ErbB receptors and cell polarity: new pathways and paradigms for understanding cell migration and invasion

HER2 Alterations in Non-Small Cell Lung Cancer: Biologico-Clinical Consequences and Interest in Therapeutic Strategies

Lung cancer stands as the first cause of death by cancer in the world. Despite the improvement in patients' outcomes in the past decades through the development of personalized medicine approaches, a substantial portion of patients remains ineligible for targeted therapies due to the lack of a "druggable" molecular target. HER2, a receptor tyrosine kinase member of the EGFR/ErbB family, is known to show oncogenic properties. In this review, we focus on the different HER2 dysregulation mechanisms that have been observed in non-small cell lung cancer (NSCLC): gene mutation, gene amplification, protein overexpression and protein hyper-phosphorylation, the latter suggesting that HER2 dysregulation can occur independently of any molecular aberration. These HER2 alterations inevitably have consequences on tumor biology. Here, we discuss how they are not only involved in abnormal proliferation and survival of cancer cells but also potentially in increased angiogenic properties, mesenchymal features and tumor immune escape. Finally, we review the impact of these HER2 alterations in various therapeutic approaches. While standard chemotherapy and groundbreaking immunotherapy seem rather ineffective for HER2-altered NSCLCs, the development of HER2-targeted therapies such as tyrosine kinase inhibitors, anti-HER2 antibodies and especially antibody-drug conjugates could provide new hopes for patients.

Circular RNA circEMB promotes osteosarcoma progression and metastasis by sponging miR-3184-5p and regulating EGFR expression

BACKGROUND

Osteosarcoma (OSA) is the most prevalent type of bone cancer with a high rate of metastasis. Circular RNAs (CircRNAs) play an essential role in multiple aspects of tumour biology. This study aimed to elucidate the role of circEMB in OSA.

METHODS

circRNAs related to OSA invasion were identified via RNA sequencing and qRT-PCR. The relationship between circEMB levels and clinicopathological features of OSA was examined using the clinical specimens and data of 53 patients with OSA. Several in vivo and in vitro experiments, including intravital imaging, whole-transcriptome sequencing, transwell assay, flow cytometry, dual-luciferase reporter assay, RIP assay, RNA pull-down assay and RNA-FISH, were performed to examine the effects of circEMB on the malignant behaviour of OSA.

RESULTS

A novel circRNA, named circEMB (hsa_circ_001310), was identified in this study. circEMB can promote the malignant behaviour of OSA. In vitro experiments revealed that circEMB knockdown decreased cell proliferation, inhibited tumour invasion and metastasis; increased apoptosis and resulted in G1/S phase arrest. In vivo experiments revealed that circEMB knockdown inhibited tumour growth and metastasis in xenograft-bearing mice. Mechanistically, circEMB affects the malignant behaviour of OSA by mediating EGFR as an miR-3184-5p sponge. In addition, the circEMB/miR-3184-5p/EGFR axis modulates methotrexate (MTX) resistance in OSA.

CONCLUSIONS

CircEMB plays a critical role in promoting cancer via the miR-3184-5p/EGFR pathway, indicating that circEMB may serve as a therapeutic target for OSA.

Prognostic Significance of Epidermal Growth Factor Receptor Expression in Distant Metastatic Melanoma from Primary Cutaneous Melanoma

Background

Epidermal growth factor receptor (EGFR) is overexpressed in many cancers. However, EGFR expression in melanoma and its role are conflicting.

Objective

This study aimed to evaluate EGFR expression in distant metastatic melanoma and analyze its relationship with histologic and clinical characteristics and survival.

Methods

Diagnostic tissues from 55 cases of distant metastatic melanoma was evaluated by immunohistochemistry for EGFR expression. Clinicopathologic features and survival outcomes were analyzed according to EGFR expression.

Results

The positive EGFR expression in distant metastatic melanoma was significantly correlated with the absence of ulceration. The EGFR expression in distant metastatic melanoma was significantly associated with poor survival, under the conditions of male sex and primary cutaneous melanoma without ulceration or Breslow thickness ≤4.0 mm. This study bears limitations of a retrospective study in a single institution.

Conclusion

EGFR immunostaining had predictive values for survival outcome. The EGFR expression in distant metastatic melanoma in male, no ulcer, or Breslow thickness ≤4.0 mm appeared to be involved in disease progression.

Blue-conversion of organic dyes produces artifacts in multicolor fluorescence imaging

Multicolor fluorescence imaging is a powerful tool visualizing the spatiotemporal relationship among biomolecules. Here, we report that commonly employed organic dyes exhibit a blue-conversion phenomenon, which can produce severe multicolor image artifacts leading to false-positive colocalization by invading predefined spectral windows, as demonstrated in the case study using EGFR and Tensin2. These multicolor image artifacts become much critical in localization-based superresolution microscopy as the blue-converted dyes are photoactivatable. We provide a practical guideline for the use of organic dyes for multicolor imaging to prevent artifacts derived by blue-conversion.

Blue-conversion, a photooxidative conversion leading to the hypsochromic shift of absorption and emission spectra, occurs in popular organic dyes under conventional laser illumination and produces severe artifacts in multicolor fluorescence imaging.

MYLK4 promotes tumor progression through the activation of epidermal growth factor receptor signaling in osteosarcoma

BACKGROUND

Osteosarcoma (OS) is the most common primary bone cancer in adolescents and lung metastasis is the leading cause of death in patients with OS. However, the molecular mechanisms that promote OS growth and metastasis remain unknown.

