A recombinant decoy comprising EGFR and ErbB-4 inhibits tumor growth and metastasis

Trapping all ERBB ligands decreases pancreatic lesions in a murine model of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is among the deadliest of cancers. Attempts to develop targeted therapies still need to be established. Some oncogenic mechanisms in PDAC carcinogenesis harness the EGFR/ERBB receptor family. To explore the effects on pancreatic lesions, we attempted simultaneous blockade of all ERBB ligands in a PDAC mouse model. To this end, we engineered a molecular decoy, TRAP-FC , comprising the ligand-binding domains of both EGFR and ERBB4 and able to trap all ERBB ligands. Next, we generated a transgenic mouse model (CBATRAP/0 ) expressing TRAP-FC ubiquitously under the control of the chicken-beta-actin promoter and crossed these mice with KRASG12D/+ mice (Kras) to generate Trap/Kras mice. The resulting mice displayed decreased emergence of spontaneous pancreatic lesion areas and exhibited reduced RAS activity and decreased activities of ERBBs, with the exception of ERBB4, which showed increased activity. To identify the involved receptor(s), we employed CRISPR/Cas9 DNA editing to singly delete each ERBB receptor in the human pancreatic carcinoma cell line Panc-1. Ablation of each ERBB family member, especially the loss of EGFR or ERBB2/HER2, altered signaling downstream of the other three ERBB receptors and decreased cell proliferation, migration, and tumor growth. We conclude that simultaneously blocking the entire ERBB receptor family is therapeutically more effective than individually inhibiting only one receptor or ligand in terms of reducing pancreatic tumor burden. In summary, trapping all ERBB ligands can reduce pancreatic lesion area and RAS activity in a murine model of pancreatic adenocarcinoma; hence, it might represent a promising approach to treat PDAC in patients.

Insulin‑like growth factor axis: A potential nanotherapy target for resistant cervical cancer tumors (Review)

Cervical cancer is among the most frequently occurring neoplasms worldwide, and it particularly affects individuals in developing countries. Factors such as the low quality of screening tests, the high incidence of locally advanced cancer stages and the intrinsic resistance of certain tumors are the main causes of failure in the treatment of this neoplasm. Due to advances in the understanding of carcinogenic mechanisms and bioengineering research, advanced biological nanomaterials have been manufactured. The insulin-like growth factor (IGF) system comprises multiple growth factor receptors, including IGF receptor 1. These receptors are activated by binding to their respective growth factor ligands, IGF-1 and IGF-2, and insulin, and play an important role in the development, maintenance, progression, survival and treatment resistance of cervical cancer. In the present review, the role of the IGF system in cervical cancer and three nanotechnological applications that use elements of this system are described, namely Trap decoys, magnetic iron oxide nanoparticles and protein nanotubes. Their use in the treatment of resistant cervical cancer tumors is also discussed.

Senescence-associated reprogramming induced by interleukin-1 impairs response to EGFR neutralization

Background

EGFR targeting is currently the main treatment strategy for metastatic colorectal cancer (mCRC). Results of different clinical trials show that patients with wild-type KRAS and BRAF benefit from anti-EGFR monoclonal antibodies (moAbs) cetuximab (CTX) or panitumumab. Unfortunately, despite initial response, patients soon became refractory. Tumor heterogeneity and multiple escaping routes have been addressed as the main culprit, and, behind genomic alterations already described, changes in signaling pathways induced by drug pressure are emerging as mechanisms of acquired resistance. We previously reported an association between reduced sensitivity to CTX and increased expression of IL-1. However, how IL-1 mediates CTX resistance in mCRC is still unclear.

Methods

Under CTX treatment, the upregulation of IL-1R1 expression and a senescence program in sensitive colorectal cancer (CRC) cell lines is examined over time using qPCR, immunoblotting, and immunofluorescence.

Results

In sensitive CRC cells, IL-1 appeared responsible for a CTX-mediated G0 phase arrest. On the contrary, CTX-resistant CRC cells (CXR) maintained high mRNA levels of IL-1R1 and a post-senescence reprogramming, as indicated by increased SNAIL expression. Interestingly, treatment of CXR cells with a recombinant decoy, able to sequester the soluble form of IL-1, pushed CTX-resistant CRC cells back into a stage of senescence, thus blocking their proliferation. Our model suggests a trans-regulatory mechanism mediated by IL-1 on EGFR signaling. By establishing senescence and regulating EGFR activity and expression, IL-1 exposure ultimately bestows resistance.

