One of these signaling systems is epidermal growth factor receptor (EGFR), which regulates the activity of neurons in the modulation of the sleep-wake cycle in vertebrates. We have evaluated the possible role of the EGFR signaling pathway in the molecular regulation of sleep. Understanding the molecular mechanisms that underlie sleep-wake regulation will provide critical insight into the fundamental regulatory functions of the brain. New findings of sleep-regulatory pathways may provide new drug targets and approaches for the treatment of sleep-related diseases.

Driver Mutations Dictate the Immunologic Landscape and Response to Checkpoint Immunotherapy of Glioblastoma

The composition of the tumor immune microenvironment (TIME) is considered a key determinant of patients' response to immunotherapy. The mechanisms underlying TIME formation and development over time are poorly understood. Glioblastoma (GBM) is a lethal primary brain cancer for which there are no curative treatments. GBMs are immunologically heterogeneous and impervious to checkpoint blockade immunotherapies. Utilizing clinically relevant genetic mouse models of GBM, we identified distinct immune landscapes associated with expression of EGFR wild-type and mutant EGFRvIII cancer driver mutations. Over time, accumulation of polymorphonuclear myeloid-derived suppressor cells (PMN-MDSC) was more pronounced in EGFRvIII-driven GBMs and was correlated with resistance to PD-1 and CTLA-4 combination checkpoint blockade immunotherapy. We determined that GBM-secreted CXCL1/2/3 and PMN-MDSC-expressed CXCR2 formed an axis regulating output of PMN-MDSCs from the bone marrow leading to systemic increase in these cells in the spleen and GBM tumor-draining lymph nodes. Pharmacologic targeting of this axis induced a systemic decrease in the numbers of PMN-MDSC, facilitated responses to PD-1 and CTLA-4 combination checkpoint blocking immunotherapy, and prolonged survival in mice bearing EGFRvIII-driven GBM. Our results uncover a relationship between cancer driver mutations, TIME composition, and sensitivity to checkpoint blockade in GBM and support the stratification of patients with GBM for checkpoint blockade therapy based on integrated genotypic and immunologic profiles.

Overexpression of ErbB-1 (EGFR) Protein in Eutopic Endometrium of Infertile Women with Severe Ovarian Endometriosis during the ‘Implantation Window’ of Menstrual Cycle

The strong association between endometriosis and infertility is of high clinical significance. High proliferative bias in eutopic endometrium during the secretory phase is a hallmark of endometriosis, which may result in high occurrence of implantation failure and resultant infertility in endometriosis. The ErbB family of proteins regulates the proliferation capacity in the endometrium, potentially causing endometrial hostility to the implantation process in endometriosis. However, our knowledge regarding the involvement of the ErbB family in human endometrium during the window of implantation (WOI) in endometriosis-associated infertility is scant. In the present study, the cellular profiles of immunopositive ErbBs-1 to -4 in the endometrium of endometriosis-free, infertile women (Group 1; n = 11) and in eutopic endometrium of infertile women diagnosed with stage IV ovarian endometriosis (Group 2; n = 13) during the mid-secretory phase were compared using standardized guidelines. Computer-aided standardized combinative analysis of immunoprecipitation in different compartments revealed an overexpression of ErbB-1 in the epithelial, stromal and vascular compartments, along with marginally higher ErbB-3 expression (p < 0.06) in the vascular compartment and ErbB-4 expression (p < 0.05) in the glandular epithelium and stroma in the endometrium during the WOI in women with primary infertility associated with stage IV ovarian endometriosis compared with disease-free endometrium of control infertile women. It appears that changes in ErbBs in the eutopic endometrium during WOI induce anomalous proliferative, inflammatory and angiogenic activities in it, which can antagonize endometrial preparation for embryo implantation in endometriosis. This knowledge appears usable in strategizing methods for the treatment of endometriosis-associated infertility, as well as preempting the oncogenic potential of endometriosis.

