Inhibition of apoptosis by amphiregulin via an insulin-like growth factor-1 receptor-dependent pathway in non-small cell lung cancer cell lines

Vasopressin and cardiovascular autonomic adjustment in chronic hypertensive pregnancy

Chronic hypertensive pregnancy (CHP) is a growing health issue with unknown etiology. Vasopressin (VP), a nonapeptide synthesized in paraventricular (PVN) and supraoptic nucleus (SON), is a well-known neuroendocrine and autonomic modulator of the cardiovascular system, related to hypertension development. We quantified gene expression of VP and its receptors, V1aR and V1bR, within the PVN and SON in CHP and normal pregnancy, and assessed levels of secreted plasma VP. Also, we evaluated autonomic cardiovascular adaptations to CHP using spectral indices of blood pressure (BPV) and heart rate (HRV) short-term variability, and spontaneous baroreflex sensitivity (BRS). Experiments were performed in female spontaneously hypertensive rats (SHRs) and in normotensive Wistar rats (WRs). Animals were equipped with a radiotelemetry probe for continuous hemodynamic recordings before and during pregnancy. BPV, HRV and BRS were assessed using spectral analysis and the sequence method, respectively. Plasma VP was determined by ELISA whilst VP, V1aR, and V1bR gene expression was analyzed by real-time-quantitative PCR (RT-qPCR). The results show that non-pregnant SHRs exhibit greater VP, V1aR, and V1bR gene expression in both PVN and SON respectively, compared to Wistar dams. Pregnancy decreased VP gene expression in the SON of SHRs but increased it in the PVN and SON of WRs. Pregnant SHRs exhibited a marked drop in plasma VP concentration associated with BP normalization. This triggered marked tachycardia, heart rate variability increase, and BRS increase in pregnant SHRs. It follows that regardless of BP normalization in late pregnancy, SHRs exhibit cardiovascular vulnerability and compensate by recruiting vagal mechanisms. Pregnant SHR dams have reduced expression of VP in SON associated with increased V1bR expression, lower plasma VP, normal BP during late pregnancy and marked signs of enhanced sympathetic cardiac stimulation (increased HR and LFHR variability) and recruitment of vagal mechanisms (enhancement of BRS and HFHR variability).

Amphiregulin regulates odontogenic differentiation of dental pulp stem cells by activation of mitogen-activated protein kinase and the phosphatidylinositol 3-kinase signaling pathways

Background

Human dental pulp stem cells (hDPSCs) have received widespread attention in the fields of tissue engineering and regenerative medicine. Although amphiregulin (AREG) has been shown to play a vital function in the biological processes of various cell types, its effects on DPSCs remain largely unknown. The aim of this study was to explore the specific role of AREG as a biologically active factor in the regeneration of dental pulp tissue.

Methods

The growth of hDPSCs, together with their proliferation and apoptosis, in response to AREG was examined by CCK-8 assay and flow cytometry. We explored the effects of AREG on osteo/odontogenic differentiation in vitro and investigated the regeneration and mineralization of hDPSCs in response to AREG in vivo. The effects of AREG gain- and loss-of-function on DPSC differentiation were investigated following transfection using overexpression plasmids and shRNA, respectively. The involvement of the mitogen-activated protein kinase (MAPK) or phosphatidylinositol 3-kinase (PI3K)/Akt pathways in the mineralization process and the expression of odontoblastic marker proteins after AREG induction were investigated by using Alizarin Red S staining and Western blotting, respectively.

Results

AREG (0.01–0.1 µg/mL) treatment of hDPSCs from 1 to 7 days increased hDPSCs growth and affected apoptosis minimally compared with negative controls. AREG exposure significantly promoted hDPSC differentiation, shown by increased mineralized nodule formation and the expression of odontoblastic marker protein expression. In vivo micro-CT imaging and quantitative analysis showed significantly greater formation of highly mineralized tissue in the 0.1 μg/mL AREG exposure group in DPSC/NF-gelatin-scaffold composites. AREG also promoted extracellular matrix production, with collagen fiber, mineralized matrix, and calcium salt deposition on the composites, as shown by H&E, Masson, and Von Kossa staining. Furthermore, AREG overexpression boosted hDPSC differentiation while AREG silencing inhibited it. During the differentiation of hDPSCs, AREG treatment led to phosphorylation of extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and PI3K/Akt. Notably, a specific inhibitor of ERK, JNK, and PI3K/Akt signaling markedly reduced AREG-induced differentiation, as well as levels of phosphorylated ERK and JNK in hDPSCs.

Conclusions

The data indicated that AREG promoted odontoblastic differentiation and facilitated regeneration and mineralization processes in hDPSCs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02971-4.

A Defect of Amphiregulin Release Predicted Longer Survival Independently of YAP Expression in Patients with Pleural Mesothelioma in the IFCT-0701 MAPS Phase 3 Trial

The Hippo pathway effector YAP is dysregulated in malignant pleural mesothelioma (MPM). YAP's target genes include the secreted growth factor amphiregulin (AREG), which is overexpressed in a wide range of epithelial cancers and plays an elusive role in MPM. We assayed the expression of YAP and AREG in MPM pathology samples and that of AREG additionally in plasma samples of patients from the randomized phase 3 IFCT‐0701 Mesothelioma Avastin Cisplatin Pemetrexed Study (MAPS) using immunohistochemistry and ELISA assays, respectively. MPM patients frequently presented high levels of tumor AREG (64.3%), a high cytosolic AREG expression being predictive of a better prognosis with longer median overall and progression‐free survival. Surprisingly, tumor AREG cytosolic expression was not correlated with secreted plasma AREG. By investigating the AREG metabolism and function in MPM cell lines H2452, H2052, MSTO‐211H and H28, in comparison with the T47D ER+ breast cancer cell line used as a positive control, we confirm that AREG is important for cell invasion, growth without anchorage, proliferation and apoptosis in mesothelioma cells. Yet, most of these MPM cell lines failed to correctly execute AREG posttranslational processing by metalloprotease ADAM17/tumor necrosis factor‐alpha‐converting enzyme (TACE) and extracell secretion. The favorable prognostic value of high cytosolic AREG expression in MPM patients could therefore be sustained by default AREG posttranslational processing and release. Thus, the determination of mesothelioma cell AREG content could be further investigated as a prognostic marker for MPM patients and used as a stratification factor in future clinical trials.

Exceptional response to Erlotinib monotherapy in EGFR Exon 19-deleted, KRAS wild-type, Chemo-refractory advanced pancreatic adenocarcinoma

Advanced pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive tumor with an abysmal prognosis. Beyond the first-line setting, treatment for advanced PDAC is limited and suboptimal. Also, the efficacy of epidermal growth factor receptor (EGFR) targeted therapy alone in the chemo-refractory setting in PDAC tumors harboring druggable EGFR mutations is unclear. Here we describe the case of a patient with chemo-refractory advanced PDAC with an activating exon-19 EGFR mutation who had an exceptional response to erlotinib monotherapy.

Molecular profiling of afatinib-resistant non-small cell lung cancer cells in vivo derived from mice

Non-small-cell lung cancer (NSCLC) is a leading cause of cancer-related death worldwide. NSCLC patients with overexpressed or mutated epidermal growth factor receptor (EGFR) related to disease progression are treated with EGFR-tyrosine kinase inhibitors (EGFR-TKIs). Acquired drug resistance after TKI treatments has been a major focus for development of NSCLC therapies. This study aimed to establish afatinib-resistant cell lines from which afatinib resistance-associated genes are identified and the underlying mechanisms of multiple-TKI resistance in NSCLC can be further investigated. Nude mice bearing subcutaneous NSCLC HCC827 tumors were administered with afatinib at different dose intensities (5-100 mg/kg). We established three HCC827 sublines resistant to afatinib (IC₅₀ > 1 μM) with cross-resistance to gefitinib (IC₅₀ > 5 μM). cDNA microarray revealed several of these sublines shared 27 up- and 13 down-regulated genes. The mRNA expression of selective novel genes - such as transmembrane 4 L six family member 19 (TM4SF19), suppressor of cytokine signaling 2 (SOCS2), and quinolinate phosphoribosyltransferase (QPRT) - are responsive to afatinib treatments only at high concentrations. Furthermore, c-MET amplification and activations of a subset of tyrosine kinase receptors were observed in all three resistant cells. PHA665752, a c-MET inhibitor, remarkably increased the sensitivity of these resistant cells to afatinib (IC₅₀ = 12-123 nM). We established afatinib-resistant lung cancer cell lines and here report genes associated with afatinib resistance in human NSCLC. These cell lines and the identified genes serve as useful investigational tools, prognostic biomarkers of TKI therapies, and promising molecule targets for development of human NSCLC therapeutics.

