Small tyrosine kinase inhibitors interrupt EGFR signaling by interacting with erbB3 and erbB4 in glioblastoma cell lines

EMP3 sustains oncogenic EGFR/CDK2 signaling by restricting receptor degradation in glioblastoma

Epithelial membrane protein 3 (EMP3) is an N-glycosylated tetraspanin with a putative trafficking function. It is highly expressed in isocitrate dehydrogenase-wild-type glioblastoma (IDH-wt GBM), and its high expression correlates with poor survival. However, the exact trafficking role of EMP3 and how it promotes oncogenic signaling in GBM remain unclear. Here, we show that EMP3 promotes EGFR/CDK2 signaling by regulating the trafficking and enhancing the stability of EGFR. BioID2-based proximity labeling revealed that EMP3 interacts with endocytic proteins involved in the vesicular transport of EGFR. EMP3 knockout (KO) enhances epidermal growth factor (EGF)-induced shuttling of EGFR into RAB7 + late endosomes, thereby promoting EGFR degradation. Increased EGFR degradation is rescued by the RAB7 negative regulator and novel EMP3 interactor TBC1D5. Phosphoproteomic and transcriptomic analyses further showed that EMP3 KO converges into the inhibition of the cyclin-dependent kinase CDK2 and the repression of EGFR-dependent and cell cycle transcriptional programs. Phenotypically, EMP3 KO cells exhibit reduced proliferation rates, blunted mitogenic response to EGF, and increased sensitivity to the pan-kinase inhibitor staurosporine and the EGFR inhibitor osimertinib. Furthermore, EGFR-dependent patient-derived glioblastoma stem cells display a transcriptomic signature consistent with reduced CDK2 activity, as well as increased susceptibility to CDK2 inhibition upon EMP3 knockdown. Lastly, using TCGA data, we showed that GBM tumors with high EMP3 expression have increased total and phosphorylated EGFR levels. Collectively, our findings demonstrate a novel EMP3-dependent mechanism by which EGFR/CDK2 activity is sustained in GBM. Consequently, EMP3's stabilizing effect provides an additional layer of tumor cell resistance against targeted kinase inhibition.

ErbB4 in the brain: Focus on high grade glioma

The epidermal growth factor receptor (EGFR) family of receptor tyrosine kinases (RTKs) consists of EGFR, ErbB2, ErbB3, and ErbB4. These receptors play key roles in cell proliferation, angiogenesis, cell migration, and in some cases, tumor promotion. ErbB4 is a unique member of the EGFR family, implicated not only in pro-tumorigenic mechanisms, such as cell proliferation and migration, but also in anti-tumorigenic activities, including cell differentiation and apoptosis. ErbB4 is differentially expressed in a wide variety of tissues, and interestingly, as different isoforms that result in vastly different signalling outcomes. Most studies have either ignored the presence of these isoforms or used overexpression models that may mask the true function of ErbB4. ErbB4 is widely expressed throughout the body with significant expression in skeletal tissue, mammary glands, heart, and brain. Knockout models have demonstrated embryonic lethality due to disrupted heart and brain development. Despite high expression in the brain and a critical role in brain development, remarkably little is known about the potential signalling activity of ErbB4 in brain cancer.This review focuses on the unique biology of ErbB4 in the brain, and in particular, highlights brain cancer research findings. We end the review with a focus on high grade gliomas, primarily glioblastoma, a disease that has been shown to involve EGFR and its mutant forms. The role of the different ErbB4 isotypes in high grade gliomas is still unclear and future research will hopefully shed some light on this question.

MiR-146a-5p, targeting ErbB4, promotes 3T3-L1 preadipocyte differentiation through the ERK1/2/PPAR-γ signaling pathway

Background

MicroRNAs (MiRNAs) are known to participate in preadipocyte differentiation, but the manner in which miR-146a-5p participates in this process remains unclear. This study was performed to examine the participation of miR-146a-5p in 3T3-L1 cell differentiation.

Material and Methods

miR-146a-5p expression was upregulated and down-regulated to examine effects on 3T3-L1 cell differentiation. Bioinformatics analysis was performed to predict its target genes, and the signaling pathway it regulates was identified by qRT-PCR and Western blotting. The expression of miR-146a-5p in epididymal adipose tissue from obese mice and in an obese mouse adipose cell model was examined by qRT-PCR.

Results

3T3-L1 cells differentiated into mature adipocytes successfully, as verified by increased areas of intracellular lipid droplets and elevated expression of mature adipocyte markers, and these cells had elevated miR-146a-5p expression. The intracellular lipid droplet and triglyceride contents and the expression of mature adipocyte markers were significantly increased in miR-146a-5p–overexpressing 3T3-L1 cells and markedly decreased in miR-146a-5p–inhibited 3T3-L1 cells. ErbB4 was a predicted target gene of miR-146a-5p. In miR-146a-5p–overexpressing 3T3-L1 cells, ErbB4 expression and ERK1/2 phosphorylation were decreased and the expression of PPAR-γ was increased; the opposite was observed in miR-146a-5p–inhibited 3T3-L1 cells. In addition, miR-146a-5p expression was significantly increased in the mouse epididymal adipose tissue and adipose cell model.

Conclusions

Upregulated miR-146a-5p expression was related to 3T3-L1 cell differentiation. MiR-146a-5p promoted 3T3-L1 cell differentiation by targeting ErbB4 and via the ERK1/2/PPAR-γ signaling pathway.

Supplementary information

The online version contains supplementary material available at 10.1186/s12944-022-01662-6.

H-Ferritin nanoparticle-mediated delivery of antibodies across a BBB in vitro model for treatment of brain malignancies

Brain cancers are a group of neoplasms that can be either primary, such as glioblastoma multiforme (GBM), or metastatic, such as the HER2+ breast cancer brain metastasis. The brain represents a sanctuary for cancer cells thanks to the presence of the blood brain barrier (BBB) that controls trafficking of molecules, protecting the brain from toxic substances including drugs. Considering that GBM and HER2+ breast cancer brain metastases are characterized by EGFR and HER2 over-expression respectively, CTX- and TZ-based treatment could be effective. Several studies show that these monoclonal antibodies (mAbs) exert both a cytostatic activity interfering with the transduction pathways of EGFR family and a cytotoxic activity mainly through the immune system activation via the antibody dependent cell-mediated cytotoxicity (ADCC). Since the major limitation to therapeutic mAbs application is the presence of the BBB, here we use a recombinant form of human apoferritin (HFn) as a nanovector to promote the delivery of mAbs to the brain for the activation of the ADCC response. Using a transwell model of the BBB we proved the crossing ability of HFn-mAb. Cellular uptake of HFn-mAb by human cerebral microvascular endothelial cells (hCMEC/D3) was demonstrated by confocal microscopy. Moreover, after crossing the endothelial monolayer, HFn-conjugated mAbs retain their biological activity against targets, as assessed by MTS and ADCC assays. Our data support the use of HFn as efficient carrier to enhance the BBB crossing of mAbs, without affecting their antitumoral activity.

