Targeting receptor tyrosine kinase signalling in small cell lung cancer (SCLC): what have we learned so far?

Cancer brain metastasis: molecular mechanisms and therapeutic strategies

Brain metastases (BMs) are the most common intracranial tumors in adults and the major cause of cancer-related morbidity and mortality. The occurrence of BMs varies according to the type of primary tumors with most frequence in lung cancer, melanoma and breast cancer. Among of them, lung cancer has been reported to have a higher risk of BMs than other types of cancers with 40 ~ 50% of such patients will develop BMs during the course of disease. BMs lead to many neurological complications and result in a poor quality of life and short life span. Although the treatment strategies were improved for brain tumors in the past decades, the prognosis of BMs patients is grim. Poorly understanding of the molecular and cellular characteristics of BMs and the complicated interaction with brain microenvironment are the major reasons for the dismal prognosis of BM patients. Recent studies have enhanced understanding of the mechanisms of BMs. The newly identified potential therapeutic targets and the advanced therapeutic strategies have brought light for a better cure of BMs. In this review, we summarized the mechanisms of BMs during the metastatic course, the molecular and cellular landscapes of BMs, and the advances of novel drug delivery systems for overcoming the obstruction of blood-brain barrier (BBB). We further discussed the challenges of the emerging therapeutic strategies, such as synergistic approach of combining targeted therapy with immunotherapy, which will provide vital clues for realizing the precise and personalized medicine for BM patients in the future.

Umbilical cord mesenchymal stem cells and lung cancer: We should be hopeful or hopeless?

Lung cancer (LC) is one of the leading causes of cancer-caused death that possesses a poor prognosis and low survival rate worldwide. In general, LC is classified into small-cell (SCLC) and non-small-cell carcinoma (NSCLC) (involving 80% of patients). Although chemotherapy, radiotherapy, surgery, and molecular-targeted therapy are considered standard approaches for LC treatment, these options have low success with detrimental effects on the life quality of patients. Ergo, recommending treatment with maximum effectiveness and minimum side effects for LC patients has been a substantial challenge for researchers and clinicians in the present era. Recently, mesenchymal stem cells (MSCs)-based strategies have sparked much interest in preventing or treating numerous illnesses. These multipotent stem cells can be isolated from diverse sources, such as umbilical cord, bone marrow, and adipose tissue. Among these sources, umbilical cord mesenchymal stem cells (UC-MSCs) have been in the spotlight of MSCs-based therapies thanks to their considerable advantages, such as high proliferation ability, low immune reactions and tumorigenesis, and easiness in collection and isolation. Some experimental studies have investigated the functionality of intact UC-MSCs and extracellular vesicles, exosomes, and conditioned medium derived from UC-MSCs, as well as genetically engineered UC-MSCs. In this review, we aimed to highlight the influences of these UMSCs-based methods in LC treatment with cellular and molecular insights.

The Evolving Scenario of ES-SCLC Management: From Biology to New Cancer Therapeutics

Small cell lung cancer (SCLC) is an aggressive neuroendocrine carcinoma accounting for 15% of lung cancers with dismal survival outcomes. Minimal changes in therapy and prognosis have occurred in SCLC for the past four decades. Recent progress in the treatment of extensive-stage disease (ES-SCLC) has been marked by incorporating immune checkpoint inhibitors (ICIs) into platinum-based chemotherapy, leading to modest improvements. Moreover, few second-line-and-beyond treatment options are currently available. The main limitation for the molecular study of SCLC has been the scarcity of samples, because only very early diseases are treated with surgery and biopsies are not performed when the disease progresses. Despite all these difficulties, in recent years we have come to understand that SCLC is not a homogeneous disease. At the molecular level, in addition to the universal loss of retinoblastoma (RB) and TP53 genes, a recent large molecular study has identified other mutations that could serve as targets for therapy development or patient selection. In recent years, there has also been the identification of new genetic subtypes which have shown us how intertumor heterogeneity exists. Moreover, SCLC can also develop intratumoral heterogeneity linked mainly to the concept of cellular plasticity, mostly due to the development of resistance to therapies. The aim of this review is to quickly present the current standard of care of ES-SCLC, to focus on the molecular landscapes and subtypes of SCLC, subsequently present the most promising therapeutic strategies under investigation, and finally recap the future directions of ongoing clinical trials for this aggressive disease which still remains a challenge.

Orchestrating smart therapeutics to achieve optimal treatment in small cell lung cancer: recent progress and future directions

Small cell lung cancer (SCLC) is a recalcitrant malignancy with elusive mechanism of pathogenesis and dismal prognosis. Over the past decades, platinum-based chemotherapy has been the backbone treatment for SCLC. However, subsequent chemoresistance after initial effectiveness urges researchers to explore novel therapeutic targets of SCLC. Recent years have witnessed significant improvements in targeted therapy in SCLC. New molecular candidates such as Ataxia telangiectasia and RAD3-related protein (ATR), WEE1, checkpoint kinase 1 (CHK1) and poly-ADP-ribose polymerase (PARP) have shown promising therapeutic utility in SCLC. While immune checkpoint inhibitor (ICI) has emerged as an indispensable treatment modality for SCLC, approaches to boost efficacy and reduce toxicity as well as selection of reliable biomarkers for ICI in SCLC have remained elusive and warrants our further investigation. Given the increasing importance of precision medicine in SCLC, optimal subtyping of SCLC using multi-omics have gradually applied into clinical practice, which may identify more drug targets and better tailor treatment strategies to each individual patient. The present review summarizes recent progress and future directions in SCLC. In addition to the emerging new therapeutics, we also focus on the establishment of predictive model for early detection of SCLC. More importantly, we also propose a multi-dimensional model in the prognosis of SCLC to ultimately attain the goal of accurate treatment of SCLC.

Targeted Therapies in Small Cell Lung Cancer: From Old Failures to Novel Therapeutic Strategies

The clinical management of small cell lung cancer (SCLC) treatment remains a major challenge for thoracic oncologists, with very few therapeutic advances significantly impacting patients' survival. The recent introduction of immunotherapy in the clinical setting produced a marginal benefit for a limited subset of metastatic patients, while the therapeutic scenario for relapsing extended-disease small cell lung cancers (ED-SCLCs) remains almost deserted. Recent efforts clarified the molecular features of this disease, leading to the identification of key signalling pathways which may serve as potential targets for clinical use. Despite the large number of molecules tested and the numerous therapeutic failures, some targeted therapies have recently shown interesting preliminary results. In this review, we describe the main molecular pathways involved in SCLC development/progression and provide an updated summary of the targeted therapies currently under investigation in SCLC patients.