ADAM17: An Emerging Therapeutic Target for Lung Cancer

Lung cancer is the leading cause of cancer-related mortality, which histologically is classified into small-cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). NSCLC accounts for approximately 85% of all lung cancer diagnoses, with the majority of patients presenting with lung adenocarcinoma (LAC). KRAS mutations are a major driver of LAC, and are closely related to cigarette smoking, unlike mutations in the epidermal growth factor receptor (EGFR) which arise in never-smokers. Although the past two decades have seen fundamental progress in the treatment and diagnosis of NSCLC, NSCLC still is predominantly diagnosed at an advanced stage when therapeutic interventions are mostly palliative. A disintegrin and metalloproteinase 17 (ADAM17), also known as tumour necrosis factor-α (TNFα)-converting enzyme (TACE), is responsible for the protease-driven shedding of more than 70 membrane-tethered cytokines, growth factors and cell surface receptors. Among these, the soluble interleukin-6 receptor (sIL-6R), which drives pro-inflammatory and pro-tumourigenic IL-6 trans-signaling, along with several EGFR family ligands, are the best characterised. This large repertoire of substrates processed by ADAM17 places it as a pivotal orchestrator of a myriad of physiological and pathological processes associated with the initiation and/or progression of cancer, such as cell proliferation, survival, regeneration, differentiation and inflammation. In this review, we discuss recent research implicating ADAM17 as a key player in the development of LAC, and highlight the potential of ADAM17 inhibition as a promising therapeutic strategy to tackle this deadly malignancy.

Prognostic role of Amphiregulin and the correlation with androgen receptor in invasive breast cancer

BACKGROUND

In androgen-sensitive prostate cancer, androgenic stimulation induces the synthesis of amphiregulin (AREG). Research is lacking on the role of AREG in invasive breast cancer and the co-expression with androgen receptor (AR) status.

MATERIALS AND METHODS

The present study investigated the prognostic role of AREG in invasive breast cancer cases (N = 298) and the co-expression with the AR status as analysed by immunohistochemistry (IHC).

RESULTS

The samples were divided into groups according to AREG expression levels: low/no expression (AREG^low/no) and high expression (AREG^high). As shown by cytoplasmic immunostaining, 46.0% (137/298) of invasive breast cancers were AREG^high, and 54.0% (161/298) of cases were AREG^low/no. Co-expression of the AR and AREG accounted for 62.4% (186/298) of cases. A Kaplan-Meier analysis revealed that AREG^high and AR⁺/AREG^high decreased patients' overall survival (OS) (P = 0.002 and P = 0.006, respectively) and disease-free survival (DFS) (P < 0.001 and P < 0.001, respectively). In Cox models, AR⁺/AREG^high remained an independent prognostic indicator of OS and DFS in invasive breast cancer (hazard ratio [HR], 0.591, 95% confidence interval [CI], 0.407-0.859, P =  0.006; HR, 0.449, 95% CI, 0.236-0.853, P =  0.014, respectively). AREG^high remained an independent prognostic indicator of OS and DFS in estrogen receptor (ER)-negative tumours (P < 0.05).

CONCLUSIONS

This study suggested that AREG and the AR were co-expressed in invasive breast cancer. Thus, AREG and the AR may be valuable prognostic biomarkers in invasive breast cancer and promising therapeutic targets, especially in ER-negative breast cancer.

Comparative mRNA and miRNA transcriptome analysis of a mouse model of IGFIR-driven lung cancer

Mouse models of cancer play an important role in elucidating the molecular mechanisms that contribute to tumorigenesis. The extent to which these models resemble one another and their human counterparts at the molecular level is critical in understanding tumorigenesis. In this study, we carried out a comparative gene expression analysis to generate a detailed molecular portrait of a transgenic mouse model of IGFIR-driven lung cancer. IGFIR-driven tumors displayed a strong resemblance with established mouse models of lung adenocarcinoma, particularly EGFR-driven models highlighted by elevated levels of the EGFR ligands Ereg and Areg. Cross-species analysis revealed a shared increase in human lung adenocarcinoma markers including Nkx2.1 and Napsa as well as alterations in a subset of genes with oncogenic and tumor suppressive properties such as Aurka, Ret, Klf4 and Lats2. Integrated miRNA and mRNA analysis in IGFIR-driven tumors identified interaction pairs with roles in ErbB signaling while cross-species analysis revealed coordinated expression of a subset of conserved miRNAs and their targets including miR-21-5p (Reck, Timp3 and Tgfbr3). Overall, these findings support the use of SPC-IGFIR mice as a model of human lung adenocarcinoma and provide a comprehensive knowledge base to dissect the molecular pathogenesis of tumor initiation and progression.

Serum proteome mapping of EGF transgenic mice reveal mechanistic biomarkers of lung cancer precursor lesions with clinical significance for human adenocarcinomas

Atypical adenomatous hyperplasia (AAH) of the lung is a pre-invasive lesion (PL) with high risk of progression to lung cancer (LC). However, the pathways involved are uncertain. We searched for novel mechanistic biomarkers of AAH in an EGF transgenic disease model of lung cancer. Disease regulated proteins were validated by Western immunoblotting and immunohistochemistry (IHC) of control and morphologically altered respiratory epithelium. Translational work involved clinical resection material. Collectively, 68 unique serum proteins were identified by 2DE-MALDI-TOF mass spectrometry and 13 reached statistical significance (p < 0.05). EGF, amphiregulin and the EGFR endosomal sorting protein VPS28 were induced up to 5-fold while IHC confirmed strong induction of these proteins. Furthermore, ApoA1, α-2-macroglobulin, and vitamin-D binding protein were nearly 6- and 2-fold upregulated in AAH; however, ApoA1 was oppositely regulated in LC to evidence disease stage dependent regulation of this tumour suppressor. Conversely, plasminogen and transthyretin were highly significantly repressed by 3- and 20-fold. IHC confirmed induced ApoA1, Fetuin-B and transthyretin expression to influence calcification, inflammation and tumour-infiltrating macrophages. Moreover, serum ApoA4, ApoH and ApoM were 2-, 2- and 6-fold repressed; however tissue ApoM and sphingosine-1-phosphate receptor expression was markedly induced to suggest a critical role of sphingosine-1-phosphate signalling in PL and malignant transformation. Finally, a comparison of three different LC models revealed common and unique serum biomarkers mechanistically linked to EGFR, cMyc and cRaf signalling. Their validation by IHC on clinical resection material established relevance for distinct human lung pathologies. In conclusion, we identified mechanistic biomarker candidates recommended for in-depth clinical evaluation.

Suppressor of cytokine signalling-2 limits IGF1R-mediated regulation of epithelial-mesenchymal transition in lung adenocarcinoma

Non-small cell lung cancer (NSCLC), including adenocarcinoma and squamous cell carcinoma, is the leading cause of death from lung malignancies and has a poor prognosis due to metastasis. Suppressor of cytokine signalling-2 (SOCS2), a feedback inhibitor of cytokine signalling, has been shown to be involved in growth control. Here, we show that SOCS2 were significantly downregulated in tumour foci in NSCLC patients. The expression levels of SOCS2 significantly correlated with clinical stage, lymph node metastasis, histological subtype and survival time. In particular, the decreased expression of SOCS2 significantly associated with advanced pathological stage, lymph node metastasis and shorter overall survival in lung adenocarcinoma patients. In vivo animal results showed that overexpressed SOCS2 attenuated the metastatic characteristics of lung adenocarcinoma, including by inhibiting the epithelial-mesenchymal transition (EMT). Further functional studies indicated that insulin-like growth factor 1 (IGF1)-driven migratory and invasive behaviours of lung adenocarcinoma cells can be partially suppressed by exogenous SOCS2 expression. Investigations into the mechanism of action revealed that SOCS2 inhibits EMT by inactivating signal transducer and activator of transcription 3 (STAT3) and STAT5 via the competitive binding of SOCS2 to the STAT binding sites on IGF1R. Altogether, our results reveal an important role for SOCS2 dysregulation in the pathogenicity of lung adenocarcinoma, suggest its potential use as a biomarker for diagnosing lung adenocarcinoma, and paves the way to develop novel therapy targets as the axis of SOCS2-IGF1R-STAT in lung adenocarcinoma.

