Oligoclonal antibodies to target the ErbB family

INTRODUCTION

Use of mAbs to inhibit signaling through the ErbB receptor tyrosine kinase family has proven to be an effective strategy for treating ErbB-driven cancers. Advances in the field of antibody engineering and manufacturing now allow us to more effectively mimic the natural immune response by generating oligoclonal mixtures of antibodies against desired targets of interest.

AREAS COVERED

In this review, we examine the literature describing the development of oligoclonal mixtures of antibodies against ErbB family members and the impact of those mixtures on preclinical and clinical efficacy.

EXPERT OPINION

Oligoclonal antibodies, facilitated by the improved antibody engineering and manufacturing techniques, hold the promise of improving patient outcomes. Through the use of empirical methods, oligoclonal mixtures with enhanced capacity to block signaling through ErbB family members can be identified. The intrinsic mechanisms associated with each of the component mAbs provide an opportunity to block signaling via multiple mechanisms of action. In addition, combinations of antibodies targeting multiple ErbB family members provide the capacity to down-regulate signaling through multiple components of this critical pathway.

The challenge of blocking a wider family members of EGFR against head and neck squamous cell carcinomas

Head and neck squamous cell carcinoma (HNSCC) represent 95% of head and neck cancer with an incidence of over half a million people globally. The prognosis for patients with recurrent or metastatic HNSCC is generally poor with low 5-year survival rates despite treatment advances over the past few decades. Consequently, it is essential to search for new biomarkers and effective therapy options to optimize HNSCC treatment. Epidermal growth factor receptor (EGFR) is overexpressed in approximately 90% of tumours. EGFR has become one of most common targets for new therapies being investigated in HNSCC. In this way, multiple therapies targeting EGFR in HNSCC have been tested but response rates are still low especially in the recurrent or metastatic setting. This has been attributed to mechanisms of resistance to EGFR-targeted therapies. Afatinib, an oral small molecule ErbB Family Blocker that irreversibly binds to ErbB1 (EGFR), ErbB2 (HER2) and ErbB4 (HER4), is being investigated in HNSCC treatment with encouraging phase II results and several ongoing phase III trials. Results of these trials will help to understand the place of afatinib in the HNSCC treatment armamentarium.

Phase II study of afatinib, an irreversible ErbB family blocker, in demographically and genotypically defined lung adenocarcinoma

OBJECTIVES

Afatinib, an oral irreversible ErbB family blocker, has demonstrated efficacy in patients with epidermal growth factor receptor (EGFR) mutation-positive advanced lung adenocarcinoma. Other potential biomarkers predicting response to afatinib, such as human epidermal growth factor receptor-2 (HER2) mutations and EGFR gene amplification, have not been validated yet. This phase II study investigated whether afatinib conferred clinical benefit in cohorts of adenocarcinoma patients with: (1) EGFR mutation and failing on erlotinib/gefitinib; or (2) increased copy number of EGFR by fluorescence in situ hybridization (FISH); or (3) HER2 mutation.

MATERIALS AND METHODS

Patients started daily afatinib 50mg monotherapy. Upon disease progression, patients could continue, at the investigator's discretion, afatinib (40mg) with the addition of paclitaxel (80mg/m(2) weekly for 3 weeks/4-week cycle). Endpoints included confirmed objective response (OR), progression-free survival (PFS), disease control, and safety.

RESULTS

Of 41 patients treated (cohort 1: n=32; cohort 2: n=2; cohort 3: n=7), 33 received afatinib monotherapy; eight subsequently received afatinib plus paclitaxel. With afatinib monotherapy, one patient achieved a confirmed OR (partial response [PR]; cohort 2). Two further patients achieved unconfirmed PRs (one each in cohort 1 and cohort 3). Disease control was achieved by 17/32 (53%), 2/2 (100%) and 5/7 (71%) patients in cohorts 1, 2 and 3, respectively. In patients receiving combination therapy (median PFS: 6.7 weeks), one (cohort 3) had confirmed PR of 41.9 weeks. The most common afatinib-related adverse events were diarrhea (95%) and rash/acne (80%).

