EGFRvIII Confers Sensitivity to Saracatinib in a STAT5-Dependent Manner in Glioblastoma.

Glioblastoma (GBM) is the most common primary malignant brain tumor in adults, with few effective treatments. EGFR alterations, including expression of the truncated variant EGFRvIII, are among the most frequent genomic changes in these tumors. EGFRvIII is known to preferentially signal through STAT5 for oncogenic activation in GBM, yet targeting EGFRvIII has yielded limited clinical success to date. In this study, we employed patient-derived xenograft (PDX) models expressing EGFRvIII to determine the key points of therapeutic vulnerability within the EGFRvIII-STAT5 signaling axis in GBM. Our findings reveal that exogenous expression of paralogs STAT5A and STAT5B augments cell proliferation and that inhibition of STAT5 phosphorylation in vivo improves overall survival in combination with temozolomide (TMZ). STAT5 phosphorylation is independent of JAK1 and JAK2 signaling, instead requiring Src family kinase (SFK) activity. Saracatinib, an SFK inhibitor, attenuates phosphorylation of STAT5 and preferentially sensitizes EGFRvIII+ GBM cells to undergo apoptotic cell death relative to wild-type EGFR. Constitutively active STAT5A or STAT5B mitigates saracatinib sensitivity in EGFRvIII+ cells. In vivo, saracatinib treatment decreased survival in mice bearing EGFR WT tumors compared to the control, yet in EGFRvIII+ tumors, treatment with saracatinib in combination with TMZ preferentially improves survival.

Carcinoma cells induce lumen filling and EMT in epithelial cells through soluble E-cadherin-mediated activation of EGFR.

In epithelial cancers, carcinoma cells coexist with normal cells. Although it is known that the tumor microenvironment (TME) plays a pivotal role in cancer progression, it is not completely understood how the tumor influences adjacent normal epithelial cells. In this study, a three-dimensional co-culture system comprising non-transformed epithelial cells (MDCK) and transformed carcinoma cells (MSV-MDCK) was used to demonstrate that carcinoma cells sequentially induce preneoplastic lumen filling and epithelial-mesenchymal transition (EMT) in epithelial cysts. MMP-9 secreted by carcinoma cells cleaves cellular E-cadherin (encoded by CDH1) from epithelial cells to generate soluble E-cadherin (sE-cad), a pro-oncogenic protein. We show that sE-cad induces EGFR activation, resulting in lumen filling in MDCK cysts. Long-term sE-cad treatment induced EMT. sE-cad caused lumen filling by induction of the ERK signaling pathway and triggered EMT through the sustained activation of the AKT pathway. Although it is known that sE-cad induces MMP-9 release and consequent EGFR activation in tumor cells, our results, for the first time, demonstrate that carcinoma cells can induce sE-cad shedding in adjacent epithelial cells, which leads to EGFR activation and the eventual transdifferentiation of the normal epithelial cells.

Na,K-ATPase ß-subunit cis homo-oligomerization is necessary for epithelial lumen formation in mammalian cells.

Na,K-ATPase is a hetero-oligomer of an α- and a ß-subunit. The α-subunit (Na,K-α) possesses the catalytic function, whereas the ß-subunit (Na,K-ß) has cell-cell adhesion function and is localized to the apical junctional complex in polarized epithelial cells. Earlier, we identified two distinct conserved motifs on the Na,K-ß(1) transmembrane domain that mediate protein-protein interactions: a glycine zipper motif involved in the cis homo-oligomerization of Na,K-ß(1) and a heptad repeat motif that is involved in the hetero-oligomeric interaction with Na,K-α(1). We now provide evidence that knockdown of Na,K-ß(1) prevents lumen formation and induces activation of extracellular regulated kinases 1 and 2 (ERK1/2) mediated by phosphatidylinositol 3-kinase in MDCK cells grown in three-dimensional collagen cultures. These cells sustained cell proliferation in an ERK1/2-dependent manner and did not show contact inhibition at high cell densities, as revealed by parental MDCK cells. This phenotype could be rescued by wild-type Na,K-ß(1) or heptad repeat motif mutant of Na,K-ß(1), but not by the glycine zipper motif mutant that abrogates Na,K-ß(1) cis homo-oligomerization. These studies suggest that Na,K-ß(1) cis homo-oligomerization rather than hetero-oligomerization with Na,K-α(1) is involved in epithelial lumen formation. The relevance of these findings to pre-neoplastic lumen filling in epithelial cancer is discussed.