Pan-HER inhibitors overcome lorlatinib resistance caused by NRG1/HER3 activation in ALK-rearranged lung cancer

Lorlatinib, a third-generation anaplastic lymphoma kinase (ALK)-tyrosine kinase inhibitor (TKI) with a broad coverage against ALK mutations, has demonstrated dramatic effects in patients with ALK-rearranged lung cancer. The mechanisms of acquired resistance to lorlatinib by secondary ALK compound mutations have recently been reported; however, resistance mechanisms other than secondary mutations remain unclear. Here, we investigated the molecular mechanisms of the acquired resistance in ALK-rearranged lung cancer cells in vitro. We established two different lorlatinib-resistant ALK-rearranged lung cancer cell lines (H3122LR and A925LLR) via long-term administration of lorlatinib. These resistant cells did not harbor the secondary ALK mutations and showed cross-resistance to the other kinds of ALK-TKIs (crizotinib or alectinib) compared with the parental cells; however, these resistant cells overexpressed the phosphorylated human epidermal growth factor receptor 3 (HER3) protein and the ligand of HER3 (neuregulin 1; NRG1). Pharmacological inhibition of HER3 with pan-HER inhibitors or genetic knockdown of HER3 with siRNA resensitized H3122LR and A925LLR cells to lorlatinib in vitro, indicating that H3122LR and A925LLR acquired resistance by NRG1/HER3 activation. These findings demonstrated that targeting NRG1/HER3 is a potential novel therapeutic option for lorlatinib-resistant ALK-rearranged lung cancer.

Targeting HER3-dependent activation of nuclear AKT improves radiotherapy of non-small cell lung cancer

BACKGROUND

AKT1 must be present and activated in the nucleus immediately after irradiation to stimulate AKT1-dependent double-strand breaks (DSB) repair through the fast non-homologous end-joining (NHEJ) repair process. We investigated the subcellular distribution of AKT1 and the role of HER family receptor members on the phosphorylation of nuclear AKT and radiation response.

MATERIALS AND METHODS

Using genetic approaches and pharmacological inhibitors, we investigated the subcellular distribution of AKT1 and the role of HER family receptor members on the activation of nuclear AKT in non-small cell lung cancer (NSCLC) cells in vitro. ɤH2AX foci assay was applied to investigate the role of AKT activating signaling pathway on DSB repair. A mouse tumor xenograft model was used to study the impact of discovered signaling pathway activating nuclear AKT on the radiation response of tumors in vivo.

RESULTS

Our data suggests that neither ionizing radiation (IR) nor stimulation with HER family receptor ligands induced rapid nuclear translocation of endogenous AKT1. GFP-tagged exogenous AKT1 translocated to the nucleus under un-irradiated conditions and IR did not stimulate this translocation. Nuclear translocation of GFP-AKT1 was impaired by the AKT inhibitor MK2206 as shown by its accumulation in the cytoplasmic fraction. IR-induced phosphorylation of nuclear AKT was primarily dependent on HER3 expression and tyrosine kinase activation of epidermal growth factor receptor. In line with the role of AKT1 in DSB repair, the HER3 neutralizing antibody patritumab as well as HER3-siRNA diminished DSB repair in vitro. Combination of patritumab with radiotherapy improved the effect of radiotherapy on tumor growth delay in a xenograft model.

CONCLUSION

IR-induced activation of nuclear AKT occurs inside the nucleus that is mainly dependent on HER3 expression in NSCLC. These findings suggest that targeting HER3 in combination with radiotherapy may provide a logical treatment option for investigation in selected NSCLC patients.