The NRG3/ERBB4 signaling cascade as a novel therapeutic target for canine glioma

Canine glioma is a common brain tumor with poor prognosis despite surgery and/or radiation therapy. Therefore, newer and more effective treatment modalities are needed. Neuregulin 3 (NRG3) has known to be a ligand of ERBB4. This study aimed to investigate the usefulness of the NRG3/ERBB4 signaling cascade as a novel therapeutic target in canine glioma. We found out that microRNA (miR)-190a was downregulated in canine brain tumor tissues, including glioma and meningioma. miR-190a directly targeted NRG3 and inhibited the growth of canine glioma cells. The level of p-Akt, which is a downstream target of ERBB4 signaling, was decreased by transfection with miR-190a. NRG3 silencing also suppressed cell growth and decreased the levels of p-Akt and p-ERK1/2, and NRG3 overexpression exhibited opposed effects in canine glioma J3T-1 cells. The mRNA level of erbb4 was significantly upregulated in glioma tissues compared with that in normal brain tissues and meningioma tissues. Furthermore, compared with gefitinib and lapatinib, afatinib exerted a greater inhibitory effect on the growth of canine glioma cells. In conclusion, NRG3/ERBB4 signaling is negatively regulated by miR-190a and contributes to the growth of canine glioma cells, indicating that it may be a promising therapeutic target in canine glioma.

Aptamer-Based In Vivo Therapeutic Targeting of Glioblastoma

Glioblastoma (GBM) is the most aggressive, infiltrative, and lethal brain tumor in humans. Despite the extensive advancement in the knowledge about tumor progression and treatment over the last few years, the prognosis of GBM is still very poor due to the difficulty of targeting drugs or anticancer molecules to GBM cells. The major challenge in improving GBM treatment implicates the development of a targeted drug delivery system, capable of crossing the blood–brain barrier (BBB) and specifically targeting GBM cells. Aptamers possess many characteristics that make them ideal novel therapeutic agents for the treatment of GBM. They are short single-stranded nucleic acids (RNA or ssDNA) able to bind to a molecular target with high affinity and specificity. Several GBM-targeting aptamers have been developed for imaging, tumor cell isolation from biopsies, and drug/anticancer molecule delivery to the tumor cells. Due to their properties (low immunogenicity, long stability, and toxicity), a large number of aptamers have been selected against GBM biomarkers and tested in GBM cell lines, while only a few of them have also been tested in in vivo models of GBM. Herein, we specifically focus on aptamers tested in GBM in vivo models that can be considered as new diagnostic and/or therapeutic tools for GBM patients’ treatment.

Expression and pharmacological inhibition of TrkB and EGFR in glioblastoma

A member of the Trk family of neurotrophin receptors, tropomyosin receptor kinase B (TrkB, encoded by the NTRK2 gene) is an increasingly important target in various cancer types, including glioblastoma (GBM). EGFR is among the most frequently altered oncogenes in GBM, and EGFR inhibition has been tested as an experimental therapy. Functional interactions between EGFR and TrkB have been demonstrated. In the present study, we investigated the role of TrkB and EGFR, and their interactions, in GBM. Analyses of NTRK2 and EGFR gene expression from The Cancer Genome Atlas (TCGA) datasets showed an increase in NTRK2 expression in the proneural subtype of GBM, and a strong correlation between NTRK2 and EGFR expression in glioma CpG island methylator phenotype (G-CIMP+) samples. We showed that when TrkB and EGFR inhibitors were combined, the inhibitory effect on A172 human GBM cells was more pronounced than when either inhibitor was given alone. When U87MG GBM cells were xenografted into the flank of nude mice, tumor growth was delayed by treatment with TrkB and EGFR inhibitors, given alone or combined, only at specific time points. Intracranial GBM growth in mice was not significantly affected by drug treatments. Our findings indicate that correlations between NTRK2 and EGFR expression occur in specific GBM subgroups. Also, our results using cultured cells suggest for the first time the potential of combining TrkB and EGFR inhibition for the treatment of GBM.

Autophagy as a Potential Therapy for Malignant Glioma

Glioma is the most frequent and aggressive type of brain neoplasm, being anaplastic astrocytoma (AA) and glioblastoma multiforme (GBM), its most malignant forms. The survival rate in patients with these neoplasms is 15 months after diagnosis, despite a diversity of treatments, including surgery, radiation, chemotherapy, and immunotherapy. The resistance of GBM to various therapies is due to a highly mutated genome; these genetic changes induce a de-regulation of several signaling pathways and result in higher cell proliferation rates, angiogenesis, invasion, and a marked resistance to apoptosis; this latter trait is a hallmark of highly invasive tumor cells, such as glioma cells. Due to a defective apoptosis in gliomas, induced autophagic death can be an alternative to remove tumor cells. Paradoxically, however, autophagy in cancer can promote either a cell death or survival. Modulating the autophagic pathway as a death mechanism for cancer cells has prompted the use of both inhibitors and autophagy inducers. The autophagic process, either as a cancer suppressing or inducing mechanism in high-grade gliomas is discussed in this review, along with therapeutic approaches to inhibit or induce autophagy in pre-clinical and clinical studies, aiming to increase the efficiency of conventional treatments to remove glioma neoplastic cells.

Autophagy in cancers including brain tumors: role of MicroRNAs

Autophagy has a crucial role in many cancers, including brain tumors. Several types of endogenous molecules (e.g. microRNAs, AKT, PTEN, p53, EGFR, and NF1) can modulate the process of autophagy. Recently miRNAs (small non-coding RNAs) have been found to play a vital role in the regulation of different cellular and molecular processes, such as autophagy. Deregulation of these molecules is associated with the development and progression of different pathological conditions, including brain tumors. It was found that miRNAs are epigenetic regulators, which influence the level of proteins coded by the targeted mRNAs with any modification of the genetic sequences. It has been revealed that various miRNAs (e.g., miR-7-1-3p, miR-340, miR-17, miR-30a, miR-224-3p, and miR-93), as epigenetic regulators, can modulate autophagy pathways within brain tumors. A deeper understanding of the underlying molecular targets of miRNAs, and their function in autophagy pathways could contribute to the development of new treatment methods for patients with brain tumors. In this review, we summarize the various miRNAs, which are involved in regulating autophagy in brain tumors. Moreover, we highlight the role of miRNAs in autophagy-related pathways in different cancers.

ErbB4 promotes malignant peripheral nerve sheath tumor pathogenesis via Ras-independent mechanisms

BACKGROUND

We have found that erbB receptor tyrosine kinases drive Ras hyperactivation and growth in NF1-null malignant peripheral nerve sheath tumors (MPNSTs). However, MPNSTs variably express multiple erbB receptors with distinct functional characteristics and it is not clear which of these receptors drive MPNST pathogenesis. Here, we test the hypothesis that altered erbB4 expression promotes MPNST pathogenesis by uniquely activating key cytoplasmic signaling cascades.

