Salivary gland cancer represents a heterogeneous group of malignant tumors. Due to their low incidence and the existence of multiple morphologically defined subtypes, these tumors are still poorly understood with regard to their molecular pathogenesis and therapeutically relevant genetic alterations.Performing a systematic and comprehensive study covering 13 subtypes of salivary gland cancer, next generation sequencing was done on 84 tissue samples of parotid gland cancer using multiplex PCR for enrichment of cancer related gene loci covering hotspots of 46 cancer genes.Mutations were identified in 22 different genes. The most frequent alterations affected TP53, followed by RAS genes, PIK3CA, SMAD4 and members of the ERB family. HRAS mutations accounted for more than 90% of RAS mutations, occurring especially in epithelial-myoepithelial carcinomas and salivary duct carcinomas. Additional mutations in PIK3CA also affected particularly epithelial-myoepithelial carcinomas and salivary duct carcinomas, occurring simultaneously with HRAS mutations in almost all cases, pointing to an unknown and therapeutically relevant molecular constellation. Interestingly, 14% of tumors revealed mutations in surface growth factor receptor genes including ALK, HER2, ERBB4, FGFR, cMET and RET, which might prove to be targetable by new therapeutic agents. 6% of tumors revealed mutations in SMAD4.In summary, our data provide novel insight into the fundamental molecular heterogeneity of salivary gland cancer, relevant in terms of tumor classification and the establishment of targeted therapeutic concepts.

OBJECTIVE

To investigate the association between hepatocellular carcinoma (HCC) susceptibility and a 12-bp insertion/deletion polymorphism (rs6147150) in the 3'UTR of ErbB4.

METHODS

Using a case-control design, the rs6147150 genotypes in 270 patients with HCC and 270 healthy controls were determined by direct polymerase chain reaction and polyacrylamide gel electrophoresis. Logistic regression was used to analyze the association between the polymorphism and cancer risk.

RESULTS

Computational modeling suggested that rs6147150 was located in the seed region of hsa-let-7c, a potential target sequence in ErbB4 3'UTR. Logistic regression analysis showed that, compared with individuals homozygous for wild-type, heterozygotes [adjusted odds ratio (OR) = 1.48, 95% confidence interval (CI) = 1.03-2.17, P = 0.034] and individuals homozygous for 12-bp del/del (OR = 2.50, 95% CI = 1.37-4.56, P = 0.001) were at significantly higher risk of HCC. Carriers of the "del" allele of rs6147150 had a 1.59-fold increased risk for HCC (95% CI = 1.22-2.07, P = 0.003).

CONCLUSIONS

rs6147150 may be associated with HCC risk, in part through let-7c-mediated regulation, and may be involved in the pathogenesis of HCC in Chinese populations.

The epidermal growth factor receptor (EGFR) gives name to a family of receptors formed by four members in mammals (EGFR, ErbB2, ErbB3, and ErbB4). Members of this family can be activated to become potent oncogenes, and many human and animal tumors express qualitatively or quantitatively altered receptors from this group. We have isolated and characterized a second egfr gene in the melanoma model fish Xiphophorus. Both Xiphophorus egfra and egfrb duplicates are co-orthologs of the mammalian egfr gene. Database analysis showed that not only egfr but also erbB3 and erbB4 are present as duplicates in some fish species. They originated from ancient duplication events that might be consistent with the hypothesis of a fish-specific genome duplication. In Xiphophorus, the egfrb gene underwent a second duplication that generated the melanoma-inducing oncogene Xmrk. The study and comparison of some of the functional characteristics of both Xiphophorus EGF receptors, including expression profile, ligand-binding abilities, and intracellular signal transduction revealed that Xiphophorus Egfra not only shares common features with Egfrb and the human EGFR but also shows significant differences in its functional characteristics. The mechanism of maintenance of these duplicates remains to be clarified.