Adult Wilms Tumor: Genetic Evidence of Origin of a Subset of Cases From Metanephric Adenoma

The genetics of nephroblastoma (Wilms tumor) occurring in adults is largely unknown, as studies have largely been limited to isolated case reports. We, therefore, studied 14 adult Wilms tumors for genetic alterations, using expanded targeted sequencing on 11 cases. The patients ranged from 17 to 46 years of age (mean and median, 31 y), and there were 8 males and 6 females. Five Wilms tumors harbored BRAF V600E mutations. All of these had better-differentiated areas identical to metanephric adenoma, as has previously been described. In 3 such cases, microdissection studies revealed that the BRAF V600E mutation was present in both the metanephric adenoma and Wilms tumor areas; however, additional genetic alterations (including TERT promoter mutations in 2 cases, ASLX1/ATR mutations in 1 other case) were limited to the Wilms tumor component. These findings suggest that the Wilms tumor developed from the metanephric adenoma. Other adult Wilms tumors harbored genetic alterations previously reported in the more common pediatric Wilms tumors, including WT1 mutations (2 cases), ASLX1 mutations (3 additional cases), NSD2 mutation (1 additional case), and 11p loss (3 cases). In summary, a significant subset of adult Wilms tumors (specifically those of epithelial type with differentiated areas) harbor targetable BRAF V600E mutations and appear to arise from metanephric adenomas as a consequence of additional acquired genetic alterations. Other adult Wilms tumors often harbor genetic alterations found in their more common pediatric counterparts, suggesting at least some similarities in their pathogenesis.

Targeting ErbB3 and Cellular NADPH/NADP+ Abundance Sensitizes Cutaneous Melanomas to Ferroptosis Inducers

Melanoma is a serious health challenge. Ferroptosis is a regulated form of oxidative cell death that shows varied efficacy in melanoma. We aimed to better understand the molecular basis for this differential ferroptosis sensitivity. We find that elevated expression of ErbB3 (V-Erb-B2 Avian Erythroblastic Leukemia Viral Oncogene Homologue 3) associates with ferroptosis resistance and that ErbB3 knockdown sensitizes to ferroptosis inducers. ErbB3 depletion also promotes a marked reduction in the cellular ratio of GSH/GSSG (reduced/oxidized glutathione) and that of NADPH/NADP+ (reduced/oxidized nicotinamide adenine dinucleotide phosphate), together with an increase in the abundance of the lipid peroxidation product malondialdehyde (MDA). We identify several small molecule inhibitors targeting ErbB3 signaling pathways that also reduce the NADPH/NADP+ and GSH/GSSG ratios, concomitantly sensitizing the melanomas to ferroptosis activators. These findings point to a previously unrecognized role of ErbB3 in ferroptosis sensitivity and provide new insight into pathways that regulate this cell death process.

Recent advances and limitations in the application of kahalalides for the control of cancer

Since the discovery of the kahalalide family of marine depsipeptides in 1993, considerable work has been done to develop these compounds as new and biologically distinct anti-cancer agents. Clinical trials and laboratory research have yielded a wealth of data that indicates tolerance of kahalalides in healthy cells and selective activity against diseased cells. Currently, two molecules have attracted the greates level of attention, kahalalide F (KF) and isokahalalide F (isoKF, Irvalec, PM 02734, elisidepsin). Both compounds were originally isolated from the sarcoglossan mollusk Elysia rufescens but due to distinct structural characteristics it has been hypothesized and recently shown that the ultimate origin of the molecules is microbial. The search for their true source has been a subject of considerable research in the anticipation of finding new analogs and a culturable expression system that can produce sufficient material through fermentation to be industrially relevant.

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.

