A Pilot PT Scheme for External Assessment of Laboratory Performance in Testing Synthetic Opioid Compounds in Urine, Plasma, and Whole Blood

A proficiency testing (PT) scheme was prepared for laboratories engaged in bioanalytical testing for synthetic opioid compounds in urine, plasma, and whole blood. Samples were prepared using compounds included in the Opioid Certified Reference Material Kit (Opioid CRM Kit) developed by the U.S. Centers for Disease Control and Prevention. Laboratories received samples during a 2-year project with each year consisting of two PT events 6 months apart. In the first year (pilot test), participants included 10 public health laboratories throughout the United States. In the second year, the group of laboratories expanded to include clinical and forensic drug testing laboratories, and 12 additional participating labs joined the program. In Year 1, overall detection percentages for the compounds present in the PT samples were 95.5% in Event 1% and 97.2% in Event 2. There were 31 apparent false positives reported in Event 1 and four apparent false positives reported in Event 2. Carryover or contamination in laboratory analytical systems were found to be the most significant causes of the false positive results, and none of the laboratories that reported false positives in Event 1 did so in Event 2. In Year 2, overall detection percentages for the compounds present in the PT samples were 89.5% in Event 3% and 94.8% in Event 4. There was one apparent false positive reported in Event 3 and three apparent false positives reported in Event 4. Improvements in drug detection between the two PT events in each year demonstrated the benefit of PT schemes in identifying and addressing potential deficiencies in laboratory systems.

Myeloid-derived itaconate suppresses cytotoxic CD8+ T cells and promotes tumour growth

The tumour microenvironment possesses mechanisms that suppress anti-tumour immunity. Itaconate is a metabolite produced from the Krebs cycle intermediate cis-aconitate by the activity of immune-responsive gene 1 (IRG1). While it is known to be immune modulatory, the role of itaconate in anti-tumour immunity is unclear. Here, we demonstrate that myeloid-derived suppressor cells (MDSCs) secrete itaconate that can be taken up by CD8+ T cells and suppress their proliferation, cytokine production and cytolytic activity. Metabolite profiling, stable-isotope tracing and metabolite supplementation studies indicated that itaconate suppressed the biosynthesis of aspartate and serine/glycine in CD8+ T cells to attenuate their proliferation and function. Host deletion of Irg1 in female mice bearing allografted tumours resulted in decreased tumour growth, inhibited the immune-suppressive activities of MDSCs, promoted anti-tumour immunity of CD8+ T cells and enhanced the anti-tumour activity of anti-PD-1 antibody treatment. Furthermore, we found a significant negative correlation between IRG1 expression and response to PD-1 immune checkpoint blockade in patients with melanoma. Our findings not only reveal a previously unknown role of itaconate as an immune checkpoint metabolite secreted from MDSCs to suppress CD8+ T cells, but also establish IRG1 as a myeloid-selective target in immunometabolism whose inhibition promotes anti-tumour immunity and enhances the efficacy of immune checkpoint protein blockade.

Evaluation of self-administered antigen testing in a college setting

BACKGROUND

The objective of our investigation was to better understand barriers to implementation of self-administered antigen screening testing for SARS-CoV-2 at institutions of higher education (IHE).

METHODS

Using the Quidel QuickVue At-Home COVID-19 Test, 1347 IHE students and staff were asked to test twice weekly for seven weeks. We assessed seroconversion using baseline and endline serum specimens. Online surveys assessed acceptability.

RESULTS

Participants reported 9971 self-administered antigen test results. Among participants who were not antibody positive at baseline, the median number of tests reported was eight. Among 324 participants seronegative at baseline, with endline antibody results and ≥ 1 self-administered antigen test results, there were five COVID-19 infections; only one was detected by self-administered antigen test (sensitivity = 20%). Acceptability of self-administered antigen tests was high.

CONCLUSIONS

Twice-weekly serial self-administered antigen testing in a low prevalence period had low utility in this investigation. Issues of testing fatigue will be important to address in future testing strategies.