Development of an FRα Companion Diagnostic Immunohistochemical Assay for Mirvetuximab Soravtansine.

CONTEXT.­: Folate receptor-α (FRα, encoded by the FOLR1 gene) is overexpressed in several solid tumor types, including epithelial ovarian cancer (EOC), making it an attractive biomarker and target for FRα-based therapy in ovarian cancer. OBJECTIVE.­: To describe the development, analytic verification, and clinical performance of the VENTANA FOLR1 Assay (Ventana Medical Systems Inc) in EOC. DESIGN.­: We used industry standard studies to establish the analytic verification of the VENTANA FOLR1 Assay. Furthermore, the VENTANA FOLR1 Assay was used in the ImmunoGen Inc-sponsored SORAYA study to select patients for treatment with mirvetuximab soravtansine (MIRV) in platinum-resistant EOC. RESULTS.­: The VENTANA FOLR1 Assay is highly reproducible, demonstrated by a greater than 98% overall percent agreement (OPA) for repeatability and intermediate precision studies, greater than 93% OPA for interreader and greater than 96% for intrareader studies, and greater than 90% OPA across all observations in the interlaboratory reproducibility study. The performance of the VENTANA FOLR1 Assay in the SORAYA study was evaluated by the overall staining acceptability rate, which was calculated using the number of patient specimens that were tested with the VENTANA FOLR1 Assay that had an evaluable result. In the SORAYA trial, data in patients who received MIRV demonstrated clinically meaningful efficacy, and the overall staining acceptability rate of the assay was 98.4%, demonstrating that the VENTANA FOLR1 Assay is safe and effective for selecting patients who may benefit from MIRV. Together, these data showed that the assay is highly reliable, consistently producing evaluable results in the clinical setting. CONCLUSIONS.­: The VENTANA FOLR1 Assay is a robust and reproducible assay for detecting FRα expression and identifying a patient population that derived clinically meaningful benefit from MIRV in the SORAYA study.

Elevated expression of Fn14 in non-small cell lung cancer correlates with activated EGFR and promotes tumor cell migration and invasion.

Lung cancer is the leading cause of cancer deaths worldwide; approximately 85% of these cancers are non-small cell lung cancer (NSCLC). Patients with NSCLC frequently have tumors harboring somatic mutations in the epidermal growth factor receptor (EGFR) gene that cause constitutive receptor activation. These patients have the best clinical response to EGFR tyrosine kinase inhibitors (TKIs). Herein, we show that fibroblast growth factor-inducible 14 (Fn14; TNFRSF12A) is frequently overexpressed in NSCLC tumors, and Fn14 levels correlate with p-EGFR expression. We also report that NSCLC cell lines that contain EGFR-activating mutations show high levels of Fn14 protein expression. EGFR TKI treatment of EGFR-mutant HCC827 cells decreased Fn14 protein levels, whereas EGF stimulation of EGFR wild-type A549 cells transiently increased Fn14 expression. Furthermore, Fn14 is highly expressed in EGFR-mutant H1975 cells that also contain an EGFR TKI-resistance mutation, and high TKI doses are necessary to reduce Fn14 levels. Constructs encoding EGFRs with activating mutations induced Fn14 expression when expressed in rat lung epithelial cells. We also report that short hairpin RNA-mediated Fn14 knockdown reduced NSCLC cell migration and invasion in vitro. Finally, Fn14 overexpression enhanced NSCLC cell migration and invasion in vitro and increased experimental lung metastases in vivo. Thus, Fn14 may be a novel therapeutic target for patients with NSCLC, in particular for those with EGFR-driven tumors who have either primary or acquired resistance to EGFR TKIs.