The Yin and Yang of ERBB4: Tumor Suppressor and Oncoprotein

ERBB4 (HER4) is a member of the ERBB family of receptor tyrosine kinases, a family that includes the epidermal growth factor receptor (EGFR/ERBB1/HER1), ERBB2 (Neu/HER2), and ERBB3 (HER3). EGFR and ERBB2 are oncoproteins and validated targets for therapeutic intervention in a variety of solid tumors. In contrast, the role that ERBB4 plays in human malignancies is ambiguous. Thus, here we review the literature regarding ERBB4 function in human malignancies. We review the mechanisms of ERBB4 signaling with an emphasis on mechanisms of signaling specificity. In the context of this signaling specificity, we discuss the hypothesis that ERBB4 appears to function as a tumor suppressor protein and as an oncoprotein. Next, we review the literature that describes the role of ERBB4 in tumors of the bladder, liver, prostate, brain, colon, stomach, lung, bone, ovary, thyroid, hematopoietic tissues, pancreas, breast, skin, head, and neck. Whenever possible, we discuss the possibility that ERBB4 mutants function as biomarkers in these tumors. Finally, we discuss the potential roles of ERBB4 mutants in the staging of human tumors and how ERBB4 function may dictate the treatment of human tumors. SIGNIFICANCE STATEMENT: This articles reviews ERBB4 function in the context of the mechanistic model that ERBB4 homodimers function as tumor suppressors, whereas ERBB4-EGFR or ERBB4-ERBB2 heterodimers act as oncogenes. Thus, this review serves as a mechanistic framework for clinicians and scientists to consider the role of ERBB4 and ERBB4 mutants in staging and treating human tumors.

ERBB Signaling Pathway in Cancer Stem Cells

The epidermal growth factor receptor (EGFR) was first tyrosine kinase receptor linked to human cancers. EGFR or ERBB1 is a member of ERBB subfamily, which consists of four type I transmembrane receptor tyrosine kinases, ERBB1, 2, 3 and 4. ERBBs form homo/heterodimers after ligand binding except ERBB2 and consequently becomes activated. Different signal pathways, such as phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT), RAS/RAF/MEK/ERK, phospholipase Cγ and JAK-STAT, are triggered by ERBB activation. Since ERBBs, through these pathways, regulate stemness and differentiation of cancer stem cells (CSCs), their roles in CSC tumorigenicity have extensively been investigated. The hyperactivation of ERBBs and its downstream pathways stimulated by either genetic and/or epigenetic factors are frequently described in many types of human cancers. Their dysregulations make cells acquiring CSC characters such as survival, tumorigenicity and stemness. Because of the roles in tumor growth and progress, ERBBs are considered to be one of the drug targets as cancer treatment strategy. In this chapter, we will summarize the structure, function and roles of ERBB subfamily along with their relative pathways regulating the stemness and tumorigenicity of CSCs. Finally, we will discuss the targeting therapy strategies of cancer along with ERBBs in addition to some challenges and future perspectives.

Glycosylation promotes the cancer regulator EGFR-ErbB2 heterodimer formation - molecular dynamics study

ErbB family of receptor tyrosine kinases play significant roles in cellular differentiation and proliferation. Mutation or overexpression of these receptors leads to several cancers in humans. The family has four homologous members including EGFR, ErbB2, ErbB3, and ErbB4. From which all except the ErbB2 bind to growth factors via the extracellular domain to send signals to the cell. However, dimerization of the ErbB receptor occurs in extracellular, transmembrane, and intracellular domains. The ErbB receptors are known to form homodimers and heterodimers in the active form. Heterodimerization increases the variety of identified ligands and signaling pathways that can be activated by these receptors. Furthermore, glycosylation of the ErbB receptors has shown to be critical for their stability, ligand binding, and dimerization. Here, atomistic molecular dynamics simulations on the glycosylated and unglycosylated heterodimer showed that the EGFR-ErbB2 heterodimer is more stable in its dynamical pattern compared to the EGFR-EGFR homodimer. This increased stability is regulated by maintaining the dimeric interface by the attached glycans. It was also shown that the presence of various glycosylation sites within the ErbB2 growth factor binding site leads to occlusion of this site by the glycans that inhibit ligand binding to ErbB2 and participate in further stabilization of the heterodimer construct. Putting together, glycosylation seems to promote the heterodimer formation within the ErbB family members as the dominant molecular mechanism of activation for these receptors.

