CorrelationCalculator and Filigree: Tools for Data-Driven Network Analysis of Metabolomics Data

A significant challenge in the analysis of omics data is extracting actionable biological knowledge. Metabolomics is no exception. The general problem of relating changes in levels of individual metabolites to specific biological processes is compounded by the large number of unknown metabolites present in untargeted liquid chromatography-mass spectrometry (LC-MS) studies. Further, secondary metabolism and lipid metabolism are poorly represented in existing pathway databases. To overcome these limitations, our group has developed several tools for data-driven network construction and analysis. These include CorrelationCalculator and Filigree. Both tools allow users to build partial correlation-based networks from experimental metabolomics data when the number of metabolites exceeds the number of samples. CorrelationCalculator supports the construction of a single network, while Filigree allows building a differential network utilizing data from two groups of samples, followed by network clustering and enrichment analysis. We will describe the utility and application of both tools for the analysis of real-life metabolomics data.

A large-scale targeted proteomics of serum and tissue shows the utility of classifying high grade and low grade meningioma tumors

BACKGROUND

Meningiomas are the most prevalent primary brain tumors. Due to their increasing burden on healthcare, meningiomas have become a pivot of translational research globally. Despite many studies in the field of discovery proteomics, the identification of grade-specific markers for meningioma is still a paradox and requires thorough investigation. The potential of the reported markers in different studies needs further verification in large and independent sample cohorts to identify the best set of markers with a better clinical perspective.

METHODS

A total of 53 fresh frozen tumor tissue and 51 serum samples were acquired from meningioma patients respectively along with healthy controls, to validate the prospect of reported differentially expressed proteins and claimed markers of Meningioma mined from numerous manuscripts and knowledgebases. A small subset of Glioma/Glioblastoma samples were also included to investigate inter-tumor segregation. Furthermore, a simple Machine Learning (ML) based analysis was performed to evaluate the classification accuracy of the list of proteins.

RESULTS

A list of 15 proteins from tissue and 12 proteins from serum were found to be the best segregator using a feature selection-based machine learning strategy with an accuracy of around 80% in predicting low grade (WHO grade I) and high grade (WHO grade II and WHO grade III) meningiomas. In addition, the discriminant analysis could also unveil the complexity of meningioma grading from a segregation pattern, which leads to the understanding of transition phases between the grades.

CONCLUSIONS

The identified list of validated markers could play an instrumental role in the classification of meningioma as well as provide novel clinical perspectives in regard to prognosis and therapeutic targets.

Body mass index associates with amyotrophic lateral sclerosis survival and metabolomic profiles

INTRODUCTION/AIMS

Body mass index (BMI) is linked to amyotrophic lateral sclerosis (ALS) risk and prognosis, but additional research is needed. The aim of this study was to identify whether and when historical changes in BMI occurred in ALS participants, how these longer term trajectories associated with survival, and whether metabolomic profiles provided insight into potential mechanisms.

METHODS

ALS and control participants self-reported body height and weight 10 (reference) and 5 years earlier, and at study entry (diagnosis for ALS participants). Generalized estimating equations evaluated differences in BMI trajectories between cases and controls. ALS survival was evaluated by BMI trajectory group using accelerated failure time models. BMI trajectories and survival associations were explored using published metabolomic profiling and correlation networks.

RESULTS

Ten-year BMI trends differed between ALS and controls, with BMI loss in the 5 years before diagnosis despite BMI gains 10 to 5 years beforehand in both groups. An overall 10-year drop in BMI associated with a 27.1% decrease in ALS survival (P = .010). Metabolomic networks in ALS participants showed dysregulation in sphingomyelin, bile acid, and plasmalogen subpathways.

DISCUSSION

ALS participants lost weight in the 5-year period before enrollment. BMI trajectories had three distinct groups and the group with significant weight loss in the past 10 years had the worst survival. Participants with a high BMI and increase in weight in the 10 years before symptom onset also had shorter survival. Certain metabolomics profiles were associated with the BMI trajectories. Replicating these findings in prospective cohorts is warranted.

Effectiveness of immunological agents in non-small cell lung cancer

BACKGROUND AND AIM

Non-small cell lung cancer (NSCLC) continues to claim millions of lives worldwide. Although its poor prognosis is largely attributed to the lack of adequate and precise detection technologies, cancer cells' suppression of the immune system adds on to the difficulty of identifying abnormal NSCLC tumors in their early stages. Therefore, cancer immunotherapy, which activates the immune system and helps it fight tumors, has recently become the most sought-after technique, especially in the advanced stages of NSCLC, where surgery or chemotherapy may or may not bring about the desired survival benefits in patients.