Sex differences in the magnitude of response to thermal and tactile stimuli have been demonstrated in both clinical and animal studies. Females typically display lower threshold responses to painful stimuli as compared to males. We have previously observed sexually dimorphic expression of the growth factor, neuregulin 1 (NRG1) following L5 nerve root ligation (LR) in male and female rats. In the present study, we sought to determine which gonadal hormones were involved in regulating NRG1 expression following L5 nerve root ligation. We observed that expression of NRG1 mRNA and the neuregulin receptors, ErbB2 and ErbB4 in the lumbar spinal cord was facilitated by the presence of progesterone in female rats following L5 nerve root ligation. An increase in NRG1 protein and NRG1 immunoreactivity was also observed in the ipsilateral spinal cord of progesterone treated female rats as compared to ovariectomized female rats and male rats at day 14 following LR. NRG1 immunoreactivity was equally colocalized with either the astrocytic marker, GFAP, and with NeuN labeled neurons 14days following L5 nerve root ligation. Intrathecal administration of recombinant NRG1-beta1 protein significantly decreased the hindpaw tactile withdrawal threshold in male rats, ovariectomized female rats, and progesterone treated female rats. These results demonstrate a role for progesterone-dependent regulation of glial and/or neuronal neuregulin 1 in female rats in mediating sex differences in nociception. Furthermore, our results suggest that NRG1 may be involved in central sensitization during the maintenance phase, but not in the initiation of persistent pain in female rats.

Differentiation of mammary epithelium in vivo requires signaling through prolactin and ErbB4/HER4-dependent mechanisms. Although stimulation of either the prolactin receptor or ErbB4/HER4 results in activation of the transcription factor signal transducer and activator of transcription 5A (STAT5A) and induction of lactogenic differentiation, how these pathways intersect is unknown. We show herein that prolactin signaling in breast cells cooperates with and is substantially enhanced by the receptor tyrosine kinase ErbB4/HER4. Prolactin and the ErbB4/HER4 ligand heparin-binding epidermal growth factor each induced STAT5A tyrosine phosphorylation and nuclear translocation; each pathway required the intracellular tyrosine kinase Janus kinase 2 (JAK2). We found that full prolactin-mediated STAT5A activation and binding to the endogenous beta-casein promoter required ErbB4/HER4 but did not require ErbB1/epidermal growth factor receptor. For example, prolactin-induced STAT5A activity was markedly diminished in cells overexpressing kinase inactive HER4, in cells transfected with small interfering RNAs to specifically knock down endogenous ErbB4/HER4 expression and in cells treated with a small molecule inhibitor that targets ErbB4 kinase. Interestingly, prolactin caused ErbB4/HER4 tyrosine phosphorylation in a JAK2 kinase-dependent manner. Finally, prolactin receptor, ErbB4/HER4, and JAK2 were coimmunoprecipitated from prolactin-treated but not untreated cells. These results suggest that prolactin signaling engages the ErbB4 pathway via JAK2 and that ErbB4 provides an important component of STAT5A-dependent lactogenic differentiation; this pathway integration may help explain the similar deficit in mammary development observed in gene-targeted mice deficient in prolactin receptor, JAK2, ErbB4, or STAT5A.

Co-expression of ERBB2 and ERBB4, reported in 75% of pediatric ependymomas, correlates with worse overall survival. Lapatinib, a selective ERBB1 and ERBB2 inhibitor has produced prolonged disease stabilization in patients with ependymoma in a phase I study. Bevacizumab exposure in ependymoma xenografts leads to ablation of tumor self-renewing cells, arresting growth. Thus, we conducted an open-label, phase II study of bevacizumab and lapatinib in children with recurrent ependymomas. Patients ≤ 21 years of age with recurrent ependymoma received lapatinib orally twice daily (900 mg/m(2)/dose to the first 10 patients, and then 700 mg/m(2)/dose) and bevacizumab 10 mg/kg intravenously on days 1 and 15 of a 28-day course. Lapatinib serum trough levels were analyzed prior to each course. Total and phosphorylated VEGFR2 expression was measured in peripheral blood mononuclear cells (PBMCs) before doses 1 and 2 of bevacizumab and 24-48 h following dose 2 of bevacizumab. Twenty-four patients with a median age of 10 years (range 2-21 years) were enrolled; 22 were eligible and 20 evaluable for response. Thirteen had anaplastic ependymoma. There were no objective responses; 4 patients had stable disease for ≥ 4 courses (range 4-14). Grade 3 toxicities included rash, elevated ALT, and diarrhea. Grade 4 toxicities included peri-tracheostomy hemorrhage (n = 1) and elevated creatinine phosphokinase (n = 1). The median lapatinib pre-dose trough concentration was 3.72 µM. Although the combination of bevacizumab and lapatinib was well tolerated in children with recurrent ependymoma, it proved ineffective.

