KSR1 regulates small-cell lung carcinoma tumor initiation and therapy resistance

Small-cell lung cancer (SCLC) is designated a recalcitrant cancer due to its five-year relative survival rate of less than 7%. First line SCLC treatment has not changed in the last 40 years. The NeuroD1 subtype of SCLC (SCLC-N) commonly harbors MYC amplifications and other hallmarks of aggressive behavior. Finding novel therapeutic options that effectively eliminate residual disease observed after initial response to therapy is essential to improving SCLC patient outcome. Tumor-initiating cells (TICs) are reported as the sanctuary population within the bulk tumor responsible for therapeutic resistance and relapse. In contrast to earlier studies in which ERK activation is reported to be inhibitory to growth and tumor development, we show that KSR1 signaling is conserved in SCLC-N and that it regulates tumor initiation through ERK. Thus, KSR1 function in SCLC-N serves as a novel model for understanding the role of KSR1-dependent signaling in normal and malignant tissues. We further show that KSR1 mediates cisplatin resistance in SCLC-N cells. CRISPR/Cas9-mediated KSR1 knockout causes a dramatic increase in sensitivity to cisplatin and is coincident with a marked decrease in TICs, indicating that targeting KSR1 might be selectively toxic to cells responsible for therapeutic resistance and tumor initiation. Our data show that KSR1, a molecular scaffold for the Raf/MEK/ERK signaling cascade, is critical for tumor initiation and clonogenicity, both in vitro and in vivo in the highly aggressive, metastatic and therapy resistant NeuroD1 subtype of SCLC. These findings shed light on a key distinct protein responsible for regulation in SCLC-N tumors, and a potential subtype specific therapeutic target.

SOS1 and KSR1 modulate MEK inhibitor responsiveness to target resistant cell populations based on PI3K and KRAS mutation status

KRAS is the most commonly mutated oncogene. Targeted therapies have been developed against mediators of key downstream signaling pathways, predominantly components of the RAF/MEK/ERK kinase cascade. Unfortunately, single-agent efficacy of these agents is limited both by intrinsic and acquired resistance. Survival of drug-tolerant persister cells within the heterogeneous tumor population and/or acquired mutations that reactivate receptor tyrosine kinase (RTK)/RAS signaling can lead to outgrowth of tumor-initiating cells (TICs) and drive therapeutic resistance. Here, we show that targeting the key RTK/RAS pathway signaling intermediates SOS1 (Son of Sevenless 1) or KSR1 (Kinase Suppressor of RAS 1) both enhances the efficacy of, and prevents resistance to, the MEK inhibitor trametinib in KRAS-mutated lung (LUAD) and colorectal (COAD) adenocarcinoma cell lines depending on the specific mutational landscape. The SOS1 inhibitor BI-3406 enhanced the efficacy of trametinib and prevented trametinib resistance by targeting spheroid-initiating cells in KRASG12/G13-mutated LUAD and COAD cell lines that lacked PIK3CA comutations. Cell lines with KRASQ61 and/or PIK3CA mutations were insensitive to trametinib and BI-3406 combination therapy. In contrast, deletion of the RAF/MEK/ERK scaffold protein KSR1 prevented drug-induced SIC upregulation and restored trametinib sensitivity across all tested KRAS mutant cell lines in both PIK3CA-mutated and PIK3CA wild-type cancers. Our findings demonstrate that vertical inhibition of RTK/RAS signaling is an effective strategy to prevent therapeutic resistance in KRAS-mutated cancers, but therapeutic efficacy is dependent on both the specific KRAS mutant and underlying comutations. Thus, selection of optimal therapeutic combinations in KRAS-mutated cancers will require a detailed understanding of functional dependencies imposed by allele-specific KRAS mutations.

PGC-1β and ERRα Promote Glutamine Metabolism and Colorectal Cancer Survival via Transcriptional Upregulation of PCK2

Simple Summary

Peroxisome Proliferator-Activated Receptor Gamma, Coactivator 1 Beta (PGC-1β) and Estrogen-Related Receptor Alpha (ERRα) are proteins that are over-expressed to support the survival of colorectal cancer (CRC) cells, but the details of how they promote the growth of CRC has not been defined. In this article, we determine that PGC-1β and ERRα work together to increase the transcription of mitochondrial Phosphoenolpyruvate Carboxykinase 2 (PCK2). We show that PCK2 is required by CRC cells to optimally use amino acid L-glutamine to generate energy through the TCA cycle to support tumor cell survival and this is one mechanism used by PGC-1β and ERRα to promote the growth of CRC.

Abstract

Background: Previous studies have shown that Peroxisome Proliferator-Activated Receptor Gamma, Coactivator 1 Beta (PGC-1β) and Estrogen-Related Receptor Alpha (ERRα) are over-expressed in colorectal cancer and promote tumor survival. Methods: In this study, we use immunoprecipitation of epitope tagged endogenous PGC-1β and inducible PGC-1β mutants to show that amino acid motif LRELL on PGC-1β is responsible for the physical interaction with ERRα and promotes ERRα mRNA and protein expression. We use RNAsequencing to determine the genes regulated by both PGC-1β & ERRα and find that mitochondrial Phosphoenolpyruvate Carboxykinase 2 (PCK2) is the gene that decreased most significantly after depletion of both genes. Results: Depletion of PCK2 in colorectal cancer cells was sufficient to reduce anchorage-independent growth and inhibit glutamine utilization by the TCA cycle. Lastly, shRNA-mediated depletion of ERRα decreased anchorage-independent growth and glutamine metabolism, which could not be rescued by plasmid derived expression of PCK2. Discussion: These findings suggest that transcriptional control of PCK2 is one mechanism used by PGC-1β and ERRα to promote glutamine metabolism and colorectal cancer cell survival.

A novel anti-proliferative PKCα-Ras-ERK signaling axis in intestinal epithelial cells

We have previously shown that the serine/threonine kinase PKCα triggers MAPK/ERK kinase (MEK)-dependent G₁→S cell cycle arrest in intestinal epithelial cells, characterized by downregulation of cyclin D1 and inhibitor of DNA-binding protein 1 (Id1) and upregulation of the cyclin-dependent kinase inhibitor p21^Cip1. Here, we use pharmacological inhibitors, genetic approaches, siRNA-mediated knockdown, and immunoprecipitation to further characterize anti-proliferative ERK signaling in intestinal cells. We show that PKCα signaling intersects the Ras-Raf-MEK-ERK kinase cascade at the level of Ras small GTPases, and that anti-proliferative effects of PKCα require active Ras, Raf, MEK and ERK, core ERK pathway components that are also essential for pro-proliferative ERK signaling induced by epidermal growth factor (EGF). However, PKCα-induced anti-proliferative signaling differs from EGF signaling in that it is independent of the Ras guanine nucleotide exchange factors (Ras-GEFs), SOS1/2, and involves prolonged rather than transient ERK activation. PKCα forms complexes with A-Raf, B-Raf and C-Raf that dissociate upon pathway activation, and all three Raf isoforms can mediate PKCα-induced anti-proliferative effects. At least two PKCα-ERK pathways that collaborate to promote growth arrest were identified: one pathway requiring the Ras-GEF, RasGRP3, and H-Ras, leads to p21^Cip1 upregulation, while additional pathway(s) mediate PKCα-induced cyclin D1 and Id1 downregulation. PKCα also induces ERK-dependent SOS1 phosphorylation, indicating possible negative crosstalk between anti-proliferative and growth-promoting ERK signaling. Importantly, the spatio-temporal activation of PKCα and ERK in the intestinal epithelium in vivo supports the physiological relevance of these pathways and highlights the importance of anti-proliferative ERK signaling to tissue homeostasis in the intestine.