ErbB3 is a critical regulator of cytoskeletal dynamics in brain microvascular endothelial cells: Implications for vascular remodeling and blood brain barrier modulation

Neuregulin (NRG)1 - ErbB receptor signaling has been shown to play an important role in the biological function of peripheral microvascular endothelial cells. However, little is known about how NRG1/ErbB signaling impacts brain endothelial function and blood-brain barrier (BBB) properties. NRG1/ErbB pathways are affected by brain injury; when brain trauma was induced in mice in a controlled cortical impact model, endothelial ErbB3 gene expression was reduced to a greater extent than that of other NRG1 receptors. This finding suggests that ErbB3-mediated processes may be significantly compromised after injury, and that an understanding of ErbB3 function would be important in the of study of endothelial biology in the healthy and injured brain. Towards this goal, cultured brain microvascular endothelial cells were transfected with siRNA to ErbB3, resulting in alterations in F-actin organization and microtubule assembly, cell morphology, migration and angiogenic processes. Importantly, a significant increase in barrier permeability was observed when ErbB3 was downregulated, suggesting ErbB3 involvement in BBB regulation. Overall, these results indicate that neuregulin-1/ErbB3 signaling is intricately connected with the cytoskeletal processes of the brain endothelium and contributes to morphological and angiogenic changes as well as to BBB integrity.

The Radiolabeled HER3 Targeting Molecules for Tumor Imaging

The human epidermal growth factor receptor (HER) family plays pivotal roles in physiologic and pathologic conditions (such as tumor growth, proliferation, and progression in multiple epithelial malignancies). All the family members are considered tyrosine kinase, while HER3 as a member of this family shows no intrinsic tyrosine kinase. HER3 is called ‘pseudokinase’ because it undergoes heterodimerization and forms dimers such as HER2-HER3 and HER1 (EGFR)-HER3. The exact role of HER3 in cancer is still unclear; however, the overexpression of this receptor is involved in the poor prognosis of malignancies. To that end, different studies investigated the development of radiotracers for imaging of HER3. The main focus of this review is to gather all the studies on developing new radiotracers for imaging of HER3.

EV20/NMS-P945, a Novel Thienoindole Based Antibody-Drug Conjugate Targeting HER-3 for Solid Tumors

HER-3 is becoming an attractive target for antibody-drug conjugate (ADC)-based therapy. Indeed, this receptor and its ligands are found to be overexpressed in several malignancies, and re-activation of its downstream signaling axis is known to play a critical role in modulating the sensitivity of targeted therapeutics in different tumors. In this study, we generated a novel ADC named EV20/NMS-P945 by coupling the anti-HER-3 antibody EV20 with a duocarmycin-like derivative, the thienoindole (TEI) NMS-P528, a DNA minor groove alkylating agent through a peptidic cleavable linker. This ADC showed target-dependent cytotoxic activity in vitro on several tumor cell lines and therapeutic activity in mouse xenograft tumor models, including those originating from pancreatic, prostatic, head and neck, gastric and ovarian cancer cells and melanoma. Pharmacokinetics and toxicological studies in monkeys demonstrated that this ADC possesses a favorable terminal half-life and stability and it is well tolerated. These data support further EV20/NMS-P945 clinical development as a therapeutic agent against HER-3-expressing malignancies.

The Clinical Role of Serum Epidermal Growth Factor Receptor 3 in Hepatitis C Virus-Infected Patients with Early Hepatocellular Carcinoma

Simple Summary

The identification of diagnostic and prognostic biomarkers for the management of patients with hepatocellular carcinoma is an unmet need. Here we investigate the potential clinical utility of the measurement of serum epidermal growth factor receptor 3 (i.e., ERBB3) in hepatitis C virus-infected patients with early hepatocellular carcinoma. Median values of serum ERBB3 were similar between patients with cirrhosis and those with early hepatocellular carcinoma (HCC); therefore, the measurement of the biomarker in the setting of HCC surveillance appeared unsuitable. Conversely, in patients with early HCC, serum ERBB3 values were significantly associated with overall survival, suggesting that the biomarker may be useful to tailor appropriate treatment strategies in hepatitis C virus (HCV)-infected patients with early hepatocellular carcinoma.