Compounds from the marine sponge Cribrochalina vasculum offer a way to target IGF-1R mediated signaling in tumor cells

In this work two acetylene alcohols, compound 1 and compound 2, which were isolated and identified from the sponge Cribrochalina vasculum, and which showed anti-tumor effects were further studied with respect to targets and action mechanisms. Gene expression analyses suggested insulin like growth factor receptor (IGF-1R) signaling to be instrumental in controlling anti-tumor efficacy of these compounds in non-small cell lung cancer (NSCLC). Indeed compounds 1 and 2 inhibited phosphorylation of IGF-1Rβ as well as reduced its target signaling molecules IRS-1 and PDK1 allowing inhibition of pro-survival signaling. In silico docking indicated that compound 1 binds to the kinase domain of IGF-1R at the same binding site as the well known tyrosine kinase inhibitor AG1024. Indeed, cellular thermal shift assay (CETSA) confirmed that C. vasculum compound 1 binds to IGF-1R but not to the membrane localized tyrosine kinase receptor EGFR. Importantly, we demonstrate that compound 1 causes IGF-1Rβ but not Insulin Receptor degradation specifically in tumor cells with no effects seen in normal diploid fibroblasts. Thus, these compounds hold potential as novel therapeutic agents targeting IGF-1R signaling for anti-tumor treatment.

Oncogenomics of c-Myc transgenic mice reveal novel regulators of extracellular signaling, angiogenesis and invasion with clinical significance for human lung adenocarcinoma

The c-Myc transcription factor is frequently deregulated in cancers. To search for disease diagnostic and druggable targets a transgenic lung cancer disease model was investigated. Oncogenomics identified c-Myc target genes in lung tumors. These were validated by RT-PCR, Western Blotting, EMSA assays and ChIP-seq data retrieved from public sources. Gene reporter and ChIP assays verified functional importance of c-Myc binding sites. The clinical significance was established by RT-qPCR in tumor and matched healthy control tissues, by RNA-seq data retrieved from the TCGA Consortium and by immunohistochemistry recovered from the Human Protein Atlas repository. In transgenic lung tumors 25 novel candidate genes were identified. These code for growth factors, Wnt/β-catenin and inhibitors of death receptors signaling, adhesion and cytoskeleton dynamics, invasion and angiogenesis. For 10 proteins over-expression was confirmed by IHC thus demonstrating their druggability. Moreover, c-Myc over-expression caused complete gene silencing of 12 candidate genes, including Bmp6, Fbln1 and Ptprb to influence lung morphogenesis, invasiveness and cell signaling events. Conversely, among the 75 repressed genes TNFα and TGF-β pathways as well as negative regulators of IGF1 and MAPK signaling were affected. Additionally, anti-angiogenic, anti-invasive, adhesion and extracellular matrix remodeling and growth suppressive functions were repressed. For 15 candidate genes c-Myc-dependent DNA binding and transcriptional responses in human lung cancer samples were confirmed. Finally, Kaplan-Meier survival statistics revealed clinical significance for 59 out of 100 candidate genes, thus confirming their prognostic value. In conclusion, previously unknown c-Myc target genes in lung cancer were identified to enable the development of mechanism-based therapies.

Membrane-Tethered Intracellular Domain of Amphiregulin Promotes Keratinocyte Proliferation

The epidermal growth factor receptor (EGFR) and its ligands are essential regulators of epithelial biology, which are often amplified in cancer cells. We have previously shown that shRNA-mediated silencing of one of these ligands, amphiregulin (AREG), results in keratinocyte growth arrest that cannot be rescued by soluble extracellular EGFR ligands. To further explore the functional importance of specific AREG domains, we stably transduced keratinocytes expressing tetracycline-inducible AREG-targeted shRNA with lentiviruses expressing silencing-proof, membrane-tethered AREG cytoplasmic and extracellular domains (AREG-CTD and AREG-ECD), as well as full-length AREG precursor (proAREG). Here we show that growth arrest of AREG-silenced keratinocytes occurs in G2/M and is significantly restored by proAREG and AREG-CTD but not by AREG-ECD. Moreover, the AREG-CTD was sufficient to normalize cell cycle distribution profiles and expression of mitosis-related genes. Our findings uncover an important role of the AREG-CTD in regulating cell division, which may be relevant to tumor resistance to EGFR-directed therapies.

Microenvironment rigidity modulates responses to the HER2 receptor tyrosine kinase inhibitor lapatinib via YAP and TAZ transcription factors

Stiffness is a biophysical property of the extracellular matrix that modulates cellular functions, including proliferation, invasion, and differentiation, and it also may affect therapeutic responses. Therapeutic durability in cancer treatments remains a problem for both chemotherapies and pathway-targeted drugs, but the reasons for this are not well understood. Tumor progression is accompanied by changes in the biophysical properties of the tissue, and we asked whether matrix rigidity modulated the sensitive versus resistant states in HER2-amplified breast cancer cell responses to the HER2-targeted kinase inhibitor lapatinib. The antiproliferative effect of lapatinib was inversely proportional to the elastic modulus of the adhesive substrata. Down-regulation of the mechanosensitive transcription coactivators YAP and TAZ, either by siRNA or with the small-molecule YAP/TEAD inhibitor verteporfin, eliminated modulus-dependent lapatinib resistance. Reduction of YAP in vivo in mice also slowed the growth of implanted HER2-amplified tumors, showing a trend of increasing sensitivity to lapatinib as YAP decreased. Thus we address the role of stiffness in resistance to and efficacy of a HER2 pathway-targeted therapeutic via the mechanotransduction arm of the Hippo pathway.

Transcriptome analysis of individual stromal cell populations identifies stroma-tumor crosstalk in mouse lung cancer model

Emerging studies have begun to demonstrate that reprogrammed stromal cells play pivotal roles in tumor growth, metastasis, and resistance to therapy. However, the contribution of stromal cells to non-small-cell lung cancer (NSCLC) has remained underexplored. We used an orthotopic model of Kras-driven NSCLC to systematically dissect the contribution of specific hematopoietic stromal cells in lung cancer. RNA deep-sequencing analysis of individually sorted myeloid lineage and tumor epithelial cells revealed cell-type-specific differentially regulated genes, indicative of activated stroma. We developed a computational model for crosstalk signaling discovery based on ligand-receptor interactions and downstream signaling networks and identified known and novel tumor-stroma paracrine and tumor autocrine crosstalk-signaling pathways in NSCLC. We provide cellular and molecular insights into components of the lung cancer microenvironment that contribute to carcinogenesis. This study has the potential for development of therapeutic strategies that target tumor-stroma interactions and may complement conventional anti-cancer treatments.

TGFα and amphiregulin paracrine network promotes resistance to EGFR blockade in colorectal cancer cells

PURPOSE

Targeted inhibition of EGFR with the mAbs cetuximab or panitumumab is a valuable treatment for RAS wild-type colorectal cancers. The efficacy of EGFR blockade is limited by the emergence of acquired resistance often attributed to secondary KRAS mutations. Remarkably, tumor biopsies from resistant patients show that only a fraction of the resilient cells carry KRAS mutations. We hypothesized that a paracrine cross-talk driven by the resistant subpopulation may provide in trans protection of surrounding sensitive cells.

EXPERIMENTAL DESIGN

Conditioned medium assays and three-dimensional cocultures were used to assess paracrine networks between cetuximab-sensitive and -resistant cells. Production of EGFR ligands by cells sensitive to cetuximab and panitumumab was measured. The ability of recombinant EGFR ligands to protect sensitive cells from cetuximab was assessed. Biochemical activation of the EGFR signaling pathway was measured by Western blotting.

RESULTS

Colorectal cancer cells sensitive to EGFR blockade can successfully grow despite cetuximab treatment when in the company of their resistant derivatives. Media conditioned by resistant cells protect sensitive parental cells from cetuximab. EGFR blockade triggers increased secretion of TGFα and amphiregulin. Increased secretion of ligands by resistant cells can sustain EGFR/ERK signaling in sensitive cells.