Contrasting effects of <i>Ksr2</i>, an obesity gene, on trabecular bone volume and bone marrow adiposity

Pathological obesity and its complications are associated with an increased propensity for bone fractures. Humans with certain genetic polymorphisms at the kinase suppressor of ras2 (KSR2) locus develop severe early-onset obesity and type 2 diabetes. Both conditions are phenocopied in mice with <i>Ksr2</i> deleted, but whether this affects bone health remains unknown. Here we studied the bones of global <i>Ksr2</i> null mice and found that <i>Ksr2</i> negatively regulates femoral, but not vertebral, bone mass in two genetic backgrounds, while the paralogous gene, <i>Ksr1</i>, was dispensable for bone homeostasis. Mechanistically, KSR2 regulates bone formation by influencing adipocyte differentiation at the expense of osteoblasts in the bone marrow. Compared with <i>Ksr2</i>'s known role as a regulator of feeding by its function in the hypothalamus, pair-feeding and osteoblast-specific conditional deletion of <i>Ksr2</i> reveals that <i>Ksr2</i> can regulate bone formation autonomously. Despite the gains in appendicular bone mass observed in the absence of <i>Ksr2</i>, bone strength, as well as fracture healing response, remains compromised in these mice. This study highlights the interrelationship between adiposity and bone health and provides mechanistic insights into how <i>Ksr2</i>, an adiposity and diabetic gene, regulates bone metabolism.

Combination antifungal therapy for breakthrough invasive mould disease in patients with haematological malignancies: when management reasoning eclipses evidence-based medicine

Timely diagnosis and treatment of invasive mould disease is challenging in severely immunocompromised patients, particularly for patients who develop breakthrough infections while on antifungal prophylaxis. Currently, there are no high-quality data on how to best diagnose and treat these infections. Many essential decisions affecting the management of breakthrough mould disease are made before a definitive diagnosis is established. In this scenario, sound management reasoning often favours the use of combination antifungal therapy, especially when antifungal resistance, suspicion of undetected sites of infection or pharmacokinetic/pharmacodynamic limitations at the site of infection are likely. In these scenarios, pre-emptive use of antifungal combination therapy with frequent re-evaluation with an aim of de-escalation could be justified for many high-risk patients.

KSR1- and ERK-dependent translational regulation of the epithelial-to-mesenchymal transition

The epithelial-to-mesenchymal transition (EMT) is considered a transcriptional process that induces a switch in cells from a polarized state to a migratory phenotype. Here, we show that KSR1 and ERK promote EMT-like phenotype through the preferential translation of Epithelial-Stromal Interaction 1 (EPSTI1), which is required to induce the switch from E- to N-cadherin and coordinate migratory and invasive behavior. EPSTI1 is overexpressed in human colorectal cancer (CRC) cells. Disruption of KSR1 or EPSTI1 significantly impairs cell migration and invasion in vitro, and reverses EMT-like phenotype, in part, by decreasing the expression of N-cadherin and the transcriptional repressors of E-cadherin expression, ZEB1 and Slug. In CRC cells lacking KSR1, ectopic EPSTI1 expression restored the E- to N-cadherin switch, migration, invasion, and anchorage-independent growth. KSR1-dependent induction of EMT-like phenotype via selective translation of mRNAs reveals its underappreciated role in remodeling the translational landscape of CRC cells to promote their migratory and invasive behavior.

A Gene Expression High-Throughput Screen (GE-HTS) for Coordinated Detection of Functionally Similar Effectors in Cancer

Genome-wide, loss-of-function screening can be used to identify novel vulnerabilities upon which specific tumor cells depend for survival. Functional Signature Ontology (FUSION) is a gene expression-based high-throughput screening (GE-HTS) method that allows researchers to identify functionally similar proteins, small molecules, and microRNA mimics, revealing novel therapeutic targets. FUSION uses cell-based high-throughput screening and computational analysis to match gene expression signatures produced by natural products to those produced by small interfering RNA (siRNA) and synthetic microRNA libraries to identify putative protein targets and mechanisms of action (MoA) for several previously undescribed natural products. We have used FUSION to screen for functional analogues to Kinase suppressor of Ras 1 (KSR1), a scaffold protein downstream of Ras in the Raf-MEK-ERK kinase cascade, and biologically validated several proteins with functional similarity to KSR1. FUSION incorporates bioinformatics analysis that may offer higher resolution of the endpoint readout than other screens which utilize Boolean outputs regarding a single pathway activation (i.e., synthetic lethal and cell proliferation). Challenges associated with FUSION and other high-content genome-wide screens include variation, batch effects, and controlling for potential off-target effects. In this review, we discuss the efficacy of FUSION to identify novel inhibitors and oncogene-induced changes that may be cancer cell-specific as well as several potential pitfalls within FUSION and best practices to avoid them.

Abstract 307: KSR1-dependent modulation of the translational landscape in Ras-driven colorectal cancer

KRAS is mutated and activated in an estimated 40% of colon cancers but has proven difficult to target directly due to the lack of drug-binding pockets on the surface of Ras. Thus, identifying effectors that transmit signals from oncogenic Ras is a critical step in targeting vulnerabilities in the tumors of patients with colorectal cancer (CRC). Kinase Suppressor of Ras 1 (KSR1) is a molecular scaffold that coordinates the interaction of effectors in the Raf/MEK/ERK signaling cascade downstream of Ras. KSR1 is necessary for oncogenic transformation of cells expressing mutated Ras but is dispensable for normal cell growth making KSR1 an attractive therapeutic target for Ras-driven colon cancers. In CRC cells, KSR1 and ERK mediate Ras-dependent effects on protein translation, notably driving cap-dependent and cap-independent translation of the Myc oncogene. Depletion of KSR1 or treatment with ERK inhibitor (SCH772984) leads to a decrease in phophorylated 4EBP1 and a decrease in PDCD4, which collectively impair protein translation, notably leading to a decrease in Myc translation. Patient-derived CRC organoids with deletion of APC, p53, and SMAD4, and an activating G12D mutation in KRAS treated with ERK inhibitor show a marked decrease in Myc protein expression, coincident with changes in PDCD4 and 4EBP1 that impair protein translation. These observations indicate that the KSR1-dependent ERK activation observed in CRC cell lines is present in pre-clinical colon tumoroid models. Genome-wide polysome profiling in CRC cell lines HCT116 and HCT15 depleted of KSR1 identified mRNAs that were preferentially translated in a KSR1 and ERK-dependent manner. Several of these mRNAs were previously predicted by our Functional Signature Ontology (FUSION) screen to be critical to CRC viability but dispensable for normal cell growth. GSEA identified functional classes of mRNAs whose translation is KSR1-dependent, including mediators of oncogenic signaling in pathways that regulate mTOR, MAPK, WNT and JAK-STAT. Our data suggest that an essential component of oncogenic Ras-induced and KSR1-dependent signaling is the preferential translation of mRNAs supporting the transformed phenotype of CRC cells.

Citation Format: Heidi Vieira, Chaitra Rao, Adrian R. Black, Siddesh Southekal, Tomohiro Mizutani, Babu Guda, Hans Clevers, Jennifer D. Black, Robert E. Lewis. KSR1-dependent modulation of the translational landscape in Ras-driven colorectal cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 307.

Serum bactericidal titres for monitoring antimicrobial therapy: current status and potential role in the management of multidrug-resistant Gram-negative infections

BACKGROUND

Serum bactericidal titres (SBTs) were widely used in the 1970s and 1980s to monitor antimicrobial therapy but are now seldom recommended. It is the only laboratory test that integrates drug pharmacodynamics, host pharmacokinetics and synergistic or antagonistic interactions of antimicrobial combinations into a single index of antimicrobial activity. We hypothesized that SBTs could play a renewed role in monitoring antibiotic treatment of multidrug-resistant Gram-negative infections. However, the last critical appraisal of the test was published over 30 years ago.