METHODS

We investigated the expression of myosin light chain kinase family members between metastasis and non-metastasis patients in the TARGET database and ensured that only myosin light chain kinase family member 4 (MYLK4) had higher expression in metastatic osteosarcoma patients. Then we confirmed the results by immunohistochemistry (IHC) and Western blotting (WB) of OS tissues. The effect of MYLK4 on the metastasis and proliferation of OS cells was investigated by wound healing, Transwell and colony-formation assays. Mass spectrum analysis was used to ensure the new binding protein of MYLK4. Tissue microarrays analysis was used to show the correlation between MYLK4 and pEGFR (Y1068). A series of in vivo experiments were conducted to reveal the mechanisms by which MYLK4 modulated the metastasis and proliferation of OS.

RESULTS

Myosin Light Chain Kinase Family Member 4 (MYLK4) was significantly upregulated in metastatic human OS tissues. Growth and metastasis of OS could be accelerated by MYLK4 overexpression, whereas silencing MYLK4 expression resulted in decreased cell growth and metastasis. Mechanistically, mass spectrum analysis showed that MYLK4 interacted with the epidermal growth factor receptor (EGFR) in osteosarcoma cells and promoted growth and metastasis via the EGFR signaling pathway. Tissue microarrays analysis also showed that MYLK4 expression had a positive correlation with the expression of pEGFR (Y1068). Moreover, the EGFR inhibitor gefitinib could partially reverse the effect of cell proliferation and metastasis caused by MYLK4 overexpression. Importantly, the combination of MYLK4 and EGFR inhibitors had synergistic effects on growth and metastasis of OS in vitro and in vivo.

CONCLUSION

Our results indicate that MYLK4 promotes OS growth and metastasis by activating the EGFR signaling pathway and can be a novel therapeutic target for the treatment of OS patients.

Expression level of EGFR and MET receptors regulates invasiveness of melanoma cells

Epidermal and hepatocyte growth factors can stimulate invasive abilities of melanoma cells, while treatment with combination of their receptors' (EGFR and MET, respectively) inhibitors reduces viability of these cells, as we have previously shown. Proposed therapy has potential; however, used drugs block more than one goal effectively, what raises the question about the real target of analysed inhibitors. For this reason, we analysed direct involvement of these receptors in the invasion of melanoma cells inducing EGFR and MET up‐ and down‐regulations in examined cells. Results were acquired with assays evaluating cell migration and invasion (scratch wound assay, Transwell filter‐based method and single‐cell tracking). We revealed that cells' motile abilities are increased after EGFR overexpression and decreased following EGFR and MET silencing. This outcome correlates with elevated (EGFR up‐regulation) or reduced (EGFR/MET down‐regulation) number of formed invadopodia, visualized with immunofluorescence, and their rate of proteolytic abilities, evaluated by fluorescent gelatin degradation assay, and gelatin zymography, compared to control cells. Above‐mentioned data indicate that both—EGFR and MET signalling is directly connected with melanoma cells invasion, what establishes these receptors as promising targets for anti‐cancer treatment.

HUNK phosphorylates EGFR to regulate breast cancer metastasis

Epidermal growth factor receptor (EGFR) is commonly over-expressed in metastatic breast cancer yet metastatic breast cancer is generally resistant to anti-EGFR therapies, and the mechanism for resistance to EGFR inhibitors in this setting is not fully understood. Hormonally up-regulated neu-associated kinase (HUNK) kinase is up-regulated in aggressive breast cancers and is thought to play a role in breast cancer metastasis. However, no studies have been conducted to examine a relationship between EGFR and HUNK in breast cancer metastasis. We performed a kinase substrate screen and identified that EGFR is phosphorylated by HUNK. Our studies show that HUNK phosphorylates EGFR at T654, enhancing receptor stability and downstream signaling. We found that increased phosphorylation of T654 EGFR correlates with increased epithelial to mesenchymal, migration and invasion, and metastasis. In addition, we found that HUNK expression correlates with overall survival and distant metastasis free survival. This study shows that HUNK directly phosphorylates EGFR at T654 to promote metastasis and is the first study to show that the phosphorylation of this site in EGFR regulates metastasis.

Combination of Selected MET and EGFR Inhibitors Decreases Melanoma Cells' Invasive Abilities

We have previously shown that combination of foretinib, an inhibitor of MET (hepatocyte growth factor receptor), with gefitinib or lapatinib, inhibitors of EGFR (epidermal growth factor receptor), has a synergistic cytotoxic effect on melanoma cells. However, there are cancer cells resistant to drugs’ treatment which are still able to invade. Thus, in this study, we examined the influence of these drugs on invasive abilities of melanoma cells. To investigate cell migration and invasion, Transwell inserts and wound healing assay were used. Cell viability was evaluated by XTT method, while invadopodia formation by immunocytochemistry. Level of phosphorylated Src kinase (pSrc) was verified by Western blot. Proteolytic activity of cells was analyzed using gelatin conjugated with fluorescein degradation assay and gelatin zymography. Combination of used inhibitors diminished cell movement, resulting in smaller distances covered by cells, and decreased the ratio of cells with ability to cross the Transwell inserts. These inhibitors induced changes in formation of invadopodia and actin cytoskeleton organization. Their application also decreased the level of pSrc kinase. Furthermore, used drugs led to reduction of proteolytic activity of examined cells. Our data support the idea that simultaneous targeting of EGFR and MET could be a promising therapeutic strategy inhibiting not only tumor cell growth but also its metastasis.

The ERBB receptor inhibitor dacomitinib suppresses proliferation and invasion of pancreatic ductal adenocarcinoma cells

PURPOSE

Pancreatic ductal adenocarcinoma (PDAC), the most common malignancy of the pancreas, is the fourth most common cause of cancer-related death in the USA. Local progression, early tumor dissemination and low efficacy of current treatments are the major reasons for its high mortality rate. The ERBB family is over-expressed in PDAC and plays essential roles in its tumorigenesis; however, single-targeted ERBB inhibitors have shown limited activity in this disease. Here, we examined the anti-tumor activity of dacomitinib, a pan-ERBB receptor inhibitor, on PDAC cells.