Heme oxygenase-1 mitigates liver injury and fibrosis via modulation of LNX1/Notch1 pathway in myeloid cells

Activation of resident macrophages (Mϕ) and hepatic stellate cells is a key event in chronic liver injury. Mice with heme oxygenase-1 (HO-1; Hmox1)-deficient Mϕ (LysM-Cre:Hmox1 ^flfl ) exhibit increased inflammation, periportal ductular reaction, and liver fibrosis following bile duct ligation (BDL)-induced liver injury and increased pericellular fibrosis in NASH model. RiboTag-based RNA-sequencing profiling of hepatic HO-1-deficient Mϕ revealed dysregulation of multiple genes involved in lipid and amino acid metabolism, regulation of oxidative stress, and extracellular matrix turnover. Among these genes, ligand of numb-protein X1 (LNX1) expression is strongly suppressed in HO-1-deficient Mϕ. Importantly, HO-1 and LNX1 were expressed by hepatic Mϕ in human biliary and nonbiliary end-stage cirrhosis. We found that Notch1 expression, a downstream target of LNX1, was increased in LysM-Cre:Hmox1 ^flfl mice. In HO-1-deficient Mϕ treated with heme, transient overexpression of LNX1 drives M2-like Mϕ polarization. In summary, we identified LNX1/Notch1 pathway as a downstream target of HO-1 in liver fibrosis.

Labile Heme and Heme Oxygenase-1 Maintain Tumor-Permissive Niche for Endometriosis-Associated Ovarian Cancer

Endometriosis, a painful gynecological condition accompanied by inflammation in women of reproductive age, is associated with an increased risk of ovarian cancer. We evaluated the role of peritoneal heme accumulated during menstrual cycling, as well as peritoneal and lesional macrophage phenotype, in promoting an oncogenic microenvironment. We quantified the heme-degrading enzyme, heme oxygenase-1 (HO-1, encoded by Hmox1) in normal peritoneum, endometriotic lesions and endometriosis-associated ovarian cancer (EAOC) of clear cell type (OCCC). HO-1 was expressed primarily in macrophages and increased in endometrioma and OCCC tissues relative to endometriosis and controls. Further, we compared cytokine expression profiles in peritoneal macrophages (PM) and peripheral blood mononuclear cells (PBMC) in women with endometriosis versus controls as a measure of a tumor-promoting environment in the peritoneum. We found elevated levels of HO-1 along with IL-10 and the pro-inflammatory cytokines (IL-1β, IL-16, IFNγ) in PM but not in PBMC from endometriosis patients. Using LysM-Cre:Hmox1flfl conditional knockout mice, we show that a deficiency of HO-1 in macrophages led to the suppression of growth of ID8 ovarian tumors implanted into the peritoneum. The restriction of ID8 ovarian tumor growth was associated with an increased number of Mac3+ macrophage and B cells in LysM-Cre:Hmox1flfl mice compared to controls. Functional experiments in ovarian cancer cell lines show that HO-1 is induced by heme. Low levels of exogenous heme promoted ovarian cancer colony growth in soft agar. Higher doses of heme led to slower cancer cell colony growth in soft agar and the induction of HO-1. These data suggest that perturbation of heme metabolism within the endometriotic niche and in cancer cells themselves may be an important factor that influences tumor initiation and growth.

Use of Diagnostic Ions for the Detection of Fentanyl Analogs in Human Matrices by LC-QTOF

To combat the ongoing opioid epidemic, our laboratory has developed and evaluated an approach to detect fentanyl analogs in urine and plasma by screening LC-QTOF MS/MS spectra for ions that are diagnostic of the core fentanyl structure. MS/MS data from a training set of 142 fentanyl analogs were used to select the four product ions and six neutral losses that together provided the most complete coverage (97.2%) of the training set compounds. Furthermore, using the diagnostic ion screen against a set of 49 fentanyl analogs not in the training set resulted in 95.9% coverage of those compounds. With this approach, lower reportable limits for fentanyl and a subset of fentanyl-related compounds range from 0.25 to 2.5 ng/mL in urine and 0.5 to 5.0 ng/mL in plasma. This innovative processing method was applied to evaluate simulated exposure samples of remifentanil and carfentanil in water and their metabolites remifentanil acid and norcarfentanil in urine. This flexible approach enables a way to detect emerging fentanyl analogs in clinical samples.