CONCLUSION

Afatinib demonstrated signs of clinical activity in heavily pretreated patients with activating HER2 or EGFR mutations or EGFR FISH-positive tumors.

The Src homology and collagen A (ShcA) adaptor protein is required for the spatial organization of the costamere/Z-disk network during heart development

Src homology and collagen A (ShcA) is an adaptor protein that binds to tyrosine kinase receptors. Its germ line deletion is embryonic lethal with abnormal cardiovascular system formation, and its role in cardiovascular development is unknown. To investigate its functional role in cardiovascular development in mice, ShcA was deleted in cardiomyocytes and vascular smooth muscle cells by crossing ShcA flox mice with SM22a-Cre transgenic mice. Conditional mutant mice developed signs of severe dilated cardiomyopathy, myocardial infarctions, and premature death. No evidence of a vascular contribution to the phenotype was observed. Histological analysis of the heart revealed aberrant sarcomeric Z-disk and M-band structures, and misalignments of T-tubules with Z-disks. We find that not only the ErbB3/Neuregulin signaling pathway but also the baroreceptor reflex response, which have been functionally associated, are altered in the mutant mice. We further demonstrate that ShcA interacts with Caveolin-1 and the costameric protein plasma membrane Ca(2+)/calmodulin-dependent ATPase (PMCA), and that its deletion leads to abnormal dystrophin signaling. Collectively, these results demonstrate that ShcA interacts with crucial proteins and pathways that link Z-disk and costamere.

Regulation of sonic hedgehog expression by integrin β1 and epidermal growth factor receptor in intestinal epithelium

We previously found that conditional deletion of integrin β1 in intestinal epithelium of mice caused early postnatal lethality and intestinal phenotypic changes including excessive proliferation and defective differentiation of intestinal epithelium due to loss of Hedgehog expression. Here, we link these defects to the Hedgehog (Hh) signaling pathway and show that loss of integrin β1 leads to excessive phosphorylation of MEK-1 and increased expression of ErbB receptors, including the epidermal growth factor receptor (EGFR). We show that increased EGFR signaling attenuates Hh abundance and that an EGFR inhibitor rescues conditional β1 integrin null pups from postnatal lethality. These studies link the loss of Hh expression in the intestinal epithelium of integrin β1-deficient mice to excessive EGFR/MAPK signaling, and identify a unique mechanism for crosstalk between stromal and epithelial signaling pathways that is critical for intestinal epithelial differentiation and function.

Dihydrotestosterone potentiates EGF-induced ERK activation by inducing SRC in fetal lung fibroblasts

Lung maturation is regulated by interactions between mesenchymal and epithelial cells, and is delayed by androgens. Fibroblast-Type II cell communications are dependent on extracellular signal-regulated kinases (ERK) 1/2 activation by the ErbB receptor ligands epidermal growth factor (EGF), transforming growth factor (TGF)-α, and neuregulin (Nrg). In other tissues, dihydrotestosterone (DHT) has been shown to activate SRC by a novel nontranscriptional mechanism, which phosphorylates EGF receptors to potentiate EGF-induced ERK1/2 activation. This study sought to determine if DHT potentiates EGFR signaling by a nontranscriptional mechanism. Embryonic day (E)17 fetal lung cells were isolated from dams treated with or without DHT since E12. Cells were exposed to 30 ng/ml DHT for periods of 30 minutes to 3 days before being stimulated with 100 ng/ml EGF, TGF-α, or Nrg for up to 30 minutes. Lysates were immunoblotted for ErbB and SRC pathway signaling intermediates. DHT increased ERK1/2 activation by EGF, TGF-α, and Nrg in fibroblasts and Type II cells. Characterization in fibroblasts showed that potentiation of the EGF pathway was significant after 60 minutes of DHT exposure and persisted in the presence of the translational inhibitor cycloheximide. SRC and EGF receptor phosphorylation was increased by DHT, as was EGF-induced SHC1 phosphorylation and subsequent association with GRB2. Finally, SRC silencing, SRC inhibition with PP2, and overexpression of a dominant-negative SRC each prevented DHT from increasing EGF-induced ERK1/2 phosphorylation. These results suggest that DHT activates SRC to potentiate the signaling pathway leading from the EGF receptor to ERK activation in primary fetal lung fibroblasts.