METHODS

Anti-proliferative effects of dacomitinib were determined using a cell proliferation assay and crystal violet staining. Annexin V/PI staining, radiation therapy and cell migration and invasion assays were carried out to examine the effects of dacomitinib on apoptosis, radio-sensitivity and cell motility, respectively. Quantitative reverse transcription-PCR (qRT-PCR) and Western blot analyses were applied to elucidate the molecular mechanisms underlying the anti-tumor activity of dacomitinib.

RESULTS

We found that dacomitinib diminished PDAC cell proliferation via inhibition of FOXM1 and its targets Aurora kinase B and cyclin B1. Moreover, we found that dacomitinib induced apoptosis and potentiated radio-sensitivity via inhibition of the anti-apoptotic proteins survivin and MCL1. Treatment with dacomitinib attenuated cell migration and invasion through inhibition of the epithelial-to-mesenchymal transition (EMT) markers ZEB1, Snail and N-cadherin. In contrast, we found that the anti-tumor activity of single-targeted ERBB agents including cetuximab (anti-EGFR mAb), trastuzumab (anti-HER2 mAb), H3.105.5 (anti-HER3 mAb) and erlotinib (EGFR small molecule inhibitor) were marginal.

CONCLUSIONS

Our findings indicate that dacomitinib-mediated blockade of the ERBB receptors yields advantages over single-targeted ERBB inhibition and provide a rationale for further investigation of the therapeutic potential of dacomitinib in the treatment of ERBB-driven PDAC.

Comparative efficacy of adjuvant trastuzumab-containing chemotherapies for patients with early HER2-positive primary breast cancer: a network meta-analysis

BACKGROUND

Trastuzumab (H) with chemotherapy benefits patients with HER2+ breast cancer (BC); however, we lack head-to-head pairwise assessment of survival or cardiotoxicity for specific combinations. We sought to identify optimal combinations.

METHODS

We searched PubMed, updated October 2017, using keywords "Breast Neoplasms/drug therapy," "Trastuzumab," and "Clinical Trial" and searched Cochrane Library. Our search included randomized trials of adjuvant H plus chemotherapy for early-stage HER2+ BC, and excluding trials of neoadjuvant therapy or without data to obtain hazard ratios (HRs) for outcomes. Following PRISMA guidelines, one investigator did initial search; two others independently confirmed and extracted information; and consensus with another investigator resolved disagreements. Before gathering data, we set outcomes of overall survival (OS), event-free survival (EFS), and severe cardiac adverse events (SCAEs). Analyzing 6 trials and 13,621 patients, we made direct and indirect comparisons using network meta-analysis on HR for OS or EFS and on odds ratio (OR) for SCAE; ranked therapy was done based on outcomes using p scores.

RESULTS

Compared with anthracycline-cyclophosphamide with taxane (ACT), ACT with concurrent H (ACT+H) showed best OS (HR 0.63, 95% confidence interval [CI] 0.55, 0.72), followed by taxane and carboplatin (TC) with concurrent H (TC+H) (HR 0.77, 95% CI 0.59, 1) and ACT with sequential H (ACT-H) (HR 0.85, 95% CI 0.68, 1.05). Pairwise comparisons showed statistically significant OS benefit for ACT+H over others; similar results for EFS. TC+H showed statistically significant lower SCAE risk compared to ACT+H (OR 0.13, 95% CI 0.03, 0.61).

CONCLUSIONS

Concurrent H with ACT or TC showed most clinical benefit for early-stage HER2+ BC; TC+H had lowest cardiotoxicity.

Signal transduction growth factors: the effective governance of transcription and cellular adhesion in cancer invasion

Giulio Bizzozero classified the tissues concerning their capacity to self-renew during the adult life in labile, stable and permanent tissues. In 1940 Viktor Hamburger and Rita Levi Montalcini exposed the possibility to induce the growth of permanent cells thanks to a specific ligand Nerve Growth Factor (NGF). Stanley Cohen purified a protein the Epidermal Growth Factor (EGF), able to induce epidermis proliferation and to elicit precocious eye disclosure and teeth eruption, establishing the “inverse” relationships between the proliferation and differentiation. These two biological effects induced by EGF were according to EGFR signaling is involved in a large array of cellular functions such as proliferation, survival, adhesion, migration and differentiation. This review is focused on the key role of growth factors signaling and their downstream effectors in physiological and in pathological phenomena, the authors highlight the governance of Growth factors during the EMT in cancer invasion.

4-Phenybutyric acid promotes gastric cancer cell migration via histone deacetylase inhibition-mediated HER3/HER4 up-regulation

Dysregulation of histone acetylation plays an important role in tumor development. Histone acetylation regulates gene transcription and expression, which is reversibly regulated by histone acetyltransferase (HAT) and histone deacetylase (HDAC). As an HDAC inhibitor, 4-phenylbutyric acid (4-PBA) can increase histone acetylation levels by inhibiting HDAC activity. While 4-PBA inhibits proliferation of tumor cells in vitro, clinical trials have failed to show benefits of 4-PBA for refractory solid tumors. Here, we found that 4-PBA could enhance the migration capacity of gastric cancer cells. Upregulation of HER3/HER4 and activation of HER3/HER4-ERK pathway was shown to be involved in 4-PBA-induced gastric cancer cell migration. Knockdown of HER3/HER4 blocked HER3/HER4-ERK activation and partially prevented 4-PBA-induced cell migration. Consistently, the ERK inhibitor PD98059 also partially prevented 4-PBA-induced cell migration. Moreover, enhanced levels of acetyl-histones were detected following 4-PBA-treatment, and histone3 acetylation in promoter regions of HER3 and HER4 were confirmed by ChIP. These results demonstrate that 4-PBA promotes gastric cancer cells migration through upregulation of HER3/HER4 subsequent to increased levels of acetyl-histone and activation of ERK signaling. These novel findings provide important considerations for the use of 4-PBA in cancer therapeutics.