CONCLUSIONS

Colorectal cancer cells that develop resistance to cetuximab and panitumumab secrete TGFα and amphiregulin, which protect the surrounding cells from EGFR blockade. This paracrine protective mechanism might be therapeutically exploitable.

Emerging combination therapies to overcome resistance in EGFR-driven tumors

The epidermal growth factor receptor (EGFR) is responsible for the growth and progression of tumor cells; its overexpression and deregulation of its downstream signaling pathway have been found in many different neoplasms. These characteristics make it an ideal target for cancer treatment. Two classes of EGFR inhibitors, which bind to different parts of this molecule, have been developed and studied: monoclonal antibodies, such as cetuximab and panitumumab and tyrosine kinase inhibitors, including erlotinib and gefitinib. The effectiveness of these new drugs is considerably reduced by a number of mechanisms of resistance developed by tumor cells. Hence, there is a clear need for better characterization of these processes and finding new therapeutic strategies to make the action of these drugs more incisive. Here, we describe some of the mechanisms of resistance to EGFR inhibitors and review the main innovations attempting to overcome these drawbacks.

Amphiregulin

Amphiregulin (AREG) is a ligand of the epidermal growth factor receptor (EGFR), a widely expressed transmembrane tyrosine kinase. AREG is synthesized as a membrane-anchored precursor protein that can engage in juxtacrine signaling on adjacent cells. Alternatively, after proteolytic processing by cell membrane proteases, mainly TACE/ADAM17, AREG is secreted and behaves as an autocrine or paracrine factor. AREG gene expression and release is induced by a plethora of stimuli including inflammatory lipids, cytokines, hormones, growth factors and xenobiotics. Through EGFR binding AREG activates major intracellular signaling cascades governing cell survival, proliferation and motility. Physiologically, AREG plays an important role in the development and maturation of mammary glands, bone tissue and oocytes. Chronic elevation of AREG expression is increasingly associated with different pathological conditions, mostly of inflammatory and/or neoplastic nature. Here we review the essential aspects of AREG structure, function and regulation, discuss the basis for its differential role within the EGFR family of ligands, and identify emerging aspects in AREG research with translational potential.

The PI3K/AKT pathway promotes gefitinib resistance in mutant KRAS lung adenocarcinoma by a deacetylase-dependent mechanism

To select the appropriate patients for treatment with epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs), it is important to gain a better understanding of the intracellular pathways leading to EGFR-TKI resistance, which is a common problem in patients with lung cancer. We recently reported that mutant KRAS adenocarcinoma is resistant to gefitinib as a result of amphiregulin and insulin-like growth factor-1 receptor overexpression. This resistance leads to inhibition of Ku70 acetylation, thus enhancing the BAX/Ku70 interaction and preventing apoptosis. Here, we determined the intracellular pathways involved in gefitinib resistance in lung cancers and explored the impact of their inhibition. We analyzed the activation of the phosphatidyl inositol-3-kinase (PI3K)/AKT pathway and the mitogen-activated protein kinase/extracellular-signal regulated kinase (MAPK/ERK) pathway in lung tumors. The activation of AKT was associated with disease progression in tumors with wild-type EGFR from patients treated with gefitinib (phase II clinical trial IFCT0401). The administration of IGF1R-TKI or amphiregulin-directed shRNA decreased AKT signaling and restored gefitinib sensitivity in mutant KRAS cells. The combination of PI3K/AKT inhibition with gefitinib restored apoptosis via Ku70 downregulation and BAX release from Ku70. Deacetylase inhibitors, which decreased the BAX/Ku70 interaction, inhibited AKT signaling and induced gefitinib-dependent apoptosis. The PI3K/AKT pathway is thus a major pathway contributing to gefitinib resistance in lung tumors with KRAS mutation, through the regulation of the BAX/Ku70 interaction. This finding suggests that combined treatments could improve the outcomes for this subset of lung cancer patients, who have a poor prognosis.

Insulin-like growth factor-1 receptor (IGF-1R) as a biomarker for resistance to the tyrosine kinase inhibitor gefitinib in non-small cell lung cancer

BACKGROUND

The insulin-like growth factor-1 receptor (IGF-1R) pathway is known to play a role in the acquisition of resistance to epidermal growth factor receptor (EGFR)-specific tyrosine kinase inhibitors (TKIs) in non-small cell lung cancer (NSCLC). However, its exact role in TKI resistance has so far remained unclear. Here, we interrogated the hypothesis that the IGF-1R may serve as a biomarker for, and may play a role in, intrinsic resistance to the EGFR-specific TKI gefitinib in NSCLC.

METHODS

Total-IGF-1R and phosphorylated (p)-IGF-1R expression levels were related to gefitinib sensitivity in 23 NSCLC cell lines. This sensitivity was re-evaluated after knocking down IGF-1R expression and after IGF-1R up-regulation through exogenous IGF-1 expression. The utility of IGF-1R expression as a predictive biomarker was also evaluated by immunohistochemistry (IHC) in 98 primary NSCLC samples from patients treated with gefitinib.

RESULTS

Seventeen of the cell lines tested were resistant to gefitinib, whereas 3 cell lines were sensitive. The three remaining cell lines showed intermediate values. Thirteen resistant cell lines were found to be positive for total-IGF-1R expression, while all the sensitive cell lines were negative, resulting in a positive predictive value (PPV) of 81% for total-IGF-1R to predict resistance. Seven resistant cell lines exhibited high p-IGF-1R levels, whereas all 3 sensitive cell lines were negative for p-IGF-1R, resulting in a PPV of 100% for p-IGF-1R to predict resistance. Neither a knock-down of IGF-1R expression nor an activation of the IGF1-R pathway through exogenous IGF-1 expression affected gefitinib sensitivity. In primary NSCLC tissues, IGF-1R expression was found to be significantly higher in patients with progressive disease, i.e., showing gefitinib resistance, as compared to those with a complete or partial response.

CONCLUSIONS

IGF-1R acts as a predictor for resistance to gefitinib in NSCLC cell lines and NSCLC patients, but does not seem to play a role in the intrinsic resistance to this drug. High total-IGF-1R and p-IGR-1R levels may predict such a resistance. Since the underlying mechanism does not appear to be related to proliferation induction, alternative pathways should be explored.

Mechanisms of resistance to endocrine therapy in breast cancer: focus on signaling pathways, miRNAs and genetically based resistance

Breast cancer is the most frequent malignancy diagnosed in women. Approximately 70% of breast tumors express the estrogen receptor (ER). Tamoxifen and aromatase inhibitors (AIs) are the most common and effective therapies for patients with ERα-positive breast cancer. Alone or combined with chemotherapy, tamoxifen significantly reduces disease progression and is associated with more favorable impact on survival in patients. Unfortunately, endocrine resistance occurs, either de novo or acquired during the course of the treatment. The mechanisms that contribute to hormonal resistance include loss or modification in the ERα expression, regulation of signal transduction pathways, altered expression of specific microRNAs, balance of co-regulatory proteins, and genetic polymorphisms involved in tamoxifen metabolic activity. Because of the clinical consequences of endocrine resistance, new treatment strategies are arising to make the cells sensitive to tamoxifen. Here, we will review the current knowledge on mechanisms of endocrine resistance in breast cancer cells. In addition, we will discuss novel therapeutic strategies to overcome such resistance. Undoubtedly, circumventing endocrine resistance should help to improve therapy for the benefit of breast cancer patients.