OBJECTIVE

Exercise training (ET) has a cardioprotective effect and can alter the molecular response to myocardial infarction (MI). The Neuregulin 1 (NRG1)/ErbB signaling plays a critical role in cardiac repair and regeneration in the failing heart. We sought to investigate whether ET following MI could activate the NRG1/ErbB signaling and promote cardiac repair and regeneration.

METHODS

Male Sprague-Dawley rats were used to establish the MI model. Exercise-trained animals were subjected to four weeks of exercise (16m/min, 50min/d, 5d/wk) following the surgery. AG1478 was used as an inhibitor of ErbB (1mg/kg body weight, administered i.v. every other day during the process of training). NRG1/ErbB signaling activation, cardiomyocyte (CM) proliferation and apoptosis were evaluated.

RESULTS

In the exercise-trained rats, NRG1 expression was up-regulated and ErbB/PI3K/Akt signaling was activated compared with the MI group. In addition, ET preserved heart function accompanied with increased numbers of BrdU(+) CMs, PCNA(+) CMs and c-kit(+) cells, and reduced apoptosis level in the MI rats. In contrast, blocking ErbB signaling by AG1478 attenuated the ET-induced cardiac repair and regeneration.

CONCLUSIONS

ET up-regulates NRG1 expression and activates ErbB2, ErbB4 and PI3K/Akt signal transduction to promote cardiac repair through endogenous regeneration. Activation of ErbB may be an underlying mechanism for the ET-induced cardiac repair and regeneration following MI.

Chromosome 3p was reported by previous studies as one of the regions showing strong evidence of linkage with schizophrenia. We performed a fine-mapping association study of a 6-Mb high-LD and gene-rich region on 3p in a Southern Chinese sample of 489 schizophrenia patients and 519 controls to search for susceptibility genes. In the initial screen, 4 SNPs out of the 144 tag SNPs genotyped were nominally significant (P < 0.05). One of the most significant SNPs (rs3732530, P = 0.0048) was a non-synonymous SNP in the neuroglycan C (NGC, also known as CSPG5) gene, which belongs to the neuregulin family. The gene prioritization program Endeavor ranked NGC 8th out of the 129 genes in the 6-Mb region and the highest among the genes within the same LD block. Further genotyping of NGC revealed 3 more SNPs to be nominally associated with schizophrenia. Three other genes (NRG1, ErbB3, ErbB4) involved in the neuregulin pathways were subsequently genotyped. Interaction analysis by multifactor dimensionality reduction (MDR) revealed a significant two-SNP interaction between NGC and NRG1 (P = 0.015) and three-SNP interactions between NRG1 and ErbB4 (P = 0.009). The gene NGC is exclusively expressed in the brain. It is implicated in neurodevelopment in rats and was previously shown to promote neurite outgrowth. Methamphetamine, a drug that may induce psychotic symptoms, was reported to alter the expression of NGC. Taken together, these results suggest that NGC may be a novel candidate gene, and neuregulin signaling pathways may play an important role in schizophrenia.

Recent genetic evidence indicates that neuregulin 1 (NRG1) and its receptor erbB4 may be susceptibility genes in schizophrenia, but their function in CNS synaptic transmission and circuitry is not well understood. In this issue of Neuron, studies from Li et al. and Woo et al. show that NRG1 and erbB4 regulate transmission at brain glutamate and GABA synapses. These findings raise the possibility of synaptic defects in schizophrenia.

During development and in the adult, erbB2, erbB3, and erbB4 are expressed in many tissues and as heterodimers (B2/B3, B2/B4) serve as receptors for neuregulins. The general importance of neuregulin receptors for development is underlined by the observed embryonic (erbB2, erbB4) or perinatal (erbB3) lethality in mouse mutants. These mutants further revealed the fundamental role of the erbB2/erbB3 heterodimer for proper Schwann cell development, the ensheathing glia of the peripheral nervous system. However, only little is known about the functions of neuregulins and their receptors during postnatal development and in the adult. erbB2 and erbB3 during late embryogenesis and postnatally are expressed in different areas and cell types of the central nervous system, including oligodendrocytes, the ensheathing glia of the central nervous system. As terminal differentiation of oligodendrocytes peaks during postnatal development, it is not possible to use the neuregulin receptor mouse mutants to study terminal differentiation of oligodendrocytes in their absence in vivo. In order to investigate possible functions of the erbB3 gene in oligodendrocytes, we employed two different techniques. First, we directed the differentiation of erbB3-deficient embryonic stem cells into neural cell types to analyze the development of oligodendrocytes in the absence of erbB3 in vitro. Second, we grafted neural stem cells from spinal cords of erbB3 mutants into the retina of young mice to monitor oligodendrocyte differentiation and myelination in vivo. Results of both experimental approaches clearly show that erbB3 is not required for normal oligodendrocyte development and myelination.