METHODS

This review focuses on the various immunotherapeutic interventions and their efficacy in advanced NSCLC clinical trials. Monoclonal antibodies like anti-PD-1/PD-L1 agents and anti-CTLA-4 antibodies, cancer vaccines, oncolytic viruses and adoptive T cell therapy have been discussed in brief. Furthermore, the effects of gender, age, and race on the efficacy of immune checkpoint inhibitors and suggest plausible future approaches in the realm of immuno-oncology.

RESULTS

Immunotherapy is used alone or in combination either with other immunological agents or with chemotherapy. However, the efficacy of these strategies depends extensively on various demographic variables, as some patients respond perfectly well to immunotherapy, while others do not benefit at all or experience disease progression. By targeting a "hallmark" of cancer (immune evasion), immunotherapy has transformed NSCLC management, though several barriers prevent its complete effectiveness.

CONCLUSIONS

All these immunological strategies should be interpreted in the current setting of synergistic treatment, in which these agents can be combined with chemotherapy, radiotherapy, and, or surgery following patient and tumor characteristics to proportionate the best-individualized treatment and achieve superior results. To better pursue this goal, further investigations on cost-effectiveness and sex-gender, race, and age differences in immunotherapy are needed.

An overview of oral insulin delivery strategies (OIDS)

Despite tremendous efforts, the world continues its fight against the common chronic disease-diabetes. Diabetes is caused by elevated glucose levels in the blood, which can lead to several complications like glaucoma, cataract, kidney failure, diabetic ketoacidosis, heart attack, and stroke. According to recent statistics, China, India, and the US rank at the top three positions with regards to the number of patients affected by diabetes. Ever since its discovery, insulin is one of the major therapeutic molecules that is used to control the disease in the diabetic population, worldwide. The most common route of insulin administration has been the subcutaneous route. However, the limitations associated with this route have motivated global efforts to explore alternative strategies to deliver insulin, including pulmonary, transdermal, nasal, rectal, buccal, and oral routes. Oral insulin delivery is the most convenient and patient-centered route. However, the oral route is also associated with numerous drawbacks that present significant challenges to the scientific fraternity. The human physiological system acts as a formidable barrier to insulin, limiting its bioavailability. The present review covers the major barriers against oral insulin delivery and explains formulation strategies that have been adopted to overcome these barriers. The review focuses on oral insulin delivery strategies (OIDS) for increasing the bioavailability of oral insulin, including nanoparticles, microparticles, nano-in-microparticles, hydrogels, tablets, capsules, intestinal patches, and use of ionic liquids. It also highlights some of the notable recent advancements and clinical trials in oral insulin delivery. This formulation based OIDS may significantly improve patient compliance in the treatment of diabetes.

Metabolomic Profiling in Response to an Oral Glucose Tolerance Test Reveals Pathways Associated With Obesity and Insulin Resistance During the Pubertal Transition

Objectives

To reveal alterations in metabolic pathways in response to an oral glucose tolerance test (OGTT) underlying the development of insulin resistance during the pubertal transition.

Methods

Participants were recruited as healthy controls (HC, n = 55, aged 8.3–18.0 years, BMI percentile 5–85%) and overweight and obese individuals (OVOB, n = 228, aged 8.1–17.9 years, BMI percentile ≥ 85%). Participants were grouped based on their peak insulin response to the OGTT, stratified by peak at t30 (Group 1, n = 163), t60 (Group 2, n = 75), and t120 minutes (Group 3,

n = 44). Untargeted metabolomics profiled 267 annotated metabolites and > 3000 unannotated features in plasma at t0 and t60 minutes. Regression classified changes in metabolites across the time-course, assessing the influence of BMI and insulin response (FDR < 0.05). The connectivity of the metabolome was determined using differential network enrichment analysis (DNEA), stratified by insulin response group.

Results

At fasting, 32% of the metabolites differed between HC and OVOB, including elevated kynurenine, leucine/isoleucine, methionine, tyrosine, short-chain acylcarnitines, and diacylglycerols in OVOB. At t60, only 4% of the metabolites differed between HC and OVOB participants, suggesting a “normalization” of the metabolome, with exceptions of acylcarnitines and FA oxidation (FAO) intermediates. Although no metabolites differed significantly between insulin response group, differential subnetworks were observed, including increased connectivity between FA and FAO intermediates in Group 1 at t60, suggesting differential regulation in post-prandial FAs.