HER family receptor and ligand status in thymic carcinoma

Overexpression and gene amplification of the HER family of receptors and their ligands are important prognostic factors in many solid tumors and treatment targeting these molecules has recently become available. The role of this group of receptors has only rarely been described in thymic epithelial neoplasms and never before in a series of cases consisting exclusively of thymic carcinoma. Twenty-four primary squamous cell carcinomas of the thymus were examined for immunohistochemical expression of epidermal growth factor receptor (EGFR), phosphorylated EGFR (pEGFR), HER2, phosphorylated HER2 (pHER2), HER3, phosphorylated HER3 (pHER3) and their ligands epidermal growth factor (EGF), transforming growth factor-α (TGF-α), amphiregulin and epiregulin. Fluorescence in situ hybridization (FISH) analysis for amplification of the EGFR and HER2 genes was performed including assessment of the copy numbers of EGFR and HER2 gene per cell and the ratio of EGFR and HER2 to centromere 7 and 17, respectively. Significant immunohistochemical expression was observed for EGFR (33.3%), pEGFR (33.3%), HER2 (58.3%), HER3 (45.8%), TGF-α (54.1%), amphiregulin (25.0%) and epiregulin (91.7%). A single case showed HER2 gene amplification by FISH. Increased EGFR and HER2 gene copy numbers were observed in 2 (8.4%) and 18 cases (75%), respectively. Eight cases (33.3%) showed an increased HER2:CEP17 ratio. The results of this study indicate that EGFR and HER2 amplification is a rare event in thymic carcinoma, however, protein expression for HER receptors as well as their ligands is a common finding indicating that targeted therapy directed against these molecules may be considered in the treatment of these tumors.

Strategies for overcoming resistance to EGFR family tyrosine kinase inhibitors

The first-generation epidermal growth factor receptor tyrosine kinase inhibitors erlotinib and gefitinib have been incorporated into treatment paradigms for patients with advanced non-small cell lung cancer. These agents are particularly effective in a subset of patients whose tumors harbor activating epidermal growth factor receptor mutations. However, most patients do not respond to these tyrosine kinase inhibitors, and those who do will eventually acquire resistance that typically results from a secondary epidermal growth factor receptor mutation (e.g., T790M), mesenchymal-epithelial transition factor amplification, or activation of other signaling pathways. For patients whose tumors have wild-type epidermal growth factor receptor, there are several known mechanisms of initial resistance (e.g., Kirsten rat sarcoma viral oncogene homolog mutations) but these do not account for all cases, suggesting that unknown mechanisms also contribute. To potentially overcome the issue of resistance, next-generation tyrosine kinase inhibitors are being developed, which irreversibly block multiple epidermal growth factor receptor family members (e.g., afatinib [BIBW 2992] and PF-00299804) and/or vascular endothelial growth factor receptor pathways (e.g., BMS-690514 and XL647). In addition, drugs that block parallel signaling pathways or signaling molecules downstream of the epidermal growth factor receptor, such as the insulin-like growth factor-1 receptor and the mammalian target of rapamycin, are undergoing clinical evaluation. As drug resistance appears to be pleomorphic, combinations of drugs or drugs with multiple targets may be more effective in circumventing resistance.

Dual epidermal growth factor receptor (EGFR)/insulin-like growth factor-1 receptor (IGF-1R) inhibitor: a novel approach for overcoming resistance in anticancer treatment

Small molecule inhibitors of epidermal growth factor receptors (EGFR) have been found to show a good initial response in cancer patients but during the course of treatment, patients develop resistance after a few weeks of time. Development of secondary mutations or over-activation of insulin like growth factor (IGF-1R) pathway are a few of the several mechanisms proposed to explain the resistance. To study the effect of dual inhibition of EGFR and IGF-1R in overcoming the resistance, three strategies were envisaged and are reported in this manuscript: 1) a virtual predictive tumor model, 2) in vitro experimental data using a combination of EGFR and IGF-1R inhibitors and 3) in vitro experimental data using in house dual inhibitors. Findings reported in this manuscript suggest that simultaneous inhibition of IGF-1R and EGFR either by combination of two inhibitors or by dual kinase inhibitors is more efficacious compared to single agents. In vitro cell based experiments conducted using epidermoid cancer cell line, A431 and an EGFR mutant cell line, H1975 along with virtual predictions reported here suggests that dual inhibition of EGFR and IGF-1R is a viable approach to overcome EGFR resistance.

The multiple roles of amphiregulin in human cancer

Amphiregulin (AREG) is one of the ligands of the epidermal growth factor receptor (EGFR). AREG plays a central role in mammary gland development and branching morphogenesis in organs and is expressed both in physiological and in cancerous tissues. Various studies have highlighted the functional role of AREG in several aspects of tumorigenesis, including self-sufficiency in generating growth signals, limitless replicative potential, tissue invasion and metastasis, angiogenesis, and resistance to apoptosis. The oncogenic activity of AREG has already been described in the most common human epithelial malignancies, such as lung, breast, colorectal, ovary and prostate carcinomas, as well as in some hematological and mesenchymal cancers. Furthermore, AREG is also involved in resistance to several cancer treatments. In this review, we describe the various roles of AREG in oncogenesis and discuss its translational potential, such as the development of anti-AREG treatments, based on AREG activity. In the last decade, independent groups have reported successful but sometimes contradictory results in relation to the potential of AREG to serve as a prognostic and/or predictive marker for oncology, especially with regard to anti-EGFR therapies. Thus, we also discuss the potential usefulness of using AREG as a therapeutic target and validated biomarker for predicting cancer outcomes or treatment efficacy.

Insulin-like growth factor-1 receptor inhibition overcomes gefitinib resistance in mucinous lung adenocarcinoma

The appropriate selection of patients is a major challenge in the treatment of non-small cell lung cancer (NSCLC) with epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs). Prospective trials in adenocarcinoma demonstrated that the mucinous subtype presents a poorer outcome under EGFR-TKI treatment than the non-mucinous subtype. Our aim was to determine the molecular characteristics associated with resistance to EGFR-TKIs in mucinous and non-mucinous adenocarcinoma. Eighty adenocarcinoma samples, including 34 tumours from patients treated with gefitinib in a phase II clinical trial (IFCT0401), were classified as mucinous (n = 32) or non-mucinous (n = 48) adenocarcinoma. We demonstrated that four biological markers were differentially expressed between the two subtypes: mucinous tumours that overexpressed IGF1R (p < 0.0001) and amphiregulin (p = 0.004) with a tendency for more frequent KRAS mutations, in contrast to non-mucinous tumours that overexpressed EGFR (p < 0.0001) and TTF-1 (p < 0.0001) with more frequent EGFR mutations (p = 0.037). Higher IGF1R (p = 0.02) and lower TTF-1 (p = 0.02) expression was associated with disease progression under gefitinib treatment. We observed in vitro cross-talk between EGFR and IGF1R signalling pathways in gefitinib-resistant H358 mucinous cells. Anti-amphiregulin siRNAs and anti-IGF1R treatments sensitized the H358 cells to gefitinib-induced apoptosis with additive effects, suggesting that these treatments could overcome the resistance of mucinous tumours to EGFR-TKIs, including those with KRAS mutation. Our results highlighted that mucinous and non-mucinous adenocarcinoma subtypes are different entities with different therapeutic responses to EGFR-TKIs. These data will foster the development of therapeutic strategies for treating adenocarcinoma with mucinous component.

Neisseria gonorrhoeae infection induces altered amphiregulin processing and release

Adhesion of the human pathogen Neisseria gonorrhoeae has established effects on the host cell and evokes a variety of cellular events including growth factor activation. In the present study we report that infection with N. gonorrhoeae causes altered amphiregulin processing and release in human epithelial cells. Amphiregulin is a well-studied growth factor with functions in various cell processes and is upregulated in different forms cancer and proliferative diseases. The protein is prototypically cleaved on the cell surface in response to external stimuli. We demonstrate that upon infection, a massive upregulation of amphiregulin mRNA is seen. The protein changes its subcellular distribution and is also alternatively cleaved at the plasma membrane, which results in augmented release of an infection-specific 36 kDa amphiregulin product from the surface of human cervical epithelial cells. Further, using antibodies directed against different domains of the protein we could determine the impact of infection on pro-peptide processing. In summary, we present data showing that the infection of N. gonorrhoeae causes an alternative amphiregulin processing, subcellular distribution and release in human epithelial cervical cells that likely contribute to the predisposition cellular abnormalities and anti-apoptotic features of N. gonorrhoeae infections.