METHODS

ErbB4 expression was assessed using immunohistochemistry, immunocytochemistry, immunoblotting and real-time PCR. To define erbB4 functions, we generated mice that develop MPNSTs with floxed Erbb4 alleles (P0-GGFβ3;Trp53+/-;Erbb4flox/flox mice) and ablated Erbb4 in these tumors. MPNST cell proliferation and survival was assessed using 3H-thymidine incorporation, MTT assays, Real-Time Glo and cell count assays. Control and Erbb4-null MPNST cells were orthotopically xenografted in immunodeficient mice and the growth, proliferation (Ki67 labeling), apoptosis (TUNEL labeling) and angiogenesis of these grafts was analyzed. Antibody arrays querying cytoplasmic kinases were used to identify erbB4-responsive kinases. Pharmacologic or genetic inhibition was used to identify erbB4-responsive kinases that drive proliferation.

RESULTS

Aberrant erbB4 expression was evident in 25/30 surgically resected human MPNSTs and in MPNSTs from genetically engineered mouse models (P0-GGFβ3 and P0-GGFβ3;Trp53+/- mice); multiple erbB4 splice variants that differ in their ability to activate PI3 kinase and nuclear signaling were present in MPNST-derived cell lines. Erbb4-null MPNST cells demonstrated decreased proliferation and survival and altered morphology relative to non-ablated controls. Orthotopic allografts of Erbb4-null cells were significantly smaller than controls, with reduced proliferation, survival and vascularization. ERBB4 knockdown in human MPNST cells similarly inhibited DNA synthesis and viability. Although we have previously shown that broad-spectrum erbB inhibitors inhibit Ras activation, Erbb4 ablation did not affect Ras activation, suggesting that erbB4 drives neoplasia via non-Ras dependent pathways. An analysis of 43 candidate kinases identified multiple NRG1β-responsive and erbB4-dependent signaling cascades including the PI3K, WNK1, STAT3, STAT5 and phospholipase-Cγ pathways. Although WNK1 inhibition did not alter proliferation, inhibition of STAT3, STAT5 and phospholipase-Cγ markedly reduced proliferation.

CONCLUSIONS

ErbB4 promotes MPNST growth by activating key non-Ras dependent signaling cascades including the STAT3, STAT5 and phospholipase-Cγ pathways. ErbB4 and its effector pathways are thus potentially useful therapeutic targets in MPNSTs.

The tumor suppressor FOXO3a mediates the response to EGFR inhibition in glioblastoma cells

PURPOSE

Although EGFR activation is a hallmark of glioblastoma (GBM), anti-EGFR therapy has so far not yielded the desired effects. Targeting PI3K/Akt has been proposed as a strategy to increase the cellular sensitivity to EGFR inhibitors. Here we evaluated the contribution of FOXO3a, a key Akt target, in the response of GBM cells to EGFR inhibition.

METHODS

FOXO3a activation was assessed by immunofluorescence and gene reporter assays, and by evaluating target gene expression using Western blotting and qRT-PCR. Cellular effects were evaluated using cell viability and apoptosis assays, i.e., Annexin V/PI staining and caspase 3/7 activity measurements. Drug synergism was evaluated by performing isobolographic analyses. Gene silencing experiments were performed using stable shRNA transfections.

RESULTS

We found that EGFR inhibition in GBM cells led to FOXO3a activation and to transcriptional modulation of its key targets, including repression of the oncogene FOXM1. In addition, we found that specific FOXO3a activation recapitulated the molecular effects of EGFR inhibition, and that the FOXO3a activator trifluoperazine, a FDA-approved antipsychotic agent, reduced GBM cell growth. Subsequent isobolographic analyses of combination experiments indicated that trifluoperazine and erlotinib cooperated synergistically and that their concomitant treatment induced a robust activation of FOXO3a, leading to apoptosis in GBM cells. Using gene silencing, we found that FOXO3a is essential for the response of GBM cells to EGFR inhibition.

CONCLUSIONS

Our data indicate that FOXO3a activation is a crucial event in the response of GBM cells to EGFR inhibition, suggesting that FOXO3a may serve as an actionable therapeutic target that can be modulated using FDA-approved drugs.

Combined Inhibition of HDAC and EGFR Reduces Viability and Proliferation and Enhances STAT3 mRNA Expression in Glioblastoma Cells

Changes in expression of histone deacetylases (HDACs), which epigenetically regulate chromatin structure, and mutations and amplifications of the EGFR gene, which codes for the epidermal growth factor receptor (EGFR), have been reported in glioblastoma (GBM), the most common and malignant type of brain tumor. There are likely interplays between HDACs and EGFR in promoting GBM progression, and HDAC inhibition can cooperate with EGFR blockade in reducing the growth of lung cancer cells. Here, we found that either HDAC or EGFR inhibitors dose-dependently reduced the viability of U87 and A-172 human GBM cells. In U87 cells, the combined inhibition of HDACs and EGFR was more effective than inhibiting either target alone in reducing viability and long-term proliferation. In addition, HDAC or EGFR inhibition, alone or combined, led to G0/G1 cell cycle arrest. The EGFR inhibitor alone or combined with HDAC inhibition increased mRNA expression of the signal transducer and activator of transcription 3 (STAT3), which can act either as an oncogene or a tumor suppressor in GBM. These data provide early evidence that combining HDAC and EGFR inhibition may be an effective strategy to reduce GBM growth, through a mechanism possibly involving STAT3.

Epidermal Growth Factor Receptor Cell Proliferation Signaling Pathways

The epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase that is commonly upregulated in cancers such as in non-small-cell lung cancer, metastatic colorectal cancer, glioblastoma, head and neck cancer, pancreatic cancer, and breast cancer. Various mechanisms mediate the upregulation of EGFR activity, including common mutations and truncations to its extracellular domain, such as in the EGFRvIII truncations, as well as to its kinase domain, such as the L858R and T790M mutations, or the exon 19 truncation. These EGFR aberrations over-activate downstream pro-oncogenic signaling pathways, including the RAS-RAF-MEK-ERK MAPK and AKT-PI3K-mTOR pathways. These pathways then activate many biological outputs that are beneficial to cancer cell proliferation, including their chronic initiation and progression through the cell cycle. Here, we review the molecular mechanisms that regulate EGFR signal transduction, including the EGFR structure and its mutations, ligand binding and EGFR dimerization, as well as the signaling pathways that lead to G1 cell cycle progression. We focus on the induction of CYCLIN D expression, CDK4/6 activation, and the repression of cyclin-dependent kinase inhibitor proteins (CDKi) by EGFR signaling pathways. We also discuss the successes and challenges of EGFR-targeted therapies, and the potential for their use in combination with CDK4/6 inhibitors.