Conclusions

To sum up, our findings point to the combined blockage of IL-1R and EGFR as a promising therapeutical approach to restore sensitivity to EGFR-targeting monoclonal antibodies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s11658-022-00319-7.

Targeting autocrine amphiregulin robustly and reproducibly inhibits ovarian cancer in a syngeneic model: roles for wildtype p53

Ovarian cancer (OvCA) remains one of the most devastating malignancies, but treatment options are still limited. We report that amphiregulin (AREG) can serve as an effective and safe pharmacological target in a syngeneic murine model. AREG is highly abundant in abdominal fluids of patients with advanced OvCa. In immunocompetent animals, depletion or overexpression of AREG respectively prolonged or shortened animal survival. A new antibody we generated in AREG-knockout mice recognized murine AREG and reproducibly prolonged animal survival in the syngeneic model. The underlying mechanism likely involves binding of wildtype p53 to AREG's promoter and autocrine activation of the epidermal growth factor receptor (EGFR), a step blocked by the antibody. Accordingly, depletion of p53 downregulated AREG secretion and conferred tolerance, whereas blocking an adaptive process involving CXCL1, which transactivates EGFR, might increase therapeutic efficacy. Consistent with these observations, analysis of OvCa patients revealed that high AREG correlates with poor prognosis of patients expressing wildtype TP53. In conclusion, clinical tests of the novel antibody are warranted; high AREG, normal TP53, and reduced CXCL1 activity might identify patients with OvCa who may derive therapeutic benefit.

New insights into ErbB3 function and therapeutic targeting in cancer

INTRODUCTION

The importance of ErbB3 receptor tyrosine kinase in cancer progression, primary and acquired drug resistance, has become steadily evident since its discovery in 1989. ErbB3 overexpression in various solid organ malignancies is associated with shorter survival of patients. However, initial strategies to therapeutically target ErbB3 have not been rewarding.

AREAS COVERED

Here, we provide an overview of ErbB3 biology in carcinogenesis. We outline the role of ErbB3 as a critical pathway for resistance to other anti-cancer drugs. We focus on emerging clinical data, which will steer the potential future development of ErbB3 directed therapies.

EXPERT OPINION

Initial approaches to ErbB3 targeting have been challenging. However, the lack of success of anti-ErbB3 therapies in ongoing clinical trials may relate more to the complex biology of the receptor and challenges with the biomarkers used to date. Furthermore, it seems certain that the expression of the receptor per se is necessary but not sufficient for the response to ErbB3 therapies. Emerging data suggest that more sophisticated biomarkers are needed. Nonetheless, it is also likely that ErbB3 therapies may have the most efficacy in combination therapy, and their favorable toxicity profile makes this feasible.

Targeting the IGF-Axis for Cancer Therapy: Development and Validation of an IGF-Trap as a Potential Drug

The insulin-like growth factor (IGF)-axis was implicated in cancer progression and identified as a clinically important therapeutic target. Several IGF-I receptor (IGF-IR) targeting drugs including humanized monoclonal antibodies have advanced to phase II/III clinical trials, but to date, have not progressed to clinical use, due, at least in part, to interference with insulin receptor signaling and compensatory signaling by the insulin receptor (IR) isoform A that can bind IGF-II and initiate mitogenic signaling. Here we briefly review the current state of IGF-targeting biologicals, discuss some factors that may be responsible for their poor performance in the clinic and outline the stepwise bioengineering and validation of an IGF-Trap—a novel anti-cancer therapeutic that could bypass these limitations. The IGF-Trap is a heterotetramer, consisting of the entire extracellular domain of the IGF-IR fused to the Fc portion of human IgG₁. It binds human IGF-I and IGF-II with a three-log higher affinity than insulin and could inhibit IGF-IR driven cellular functions such as survival, proliferation and invasion in multiple carcinoma cell models in vitro. In vivo, the IGF-Trap has favorable pharmacokinetic properties and could markedly reduce metastatic outgrowth of colon and lung carcinoma cells in the liver, outperforming IGF-IR and ligand-binding monoclonal antibodies. Moreover, IGF-Trap dose-response profiles correlate with their bio-availability profiles, as measured by the IGF kinase receptor-activation (KIRA) assay, providing a novel, surrogate biomarker for drug efficacy. Our studies identify the IGF-Trap as a potent, safe, anti-cancer therapeutic that could overcome some of the obstacles encountered by IGF-targeting biologicals that have already been evaluated in clinical settings.