ErbB targeting inhibitors repress cell migration of esophageal squamous cell carcinoma and adenocarcinoma cells by distinct signaling pathways

ErbB family receptor tyrosine kinases (ErbBs) play a role in cell adhesion and migration and are frequently overexpressed in esophageal squamous cell carcinomas (ESCCs) or esophageal adenocarcinomas (EACs). Targeting ErbBs by tyrosine kinase inhibitors (TKIs) may therefore limit esophageal cancer cell migration. Here, we studied the impact of TKIs on ErbB dimerization, cell signaling pathways, and cell migration in three esophageal cell lines: OE21 (ESCC), OE33 (EAC), and Het-1A (non-neoplastic esophageal epithelium). In OE21 cells, the TKIs erlotinib, gefitinib, and lapatinib slightly affected epidermal growth factor receptor EGFR/EGFR, but not EGFR/HER2 dimerization as detected by in situ proximity ligation assay (in situ PLA). Still, TKIs inhibited ERK1/2, Akt, STAT3, and RhoA activity in OE21 cells, as assessed by Western blot, antibody arrays, and Rho GTPase effector pull-down assays. This was accompanied by reduced OE21 cell migration, induction of focal adhesions, and actin cytoskeleton reorganization, as shown by Oris™ migration assay and focal adhesion kinase (FAK)/phalloidin staining. In contrast, in OE33 cells, only lapatinib decreased STAT5, Src family kinase (SFK), and FAK activity as well as β-catenin expression. This impeded cell migration and induced morphological changes in OE33 cells. No alterations were seen for the non-neoplastic Het-1A cells. Thus, we identified the ErbB signaling network as regulator of esophageal cancer cell's actin cytoskeleton, focal adhesions, and cell migration. ErbB targeted TKIs therefore also limit ESCC and EAC cell motility and migration.

KEY MESSAGE

Clinical tyrosine kinase inhibitors (TKIs) reduce esophageal cancer cell migration. Loss of cell migration is linked to reduced Akt, ERK1/2, STAT (3 or 5), FAK, SFKs, and RhoA activity. Clinical TKIs act via distinct signaling in the two main histotypes of esophageal cancer.

Signalling between microvascular endothelium and cardiomyocytes through neuregulin

Heterocellular communication in the heart is an important mechanism for matching circulatory demands with cardiac structure and function, and neuregulins (Nrgs) play an important role in transducing this signal between the hearts' vasculature and musculature. Here, we review the current knowledge regarding Nrgs, explaining their roles in transducing signals between the heart's microvasculature and cardiomyocytes. We highlight intriguing areas being investigated for developing new, Nrg-mediated strategies to heal the heart in acquired and congenital heart diseases, and note avenues for future research.

A bispecific transmembrane antibody simultaneously targeting intra- and extracellular epitopes of the epidermal growth factor receptor inhibits receptor activation and tumor cell growth

Epidermal growth factor receptor (EGFR) plays an important role in essential cellular processes such as proliferation, survival and migration. Aberrant activation of EGFR is frequently found in human cancers of various origins and has been implicated in cancer pathogenesis. The therapeutic antibody cetuximab (Erbitux) inhibits tumor growth by binding to the extracellular domain of EGFR, thereby preventing ligand binding and receptor activation. This activity is shared by the single chain antibody fragment scFv(225) that contains the same antigen binding domain. The unrelated EGFR-specific antibody fragment scFv(30) binds to the intracellular domain of the receptor and retains antigen binding upon expression as an intrabody in the reducing environment of the cytosol. Here, we used scFv(225) and scFv(30) domains to generate a novel type of bispecific transmembrane antibody termed 225.TM.30, that simultaneously targets intra- and extracellular EGFR epitopes. Bispecific 225.TM.30 and related membrane-anchored monospecific 225.TM and TM.30 proteins carrying extracellular scFv(225) or intracellular scFv(30) antibody fragments linked to a transmembrane domain were expressed in EGFR-overexpressing tumor cells using a doxycycline-inducible retroviral system. Induced expression of 225.TM.30 and 225.TM, but not TM.30 reduced EGFR surface levels and ligand-induced EGFR activation, while all three molecules markedly inhibited tumor cell growth. Co-localization of 225.TM with EGFR was predominantly found on the cell surface, while interaction with 225.TM.30 and TM.30 proteins resulted in the redistribution of EGFR to perinuclear compartments. Our data demonstrate functionality of this novel type of membrane-anchored intrabodies in tumor cells and suggest distinct modes of action of mono- and bispecific variants.