Therapeutic Repurposing of Biguanides in Cancer

Biguanides are a class of antidiabetic drugs that includes phenformin and metformin; however, the former was withdrawn from approval in many countries due to its toxicity. Findings from retrospective epidemiological studies in diabetic populations and preclinical laboratory models have demonstrated that biguanides possess antitumor activities that suggest their repurposing for cancer prevention and treatment. However, a better understanding of how these biguanides behave as antitumor agents is needed to guide their improved applications in cancer therapy, spurring increased interest in their pharmacology. Here, we present evidence for proposed mechanisms of action related to their antitumor activity, including their effects on central carbon metabolism in cancer cells and immune-modulating activity, and then review progress on biguanide repurposing in cancer therapeutics and the possible re-evaluation of phenformin as a cancer therapeutic agent.

SKAP2 is required for defense against K. pneumoniae infection and neutrophil respiratory burst

Klebsiella pneumoniae is a respiratory, blood, liver, and bladder pathogen of significant clinical concern. We show that the adaptor protein, SKAP2, is required for protection against K. pneumoniae (ATCC 43816) pulmonary infections. Skap2-/- mice had 100-fold higher bacterial burden when compared to wild-type and burden was controlled by SKAP2 expression in innate immune cells. Skap2-/- neutrophils and monocytes were present in infected lungs, and the neutrophils degranulated normally in response to K. pneumoniae infection in mice; however, K. pneumoniae-stimulated reactive oxygen species (ROS) production in vitro was abolished. K. pneumoniae-induced neutrophil ROS response required the activity of SFKs, Syk, Btk, PLCγ2, and PKC. The loss of SKAP2 significantly hindered the K. pneumoniae-induced phosphorylation of SFKs, Syk, and Pyk2 implicating SKAP2 as proximal to their activation in pathogen-signaling pathways. In conclusion, SKAP2-dependent signaling in neutrophils is essential for K. pneumoniae-activated ROS production and for promoting bacterial clearance during infection.

Klebsiella pneumoniae is a type of bacteria that can cause life-threatening infections – including pneumonia, blood stream infections, and urinary tract infections – in hospitalized patients. These infections can be difficult to treat because some K. pneumoniae are resistant to antibiotics. The bacteria are normally found in the human intestine, and they do not usually cause infections in healthy people. This implies that healthy people’s immune systems are better able to fend off K. pneumoniae infections; learning how could help scientists develop new ways to treat or prevent infections in hospitalized patients.

In healthy people, a type of immune cell called neutrophils are the first line of defense against bacterial infections. Several different proteins are needed to activate neutrophils, including a protein called SKAP2. But the role of this protein in fighting K. pneumoniae infections is not clear.

To find out what role SKAP2 plays in the defense against pneumonia caused by K. pneumoniae, Nguyen et al. compared infections in mice with and without the protein. Mice lacking SKAP2 in their white blood cells had more bacteria in their lungs than normal mice. The experiments showed that neutrophils from mice with SKAP2 produce a burst of chemicals called “reactive oxygen species”, which can kill bacteria. But neutrophils without the protein do not. Without SKAP2, several proteins that help produce reactive oxygen species do not work.

Understanding the role of SKAP2 in fighting infections may help scientists better understand the immune system. This could help clinicians to treat conditions that cause it to be hyperactive or ineffective. More studies are needed to determine if SKAP2 works the same way in human neutrophils and if it works against all types of K. pneumoniae. If it does, then scientists might be able use this information to develop therapies that help the immune system fight infections.

Rapid, Sensitive, and Accurate Point-of-Care Detection of Lethal Amatoxins in Urine

Globally, mushroom poisonings cause about 100 human deaths each year, with thousands of people requiring medical assistance. Dogs are also susceptible to mushroom poisonings and require medical assistance. Cyclopeptides, and more specifically amanitins (or amatoxins, here), are the mushroom poison that causes the majority of these deaths. Current methods (predominantly chromatographic, as well as antibody-based) of detecting amatoxins are time-consuming and require expensive equipment. In this work, we demonstrate the utility of the lateral flow immunoassay (LFIA) for the rapid detection of amatoxins in urine samples. The LFIA detects as little as 10 ng/mL of α-amanitin (α-AMA) or γ-AMA, and 100 ng/mL of β-AMA in urine matrices. To demonstrate application of this LFIA for urine analysis, this study examined fortified human urine samples and urine collected from exposed dogs. Urine is sampled directly without the need for any pretreatment, detection from urine is completed in 10 min, and the results are read by eye, without the need for specialized equipment. Analysis of both fortified human urine samples and urine samples collected from intoxicated dogs using the LFIA correlated well with liquid chromatography-mass spectrometry (LC-MS) methods.