A Novel Role for the Interleukin-1 Receptor Axis in Resistance to Anti-EGFR Therapy

Cetuximab (CTX) is a monoclonal antibody targeting the epidermal growth factor receptor (EGFR), commonly used to treat patients with metastatic colorectal cancer (mCRC). Unfortunately, objective remissions occur only in a minority of patients and are of short duration, with a population of cells surviving the treatment and eventually enabling CTX resistance. Our previous study on CRC xenopatients associated poor response to CTX with increased abundance of a set of pro-inflammatory cytokines, including the interleukins IL-1A, IL-1B and IL-8. Stemming from these observations, our current work aimed to assess the role of IL-1 pathway activity in CTX resistance. We employed a recombinant decoy TRAP IL-1, a soluble protein combining the human immunoglobulin Fc portion linked to the extracellular region of the IL-1-receptor (IL-1R1), able to sequester IL-1 directly from the medium. We generated stable clones expressing and secreting a functional TRAP IL-1 into the culture medium. Our results show that IL-1R1 inhibition leads to a decreased cell proliferation and a dampened MAPK and AKT axes. Moreover, CRC patients not responding to CTX blockage displayed higher levels of IL-1R1 than responsive subjects, and abundant IL-1R1 is predictive of survival in patient datasets specifically for the consensus molecular subtype 1 (CMS1). We conclude that IL-1R1 abundance may represent a therapeutic marker for patients who become refractory to monoclonal antibody therapy, while inhibition of IL-1R1 by TRAP IL-1 may offer a novel therapeutic strategy.

Suppression of c-MET overcomes erlotinib resistance in tongue cancer cells

Background

Erlotinib is a commonly used molecular-targeted drug for the treatment of tongue cancer. However, the development of acquired resistance to erlotinib hampers its therapeutic use.

Materials and methods

To analyze the erlotinib resistance, long-term and short term survival assay were used to compare the resistance between parental and resistant tongue cancer cells. Flow cytometry, Hochest staining and western blot were used to analyze the apoptosis among the cells. Moreover, Transwell and wound healing assay were used to compare the invasion ability of the cells. To deeply explore the drug resistance in vivo, orthotopic tumor studies were applied. Finally, to explain the mechanism of c-met in erlotinib resistance, shRNA against c-met was used to down-regulate the expression of c-met. And SU11274 also used in orthotopic model.

Results

We established erlotinib-resistant human tongue cancer cell line by chronic exposure of TCA-8113 cells to increasing concentrations of erlotinib and determined the role of c-MET and EGFR in the development of acquired resistance. We found a significant increase in the phosphorylation of c-MET and an obvious decrease of the phosphorylation of EGFR in erlotinib-resistant cells. Our results also revealed that inhibition of c-MET alone with SU11274 exerted an inhibitory effect on the proliferation of erlotinib-resistant cells in the short term; however, it failed to sustain the inhibitory effect in the long term. Simultaneous inhibition of c-MET and EGFR significantly inhibited the proliferation of erlotinib-resistant cells in both a short and long period. Furthermore, we explored the underlying mechanism and found that treatment of erlotinib-resistant cells with SU11274 or shRNA against c-MET induced the phosphorylation of EGFR. Moreover, our results demonstrated that simultaneous inhibition of c-MET and EGFR significantly inhibited the migration and invasion of erlotinib-resistant cells.

Conclusion

Taken together, our results suggested that c-MET is involved in acquired drug resistance to erlotinib and that cotargeting of EGFR and c-MET could overcome acquired resistance to erlotinib and inhibit the invasion and metastasis of erlotinib-resistant cells.