Microglia-Derived Spp1 Promotes Pathological Retinal Neovascularization via Activating Endothelial Kit/Akt/mTOR Signaling

Pathological retinal neovascularization (RNV) is the main character of ischemic ocular diseases, which causes severe visual impairments. Though retinal microglia are well acknowledged to play important roles in both physiological and pathological angiogenesis, the molecular mechanisms by which microglia communicates with endothelial cells (EC) remain unknown. In this study, using single-cell RNA sequencing, we revealed that the pro-inflammatory secreted protein Spp1 was the most upregulated gene in microglia in the mouse model of oxygen-induced retinopathy (OIR). Bioinformatic analysis showed that the expression of Spp1 in microglia was respectively regulated via nuclear factor-kappa B (NF-κB) and hypoxia-inducible factor 1α (HIF-1α) pathways, which was further confirmed through in vitro assays using BV2 microglia cell line. To mimic microglia-EC communication, the bEnd.3 endothelial cell line was cultured with conditional medium (CM) from BV2. We found that adding recombinant Spp1 to bEnd.3 as well as treating with hypoxic BV2 CM significantly enhanced EC proliferation and migration, while Spp1 neutralizing blocked those CM-induced effects. Moreover, RNA sequencing of BV2 CM-treated bEnd.3 revealed a significant downregulation of Kit, one of the type III tyrosine kinase receptors that plays a critical role in cell growth and activation. We further revealed that Spp1 increased phosphorylation and expression level of Akt/mTOR signaling cascade, which might account for its pro-angiogenic effects. Finally, we showed that intravitreal injection of Spp1 neutralizing antibody attenuated pathological RNV and improved visual function. Taken together, our work suggests that Spp1 mediates microglia-EC communication in RNV via activating endothelial Kit/Akt/mTOR signaling and is a potential target to treat ischemic ocular diseases.

Opportunities and obstacles of targeted therapy and immunotherapy in small cell lung cancer

Small cell lung cancer (SCLC) is an aggressive malignant tumour which accounts for approximately 13-15% of all newly diagnosed lung cancer cases. To date, platinum-based chemotherapy are still the first-line treatments for SCLC. However, chemotherapy resistance and systemic toxicity limit the long-term clinical outcome of first-line treatment in SCLC. Recent years, targeted therapy and immunotherapy have made great breakthrough in cancer therapy, and researchers aim to exploit both as a single agent or in combination with chemotherapy to improve the survival of SCLC patients, but limited effectiveness and the adverse events remain the major obstacles in the treatment of SCLC. To overcome these challenges for SCLC therapies, prevention and early diagnosis for this refractory disease is very important. At the same time, we should reveal more information about the pathogenesis of SCLC and the mechanism of drug resistance. Finally, new treatment strategies should also be taken into considerations, such as repurposing drug, optimising of targets, combination therapy strategies or prognostic biomarkers to enhance therapeutic effects and decrease the adverse events rates in SCLC patients. This article will review the molecular biology characteristics of SCLC and discuss the opportunities and obstacles of the current therapy for SCLC patients.

High Expression of NEK2 and PIM1, but Not PIM3, Is Linked to an Aggressive Phenotype of Bronchopulmonary Neuroendocrine Neoplasms

Dysregulations of the NEK2 and PIM1-3 kinase signaling axes have been implicated in the pathogenesis of several cancers, including those with a neuroendocrine phenotype. However, their impact on bronchopulmonary neuroendocrine neoplasms (BP-NENs) has not been investigated. The aim of this pilot study was to determine mRNA and protein levels of NEK2, PIM1, and PIM3 in a group of 49 patients with BP-NENs: 11 typical carcinoids, 5 atypical carcinoids, 11 large cell neuroendocrine carcinomas, 22 small cell lung carcinomas (SCLC). The expression was measured using TaqMan-based RT-PCR and immunohistochemistry. NEK2 and PIM1 mRNA levels were higher in the SCLC patients than in the other BP-NEN groups (p < 0.001). There was an association between NEK2 mRNA and protein expression (p = 0.023) and elevated NEK2 mRNA levels were related to reduced survival in BP-NEN patients (p = 0.015). Patients with higher PIM1 protein expression had also diminished survival comparing with those with weak or no PIM1 expression (p = 0.037). Elevated NEK2 and PIM1 expression were related to aggressive tumor phenotype and indirectly affected the overall survival of BP-NEN patients. Our pilot study supports the need for future investigation of the biological function of NEK2 and PIM1 in BP-NEN transformation to verify the clinical value of our findings.

Developing and Characterization of Chemically Modified RNA Aptamers for Targeting Wild Type and Mutated c-KIT Receptor Tyrosine Kinases

The c-KIT receptor represents an attractive target for cancer therapy. Aptamers are emerging as a new promising class of nucleic acid therapeutics. In this study, a conventional SELEX approach was applied against the kinase domain of a group of c-KIT proteins (c-KIT^WT, c-KIT^D816V, and c-KIT^D816H) to select aptamers from a random RNA pool that can bind to the kinase domain of each target with high affinity and can selectively interfere with their kinase activities. Interestingly, our data indicated that one candidate aptamer, called V15, can specifically inhibit the in vitro kinase activity of mutant c-KIT^D816V with an IC₅₀ value that is 9-fold more potent than the sunitinib drug tested under the same conditions. Another aptamer, named as H5/V36, showed the potential to distinguish between the c-KIT kinases by modulating the phosphorylation activity of each in a distinct mechanism of action and in a different potency.

Metabolic advantages and vulnerabilities in brain metastases

Metabolic adaptations permit tumor cells to metastasize to and thrive in the brain. Brain metastases continue to present clinical challenges due to rising incidence and resistance to current treatments. Therefore, elucidating altered metabolic pathways in brain metastases may provide new therapeutic targets for the treatment of aggressive disease. Due to the high demand for glucose in the brain, increased glycolytic activity is favored for energy production. Primary tumors that undergo Warburg-like metabolic reprogramming become suited to growth in the brain microenvironment. Indeed, elevated metabolism is a predictor of metastasis in many cancer subtypes. Specifically, metabolic alterations are seen in primary tumors that are associated with the formation of brain metastases, namely breast cancer, lung cancer, and melanoma. Because of this selective pressure, inhibitors of key metabolic factors may reduce tumor cell viability, thus exploiting metabolic pathways for cancer therapeutics. This review summarizes the metabolic advantages and vulnerabilities of brain metastases.

Novel Hybrid Phenotype Revealed in Small Cell Lung Cancer by a Transcription Factor Network Model That Can Explain Tumor Heterogeneity

Small cell lung cancer (SCLC) is a devastating disease due to its propensity for early invasion and refractory relapse after initial treatment response. Although these aggressive traits have been associated with phenotypic heterogeneity, our understanding of this association remains incomplete. To fill this knowledge gap, we inferred a set of 33 transcription factors (TF) associated with gene signatures of the known neuroendocrine/epithelial (NE) and non-neuroendocrine/mesenchymal-like (ML) SCLC phenotypes. The topology of this SCLC TF network was derived from prior knowledge and was simulated using Boolean modeling. These simulations predicted that the network settles into attractors, or TF expression patterns, that correlate with NE or ML phenotypes, suggesting that TF network dynamics underlie the emergence of heterogeneous SCLC phenotypes. However, several cell lines and patient tumor specimens failed to correlate with either the NE or ML attractors. By flow cytometry, single cells within these cell lines simultaneously expressed surface markers of both NE and ML differentiation, confirming the existence of a "hybrid" phenotype. Upon exposure to standard-of-care cytotoxic drugs or epigenetic modifiers, NE and ML cell populations converged toward the hybrid state, suggesting possible escape from treatment. Our findings indicate that SCLC phenotypic heterogeneity can be specified dynamically by attractor states of a master regulatory TF network. Thus, SCLC heterogeneity may be best understood as states within an epigenetic landscape. Understanding phenotypic transitions within this landscape may provide insights to clinical applications. Cancer Res; 77(5); 1063-74. ©2016 AACR.