Epidermal Growth Factor Receptor Cell Proliferation Signaling Pathways

The epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase that is commonly upregulated in cancers such as in non-small-cell lung cancer, metastatic colorectal cancer, glioblastoma, head and neck cancer, pancreatic cancer, and breast cancer. Various mechanisms mediate the upregulation of EGFR activity, including common mutations and truncations to its extracellular domain, such as in the EGFRvIII truncations, as well as to its kinase domain, such as the L858R and T790M mutations, or the exon 19 truncation. These EGFR aberrations over-activate downstream pro-oncogenic signaling pathways, including the RAS-RAF-MEK-ERK MAPK and AKT-PI3K-mTOR pathways. These pathways then activate many biological outputs that are beneficial to cancer cell proliferation, including their chronic initiation and progression through the cell cycle. Here, we review the molecular mechanisms that regulate EGFR signal transduction, including the EGFR structure and its mutations, ligand binding and EGFR dimerization, as well as the signaling pathways that lead to G1 cell cycle progression. We focus on the induction of CYCLIN D expression, CDK4/6 activation, and the repression of cyclin-dependent kinase inhibitor proteins (CDKi) by EGFR signaling pathways. We also discuss the successes and challenges of EGFR-targeted therapies, and the potential for their use in combination with CDK4/6 inhibitors.

Epidermal growth factor receptor variant III in head and neck squamous cell carcinoma is not relevant for targeted therapy and irradiation

BACKGROUND

The epidermal growth factor receptor (EGFR) is an important regulator of cell growth and survival, and is highly variable in tumor cells. The most prevalent variation of the EGFR extracellular domain is the EGFR variant III (EGFRvIII). Some studies imply that EGFRvIII may be responsible for the poor response to the monoclonal EGFR-antibody Cetuximab, used therapeutically in head and neck squamous cell carcinoma (HNSCC). Due to inconsistent data in the literature regarding EGFRvIII prevalence and clinical relevance in HNSCC, especially its predictive value, we examined EGFRvIII-transfected cell lines and patient tissue samples.

RESULTS

In contrast to other recent publications, we were able to demonstrate EGFRvIII expression in HNSCC. However, we noted that the different detection methods yielded inconsistent results. Furthermore, our EGFRvIII transfected and EGFR wild type cell lines exhibited similar characteristics and response rates in the performed in vitro experiments.

MATERIALS AND METHODS

We conducted various inhibition and combined irradiation experiments using three EGFRvIII-transfected cell lines. Moreover, a patient cohort of 149 cases consisting of formalin fixed and paraffin embedded (FFPE) and fresh-frozen specimens was assayed via reverse transcriptase PCR (rtPCR) with gel electrophoresis and sequencing for EGFRvIII prevalence. In the rtPCR assays, we used five previously published EGFRvIII primers and EGFRvIII-positive glioblastoma tissue as a positive control. In addition, immunohistochemical staining was conducted.

CONCLUSIONS

EGFRvIII can be detected in HNSCC patient samples. Nevertheless, the low prevalence and similar response rates to targeted drugs and irradiation in vitro cast doubt regarding the clinical relevance of EGFRvIII in HNSCC.

Human Cytomegalovirus Requires Epidermal Growth Factor Receptor Signaling To Enter and Initiate the Early Steps in the Establishment of Latency in CD34+ Human Progenitor Cells

The establishment of human cytomegalovirus (HCMV) latency and persistence relies on the successful infection of hematopoietic cells, which serve as sites of viral persistence and contribute to viral spread. Here, using blocking antibodies and pharmacological inhibitors, we document that HCMV activation of the epidermal growth factor receptor (EGFR) and downstream phosphatidylinositol 3-kinase (PI3K) mediates viral entry into CD34+ human progenitor cells (HPCs), resulting in distinct cellular trafficking and nuclear translocation of the virus compared to that in other immune cells, such as we have documented in monocytes. We argue that the EGFR allows HCMV to regulate the cellular functions of these replication-restricted cells via its signaling activity following viral binding. In addition to regulating HCMV entry/trafficking, EGFR signaling may also shape the early steps required for the successful establishment of viral latency in CD34+ cells, as pharmacological inhibition of EGFR increases the transcription of lytic IE1/IE2 mRNA while curbing the expression of latency-associated UL138 mRNA. EGFR signaling following infection of CD34+ HPCs may also contribute to changes in hematopoietic potential, as treatment with the EGFR kinase (EGFRK) inhibitor AG1478 alters the expression of the cellular hematopoietic cytokine interleukin 12 (IL-12) in HCMV-infected cells but not in mock-infected cells. These findings, along with our previous work with monocytes, suggest that EGFR likely serves as an important determinant of HCMV tropism for select subsets of hematopoietic cells. Moreover, our new data suggest that EGFR is a key receptor for efficient viral entry and that the ensuing signaling regulates important early events required for successful infection of CD34+ HPCs by HCMV.IMPORTANCE HCMV establishes lifelong persistence within the majority of the human population without causing overt pathogenesis in healthy individuals. Despite this, reactivation of HCMV from its latent reservoir in the bone marrow causes significant morbidity and mortality in immunologically compromised individuals, such as bone marrow and solid organ transplant patients. Lifelong persistent infection has also been linked with the development of various cardiovascular diseases in otherwise healthy individuals. Current HCMV therapeutics target lytic replication, but not the latent viral reservoir; thus, an understanding of the molecular basis for viral latency and persistence is paramount to controlling or eliminating HCMV infection. Here, we show that the viral signalosome activated by HCMV binding to its entry receptor, EGFR, in CD34+ HPCs initiates early events necessary for successful latent infection of this cell type. EGFR and associated signaling players may therefore represent promising targets for mitigating HCMV persistence.

Epidermal Growth Factor Receptor Silencing Blunts the Slow Force Response to Myocardial Stretch

Background

Myocardial stretch increases force biphasically: the Frank‐Starling mechanism followed by the slow force response (SFR). Based on pharmacological strategies, we proposed that epidermal growth factor (EGF) receptor (EGFR or ErbB1) activation is crucial for SFR development. Pharmacological inhibitors could block ErbB4, a member of the ErbB family present in the adult heart. We aimed to specifically test the role of EGFR activation after stretch, with an interference RNA incorporated into a lentiviral vector (small hairpin RNA [shRNA]‐EGFR).