Amorphous Silica Particles Relevant in Food Industry Influence Cellular Growth and Associated Signaling Pathways in Human Gastric Carcinoma Cells

Nanostructured silica particles are commonly used in biomedical and biotechnical fields, as well as, in cosmetics and food industry. Thus, their environmental and health impacts are of great interest and effects after oral uptake are only rarely investigated. In the present study, the toxicological effects of commercially available nano-scaled silica with a nominal primary diameter of 12 nm were investigated on the human gastric carcinoma cell line GXF251L. Besides the analysis of cytotoxic and proliferative effects and the comparison with effects of particles with a nominal primary diameter of 200 nm, emphasis was also given to their influence on the cellular epidermal growth factor receptor (EGFR) and mitogen-activated protein kinases (MAPK) signaling pathways—both of them deeply involved in the regulation of cellular processes like cell cycle progression, differentiation or proliferation. The investigated silica nanoparticles (NPs) were found to stimulate cell proliferation as measured by microscopy and the sulforhodamine B assay. In accordance, the nuclear level of the proliferation marker Ki-67 was enhanced in a concentration-dependent manner. At high particle concentrations also necrosis was induced. Finally, silica NPs affected the EGFR and MAPK pathways at various levels dependent on concentration and time. However, classical activation of the EGFR, to be reflected by enhanced levels of phosphorylation, could be excluded as major trigger of the proliferative stimulus. After 45 min of incubation the level of phosphorylated EGFR did not increase, whereas enhanced levels of total EGFR protein were observed. These results indicate interference with the complex homeostasis of the EGFR protein, whereby up to 24 h no impact on the transcription level was detected. In addition, downstream on the level of the MAP kinases ERK1/2 short term incubation appeared to affect total protein levels without clear increase in phosphorylation. Depending on the concentration range, enhanced levels of ERK1/2 phosphorylation were only observed after 24 h of incubation. Taken together, the present study demonstrates the potential of the tested silica particles to enhance the growth of gastric carcinoma cells. Although interference with the EGFR/MAPK cascade is observed, additional mechanisms are likely to be involved in the onset of the proliferative stimulus.

EGFR transactivation contributes to neuroinflammation in Streptococcus suis meningitis

BACKGROUND

Streptococcus suis serotype 2 (SS2) is an important zoonotic bacterial pathogen in both humans and animals, which can cause high morbidity and mortality. Meningitis is one of the major clinical manifestations of SS2 infection. However, the specific process of SS2 meningitis and its molecular mechanisms remain unclear. Epidermal growth factor receptor (EGFR) has been reported to initiate transduction of intracellular signals and regulate host inflammatory responses. Whether and how EGFR contributes to the development of S. suis meningitis are currently unknown.

METHODS

The tyrosine phosphorylation of cellular proteins, the transactivation of EGFR, as well as its dimerization, and the associated signal transduction pathways were investigated by immunoprecipitation and western blotting. Real-time quantitative PCR was used to investigate the transcriptional level of the ErbB family members, EGFR-related ligands, cytokines, and chemokines. The secretion of cytokines and chemokines in the serum and brain were detected by Q-Plex™ Chemiluminescent ELISA.

RESULTS

We found an important role of EGFR in SS2 strain SC19-induced meningitis. SC19 increasingly adhered to human brain microvascular endothelial cells (hBMEC) and caused inflammatory lesions in the brain tissues, with significant induction and secretion of proinflammatory cytokines and chemokines in the serum and brains. SC19 infection of hBMEC induced tyrosine phosphorylation of cellular EGFR in a ligand-dependent manner involving the EGF-like ligand HB-EGF, amphiregulin (AREG), and epiregulin (EREG) and led to heterodimerization of EGFR/ErbB3. The EGFR transactivation did not participate in SS2 strain SC19 adhesion of hBMEC, as well as in bacterial colonization in vivo. However, its transactivation contributed to the bacterial-induced neuroinflammation, via triggering the MAPK-ERK1/2 and NF-κB signaling pathways in hBMEC that promote the production of proinflammatory cytokines and chemokines.

CONCLUSIONS

We investigated for the first time the tyrosine phosphorylation of cellular proteins in response to SS2 strain SC19 infection of hBMEC and demonstrated the contribution of EGFR to SS2-induced neuroinflammation. These observations propose a novel mechanism involving EGFR in SS2-mediated inflammatory responses in the brain, and therefore, EGFR might be an important host target for further investigation and prevention of neuroinflammation caused by SS2 strains.