Real-World Biomarker Test Utilization and Subsequent Treatment in Patients with Early-Stage Non-small Cell Lung Cancer in the United States, 2011-2021.

INTRODUCTION: Biomarker testing is increasingly crucial for patients with early-stage non-small cell lung cancer (eNSCLC). We explored biomarker test utilization and subsequent treatment in eNSCLC patients in the real-world setting. METHODS: Using COTA's oncology database, this retrospective observational study included adult patients ≥ 18 years old diagnosed with eNSCLC (disease stage 0-IIIA) between January 1, 2011 and December 31, 2021. Date of first eNSCLC diagnosis was the study index date. We reported testing rates by index year for patients who received any biomarker test within 6 months of eNSCLC diagnosis and by each molecular marker. We also evaluated treatments received among patients receiving the five most common biomarker tests. RESULTS: Among the 1031 eNSCLC patients included in the analysis, 764 (74.1%) received ≥ 1 biomarker test within 6 months of eNSCLC diagnosis. Overall, epidermal growth factor receptor (EGFR; 64%), anaplastic lymphoma kinase (ALK; 60%), programmed death receptor ligand 1 (PD-L1; 48%), ROS proto-oncogene 1 (ROS1; 46%), B-Raf proto-oncogene (40%), mesenchymal epithelial transition factor receptor (35%), Kirsten rat sarcoma viral oncogene (29%), RET proto-oncogene (22%), human epidermal growth factor receptor 2 (21%), and phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (20%) were the 10 most frequently tested biomarkers. The proportion of patients undergoing biomarker testing rose from 55.3% in 2011 to 88.1% in 2021. The most common testing methods were Sanger sequencing for EGFR (244, 37%), FISH (fluorescence in situ hybridization) for ALK (464, 75%) and ROS1 (357, 76%), immunohistochemical assay for PD-L1 (450, 90%), and next-generation sequencing testing for other biomarkers. Almost all the 763 patients who received the five most common biomarker tests had a test before the initiation of a systemic treatment. CONCLUSION: This study suggests a high biomarker testing rate among patients with eNSCLC in the US, with testing rates for various biomarkers increasing over the past decade, indicating a continuous trend towards the personalization of treatment decisions.

Analytical and clinical validation of PATHWAY Anti-HER-2/neu (4B5) antibody to assess HER2-low status for trastuzumab deruxtecan treatment in breast cancer.

In DESTINY-Breast04 (DB-04), safety and efficacy of HER2-targeted antibody-drug conjugate (ADC) trastuzumab deruxtecan (T-DXd) in previously treated HER2-low unresectable/metastatic breast cancer were established. This manuscript describes the analytical validation of PATHWAY Anti-HER2/neu (4B5) Rabbit Monoclonal Primary Antibody (PATHWAY HER2 (4B5)) to assess HER2-low status and its clinical performance in DB-04. Preanalytical processing and tissue staining parameters were evaluated to determine their impact on HER2 scoring. The recommended antibody staining procedure provided the optimal tumor staining, and deviations in cell conditioning and/or antibody incubation times resulted in unacceptable negative control staining and/or HER2-low status changes. Comparisons between antibody lots, kit lots, instruments, and day-to-day runs showed overall percent agreements (OPAs) exceeding 97.9%. Inter-laboratory reproducibility showed OPAs of ≥97.4% for all study endpoints. PATHWAY HER2 (4B5) was utilized in DB-04 for patient selection using 1340 tumor samples (59.0% metastatic, 40.7% primary, (0.3% missing data); 74.3% biopsy, 25.7% resection/excisions). Overall, 77.6% (823/1060) of samples were HER2-low by both central and local testing, with the level of concordance differing by sample region of origin and collection date. In DB-04, the efficacy of T-DXd over chemotherapy of physician's choice was consistent, regardless of the characteristics of the sample used (primary or metastatic, archival, or newly collected, biopsy or excision/resection). These results demonstrate that PATHWAY HER2 (4B5) is precise and reproducible for scoring HER2-low status and can be used with multiple breast cancer sample types for reliably identifying patients whose tumors have HER2-low expression and are likely to derive clinical benefit from T-DXd.