Methods and Results

Silencing capability of p‐shEGFR was assessed in EGFR‐GFP transiently transfected HEK293T cells. Four weeks after lentivirus injection into the left ventricular wall of Wistar rats, shRNA‐EGFR–injected hearts showed ≈60% reduction of EGFR protein expression compared with shRNA‐SCR–injected hearts. ErbB2 and ErbB4 expression did not change. The SFR to stretch evaluated in isolated papillary muscles was ≈130% of initial rapid phase in the shRNA‐SCR group, while it was blunted in shRNA‐EGFR–expressing muscles. Angiotensin II (Ang II)‐dependent Na+/H+ exchanger 1 activation was indirectly evaluated by intracellular pH measurements in bicarbonate‐free medium, demonstrating an increase in shRNA‐SCR–injected myocardium, an effect not observed in the silenced group. Ang II‐ or EGF‐triggered reactive oxygen species production was significantly reduced in shRNA‐EGFR–injected hearts compared with that in the shRNA‐SCR group. Chronic lentivirus treatment affected neither the myocardial basal redox state (thiobarbituric acid reactive substances) nor NADPH oxidase activity or expression. Finally, Ang II or EGF triggered a redox‐sensitive pathway, leading to p90RSK activation in shRNA‐SCR‐injected myocardium, an effect that was absent in the shRNA‐EGFR group.

Conclusions

Our results provide evidence that specific EGFR activation after myocardial stretch is a key factor in promoting the redox‐sensitive kinase activation pathway, leading to SFR development.

FOXA2 mRNA expression is associated with relapse in patients with Triple-Negative/Basal-like breast carcinoma

The FOXA family of transcription factors regulates chromatin structure and gene expression especially during embryonic development. In normal breast tissue FOXA1 acts throughout mammary development; whereas in breast carcinoma its expression promotes luminal phenotype and correlates with good prognosis. However, the role of FOXA2 has not been previously studied in breast cancer. Our purpose was to analyze the expression of FOXA2 in breast cancer cells, to explore its role in breast cancer stem cells, and to correlate its mRNA expression with clinicopathological features and outcome in a series of patients diagnosed with breast carcinoma. We analyzed FOXA2 mRNA expression in a retrospective cohort of 230 breast cancer patients and in cell lines. We also knocked down FOXA2 mRNA expression by siRNA to determine the impact on cell proliferation and mammospheres formation using a cancer stem cells culture assay. In vitro studies demonstrated higher FOXA2 mRNA expression in Triple-Negative/Basal-like cells. Further, when it was knocked down, cells decreased proliferation and its capability of forming mammospheres. Similarly, FOXA2 mRNA expression was detected in 10% (23/230) of the tumors, especially in Triple-Negative/Basal-like phenotype (p < 0.001, Fisher's test). Patients whose tumors expressed FOXA2 had increased relapses (59 vs. 79%, p = 0.024, log-rank test) that revealed an independent prognostic value (HR = 3.29, C.I.95% = 1.45-7.45, p = 0.004, Cox regression). Our results suggest that FOXA2 promotes cell proliferation, maintains cancer stem cells, favors the development of Triple-Negative/Basal-like tumors, and is associated with increase relapses.

HGUE-C-1 is an atypical and novel colon carcinoma cell line

Background

Colorectal carcinoma is a common cause of cancer. Adjuvant treatments include: 5-fluorouracil administered together with folinic acid, or more recently, oral fluoropyrimidines such as capecitabine, in combination with oxaliplatin or irinotecan. Metastatic colorectal cancer patients can benefit from other additional treatments such as cetuximab or bevacizumab.

Methods

Using cell culture techniques, we isolated clonal populations from primary cultures of ascitic effusion derived from a colon cancer patient and after several passages an established cell line, HGUE-C-1, was obtained. Genetic analysis of HGUE-C-1 cells was performed by PCR of selected exons and sequencing. Cell proliferation studies were performed by MTT assays and cell cycle analyses were performed by flow cytometry. Retinoblastoma activity was measured by luciferase assays and proteins levels and activity were analysed by Western blot or immunohistochemistry.

Results

We have established a new cell line from ascitic efussion of a colon cancer patient who did not respond to 5-fluorouracil or irinotecan. HGUE-C-1 cells did not show microsatellite instability and did not harbour mutations in KRAS, BRAF, PI3KCA or TP53. However, these cells showed loss of heterozygosity affecting Adenomatous Polyposis Coli and nuclear staining of β-catenin protein. The HGUE-C-1 cell line was sensitive to erlotinib, gefitinib, NVP-BEZ235, rapamycin and trichostatin, among other drugs, but partially resistant to heat shock protein inhibitors and highly resistant to AZD-6244 and oxaliplatin, even though the patient from which this cell line was derived had not been exposed to these drugs. Molecular characterization of this cell line revealed low expression levels and activity of Retinoblastoma protein and elevated basal levels of Erk1/2 activity and p70S6K expression and activity, which may be related to chemoresistance mechanisms.

Conclusions

HGUE-C-1 represents a novel and peculiar colon carcinoma model to study chemoresistance to chemotherapeutic agents and to novel anti-neoplasic drugs that interrupt signalling pathways such as the APC/βcatenin, Ras/Raf/Mek/Erk, PI3K/mTOR/p70S6K pathways as well as histone regulation mechanisms.

Role of receptor tyrosine kinases and their ligands in glioblastoma

Glioblastoma multiforme is the most frequent, aggressive and fatal type of brain tumor. Glioblastomas are characterized by their infiltrating nature, high proliferation rate and resistance to chemotherapy and radiation. Recently, oncologic therapy experienced a rapid evolution towards “targeted therapy,” which is the employment of drugs directed against particular targets that play essential roles in proliferation, survival and invasiveness of cancer cells. A number of molecules involved in signal transduction pathways are used as molecular targets for the treatment of various tumors. In fact, inhibitors of these molecules have already entered the clinic or are undergoing clinical trials. Cellular receptors are clear examples of such targets and in the case of glioblastoma multiforme, some of these receptors and their ligands have become relevant. In this review, the importance of glioblastoma multiforme in signaling pathways initiated by extracellular tyrosine kinase receptors such as EGFR, PDGFR and IGF-1R will be discussed. We will describe their ligands, family members, structure, activation mechanism, downstream molecules, as well as the interaction among these pathways. Lastly, we will provide an up-to-date review of the current targeted therapies in cancer, in particular glioblastoma that employ inhibitors of these pathways and their benefits.