Expression of epidermal growth factor receptors and epidermal growth factor, amphiregulin and neuregulin in bovine uteroplacental tissues during gestation

INTRODUCTION

Growth factors are proteins that bind to specific cell surface receptors that initiate signalling pathways and result in proliferation or differentiation of the affected cells. During gestation, epidermal growth factor receptors (ErbB1-4) and its ligands (epidermal growth factor-EGF, amphiregulin-AREG, neuregulin1-NRG1) play a significant role in differentiation, function and growth of the uterus.

OBJECTIVES

To determine the role of ErbB receptors and EGF, AREG and NRG1 in bovine uteroplacental tissues during gestation.

METHODS

Placentomes and interplacentomal areas from 30 cows from early gestation until near term were analysed by immunohistochemistry.

RESULTS

ErbB receptors and its ligands were observed in uteroplacental tissues and its expression was maintained throughout pregnancy, but ErbB1 receptor did not exist in the caruncular and cotyledonary stromal cells. Besides, caruncular stromal cells did not present with any immune reaction for EGF, AREG and NRG1. Generally, it was observed that total scores for ErbB receptors and its ligands (EGF, AREG and NRG1) had decreased from early to late gestation (p < 0.05).

CONCLUSION

Our study shows the presence of ErbB receptors and its ligands participate in the mid- and late-phases of pregnancy. To our knowledge, this is the first study on the expression of NRG1 during bovine pregnancy. These results indicates that these factors may play a crucial role not only to enable cellular proliferation and differentiation in the uterus throughout gestation, but also to have a potential role in the cellular communication maintained between the embryo/fetus and uterus by the placenta.

Quantification of cell surface proteins with bispecific antibodies

Flow cytometry is an established method for fast and accurate quantitation of cellular protein levels and requires fluorescently labeled antibodies as well as calibration standards. A critical step for quantitation remains the production of suitable detection antibodies with a precisely defined ratio of antigen-binding sites to fluorophores. Problems often arise as a consequence of inefficient and unspecific labeling which can influence antibody properties. In addition, the number of incorporated fluorophores necessitates a special normalization step for quantitation. To address these problems, we constructed different mono- and bivalent bispecific antibodies with binding site(s) for the cell surface antigens, cMET, EGFR1/HER1, ErbB2/HER2 or ErbB3/HER3 and with an additional digoxigenin-binding single-chain Fv fusion. The fluorophore Cy5 was covalently coupled to digoxigenin and quantitatively bound by the bispecific antibody. A panel of tumor cell lines was assessed under different culture conditions for absolute receptor expression levels of the indicated antigens and the data were set in relation to mRNA, gene count and immunoblot data. We could reproducibly quantify these receptors, omit the otherwise required normalization step and demonstrate the superiority of a 1 + 1 bispecific antibody. The same antibodies were also used to quantify the number of proteins in intracellular vesicles in confocal microscopy. The antibodies can be stored like regular antibodies and can be coupled with different digoxigenin-labeled fluorophores which makes them excellent tools for FACS and imaging-based experiments.