Tyrosine Kinase Receptor Landscape in Lung Cancer: Therapeutical Implications

Lung cancer is a heterogeneous disease responsible for the most cases of cancer-related deaths. The majority of patients are clinically diagnosed at advanced stages, with a poor survival rate. For this reason, the identification of oncodrivers and novel biomarkers is decisive for the future clinical management of this pathology. The rise of high throughput technologies popularly referred to as “omics” has accelerated the discovery of new biomarkers and drivers for this pathology. Within them, tyrosine kinase receptors (TKRs) have proven to be of importance as diagnostic, prognostic, and predictive tools and, due to their molecular nature, as therapeutic targets. Along this review, the role of TKRs in the different lung cancer histologies, research on improvement of anti-TKR therapy, and the current approaches to manage anti-TKR resistance will be discussed.

Is the Canonical RAF/MEK/ERK Signaling Pathway a Therapeutic Target in SCLC?

The activity of the RAF/MEK/ERK signaling pathway is critical for the proliferation of normal and cancerous cells. Oncogenic mutations driving the development of lung adenocarcinoma often activate this signaling pathway. In contrast, pathway activity levels and their biological roles are not well established in small cell lung cancer (SCLC), a fast-growing neuroendocrine lung cancer subtype. Here we discuss the function of the RAF/MEK/ERK kinase pathway and the mechanisms leading to its activation in SCLC cells. In particular, we argue that activation of this pathway may be beneficial to the survival, proliferation, and spread of SCLC cells in response to multiple stimuli. We also consider evidence that high levels of RAF/MEK/ERK pathway activity may be detrimental to SCLC tumors, including in part by interfering with their neuroendocrine fate. On the basis of these observations, we examined when small molecules targeting kinases in the RAF/MEK/ERK pathway may be useful therapeutically in patients with SCLC, including in combination with other therapeutic agents.

Label-Free Raman Spectroscopic Imaging Monitors the Integral Physiologically Relevant Drug Responses in Cancer Cells

Predictions about the cellular efficacy of drugs tested in vitro are usually based on the measured responses of a few proteins or signal transduction pathways. However, cellular proteins are highly coupled in networks, and observations of single proteins may not adequately reflect the in vivo cellular response to drugs. This might explain some large discrepancies between in vitro drug studies and drug responses observed in patients. We present a novel in vitro marker-free approach that enables detection of cellular responses to a drug. We use Raman spectral imaging to measure the effect of the epidermal growth factor receptor (EGFR) inhibitor panitumumab on cell lines expressing wild-type Kirsten-Ras (K-Ras) and oncogenic K-Ras mutations. Oncogenic K-Ras mutation blocks the response to anti-EGFR therapy in patients, but this effect is not readily observed in vitro. The Raman studies detect large panitumumab-induced differences in vitro in cells harboring wild-type K-Ras as seen in A in red but not in cells with K-Ras mutations as seen in B; these studies reflect the observed patient outcomes. However, the effect is not observed when extracellular-signal-regulated kinase phosphorylation is monitored. The Raman spectra show for cells with wild-type K-Ras alterations based on the responses to panitumumab. The subcellular component with the largest spectral response to panitumumab was lipid droplets, but this effect was not observed when cells harbored K-Ras mutations. This study develops a noninvasive, label-free, in vitro vibrational spectroscopic test to determine the integral physiologically relevant drug response in cell lines. This approach opens a new field of patient-centered drug testing that could deliver superior patient therapies.

The DNA Methyltransferase DNMT1 and Tyrosine-Protein Kinase KIT Cooperatively Promote Resistance to 5-Aza-2'-deoxycytidine (Decitabine) and Midostaurin (PKC412) in Lung Cancer Cells

Lung cancer cells are sensitive to 5-aza-2'-deoxycytidine (decitabine) or midostaurin (PKC412), because decitabine restores the expression of methylation-silenced tumor suppressor genes, whereas PKC412 inhibits hyperactive kinase signaling, which is essential for cancer cell growth. Here, we demonstrated that resistance to decitabine (decitabine(R)) or PKC412 (PKC412(R)) eventually results from simultaneously remethylated DNA and reactivated kinase cascades. Indeed, both decitabine(R) and PKC412(R) displayed the up-regulation of DNA methyltransferase DNMT1 and tyrosine-protein kinase KIT, the enhanced phosphorylation of KIT and its downstream effectors, and the increased global and gene-specific DNA methylation with the down-regulation of tumor suppressor gene epithelial cadherin CDH1. Interestingly, decitabine(R) and PKC412(R) had higher capability of colony formation and wound healing than parental cells in vitro, which were attributed to the hyperactive DNMT1 or KIT, because inactivation of KIT or DNMT1 reciprocally blocked decitabine(R) or PKC412(R) cell proliferation. Further, DNMT1 knockdown sensitized PKC412(R) cells to PKC412; conversely, KIT depletion synergized with decitabine in eliminating decitabine(R). Importantly, when engrafted into nude mice, decitabine(R) and PKC412(R) had faster proliferation with stronger tumorigenicity that was caused by the reactivated KIT kinase signaling and further CDH1 silencing. These findings identify functional cross-talk between KIT and DNMT1 in the development of drug resistance, implying the reciprocal targeting of protein kinases and DNA methyltransferases as an essential strategy for durable responses in lung cancer.

Discovery of novel non-ATP competitive FGFR1 inhibitors and evaluation of their anti-tumor activity in non-small cell lung cancer in vitro and in vivo

Accumulating evidence suggests that high expression of FGFR1 is closely related to the development of lung cancer especially in non-small cell lung cancers (NSCLC), to which non-ATP competitive inhibitors represent an effective therapeutical approach due to their good specificity. Herein, a series of NDGA analogues with the framework of bisaryl-1,4-dien-3-one as novel FGFR1 inhibitors have been designed and screened. Among them Aea4 and Aea25 showed strong FGFR1 ‵inhibition and high selectivity over other receptor kinases. The kinase inhibitory assay in different ATP concentrations and computer-assistant molecular docking showed that the FGFR1 inhibition mode of both Aea4 and Aea25 was non-ATP-competitive. The in vitro and in vivo study on anticancer efficacy of Aea4 and Aea25 against non-small cell lung cancer involves inhibition of cell proliferation, apoptosis induction and cell cycle arrest with no toxicity. Thus, these two novel non-ATP competitive inhibitors derived from NDGA may have a great therapeutic potential in the treatment of NSCLC. This work also provides a structural lead for the design of new non-ATP-competitive FGFR1 inhibitors.

Targeted therapies for small cell lung cancer: Where do we stand?