RSK in tumorigenesis: connections to steroid signaling

The Ser/Thr kinase family, RSK, has been implicated in numerous types of hormone-dependent and -independent cancers. However, there has been little consideration of RSKs as downstream mediators of steroid hormone non-genomic effects or of their ability to facilitate steroid receptor-mediated gene expression. Steroid hormone signaling can directly stimulate the MEK/ERK/RSK pathway to regulate cellular proliferation and survival in transformed cells. To date, multiple mechanisms of RSK and steroid hormone receptor-mediated proliferation/survival have been elucidated. For example, RSK enhances proliferation of breast and prostate cancer cells via its ability to control the levels of the estrogen receptor co-activator, cyclin D1. While in lung and other tumors RSK may control apoptosis via estrogen-mediated regulation of mitochondrial integrity. Thus the RSKs could be important anti-cancer therapeutic targets in many different transformed tissues. The recent discovery of RSK-specific inhibitors will advance our current understanding of RSK in transformation and drive these studies into animal and clinical models. In this review we explore the mechanisms associated with RSK in tumorigenesis and their relationship to steroid hormone signaling.

Novel targets in esophageal and gastric cancer: beyond antiangiogenesis

Cancers of the stomach, gastroesophageal junction and esophagus are a major cause of cancer-related deaths worldwide. In Western countries, adenocarcinomas of the distal esophagus, gastroesophageal junction and proximal stomach have been increasing in frequency more rapidly than other malignancies. The majority of newly diagnosed patients present with advanced disease and the overall survival remains dismal at approximately 10% at 5 years. Better understanding of tumor biology has led to the development of promising novel therapeutic strategies. There is therefore increasing optimism that some of these approaches will improve the outcomes in these increasingly common cancers. Given the success of antiangiogenesis as a therapeutic strategy in various types of cancer, there are ongoing efforts to investigate the utility of other targeted therapies in the treatment of gastric and esophageal cancers. This review will focus on novel therapeutic targets other than angiogenesis and provide a rationale for the further clinical evaluation of these agents in patients with upper gastrointestinal tract cancers.

The cell line secretome, a suitable tool for investigating proteins released in vivo by tumors: application to the study of p53-modulated proteins secreted in lung cancer cells

Malignant processes such as metastasis, invasion, or angiogenesis are tightly dependent on the composition of the extracellular medium, which is itself affected by the release of proteins by the tumor cells. p53, a major tumor suppressor protein very frequently mutated and/or inactivated in cancer cells, is known to modulate the release of proteins by the tumor cells; however, while p53-modulated intracellular proteins have been extensively studied, little is known concerning their extracellular counterparts. Here, we characterized the p53-dependent secretome of a lung tumor model in vitro (H358 human nonsmall cell lung adenocarcinoma cell line with a homozygous deletion of p53) and demonstrate that the modulation of exported proteins can also be detected in vivo in the plasma of tumor-bearing mice. We used a clone of H358, stably transfected with a tetracycline-inducible wild-type p53-expressing vector. With the use of iTRAQ labeling and LC-MALDI-MS/MS analysis, we identified 909 proteins released in vitro by the cells, among which 91 are p53-modulated. Three proteins (GDF-15, FGF-19, and VEGF) were also investigated in H358/TetOn/p53 xenograft mice. The ELISA dosage on total tumor protein extracts confirmed the influence of p53 on the release of these proteins in vivo. Moreover, the GDF-15 concentration was measured in the plasma and its p53-dependent modulation was confirmed. To our knowledge, this is the first report establishing that the in vitro cell line secretome is reliable and reflects the extracellular release of proteins from tumor cells in vivo and could be used to identify putative tumor markers.

Amphiregulin promotes BAX inhibition and resistance to gefitinib in non-small-cell lung cancers

Molecular resistance mechanisms affecting the efficiency of receptor tyrosine kinase inhibitors such as gefitinib in non-small-cell lung cancer (NSCLC) cells are not fully understood. Amphiregulin (Areg) overexpression has been proposed to predict NSCLC resistance to gefitinib and we have established that Areg-overexpressing H358 NSCLC cells resist apoptosis. Here, we demonstrate that Areg prevents gefitinib-induced apoptosis in NSCLC cells. We show that H358 cells are resistant to gefitinib in contrast to H322 cells, which do not overexpress Areg. Inhibition of Areg expression by small-interfering RNAs (siRNAs) restores gefitinib sensitivity in H358 cells, whereas addition of recombinant Areg confers resistance in H322 cells. Areg knockdown overcomes resistance to gefitinib and induced apoptosis in NSCLC H358 cells in vitro and in vivo. Under gefitinib treatment, Areg decreases the expression of the proapoptotic protein BAX, inhibits its conformational change and its mitochondrial translocation. Thus, in the presence of Areg, gefitinib-mediated apoptosis is reduced because BAX is sequestered in the cytoplasm. This suggests that treatments using epidermal growth factor receptor (EGFR) inhibitors may be poorly efficient in patients with elevated levels of Areg. These findings indicate the need for inhibition of Areg to enhance the efficiency of the EGFR inhibitors in patients suffering NSCLC.

Amphiregulin promotes resistance to gefitinib in nonsmall cell lung cancer cells by regulating Ku70 acetylation

Multiple molecular resistance mechanisms reduce the efficiency of receptor tyrosine kinase inhibitors such as gefitinib in non-small cell lung cancer (NSCLC). We previously demonstrated that amphiregulin (Areg) inhibits gefitinib-induced apoptosis in NSCLC cells by inactivating the proapoptotic protein BAX. In this part of the investigation, we studied the molecular mechanisms leading to BAX inactivation. We show that Areg prevents gefitinib-mediated acetylation of Ku70. This augments the BAX-Ku70 interaction and therefore prevents BAX-mediated apoptosis. Accordingly, Areg or Ku70 knock down restore BAX activation and apoptosis in gefitinib-treated H358 cells in vitro. In addition, overexpression of the histone acetyltransferase (HAT) CREB-binding protein (CBP) or treatments with histone deacetylase (HDAC) inhibitors sensitize H358 cells to gefitinib. Moreover, a treatment with vorinostat, a HDAC inhibitor strongly sensitized tumors to gefitinib in vivo. These findings suggest new prospects in combining both HDAC and epidermal growth factor receptor inhibitors for the treatment of NSCLC.

Cancer genomics identifies regulatory gene networks associated with the transition from dysplasia to advanced lung adenocarcinomas induced by c-Raf-1

BACKGROUND

Lung cancer is a leading cause of cancer morbidity. To improve an understanding of molecular causes of disease a transgenic mouse model was investigated where targeted expression of the serine threonine kinase c-Raf to respiratory epithelium induced initially dysplasia and subsequently adenocarcinomas. This enables dissection of genetic events associated with precancerous and cancerous lesions.

METHODOLOGY/PRINCIPAL FINDINGS

By laser microdissection cancer cell populations were harvested and subjected to whole genome expression analyses. Overall 473 and 541 genes were significantly regulated, when cancer versus transgenic and non-transgenic cells were compared, giving rise to three distinct and one common regulatory gene network. At advanced stages of tumor growth predominately repression of gene expression was observed, but genes previously shown to be up-regulated in dysplasia were also up-regulated in solid tumors. Regulation of developmental programs as well as epithelial mesenchymal and mesenchymal endothelial transition was a hall mark of adenocarcinomas. Additionally, genes coding for cell adhesion, i.e. the integrins and the tight and gap junction proteins were repressed, whereas ligands for receptor tyrosine kinase such as epi- and amphiregulin were up-regulated. Notably, Vegfr- 2 and its ligand Vegfd, as well as Notch and Wnt signalling cascades were regulated as were glycosylases that influence cellular recognition. Other regulated signalling molecules included guanine exchange factors that play a role in an activation of the MAP kinases while several tumor suppressors i.e. Mcc, Hey1, Fat3, Armcx1 and Reck were significantly repressed. Finally, probable molecular switches forcing dysplastic cells into malignantly transformed cells could be identified.

CONCLUSIONS/SIGNIFICANCE

This study provides insight into molecular pertubations allowing dysplasia to progress further to adenocarcinoma induced by exaggerted c-Raf kinase activity.

Molecular characterization of lung dysplasia induced by c-Raf-1

Background

Lung cancer is a multistage process with poor prognosis and high morbidity. Importantly, the genetics of dysplasia, a facultative cancer, at the edge of malignant transformation is unknown.