Targeting the NRG1/HER3 pathway in tumor cells and cancer-associated fibroblasts with an anti-neuregulin 1 antibody inhibits tumor growth in pre-clinical models of pancreatic cancer

Neuregulin 1 (NRG1), a ligand for HER3 and HER4 receptors, is secreted by both pancreatic tumor cells (PC) and cancer-associated fibroblasts (CAFs), the latter representing the most abundant compound of pancreatic stroma. This desmoplastic stroma contributes to Pancreatic Ductal Adenocarcinoma (PDAC) aggressiveness and therapeutic failure by promoting tumor progression, invasion and resistance to chemotherapies. In the present work, we aimed at disrupting the complex crosstalk between PC and CAF in order to prevent tumor cell proliferation. To do so, we demonstrated the promising tumor growth inhibitory effect of the 7E3, an original antibody directed to NRG1. This antibody promotes antibody dependent cellular cytotoxicity in NRG1-positive PC and CAFs and inhibits NRG1-associated signaling pathway induction, by blocking NRG1-mediated HER3 activation. Moreover, 7E3 inhibits migration and growth of pancreatic cancer cells co-cultured with CAFs, both in vitro and in vivo using orthotopic pancreatic tumor xenografts. Our preclinical results demonstrate that the anti-NRG1 antibody 7E3 could represent a promising approach to target pancreatic stroma and cancer cells, thereby providing novel therapeutic options for PDAC.

PGE2/EP3/SRC signaling induces EGFR nuclear translocation and growth through EGFR ligands release in lung adenocarcinoma cells

Prostaglandin E₂ (PGE₂) interacts with tyrosine kinases receptor signaling in both tumor and stromal cells supporting tumor progression. Here we demonstrate that in non-small cell lung carcinoma (NSCLC) cells, A549 and GLC82, PGE₂ promotes nuclear translocation of epidermal growth factor receptor (nEGFR), affects gene expression and induces cell growth. Indeed, cyclin D1, COX-2, iNOS and c-Myc mRNA levels are upregulated following PGE₂ treatment. The nuclear localization sequence (NLS) of EGFR as well as its tyrosine kinase activity are required for the effect of PGE₂ on nEGFR and downstream signaling activities. PGE₂ binds its bona fide receptor EP3 which by activating SRC family kinases, induces ADAMs activation which, in turn, releases EGFR-ligands from the cell membrane and promotes nEGFR. Amphiregulin (AREG) and Epiregulin (EREG) appear to be involved in nEGFR promoted by the PGE₂/EP3-SRC axis. Pharmacological inhibition or silencing of the PGE₂/EP3/SRC-ADAMs signaling axis or EGFR ligands i.e. AREG and EREG expression abolishes nEGFR induced by PGE₂. In conclusion, PGE₂ induces NSCLC cell proliferation by EP3 receptor, SRC-ADAMs activation, EGFR ligands shedding and finally, phosphorylation and nEGFR. Since nuclear EGFR is a hallmark of cancer aggressiveness, our findings reveal a novel mechanism for the contribution of PGE₂ to tumor progression.

Database-independent Protein Sequencing (DiPS) Enables Full-length de Novo Protein and Antibody Sequence Determination

Traditional "bottom-up" proteomic approaches use proteolytic digestion, LC-MS/MS, and database searching to elucidate peptide identities and their parent proteins. Protein sequences absent from the database cannot be identified, and even if present in the database, complete sequence coverage is rarely achieved even for the most abundant proteins in the sample. Thus, sequencing of unknown proteins such as antibodies or constituents of metaproteomes remains a challenging problem. To date, there is no available method for full-length protein sequencing, independent of a reference database, in high throughput. Here, we present Database-independent Protein Sequencing, a method for unambiguous, rapid, database-independent, full-length protein sequencing. The method is a novel combination of non-enzymatic, semi-random cleavage of the protein, LC-MS/MS analysis, peptide de novo sequencing, extraction of peptide tags, and their assembly into a consensus sequence using an algorithm named "Peptide Tag Assembler." As proof-of-concept, the method was applied to samples of three known proteins representing three size classes and to a previously un-sequenced, clinically relevant monoclonal antibody. Excluding leucine/isoleucine and glutamic acid/deamidated glutamine ambiguities, end-to-end full-length de novo sequencing was achieved with 99-100% accuracy for all benchmarking proteins and the antibody light chain. Accuracy of the sequenced antibody heavy chain, including the entire variable region, was also 100%, but there was a 23-residue gap in the constant region sequence.