Modulation of dorsal root ganglion development by ErbB signaling and the scaffold protein Sorbs3

The multipotent cells of the vertebrate neural crest (NC) arise at the dorsal aspect of the neural tube, then migrate throughout the developing embryo and differentiate into diverse cell types, including the sensory neurons and glia of the dorsal root ganglia (DRG). As multiple cell types are derived from this lineage, it is ideal for examining mechanisms of fate restriction during development. We have isolated a mutant, ouchless, that specifically fails to develop DRG neurons, although other NC derivatives develop normally. This mutation affects the expression of Sorbs3, a scaffold protein known to interact with proteins involved in focal adhesions and several signaling pathways. ouchless mutants share some phenotypic similarities with mutants in ErbB receptors, EGFR homologs that are implicated in diverse developmental processes and associated with several cancers; and ouchless interacts genetically with an allele of erbb3 in DRG neurogenesis. However, the defect in ouchless DRG neurogenesis is distinct from ErbB loss of function in that it is not associated with a loss of glia. Both ouchless and neurogenin1 heterozygous fish are sensitized to the effects of ErbB chemical inhibitors, which block the development of DRG in a dose-dependent manner. Inhibitors of MEK show similar effects on DRG neurogenesis. We propose a model in which Sorbs3 helps to integrate ErbB signals to promote DRG neurogenesis through the activation of MAPK and upregulation of neurogenin1.

Expression of epidermal growth factors and a tight junction protein in the nasal mucosa of patients with chronic hypertrophic rhinitis

BACKGROUND

ErbB family receptors and tight junction proteins participate in the pathologic process including tissue remodelling of inflammatory diseases in the upper and lower respiratory tracts. This study aimed at investigating the expressions of erbB1, 2, 3, 4, and a tight junction protein, claudin-1, in the nasal mucosa of patients with chronic hypertrophic rhinitis.

METHODS

Inferior turbinates were collected from 10 turbinectomised patients with allergic and non-allergic chronic hypertrophic rhinitis. The expressions of erbB1, 2, 3, 4, and claudin-1 were examined by fluorescence immunohistochemistry and by quantitative real-time transcription-polymerase chain reaction (qRT-PCR).

RESULTS

All erbB1-4 and claudin-1 were detected, and mainly localised in the epithelial cells and nasal gland cells. The immunoreactivity for claudin-1 was positively correlated with the expressions of erbB1, 2 and 4, but negatively correlated with that of erbB3. The mRNA expressions of erbB1, 2 and 4 were positively correlated with one another, whereas the expression of erbB3 showed negative correlation with the immunoreactivity for erbB2 and 4.

CONCLUSIONS

These results suggest a possible participation of erbBs and claudin-1 in tissue remodelling in chronic hypertrophic rhinitis.

Somatic mutations of the EGF receptor and their signal transducers affect the efficacy of EGF receptor-specific tyrosine kinase inhibitors

Non-small cell lung cancer (NSCLC) is a major subtype of lung cancer that has been the most common and most fatal cancer worldwide. Gefitinib (Iressa) and erlotinib (Tarceva) specific tyrosine kinase inhibitors (TKI) for the epidermal growth factor receptor (EGFR), have been demonstrated to be effective for some NSCLC patients and are pioneering molecular-targeted drugs used in the clinic for cancer. Because many studies indicate that only some patient populations benefit from these drugs, there has been an urgent need to develop diagnostic methods to select appropriate patients for whom treatment with these drugs will be beneficial. Moreover, problems of acquired resistance after long-term treatment with the drugs have emerged. In this review, I summarize the current understanding of the EGFR-activated signal transduction pathway, which plays important roles in tumorigenesis, and of the molecular mechanisms that determine the sensitivity toward EGFR-TKI.

Targeting HER2 in breast cancer: overview of long-term experience

The ability to probe diseases at the genomic level has improved our understanding and enhanced the treatment of breast cancer. One important finding relates to the HER2 oncogene which encodes a novel transmembrane receptor that, when overexpressed, appears to confer growth and survival advantages to breast tumor cells. This fortuitous discovery enabled researchers to develop agents which could inhibit receptor-mediated tumor cell signaling. Numerous clinical trials of such agents have demonstrated improved outcomes in patients with HER2-positive breast cancer. Nonetheless, not all tumors respond to therapy targeting the receptor, while relapses occur after an initial response to treatment. This paper provides a historical and current perspective of the treatment of patients with HER2-positive breast cancer.