Heme-Derived Metabolic Signals Dictate Immune Responses

Heme is one of the most abundant molecules in the body acting as the functional core of hemoglobin/myoglobin involved in the O₂/CO₂ carrying in the blood and tissues, redox enzymes and cytochromes in mitochondria. However, free heme is toxic and therefore its removal is a significant priority for the host. Heme is a well-established danger-associated molecular pattern (DAMP), which binds to toll-like receptor 4 (TLR4) to induce immune responses. Heme-derived metabolites including the bile pigments, biliverdin (BV) and bilirubin (BR), were first identified as toxic drivers of neonatal jaundice in 1800 but have only recently been appreciated as endogenous drivers of multiple signaling pathways involved in protection from oxidative stress and regulators of immune responses. The tissue concentration of heme, BV and BR is tightly controlled. Heme oxygenase-1 (HO-1, encoded by HMOX1) produces BV by heme degradation, while biliverdin reductase-A (BLVR-A) generates BR by the subsequent conversion of BV. BLVR-A is a fascinating protein that possesses a classical protein kinase domain, which is activated in response to BV binding to its enzymatic site and initiates the downstream mitogen-activated protein kinases (MAPK) and phosphatidylinositol 3-kinase (PI3K) pathways. This links BLVR-A activity to cell growth and survival pathways. BLVR-A also contains a bZip DNA binding domain and a nuclear export sequence (NES) and acts as a transcription factor to regulate the expression of immune modulatory genes. Here we will discuss the role of heme-related immune response and the potential for targeting the heme system for therapies directed toward hepatitis and cancer.

Application of the fentanyl analog screening kit toward the identification of emerging synthetic opioids in human plasma and urine by LC-QTOF

Human exposures to fentanyl analogs, which significantly contribute to the ongoing U.S. opioid overdose epidemic, can be confirmed through the analysis of clinical samples. Our laboratory has developed and evaluated a qualitative approach coupling liquid chromatography and quadrupole time-of-flight mass spectrometry (LC-QTOF) to address novel fentanyl analogs and related compounds using untargeted, data-dependent acquisition. Compound identification was accomplished by searching against a locally-established mass spectral library of 174 fentanyl analogs and metabolites. Currently, our library can identify 150 fentanyl-related compounds from the Fentanyl Analog Screening (FAS) Kit), plus an additional 25 fentanyl-related compounds from individual purchases. Plasma and urine samples fortified with fentanyl-related compounds were assessed to confirm the capabilities and intended use of this LC-QTOF method. For fentanyl, 8 fentanyl-related compounds and naloxone, lower reportable limits (LRL₁₀₀), defined as the lowest concentration with 100 % true positive rate (n = 12) within clinical samples, were evaluated and range from 0.5 ng/mL to 5.0 ng/mL for urine and 0.25 ng/mL to 2.5 ng/mL in plasma. The application of this high resolution mass spectrometry (HRMS) method enables the real-time detection of known and emerging synthetic opioids present in clinical samples.

The Clinical Application of Tumor Treating Fields Therapy in Glioblastoma

Glioblastoma is the most common and lethal form of brain cancer, with a median survival of 15 months after diagnosis and a 5 year survival rate of only 5% with current standard of care. Tumors often recur within 9 months following initial surgery, radiation and chemotherapy, at which point treatment options become limited. This highlights the pressing need for the development of better therapeutics to prolong survival and increase the quality of life for these patients. Tumor Treating Fields (TTFields) therapy was developed to take advantage of the effect of low frequency alternating electrical fields on cells for cancer therapy. TTFields have been demonstrated to disrupt cells during mitosis and slow tumor growth. There is also growing evidence that they act through stimulating immune responses within exposed tumors. The advantages of TTFields therapy include its noninvasive approach and increased quality of life compared to other treatment modalities such as cytotoxic chemotherapies. The Food and Drug Administration approved TTFields therapy for the treatment of recurrent glioblastoma in 2011 and for newly diagnosed glioblastoma in 2015. We report on the effects of TTFields during mitosis, the results of electric fields modeling, and proper transducer array placement. Our protocol outlines the clinical application of TTFields on a patient post-surgery, using the second-generation device.