Conclusions

Profiling the metabolome response to an OGTT may highlight metabolic dysfunction prior to type 2 diabetes and will be used in future longitudinal analyses predicting insulin resistance trajectory.

Funding Sources

The National Institute of Child Health and Human Development, the National Institute of Diabetes and Digestive and Kidney Diseases, and the National Institutes of Health

Characterization of on-target adverse events caused by TRK inhibitor therapy

BACKGROUND

The tropomyosin receptor kinase (TRK) pathway controls appetite, balance, and pain sensitivity. While these functions are reflected in the on-target adverse events (AEs) observed with TRK inhibition, these AEs remain under-recognized, and pain upon drug withdrawal has not previously been reported. As TRK inhibitors are approved by multiple regulatory agencies for TRK or ROS1 fusion-positive cancers, characterizing these AEs and corresponding management strategies is crucial.

PATIENTS AND METHODS

Patients with advanced or unresectable solid tumors treated with a TRK inhibitor were retrospectively identified in a search of clinical databases. Among these patients, the frequency, severity, duration, and management outcomes of AEs including weight gain, dizziness or ataxia, and withdrawal pain were characterized.

RESULTS

Ninety-six patients with 15 unique cancer histologies treated with a TRK inhibitor were identified. Weight gain was observed in 53% [95% confidence interval (CI), 43%-62%] of patients and increased with time on TRK inhibition. Pharmacologic intervention, most commonly with glucagon-like peptide 1 analogs or metformin, appeared to result in stabilization or loss of weight. Dizziness, with or without ataxia, was observed in 41% (95% CI, 31%-51%) of patients with a median time to onset of 2 weeks (range, 3 days to 16 months). TRK inhibitor dose reduction was the most effective intervention for dizziness. Pain upon temporary or permanent TRK inhibitor discontinuation was observed in 35% (95% CI, 24%-46%) of patients; this was more common with longer TRK inhibitor use. TRK inhibitor reinitiation was the most effective intervention for withdrawal pain.

CONCLUSIONS

TRK inhibition-related AEs including weight gain, dizziness, and withdrawal pain occur in a substantial proportion of patients receiving TRK inhibitors. This safety profile is unique relative to other anticancer therapies and warrants careful monitoring. These on-target toxicities are manageable with pharmacologic intervention and dose modification.

Familial Acute Necrotizing Encephalopathy: Evidence From Next Generation Sequencing of Digenic Inheritance

Infection-induced acute encephalopathies (IIAEs) are a group of neurologic disorders caused post infection. They are of 8 types, 6 of which are herpes specific, whereas IIAE3 and IIAE4 can be triggered by infections additional to herpeslike influenza, enterovirus, etc. IIAE3 is also known as acute necrotizing encephalopathy type 1, which is a rare type of encephalopathy that occurs following an infection in infancy or early childhood. Symptoms include fever, cough, congestion, vomiting, and diarrhea followed by seizures, hallucination, ataxia, and abnormal muscle tone, and sometimes it leads to untimely death. Here, we describe a familial case where 3 siblings were clinically diagnosed with acute necrotizing encephalopathy 1. Genetic testing revealed 2 heterozygous variations: RANBP2 c.5249C>G, p.P1750 R, and CPT2 c.365C>T, p.S122F. Variants in RANBP2 and CPT2 have been individually known to be associated with IIAE3 and IIAE4, respectively. Segregation analysis revealed that the RANBP2 variant was inherited from the father and the CPT2 variant from the mother. This case qualifies to be the first of its kind where digenic inheritance (ie, DNA sequence variants in 2 genes are required for the pathogenic phenotypes) appears to cause a lethal class of acute necrotizing encephalopathy.

Novel therapies in urothelial carcinoma: a biomarker-driven approach

Urothelial malignancies, including carcinomas of the bladder, ureters, and renal pelvis comprised ∼8% of new cancer cases in the USA in 2016. In the metastatic setting, 15% of patients exhibit long-term survival following cisplatin-based chemotherapy and in patients with recurrent disease, response rates to second-line chemotherapy are generally 15%-20% with a 3-month progression-free survival. However, recent advances in immunotherapy represent an opportunity to significantly improve patient outcomes. Moreover, the advent of next-generation sequencing has resulted in both an improved understanding of the fundamental genetic changes that characterize urothelial carcinoma (UC) and identification of several candidate biomarkers of response to various therapies. Incorporation of prospective genotyping into clinical trials will allow for the identification and enrichment of patients most likely to respond to specific targeted therapies and chemotherapy. Combining different therapeutic classes to enhance outcomes is also an area of active research in UC.