Neuregulin-1 (NRG1) signaling participates in the synaptic plasticity, maintenance or regulation of adult brain. Although ErbB4, a key NRG1 receptor, is expressed in multiple regions in the adult animal brain, little is known about its localization in Alzheimer's disease (AD) brains. We previously reported that ErbB4 immunoreactivity showed regional difference in the hippocampus of age-matched control. In the present paper, immunohistochemical characterization of the distribution of ErbB4 receptor in the hippocampus relative to pathology staging were performed in age-matched control (Braak stage 0, n=6) and AD (Braak stage I/V, n=10). Here, we found that ErbB4 immunoreactivity was significantly increased in apoptotic hippocampal pyramidal neurons in the brains of AD patients, compared to those of age-matched control subjects. In AD brains, ErbB4 immunoreactivity was demonstrated to colocalize with the apoptotic signal Bax in apoptotic hippocampal pyramidal neurons. These results suggest that up-regulation of ErbB4 immunoreactivity in apoptotic neuron may involve in the progression of pathology of AD.

In the present study the authors evaluated the expression of the EGFR family members ErbB2-4 in renal cell carcinoma (RCC). Thirty-one RCCs were examined for gene expression of ErbB2-4 mRNA by quantitative real-time RT-PCR. For eight of the patients samples of nonneoplastic kidney cortex were also evaluated. Expression of ErbB4 mRNA was analysed in the eight matched tumour and kidney cortex samples by isoform-specific real-time RT-PCR analysis. ErbB4 protein expression was analysed by immunohistochemistry. In summary the results showed that ErbB2 mRNA was downregulated in conventional (clear cell) RCC; ErbB3 mRNA levels were low and heterogeneous in both tumours and kidney cortex; ErbB4 mRNA and protein were strongly downregulated in conventional and papillary RCC. Thus, ErbB2 and ErbB4 are not likely to be oncogenes in the majority of RCCs; instead, the observed downregulations suggest that these receptors might function as tumour suppressors in RCC.

Neuregulin-1s (NRG-1s) are a family of growth and differentiation factors with multiple roles in the development and function in different organs including the nervous system. Among the proposed functions of NRG-1s in the nervous system is the regulation of genes encoding certain neurotransmitter receptors during synapse formation as well as of other aspects of synaptic function. Here, we have examined, in granule cells of the cerebellum in vivo, the role of NRGs in the induction of NMDA receptor (NMDA-R) and GABA(A) receptor (GABA(A)-R), which are thought to be induced by NRG-1 secreted by the synaptic inputs. To this end, we used the Cre/loxP system to genetically ablate the NRG receptors ErbB2 and ErbB4 selectively in these cells, thus eliminating all NRG-mediated signaling to them. Unlike previous reports using cultured granule cells to address the same question, we found that the developmental expression patterns of the mRNAs encoding the NR2C subunit of the NMDA-R and the beta2-subunit of the GABA(A)-R is normal in mice lacking the NRG receptors ErbB2 and ErbB4. Likewise, no alterations in cerebellar morphology nor in certain aspects of cerebellar wiring were resolved in these mutants. We conclude that NRG/ErbB signaling to the granule cells is dispensable for the normal development of their synaptic inputs.