Synergistic cell growth inhibition by the combination of amrubicin and Akt-suppressing agents in K-ras mutation-harboring lung adenocarcinoma cells: implication of EGFR tyrosine kinase inhibitors

Previously we showed that Akt-suppressing agents, combined with amrubicin, synergistically inhibited the growth of small cell lung cancer cells. The combined effects of chemotherapeutic agents and Akt-suppressing agents, including epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors, were evaluated in A549 lung adenocarcinoma cells harboring K-ras mutation and wild-type EGFR. Only amrubicin and not other chemotherapeutics (cisplatin, pemetrexed and paclitaxel) synergistically inhibited cell growth when combined with an Akt inhibitor, LY294002. The combination of amrubicin and LY294002 enhanced Annexin V binding to cells. A non-specific tyrosine kinase inhibitor, genistein, suppressed Akt and showed synergistic interaction in combination with amrubicin. Two EGFR tyrosine kinase inhibitors (EGFR-TKIs), gefitinib and erlotinib, suppressed Akt activity at clinically achievable concentrations and demonstrated synergism when combined with amrubicin. The suppression of K-ras expression by siRNA interfered with this synergism and inhibited both EGFR and Akt activity in A549 cells. In Ma10 cells, which harbor wild-type EGFR and K-ras, EGFR-TKIs neither suppressed Akt activity nor exhibited such synergism when combined with amrubicin. We concluded that the synergism by the combination of EGFR-TKI and amrubicin is attributable, at least partially, to K-ras mutation in A549 cells. The combination of EGFR-TKI and amrubicin may be a promising treatment for lung cancer with wild-type EGFR and K-ras mutation.

Inhibition of receptor signaling and of glioblastoma-derived tumor growth by a novel PDGFRβ aptamer

Platelet-derived growth factor receptor β (PDGFRβ) is a cell-surface tyrosine kinase receptor implicated in several cellular processes including proliferation, migration, and angiogenesis. It represents a compelling therapeutic target in many human tumors, including glioma. A number of tyrosine kinase inhibitors under development as antitumor agents have been found to inhibit PDGFRβ. However, they are not selective as they present multiple tyrosine kinase targets. Here, we report a novel PDGFRβ-specific antagonist represented by a nuclease-resistant RNA-aptamer, named Gint4.T. This aptamer is able to specifically bind to the human PDGFRβ ectodomain (Kd: 9.6 nmol/l) causing a strong inhibition of ligand-dependent receptor activation and of downstream signaling in cell lines and primary cultures of human glioblastoma cells. Moreover, Gint4.T aptamer drastically inhibits cell migration and proliferation, induces differentiation, and blocks tumor growth in vivo. In addition, Gint4.T aptamer prevents PDGFRβ heterodimerization with and resultant transactivation of epidermal growth factor receptor. As a result, the combination of Gint4.T and an epidermal growth factor receptor-targeted aptamer is better at slowing tumor growth than either single aptamer alone. These findings reveal Gint4.T as a PDGFRβ-drug candidate with translational potential.

Developmental defects in zebrafish for classification of EGF pathway inhibitors

One of the major challenges when testing drug candidates targeted at a specific pathway in whole animals is the discrimination between specific effects and unwanted, off-target effects. Here we used the zebrafish to define several developmental defects caused by impairment of Egf signaling, a major pathway of interest in tumor biology. We inactivated Egf signaling by genetically blocking Egf expression or using specific inhibitors of the Egf receptor function. We show that the combined occurrence of defects in cartilage formation, disturbance of blood flow in the trunk and a decrease of myelin basic protein expression represent good indicators for impairment of Egf signaling. Finally, we present a classification of known tyrosine kinase inhibitors according to their specificity for the Egf pathway. In conclusion, we show that developmental indicators can help to discriminate between specific effects on the target pathway from off-target effects in molecularly targeted drug screening experiments in whole animal systems.

Domain 2 of uPAR regulates single-chain urokinase-mediated angiogenesis through β1-integrin and VEGFR2

How single-chain urokinase (ScuPA) mediates angiogenesis is incompletely understood. ScuPA (≥4 nM) induces phosphorylated (p)ERK1/2 (MAPK44 and MAPK42) and pAkt (Ser(473)) in umbilical vein and dermal microvascular endothelial cells. Activation of pERK1/2 by ScuPA is blocked by PD-98059 or U-0126, and pAkt (Ser(473)) activation is inhibited by wortmannin or LY-294002. ScuPA (32 nM) or protease-inhibited two-chain urokinase stimulates pERK1/2 to the same extent, indicating that signaling is not dependent on enzymatic activity. ScuPA induces pERK1/2, but not pAkt (Ser(473)), in SIN1(-/-) cells, indicating that the two pathways are not identical. Peptides from domain 2 of the urokinase plasminogen activator receptor (uPAR) or domain 5 of high-molecular-weight kininogen compete with ScuPA for the induction of pERK1/2 and pAkt (Ser(473)). A peptide of the integrin-binding site on uPAR, a β1-integrin peptide that binds uPAR, antibody 6S6 to β1-integrin, tyrosine kinase inhibitors AG-1478 or PP3, and small interfering RNA knockdown of VEFG receptor 2, but not HER1-HER4, blocked ScuPA-induced pERK1/2 and pAkt (Ser(473)). ScuPA-induced endothelial cell proliferation was blocked by inhibitors of pERK1/2 and pAkt (Ser(473)), antibody 6S6, and uPAR or kininogen peptides. ScuPA initiated aortic sprouts and Matrigel plug angiogenesis in normal, but not uPAR-deficient, mouse aortae or mice, respectively, but these were blocked by PD-98059, LY-294002, AG-1478, or cleaved high-molecular-weight kininogen. In summary, this investigation indicates a novel, a nonproteolytic signaling pathway initiated by zymogen ScuPA and mediated by domain 2 of uPAR, β1-integrins, and VEGF receptor 2 leading to angiogenesis. Kininogens or peptides from it downregulate this pathway.

Identification of a novel antagonist of the ErbB1 receptor capable of inhibiting migration of human glioblastoma cells

BACKGROUND

Receptors of the ErbB family are involved in the development of various cancers, and the inhibition of these receptors represents an attractive therapeutic concept. Upon ligand binding, ErbB receptors become activated as homo- or heterodimers, leading to the activation of downstream signaling cascades that result in the facilitation of cell proliferation and migration. A region of the extracellular part of the receptor, termed the 'dimerization arm', is important for the formation of receptor dimers and represents an attractive target for the design of ErbB inhibitors.

METHODS

An ErbB1 targeting peptide, termed Herfin-1, was designed based on a model of the tertiary structure of the EGF-EGFR ternary complex. The binding kinetics of this peptide were determined employing surface plasmon resonance analyses. ErbB1-4 expression and phosphorylation in human glioblastoma cell lines U87 and U118 were determined by Western blotting using specific antibodies. Cell proliferation was determined by MTS staining. Cell migration was examined using a Chemotaxis Migration Kit. Neurite outgrowth from primary cerebellar granule neurons was evaluated by fluorescence microscopy and image processing.

RESULTS

The present study shows that Herfin-1 functions as an ErbB1 antagonist. It binds to the extracellular domain of ErbB1 with a KD value of 361 nM. In U87 and U118 cells, both expressing high levels of ErbB1, Herfin-1 inhibits EGF-induced ErbB1 phosphorylation and cell migration. Additionally, Herfin-1 was found to increase neurite outgrowth in cerebellar granule neurons, likely through the inhibition of a sustained weak ErbB1 activation.