Soluble E-cadherin promotes cell survival by activating epidermal growth factor receptor.

High levels of the soluble form of E-cadherin can be found in the serum of cancer patients and are associated with poor prognosis. Despite the possible predictive value of soluble E-cadherin, little is understood concerning its patho-physiological consequences in tumor progression. In this study, we show that soluble E-cadherin facilitates cell survival via functional interaction with cellular E-cadherin. Exposure of cells to a recombinant form of soluble E-cadherin, at a concentration found in cancer patient's serum, prevents apoptosis due to serum/growth factor withdrawal, and inhibits epithelial lumen formation, a process that requires apoptosis. Further, soluble E-cadherin-mediated cell survival involves activation of the epidermal growth factor receptor (EGFR) and EGFR-mediated activation of both phosphoinositide-3 kinase (PI3K)/AKT and ERK1/2 signaling pathways. These results are evidence of a complex functional interplay between EGFR and E-cadherin and also suggest that the presence of soluble E-cadherin in cancer patients' sera might have relevance to cell survival and tumor progression.

Computer-aided scoring of erb-b2 receptor tyrosine kinase 2 (HER2) gene amplification status in breast cancer.

Background: Identification of HER2 protein overexpression and/or amplification of the HER2 gene are required to qualify breast cancer patients for HER2 targeted therapies. In situ hybridization (ISH) assays that identify HER2 gene amplification function as a stand-alone test for determination of HER2 status and rely on the manual quantification of the number of HER2 genes and copies of chromosome 17 to determine HER2 amplification. Methods: To assist pathologists, we have developed the uPath HER2 Dual ISH Image Analysis for Breast (uPath HER2 DISH IA) algorithm, as an adjunctive aid in the determination of HER2 gene status in breast cancer specimens. The objective of this study was to compare uPath HER2 DISH image analysis vs manual read scoring of VENTANA HER2 DISH-stained breast carcinoma specimens with ground truth (GT) gene status as the reference. Three reader pathologists reviewed 220, formalin-fixed, paraffin-embedded (FFPE) breast cancer cases by both manual and uPath HER2 DISH IA methods. Scoring results from manual read (MR) and computer-assisted scores (image analysis, IA) were compared against the GT gene status generated by consensus of a panel of pathologists. The differences in agreement rates of HER2 gene status between manual, computer-assisted, and GT gene status were determined. Results: The positive percent agreement (PPA) and negative percent agreement (NPA) rates for image analysis (IA) vs GT were 97.2% (95% confidence interval [CI]: 95.0, 99.3) and 94.3% (95% CI: 90.8, 97.3) respectively. Comparison of agreement rates showed that the lower bounds of the 95% CIs for the difference of PPA and NPA for IA vs MR were -0.9% and -6.2%, respectively. Further, inter- and intra-reader agreement rates in the IA method were observed with point estimates of at least 96.7%. Conclusions: Overall, our data show that the uPath HER2 DISH IA is non-inferior to manual scoring and supports its use as an aid for pathologists in routine diagnosis of breast cancer.

Identification of a Blood-Based Protein Biomarker Panel for Lung Cancer Detection.

Lung cancer is the deadliest cancer worldwide, mainly due to its advanced stage at the time of diagnosis. A non-invasive method for its early detection remains mandatory to improve patients' survival. Plasma levels of 351 proteins were quantified by Liquid Chromatography-Parallel Reaction Monitoring (LC-PRM)-based mass spectrometry in 128 lung cancer patients and 93 healthy donors. Bootstrap sampling and least absolute shrinkage and selection operator (LASSO) penalization were used to find the best protein combination for outcome prediction. The PanelomiX platform was used to select the optimal biomarker thresholds. The panel was validated in 48 patients and 49 healthy volunteers. A 6-protein panel clearly distinguished lung cancer from healthy individuals. The panel displayed excellent performance: area under the receiver operating characteristic curve (AUC) = 0.999, positive predictive value (PPV) = 0.992, negative predictive value (NPV) = 0.989, specificity = 0.989 and sensitivity = 0.992. The panel detected lung cancer independently of the disease stage. The 6-protein panel and other sub-combinations displayed excellent results in the validation dataset. In conclusion, we identified a blood-based 6-protein panel as a diagnostic tool in lung cancer. Used as a routine test for high- and average-risk individuals, it may complement currently adopted techniques in lung cancer screening.