OBJECTIVES

This narrative review provides an updated assessment of the SBT test and its methodological limitations. We performed a diagnostic meta-analysis to estimate the value of SBTs for predicting clinical failure or death during antibiotic treatment.

SOURCES

A comprehensive literature search of PubMed including all English publications was performed in December 2019 using the Medical Subject Headings (MeSH search terms "serum", "bactericidal", "inhibitory", "titre", "monitoring", "anti-infective agents" "antimicrobial therapy" and "therapeutic drug monitoring").

CONTENT

Although standardized methods for performing SBTs were approved in 1999, the test remains labour intensive, and results may not be available until 72 hr. However, the use of non-culture-based endpoints (i.e. spectrophotometric or fluorescent) may shorten test time to 24 hr. Despite considerable heterogeneity in published studies, a meta-analysis of 11 evaluable studies published from 1974 to 2007 indicated a critical SBT result (peak SBT ≤1:8 or trough ≤1:2) is associated with a diagnostic odds ratio for clinical failure during antibiotic treatment of 12.27 (95% confidence interval 5.28-28.54) and a 5.32 (95% 1.32-21.42) odds of death.

IMPLICATIONS

SBTs have prognostic value for identifying patients at high risk for antibiotic treatment failure, but the slow turnaround time of the current test limits its clinical utility. Standardization of a more rapid SBT testing method is needed.

High-throughput identification of protein functional similarities using a gene-expression-based siRNA screen

A gene expression-based siRNA screen was used to evaluate functional similarity between genetic perturbations to identify functionally similar proteins. A siRNA library (siGenome library, Dharmacon) consisting of multiple siRNAs per gene that have been pooled in to one well per gene was arrayed in a 384-well format and used to individually target 14,335 proteins for depletion in HCT116 colon cancer cells. For each protein depletion, the gene expression of eight genes was quantified using the multiplexed Affymetrix Quantigene 2.0 assay in technical triplicate. As a proof of concept, six genes (BNIP3, NDRG1, ALDOC, LOXL2, ACSL5, BNIP3L) whose expression pattern reliably reflect the disruption of the molecular scaffold KSR1 were measured upon each protein depletion. The remaining two genes (PPIB and HPRT) are housekeeping genes used for normalization. The gene expression signatures from this screen can be used to estimate the functional similarity between any two proteins and successfully identified functional relationships for specific proteins such as KSR1 and more generalized processes, such as autophagy.

Measurement(s)	gene expression • KSR1 pathway regulation
Technology Type(s)	Microarray • RNA interference
Factor Type(s)	target RNA
Sample Characteristic - Organism	Homo sapiens

Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.11418018

A Genome-wide Functional Signature Ontology Map and Applications to Natural Product Mechanism of Action Discovery

Gene expression signature-based inference of functional connectivity within and between genetic perturbations, chemical perturbations, and disease status can lead to the development of actionable hypotheses for gene function, chemical modes of action, and disease treatment strategies. Here, we report a FuSiOn-based genome-wide integration of hypomorphic cellular phenotypes that enables functional annotation of gene network topology, assignment of mechanistic hypotheses to genes of unknown function, and detection of cooperativity among cell regulatory systems. Dovetailing genetic perturbation data with chemical perturbation phenotypes allowed simultaneous generation of mechanism of action hypotheses for thousands of uncharacterized natural products fractions (NPFs). The predicted mechanism of actions span a broad spectrum of cellular mechanisms, many of which are not currently recognized as "druggable." To enable use of FuSiOn as a hypothesis generation resource, all associations and analyses are available within an open source web-based GUI (http://fusion.yuhs.ac).

O-GlcNAc Transferase Suppresses Inflammation and Necroptosis by Targeting Receptor-Interacting Serine/Threonine-Protein Kinase 3

Elevated glucose metabolism in immune cells represents a hallmark feature of many inflammatory diseases, such as sepsis. However, the role of individual glucose metabolic pathways during immune cell activation and inflammation remains incompletely understood. Here, we demonstrate a previously unrecognized anti-inflammatory function of the O-linked β-N-acetylglucosamine (O-GlcNAc) signaling associated with the hexosamine biosynthesis pathway (HBP). Despite elevated activities of glycolysis and the pentose phosphate pathway, activation of macrophages with lipopolysaccharide (LPS) resulted in attenuated HBP activity and protein O-GlcNAcylation. Deletion of O-GlcNAc transferase (OGT), a key enzyme for protein O-GlcNAcylation, led to enhanced innate immune activation and exacerbated septic inflammation. Mechanistically, OGT-mediated O-GlcNAcylation of the serine-threonine kinase RIPK3 on threonine 467 (T467) prevented RIPK3-RIPK1 hetero- and RIPK3-RIPK3 homo-interaction and inhibited downstream innate immunity and necroptosis signaling. Thus, our study identifies an immuno-metabolic crosstalk essential for fine-tuning innate immune cell activation and highlights the importance of glucose metabolism in septic inflammation.

ERK-mediated TIMELESS expression suppresses G2/M arrest in colon cancer cells

The cell cycle is under circadian regulation. Oncogenes can dysregulate circadian-regulated genes to disrupt the cell cycle, promoting tumor cell proliferation. As a regulator of G2/M arrest in response to DNA damage, the circadian gene Timeless Circadian Clock (TIMELESS) coordinates this connection and is a potential locus for oncogenic manipulation. TIMELESS expression was evaluated using RNASeq data from TCGA and by RT-qPCR and western blot analysis in a panel of colon cancer cell lines. TIMELESS expression following ERK inhibition was examined via western blot. Cell metabolic capacity, propidium iodide, and CFSE staining were used to evaluate the effect of TIMELESS depletion on colon cancer cell survival and proliferation. Cell metabolic capacity following TIMELESS depletion in combination with Wee1 or CHK1 inhibition was assessed. TIMELESS is overexpressed in cancer and required for increased cancer cell proliferation. ERK activation promotes TIMELESS expression. TIMELESS depletion increases γH2AX, a marker of DNA damage, and triggers G2/M arrest via increased CHK1 and CDK1 phosphorylation. TIMELESS depletion in combination with Wee1 or CHK1 inhibition causes an additive decrease in cancer cell metabolic capacity with limited effects in non-transformed human colon epithelial cells. The data show that ERK activation contributes to the overexpression of TIMELESS in cancer. Depletion of TIMELESS increases γH2AX and causes G2/M arrest, limiting cell proliferation. These results demonstrate a role for TIMELESS in cancer and encourage further examination of the link between circadian rhythm dysregulation and cancer cell proliferation.

WDR5 supports colon cancer cells by promoting methylation of H3K4 and suppressing DNA damage

BACKGROUND

KMT2/MLL proteins are commonly overexpressed or mutated in cancer and have been shown to support cancer maintenance. These proteins are responsible for methylating histone 3 at lysine 4 and promoting transcription and DNA synthesis; however, they are inactive outside of a multi-protein complex that requires WDR5. WDR5 has been implicated in cancer for its role in the COMPASS complex and its interaction with Myc; however, the role of WDR5 in colon cancer has not yet been elucidated.

METHODS

WDR5 expression was evaluated using RT-qPCR and western blot analysis. Cell viability and colony forming assays were utilized to evaluate the effects of WDR5 depletion or inhibition in colon cancer cells. Downstream effects of WDR5 depletion and inhibition were observed by western blot.