Abstract

Epidermal growth factor receptor 3 (ERBB3) is a surface tyrosine kinase receptor belonging to the EGFR/ERBB family, involved in tumor development and progression. We evaluated the diagnostic and prognostic value of serum ERBB3 measurement in hepatitis C virus (HCV)-infected patients with early hepatocellular carcinoma (HCC). A total of 164 HCV-infected patients (82 with cirrhosis and 82 with early HCC) were included in the study. HCC was classified according to the Barcelona Clinic Liver Cancer (BCLC) staging system. Among patients with HCC, 23 (28%) had a diagnosis of very early tumor (BCLC = 0), while 59 (62%) had a diagnosis of early HCC (BCLC = A). Median overall survival (OS) in patients with HCC was 79.2 (95% CI 51.6–124.8) months. While ERBB3 serum values were similar between patients with cirrhosis and those with HCC (p = 0.993), in the latter, serum ERBB3 ≥ 2860 RU resulted significantly and independently associated with OS (Hazard Ratio = 2.24, 95% CI 1.16–4.35, p = 0.017). Consistently, the 1-, 3-, and 5-year OS rates in patients with serum ERBB3 ≥ 2860 RU were 90% (36/40), 53% (19/36), and 28% (8/29) in comparison to patients with serum ERBB3 < 2860 RU, which were 98% (40/41), 80% (32/40), and 74% (26/35) (Log-rank test; p = 0.014). In conclusion, serum ERBB3 values resulted an independent prognostic factor of patients with early HCC and might be useful to tailor more personalized treatment strategies.

Cell-to-cell diversification in ERBB-RAS-MAPK signal transduction that produces cell-type specific growth factor responses

Growth factors regulate cell fates, including their proliferation, differentiation, survival, and death, according to the cell type. Even when the response to a specific growth factor is deterministic for collective cell behavior, significant levels of fluctuation are often observed between single cells. Statistical analyses of single-cell responses provide insights into the mechanism of cell fate decisions but very little is known about the distributions of the internal states of cells responding to growth factors. Using multi-color immunofluorescent staining, we have here detected the phosphorylation of seven elements in the early response of the ERBB-RAS-MAPK system to two growth factors. Among these seven elements, five were analyzed simultaneously in distinct combinations in the same single cells. Although principle component analysis suggested cell-type and input specific phosphorylation patterns, cell-to-cell fluctuation was large. Mutual information analysis suggested that each cell type uses multitrack (bush-like) signal transduction pathways under conditions in which clear fate changes have been reported. The clustering of single-cell response patterns indicated that the fate change in a cell population correlates with the large entropy of the response, suggesting a bet-hedging strategy is used in decision making. A comparison of true and randomized datasets further indicated that this large variation is not produced by simple reaction noise, but is defined by the properties of the signal-processing network.

Neoadjuvant chemotherapy promotes the expression of HER3 in patients with ovarian cancer

HER3 (erbB3) signaling serves an important role in the development and chemoresistance of ovarian cancer, and is activated by chemotherapy. To evaluate the influence of neoadjuvant chemotherapy and other clinical factors on the expression of HER3, as well as to examine its role as a prognostic marker, the present study evaluated archived tissues from patients who underwent surgery for ovarian cancer between 2011 and 2018 at our hospital. Immunohistochemical staining for HER3 was performed using formalin-fixed paraffin-embedded surgical specimens and biopsy samples. In total, data from 111 patients with sufficient surgically resected tumor samples were extracted. A total of 28 patients with histology type high-grade serous carcinoma (HGSC) had specimens available from both pre-chemotherapy biopsies and post-chemotherapy surgery. High HER3 expression (HER3-high) was observed in 64 patients (58%), whereas low HER3 expression (HER3-low) was observed in 47 patients (42%). Multivariate logistic regression analysis identified neoadjuvant chemotherapy [odds ratio (OR), 7.49; 95% confidence interval (CI), 2.48–22.64; P<0.001) and non-HGSC histology (OR, 5.42; 95% CI, 1.99–14.78; P<0.001) as significant predictive factors for HER3-high. In pre-chemotherapy biopsy specimens, 15 patients were HER3-high and 13 were HER3-low. After chemotherapy, eight of 13 patients with HER3-low exhibited a change in status to HER3-high, with a trend toward poorer progression-free survival compared to that of patients whose status remained HER3-low. In conclusion, HER3 overexpression was revealed to be common among patients with ovarian cancer, especially in those with non-HGSC histology. In addition, HER3 expression may be promoted by chemotherapy. These findings suggested that patients with ovarian cancer are good candidates for emerging HER3-targeting therapies.