Small cell lung cancer (SCLC) accounts for 15% of lung cancer cases and is associated with a dismal prognosis. Standard therapeutic regimens have been improved over the past decades, but without a major impact on patient survival. The development of targeted therapies based on a better understanding of the molecular basis of the disease is urgently needed. At the genetic level, SCLC appears very heterogenous, although somatic mutations targeting classical oncogenes and tumor suppressors have been reported. SCLC also possesses somatic mutations in many other cancer genes, including transcription factors, enzymes involved in chromatin modification, receptor tyrosine kinases and their downstream signaling components. Several avenues have been explored to develop targeted therapies for SCLC. So far, however, there has been limited success with these targeted approaches in clinical trials. Further progress in the optimization of targeted therapies for SCLC will require the development of more personalized approaches for the patients.

Formononetin inhibits enterovirus 71 replication by regulating COX- 2/PGE₂ expression

Background

The activation of ERK, p38 and JNK signal cascade in host cells has been demonstrated to up-regulate of enterovirus 71 (EV71)-induced cyclooxygenase-2 (COX-2)/ prostaglandins E₂ (PGE₂) expression which is essential for viral replication. So, we want to know whether a compound can inhibit EV71 infection by suppressing COX-2/PGE₂ expression.

Methods

The antiviral effect of formononetin was determined by cytopathic effect (CPE) assay and the time course assays. The influence of formononetin for EV71 replication was determined by immunofluorescence assay, western blotting assay and qRT-PCR assay. The mechanism of the antiviral activity of formononetin was determined by western blotting assay and ELISA assay.

Results

Formononetin could reduce EV71 RNA and protein synthesis in a dose-dependent manner. The time course assays showed that formononetin displayed significant antiviral activity both before (24 or 12 h) and after (0–6 h) EV71 inoculation in SK-N-SH cells. Formononetin was also able to prevent EV71-induced cytopathic effect (CPE) and suppress the activation of ERK, p38 and JNK signal pathways. Furthermore, formononetin could suppress the EV71-induced COX-2/PGE₂ expression. Also, formononetin exhibited similar antiviral activities against other members of Picornaviridae including coxsackievirus B2 (CVB2), coxsackievirus B3 (CVB3) and coxsackievirus B6 (CVB6).

Conclusions

Formononetin could inhibit EV71-induced COX-2 expression and PGE₂ production via MAPKs pathway including ERK, p38 and JNK. Formononetin exhibited antiviral activities against some members of Picornaviridae. These findings suggest that formononetin could be a potential lead or supplement for the development of new anti-EV71 agents in the future.

Recent advances in histogenesis research of lung neuroendocrine cancers: Evidence obtained from functional analyses of primitive neural/neuroendocrine cell-specific transcription factors

Small cell carcinoma (SmCC) and large cell neuroendocrine carcinoma (LENEC) are categorized as neuroendocrine cancers (NECs) of the lung and have extremely poor prognoses. The lack of an effective therapeutic strategy against SmCC and LCNEC is a serious issue. Because the regulation of the cellular phenotype is complicated by the actions of various transcription factors, investigations into the function of neural/neuroendocrine cell-specific transcription factors are important for elucidating the cellular characteristics and histogenesis of SmCC and LCNEC and for establishing innovative therapeutic strategies against them. In this review, the functions of ASCL1, NeuroD1, REST, TTF1, and class III/IV POU, that are specifically and highly expressed in lung NECs, are introduced. These transcription factors transactivate and/or transrepress various genes and are involved in neural progenitor phenotyping, neuroendocrine and stem cell marker expression, and epithelial-to-mesenchymal transition. Based on the evidence that certain carcinoids express ASCL1, NeuroD1, TTF1, and class III/IV POU and that lung NECs can develop from non-NE cells/non-NEC cells, the relationships among lung NECs, carcinoid tumors, and non-NECs are discussed. Finally, a model of the histogenesis of lung NECs in view of similarities in the expression of primitive neural/neuroendocrine cell-specific transcription factors is proposed.

Overcoming chemoresistance of small-cell lung cancer through stepwise HER2-targeted antibody-dependent cell-mediated cytotoxicity and VEGF-targeted antiangiogenesis

Small-cell lung cancer (SCLC) easily recurs with a multidrug resistant phenotype. However, standard therapeutic strategies for relapsed SCLC remain unestablished. We found that human epidermal growth factor receptor 2 (HER2) is not only expressed in pretreated human SCLC specimens, but is also upregulated when HER2-positive SCLC cells acquire chemoresistance. Trastuzumab induced differential levels of antibody-dependent cell-mediated cytotoxicity (ADCC) to HER2-positive SCLC cells. Furthermore, as a mechanism of the differential levels of ADCC, we have revealed that coexpression of intracellular adhesion molecule (ICAM)-1 on SCLC cells is essential to facilitate and accelerate the trastuzumab-mediated ADCC. Although SN-38-resistant SCLC cells lacking ICAM-1 expression were still refractory to trastuzumab, their in vivo growth was significantly suppressed by bevacizumab treatment due to dependence on their distinctive and abundant production of vascular endothelial growth factor. Collectively, stepwise treatment with trastuzumab and bevacizumab is promising for the treatment of chemoresistant SCLC.

Detection of c-kit mutational status in small-cell lung cancer in a Chinese cohort

BACKGROUND

Overexpression of KIT (CD117), a tyrosine kinase receptor, and its natural ligand, stem cell factor, are found in small-cell lung cancer (SCLC). Somatic mutations of the proto-oncogene c-kit constitutively activate KIT expression in a ligand-independent way. To explore the clinical value of the c-kit mutation as a potential target for therapy with tyrosine kinase inhibitors, the c-kit mutational status and KIT expression in tumors from Chinese patients with SCLC were analyzed.

METHODS

Using 107 paraffin-embedded SCLC tumor specimens, c-kit exons 9, 11, 13, and 17 were analyzed for mutations by polymerase chain reaction and direct sequencing.

RESULTS

There were no activating mutations in exons 9, 11, 13, or 17. However, a point mutation in intron 16 (81240 G>A) was found in 11 out of the 107 samples (10.3%), of which the majority were limited-stage SCLC (10/11, 90.9%). Immunohistochemical staining of tumors harboring the c-kit point mutation using the anti-CD117 antibody showed that the mutation status was not associated with the expression of KIT.

CONCLUSION

These findings indicate that the incidence and the types of c-kit mutations in SCLC tumors found in Chinese are different from those of the Caucasian population. Nevertheless, c-kit mutations are similarly rare in both groups, implying that they may not be suitable targets for c-kit-based tyrosine kinase inhibitors.

Structural and functional properties of platelet-derived growth factor and stem cell factor receptors

The receptors for platelet-derived growth factor (PDGF) and stem cell factor (SCF) are members of the type III class of PTK receptors, which are characterized by five Ig-like domains extracellularly and a split kinase domain intracellularly. The receptors are activated by ligand-induced dimerization, leading to autophosphorylation on specific tyrosine residues. Thereby the kinase activities of the receptors are activated and docking sites for downstream SH2 domain signal transduction molecules are created; activation of these pathways promotes cell growth, survival, and migration. These receptors mediate important signals during the embryonal development, and control tissue homeostasis in the adult. Their overactivity is seen in malignancies and other diseases involving excessive cell proliferation, such as atherosclerosis and fibrotic diseases. In cancer, mutations of PDGF and SCF receptors-including gene fusions, point mutations, and amplifications-drive subpopulations of certain malignancies, such as gastrointestinal stromal tumors, chronic myelomonocytic leukemia, hypereosinophilic syndrome, glioblastoma, acute myeloid leukemia, mastocytosis, and melanoma.