Molecular Pathways: Receptor Ectodomain Shedding in Treatment, Resistance, and Monitoring of Cancer

Proteases known as sheddases cleave the extracellular domains of their substrates from the cell surface. The A Disintegrin and Metalloproteinases ADAM10 and ADAM17 are among the most prominent sheddases, being widely expressed in many tissues, frequently overexpressed in cancer, and promiscuously cleaving diverse substrates. It is increasingly clear that the proteolytic shedding of transmembrane receptors impacts pathophysiology and drug response. Receptor substrates of sheddases include the cytokine receptors TNFR1 and IL6R; the Notch receptors; type-I and -III TGFβ receptors; receptor tyrosine kinases (RTK) such as HER2, HER4, and VEGFR2; and, in particular, MET and TAM-family RTKs AXL and Mer (MerTK). Activation of receptor shedding by mechanical cues, hypoxia, radiation, and phosphosignaling offers insight into mechanisms of drug resistance. This particularly holds for kinase inhibitors targeting BRAF (such as vemurafenib and dabrafenib) and MEK (such as trametinib and cobimetinib), along with direct sheddase inhibitors. Receptor proteolysis can be detected in patient fluids and is especially relevant in melanoma, glioblastoma, lung cancer, and triple-negative breast cancer where RTK substrates, MAPK signaling, and ADAMs are frequently dysregulated. Translatable strategies to exploit receptor shedding include combination kinase inhibitor regimens, recombinant decoy receptors based on endogenous counterparts, and, potentially, immunotherapy. Clin Cancer Res; 23(3); 623-9. ©2016 AACR.

Strategies of targeting the extracellular domain of RON tyrosine kinase receptor for cancer therapy and drug delivery

PURPOSE

Cancer is one of the most important life-threatening diseases in the world. The current efforts to combat cancer are being focused on molecular-targeted therapies. The main purpose of such approaches is based on targeting cancer cell-specific molecules to minimize toxicity for the normal cells. RON (Recepteur d'Origine Nantais) tyrosine kinase receptor is one of the promising targets in cancer-targeted therapy and drug delivery.

METHODS

In this review, we will summarize the available agents against extracellular domain of RON with potential antitumor activities.

RESULTS

The presented antibodies and antibody drug conjugates against RON in this review showed wide spectrum of in vitro and in vivo antitumor activities promising the hope for them entering the clinical trials.

CONCLUSION

Due to critical role of extracellular domain of RON in receptor activation, the development of therapeutic agents against this region could lead to fruitful outcome in cancer therapy.

Emerging anti-cancer antibodies and combination therapies targeting HER3/ERBB3

Cancer progression depends on stepwise accumulation of oncogenic mutations and a select group of growth factors essential for tumor growth, metastasis and angiogenesis. Agents blocking the epidermal growth factor receptor (EGFR, also called HER1 and ERBB1) and the co-receptor called HER2/ERBB2 have been approved over the last decade as anti-cancer drugs. Because the catalytically defective member of the family, HER3/ERBB3, plays critical roles in emergence of resistance of carcinomas to various drugs, current efforts focus on antibodies and other anti-HER3/ERBB3 agents, which we review herein with an emphasis on drug combinations and some unique biochemical features of HER3/ERBB3.

Targeting non-canonical autophagy overcomes erlotinib resistance in tongue cancer

Acquired resistance to epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) frequently occurs in many human cancers and hampers their therapeutic use. A large body of evidence has demonstrated the pro-survival role of autophagy in many human cancers. However, whether autophagy is involved in the induction of erlotinib resistance in tongue squamous cell carcinoma (TSCC) remains unknown. In this report, we found that autophagy prior to or induced by erlotinib treatment plays an important role in erlotinib resistance in tongue cancer cells. Using LC3 transfection, we observed that autophagy is upregulated and further induced when treated with erlotinib. Moreover, we found that autophagy plays a cytoprotective role by MTT analysis of the cell viability in TSCCs when treated with rapamycin or hydroxychloroquine (HCQ) in combination with erlotinib. However, 3-methyladenine (3-MA) did not influence the autophagy. Then, through siRNA technology and WB, we found that erlotinib-induced autophagy is mediated by ATG5 but not Beclin1. Also, knockdown of ATG5 significantly decreased the erlotinib resistance and knockdown of Beclin1 did not affect the sensitivity to erlotinib in TSCCs. Taken together, this indicates the critical role of non-canonical autophagy in erlotinib resistance in TSCCs.