Role of EGFR in the Nervous System

Epidermal growth factor receptor (EGFR) is the first discovered member of the receptor tyrosine kinase superfamily and plays a fundamental role during embryogenesis and in adult tissues, being involved in growth, differentiation, maintenance and repair of various tissues and organs. The role of EGFR in the regulation of tissue development and homeostasis has been thoroughly investigated and it has also been demonstrated that EGFR is a driver of tumorigenesis. In the nervous system, other growth factors, and thus other receptors, are important for growth, differentiation and repair of the tissue, namely neurotrophins and neurotrophins receptors. For this reason, for a long time, the role of EGFR in the nervous system has been underestimated and poorly investigated. However, EGFR is expressed both in the central and peripheral nervous systems and it has been demonstrated to have specific important neurotrophic functions, in particular in the central nervous system. This review discusses the role of EGFR in regulating differentiation and functions of neurons and neuroglia. Furthermore, its involvement in regeneration after injury and in the onset of neurodegenerative diseases is examined.

Analysis of expression of candidate genes for polycystic ovary syndrome in adult and fetal human and fetal bovine ovaries†

Polycystic ovary syndrome (PCOS) appears to have a genetic predisposition and a fetal origin. We compared the expression levels of 25 PCOS candidate genes from adult control and PCOS human ovaries (n = 16) using microarrays. Only one gene was potentially statistically different. Using qRT-PCR, expression of PCOS candidate genes was examined in bovine fetal ovaries from early stages when they first developed stroma through to completion of development (n = 27; 60-270 days of gestation). The levels of ERBB3 mRNA negatively correlated with gestational age but positively with HMGA2, FBN3, TOX3, GATA4, and DENND1A.X1,2,3,4, previously identified as correlated with each other and expressed early. PLGRKT and ZBTB16, and less so IRF1, were also correlated with AMH, FSHR, AR, INSR, and TGFB1I1, previously identified as correlated with each other and expressed late. ARL14EP, FDFT1, NEIL2, and MAPRE1 were expressed across gestation and not correlated with gestational age as shown previously for THADA, ERBB4, RAD50, C8H9orf3, YAP1, RAB5B, SUOX, and KRR1. LHCGR, because of its unusual bimodal expression pattern, had some unusual correlations with other genes. In human ovaries (n = 15; <150 days of gestation), ERBB3.V1 and ERBB3.VS were expressed and correlated negatively with gestational age and positively with FBN3, HMGA2, DENND1A.V1,3,4, DENND1A.V1-7, GATA4, and FSHR, previously identified as correlated with each other and expressed early. Thus, the general lack of differential expression of candidate genes in adult ovaries contrasting with dynamic patterns of gene expression in fetal ovaries is consistent with a vulnerability to disturbance in the fetal ovary that may underpin development of PCOS.