Role of ErbB Receptors in Cancer Cell Migration and Invasion

Growth factors mediate their diverse biologic responses (regulation of cellular proliferation, differentiation, migration and survival) by binding to and activating cell-surface receptors with intrinsic protein kinase activity named receptor tyrosine kinases (RTKs). About 60 RTKs have been identified and can be classified into more than 16 different receptor families. Their activity is normally tightly controlled and regulated. Overexpression of RTK proteins or functional alterations caused by mutations in the corresponding genes or abnormal stimulation by autocrine growth factor loops contribute to constitutive RTK signaling, resulting in alterations in the physiological activities of cells. The ErbB receptor family of RTKs comprises four distinct receptors: the EGFR (also known as ErbB1/HER1), ErbB2 (neu, HER2), ErbB3 (HER3) and ErbB4 (HER4). ErbB family members are often overexpressed, amplified, or mutated in many forms of cancer, making them important therapeutic targets. EGFR has been found to be amplified in gliomas and non-small-cell lung carcinoma while ErbB2 amplifications are seen in breast, ovarian, bladder, non-small-cell lung carcinoma, as well as several other tumor types. Several data have shown that ErbB receptor family and its downstream pathway regulate epithelial-mesenchymal transition, migration, and tumor invasion by modulating extracellular matrix (ECM) components. Recent findings indicate that ECM components such as matrikines bind specifically to EGF receptor and promote cell invasion. In this review, we will present an in-depth overview of the structure, mechanisms, cell signaling, and functions of ErbB family receptors in cell adhesion and migration. Furthermore, we will describe in a last part the new strategies developed in anti-cancer therapy to inhibit ErbB family receptor activation.

Computational Inferences of the Functions of Alternative/Noncanonical Splice Isoforms Specific to HER2+/ER-/PR- Breast Cancers, a Chromosome 17 C-HPP Study

This study was conducted as a part of the Chromosome-Centric Human Proteome Project (C-HPP) of the Human Proteome Organization. The main objective is to identify and evaluate functionality of a set of specific noncanonical isoforms expressed in HER2-neu positive, estrogen receptor negative (ER-), and progesterone receptor negative (PR-) breast cancers (HER2+/ER-/PR- BC), an aggressive subtype of breast cancers that cause significant morbidity and mortality. We identified 11 alternative splice isoforms that were differentially expressed in HER2+/ER-/PR- BC compared to normal mammary, triple negative breast cancer and triple positive breast cancer tissues (HER2+/ER+/PR+). We used a stringent criterion that differentially expressed noncanonical isoforms (adjusted p value < 0.05) and have to be expressed in all replicates of HER2+/ER-/PR- BC samples, and the trend in differential expression (up or down) is the same in all comparisons. Of the 11 protein isoforms, six were overexpressed in HER2+/ER-/PR- BC. We explored possible functional roles of these six proteins using several complementary computational tools. Biological processes including cell cycle events and glycolysis were linked to four of these proteins. For example, glycolysis was the top ranking functional process for DMXL2 isoform 3, with a fold change of 27 compared to just two for the canonical protein. No previous reports link DMXL2 with any metabolic processes; the canonical protein is known to participate in signaling pathways. Our results clearly indicate distinct functions for the six overexpressed alternative splice isoforms, and these functions could be specific to HER2+/ER-/PR- tumor progression. Further detailed analysis is warranted as these proteins could be explored as potential biomarkers and therapeutic targets for HER2+/ER-/PR- BC patients.

HER2 and uPAR cooperativity contribute to metastatic phenotype of HER2-positive breast cancer

Human epidermal growth factor receptor type 2 (HER2)-positive breast carcinoma is highly aggressive and mostly metastatic in nature though curable/manageable in part by molecular targeted therapy. Recent evidence suggests a subtype of cells within HER2-positive breast tumors that concomitantly expresses the urokinase plasminogen activator receptor (uPAR) with inherent stem cell/mesenchymal-like properties promoting tumor cell motility and a metastatic phenotype. This HER-positive/uPAR-positive subtype may be partially responsible for the failure of HER2-targeted treatment strategies. Herein we discuss and substantiate the cumulative preclinical and clinical evidence on HER2-uPAR cooperativity in terms of gene co-amplification and/or mRNA/protein co-overexpression. We then propose a regulatory signaling model that we hypothesize to maintain upregulation and cooperativity between HER2 and uPAR in aggressive breast cancer. An improved understanding of the HER2/uPAR interaction in breast cancer will provide critical biomolecular information that may help better predict disease course and response to therapy.

Directional secretomes reflect polarity-specific functions in an in vitro model of human bronchial epithelium

The polarity of the conducting airway epithelium is responsible for its directional secretion. This is an essential characteristic of lung integrity and function that dictates interactions between the external environment (apical) and subepithelial structures (basolateral). Defining the directional secretomes in the in vitro human bronchial epithelial (HBE) differentiated model could bring valuable insights into lung biology and pulmonary diseases. Normal primary HBE cells (n = 3) were differentiated into respiratory tract epithelium. Apical and basolateral secretions (24 h) were processed for proteome profiling and pathway analysis. A total of 243 proteins were identified in secretions from all HBE cultures combined. Of these, 51% were classified as secreted proteins, including true secreted proteins (36%) and exosomal proteins (15%). Close examination revealed consistent secretion of 69 apical proteins and 13 basolateral proteins and differential secretion of 25 proteins across all donors. Expression of Annexin A4 in apical secretions and Desmoglein-2 in basolateral secretions was validated using Western blot or ELISA in triplicate independent experiments. To the best of our knowledge, this is the first study defining apical and basolateral secretomes in the in vitro differentiated HBE model. The data demonstrate that epithelial polarity directs protein secretion with different patterns of biological processes to the apical and basolateral surfaces that are consistent with normal bronchial epithelium homeostatic functions. Applying this in vitro directional secretome model to lung diseases may elucidate their molecular pathophysiology and help define potential therapeutic targets.

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.