Commentary on "DNA damage response and repair gene alterations are associated with improved survival in patients with platinum-treated advanced urothelial carcinoma."

PURPOSE

Platinum-based chemotherapy remains the standard treatment for advanced urothelial carcinoma by inducing DNA damage. We hypothesize that somatic alterations in DNA damage response and repair (DDR) genes are associated with improved sensitivity to platinum-based chemotherapy.

EXPERIMENTAL DESIGN

Patients with diagnosis of locally advanced and metastatic urothelial carcinoma treated with platinum-based chemotherapy who had exon sequencing with the Memorial Sloan Kettering-Integrated Mutation Profiling of Actionable Cancer Targets (MSK-IMPACT) assay were identified. Patients were dichotomized based on the presence/absence of alterations in a panel of 34 DDR genes. DDR alteration status was correlated with clinical outcomes and disease features.

RESULTS

One hundred patients were identified, of which 47 harbored alterations in DDR genes. Patients with DDR alterations had improved progression-free survival (9.3 vs. 6.0 months, log-rank P = 0.007) and overall survival (23.7 vs. 13.0 months, log-rank P = 0.006). DDR alterations were also associated with higher number mutations and copy-number alterations. A trend toward positive correlation between DDR status and nodal metastases and inverse correlation with visceral metastases were observed. Different DDR pathways also suggested variable effect on clinical outcomes.

CONCLUSIONS

Somatic DDR alteration is associated with improved clinical outcomes in platinum-treated patients with advanced urothelial carcinoma. Once validated, it can improve patient selection for clinical practice and future study enrollment.

Germline single nucleotide polymorphisms associated with response of urothelial carcinoma to platinum-based therapy: the role of the host

BACKGROUND

Variations in urothelial carcinoma (UC) response to platinum chemotherapy are common and frequently attributed to genetic and epigenetic variations of somatic DNA. We hypothesized that variations in germline DNA may contribute to UC chemosensitivity.

PATIENTS AND METHODS

DNA from 210 UC patients treated with platinum-based chemotherapy was genotyped for 80 single nucleotide polymorphisms (SNPs). Logistic regression was used to examine the association between SNPs and response, and a multivariable predictive model was created. Significant SNPs were combined to form a SNP score predicting response. Eleven UC cell lines were genotyped as validation.

RESULTS

Six SNPs were significantly associated with 101 complete or partial responses (48%). Four SNPs retained independence association and were incorporated into a response prediction model. Each additional risk allele was associated with a nearly 50% decrease in odds of response [odds ratio (OR) = 0.51, 95% confidence interval 0.39-0.65, P = 1.05 × 10(-7)). The bootstrap-adjusted area under the curves of this model was greater than clinical prognostic factors alone (0.78 versus 0.64). The SNP score showed a positive trend with chemosensitivity in cell lines (P = 0.115).

CONCLUSIONS

Genetic variants associated with response of UC to platinum-based therapy were identified in germline DNA. A model using these genetic variants may predict response to chemotherapy better than clinical factors alone.

Alterations in genes regulating cell cycle and apoptosis in high-grade urothelial carcinoma

237

Background: Dysregulations of cell cycle and inhibition of apoptosis are crucial factors in tumorigenesis of multiple malignancies, including urothelial carcinoma (UC). Deletions of TP53 and CDKN2A and amplification of MDM2 have been observed in UC, but their exact frequency and functional consequence is less known. We sought to determine the frequency of copy number alteration (CNA) and mutations of genes that regulate cell cycle or apoptosis in a panel of 96 cases of high-grade UC (HGUC) of bladder.

Methods: 96 frozen cases of HGUC were studied, including 11 bladder small cell carcinomas. DNA was isolated and analyzed for CNA by comparative genomic hybridization (CGH) using a one million oligonucleotide probe array from Agilent. The targeted genes included TP53, MDM2, CCND1, CCNE1, CDKN2A/B, E2F3 and Rb1. Traditional Sanger sequencing for mutations within TP53, Rb1, and CDKN2A was also performed.