Therapeutic efficacy of c-kit-targeted radioimmunotherapy using 90Y-labeled anti-c-kit antibodies in a mouse model of small cell lung cancer

Small cell lung cancer (SCLC) is an aggressive tumor and prognosis remains poor. Therefore, the development of more effective therapy is needed. We previously reported that high levels of an anti-c-kit antibody (12A8) accumulated in SCLC xenografts. In the present study, we evaluated the efficacy of two antibodies (12A8 and 67A2) for radioimmunotherapy (RIT) of an SCLC mouse model by labeling with the (90)Y isotope.

METHODS

(111)In- or (125)I-labeled antibodies were evaluated in vitro by cell binding, competitive inhibition and cellular internalization assays in c-kit-expressing SY cells and in vivo by biodistribution in SY-bearing mice. Therapeutic efficacy of (90)Y-labeled antibodies was evaluated in SY-bearing mice upto day 28 and histological analysis was conducted at day 7.

RESULTS

[(111)In]12A8 and [(111)In]67A2 specifically bound to SY cells with high affinity (8.0 and 1.9 nM, respectively). 67A2 was internalized similar to 12A8. High levels of [(111)In]12A8 and [(111)In]67A2 accumulated in tumors, but not in major organs. [(111)In]67A2 uptake by the tumor was 1.7 times higher than for [(111)In]12A8. [(90)Y]12A8, but not [(90)Y]67A2, suppressed tumor growth in a dose-dependent manner. Tumors treated with 3.7 MBq of [(90)Y]12A8, and 1.85 and 3.7 MBq of [(90)Y]67A2 (absorbed doses were 21.0, 18.0 and 35.9 Gy, respectively) almost completely disappeared approximately 2 weeks after injection, and regrowth was not observed except for in one mouse treated with 1.85 MBq [(90)Y]67A2. The area of necrosis and fibrosis increased depending on the RIT effect. Apoptotic cell numbers increased with increased doses of [(90)Y]12A8, whereas no dose-dependent increase was observed following [(90)Y]67A2 treatment. Body weight was temporarily reduced but all mice tolerated the RIT experiments well.

CONCLUSION

Treatment with [(90)Y]12A8 and [(90)Y]67A2 achieved a complete therapeutic response when SY tumors received an absorbed dose greater than 18 Gy and thus are promising RIT agents for metastatic SCLC cells at distant sites.

Targeting the phosphoinositide 3-kinase p110-α isoform impairs cell proliferation, survival, and tumor growth in small cell lung cancer

PURPOSE

The phosphoinositide 3-kinase (PI3K) pathway is fundamental for cell proliferation and survival and is frequently altered and activated in neoplasia, including carcinomas of the lung. In this study, we investigated the potential of targeting the catalytic class I(A) PI3K isoforms in small cell lung cancer (SCLC), which is the most aggressive of all lung cancer types.

EXPERIMENTAL DESIGN

The expression of PI3K isoforms in patient specimens was analyzed. The effects on SCLC cell survival and downstream signaling were determined following PI3K isoform inhibition by selective inhibitors or downregulation by siRNA.

RESULTS

Overexpression of the PI3K isoforms p110-α and p110-β and the antiapoptotic protein Bcl-2 was shown by immunohistochemistry in primary SCLC tissue samples. Targeting the PI3K p110-α with RNA interference or selective pharmacologic inhibitors resulted in strongly affected cell proliferation of SCLC cells in vitro and in vivo, whereas targeting p110-β was less effective. Inhibition of p110-α also resulted in increased apoptosis and autophagy, which was accompanied by decreased phosphorylation of Akt and components of the mTOR pathway, such as the ribosomal S6 protein, and the eukaryotic translation initiation factor 4E-binding protein 1. A DNA microarray analysis revealed that p110-α inhibition profoundly affected the balance of pro- and antiapoptotic Bcl-2 family proteins. Finally, p110-α inhibition led to impaired SCLC tumor formation and vascularization in vivo.

CONCLUSION

Together our data show the key involvement of the PI3K isoform p110-α in the regulation of multiple tumor-promoting processes in SCLC.

The role of insulin C-peptide in the coevolution analyses of the insulin signaling pathway: a hint for its functions

As the linker between the A chain and B chain of proinsulin, C-peptide displays high variability in length and amino acid composition, and has been considered as an inert byproduct of insulin synthesis and processing for many years. Recent studies have suggested that C-peptide can act as a bioactive hormone, exerting various biological effects on the pathophysiology and treatment of diabetes. In this study, we analyzed the coevolution of insulin molecules among vertebrates, aiming at exploring the evolutionary characteristics of insulin molecule, especially the C-peptide. We also calculated the correlations of evolutionary rates between the insulin and the insulin receptor (IR) sequences as well as the domain-domain pairs of the ligand and receptor by the mirrortree method. The results revealed distinctive features of C-peptide in insulin intramolecular coevolution and correlated residue substitutions, which partly supported the idea that C-peptide can act as a bioactive hormone, with significant sequence features, as well as a linker assisting the formation of mature insulin during synthesis. Interestingly, the evolution of C-peptide exerted the highest correlation with that of the insulin receptor and its ligand binding domain (LBD), implying a potential relationship with the insulin signaling pathway.

Stem Cell Factor Receptor/c-Kit: From Basic Science to Clinical Implications

Stem cell factor (SCF) is a dimeric molecule that exerts its biological functions by binding to and activating the receptor tyrosine kinase c-Kit. Activation of c-Kit leads to its autophosphorylation and initiation of signal transduction. Signaling proteins are recruited to activated c-Kit by certain interaction domains (e.g., SH2 and PTB) that specifically bind to phosphorylated tyrosine residues in the intracellular region of c-Kit. Activation of c-Kit signaling has been found to mediate cell survival, migration, and proliferation depending on the cell type. Signaling from c-Kit is crucial for normal hematopoiesis, pigmentation, fertility, gut movement, and some aspects of the nervous system. Deregulated c-Kit kinase activity has been found in a number of pathological conditions, including cancer and allergy. The observation that gain-of-function mutations in c-Kit can promote tumor formation and progression has stimulated the development of therapeutics agents targeting this receptor, e.g., the clinically used inhibitor imatinib mesylate. Also other clinically used multiselective kinase inhibitors, for instance, sorafenib and sunitinib, have c-Kit included in their range of targets. Furthermore, loss-of-function mutations in c-Kit have been observed and shown to give rise to a condition called piebaldism. This review provides a summary of our current knowledge regarding structural and functional aspects of c-Kit signaling both under normal and pathological conditions, as well as advances in the development of low-molecular-weight molecules inhibiting c-Kit function.