Identification of p130Cas/ErbB2-dependent invasive signatures in transformed mammary epithelial cells

Understanding transcriptional changes during cancer progression is of crucial importance to develop new and more efficacious diagnostic and therapeutic approaches. It is well known that ErbB2 is overexpressed in about 25% of human invasive breast cancers. We have previously demonstrated that p130Cas overexpression synergizes with ErbB2 in mammary cell transformation and promotes ErbB2-dependent invasion in three-dimensional (3D) cultures of human mammary epithelial cells. Here, by comparing coding and non-coding gene expression profiles, we define the invasive signatures associated with concomitant p130Cas overexpression and ErbB2 activation in 3D cultures of mammary epithelial cells. Specifically, we have found that genes involved in amino acids synthesis (CBS, PHGDH), cell motility, migration (ITPKA, PRDM1), and angiogenesis (HEY1) are upregulated, while genes involved in inflammatory response (SAA1, S100A7) are downregulated. In parallel, we have shown that the expression of specific miRNAs is altered. Among these, miR-200b, miR-222, miR-221, miR-R210, and miR-424 are upregulated, while miR-27a, miR-27b, and miR-23b are downregulated. Overall, this study presents, for the first time, the gene expression changes underlying the invasive behavior following p130Cas overexpression in an ErbB2 transformed mammary cell model.

Epidermal growth factors in the kidney and relationship to hypertension

Members of the epidermal growth factor (EGF)-family bind to ErbB (EGFR)-family receptors that play an important role in the regulation of various fundamental cell processes in many organs including the kidney. In this field, most of the research efforts are focused on the role of EGF-ErbB axis in cancer biology. However, many studies indicate that abnormal ErbB-mediated signaling pathways are critical in the development of renal and cardiovascular pathologies. The kidney is a major site of the EGF-family ligands synthesis, and it has been shown to express all four members of the ErbB receptor family. The study of kidney disease regulation by ErbB receptor ligands has expanded considerably in recent years. In vitro and in vivo studies have provided direct evidence of the role of ErbB signaling in the kidney. Recent advances in the understanding of how the proteins in the EGF-family regulate sodium transport and development of hypertension are specifically discussed here. Collectively, these results suggest that EGF-ErbB signaling pathways could be major determinants in the progress of renal lesions, including its effects on the regulation of sodium reabsorption in collecting ducts.

Role of epidermal growth factor receptor in acute and chronic kidney injury

Epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase. Its activation results in beneficial or detrimental consequences, depending on the particular setting. Earlier studies in the animal model of acute kidney injury showed that EGFR activation promotes renal tubular cell proliferation. Activation of EGFR by its exogenous ligands, like EGF, can enhance recovery of renal function and structure following acute kidney injury. However, recent studies indicated that EGFR activation also contributes to development and progression of renal diseases in animal models of obstructive nephropathy, diabetic nephropathy, hypertensive nephropathy, and glomerulonephritis through mechanisms involved in activation of renal interstitial fibroblasts, induction of tubular atrophy, overproduction of inflammatory factors, and/or promotion of glomerular and vascular injury. This review highlights the actions and mechanisms of EGFR in a variety of acute and chronic kidney injuries.

Dynamic phosphorylation of tyrosine 665 in pseudopodium-enriched atypical kinase 1 (PEAK1) is essential for the regulation of cell migration and focal adhesion turnover

Pseudopodium-enriched atypical kinase 1 (PEAK1) is a recently described tyrosine kinase that associates with the actin cytoskeleton and focal adhesion (FA) in migrating cells. PEAK1 is known to promote cell migration, but the responsible mechanisms remain unclear. Here, we show that PEAK1 controls FA assembly and disassembly in a dynamic pathway controlled by PEAK1 phosphorylation at Tyr-665. Knockdown of endogenous PEAK1 inhibits random cell migration. In PEAK1-deficient cells, FA lifetimes are decreased, FA assembly times are shortened, and FA disassembly times are extended. Phosphorylation of Tyr-665 in PEAK1 is essential for normal PEAK1 localization and its function in the regulation of FAs; however, constitutive phosphorylation of PEAK1 Tyr-665 is also disruptive of its function, indicating a requirement for precise spatiotemporal regulation of PEAK1. Src family kinases are required for normal PEAK1 localization and function. Finally, we provide evidence that PEAK1 promotes cancer cell invasion through Matrigel by a mechanism that requires dynamic regulation of Tyr-665 phosphorylation.

Characterization of the diffusion of epidermal growth factor receptor clusters by single particle tracking

A number of studies have shown that receptors of the epidermal growth factor receptor family (ErbBs) exist as higher-order oligomers (clusters) in cell membranes in addition to their monomeric and dimeric forms. Characterizing the lateral diffusion of such clusters may provide insights into their dynamics and help elucidate their functional relevance. To that end, we used single particle tracking to study the diffusion of clusters of the epidermal growth factor (EGF) receptor (EGFR; ErbB1) containing bound fluorescently-labeled ligand, EGF. EGFR clusters had a median diffusivity of 6.8×10(-11)cm(2)/s and were found to exhibit different modes of transport (immobile, simple, confined, and directed) similar to that previously reported for single EGFR molecules. Disruption of actin filaments increased the median diffusivity of EGFR clusters to 10.3×10(-11)cm(2)/s, while preserving the different modes of diffusion. Interestingly, disruption of microtubules rendered EGFR clusters nearly immobile. Our data suggests that microtubules may play an important role in the diffusion of EGFR clusters either directly or perhaps indirectly via other mechanisms. To our knowledge, this is the first report probing the effect of the cytoskeleton on the diffusion of EGFR clusters in the membranes of live cells.