CONCLUSIONS

Targeting the ErbB1 receptor dimerization interface is a promising strategy to inhibit receptor activation in ErbB1-expressing glioma cells.

Collections of simultaneously altered genes as biomarkers of cancer cell drug response

Computational analysis of cancer pharmacogenomics data has resulted in biomarkers predictive of drug response, but the majority of response is not captured by current methods. Methods typically select single biomarkers or groups of related biomarkers but do not account for response that is strictly dependent on many simultaneous genetic alterations. This shortcoming reflects the combinatorics and multiple-testing problem associated with many-body biologic interactions. We developed a novel approach, Multivariate Organization of Combinatorial Alterations (MOCA), to partially address these challenges. Extending on previous work that accounts for pairwise interactions, the approach rapidly combines many genomic alterations into biomarkers of drug response, using Boolean set operations coupled with optimization; in this framework, the union, intersection, and difference Boolean set operations are proxies of molecular redundancy, synergy, and resistance, respectively. The algorithm is fast, broadly applicable to cancer genomics data, is of immediate use for prioritizing cancer pharmacogenomics experiments, and recovers known clinical findings without bias. Furthermore, the results presented here connect many important, previously isolated observations.

Therapeutic stem cells expressing variants of EGFR-specific nanobodies have antitumor effects

The deregulation of the epidermal growth factor receptor (EGFR) has a significant role in the progression of tumors. Despite the development of a number of EGFR-targeting agents that can arrest tumor growth, their success in the clinic is limited in several tumor types, particularly in the highly malignant glioblastoma multiforme (GBM). In this study, we generated and characterized EGFR-specific nanobodies (ENb) and imageable and proapoptotic ENb immunoconjugates released from stem cells (SC) to ultimately develop a unique EGFR-targeted therapy for GBM. We show that ENbs released from SCs specifically localize to tumors, inhibit EGFR signaling resulting in reduced GBM growth and invasiveness in vitro and in vivo in both established and primary GBM cell lines. We also show that ENb primes GBM cells for proapoptotic tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis. Furthermore, SC-delivered immunoconjugates of ENb and TRAIL target a wide spectrum of GBM cell types with varying degrees of TRAIL resistance and significantly reduce GBM growth and invasion in both established and primary invasive GBM in mice. This study demonstrates the efficacy of SC-based EGFR targeted therapy in GBMs and provides a unique approach with clinical implications.

Effect of rosemary polyphenols on human colon cancer cells: transcriptomic profiling and functional enrichment analysis

In this work, the effect of rosemary extracts rich on polyphenols obtained using pressurized fluids was investigated on the gene expression of human SW480 and HT29 colon cancer cells. The application of transcriptomic profiling and functional enrichment analysis was done via two computational approaches, Ingenuity Pathway Analysis and Gene Set Enrichment Analysis. These two approaches were used for functional enrichment analysis as a previous step for a reliable interpretation of the data obtained from microarray analysis. Reverse transcription quantitative-PCR was used to confirm relative changes in mRNA levels of selected genes from microarrays. The selection of genes was based on their expression change, adjusted p value, and known biological function. According to genome-wide transcriptomics analysis, rosemary polyphenols altered the expression of ~4 % of the genes covered by the Affymetrix Human Gene 1.0ST chip in both colon cancer cells. However, only ~18 % of the differentially expressed genes were common to both cell lines, indicating markedly different expression profiles in response to the treatment. Differences in induction of G2/M arrest observed by rosemary polyphenols in the two colon adenocarcinoma cell lines suggest that the extract may be differentially effective against tumors with specific mutational pattern. From our results, it is also concluded that rosemary polyphenols induced a low degree of apoptosis indicating that other multiple signaling pathways may contribute to colon cancer cell death.

EGFR inhibitor BIBU induces apoptosis and defective autophagy in glioma cells

The importance of aberrant EGFR signaling in glioblastoma progression and the promise of EGFR-specific therapies, prompted us to determine the efficacy of novel EGFR inhibitor BIBU-1361 [(3-chloro-4-fluoro-phenyl)-[6-(4-diethylaminomethyl-piperidin-1-yl)-pyrimido [5,4-d]pyrimidin-4-yl]-amine] in affecting glioma survival. BIBU induced apoptosis in a caspase-dependent manner and induced cell cycle arrest in glioma cells. Apoptosis was accompanied by decreased EGFR levels and its increased distribution towards caveolin rich lipid raft microdomains. BIBU inhibited pro-survival pathways Akt/mTOR and gp130/JAK/STAT3; and decreased levels of pro-inflammatory cytokine IL-6. BIBU caused increased LC3-I to LC3-II conversion and triggered the internalization of EGFR within vacuoles along with its increased co-localization with LC3-II. BIBU caused accumulation of p62 and increased levels of cleaved forms of Beclin-1 in all the cell lines tested. Importantly, BIBU failed to initiate execution of autophagy as pharmacological inhibition of autophagy with 3-Methyladenine or Bafilomycin failed to rescue BIBU mediated death. The ability of BIBU to abrogate Akt and STAT3 activation, induce apoptosis and prevent execution of autophagy warrants its investigation as a potent anti-glioma target.

EGFR inhibition in glioma cells modulates Rho signaling to inhibit cell motility and invasion and cooperates with temozolomide to reduce cell growth

Enforced EGFR activation upon gene amplification and/or mutation is a common hallmark of malignant glioma. Small molecule EGFR tyrosine kinase inhibitors, such as erlotinib (Tarceva), have shown some activity in a subset of glioma patients in recent trials, although the reported data on the cellular basis of glioma cell responsiveness to these compounds have been contradictory. Here we have used a panel of human glioma cell lines, including cells with amplified or mutant EGFR, to further characterize the cellular effects of EGFR inhibition with erlotinib. Dose-response and cellular growth assays indicate that erlotinib reduces cell proliferation in all tested cell lines without inducing cytotoxic effects. Flow cytometric analyses confirm that EGFR inhibition does not induce apoptosis in glioma cells, leading to cell cycle arrest in G₁. Interestingly, erlotinib also prevents spontaneous multicellular tumour spheroid growth in U87MG cells and cooperates with sub-optimal doses of temozolomide (TMZ) to reduce multicellular tumour spheroid growth. This cooperation appears to be schedule-dependent, since pre-treatment with erlotinib protects against TMZ-induced cytotoxicity whereas concomitant treatment results in a cooperative effect. Cell cycle arrest in erlotinib-treated cells is associated with an inhibition of ERK and Akt signaling, resulting in cyclin D1 downregulation, an increase in p27^kip1 levels and pRB hypophosphorylation. Interestingly, EGFR inhibition also perturbs Rho GTPase signaling and cellular morphology, leading to Rho/ROCK-dependent formation of actin stress fibres and the inhibition of glioma cell motility and invasion.