The mTOR pathway in lung cancer and implications for therapy and biomarker analysis

Mammalian target of rapamycin (mTOR) is a serine/threonine kinase that functions as a key regulatory protein in normal cell growth, survival, metabolism, development, and angiogenic pathways. Deregulation of these processes is a required hallmark of cancer, and dysregulation of mTOR signaling frequently occurs in a wide variety of malignancies, including lung cancer. Targeting of mTOR is thus an attractive strategy in the development of therapeutic agents against lung cancer. In this review, the mTOR-signaling pathway is described, highlighting opportunities for therapeutic intervention and biomarker analysis, and clinical trials in lung cancer including both non-small cell lung cancer and small cell lung cancer.

The DNA methylation landscape of small cell lung cancer suggests a differentiation defect of neuroendocrine cells

Small cell lung cancer (SCLC) is a disease characterized by aggressive clinical behavior and lack of effective therapy. Owing to its tendency for early dissemination, only a third of patients have limited-stage disease at the time of diagnosis. SCLC is thought to derive from pulmonary neuroendocrine cells. Although several molecular abnormalities in SCLC have been described, there are relatively few studies on epigenetic alterations in this type of tumor. Here, we have used methylation profiling with the methylated-CpG island recovery assay in combination with microarrays and conducted the first genome-scale analysis of methylation changes that occur in primary SCLC and SCLC cell lines. Among the hundreds of tumor-specifically methylated genes discovered, we identified 73 gene targets that are methylated in >77% of primary SCLC tumors, most of which have never been linked to aberrant methylation in tumors. These methylated targets have potential for biomarker development for early detection and therapeutic management of SCLC. SCLC cell lines had a greater number of hypermethylated genes than primary tumors. Gene ontology analysis indicated a significant enrichment of methylated genes functioning as transcription factors and in processes of neuronal differentiation. Motif analysis of tumor-specific methylated regions identified enrichment of binding sites for several neural cell fate-specifying transcription factors including NEUROD1, HAND1, ZNF423 and REST. We hypothesize that two potential mechanisms, loss of cell fate-determining transcription factors by methylation of their promoters and functional inactivation of their corresponding genomic-binding sites by DNA methylation, can promote a differentiation defect of neuroendocrine cells thus enhancing the ability of tumor progenitor cells to transition toward SCLC.

Molecular and cellular biology of neuroendocrine lung tumors: evidence for separate biological entities

Pulmonary neuroendocrine tumors (NETs) are traditionally described as comprising a spectrum of neoplasms, ranging from low grade typical carcinoids (TCs) via the intermediate grade atypical carcinoids (ACs) to the highly malignant small cell lung cancers (SCLCs) and large cell neuroendocrine carcinomas (LCNECs). Recent data, however, suggests that two categories can be distinguished on basis of molecular and clinical data, i.e. the high grade neuroendocrine (NE) carcinomas and the carcinoid tumors. Bronchial carcinoids and SCLCs may originate from the same pulmonary NE precursor cells, but a precursor lesion has only been observed in association with carcinoids, termed diffuse idiopathic pulmonary neuroendocrine cell hyperplasia. The occurrence of mixed tumors exclusively comprising high grade NE carcinomas also supports a different carcinogenesis for these two groups. Histopathologically, high grade NE lung tumors are characterized by high mitotic and proliferative indices, while carcinoids are defined by maximally 10 mitoses per 2mm(2) (10 high-power fields) and rarely have Ki67-proliferative indices over 10%. High grade NE carcinomas are chemosensitive tumors, although they usually relapse. Surgery is often not an option due to extensive disease at presentation and early metastasis, especially in SCLC. Conversely, carcinoids are often insensitive to chemo- and radiation therapy, but cure can usually be achieved by surgery. A meta-analysis of comparative genomic hybridization studies performed for this review, as well as gene expression profiling data indicates separate clustering of carcinoids and carcinomas. Chromosomal aberrations are much more frequent in carcinomas, except for deletion of 11q, which is involved in the whole spectrum of NE lung tumors. Deletions of chromosome 3p are rare in carcinoids but are a hallmark of the high grade pulmonary NE carcinomas. On the contrary, mutations of the multiple endocrine neoplasia type 1 (MEN1) gene are restricted to carcinoid tumors. Many of the differences between carcinoids and high grade lung NETs can be ascribed to tobacco consumption, which is strongly linked to the occurrence of high grade NE carcinomas. Smoking causes p53 mutations, very frequently present in SCLCs and LCNECs, but rarely in carcinoids. It further results in other early genetic events in SCLCs and LCNECs, such as 3p and 17p deletions. Smoking induces downregulation of E-cadherin and associated epithelial to mesenchymal transition. Also, high grade lung NETs display higher frequencies of aberrations of the Rb pathway, and of the intrinsic and extrinsic apoptotic routes. Carcinoid biology on the other hand is not depending on cigarette smoke intake but rather characterized by aberrations of other specific genetic events, probably including Menin or its targets and interaction partners. This results in a gradual evolution, most likely from proliferating pulmonary NE cells via hyperplasia and tumorlets towards classical carcinoid tumors. We conclude that carcinoids and high grade NE lung carcinomas are separate biological entities and do not comprise one spectrum of pulmonary NETs. This implies the need to reconsider both diagnostic as well as therapeutic approaches for these different groups of malignancies.

Japanese encephalitis virus induces matrix metalloproteinase-9 expression via a ROS/c-Src/PDGFR/PI3K/Akt/MAPKs-dependent AP-1 pathway in rat brain astrocytes

BACKGROUND

Japanese encephalitis virus (JEV) infection is a major cause of acute encephalopathy in children, which destroys central nervous system (CNS) cells, including astrocytes and neurons. Matrix metalloproteinase (MMP)-9 has been shown to degrade components of the basal lamina, leading to disruption of the blood-brain barrier (BBB) and to contribute to neuroinflammatory responses in many neurological diseases. However, the detailed mechanisms of JEV-induced MMP-9 expression in rat brain astrocytes (RBA-1 cells) are largely unclear.

METHODS

In this study, the effect of JEV on expression of MMP-9 was determined by gelatin zymography, western blot analysis, RT-PCR, and promoter assay. The involvement of AP-1 (c-Jun and c-Fos), c-Src, PDGFR, PI3K/Akt, and MAPKs in these responses were investigated by using the selective pharmacological inhibitors and transfection with siRNAs.

RESULTS

Here, we demonstrate that JEV induces expression of pro-form MMP-9 via ROS/c-Src/PDGFR/PI3K/Akt/MAPKs-dependent, AP-1 activation in RBA-1 cells. JEV-induced MMP-9 expression and promoter activity were inhibited by pretreatment with inhibitors of AP-1 (tanshinone), c-Src (PP1), PDGFR (AG1296), and PI3K (LY294002), and by transfection with siRNAs of c-Jun, c-Fos, PDGFR, and Akt. Moreover, JEV-stimulated AP-1 activation was inhibited by pretreatment with the inhibitors of c-Src, PDGFR, PI3K, and MAPKs.

CONCLUSION

From these results, we conclude that JEV activates the ROS/c-Src/PDGFR/PI3K/Akt/MAPKs pathway, which in turn triggers AP-1 activation and ultimately induces MMP-9 expression in RBA-1 cells. These findings concerning JEV-induced MMP-9 expression in RBA-1 cells imply that JEV might play an important role in CNS inflammation and diseases.