Dysfunction of ouabain-induced cardiac contractility in mice with heart-specific ablation of Na,K-ATPase beta1-subunit.

Na,K-ATPase is composed of two essential alpha- and beta-subunits, both of which have multiple isoforms. Evidence indicates that the Na,K-ATPase enzymatic activity as well as its alpha(1), alpha(3) and beta(1) isoforms are reduced in the failing human heart. The catalytic alpha-subunit is the receptor for cardiac glycosides such as digitalis, used for the treatment of congestive heart failure. The role of the Na,K-ATPase beta(1)-subunit (Na,K-beta(1)) in cardiac function is not known. We used Cre/loxP technology to inactivate the Na,K-beta(1) gene exclusively in the ventricular cardiomyocytes. Animals with homozygous Na,K-beta(1) gene excision were born at the expected Mendelian ratio, grew into adulthood, and appeared to be healthy until 10 months of age. At 13-14 months, these mice had 13% higher heart/body weight ratios, and reduced contractility as revealed by echocardiography compared to their wild-type (WT) littermates. Pressure overload by transverse aortic constriction (TAC) in younger mice, resulted in compensated hypertrophy in WT mice, but decompensation in the Na,K-beta(1) KO mice. The young KO survivors of TAC exhibited decreased contractile function and mimicked the effects of the Na,K-beta(1) KO in older mice. Further, we show that intact hearts of Na,K-beta(1) KO anesthetized mice as well as isolated cardiomyocytes were insensitive to ouabain-induced positive inotropy. This insensitivity was associated with a reduction in NCX1, one of the proteins involved in regulating cardiac contractility. In conclusion, our results demonstrate that Na,K-beta(1) plays an essential role in regulating cardiac contractility and that its loss is associated with significant pathophysiology of the heart.

alpha-Catenin overrides Src-dependent activation of beta-catenin oncogenic signaling.

Loss of alpha-catenin is one of the characteristics of prostate cancer. The catenins (alpha and beta) associated with E-cadherin play a critical role in the regulation of cell-cell adhesion. Tyrosine phosphorylation of beta-catenin dissociates it from E-cadherin and facilitates its entry into the nucleus, where beta-catenin acts as a transcriptional activator inducing genes involved in cell proliferation. Thus, beta-catenin regulates cell-cell adhesion and cell proliferation. Mechanisms controlling the balance between these functions of beta-catenin invariably are altered in cancer. Although a wealth of information is available about beta-catenin deregulation during oncogenesis, much less is known about how or whether alpha-catenin regulates beta-catenin functions. In this study, we show that alpha-catenin acts as a switch regulating the cell-cell adhesion and proliferation functions of beta-catenin. In alpha-catenin-null prostate cancer cells, reexpression of alpha-catenin increased cell-cell adhesion and decreased beta-catenin transcriptional activity, cyclin D1 levels, and cell proliferation. Further, Src-mediated tyrosine phosphorylation of beta-catenin is a major mechanism for decreased beta-catenin interaction with E-cadherin in alpha-catenin-null cells. alpha-Catenin attenuated the effect of Src phosphorylation by increasing beta-catenin association with E-cadherin. We also show that alpha-catenin increases the sensitivity of prostate cancer cells to a Src inhibitor in suppressing cell proliferation. This study reveals for the first time that alpha-catenin is a key regulator of beta-catenin transcriptional activity and that the status of alpha-catenin expression in tumor tissues might have prognostic value for Src targeted therapy.

EGFRvIII-Stat5 Signaling Enhances Glioblastoma Cell Migration and Survival.