RESULTS

WDR5 is overexpressed in colon tumors and colon cancer cell lines at the mRNA and protein level. WDR5 depletion reduces cell viability in HCT116, LoVo, RKO, HCT15, SW480, SW620, and T84 colon cancer cells. Inhibition of the WDR5:KMT2/MLL interaction using OICR-9429 reduces cell viability in the same panel of cell lines albeit not to the same extent as RNAi-mediated WDR5 depletion. WDR5 depletion reduced H3K4Me3 and increased phosphorylation of H2AX in HCT116, SW620, and RKO colon cancer cells; however, OICR-9429 treatment did not recapitulate these effects in all cell lines potentially explaining the reduced toxicity of OICR-9429 treatment as compared to WDR5 depletion. WDR5 depletion also sensitized colon cancer cells to radiation-induced DNA damage.

CONCLUSIONS

These data demonstrate a clear role for WDR5 in colon cancer and future studies should examine its potential to serve as a therapeutic target in cancer. Additional studies are needed to fully elucidate if the requirement for WDR5 is independent of or consistent with its role within the COMPASS complex. OICR-9429 treatment was particularly toxic to SW620 and T84 colon cancer cells, two cell lines without mutations in WDR5 and KMT2/MLL proteins suggesting COMPASS complex inhibition may be particularly effective in tumors lacking KMT2 mutations. Additionally, the ability of WDR5 depletion to amplify the toxic effects of radiation presents the possibility of targeting WDR5 to sensitize cells to DNA-damaging therapies.

Diagnosis and management of Aspergillus diseases: executive summary of the 2017 ESCMID-ECMM-ERS guideline

The European Society for Clinical Microbiology and Infectious Diseases, the European Confederation of Medical Mycology and the European Respiratory Society Joint Clinical Guidelines focus on diagnosis and management of aspergillosis. Of the numerous recommendations, a few are summarized here. Chest computed tomography as well as bronchoscopy with bronchoalveolar lavage (BAL) in patients with suspicion of pulmonary invasive aspergillosis (IA) are strongly recommended. For diagnosis, direct microscopy, preferably using optical brighteners, histopathology and culture are strongly recommended. Serum and BAL galactomannan measures are recommended as markers for the diagnosis of IA. PCR should be considered in conjunction with other diagnostic tests. Pathogen identification to species complex level is strongly recommended for all clinically relevant Aspergillus isolates; antifungal susceptibility testing should be performed in patients with invasive disease in regions with resistance found in contemporary surveillance programmes. Isavuconazole and voriconazole are the preferred agents for first-line treatment of pulmonary IA, whereas liposomal amphotericin B is moderately supported. Combinations of antifungals as primary treatment options are not recommended. Therapeutic drug monitoring is strongly recommended for patients receiving posaconazole suspension or any form of voriconazole for IA treatment, and in refractory disease, where a personalized approach considering reversal of predisposing factors, switching drug class and surgical intervention is also strongly recommended. Primary prophylaxis with posaconazole is strongly recommended in patients with acute myelogenous leukaemia or myelodysplastic syndrome receiving induction chemotherapy. Secondary prophylaxis is strongly recommended in high-risk patients. We strongly recommend treatment duration based on clinical improvement, degree of immunosuppression and response on imaging.

Treatment duration for Escherichia coli bloodstream infection and outcomes: retrospective single-centre study

OBJECTIVES

To investigate the impact of treatment duration on mortality and on relapse in patients with Escherichia coli bloodstream infection (BSI).

METHODS

Retrospective single-centre study of patients diagnosed with E. coli BSI at our centre over a 4-year period.

EXCLUSION CRITERIA

age <18 years, clinical data not available, polymicrobial BSI, failure to receive in vitro active therapy, and death while receiving antibiotic therapy. Exposure variable was treatment duration dichotomized into short (≤10 days) and long (>10 days) therapy. Primary end point was all-cause mortality within 90 days after index BSI. Secondary end point was relapse, defined as repeat isolation of E. coli from blood cultures within 90 days after index BSI, in patients with documented clinical cure and completion of therapy for the initial episode.

RESULTS

Of the 856 analysed patients: 426 received short and 430 received long therapy. All-cause mortality at day 90 occurred in 47 patients; on multivariate analysis, short therapy was not associated with a higher risk of mortality, also after adjusting the model for the propensity score of receiving short therapy. Relapse occurred in 42 patients. Independent risk factors for relapse using death as competing risk were immunosuppression (subhazard ratio 4.67, p < 0.001), and end-stage liver disease (subhazard ratio 2.58, p 0.013). The propensity-weighted estimation of the average treatment effect for relapse reduction with long therapy (>10 days) was -1.6% (p 0.26) in the total population, and -7.1% (p 0.18) in immunocompromised patients.

CONCLUSIONS

We could not identify shorter treatment duration as a risk factor for mortality and for relapse in patients with E. coli BSI.

A prospective international Aspergillus terreus survey: an EFISG, ISHAM and ECMM joint study

OBJECTIVES

A prospective international multicentre surveillance study was conducted to investigate the prevalence and amphotericin B susceptibility of Aspergillus terreus species complex infections.

METHODS

A total of 370 cases from 21 countries were evaluated.

RESULTS

The overall prevalence of A. terreus species complex among the investigated patients with mould-positive cultures was 5.2% (370/7116). Amphotericin B MICs ranged from 0.125 to 32 mg/L, (median 8 mg/L).

CONCLUSIONS

Aspergillus terreus species complex infections cause a wide spectrum of aspergillosis and the majority of cryptic species display high amphotericin B MICs.

KSR as a therapeutic target for Ras-dependent cancers

INTRODUCTION

Targeting downstream effectors required for oncogenic Ras signaling is a potential alternative or complement to the development of more direct approaches targeting Ras in the treatment of Ras-dependent cancers. Areas covered: Here we review literature pertaining to the molecular scaffold Kinase Suppressor of Ras (KSR) and its role in promoting signals critical to tumor maintenance. We summarize the phenotypes in knockout models, describe the role of KSR in cancer, and outline the structure and function of the KSR1 and KSR2 proteins. We then focus on the most recent literature that describes the crystal structure of the kinase domain of KSR2 in complex with MEK1, KSR-RAF dimerization particularly in response to RAF inhibition, and novel attempts to target KSR proteins directly. Expert opinion: KSR is a downstream effector of Ras-mediated tumorigenesis that is dispensable for normal growth and development, making it a desirable target for the development of novel therapeutics with a high therapeutic index. Recent advances have revealed that KSR can be functionally inhibited using a small molecule that stabilizes KSR in an inactive conformation. The efficacy and potential for this novel approach to be used clinically in the treatment of Ras-driven cancers is still being investigated.

Characterization of antibody response in neuroinvasive infection caused by Toscana virus

OBJECTIVES

Among sandfly-borne pathogens, Toscana virus (TOSV) is a prominent cause of summer meningitis in Mediterranean Europe. Here, we assessed the kinetics of anti-TOSV antibodies over time in 41 patients diagnosed with TOSV meningitis or meningoencephalitis in northeastern Italy.

METHODS

Acute and follow-up serum samples were collected up to 20 months after diagnosis of TOSV infection and tested for the presence of specific antibody using immunoenzymatic and indirect immunofluorescence assays. In addition, maturation of anti-TOSV IgG over time was evaluated as well as production of neutralizing antibodies.

RESULTS

Specific IgM and IgG response was present at diagnosis in 100% of patients; TOSV-specific IgM and IgG were detected in patients' sera up to 6 and 20 months after diagnosis, respectively. The avidity index (AI) increased over the first month after infection in 100% of patients and most cases exceeded 60% by Day 30 post infection. The AI subsequently plateaued then declined at 20 months after diagnosis. Finally, neutralization assay to TOSV was performed in 217 sera collected from 41 patients; 69.6% of tested samples resulted in reactive and moderate levels of neutralizing antibodies observed during all phases of infection despite high titres of total anti-TOSV IgG.