Enterovirus 71 modulates a COX-2/PGE2/cAMP-dependent viral replication in human neuroblastoma cells: role of the c-Src/EGFR/p42/p44 MAPK/CREB signaling pathway

Enterovirus 71 (EV71) has been shown to induce cyclooxygenase‐2 (COX‐2) expression in human neuroblastoma SK‐N‐SH cells through the action of MAPKs, NF‐κB, and AP‐1. On the other hand, the transcription factor CREB has also been implicated in the expression of COX‐2 in other cell lines. Here, we report that EV71‐induced COX‐2 expression and PGE₂ production were both inhibited by pretreatment with the PKA inhibitor H89 or by transfection with CREB siRNA. In addition, EV71‐induced COX‐2 expression and c‐Src/EGFR phosphorylation were both attenuated by transfection with c‐Src siRNA or pretreatment with the inhibitors of c‐Src (PP1) or EGF receptor (EGFR) (AG1478 and EGFR‐neutralizing antibody). We also observed that EV71‐induced p42/p44 MAPK phosphorylation was decreased following pretreatment with AG1478. Moreover, EV71‐induced COX‐2 expression was blocked by pretreatment with the p300 inhibitor GR343 or by transfection with p300 siRNA. Using immunoprecipitation and chromatin immunoprecipitation assays, we observed that EV71 stimulated the association of CREB and p300 with the COX‐2 promoter region. Notably, we also demonstrated that EV71‐induced COX‐2 expression and PGE₂ production promoted viral replication via cAMP signaling. In summary, this study demonstrates that EV71 activates the c‐Src/EGFR/p42/p44 MAPK pathway in human SK‐N‐SH cell, which leads to the activation of CREB/p300, and stimulates COX‐2 expression and PGE₂ release. J. Cell. Biochem. 112: 559–570, 2011. © 2010 Wiley‐Liss, Inc.

Signalling pathways and the host-parasite relationship: putative targets for control interventions against schistosomiasis: signalling pathways and future anti-schistosome therapies

A better understanding of how schistosomes exploit host nutrients, neuro-endocrine hormones and signalling pathways for growth, development and maturation may provide new insights for improved interventions in the control of schistosomiasis. This paper describes recent advances in the identification and characterisation of schistosome tyrosine kinase and signalling pathways. It discusses the potential intervention value of insulin signalling, which may play an important role in glucose uptake and carbohydrate metabolism in schistosomes, providing the nutrients essential for parasite growth, development and, notably, female fecundity. Significant progress has also been made in the characterisation of other schistosome growth factor receptors, such as transforming growth factor beta receptor and epidermal growth factor receptor, and in our understanding of their roles in the host-parasite molecular dialogue and parasite development. The use of parasite signal transduction components as novel vaccine or drug targets may prove invaluable in prevention, treatment and control strategies to combat schistosomiasis.

Dual inhibition of EGFR and mTOR pathways in small cell lung cancer

Background:

In this report we investigated the combination of epidermal growth factor receptor (EGFR) and mammalian target of rapamycin (mTOR) pathway inhibition as a possible new therapeutic strategy for small cell lung cancer (SCLC).

Methods:

EGFR, p-AKT, p-ERK, p-mTOR and p-p70s6K protein expressions were studied by immunohistochemistry in 107 small cell lung carcinomas and correlated with clinicopathological parameters. Cells of SCLC were treated with erlotinib±RAD001 and analysed for cell viability, proliferation, autophagy, and pathway regulation.

Results:

Epidermal growth factor receptor, p-AKT, p-ERK, p-mTOR, and p-p70s6K were expressed in 37, 24, 13, 55 and 91% of the tumour specimens of all SCLC patients, respectively, and were not associated with disease-free or overall survival. The expression of EGFR was lower in neoadjuvant-treated patients (P=0.038); mTOR pathway activation was higher in the early stages of disease (P=0.048). Coexpression of EGFR/p-mTOR/p-p70s6K was observed in 28% of all patients . EGFR immunoreactivity was associated with p-ERK and p-mTOR expression (P=0.02 and P=0.0001); p-mTOR immunoreactivity was associated with p-p70s6K expression (P=0.001). Tumour cells comprised a functional EGFR, no activating mutations in exons 18–21, and resistance to RAD001 monotherapy. We found synergistic effects of erlotinib and RAD001 combination therapy on the molecular level, cell viability, proliferation and autophagy.

Conclusions:

The combined inhibition of EGFR/mTOR pathways could be a promising approach to treat SCLC.

EV71 induces COX-2 expression via c-Src/PDGFR/PI3K/Akt/p42/p44 MAPK/AP-1 and NF-kappaB in rat brain astrocytes

Enterovirus 71 (EV71) induces the expression of cyclooxgenase (COX)-2 served as a major neurotoxic factor in CNS injury. However, the mechanisms underlying EV71-initiated intracellular signaling pathways leading to COX-2 expression remain unknown. Therefore, we investigated the mechanisms underlying EV71-induced COX-2 expression and prostaglandin E(2) (PGE(2)) production in rat brain astrocytes (RBA)-1, determined by Western blotting, RT-PCR, and promoter assay. Here, we reported that EV71-induced COX-2 expression and PGE(2) production were attenuated by pretreatment with the inhibitors of c-Src (PP1), PDGFR (AG1296), PI3K (Wortmannin), MEK1/2 (PD98059), NF-kappaB (helenalin), and AP-1 (Tanshinone) and transfection with shRNA or siRNA of c-Src, PDGFR, p85, c-Jun, c-Fos, ERK1, or ERK2. We further observed that EV71-induced activation of Akt and p42/p44 MAPK were mediated via c-Src and PDGFR. Pretreatment with PP1 attenuated EV71-stimulated phosphorylation of Src, PDGFR, Akt, and p42/p44 MAPK. Inhibition of PI3K by Wortmannin attenuated EV71-induced Akt and p42/p44 MAPK phosphorylation, but had no effect on PDGFR phosphorylation, suggesting that PDGFR is an upstream and p42/p44 MAPK is a downstream component of PI3K/Akt in these responses. EV71-stimulated NF-kappaB translocation from the cytoplasm to the nucleus, IkappaBalpha degradation and NF-kappaB promoter activity were attenuated by pretreatment with helenalin, but not AG1296, Wortmannin, and PD98059. EV71-induced c-Jun mRNA expression was attenuated by pretreatment with PD98059, AG1296, or Wortmannin. These results demonstrate that in RBA-1 cells, EV71-induced COX-2 expression associated with PGE(2) production is mediated through activation of c-Src/PDGFR/PI3K/Akt/p42/p44 MAPK to initiate the expression of AP-1.