Glioblastoma multiforme (GBM) is the most common brain malignancies in adults. Most GBM patients succumb to the disease less than 1 year after diagnosis due to the highly invasive nature of the tumor, which prevents complete surgical resection and gives rise to tumor recurrence. The invasive phenotype also confers radioresistant and chemoresistant properties to the tumor cells; therefore, there is a critical need to develop new therapeutics that target drivers of GBM invasion. Amplification of EGFR is observed in over 50% of GBM tumors, of which half concurrently overexpress the variant EGFRvIII, and expression of both receptors confers a worse prognosis. EGFR and EGFRvIII cooperate to promote tumor progression and invasion, in part, through activation of the Stat signaling pathway. Here, it is reported that EGFRvIII activates Stat5 and GBM invasion by inducing the expression of a previously established mediator of glioma cell invasion and survival: fibroblast growth factor-inducible 14 (Fn14). EGFRvIII-mediated induction of Fn14 expression is Stat5 dependent and requires activation of Src, whereas EGFR regulation of Fn14 is dependent upon Src-MEK/ERK-Stat3 activation. Notably, treatment of EGFRvIII-expressing GBM cells with the FDA-approved Stat5 inhibitor pimozide blocked Stat5 phosphorylation, Fn14 expression, and cell migration and survival. Because EGFR inhibitors display limited therapeutic efficacy in GBM patients, the EGFRvIII-Stat5-Fn14 signaling pathway represents a node of vulnerability in the invasive GBM cell populations.Implications: Targeting critical effectors in the EGFRvIII-Stat5-Fn14 pathway may limit GBM tumor dispersion, mitigate therapeutic resistance, and increase survival. Mol Cancer Res; 16(7); 1185-95. ©2018 AACR.

LKB1 inactivation occurs in a subset of esophageal adenocarcinomas and is sufficient to drive tumor cell proliferation.

BACKGROUND: The incidence of esophageal adenocarcinoma (EAC) has increased over the last several decades. Apart from mutations in TP53 gene, there are little data on genetic drivers of EAC. Liver kinase B1 (LKB1) has emerged as a multifunctional tumor suppressor regulating cell growth, differentiation, and metabolism. Somatic inactivation of LKB1 has been described in several tumor types; however, whether LKB1 inactivation has a role in EAC is unknown. Here we analyzed patient tumors to assess the prevalence of LKB1 loss in EAC. METHODS: Chromosomal deletion and expression of LKB1 in EAC were investigated using publicly available genomic data. Protein expression was assessed by immunohistochemistry (IHC) analysis for LKB1 in a tissue microarray (TMA) containing esophageal tumor specimens, including EAC. LKB1 was suppressed in EAC cells to determine the effects on cell growth in vitro. RESULTS: Analysis of EAC data in The Cancer Genome Atlas dataset revealed significant deletion of chromosome 19p13.3, containing the LKB1 gene locus. Single copy loss (shallow deletion) of LKB1 was present in 58% of EAC samples. Expression of LKB1 was significantly lower in EAC tumors compared with normal esophagus. IHC analysis showed reduced LKB1 protein expression in EAC. Suppression of LKB1 was sufficient to enhance EAC cell growth in vitro. CONCLUSIONS: Our data suggest that inactivation of LKB1 frequently occurs in EAC. Based on the reported oncogenic effects of LKB1 inactivation, our data indicate that LKB1 loss may play a significant role in EAC tumorigenesis, and point to the need for future studies.

WEE1 Kinase Inhibitor AZD1775 Has Preclinical Efficacy in LKB1-Deficient Non-Small Cell Lung Cancer.