Results: The frequency of CNA and mutations are listed in the table. Overall, 54 of 96 cases (56%) showed CNA (45) or mutation (13). Deletion of CDKN2A/B and amplification of E2F3 were the most common alterations in cell cycle regulatory genes (13 cases each, 14%), followed by amplification of CCND1 (11 cases, 11%). There was no co-amplification of CCND1 and CCNE1 in any sample. Rb1 deletion was present in five cases. CNA in E2F3 and Rb1 were mutually exclusive in 14 of 16 cases (88%) and were both present in two cases only. Mutations in TP53 were noted in 13 cases and deletions in nine. Amplification of MDM2 was noted in four cases, none of which overlapped with TP53 deletions or mutations. Overexpression of E2F3 was significantly more common in small cell carcinoma (5/11) compared to conventional UC (8/85, p = 0.006).

Conclusions: Regulators of cell cycle and apoptosis are amplified, deleted or mutated in more than half of cases (56%) of high-grade urothelial carcinoma. The overwhelming majority of these abnormalities are nonoverlapping. Amplification of E2F3 seems to be overrepresented in small cell carcinoma of bladder.

[Table: see text]

No significant financial relationships to disclose.

Peptide-coated semiconductor nanocrystals for biomedical applications

We have developed a new functionalization approach for semiconductor nanocrystals based on a single-step exchange of surface ligands with custom-designed peptides. This peptide-coating technique yield small, monodisperse and very stable water-soluble NCs that remain bright and photostable. We have used this approach on several types of core and core-shell NCs in the visible and near-infrared spectrum range and used fluorescence correlation spectroscopy for rapid assessment of the colloidal and photophysical properties of the resulting particles. This peptide coating strategy has several advantages: it yields probes that are immediately biocompatible; it is amenable to improvements of the different properties (solubilization, functionalization, etc) via rational design, parallel synthesis, or molecular evolution; it permits the combination of several functions on individual NCs. These functionalized NCs have been used for diverse biomedical applications. Two are discussed here: single-particle tracking of membrane receptor in live cells and combined fluorescence and PET imaging of targeted delivery in live animals.

Giant left atrium secondary to tight mitral stenosis leading to acquired Lutembacher syndrome: a case report with emphasis on role of echocardiography in assessment of Lutembacher syndrome

Lutembacher syndrome is an unusual clinical entity of congenital secundum atrial septal defect in combination with rheumatic mitral stenosis. Although this classic form is seldom seen by the adult cardiologist, spontaneous Lutembacher syndrome as discussed later or the iatrogenic variant is not infrequently encountered. The pathophysiologic, clinical, and hemodynamic differences of mitral valve disease in the presence of atrial septal defect compared with isolated mitral stenosis are highlighted in this case review. Special emphasis has also been given to echocardiographic evaluation of this syndrome complex, particularly in the setting of percutaneous mitral valvuloplasty, which produces the iatrogenic form of Lutembacher syndrome.

Perceiving, remembering, and communicating structure in events

How do people perceive routine events, such as making a bed, as these events unfold in time? Research on knowledge structures suggests that people conceive of events as goal-directed partonomic hierarchies. Here, participants segmented videos of events into coarse and fine units on separate viewings; some described the activity of each unit as well. Both segmentation and descriptions support the hierarchical bias hypothesis in event perception: Observers spontaneously encoded the events in terms of partonomic hierarchies. Hierarchical organization was strengthened by simultaneous description and, to a weaker extent, by familiarity. Describing from memory rather than perception yielded fewer units but did not alter the qualitative nature of the descriptions. Although the descriptions were telegraphic and without communicative intent, their hierarchical structure was evident to naive readers. The data suggest that cognitive schemata mediate between perceptual and functional information about events and indicate that these knowledge structures may be organized around object/action units.

Messenger RNA editing of the human serotonin 5-HT2C receptor

RNA encoding the rat serotonin 5-HT2C receptor undergoes editing whereby one to four adenosines are converted to inosines. This conversion can change up to three codons out of a stretch of five in the second intracellular loop of the receptor. RNA editing of the rat 5-HT2C receptor that changes all three codons was shown previously to alter intracellular signaling by 5-HT without changing its receptor-binding affinity. We analyzed 5-HT2C receptor editing in human brain and hypothalamic RNA samples and confirmed that all four adenosine editing sites observed in rat were also present in human samples. Additionally, we identified a novel editing site in the middle edited codon that extends the repertoire of 5-HT2C receptors by six additional protein isoforms. We observed that editing reduces both the binding affinity and functional potency of agonists for recombinant human 5-HT2C receptor isoforms. This effect on binding affinity was proportional to the agonist's intrinsic activity, with full agonists most affected, and antagonists showing no effect. These data suggest that RNA editing may alter coupling energetics within the ternary complex, thereby altering agonist binding affinities, G protein coupling, and functional responses. RNA editing may thus provide a novel mechanism for regulating 5-HT synaptic signaling and plasticity.