Targeting autocrine HB-EGF signaling with specific ADAM12 inhibition using recombinant ADAM12 prodomain

Dysregulation of ErbB-family signaling underlies numerous pathologies and has been therapeutically targeted through inhibiting ErbB-receptors themselves or their cognate ligands. For the latter, “decoy” antibodies have been developed to sequester ligands including heparin-binding epidermal growth factor (HB-EGF); however, demonstrating sufficient efficacy has been difficult. Here, we hypothesized that this strategy depends on properties such as ligand-receptor binding affinity, which varies widely across the known ErbB-family ligands. Guided by computational modeling, we found that high-affinity ligands such as HB-EGF are more difficult to target with decoy antibodies compared to low-affinity ligands such as amphiregulin (AREG). To address this issue, we developed an alternative method for inhibiting HB-EGF activity by targeting its cleavage from the cell surface. In a model of the invasive disease endometriosis, we identified A Disintegrin and Metalloproteinase 12 (ADAM12) as a protease implicated in HB-EGF shedding. We designed a specific inhibitor of ADAM12 based on its recombinant prodomain (PA12), which selectively inhibits ADAM12 but not ADAM10 or ADAM17. In endometriotic cells, PA12 significantly reduced HB-EGF shedding and resultant cellular migration. Overall, specific inhibition of ligand shedding represents a possible alternative to decoy antibodies, especially for ligands such as HB-EGF that exhibit high binding affinity and localized signaling.

Pharmacokinetic and pharmacodynamic considerations for the next generation protein therapeutics

Increasingly sophisticated protein engineering efforts have been undertaken lately to generate protein therapeutics with desired properties. This has resulted in the discovery of the next generation of protein therapeutics, which include: engineered antibodies, immunoconjugates, bi/multi-specific proteins, antibody mimetic novel scaffolds, and engineered ligands/receptors. These novel protein therapeutics possess unique physicochemical properties and act via a unique mechanism-of-action, which collectively makes their pharmacokinetics (PK) and pharmacodynamics (PD) different than other established biological molecules. Consequently, in order to support the discovery and development of these next generation molecules, it becomes important to understand the determinants controlling their PK/PD. This review discusses the determinants that a PK/PD scientist should consider during the design and development of next generation protein therapeutics. In addition, the role of systems PK/PD models in enabling rational development of the next generation protein therapeutics is emphasized.

Fibroblast-derived neuregulin 1 promotes compensatory ErbB3 receptor signaling in mutant BRAF melanoma

Rapidly accelerated fibrosarcoma (RAF) inhibitors are first-line treatments for patients harboring V600E/K mutant BRAF melanoma. Although RAF inhibitors produce high response rates, the degree of tumor regression is heterogeneous. Compensatory/adaptive responses to targeted inhibitors are frequently initiated by the activation of growth factor receptor tyrosine kinases, including ErbB3, and factors from the tumor microenvironment may play an important role. We have shown previously that mutant v-raf murine sarcoma viral oncogene homolog B1 (BRAF) melanoma cells have enhanced activation of ErbB3 following RAF inhibition. However, the source of neuregulin 1 (NRG1), the ligand for ErbB3, is unknown. In this study, we demonstrate that NRG1 is highly expressed by dermal fibroblasts and cancer-associated fibroblasts (CAFs) isolated from mutant BRAF melanomas. Conditioned medium from fibroblasts and CAFs enhanced ErbB3 pathway activation and limited RAF inhibitor cytotoxicity in V600 mutant BRAF-harboring melanomas. Targeting the ErbB3/ErbB2 pathway partially reversed the protective effects of fibroblast/CAF-derived NRG1 on cell growth properties of RAF inhibitor-treated melanoma cells. These findings support the idea that NRG1, acting in a paracrine manner, promotes resistance to RAF inhibitors and emphasize that targeting the ErbB3/ErbB2 pathway will likely improve the efficacy of RAF inhibitors for mutant BRAF melanoma patients.

egr-4, a target of EGFR signaling, is required for the formation of the brain primordia and head regeneration in planarians