G1-S checkpoint loss contributes to carcinogenesis and increases reliance upon the G2-M checkpoint for adaptation to stress and DNA repair, making G2-M checkpoint inhibition a target for novel therapeutic development. AZD1775, an inhibitor against the critical G2-M checkpoint protein WEE1, is currently in clinical trials across a number of tumor types. AZD1775 and DNA-damaging agents have displayed favorable activity in several preclinical tumor models, often in the molecular context of TP53 loss. Whether AZD1775 efficacy is modulated by other molecular contexts remains poorly understood. The tumor suppressor serine/threonine kinase 11 (LKB1/STK11) is one of the most frequently mutated genes in non-small cell lung cancer (NSCLC) and is commonly comutated with oncogenic KRAS mutations. We investigated the preclinical effects of AZD1775 in the context of KRAS/LKB1 in NSCLC. Using NSCLC cell lines, we found that AZD1775 alone and in combination with DNA-damaging agents (e.g., cisplatin and radiation) decreased tumor cell viability in LKB1-deficient NSCLC cells. In vitro, LKB1 deficiency enhanced DNA damage and apoptosis in response to AZD1775 exposure compared with wild-type LKB1 cells. In a genetically engineered mouse model of mutant Kras with concomitant loss of Lkb1, combined AZD1775 and cisplatin extended overall survival compared with cisplatin alone. Our data suggest that lack of phosphorylation of LKB1 by ATM was involved in AZD1775-mediated cytotoxicity. Collectively, these findings provide a clinical application for AZD1775 with DNA-damaging agents in KRAS/LKB1 NSCLC. Cancer Res; 77(17); 4663-72. ©2017 AACR.

Identification of aurintricarboxylic acid as a selective inhibitor of the TWEAK-Fn14 signaling pathway in glioblastoma cells.

The survival of patients diagnosed with glioblastoma (GBM), the most deadly form of brain cancer, is compromised by the proclivity for local invasion into the surrounding normal brain, which prevents complete surgical resection and contributes to therapeutic resistance. Tumor necrosis factor-like weak inducer of apoptosis (TWEAK), a member of the tumor necrosis factor (TNF) superfamily, can stimulate glioma cell invasion and survival via binding to fibroblast growth factor-inducible 14 (Fn14) and subsequent activation of the transcription factor NF-κB. To discover small molecule inhibitors that disrupt the TWEAK-Fn14 signaling axis, we utilized a cell-based drug-screening assay using HEK293 cells engineered to express both Fn14 and a NF-κB-driven firefly luciferase reporter protein. Focusing on the LOPAC1280 library of 1280 pharmacologically active compounds, we identified aurintricarboxylic acid (ATA) as an agent that suppressed TWEAK-Fn14-NF-κB dependent signaling, but not TNFα-TNFR-NF-κB driven signaling. We demonstrated that ATA repressed TWEAK-induced glioma cell chemotactic migration and invasion via inhibition of Rac1 activation but had no effect on cell viability or Fn14 expression. In addition, ATA treatment enhanced glioma cell sensitivity to both the chemotherapeutic agent temozolomide (TMZ) and radiation-induced cell death. In summary, this work reports a repurposed use of a small molecule inhibitor that targets the TWEAK-Fn14 signaling axis, which could potentially be developed as a new therapeutic agent for treatment of GBM patients.

Abnormal Capillary Vasodynamics Contribute to Ictal Neurodegeneration in Epilepsy.

Seizure-driven brain damage in epilepsy accumulates over time, especially in the hippocampus, which can lead to sclerosis, cognitive decline, and death. Excitotoxicity is the prevalent model to explain ictal neurodegeneration. Current labeling technologies cannot distinguish between excitotoxicity and hypoxia, however, because they share common molecular mechanisms. This leaves open the possibility that undetected ischemic hypoxia, due to ictal blood flow restriction, could contribute to neurodegeneration previously ascribed to excitotoxicity. We tested this possibility with Confocal Laser Endomicroscopy (CLE) and novel stereological analyses in several models of epileptic mice. We found a higher number and magnitude of NG2+ mural-cell mediated capillary constrictions in the hippocampus of epileptic mice than in that of normal mice, in addition to spatial coupling between capillary constrictions and oxidative stressed neurons and neurodegeneration. These results reveal a role for hypoxia driven by capillary blood flow restriction in ictal neurodegeneration.

Analysis of the phosphatidylinositol 3'-kinase signaling pathway in glioblastoma patients in vivo.