Girdin locates in centrosome and midbody and plays an important role in cell division

Girdin is a downstream effector of epidermal growth factor receptor (EGFR)-AKT and interacts with actin and microtubule. Increasing evidence confirmed that Girdin played an important role in cell migration. Here we report that Girdin also regulates cell division. Overexpression or suppression of Girdin leads to attenuated cell proliferation. Imaging of mitotic cells revealed that Girdin is located in the cell division apparatus such as centrosome and midbody. The sub-cellular localization of Girdin was dependent on the domains, which interacted with actin or microtubules. Overexpression of Girdin lead to increased centrosome splitting and amplification. In addition, data show that pAKT also locates in both the centrosome and midbody, indicating the regulating role of AKT in Girdin-mediated cell division. To elucidate the effect of Girdin on tumor growth in vivo, HeLa cells infected with retrovirus harboring either control or Girdin shRNAs were injected subcutaneously into the immunocompromised nude mice. Downregulation of Girdin by shRNA markedly inhibited the cell growth of subcutaneously transplanted tumors in nude mice. These data demonstrate that Girdin is important for efficient cell division. Taking our previous data into consideration, we speculate that Girdin regulates both cell division and cell migration through cytoskeletal molecules.

ErbB-2 signals through Plexin-B1 to promote breast cancer metastasis

Diagnosis of metastatic breast cancer is associated with a very poor prognosis. New therapeutic targets are urgently needed, but their development is hampered by a lack of understanding of the mechanisms leading to tumor metastasis. Exemplifying this is the fact that the approximately 30% of all breast cancers overexpressing the receptor tyrosine kinase ErbB-2 are characterized by high metastatic potential and poor prognosis, but the signaling events downstream of ErbB-2 that drive cancer cell invasion and metastasis remain incompletely understood. Here we show that overexpression of ErbB-2 in human breast cancer cell lines leads to phosphorylation and activation of the semaphorin receptor Plexin-B1. This was required for ErbB-2-dependent activation of the pro-metastatic small GTPases RhoA and RhoC and promoted invasive behavior of human breast cancer cells. In a mouse model of ErbB-2-overexpressing breast cancer, ablation of the gene encoding Plexin-B1 strongly reduced the occurrence of metastases. Moreover, in human patients with ErbB-2-overexpressing breast cancer, low levels of Plexin-B1 expression correlated with good prognosis. Our data suggest that Plexin-B1 represents a new candidate therapeutic target for treating patients with ErbB-2-positive breast cancer.

Adjuvant trastuzumab in HER2-positive breast cancer

BACKGROUND

Trastuzumab improves survival in the adjuvant treatment of HER-positive breast cancer, although combined therapy with anthracycline-based regimens has been associated with cardiac toxicity. We wanted to evaluate the efficacy and safety of a new nonanthracycline regimen with trastuzumab.

METHODS

We randomly assigned 3222 women with HER2-positive early-stage breast cancer to receive doxorubicin and cyclophosphamide followed by docetaxel every 3 weeks (AC-T), the same regimen plus 52 weeks of trastuzumab (AC-T plus trastuzumab), or docetaxel and carboplatin plus 52 weeks of trastuzumab (TCH). The primary study end point was disease-free survival. Secondary end points were overall survival and safety.

RESULTS

At a median follow-up of 65 months, 656 events triggered this protocol-specified analysis. The estimated disease-free survival rates at 5 years were 75% among patients receiving AC-T, 84% among those receiving AC-T plus trastuzumab, and 81% among those receiving TCH. Estimated rates of overall survival were 87%, 92%, and 91%, respectively. No significant differences in efficacy (disease-free or overall survival) were found between the two trastuzumab regimens, whereas both were superior to AC-T. The rates of congestive heart failure and cardiac dysfunction were significantly higher in the group receiving AC-T plus trastuzumab than in the TCH group (P<0.001). Eight cases of acute leukemia were reported: seven in the groups receiving the anthracycline-based regimens and one in the TCH group subsequent to receiving an anthracycline outside the study.

CONCLUSIONS

The addition of 1 year of adjuvant trastuzumab significantly improved disease-free and overall survival among women with HER2-positive breast cancer. The risk-benefit ratio favored the nonanthracycline TCH regimen over AC-T plus trastuzumab, given its similar efficacy, fewer acute toxic effects, and lower risks of cardiotoxicity and leukemia. (Funded by Sanofi-Aventis and Genentech; BCIRG-006 ClinicalTrials.gov number, NCT00021255.).

Epidermal growth factor-mediated proliferation and sodium transport in normal and PKD epithelial cells

Members of the epidermal growth factor (EGF) family bind to ErbB (EGFR) family receptors which play an important role in the regulation of various fundamental cell processes including cell proliferation and differentiation. The normal rodent kidney has been shown to express at least three members of the ErbB receptor family and is a major site of EGF ligand synthesis. Polycystic kidney disease (PKD) is a group of diseases caused by mutations in single genes and is characterized by enlarged kidneys due to the formation of multiple cysts in both kidneys. Tubule cells proliferate, causing segmental dilation, in association with the abnormal deposition of several proteins. One of the first abnormalities described in cell biological studies of PKD pathogenesis was the abnormal mislocalization of the EGFR in cyst lining epithelial cells. The kidney collecting duct (CD) is predominantly an absorptive epithelium where electrogenic Na(+) entry is mediated by the epithelial Na(+) channel (ENaC). ENaC-mediated sodium absorption represents an important ion transport pathway in the CD that might be involved in the development of PKD. A role for EGF in the regulation of ENaC-mediated sodium absorption has been proposed. However, several investigations have reported contradictory results indicating opposite effects of EGF and its related factors on ENaC activity and sodium transport. Recent advances in understanding how proteins in the EGF family regulate the proliferation and sodium transport in normal and PKD epithelial cells are discussed here. This article is part of a Special Issue entitled: Polycystic Kidney Disease.