Supplementing Cancer?

In this issue of Molecular Cell, Lin et al. (2018) report that chondroitin-4-sulfate, which is found in a common supplement meant to alleviate degenerative joint disorders, promotes the growth of BRAF V600E mutant melanoma. This study not only has implications for patient care but also sheds light on a novel mechanism for regulating phosphoinositide 3-kinase signaling.

Alternating Electric Fields Therapy for Malignant Gliomas: From Bench Observation to Clinical Reality

Alternating electric fields of intermediate frequencies, also known as Tumor Treating Fields (TTFields or TTF) is a novel anticancer treatment modality that disrupts tumor cell mitosis at the metaphase-anaphase transition, leading to mitotic catastrophe, aberrant mitotic exit, and/or cell death. It is realized through alteration of the cytokinetic cleavage furrow by interference of proteins possessing large dipole moments, like septin heterotrimer complex and α/β-tubulin, and that results in disordered membrane contraction and failed cytokinesis. Aberrant mitotic exit also elicits immunogenic cell death, which may potentiate an immune response against treated tumors. Notably, in patients with recurrent glioblastoma multiforme (GBM) a prospective clinical trial demonstrated comparable overall survival and progression-free survival after TTFields therapy and best physician's choice chemotherapy. Moreover, it was shown that in patients with newly diagnosed GBM initially treated with standard chemoradiotherapy with daily temozolomide (TMZ), adjuvant TTFields combined with TMZ offered better survival than adjuvant TMZ alone. Therefore, TTFields therapy can be appreciated as a standard treatment option in cases of intracranial malignant gliomas, whereas future studies should establish its optimal combination with other existing anticancer modalities, which may offer additional survival benefits for patients.

Abstract 1707: Tumor treating fields exert cellular and immunologic effects

While there is clear clinical evidence to support the therapeutic efficacy of low dose alternating electric fields (TTFields) in treating glioblastoma, their intracellular targets and mechanism of action remains poorly defined. Historically, TTFields have been thought to operate by inducing extensive plasma membrane blebbing during the entry into anaphase resulting in aberrant mitotic exit and cell death. However, we have found that cells exposed to TTFields exhibited increased granularity and evidence of endoplasmic reticulum stress and genotoxic stress suggesting other mechanisms to explain their clinical efficacy. Cells exposed to TTFields exhibited reductions in levels of culture media acidification and analysis of intracellular metabolism showed evidence for an increase in mitochondrial respiration and glutaminolysis pathway. Our previous analysis of data from the pivotal phase III EF-11 clinical trial showed that increased corticosteroid use was strongly correlated with poor outcomes in TTFields-treated patients, possibly by suppressing immune effector function required for to drive tumor regression. TTFields drives the cell surface expression of immune stimulatory stress marker proteins calreticulin, and the secretion of the Alarmin/DAMP protein, HMGB1 which are together suggest that TTFields can stimulate immunogenic cell death. Co-culture of bone marrow derived macrophages with TTFields-treated CT26 cells resulted in the up-regulation of cell surface activation markers in the macrophage population that was blocked by a monoclonal antibody directed against HMGB1. Further, supernatants from these co-cultures contained increased levels of pro-inflammatory cytokines and chemokines and a reduction of anti-inflammatory cytokines associated with the presence of the TTFields-treated cells relative to co-cultures containing naïve tumor cells. Further, in vivo, engrafted Lewis lung carcinoma tumors exhibited increased levels of granzyme positive cells following TTFields treatment. Together, these data suggest that TTFields affect cancer cells during interphase and this insult leads to alterations in cancer cell metabolism and increased tumor cell immunogenicity and thus act to drive increased immune recognition and tumor rejection. In patients, these effects are likely to be opposed by the immune suppressive functions within the tumor microenvironment and corticosteroid use. Therefore, this model of TTFields action may provide a therapeutically rational base to devise improved TTFields treatment strategies from.