High-affinity agonist binding correlates with efficacy (intrinsic activity) at the human serotonin 5-HT2A and 5-HT2C receptors: evidence favoring the ternary complex and two-state models of agonist action

Many modern models of receptor-G protein function assume that there is a direct relationship between high-affinity agonist binding and efficacy. The validity of this assumption has been recently questioned for the serotonin 5-HT2A receptor. We examined the intrinsic activities of various ligands in activating phosphoinositide hydrolysis and measured their respective binding affinities to the high- and low-affinity states of the 5-HT2C (VNV isoform) and 5-HT(2A) receptors. Ligand binding affinities for the high-affinity state of the receptors were determined using 1-(4-[125I]iodo-2,5-dimethoxyphenyl)2-aminopropane, whereas [3H]mesulergine and N-[3H]methylspiperone were used, in the presence of excess guanine nucleotide [guanosine 5'-O-(3-thiotriphosphate)], to define binding to the low-affinity state of the 5-HT2C and 5-HT2A receptors, respectively. Antagonists labeled the high- and low-affinity states of each receptor with comparable affinities. Previously identified inverse agonists of the 5-HT2C receptor behaved as silent antagonists in our systems even when the receptor was overexpressed at a relatively high density. In contrast, the ability of agonists to bind differentially to the high- and low-affinity states of the 5-HT2A and 5-HT2C receptors was highly correlated (r2 = 0.86 and 0.96, respectively) with their intrinsic activities. These data suggest that high-affinity agonist states can account for agonist efficacy at human 5-HT2A or 5-HT2C receptors without the need for considering additional transition or active states of the receptor-ligand complex. The procedure described herein may expedite drug discovery efforts by predicting intrinsic activities of ligands solely from ligand binding assays.

Genetic vaccination-induced immune responses to the human immunodeficiency virus protein Rev: emergence of the interleukin 2-producing helper T lymphocyte

Rev M10 is a trans-dominant negative inhibitor of HIV replication. Hence, stable transduction of CD4+ T cells with Rev M10 represents a novel gene therapy aimed at inhibiting HIV replication within these cells, thereby slowing the progression of AIDS. However, the immune system may recognize Rev M10 as foreign and target transduced cells for elimination. In the current study, mice were genetically immunized with a plasmid encoding Rev M10, to (1) identify immune parameters that may be induced by Rev M10 gene transfer, (2) determine the impact of repeated introduction of the Rev M10-encoding plasmid on the immune response to the transgene product, and (3) determine if cotransfection with a plasmid encoding TGFbeta1 would suppress the response. Kinetic studies revealed that Rev-specific IL-2-producing helper T lymphocytes (HTLs) appeared following the second genetic immunization, peaked after the third, and persisted at peak levels for at least 6 weeks. Rev-specific HTLs were CD4+, and the development of these cells was ablated by cotransfection with TGFbeta1. Other cytokines were not readily detectable when immune splenocytes were restimulated with Rev in vitro, and Rev-specific IgG antibodies were not present in the sera of these mice. To our knowledge, this represents the first report that genetic immunization with Rev M10 induces an immune response that is dominated by IL-2-producing HTLs. Further, this study demonstrates the potential utility of introducing immunosuppressive genes as a means to control the immune response to foreign transgene products.

Fos is required for EGF stimulation of the gastrin promoter

Gastrin gene expression is regulated by developmental cues, pH, and inflammation. These processes are mediated by various extracellular ligands, e.g., growth factors, cytokines, and neuropeptides that also stimulate c-fos gene expression. Therefore, to determine whether Fos is required for stimulation of the gastrin promoter, a c-fos sense expression vector was coexpressed with a gastrin reporter construct in a GH4 rat pituitary cell line. We found that epidermal growth factor (EGF) and tumor necrosis factor-alpha (TNF-alpha) transiently stimulate an increase in Fos protein that precedes stimulation of the gastrin promoter. However, the induction mediated by TNF-alpha was weaker than that mediated by EGF, indicating minimal overlap of the signaling pathways activated by EGF and TNF-alpha. Accordingly, overexpression of c-fos mRNA facilitated primarily EGF rather than TNF-alpha induction of the gastrin promoter. Expression of the c-fos gene in the absence of ligand did not stimulate the gastrin promoter. Thus c-fos gene expression is required but is not sufficient for induction of the gastrin promoter by EGF.