CONCLUSIONS

Specific antibody response develops rapidly and is long-lasting for neuroinvasive TOSV infection. Serodiagnosis of neuroinvasive TOSV requires simultaneous detection of specific IgM and IgG. Moderate levels of neutralizing antibodies were maintained over the study period, while the protective role of antibodies lacking neutralizing activity is unclear and requires further evaluation.

Abstract PR04: Translational control of human colon tumor cell survival

Kinase Suppressor of Ras 1 (KSR1), a molecular scaffold for the Raf/MEK/ERK kinase cascade, is required for transformation and survival of cells bearing oncogenic Ras, but is not required for normal cell survival. KSR1 knockout mice are phenotypically normal, and depletion of KSR1 by RNAi does not kill immortalized, non-transformed human colon epithelial cells (HCECs), suggesting that KSR1 or KSR1-dependent effectors may serve as highly selective therapeutic targets. Our previous work showed that KSR1 regulates expression of the transcription factor peroxisome proliferator-activated receptor gamma coactivator 1 (PGC1β), whose expression is critical to colon cancer cell survival. Using RNAi and pharmacological inhibition, we observed that KSR1 and ERK drive both cap-dependent and cap-independent translation of Myc in human colon tumor cell lines, which increases PGC1β mRNA expression (McCall et al. MCB, 2016). This effect is mediated through the KSR1 and ERK-dependent phosphorylation of 4E-PB1 and phosphorylation-dependent loss of PDCD4 that reverses their inhibitory effect on eIF4E and eIF4A, respectively. Treatment with ERK inhibitor SCH772984 showed that ERK regulates PDCD4 protein expression and 4EBP1 phosphorylation to promote Myc expression in four of the seven colon cancer cell lines. These observations suggest that KSR1-dependent regulation of translation may be a common mechanism used to support tumor cell survival. Using KSR1 as a reference standard, Functional Signature Ontology (FUSION, Potts et al. Sci. Signaling 2013) was used to identify genetic vulnerabilities in human colon tumor cells that are absent in HCECs. Comparison of results from this screen to genome-wide polysome profiling data from cells transformed with Ras and Myc (Truitt et al. Cell 2015) identified 25 candidate mRNAs with altered translational efficiency that are predicted to support the survival of human colon tumor cells. These data suggest that KSR1 and ERK-dependent alteration of the translational landscape is a common strategy used to support colon tumor cell survival. Identification of mRNAs preferentially translated in colon tumor cells may yield novel targets for therapeutic manipulation and may provide unique markers with which to classify colon tumors, predict patient outcome, and select effective treatment.

This abstract is also being presented as Poster B36.

Citation Format: Eyerusalem M. Lemma, Jamie L. McCall, Beth K. Clymer, David L. Kelly, Michael A. White, Robert E. Lewis. Translational control of human colon tumor cell survival. [abstract]. In: Proceedings of the AACR Special Conference on Translational Control of Cancer: A New Frontier in Cancer Biology and Therapy; 2016 Oct 27-30; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2017;77(6 Suppl):Abstract nr PR04.

Kinase Suppressor of Ras 2 (KSR2) expression in the brain regulates energy balance and glucose homeostasis

Objective

Kinase Suppressor of Ras 2 (KSR2) is a molecular scaffold coordinating Raf/MEK/ERK signaling that is expressed at high levels in the brain. KSR2 disruption in humans and mice causes obesity and insulin resistance. Understanding the anatomical location and mechanism of KSR2 function should lead to a better understanding of physiological regulation over energy balance.

Methods

Mice bearing floxed alleles of KSR2 (KSR2^fl/fl) were crossed with mice expressing the Cre recombinase expressed by the Nestin promoter (Nes-Cre) to produce Nes-CreKSR2^fl/fl mice. Growth, body composition, food consumption, cold tolerance, insulin and free fatty acid levels, glucose, and AICAR tolerance were measured in gender and age matched KSR2^−/− mice

Results

Nes-CreKSR2^fl/fl mice lack detectable levels of KSR2 in the brain. The growth and onset of obesity of Nes-CreKSR2^fl/fl mice parallel those observed in KSR2^−/− mice. As in KSR2^−/− mice, Nes-CreKSR2^fl/fl are glucose intolerant with elevated fasting and cold intolerance. Male Nes-CreKSR2^fl/fl mice are hyperphagic, but female Nes-CreKSR2^fl/fl mice are not. Unlike KSR2^−/− mice, Nes-CreKSR2^fl/fl mice respond normally to leptin and AICAR, which may explain why the degree of obesity of adult Nes-CreKSR2^fl/fl mice is not as severe as that observed in KSR2^−/− animals.

Conclusions

These observations suggest that, in the brain, KSR2 regulates energy balance via control of feeding behavior and adaptive thermogenesis, while a second KSR2-dependent mechanism, functioning through one or more other tissues, modulates sensitivity to leptin and activators of the energy sensor AMPK.

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Brain-specific KSR2 knockout causes obesity and glucose intolerance in both genders, but hyperphagia only in male mice.

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Brain-specific KSR2 knockout suppresses body temperature, before obesity.

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KSR2 in the brain regulates energy balance via control of feeding behavior and adaptive thermogenesis.

Antifungal prophylaxis in liver transplant recipients: one size does not fit all

BACKGROUND

Targeted antifungal prophylaxis against Candida species or against Candida species and Aspergillus species, according to individual patient risk factors (RFs), is recommended by experts. However, recent studies have reported fluconazole is as effective as broader spectrum antifungals for preventing invasive fungal infection (IFI) after liver transplantation (LT).

METHODS

We performed a retrospective cohort study of all adult patients who underwent LT at our 1420-bed tertiary teaching hospital, from June 2010 to December 2014, to assess the rate and etiology of IFI within 100 days after LT, to investigate the compliance with targeted prophylaxis, and to analyze risk factors for developing IFI.

RESULTS

In total, 303 patients underwent LT. Patients were classified as having low (no RFs), intermediate (1 RF for invasive candidiasis [IC]), and high risk (1 RF for invasive aspergillosis [IA] or ≥2 RFs for IC) for IFI in 20%, 30%, and 50% of cases, respectively. A total of 139 patients received antifungal prophylaxis: 98 with a mold-active drug and 41 with fluconazole. Overall adherence to targeted prophylaxis was 53%. Nineteen patients (6.3%) developed IFI: 7 IC and 12 IA. Multivariate Cox regression analysis, adjusted for median model for end-stage liver disease score at LT, stratification risk group, and adherence to targeted prophylaxis, showed that graft dysfunction, renal replacement therapy, and prophylaxis with fluconazole were independent risk factors for IFI. Seven of the 9 patients who received fluconazole prophylaxis and developed IFI were classified as having high risk for IFI, and 6 developed IA.

CONCLUSION

Recommended stratification is accurate for predicting patients at very high risk for IFI, who should receive prophylaxis with a mold-active drug.

Abstract 1252: TIMELESS is a KSR1-like effector of Ras-driven colon tumorigenesis

Multiple studies have revealed that Ras-driven tumors acquire unique vulnerabilities by adapting cellular mechanisms that promote uncontrolled proliferation and suppress apoptosis. Targeting these vulnerabilities provide opportunities to develop novel, efficacious cancer therapeutics that lack the harmful side effects accompanying current therapies. RNA interference (RNAi) of the molecular scaffold Kinase Suppressor of Ras 1 (KSR1), which modulates ERK activation downstream of oncogenic Ras, selectively kills malignant, Ras-driven cancer cells, but does not kill immortalized, non-transformed human colon epithelial cells (HCECs). With the exception of a minor hair follicle defect, KSR1-/- mice are fertile and phenotypically normal, suggesting that KSR1 is not required for normal cell survival and that Ras-driven and KSR1-dependent pathways may yield valuable new targets for therapeutic development.