Merkel cell carcinoma: lack of KIT positivity and implications for the use of imatinib mesylate

The large variability (7% to 100%) in previously reported rates of receptor tyrosine kinase KIT expression in Merkel cell carcinoma (MCC) may be owing to the use of heat-induced epitope retrieval. High frequency of reported KIT reactivity by immunohistochemistry (IHC) in part prompted the initiation of a phase 2 clinical trial of imatinib mesylate (Gleevec, Novartis Pharmaceuticals, East Hanover, NJ) for the treatment of advanced MCC. Our experience has been that a small number of MCCs (12.5%) are positive for KIT by IHC. We also found a higher rate of apparently KIT-positive MCCs (75%) using heat-induced epitope retrieval. Our anecdotal experience with the use of imatinib mesylate has been disappointing. As IHC detection of KIT expression does not correlate with the presence of KIT-activating mutations, protein expression as tested by IHC should not be used to determine if patients would respond to imatinib mesylate. Indeed, our review of the literature and the apparent lack of efficacy of imatinib mesylate for MCC in a recent phase 2 trial suggest a minor role for KIT signaling in MCC tumorigenesis.

Characterizing the effects of the juxtamembrane domain on vascular endothelial growth factor receptor-2 enzymatic activity, autophosphorylation, and inhibition by axitinib

The catalytic domains of protein kinases are commonly treated as independent modular units with distinct biological functions. Here, the interactions between the catalytic and juxtamembrane domains of VEGFR2 are studied. Highly purified preparations of the receptor tyrosine kinase VEGFR2 catalytic domain without (VEGFR2-CD) and with (VEGFR2-CD/JM) the juxtamembrane (JM) domain were characterized by kinetic, biophysical, and structural methods. Although the catalytic parameters for both constructs were similar, the autophosphorylation rate of VEGFR2-CD/JM was substantially faster than VEGFR2-CD. The first event in the autophosphorylation reaction was phosphorylation of JM residue Y801 followed by phosphorylation of activation loop residues in the CD. The rates of activation loop autophosphorylation for the two constructs were determined to be similar. The autophosphorylation rate of Y801 was invariant on enzyme concentration, which is consistent with an intramolecular reaction. In addition, the first biochemical characterization of the advanced clinical compound axitinib is reported. Axitinib was found to have 40-fold enhanced biochemical potency toward VEGFR2-CD/JM (K(i) = 28 pM) compared to VEGFR2-CD, which correlates better with cellular potency. Calorimetric studies, including a novel ITC compound displacement method, confirmed the potency and provided insight into the thermodynamic origin of the potency differences. A structural model for the VEGFR2-CD/JM is proposed based on the experimental findings reported here and on the JM position in c-Kit, FLT3, and CSF1/cFMS. The described studies identify potential functions of the VEGFR2 JM domain with implications to both receptor biology and inhibitor design.

Targeting growth factors in lung cancer

Lung cancer causes more deaths than any other malignancy in the developed world. Advances in surgical techniques and chemotherapy/radiotherapy regimes have produced only minimal improvements in long-term survival. New therapeutic interventions are urgently required. Research has indicated that growth factor signaling may be an important novel target in lung cancer therapy. Preclinical studies have demonstrated the role of extracellular growth factors in lung cancer cell proliferation, metastasis, and resistance to cytotoxic therapy, and have elucidated the key molecular components of growth factor-signaling cascades. This has enabled the development of selective growth factor inhibitors, which have been evaluated in clinical trials and are now an accepted component of advanced lung cancer treatment. Further research is underway to improve the efficacy of this growth factor-targeted therapy. This article will outline the important aspects of this translational research indicating the growth factor-signaling pathways identified in lung cancer, clinical trials of anti-growth factor therapy, and potential future research directions.

Novel systemic therapies for small cell lung cancer

A diagnosis of small cell lung cancer (SCLC) today confers essentially the same terrible prognosis that it did 25 years ago, when common use of cisplatin-based chemotherapy began for this disease. In contrast to past decades of research on many other solid tumors, studies of combination chemotherapy using later generation cytotoxics and targeted kinase inhibitors have not had a significant impact on standard care for SCLC. The past few years have seen suggestions of incrementally improved outcomes using standard cytotoxics, including cisplatin-based combination studies of irinotecan and amrubicin by Japanese research consortia. Confirmatory phase III studies of these agents are ongoing in the United States. Antiangiogenic strategies are also of primary interest and are in late-phase testing. Several novel therapeutics, including high-potency small molecule inhibitors of Bcl-2 and the Hedgehog signaling pathway, and a recently discovered replication-competent picornavirus, have shown remarkable activity against SCLC in preclinical models and are currently in simultaneous phase I clinical development. Novel therapeutic approaches based on advances in understanding of the biology of SCLC have the potential to radically change the outlook for patients with this disease.

Role of MED12 in transcription and human behavior

The Mediator complex is a fluid assemblage of approximately 25 proteins that is essential for eukaryotic transcriptional regulation. Mediator of RNA polymerase II transcription (MED)12 (HOPA) is a 25-kb Xq13 member of the Mediator complex that plays a key role in the complex and directly moderates receptor tyrosine kinase, nuclear receptor and Wnt pathway signaling. Sequence variation in two MED12 protein domains has been linked to neuropsychiatric illness. First, variants in the Leu-Ser domain have been linked to Opitz-Kaveggia and Lujan syndromes, which are forms of X-linked mental retardation. Second, a balanced polymorphism in the C terminus opposite-paired domain, a key motif in the MED12-mediated transcriptional repression of Wnt signaling, has been associated with increased risk for psychosis. We conclude that variation of MED12 is associated with a wide variety of clinical presentations whose severity is dependent on the location and nature of the variation, and that a thorough understanding of MED12's role in transcriptional regulation could have significant benefits for human healthcare.

Biological characterization of two xenografts derived from human CUPs (carcinomas of unknown primary)

Background

Carcinomas of unknown primary site (CUP) are epithelial malignancies revealed by metastatic lesions in the absence of any detectable primary tumor. Although they often adopt an aggressive clinical pattern, their basic biology remains poorly understood. Laboratory research on their biology have been hampered so far by the absence of cell lines representative of CUPs.

Methods

We attempted xenografts of CUP clinical specimens in immunodeficient mice and subsequent in vitro culture of transplanted malignant cells. Whenever possible, malignant xenografted or cultured cells were characterized by microsatellite genotyping, immunohistology, electron microscopy, multifish chromosome analysis and search of TP 53 gene mutations.

Results

Successful xenografts were achieved in 2 cases out of 4. One of them (Capi1) was lost after 3 passages whereas the other one (Capi3) has been adapted to in vitro culture and is currently available to the scientific community with reliable identification based on microsatellite genotyping. Both Capi1 and Capi3 have histological characteristics of adenocarcinomas and display intense expression of EMA, CEA and cytokeratin 7. Multifish chromosome analysis demonstrated a translocation involving chromosomes 4 and 21 in both specimens. Distinct rare missense mutations of the TP53 gene were detected in Capi1 (codon 312) and Capi3 (codon 181); the codon 181 mutation is consistent with a previously reported similar finding in a small series of CUP specimens. Finally, intense membrane expression of c-kit was recorded in Capi3.

Conclusion

Our data suggest that xenografted tumors can be obtained from a substantial fraction of CUP clinical specimens. The hypothesis of a preferential association of CUPs with TP 53 mutations of codon 181 deserves further investigations. The Capi3 cell line will be a useful tool for assessment of novel c-kit inhibitors.