Estrogen stimulation of cell migration involves multiple signaling pathway interactions

Hormone-dependent breast cancers respond to inhibitors of estrogen synthesis or action with tumor regression and with a reduction of new metastases. The mechanisms underlying the effects of estrogen on metastasis likely differ from those on tumor regression. Cell migration is a key first step in the metastatic process. Based on our prior work and other published data, we designed and tested a working model that suggested that estrogen receptor α, epidermal growth factor receptor, focal adhesion kinase (FAK), paxillin, phosphatidylinositol 3 kinase, p60 Src tyrosine kinase (c-Src), c-Jun N-terminal kinase, and MAPK interact to facilitate estradiol (E(2))-induced cell migration. Accordingly, we examined the effect of E(2) on activation of these pathways and demonstrated mechanistic effects by blocking each component and assessing cell migration as a biologic endpoint. Initial studies validated a robust cell migration assay characterized by highly reproducible, dose-dependent responses to E(2). Examining various mechanisms involved in migration, we showed that E(2) induced activation of c-Src, FAK, and paxillin with early peaks within 5-30 min and later peaks at 24 h. ERK and protein kinase B phosphorylation exhibited only early peaks. Blockade of various steps in these signaling pathways with use of small interfering RNA or specific inhibitors demonstrated mechanistic effects of these signaling molecules on cell migration. Our results suggest that the effects of E(2) on cell migration involve multiple, interacting signaling pathways. Important effects are mediated by the MAPK, phosphatidylinositol 3 kinase, and c-Jun N-terminal kinase pathways and use FAK, paxillin, and c-Src for activation. Each pathway represents a potential target for blocking cell migration and metastasis of breast cancer cells.

Autoproteolysis of the SEA module of rMuc3 C-terminal domain modulates its functional composition

rMuc3 is a typical transmembrane mucin and contains a 174 amino acid domain called an SEA module in its C-terminal domain which is cleaved in eukaryotic cells. However, the mechanism by which the rMuc3 SEA module is proteolyzed and its biological significance has to be elucidated. In this study, we showed that the rMuc3 C-terminal domain was cleaved at LSKGSIVV motif within SEA module in prokaryotic cells, the time-dependence of the cleavage was found in the purified rMuc3 C-terminal domain carrying a mutated LSKASIVV motif expressed in bacteria. Thus, the cleavage of rMuc3 SEA module depended on autoproteolysis. The autoproteolysis of the SEA module of rMuc3 C-terminal domain played a critical role in the migration and invasion of the LoVo human colon cancer cells with rMuc3 C-terminal domain in vitro. The rMuc3 C-terminal domain induced a significant activation of HER/ErbB2 phosphorylated form (py1248) in LoVo cells. Inhibition of the phosphorylation by gefitinib (ZD1839) did attenuate migration and invasion of LoVo cells with rMuc3 C-terminal domain. Thus, rMuc3 C-terminal domain undergoes autoproteolysis at its SEA module, which maintains its availability for the potentiation of the signaling process that is modulated by HER/ErbB2 phosphorylation to promote the migration and invasion of LoVo cells.

ErbB/EGF signaling and EMT in mammary development and breast cancer

Activation of the ErbB family of receptor tyrosine kinases via cognate Epidermal Growth Factor (EGF)-like peptide ligands constitutes a major group of related signaling pathways that control proliferation, survival, angiogenesis and metastasis of breast cancer. In this respect, clinical trials with various ErbB receptor blocking antibodies and specific tyrosine kinase inhibitors have proven to be partially efficacious in the treatment of this heterogeneous disease. Induction of an embryonic program of epithelial-to-mesenchymal transition (EMT) in breast cancer, whereupon epithelial tumor cells convert to a more mesenchymal-like phenotype, facilitates the migration, intravasation, and extravasation of tumor cells during metastasis. Breast cancers which exhibit properties of EMT are highly aggressive and resistant to therapy. Activation of ErbB signaling can regulate EMT-associated invasion and migration in normal and malignant mammary epithelial cells, as well as modulating discrete stages of mammary gland development. The purpose of this review is to summarize current information regarding the role of ErbB signaling in aspects of EMT that influence epithelial cell plasticity during mammary gland development and tumorigenesis. How this information may contribute to the improvement of therapeutic approaches in breast cancer will also be addressed.

EGF and its related growth factors mediate sodium transport in mpkCCDc14 cells via ErbB2 (neu/HER-2) receptor

Amiloride-sensitive sodium entry, via the epithelial sodium channel (ENaC), is the rate-limiting step for Na(+) absorption. Epidermal growth factor (EGF) is involved in the regulation of Na(+) transport and ENaC activity. However it is still controversial exactly how EGF regulates ENaC and Na(+) absorption. The aim of the present study was to characterize the EGF regulation of Na(+) transport in cultured mouse renal collecting duct principal mpkCCD(c14) cells, a highly differentiated cell line which retains many characteristics of the cortical collecting duct (CCD). EGF dose dependently regulates basal transepithelial Na(+) transport in two phases: an acute phase (<4 h) and a chronic phase (>8 h). Similar effects were observed with TGF-alpha, HB-EGF, and amphiregulin which also belong to the EGF-related peptide growth factor family. Inhibition of MEK1/2 by PD98059 or U0126 increased acute effects and disrupted chronic effects of EGF on Na(+) reabsorption. Inhibition of PI3-kinase with LY294002 abolished acute effect of EGF. As assessed by Western blotting, ErbB2 is the most predominant member of the ErbB family detected in mpkCCD(c14) cells. Immunohistochemistry analysis revealed localization of ErbB2 in the CCD in Sprague-Dawley rat kidneys. Both acute and long-term effects of EGF were abolished when cells were treated with tyrphostin AG-825 and ErbB2 inhibitor II, chemically dissimilar selective inhibitors of the ErbB2 receptor. Thus, we conclude that EGF and its related growth factors are important for maintaining transepithelial Na(+) transport and that EGF biphasically modulates sodium transport in mpkCCD(c14) cells via the ErbB2 receptor.