To identify targets, like KSR1, that are required for cancer cell survival but not normal cell survival, we used a gene expression-based signature screening approach termed Functional Signature Ontology (FUSION, Potts et al. Sci. Signaling 2013) to screen 15,172 genes in the K-RasD13-bearing human colorectal cancer cell line HCT116. We quantified the functional similarity between KSR1 and each individual gene screened using Euclidean Distance and Pearson Correlation similarity metrics. Additional metrics were added to identify the best targets for biological validation including off-target analysis (siRNA seed sequences), cell viability evaluation, expression analysis, and enrichment analysis. Initial biological validation is completed by assessing cell viability following transient depletion of a screen hit in anchorage-independent and normal culture conditions in HCECs and HCT116s.

Due to the similarity between the gene expression signatures, Timeless Circadian Clock (TIMELESS) was identified as being KSR1-like and a potential target. We found that transient TIMELESS depletion decreases cell viability in HCT116 cells under anchorage-independent conditions (47% decrease, p &lt; 0.0001, N = 4). In normal culture conditions, TIMELESS depletion decreases cell viability in HCT116 cells, but not HCECs (HCEC 14% decrease, p &gt; 0.05; HCT116 49% decrease, p &lt; 0.0001, N = 6). TIMELESS is upregulated at the RNA level in colon tumors compared to normal colon tissue (∼2.2 fold, p &lt; 0.0001) (TCGA) and is upregulated at the protein level in three human colon cancer cell lines (HCT116, SW480, SW620) bearing activated Ras compared to HCECs (4-7 fold).

Our data indicate that the FUSION screen provides a platform for identifying novel therapeutic targets and demonstrates the potential to identify oncogene-specific vulnerabilities in an unbiased manner. TIMELESS overexpression represents a vulnerability in Ras-driven tumors that will reveal novel and selective targets found in Ras-driven cancers that can be used in the development of selective therapeutics.

Citation Format: Beth K. Clymer, Kurt W. Fisher, David L. Kelly, Michael A. White, Robert E. Lewis. TIMELESS is a KSR1-like effector of Ras-driven colon tumorigenesis. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1252.

AMPK Promotes Aberrant PGC1β Expression To Support Human Colon Tumor Cell Survival

A major goal of cancer research is the identification of tumor-specific vulnerabilities that can be exploited for the development of therapies that are selectively toxic to the tumor. We show here that the transcriptional coactivators peroxisome proliferator-activated receptor gamma coactivator 1β (PGC1β) and estrogen-related receptor α (ERRα) are aberrantly expressed in human colon cell lines and tumors. With kinase suppressor of Ras 1 (KSR1) depletion as a reference standard, we used functional signature ontology (FUSION) analysis to identify the γ1 subunit of AMP-activated protein kinase (AMPK) as an essential contributor to PGC1β expression and colon tumor cell survival. Subsequent analysis revealed that a subunit composition of AMPK (α2β2γ1) is preferred for colorectal cancer cell survival, at least in part, by stabilizing the tumor-specific expression of PGC1β. In contrast, PGC1β and ERRα are not detectable in nontransformed human colon epithelial cells, and depletion of the AMPKγ1 subunit has no effect on their viability. These data indicate that Ras oncogenesis relies on the aberrant activation of a PGC1β-dependent transcriptional pathway via a specific AMPK isoform.

Hormone receptor-independent CXCL10 production is associated with the regulation of cellular factors linked to breast cancer progression and metastasis

Breast cancer (BC) is a major health problem for women around the world. Although advances in the field of molecular therapy have been achieved, the successful therapeutic management of BC, particularly metastatic disease, remains a challenge for patients and clinicians. One of the areas of current investigation is the circulating tumor cells (CTCs), which have a determinant role in the development of distant metastasis. At the present, many of the available treatment strategies for metastatic disease are of limited benefit. However, the elucidation of the mechanisms of tumor progression and metastasis may help to identify key molecules/components that may function as therapeutic targets in the future. In the present study, the functional analysis of CTCs revealed their ability to grow and proliferate to form colonies. Immunofluorescence staining of the CTCs' colonies exhibits elevated expression of cell growth and survival associated proteins such as, survivin, ERK and Akt1. More importantly, the functional screening of the chemokine profile in BC patients' sera revealed an HR-independent elevation of the chemokine CXCL10 when compared to healthy controls. The analysis of chemokines CXCL9 and CXCL11 demonstrated an HR-dependent production pattern. The levels of both CXCL9 and CXCL11 were markedly high in HR+ patients' sera when compared to HR- patients and healthy controls. The functional analysis of HR+ and HR- BC derived cell lines when cultivated in media supplemented with patients' sera demonstrated the alteration of tumor progression and metastasis related proteins. We noted the induction of survivin, β-catenin, MKP-1, pERK, CXCR4 and MMP-1 both at the protein and mRNA levels. The induction of those proteins was in keeping with patients' sera induced cell proliferation as measured by the MTT assay. In conclusion, our data emphasizes the role of chemokines, especially CXCL10, in BC progression and metastasis via the induction of signaling pathways, which mainly involve survivin, β-catenin, MKP-1 and MMP-1.

Abstract A16: Overexpression and ubiquitination of kinase suppressor of Ras 1 (KSR1) in human colon tumor cells

Kinase Suppressor of Ras 1 (KSR1) is required for oncogenic Ras-induced transformation in mouse embryonic fibroblasts (MEFs) and human colon tumor cells, but is dispensable for normal cellular development. It is also overexpressed in a variety of human tumors, including human colon tumor cells. Seven human colon tumor cell lines with mutated and activated Ras (GEO, CBS, FET, SW480, HCT15, DLD1, and HCT116), one with wild type Ras (CaCo2), and non-transformed human colonic epithelial cells (HCECs) were assessed for KSR1 by western blot. Compared to HCECs, all eight tumor cell lines showed a marked decrease in electrophoretic motility. Seven of eight cell lines had a clear increase in KSR1 expression regardless of Ras mutation status. The purpose of the study is to examine the mechanism by which KSR1 is up-regulated in cancer cells.

Previous studies indicate that KSR proteins interact with multiple E3 ubiquitin ligase complexes including members homologous to the E6AP carboxyl terminus (HECT) domain family and the really interesting new gene (RING) family, including Cullin (Cul) 1, Cul4A, Cul4B, Cul7, damage-specific DNA binding protein 1 (DDB1), and DDB1-Cullin associating factor 1 (DCAF1), and ubiquitin protein ligase E3 component N-recognin 5 (UBR5/EDD1). Using tagged expression vectors and immunoprecipitation techniques, we investigated whether KSR1 is a substrate or a component of E3 ligase complexes. Both FLAG-tagged and endogenous KSR1 are ubiquitinated in the human colon tumor cell line, HCT-116. In HEK 293T cells, truncated KSR1 constructs were used to determine that KSR1 ubiquitination is dependent on the presence of the putative kinase domain in the C-terminal region. Furthermore, the kinase domain is sufficient for KSR1 ubiquitination by Cul4A/4B RING ligases (CRLs); however, silencing of Cul4A/4B by RNAi does not inhibit KSR1 ubiquitination. These data indicate that multiple Cullin family members may function to ubiquitinate KSR1. Additionally, KSR1 does not exclusively bind to Cullins, but also interacts with other components of the multi-subunit CRLs, including DDB1 and DCAF1. Therefore, KSR1 may not only be a direct substrate but also a member of the large complex helping to modulate activity of the CRL. Overall, these data suggest that Cul4A/4B-dependent ubiquitination of the KSR1 putative kinase may function to modulate KSR1-dependent signaling.