Cellular, animal and human studies support the involvement of aberrant NRG-ErbB signaling in the pathogenesis of schizophrenia. The aim of the present study was to examine whether genetic variation in the human ERBB4 gene is associated with susceptibility to schizophrenia. Two hundred and twenty-seven unrelated chronic inpatients with schizophrenia were enrolled in the study, and the genetic variation in the polymorphisms of the ERBB4 gene in the patients was compared with that of the control group, which consisted of 223 subjects free of psychiatric illness. The results showed that one coding-synonymous polymorphism (rs3748962, Val1065Val) was in genotypic (p=0.0027) and allelic (p=0.0007) association with schizophrenia. In comparison with subjects of the rs3748962-TT type, those of the rs3748962-CT and rs3748962-CC types were at 1.74- and 2.64-fold greater risk of schizophrenia (CT vs. TT: OR=1.71 (95% CI=1.15-2.53), p=0.0014; CC vs. TT: OR=2.64 (95% CI=1.37-5.23), p=0.0047), which supports the hypothesis of an additive model of transmission (p=0.0006). Furthermore, the frequency of haplotype ATC of rs3791709-rs2289086-rs3748962 was found to be significantly higher in the patients with schizophrenia than in the controls (case vs. control=36.0% vs. 24.4%, permutation p-value=0.0002). The findings support the involvement of the ERBB4 gene in schizophrenia in Han Chinese.

Target identification remains challenging for the field of chemical biology. We describe an integrative chemical genomic and proteomic approach combining the use of differentially active analogs of small molecule probes with stable isotope labeling by amino acids in cell culture-mediated affinity enrichment, followed by subsequent testing of candidate targets using RNA interference-mediated gene silencing. We applied this approach to characterizing the natural product K252a and its ability to potentiate neuregulin-1 (Nrg1)/ErbB4 (v-erb-a erythroblastic leukemia viral oncogene homolog 4)-dependent neurotrophic factor signaling and neuritogenesis. We show that AAK1 (adaptor-associated kinase 1) is a relevant target of K252a, and that the loss of AAK1 alters ErbB4 trafficking and expression levels, providing evidence for a previously unrecognized role for AAK1 in Nrg1-mediated neurotrophic factor signaling. Similar strategies should lead to the discovery of novel targets for therapeutic development.

CONCLUSIONS

Overexpression of ErbB receptors is frequent in head and neck squamous cell carcinomas (HNSCC) and seems to be correlated with tumor progression and metastasis. Fatty acid synthase (FASN), the key lipogenic enzyme responsible for the endogenous synthesis of fatty acids, is regulated by ErbB2 and overexpressed in several human malignancies.

METHODS

This study was performed to examine the immunohistochemical expression patterns of ErbB1, ErbB2, ErbB3, ErbB4, and FASN in a tissue microarray, containing 33 representative areas from aggressive primary HNSCC (whose patients had distant metastasis), and 21 matched lung metastasis.

RESULTS

Strong correlation among the expression of ErbB family receptors was found (ErbB1-ErbB2 P = 0.008, ErbB1-ErbB4 P = 0.018, EbB2-ErbB3 P = 0.001, ErbB2-ErbB4 P = 0.006, ErbB3-ErbB4 P=0.012) in the HNSCC. FASN expression was significantly associated with ErbB2 (P = 0.024). Lymphatic permeation was correlated with ErbB3 (P = 0.033) and histological grade with ErbB4 staining (P = 0.050). ErbB1 and ErbB2 were found mainly in patients with smoking habit (P = 0.011 and P = 0.027), and ErbB2 was associated with alcohol consumption and clinical stage (P = 0.014 and P = 0.031). Finally, FASN was overexpressed in lung metastasis, in comparison with matched HNSCC samples (P = 0.006).

CONCLUSIONS

The results showed that high FASN immunohistochemical expression is a feature of HNSCC lung metastasis, and ErbB1-ErbB2, ErbB1-ErbB4, ErbB2-ErbB3, ErbB2-ErbB4, and ErbB3-ErbB4 expression levels are correlated in the respective primary tumors, being ErbB2 the preferred coexpression partner of all the other ErbB receptors.