Methodology/Principal Findings

We employed laser microdissection to harvest c-Raf1- induced dysplastic as opposed to transgenic but otherwise morphologically unaltered epithelium and compared findings to non-transgenic lung. We then employed microarrays to search genome wide for gene regulatory networks. A total of 120 and 287 genes were significantly regulated, respectively. Dysplasia was exclusive associated with up-regulation of genes coding for cell growth and proliferation, cell-to-cell signalling and interaction, lipid metabolism, development, and cancer. Likewise, when dysplasia was compared with non-transgenic cells up-regulation of cancer associated genes, tight junction proteins, xenobiotic defence and developmental regulators was observed. Further, in a comparison of the data sets of dysplasia vs transgenic and dysplasia vs non-transgenic 114 genes were regulated in common. We additionally confirmed regulation of some genes by immunohistochemistry and therefore demonstrate good concordance between gene regulation and coded protein.

Conclusion

Our study identified transcriptional networks at successive stages of tumor-development, i.e. from histological unaltered but transgenic lungs to nuclear atypia. Our SP-C/c-raf transgenic mouse model revealed interesting and novel candidate genes and pathways that provide clues on the mechanism forcing respiratory epithelium into dysplasia and subsequently cancer, some of which might also be useful in the molecular imaging and flagging of early stages of disease.

Relationship between amphiregulin and airway inflammation in children with asthma and eosinophilic bronchitis

BACKGROUND

Amphiregulin, a member of the epidermal growth factor family, has been shown to promote the growth of fibroblasts, to be associated with the T-helper type 2 cell adaptive immune response, and to up-regulate mucin gene expression. We aimed to determine whether sputum amphiregulin is expressed at elevated levels in patients with asthma or eosinophilic bronchitis (EB), and whether it is associated with eosinophilic inflammation, pulmonary function, and bronchial hyperresponsiveness in children.

METHODS

A total of 117 children with asthma, 77 with EB, and 84 control subjects were enrolled in this study. Amphiregulin and eosinophil cationic protein (ECP) levels were measured in sputum supernatants. We performed pulmonary function and methacholine challenge tests while measuring total eosinophil count, and serum levels of total IgE and ECP in all children.

RESULTS

The children with asthma had significantly higher levels of sputum amphiregulin (mean, 10.80 pg/mL; range, 4.07 to 38.75 pg/mL) than both the children with EB (mean, 5.76 pg/mL; range, 0.61 to 21.65 pg/mL; p = 0.013) and the control subjects (mean, 6.56 pg/mL; range, 0.51 to 17.98 pg/mL; p = 0.003). Sputum amphiregulin levels positively correlated with levels of sputum eosinophils (gamma = 0.221; p = 0.007) and sputum ECP (gamma = 0.601; p < 0.0001). Negative significant correlations were found between sputum amphiregulin and FEV(1) (gamma = -0.181; p = 0.006) or post-bronchodilator therapy FEV(1) (gamma = -0.233; p = 0.002). In children with asthma who were not receiving any controller medications, sputum amphiregulin level was negatively correlated with the provocative concentration of methacholine causing a 20% fall in FEV(1) (r = -0.398; p = 0.008).

CONCLUSIONS

Our findings suggest that childhood asthma is associated with sputum amphiregulin, whereas EB is not, and that sputum amphiregulin would be a supportive marker of airway inflammation in asthma.

EGFR Inhibition in the Treatment of Non-Small Cell Lung Cancer

Epidermal growth factor receptor (EGFR) inhibitors have introduced the concept of targeted therapy to the treatment of non-small cell lung cancer (NSCLC). These agents appear most effective in patients with tumors that are highly dependent on EGFR signaling pathways, a population that disproportionately includes females, nonsmokers, individuals of East Asian origin, and patients with adenocarcinoma histology. Currently available EGFR-inhibiting drugs include the tyrosine kinase inhibitors (TKIs) erlotinib, gefitinib, and lapatinib, which are administered orally and interfere with the intracellular tyrosine kinase domain, and the monoclonal antibodies (mAbs) cetuximab and panitumumab, which are administered intravenously and interfere with extracellular ligand binding. While the use of EGFR TKIs as monotherapy prolongs survival in metastatic NSCLC, they have demonstrated no benefit when added to conventional, cytotoxic chemotherapy. In contrast, the anti-EGFR mAb cetuximab appears most effective when combined with chemotherapy or radiation. Despite dramatic initial responses to treatment in some cases, NSCLC eventually becomes resistant to EGFR inhibition. Possible mechanisms include secondary mutations that interfere with drug binding, oncogenic pathways driven by other receptor tyrosine kinases, and independent activity of downstream signaling molecules. Efforts to overcome such resistance include irreversibly binding EGFR TKIs, multi-targeted TKIs, and combinations with chemotherapy, radiation, and other targeted therapies.

The effect of interleukin-4 and amphiregulin on the proliferation of human airway smooth muscle cells and cytokine release

Airway smooth muscle (ASM) hyperplasia and angiogenesis are important features associated with airway remodeling. We investigated the effect of IL-4 and amphiregulin, an epidermal growth factor family member, on the proliferation of human ASM cells and on the release of vascular endothelial growth factor (VEGF) and monocyte chemotactic protein (MCP)-1 from human ASM cells. Human ASM cells were growth-arrested for 48 hr and incubated with platelet-derived growth factor (PDGF)- BB, interleukin (IL)-4, amphiregulin, and VEGF to evaluate cell proliferation. The cells were treated with PDGF, IL-4 and amphiregulin to evaluate the release of VEGF, MCP-1. IL-4 suppressed unstimulated and PDGF-stimulated ASM cell proliferation. Amphiregulin stimulated ASM cell proliferation in a dose-dependent manner. VEGF did not have any influence on ASM cell proliferation. IL-4 stimulated VEGF secretion by the ASM cells in a dose-dependent manner and showed added stimulatory effects when co-incubated with PDGF. Amphiregulin did not promote VEGF secretion. IL-4 and amphiregulin showed no stimulatory effects on MCP-1 secretion. The results of this study showed that IL-4 had bifunctional effects on airway remodeling, one was the suppression of the proliferation of the ASM cells and the other was the promotion of VEGF release by the ASM cells, and amphiregulin can promote human ASM cell proliferation.

Gene Expression Studies Demonstrate that the K-ras/Erk MAP Kinase Signal Transduction Pathway and Other Novel Pathways Contribute to the Pathogenesis of Cumene-induced Lung Tumors

National Toxicology Program (NTP) inhalation studies demonstrated that cumene significantly increased the incidence of alveolar/bronchiolar adenomas and carcinomas in B6C3F1 mice. Cumene or isopropylbenzene is a component of crude oil used primarily in the production of phenol and acetone. The authors performed global gene expression analysis to distinguish patterns of gene regulation between cumene-induced tumors and normal lung tissue and to look for patterns based on the presence or absence of K- ras and p53 mutations in the tumors. Principal component analysis segregated the carcinomas into groups with and without K- ras mutations, but failed to separate the tumors based on p53 mutation status. Expression of genes associated with the Erk MAP kinase signaling pathway was significantly altered in carcinomas with K- ras mutations compared to tumors without K- ras mutations or normal lung. Gene expression analysis also suggested that cumene-induced carcinomas with K- ras mutations have greater malignant potential than those without mutations. In addition, significance analysis of function and expression (SAFE) demonstrated expression changes of genes regulated by histone modification in carcinomas with K- ras mutations. The gene expression analysis suggested the formation of alveolar/bronchiolar carcinomas in cumene-exposed mice typically involves mutation of K- ras, which results in increased Erk MAP kinase signaling and modification of histones.

Co-targeting insulin-like growth factor I receptor and HER2: dramatic effects of HER2 inhibitors on nonoverexpressing breast cancer

The insulin-like growth factor I receptor (IGFIR) and HER2 display important signaling interactions in breast cancer. We examined the effect of combinations of antagonists of these receptors using two human breast cancer cell lines: BT474 (HER2+, IGFIR low) and MCF7 (HER2 low, IGFIR high). In BT474 cells, growth was inhibited by HER2 antagonists but not by IGFIR antagonists; however, IGFIR antagonists enhanced the effect of HER2 inhibitors. In MCF7 cells, growth was inhibited by IGFIR antagonists but not by HER2 antagonists; however, HER2 antagonism enhanced the effect of IGFIR inhibitors. Synergistic inhibition of soft agar growth was also observed. Although HER2 and IGFIR antagonists individually only minimally affected cell cycle, their combination gave a small enhancement of their effects. No single receptor-targeting drug was capable of inducing apoptosis, but combining antagonists of both receptors induced a dramatic degree of apoptosis in both cell lines. Induction of apoptosis was most striking in MCF7 cells using a Herceptin/IGFIR antagonist combination despite these cells being HER2 nonoverexpressing. Toward understanding the mechanism of these effects, we detected coassociation IGFIR and HER2 in both cell lines. Specific inhibitors of one of these receptors could cross-inhibit the activity of the other. Targeting both receptors gave the maximal inhibition of their downstream extracellular signal-regulated kinase 1/2 and AKT signaling pathways. Hence, such drug combinations may be clinically useful and may be beneficial even in tumors in which single drugs are inactive, as exemplified by the effect of the HER2/IGFIR inhibitor combination in HER2 nonoverexpressing MCF7 cells.