Citation Format: Jamie L. McCall, Ken Kono, Kurt W. Fisher, Manabu Furukawa, Robert E. Lewis. Overexpression and ubiquitination of kinase suppressor of Ras 1 (KSR1) in human colon tumor cells. [abstract]. In: Proceedings of the AACR Special Conference on RAS Oncogenes: From Biology to Therapy; Feb 24-27, 2014; Lake Buena Vista, FL. Philadelphia (PA): AACR; Mol Cancer Res 2014;12(12 Suppl):Abstract nr A16. doi: 10.1158/1557-3125.RASONC14-A16

Risk factors for carbapenem-resistant Klebsiella pneumoniae bloodstream infection among rectal carriers: a prospective observational multicentre study

Knowledge of carbapenem-resistant Klebsiella pneumoniae (CR-KP) colonization is important to prevent nosocomial spread but also to start prompt adequate antibiotic therapy in patients with suspicion of infection. However, few studies have examined the incidence and risk factors for CR-KP bloodstream infection (BSI) among rectal carriers. To identify risk factors for CR-KP BSI among carriers, we performed a multicentre prospective matched case-control study of all adult CR-KP rectal carriers hospitalized in five tertiary teaching hospitals in Italy over a 2-year period. Carriers who developed CR-KP BSI were compared with those who did not develop subsequent BSI. Overall, 143 CR-KP BSIs were compared with 572 controls without a documented infection during their hospitalization. Multivariate analysis revealed that admission to the Intensive Care Unit (ICU) (OR, 1.65; 95% CI, 1.05-2.59; p 0.03), abdominal invasive procedure (OR, 1.87; 95% CI, 1.16-3.04; p 0.01), chemotherapy/radiation therapy (OR, 3.07; 95% CI, 1.78-5.29; p <0.0001), and number of additional colonization sites (OR, 3.37 per site; 95% CI, 2.56-4.43; p <0.0001) were independent risk factors for CR-KP BSI development among CR-KP rectal carriers. A CR-KP BSI risk score ranging from 0 to 28 was developed based on these four independent variables. At a cut-off of ≥2 the model exhibited a sensitivity, specificity, positive predictive value and negative predictive value of 93%, 42%, 29% and 93%, respectively. Colonization at multiple sites with CR-KP was the strongest predictor of BSI development in our large cohort of CR-KP rectal carriers.

Obesity-dependent dysregulation of glucose homeostasis in kinase suppressor of ras 2-/- mice

Disruption of KSR2 in humans and mice decreases metabolic rate and induces obesity, coincident with dysregulation of glucose homeostasis. Relative to wild‐type mice, ksr2^−/− mice are small prior to weaning with normal glucose tolerance at 6 weeks of age, but demonstrate excess adiposity by 9 weeks and glucose intolerance by 12–14 weeks. Defects in AICAR tolerance, a measure of whole‐body AMPK activation, are detectable only when ksr2^−/− mice are obese. Food restriction prevents the obesity of adult ksr2^−/− mice and normalizes glucose and AICAR sensitivity. Obesity and glucose intolerance return when ad lib feeding is restored to the diet‐restricted mice, indicating that glucose dysregulation is secondary to obesity in ksr2^−/− mice. The phenotype of C57BL/6 ksr2^−/− mice, including obesity and obesity‐related dysregulation of glucose homeostasis, recapitulates that of humans with KSR2 mutations, demonstrating the applicability of the C57BL/6 ksr2^−/− mouse model to the study of the pathogenesis of human disease. These data implicate KSR2 as a physiological regulator of glucose metabolism during development affecting energy sensing, insulin signaling, and lipid storage, and demonstrate the value of the C57BL/6 ksr2^−/− mouse model as a unique and relevant model system in which to develop and test therapeutic targets for the prevention and treatment of obesity, type 2 diabetes, and obesity‐related metabolic disorders.

A fraction of individuals with obesity‐induced insulin resistance and diabetes respond to diet with improved glucose metabolism. The phenotype of C57BL/6 ksr2^−/− mice, including obesity and obesity‐related dysregulation of glucose homeostasis, recapitulates that of humans with KSR2 mutations. These data show that the glucose intolerance and AICAR insensitivity that accompanies KSR2 disruption in mice is preventable or reversible by diet, suggesting that dietary intervention in humans with KSR2 mutations should have similar effects.

Toll-like receptor (TLR) expression of immune system cells from metastatic breast cancer patients with circulating tumor cells

The risk posed by breast cancer represents a complex interaction among factors affecting tumor immunity of the host. Toll-like receptors (TLRs) are members of the innate immune system and generally function to attract host immune cells upon activation. However, the good intentions of TLRs are sometimes not transferred to positive long-term effects, due to their involvement in exacerbating inflammatory effects and even contributing to continued inflammation. Chronic inflammatory states are considered to favor an increased predisposition to cancer, with continuous activation of inflammatory cytokines and other hallmarks of inflammation exerting a deleterious effect. Circulating tumor cells (CTCs) are neoplastic cells present in the peripheral blood circulation that have been found to be an indicator of disease progression and long-term survival. In the present study, we examined the expression of TLRs on dendritic cells, which play a major role in eliciting anti-tumor immunity, in metastatic breast cancer patients with CTCs. Flow cytometric data showed significant differences between circulating tumor cell (CTC) positive patients and CTC negative patients in their expression of TLR2 by CD8 positive cytotoxic T cells and TLR2, TLR4, TLR3, and TLR8 by CD11c positive dendritic cells (p<0.05). Expression of TLR2, TLR4, and TLR8 was increased in CTC positive patients, whereas TLR3 expression was decreased in the dendritic cell population.

Identification of a truncated kinase suppressor of Ras 2 mRNA in sperm

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A truncated kinase suppressor of Ras 2 (T-KSR2) mRNA was identified.

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T-KSR2 is expressed exclusively in mouse testes and sperm.

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Analysis of T-KSR2 may enhance understanding of spermatogenesis and fertility.

The kinase suppressor of Ras 2 (KSR2) is a scaffold protein for the extracellular signal-regulated protein kinase (ERK) signaling pathway. KSR2 mediates germline mpk-1 (Caenorhabditis elegans ERK) phosphorylation in C. elegans and has been implicated the regulation of meiosis. KSR2^−/− mice exhibit metabolic abnormalities and are reproductively impaired. The role of KSR2 in meiosis and fertility in mice has yet to be elucidated. Here, we describe a novel truncated KSR2 mRNA identified in mouse testes (T-KSR2). Further analysis demonstrates T-KSR2 is specific to mouse testes and mature sperm cells. The detection of T-KSR2 may enhance our understanding of mechanisms controlling spermatogenesis and fertility.

Comparative analysis of innate immune system function in metastatic breast, colorectal, and prostate cancer patients with circulating tumor cells

In recent years, circulating tumor cells (CTCs) in metastatic cancer patients have been found to be a promising biomarker to predict overall survival and tumor progression in these patients. A relatively high number of CTCs has been correlated with disease progression and poorer prognosis. This study was designed to assess innate immune system function, known to be responsible for the immune defense against developing neoplasms, in metastatic cancer patients with CTCs. Our aim is to provide a link between indication of poorer prognosis, represented by the number of CTCs to the cytotoxic activity of natural killer cells, an important component of the innate immune system, and to represent a promising expanded approach to management of metastatic cancer patients with CTCs. Seventy-four patients, with metastatic breast, colorectal, or prostate cancer, were recruited for this study. Using a flow cytometric assay, we measured natural killer (NK) cell cytotoxicity against K562 target cells; and CTCs were enumerated using the CellSearch System. Toll-like receptors 2 and 4 expression was also determined by flow cytometry. We found that within each of our three metastatic cancer patient groups, NK cell cytotoxic activity was decreased in patients with a relatively high number of CTCs in peripheral blood compared to patients with a relatively low number of CTCs. In the breast and prostate cancer group, patients with CTCs greater than 5 had decreased NK cell cytotoxicity when compared to patients with less than 5 CTCs. In the colorectal cancer group, we found that 3 or more CTCs in the blood was the level at which NK cell cytotoxicity is diminished. Additionally, we found that the toll-like receptors 2 and 4 expression was decreased in intensity in all the metastatic cancer patients when compared to the healthy controls. Furthermore, within each cancer group, the expression of both toll-like receptors was decreased in the patients with relatively high number of CTCs, i.e. greater than 5 for the breast and prostate cancer group and greater than 3 for the colorectal cancer group, compared to the patients with relatively low number, i.e. less than 5 or 3, respectively. Treatment options to increase NK cell cytotoxic activity should be considered in patients with relatively high numbers of CTCs.