Anti-EGFR therapy in metastatic colorectal cancer: mechanisms and potential regimens of drug resistance

Cetuximab and panitumumab, as the highly effective antibodies targeting epidermal growth factor receptor (EGFR), have clinical activity in the patients with metastatic colorectal cancer (mCRC). These agents have good curative efficacy, but drug resistance also exists at the same time. The effects of KRAS, NRAS, and BRAF mutations and HER2 amplification on the treatment of refractory mCRC have been elucidated and the corresponding countermeasures have been put forward. However, the changes in EGFR and its ligands, the mutations or amplifications of PIK3CA, PTEN, TP53, MET, HER3, IRS2, FGFR1, and MAP2K1, the overexpression of insulin growth factor-1, the low expression of Bcl-2-interacting mediator of cell death, mismatch repair-deficient, and epigenetic instability may also lead to drug resistance in mCRC. Although the emergence of drug resistance has genetic or epigenetic heterogeneity, most of these molecular changes relating to it are focused on the key signaling pathways, such as the RAS/RAF/mitogen-activated protein kinase or phosphatidylinositol 3-kinase/Akt/mammalian target of the rapamycin pathway. Accordingly, numerous efforts to target these signaling pathways and develop the novel therapeutic regimens have been carried out. Herein, we have reviewed the underlying mechanisms of the resistance to anti-EGFR therapy and the possible implications in clinical practice.

HER3 targeting with an antibody-drug conjugate bypasses resistance to anti-HER2 therapies

Despite impressive clinical benefit obtained with anti‐HER2‐targeted therapies, in advances stages, especially in the metastatic setting, HER2‐positive tumors remain incurable. Therefore, it is important to develop novel strategies to fight these tumors, especially when they become resistant to available therapies. We show here that the anti‐HER3 antibody–drug conjugate EV20/MMAF exerted potent anti‐tumoral properties against several models of primary resistance and secondary resistance to common anti‐HER2 available therapies, including trastuzumab, lapatinib, neratinib, and trastuzumab‐emtansine. HER3 was expressed in these HER2⁺ breast cancer cells and knockdown experiments demonstrated that HER3 expression was required for the action of EV20/MMAF. In mice injected with trastuzumab‐resistant HER2⁺ cells, a single dose of EV20/MMAF caused complete and long‐lasting tumor regression. Mechanistically, EV20/MMAF bound to cell surface HER3 and became internalized to the lysosomes. Treatment with EV20/MMAF caused cell cycle arrest in mitosis and promoted cell death through mitotic catastrophe. These findings encourage the clinical testing of EV20/MMAF for several indications in the HER2⁺ cancer clinic, including situations in which HER2⁺ tumors become refractory to approved anti‐HER2 therapies.

Neuropeptide bombesin receptor activation stimulates growth of lung cancer cells through HER3 with a MAPK-dependent mechanism

Despite recent advances in treatment of non-small cell lung cancer (NSCLC), prognosis still remains poor and new therapeutic approaches are needed. Studies demonstrate the importance of the EGFR/HER-receptor family in NSCLC growth, as well as that of other tumors. Recently, HER3 is receiving increased attention because of its role in drug resistance and aggressive growth. Activation of overexpressed G-protein-coupled receptors (GPCR) can also initiate growth by transactivating EGFR/HER-family members. GPCR transactivation of EGFR has been extensively studied, but little is known of its ability to transactivate other EGFR/HER-members, especially HER3. To address this, we studied the ability of bombesin receptor (BnR) activation to transactivate all EGFR/HER-family members and their principal downstream signaling cascades, the PI3K/Akt- and MAPK/ERK-pathways, in human NSCLC cell-lines. In all three cell-lines studied, which possessed EGFR, HER2 and HER3, Bn rapidly transactivated EGFR, HER2 and HER3, as well as Akt and ERK. Immunoprecipitation studies revealed Bn-induced formation of both HER3/EGFR- and HER3/HER2-heterodimers. Specific EGFR/HER3 antibodies or siRNA-knockdown of EGFR and HER3, demonstrated Bn-stimulated activation of EGFR/HER members is initially through HER3, not EGFR. In addition, specific inhibition of HER3, HER2 or MAPK, abolished Bn-stimulated cell-growth, while neither EGFR nor Akt inhibition had an effect. These results show HER3 transactivation mediates all growth effects of BnR activation through MAPK. These results raise the possibility that targeting HER3 alone or with GPCR activation and its signal cascades, may be a novel therapeutic approach in NSCLC. This is especially relevant with the recent development of HER3-blocking antibodies.