Growth factor signalling in endocrine and anti-growth factor resistant breast cancer

Growth factors provide powerful mitogenic and survival signals to breast cancer cells and it is therefore not surprising that they are able to subvert inhibitory responses to anti-hormonal drugs. In this review we discuss several mechanisms by which this may be achieved and expand our observations to encompass recently emerging anti-growth factor treatments. The information presented is underpinned by inhibitor studies that show the targeting of such mechanisms in advance of anti-hormone or anti-growth factor resistance development is able to substantially delay this event, thus pointing the way forward to intelligent combination therapies relevant to the future management of breast cancer.

A novel, potent, and selective insulin-like growth factor-I receptor kinase inhibitor blocks insulin-like growth factor-I receptor signaling in vitro and inhibits insulin-like growth factor-I receptor dependent tumor growth in vivo

Insulin-like growth factor-I receptor (IGF-IR) and its ligands, IGF-I and IGF-II, are up-regulated in a variety of human cancers. In tumors, such as colorectal, non-small cell lung, ovarian, and pediatric cancers, which may drive their own growth and survival through autocrine IGF-II expression, the role of IGF-IR is especially critical. Here, we present a novel small-molecule IGF-IR kinase inhibitor, cis-3-[3-(4-methyl-piperazin-l-yl)-cyclobutyl]-1-(2-phenyl-quinolin-7-yl)-imidazo[1,5-a]pyrazin-8-ylamine (PQIP), which displayed a cellular IC(50) of 19 nmol/L for inhibition of ligand-dependent autophosphorylation of human IGF-IR with 14-fold cellular selectivity relative to the human insulin receptor. PQIP showed minimal activity against a panel of 32 other protein kinases. It also abolished the ligand-induced activation of downstream phosphorylated AKT and phosphorylated extracellular signal-regulated kinase 1/2 in both IGF-IR transfectant cells and a GEO human colorectal cancer cell line. Analysis of GEO cells revealed a significant level of both phosphorylated IGF-IR and IGF-II expression. Furthermore, inactivation of IGF-II in conditioned GEO culture medium by a neutralizing antibody diminished IGF-IR activation, indicating the presence of a functional IGF-II/IGF-IR autocrine loop in GEO cells. Once daily oral dosing of PQIP induced robust antitumor efficacy in GEO xenografts. The antitumor efficacy correlated with the degree and duration of inhibition of tumor IGF-IR phosphorylation in vivo by this compound. Moreover, when mice were treated for 3 days with a dose of PQIP that maximally inhibited tumor growth, only minor changes in blood glucose were observed. Thus, PQIP represents a potent and selective IGF-IR kinase inhibitor that is especially efficacious in an IGF-II-driven human tumor model.

Amphiregulin: A new growth factor in hepatocarcinogenesis

Amphiregulin (AR) is a member of the epidermal growth factor family and a ligand of the epidermal growth factor receptor (EGFR). As other ligands of the EGFR, AR is synthesized as a precursor that is shed from the plasma membrane by metalloproteases. Hyperactive autocrine loops involving AR production have been described in a variety of tumors, and this growth factor is thought to play a non-redundant role in cancer development. AR expression is not detected in the normal liver, however it is readily induced during acute liver injury and behaves as a potent pro-regenerative and survival factor. Increased AR expression is also detected in human chronic liver injury (liver cirrhosis), which is considered a pre-neoplastic condition. Recent evidences suggest that AR can play a unique role in liver tumorigenesis and in the maintenance of the neoplastic phenotype of hepatocarcinoma cells. In this review, we summarize some aspects of AR patho-biology and the rationale behind its definition as a novel target in hepatocarcinoma therapy.

The molecular signature of MDS stem cells supports a stem-cell origin of 5q myelodysplastic syndromes

Global gene expression profiling of highly purified 5q-deleted CD34+CD38(-)Thy1+ cells in 5q- myelodysplastic syndromes (MDSs) supported that they might originate from and outcompete normal CD34+CD38(-)Thy1+ hematopoietic stem cells. Few but distinct differences in gene expression distinguished MDS and normal stem cells. Expression of BMI1, encoding a critical regulator of self-renewal, was up-regulated in 5q- stem cells. Whereas multiple previous MDS genetic screens failed to identify altered expression of the gene encoding the myeloid transcription factor CEBPA, stage-specific and extensive down-regulation of CEBPA was specifically observed in MDS progenitors. These studies establish the importance of molecular characterization of distinct stages of cancer stem and progenitor cells to enhance the resolution of stage-specific dysregulated gene expression.

Combination of radiotherapy with EGFR antagonists for head and neck carcinoma

The introduction of biologically sound radiation fractionation regimens and combinations of radiotherapy with chemotherapy have gradually improved both the survival of patients with locally advanced head and neck squamous cell carcinoma (HNSCC) and the prospect of organ preservation. Long-term follow-up, however, has shown that some of the radiation-chemotherapy combinations are associated with increased late toxicity. This observation, in conjunction with advances in tumor biology, has led to the launch of investigations into molecular markers and targets for therapeutic interventions. Research on the epidermal growth factor receptor (EGFR)-mediated signaling pathway has enriched our understanding of the biology of HNSCC, in terms of carcinogenesis and cellular processes governing tumor response to therapy. The finding that the addition of an antibody-based inhibitor of the EGFR pathway to radiotherapy significantly improves locoregional control and overall survival rates in patients with locally advanced HNSCC, without increasing radiation-induced toxicity, has resulted in the growing acceptance of such combined regimens as a frontline therapy option for locally advanced HNSCC. Because such therapy has benefited only an additional 10%-15% of patients, studies are being undertaken to identify markers and mechanisms of resistance to EGFR antagonists that are essential for the further refinement of therapy. Overall, preclinical and clinical studies on EGFR have validated the concept that selective tumor radiation sensitization can be achieved by modulating a specific perturbed signaling pathway, and these studies have increased the enthusiasm for developing and investigating other novel agents targeting other cellular processes.

Gastrin-releasing peptide activates Akt through the epidermal growth factor receptor pathway and abrogates the effect of gefitinib

Gastrin-releasing peptide (GRP) is a mitogen for lung epithelial cells and initiates signaling through a G-protein-coupled receptor, gastrin-releasing peptide receptor (GRPR). Because GRPR transactivates the epidermal growth factor receptor (EGFR), we investigated induction by GRP of Akt, an EGFR-activated signaling pathway, and examined effects of GRP on viability of non-small cell lung carcinoma (NSCLC) cells exposed to the EGFR tyrosine kinase inhibitor gefitinib. GRP induced Akt activation primarily through c-Src-mediated transactivation of EGFR. Transfection of dominant-negative c-Src abolished GRP-induced EGFR and Akt activation. GRP induced release of amphiregulin, and pre-incubation with human amphiregulin neutralizing antibody eliminated GRP-induced Akt phosphorylation. Pretreatment with phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 completely blocked GRP-initiated Akt phosphorylation. These results suggest that GRP stimulates Akt activation primarily via c-Src activation, followed by extracellular release of the EGFR ligand amphiregulin, leading to the activation of EGFR and PI3K. Pretreatment of NSCLC cells with GRP resulted in an increase in the IC(50) of gefitinib of up to 9-fold; this protective effect was mimicked by the pretreatment of cells with amphiregulin and reversed by Akt or PI3K inhibition. GRP appears to rescue NSCLC cells exposed to gefitinib through release of amphiregulin and activation of the Akt pathway, suggesting GRPR and/or EGFR autocrine pathways in NSCLC cells may modulate therapeutic response to EGFR inhibitors.