Neuregulin 1 (NRG1) is a susceptibility gene for schizophrenia. A decrease in NRG1-ErbB4 signalling has also been associated with the disease. β-amyloid precursor protein-cleaving enzyme (BACE1) processes type III NRG1 precursor, a major neuregulin variant expressed in the brain, to release NRG1 fragments that trigger signalling events and activation of neurotransmitter receptors. Experimental evidence suggests that muscarinic acetylcholine receptors (CHRM) regulate BACE1 expression. Having recently shown that CHRM1 levels are decreased selectively in frontal cortex regions of a subpopulation of schizophrenic patients (muscarinic receptor deficit schizophrenia, MRDS) we aimed to compare the protein expression of BACE1 and NRG1 in the agranular frontal cortex Brodmann's area 6 of SCZ subjects with normal levels of CHRM1 (N = 19), MRDS (N = 20), and age/gender-matched non-psychiatric (healthy) controls (HC; N = 20). Western blot analysis of post-mortem samples showed that the levels of BACE1 and full-length NRG1 precursor (130 kDa) did not differ significantly between the three groups. In contrast, the levels of the NRG1 C-terminal fragment (NRG1-CTF) were decreased by approximately 50% in both schizophrenic groups compared to the HC group (p<0.0027). The ratio of NRG1-CTF versus NRG1 precursor was significantly reduced in the SCZ groups compared to the HC group (p = 0.051). There was no correlation between the levels of either full-length NRG1, NRG1-CTF, or BACE1 and the final recorded doses of antipsychotic drugs for the subjects with schizophrenia. A positive correlation was found between BACE1 and full-length NRG1 precursor in the HC group (r(2) = 0.671, p<0.001) but not in the schizophrenic groups. These data suggest that the proteolytic processing of NRG1 is impaired in schizophrenia.

During embryonic development, the oligodendrocyte precursors (OPCs) are generated in specific oligodendrogliogenic sites within the neural tube and migrate to colonize the entire CNS. Different factors have been shown to influence the OPC migration and differentiation, including morphogens, growth factors, chemotropic molecules, and extracellular matrix proteins. Neuregulins have been shown to influence the migration of neuronal precursors as well as the movement and differentiation of Schwann cells for peripheral myelination, but their role in the motility of OPCs has not been explored. In the present study, we have used the optic nerve as an experimental model to examine the function of Nrg1 and its ErbB4 receptor in the migration of OPCs in the developing embryo. In vitro experiments revealed that Nrg1 is a potent chemoattractant for the first wave of OPCs, and that this effect is mediated via ErbB4 receptor. In contrast, OPCs colonizing the optic nerve at postnatal stages (PDGFRα(+)-OPCs) does not respond to Nrg1-chemoattraction. We also found that mouse embryos lacking ErbB4 display deficits in early OPC migration away from different oligodendrogliogenic regions in vivo. The present findings reveal a new role for Nrg1/ErbB4 signaling in regulating OPC migration selectively during early stages of CNS development.

Trastuzumab, a monoclonal antibody that is selective for cells that overexpress the erbB2 receptor protein tyrosine kinase, is a promising targeted therapy for the treatment of breast cancer. Surprisingly, toxic cardiovascular side effects were discovered in late-phase clinical trials, and these effects were most prominent when trastuzumab was combined with anthracycline chemotherapy. We review recent data focusing on how erbB2 monoclonal antibodies could exert a cardiotoxic effect through unique cardiomyocyte cell surface and intracellular structural features, and how an individual's cardiac susceptibility to erbB2 monoclonal antibodies may be dictated by the ability of erbB2 monoclonal antibodies to bind cardiomyocytes. In addition, we discuss ways that anthracyclines may also affect erbB2/erbB4/neuregulin receptor signaling, explaining the apparent synergistic effect. Further investigation of the role of normal and aberrant erbB2 signaling in the development of cardiac dysfunction could lead to an improved understanding of the pathophysiology of cardiac dysfunction and may lead to novel therapies for the treatment of heart failure, regardless of etiology. Understanding the nature and specificity of trastuzumab's cardiotoxic effects is important in better defining clinical criteria for inclusion and exclusion of patients who can safely receive trastuzumab for the treatment of breast cancer, or possibly other malignancies.

Neuregulin-1 (NRG1) plays important roles in the development and plasticity of the brain, and it is also reported to have potent neuroprotective properties. We previously reported that NRG1 has neuroprotective actions against Swedish amyloid precursor protein-induced neurotoxicity. In addition to the amyloid beta peptide, other metabolites of amyloid precursor protein (APP) such as the C-terminal fragments of APP (APP-CTs) have been reported to possess cytotoxic effects in neuronal cells. In this study, we investigated whether NRG1 exerts neuroprotective effects against APP-CTs and attempted to determine its neuroprotective mechanisms. NRG1 attenuated the neurotoxicities induced by the expression of APP-CTs in neuronal cells. NRG1 also reduced the accumulation of reactive oxygen species and attenuated mitochondrial membrane potential loss induced by APP-CTs. In addition, NRG1 upregulated the expression of the anti-apoptotic protein Bcl-2. This effect was blocked by the inhibition of ErbB4, a key NRG1 receptor. Taken together, these results demonstrate the neuroprotective potential of NRG1 in Alzheimer's disease.