Characterization and response of newly developed high-grade glioma cultures to the tyrosine kinase inhibitors, erlotinib, gefitinib and imatinib

High-grade gliomas (HGG), are the most common aggressive brain tumours in adults. Inhibitors targeting growth factor signalling pathways in glioma have shown a low clinical response rate. To accurately evaluate response to targeted therapies further in vitro studies are necessary. Growth factor pathway expression using epidermal growth factor receptor (EGFR), mutant EGFR (EGFRvIII), platelet derived growth factor receptor (PDGFR), C-Kit and C-Abl together with phosphatase and tensin homolog (PTEN) expression and downstream activation of AKT and phosphorylated ribosomal protein S6 (P70S6K) was analysed in 26 primary glioma cultures treated with the tyrosine kinase inhibitors (TKIs) erlotinib, gefitinib and imatinib. Response to TKIs was assessed using 50% inhibitory concentrations (IC(50)). Response for each culture was compared with the EGFR/PDGFR immunocytochemical pathway profile using hierarchical cluster analysis (HCA) and principal component analysis (PCA). Erlotinib response was not strongly associated with high expression of the growth factor pathway components. PTEN expression did not correlate with response to any of the three TKIs. Increased EGFR expression was associated with gefitinib response; increased PDGFR-α expression was associated with imatinib response. The results of this in vitro study suggest gefitinib and imatinib may have therapeutic potential in HGG tumours with a corresponding growth factor receptor expression profile.

Histamine may induce airway remodeling through release of epidermal growth factor receptor ligands from bronchial epithelial cells

Asthma is a chronic inflammatory disease that is associated with airway remodeling, including hyperplasia of airway epithelial cells and airway smooth muscle cells, and goblet cell differentiation. We wished to address the potential role of histamine, a key biogenic amine involved in allergic reactions, in airway remodeling through the epidermal growth factor receptor (EGFR) pathway. Here, we demonstrate that histamine releases 2 EGFR ligands, amphiregulin and heparin-binding epidermal growth factor-like growth factor (HB-EGF), from airway epithelial cells. Amphiregulin and HB-EGF were expressed in airway epithelium of patients with asthma. Histamine up-regulated their mRNA expression (amphiregulin 3.2-fold, P<0.001; HB-EGF 2.3-fold, P<0.05) and triggered their release (amphiregulin EC(50) 0.50 μM, 31.2 ± 2.7 pg/ml with 10 μM histamine, P<0.01; HB-EGF EC(50) 0.54 μM, 78.5 ± 1.8 pg/ml with 10 μM histamine, P<0.001) compared to vehicle control (amphiregulin 19.3 ± 0.9 pg/ml; HB-EGF 60.2 ± 1.0 pg/ml), in airway epithelial cells. Histamine increased EGFR phosphorylation (2.1-fold by Western blot analysis) and induced goblet cell differentiation (CLCA1 up-regulation by real-time qPCR) in normal human bronchial epithelial (NHBE) cells. Moreover, amphiregulin and HB-EGF caused proliferation and migration of both NHBE cells and human airway smooth muscle cells. These results suggest that histamine may induce airway remodeling via the epithelial-derived EGFR ligands amphiregulin and HB-EGF.

Autophagy in brain tumors: a new target for therapeutic intervention

The role of autophagy, traditionally considered a cellular homeostatic and recycling mechanism, has expanded dramatically to include an involvement in discrete stages of tumor initiation and development. Gliomas are the most aggressive and also the most common brain malignancies. Current treatment modalities have only a modest effect on patient outcomes. Resistance to apoptosis, a hallmark of most cancers, has driven the search for novel targets in cancer therapy. The autophagy lysosomal pathway is one such target that is being explored in multiple cancers including gliomas and is a promising avenue for further therapeutic development. This review summarizes our current understanding of the autophagic process and its potential utility as a target for glioma therapy.

Bay846, a new irreversible small molecule inhibitor of EGFR and Her2, is highly effective against malignant brain tumor models

The epidermal growth factor receptor (EGFR) pathway is aberrantly activated in tumors and plays a key role in promoting tumor growth. Small molecule inhibitors which bind reversibly to EGFR have demonstrated limited clinical activity. Thus, there is a continued need to develop novel EGFR inhibitors with improved anti-tumor activity. Bay846 is a newly developed small molecule inhibitor that binds irreversibly to the tyrosine kinase domains of EGFR and Her2. The in vitro and in vivo efficacy of Bay846 was tested using a panel of nine human malignant brain tumor (glioma) models. Lapatinib, a reversible inhibitor of EGFR and Her2, was included for comparison. Six glioma cell lines were sensitive to Bay846 treatment. Bay846 strongly suppressed tumor cell growth in vitro by inducing cell lysis/death rather than cell cycle arrest. Consistent with this, Bay846 had potent anti-tumor activity which led to regressions in tumor size. The active, phosphorylated form of EGFR was reduced by Bay846 treatment in vitro and in tumors. Importantly, the efficacy of Bay846 was significantly greater than lapatinib in all assays. Bay846-sensitivity was associated with expression of a wild-type PTEN in conjunction with high levels of an oncogenic EGFR variant (A289V or EGFRvIII). These studies demonstrate that targeting the EGFR pathway with the irreversible inhibitor Bay846 has great potential to increase the efficacy of this cancer therapy.

Dual targeting of EGFR and focal adhesion kinase in 3D grown HNSCC cell cultures

PURPOSE

Epidermal growth factor receptor (EGFR) and focal adhesion kinase (FAK) show frequent overexpression and hyperactivity in various human malignancies including head and neck squamous cell carcinomas (HNSCC). To examine effects of dual EGFR/FAK inhibition on cellular radiosensitivity of HNSCC cells in a more physiological environment, we employed a previously established laminin-rich extracellular matrix (lrECM) based three-dimensional (3D) cell culture model.

MATERIALS AND METHODS

UTSCC15 and SAS HNSCC cell lines stably transfected with EGFR-CFP or CFP were used. Single or combined EGFR (Cetuximab, siRNA) and FAK (TAE226, siRNA) inhibition were accomplished prior to measuring clonogenic survival and protein expression and phosphorylation. Immunofluorescence enabled visualization of EGFR-CFP and FAK.

RESULTS

Cetuximab resulted in higher radiosensitization in EGFR-CFP overexpressing cell lines than CFP controls. Single EGFR or FAK inhibition mediated radiosensitization, while dual EGFR/FAK targeting further augmented this effect. Despite signaling alterations upon Cetuximab and siRNA knockdown, analysis of protein expression and phosphorylation indicates EGFR and FAK signaling coexistence without obvious overlap.

CONCLUSIONS

Combined EGFR/FAK targeting yielded stronger radiosensitization than either approach alone, which might be based on non-overlapping downstream signaling. Whether dual targeting of EGFR and FAK can reasonably be combined with radiotherapy and chemotherapy needs clarification.