Using functional signature ontology (FUSION) to identify mechanisms of action for natural products

A challenge for biomedical research is the development of pharmaceuticals that appropriately target disease mechanisms. Natural products can be a rich source of bioactive chemicals for medicinal applications but can act through unknown mechanisms and can be difficult to produce or obtain. To address these challenges, we developed a new marine-derived, renewable natural products resource and a method for linking bioactive derivatives of this library to the proteins and biological processes that they target in cells. We used cell-based screening and computational analysis to match gene expression signatures produced by natural products to those produced by small interfering RNA (siRNA) and synthetic microRNA (miRNA) libraries. With this strategy, we matched proteins and miRNAs with diverse biological processes and also identified putative protein targets and mechanisms of action for several previously undescribed marine-derived natural products. We confirmed mechanistic relationships for selected siRNAs, miRNAs, and compounds with functional roles in autophagy, chemotaxis mediated by discoidin domain receptor 2, or activation of the kinase AKT. Thus, this approach may be an effective method for screening new drugs while simultaneously identifying their targets.

Circulating tumor cells (CTCs) from metastatic breast cancer patients linked to decreased immune function and response to treatment

We aimed to examine the use of circulating tumor cells (CTCs) as an effective measure of treatment efficacy and immune system function in metastatic breast cancer patients. CTCs are believed to be indicators of residual disease and thus pose an increased risk of metastasis and poorer outcomes to those patients who are CTC-positive. We obtained peripheral blood samples from 45 patients previously diagnosed with metastatic disease originating in the breast. Using TLR agonists that bind TLR ligands and upregulate immune effects versus unstimulated cells, we calculated a percent specific lysis using chromium-51 assay to illustrate the functional abilities of patient natural killer (NK) cells. We found those with greater than 5 CTCs per 7.5 mL blood had significantly decreased responses by their immune cells when compared with those patients who had 5 CTCs or less. We furthermore found a correlation between disease progression and CTC-positive patients, indicating that those who have a positive test should be closely monitored by their clinician. CTCs represent an exciting new clinical opportunity that will ideally utilize their low invasiveness and quick turnaround time to best benefit clinical scenarios.

Decreased humoral antibody episodes of acute renal allograft rejection in recipients expressing the HLA-DQβ1*0202 allele

The present investigation was designed to show the effect of human leukocyte antigen (HLA) class II molecular allelic specificities in the recipient on the induction of humoral antibody rejection, identified by C4d peritubular capillary staining, as well as specific antibody identified by Luminex technology. Major histocompatibility complex (MHC) class II molecules are expressed on dendritic cells, macrophages, and B lymphocytes and they present antigenic peptides to CD4 positive T lymphocytes. Human renal peritubular and glomerular capillaries express class II MHC molecules upon activation. Expression of class II molecules on renal microvascular endothelial cells exposes them to possible interaction with specific circulating antibodies. We hypothesize that HLA-DQβ1*0202 expression in recipients decreases the likelihood of antibody-mediated renal allograft rejection. We found that 80% (=25) of DQ2 positive haplotype recipients failed to induce humoral antibody renal allograft rejection and 20% (n=25) of DQ2 positive haplotype recipients induced humoral antibody renal allograft rejection (p=0.008). By contrast, 48% (n=46) of DQ2 negative haplotype recipients failed to induce a humoral antibody component of renal allograft rejection and 52% (n=46) of DQ2 negative haplotype recipients induced humoral antibody-mediated renal allograft rejection. Our results suggest that recipients who express the DQβ1*0202 allele are less likely to induce a humoral antibody component of acute renal allograft rejection than are those expressing DQ1, DQ3, or DQ4 alleles. DQβ1*0202 allele expression in recipients could possibly be protective against acute humoral allograft rejection and might serve as a future criterion in recipient selection and in appropriate therapy for acute renal rejection episodes.

KIBRA protein phosphorylation is regulated by mitotic kinase aurora and protein phosphatase 1

Recent genetic studies in Drosophila identified Kibra as a novel regulator of the Hippo pathway, which controls tissue growth and tumorigenesis by inhibiting cell proliferation and promoting apoptosis. The cellular function and regulation of human KIBRA remain largely unclear. Here, we show that KIBRA is a phosphoprotein and that phosphorylation of KIBRA is regulated in a cell cycle-dependent manner with the highest level of phosphorylated KIBRA detected in mitosis. We further demonstrate that the mitotic kinases Aurora-A and -B phosphorylate KIBRA both in vitro and in vivo. We identified the highly conserved Ser(539) as the primary phosphorylation site for Aurora kinases. Moreover, we found that wild-type, but not catalytically inactive, protein phosphatase 1 (PP1) associates with KIBRA. PP1 dephosphorylated Aurora-phosphorylated KIBRA. KIBRA depletion impaired the interaction between Aurora-A and PP1. We also show that KIBRA associates with neurofibromatosis type 2/Merlin in a Ser(539) phosphorylation-dependent manner. Phosphorylation of KIBRA on Ser(539) plays a role in mitotic progression. Our results suggest that KIBRA is a physiological substrate of Aurora kinases and reveal a new avenue between KIBRA/Hippo signaling and the mitotic machinery.

KSR1 is overexpressed in endometrial carcinoma and regulates proliferation and TRAIL-induced apoptosis by modulating FLIP levels

The Raf/MEK/extracellular signal-regulated kinase (ERK) pathway participates in many processes altered in development and progression of cancer in human beings such as proliferation, transformation, differentiation, and apoptosis. Kinase suppressor of Ras 1 (KSR1) can interact with various kinases of the Raf/MEK/extracellular signal-regulated kinase pathway to enhance its activation. The role of KSR1 in endometrial carcinogenesis was investigated. cDNA and tissue microarrays demonstrated that expression of KSR1 was up-regulated in endometrial carcinoma. Furthermore, inhibition of KSR1 expression by specific small hairpin RNA resulted in reduction of both proliferation and anchorage-independent cell growth properties of endometrial cancer cells. Because inhibition of apoptosis has a pivotal role in endometrial carcinogenesis, the effects of KSR1 in regulation of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis were investigated. KSR1 knock-down sensitized resistant endometrial cell lines to both TRAIL- and Fas-induced apoptosis. Sensitization to TRAIL and agonistic anti-Fas antibody was caused by down-regulation of FLIP (FLICE-inhibitory protein). Also investigated was the molecular mechanism by which KSR1 regulates FLIP protein levels. It was demonstrated that KSR1 small hairpin RNA did not affect FLIP transcription or degradation. Rather, FLIP down-regulation was caused by Fas-associated death domain protein-dependent inhibition of FLIP translation triggered after TRAIL stimulation in KSR1-silenced cells. Re-expression of heterologous KSR1 in cells with down-regulated endogenous KSR1 restored FLIP protein levels and TRAIL resistance. In conclusion, KSR1 regulates endometrial sensitivity to TRAIL by regulating FLIP levels.