Deregulated signaling through the phosphatidylinositol 3'-kinase (PI3K) pathway is common in many types of cancer, including glioblastoma. Dissecting the molecular events associated with activation of this pathway in glioblastoma patients in vivo presents an important challenge that has implications for the development and clinical testing of PI3K pathway inhibitors. Using an immunohistochemical analysis applied to a tissue microarray, we performed hierarchical clustering and multidimensional scaling, as well as univariate and multivariate analyses, to dissect the PI3K pathway in vivo. We demonstrate that loss of the tumor suppressor protein PTEN, which antagonizes PI3K pathway activation, is highly correlated with activation of the main PI3K effector Akt in vivo. We also show that Akt activation is significantly correlated with phosphorylation of mammalian target of rapamycin (mTOR), the family of forkhead transcription factors (FOXO1, FOXO3a, and FOXO4), and S6, which are thought to promote its effects. Expression of the mutant epidermal growth factor receptor vIII is also tightly correlated with phosphorylation of these effectors, demonstrating an additional route to PI3K pathway activation in glioblastomas in vivo. These results provide the first dissection of the PI3K pathway in glioblastoma in vivo and suggest an approach to stratifying patients for targeted kinase inhibitor therapy.

beta-Catenin regulates vascular endothelial growth factor expression in colon cancer.

To evaluate whether beta-catenin signaling has a role in the regulation of angiogenesis in colon cancer, a series of angiogenesis-related gene promoters was analyzed for beta-catenin/TCF binding sites. Strikingly, the gene promoter of human vascular endothelial growth factor (VEGF, or VEGF-A) contains seven consensus binding sites for beta-catenin/TCF. Analysis of laser capture microdissected human colon cancer tissue indicated a direct correlation between up-regulation of VEGF-A expression and adenomatous polyposis coli (APC) mutational status (activation of beta-catenin signaling) in primary tumors. In metastases, this correlation was not observed. Analysis by immunohistochemistry of intestinal polyps in mice heterozygous for the multiple intestinal neoplasia gene (Min/+) at 5 months revealed an increase and redistribution of VEGF-A in proximity to those cells expressing nuclear beta-catenin with a corresponding increase in vessel density. Transfection of normal colon epithelial cells with activated beta-catenin up-regulated levels of VEGF-A mRNA and protein by 250-300%. When colon cancer cells with elevated beta-catenin levels were treated with beta-catenin antisense oligodeoxynucleotides, VEGF-A expression was reduced by more than 50%. Taken together, our observations indicate a close link between beta-catenin signaling and the regulation of VEGF-A expression in colon cancer.

N-glycosylation and microtubule integrity are involved in apical targeting of prostate-specific membrane antigen: implications for immunotherapy.

Prostate-specific membrane antigen (PSMA) is an important biomarker expressed in prostate cancer cells with levels proportional to tumor grade. The membrane association and correlation with disease stage portend a promising role for PSMA as an antigenic target for antibody-based therapies. Successful application of such modalities necessitates a detailed knowledge of the subcellular localization and trafficking of target antigen. In this study, we show that PSMA is expressed predominantly in the apical plasma membrane in epithelial cells of the prostate gland and in well-differentiated Madin-Darby canine kidney cells. We show that PSMA is targeted directly to the apical surface and that sorting into appropriate post-Golgi vesicles is dependent upon N-glycosylation of the protein. Integrity of the microtubule cytoskeleton is also essential for delivery and retention of PSMA at the apical plasma membrane domain, as destabilization of microtubules with nocodazole or commonly used chemotherapeutic Vinca alkaloids resulted in the basolateral expression of PSMA and increased the uptake of anti-PSMA antibody from the basolateral domain. These results may have important relevance to PSMA-based immunotherapy and imaging strategies, as prostate cancer cells can maintain a well-differentiated morphology even after metastasis to distal sites. In contrast to antigens on the basolateral surface, apical antigens are separated from the circulation by tight junctions that restrict transport of molecules across the epithelium. Thus, antigens expressed on the apical plasma membrane are not exposed to intravenously administered agents. The ability to reverse the polarity of PSMA from apical to basolateral could have significant implications for the use of PSMA as a therapeutic target.