During the regeneration of freshwater planarians, polarity and patterning programs play essential roles in determining whether a head or a tail regenerates at anterior or posterior-facing wounds. This decision is made very soon after amputation. The pivotal role of the Wnt/β-catenin and Hh signaling pathways in re-establishing anterior-posterior (AP) polarity has been well documented. However, the mechanisms that control the growth and differentiation of the blastema in accordance with its AP identity are less well understood. Previous studies have described a role of Smed-egfr-3, a planarian epidermal growth factor receptor, in blastema growth and differentiation. Here, we identify Smed-egr-4, a zinc-finger transcription factor belonging to the early growth response gene family, as a putative downstream target of Smed-egfr-3. Smed-egr-4 is mainly expressed in the central nervous system and its silencing inhibits anterior regeneration without affecting the regeneration of posterior regions. Single and combinatorial RNA interference to target different elements of the Wnt/β-catenin pathway, together with expression analysis of brain- and anterior-specific markers, revealed that Smed-egr-4: (1) is expressed in two phases - an early Smed-egfr-3-independent phase and a late Smed-egfr-3-dependent phase; (2) is necessary for the differentiation of the brain primordia in the early stages of regeneration; and (3) that it appears to antagonize the activity of the Wnt/β-catenin pathway to allow head regeneration. These results suggest that a conserved EGFR/egr pathway plays an important role in cell differentiation during planarian regeneration and indicate an association between early brain differentiation and the proper progression of head regeneration.

Suppression of heregulin β signaling by the single N-glycan deletion mutant of soluble ErbB3 protein

Heregulin signaling is involved in various tumor proliferations and invasions; thus, receptors of heregulin are targets for the cancer therapy. In this study we examined the suppressing effects of extracellular domains of ErbB2, ErbB3, and ErbB4 (soluble ErbB (sErbB)) on heregulin β signaling in human breast cancer cell line MCF7. It was found that sErbB3 suppresses ligand-induced activation of ErbB receptors, PI3K/Akt and Ras/Erk pathways most effectively; sErbB2 scarcely suppresses ligand-induced signaling, and sErbB4 suppresses receptor activation at ∼10% efficiency of sErbB3. It was revealed that sErbB3 does not decrease the effective ligands but decreases the effective receptors. By using small interfering RNA (siRNA) for ErbB receptors, we determined that sErbB3 suppresses the heregulin β signaling by interfering ErbB3-containing heterodimers including ErbB2/ErbB3. By introducing the mutation of N418Q to sErbB3, the signaling-inhibitory effects were increased by 2-3-fold. Moreover, the sErbB3 N418Q mutant enhanced anticancer effects of lapatinib more effectively than the wild type. We also determined the structures of N-glycan on Asn-418. Results suggested that the N-glycan-deleted mutant of sErbB3 suppresses heregulin signaling via ErbB3-containing heterodimers more effectively than the wild type. Thus, we demonstrated that the sErbB3 N418Q mutant is a potent inhibitor for heregulin β signaling.

Beyond antibodies: using biological principles to guide the development of next-generation protein therapeutics

Protein-based biologics, which leverage the inherent affinity and specificity of protein-protein interactions, offer an effective strategy for targeting and modulating disease pathways. Despite the broad diversity of the proteome, monoclonal antibodies have been the major focus of such drug discovery efforts. While antibodies have shown great clinical value, the breadth and complexity of human disease highlight the need for alternatives that expand the therapeutic repertoire beyond this single class of proteins. The elucidation of molecular mechanisms underlying human disease has provided new opportunities for protein-based drugs to address challenging clinical problems. Natural ligands and receptors, which inherently modulate complex biological processes, have emerged as promising candidates for protein-based drug discovery efforts. Protein engineering strategies, guided by biological principles, are allowing ligands and receptors to be developed as next-generation therapeutics with improved safety and efficacy.

The ERBB network: at last, cancer therapy meets systems biology

Although it is broadly agreed that the improved treatment of patients with cancer will depend on a deeper molecular understanding of the underlying pathogenesis, only a few examples are already available. This Timeline article focuses on the ERBB (also known as HER) network of receptor tyrosine kinases (RTKs), which exemplifies how a constant dialogue between basic research and medical oncology can translate into both a sustained pipeline of novel drugs and ways to overcome acquired treatment resistance in patients. We track the key early discoveries that linked this RTK family to oncogenesis, the course of pioneering clinical research and their merger into a systems-biology framework that is likely to inspire further generations of effective therapeutic strategies.