Neuregulin-1 (NRG1) plays important roles in the development and plasticity of the brain, and has also been reported to exhibit potent neuroprotective properties. Although ErbB4, a key NRG1 receptor, is expressed in multiple regions in the adult animal brain, little is known about its role in Alzheimer's disease (AD). AD is characterized by progressive impairment of cognition and behavioral disturbance that strongly correlate with degeneration and death of neurons in the cerebral cortex and limbic brain areas, such as the hippocampus and the amygdala. Here, we show that the ErbB4 and phospho-ErbB4 immunoreactivities were higher intensity in the neurons of the CA1-2 transitional field of AD brains as compared to age-matched controls. Also, ErbB4 expression was increased in the neurons of the cortico medial nucleus amygdala, human basal forebrain and superior frontal gyrus of AD brains. In cerebral cortex and hippocampus of amyloid precursor protein/presenilin 1 double transgenic mice, ErbB4 immunoreactivity significantly increased in comparison to age-matched wild type control. These results suggest that up-regulating of ErbB4 immunoreactivity may involve in the progression of pathology of AD.

Primary breast carcinomas expressing both estrogen and progesterone receptors are most likely to respond to tamoxifen therapy, especially in patients with early-stage lesions. However, certain patients exhibit clinicopathologic features suggesting good prognosis relapse within 10 years, justifying a search for biomarkers identifying patients at risk for recurrence. Nine candidate genes associated with estrogen signaling were selected from microarray studies and combined with those for conventional biomarkers (ESR1, PGR, ERBB2). Expression of this 12-gene subset was analyzed by RT-qPCR in frozen tissue specimens from 60 early-stage, estrogen receptor (ER)+/progestin receptor (PR)+ breast cancers from patients treated with adjuvant tamoxifen. A multivariate model was created by Cox regression using a training data set and applied to an independent validation set. A five-gene model was developed from the training set (n = 36) that exhibited significant correlations with both relapse-free and overall survival. Applying this model to Kaplan-Meier regression, patients were separated into low-risk (100% relapse-free at 150 months) and high-risk (60% relapse-free at 150 months) groups (P = 0.03). When this model was applied to the validation set (n = 24), similar risk stratification was achieved for both relapse-free and overall survival (P = 0.01 and 0.04, respectively). We developed a five-gene model composed of PgR, BCL2, ERBB4 JM-a, RERG, and CD34 that identified early-stage, ER+/PR+ breast cancers in patients treated with tamoxifen that relapsed, although they exhibited clinicopathologic features suggesting good prognosis. Within this multivariate model, increased expression of PgR, ERBB4 JM-a, RERG, and CD34 was associated with increased survival, while increased expression of BCL2 was associated with decreased survival.

Pancreatic cancer is the fourth leading cause of cancer death in the United States. Indeed, it has been estimated that 37,000 Americans will die from this disease in 2010. Late diagnosis, chemoresistance, and radioresistance of these tumors are major reasons for poor patient outcome, spurring the search for pancreatic cancer early diagnostic and therapeutic targets. ErbB4 (HER4) is a member of the ErbB family of receptor tyrosine kinases (RTKs), a family that also includes the Epidermal Growth Factor Receptor (EGFR/ErbB1/HER1), Neu/ErbB2/HER2, and ErbB3/HER3. These RTKs play central roles in many human malignancies by regulating cell proliferation, survival, differentiation, invasiveness, motility, and apoptosis. In this report we demonstrate that human pancreatic tumor cell lines exhibit minimal ErbB4 expression; in contrast, these cell lines exhibit varied and in some cases abundant expression and basal tyrosine phosphorylation of EGFR, ErbB2, and ErbB3. Expression of a constitutively-dimerized and -active ErbB4 mutant inhibits clonogenic proliferation of CaPan-1, HPAC, MIA PaCa-2, and PANC-1 pancreatic tumor cell lines. In contrast, expression of wild-type ErbB4 in pancreatic tumor cell lines potentiates stimulation of anchorage-independent colony formation by the ErbB4 ligand Neuregulin 1β. These results illustrate the multiple roles that ErbB4 may be playing in pancreatic tumorigenesis and tumor progression.