Citation Format: Eric T. Wong, Joshua Timmons, Kenneth D. Swanson. Tumor treating fields exert cellular and immunologic effects [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1707.

Use of an Open Port Sampling Interface Coupled to Electrospray Ionization for the On-Line Analysis of Organic Aerosol Particles

A simple design for an open port sampling interface coupled to electrospray ionization (OPSI-ESI) is presented for the analysis of organic aerosols. The design uses minimal modifications to a Bruker electrospray (ESI) emitter to create a continuous flow, self-aspirating open port sampling interface. Considerations are presented for introducing aerosol to the open port sampling interface including aerosol gas flow and solvent flow rates. The device has been demonstrated for use with an aerosol of nicotine as well as aerosol formed in the pyrolysis of biomass. Upon comparison with extractive electrospray ionization (EESI), this device has similar sensitivity with increased reproducibility by nearly a factor of three. The device has the form factor of a standard Bruker/Agilent ESI emitter and can be used without any further instrument modifications. Graphical Abstract ᅟ.

ZNF143 protein is an important regulator of the myeloid transcription factor C/EBPα

The transcription factor C/EBPα is essential for myeloid differentiation and is frequently dysregulated in acute myeloid leukemia. Although studied extensively, the precise regulation of its gene by upstream factors has remained largely elusive. Here, we investigated its transcriptional activation during myeloid differentiation. We identified an evolutionarily conserved octameric sequence, CCCAGCAG, ∼100 bases upstream of the CEBPA transcription start site, and demonstrated through mutational analysis that this sequence is crucial for C/EBPα expression. This sequence is present in the genes encoding C/EBPα in humans, rodents, chickens, and frogs and is also present in the promoters of other C/EBP family members. We identified that ZNF143, the human homolog of the Xenopus transcriptional activator STAF, specifically binds to this 8-bp sequence to activate C/EBPα expression in myeloid cells through a mechanism that is distinct from that observed in liver cells and adipocytes. Altogether, our data suggest that ZNF143 plays an important role in the expression of C/EBPα in myeloid cells.

Metal Cationization Extractive Electrospray Ionization Mass Spectrometry of Compounds Containing Multiple Oxygens

Extractive electrospray ionization is an ambient ionization technique that allows real-time sampling of liquid samples, including organic aerosols. Similar to electrospray ionization, the composition of the electrospray solvent used in extractive electrospray ionization can easily be altered to form metal cationized molecules during ionization simply by adding a metal salt to the electrospray solvent. An increase in sensitivity is observed for some molecules that are lithium, sodium, or silver cationized compared with the protonated molecule formed in extractive electrospray ionization with an acid additive. Tandem mass spectrometry of metal cationized molecules can also significantly improve the ability to identify a compound. Tandem mass spectrometry of lithium and silver cationized molecules can result in an increase in the number and uniqueness of dissociation pathways relative to [M + H]⁺. These results highlight the potential for extractive electrospray ionization with metal cationization in analyzing complex aerosol mixtures. Graphical Abstract ᅟ.

Phenformin Inhibits Myeloid-Derived Suppressor Cells and Enhances the Anti-Tumor Activity of PD-1 Blockade in Melanoma

Biguanides, such as the diabetes therapeutics metformin and phenformin, have shown antitumor activity both in vitro and in vivo. However, their potential effects on the tumor microenvironment are largely unknown. Here we report that phenformin selectively inhibits granulocytic myeloid-derived suppressor cells in spleens of tumor-bearing mice and ex vivo. Phenformin induces production of reactive oxygen species in granulocytic myeloid-derived suppressor cells, whereas the antioxidant N-acetylcysteine attenuates the inhibitory effects of phenformin. Co-treatment of phenformin enhances the effect of anti-PD-1 antibody therapy on inhibiting tumor growth in the BRAF V600E/PTEN-null melanoma mouse model. Combination of phenformin and anti PD-1 cooperatively induces CD8⁺ T-cell infiltration and decreases levels of proteins that are critical for immune suppressive activities of myeloid-derived suppressor cells. Our findings show a selective, inhibitory effect of phenformin on granulocytic myeloid-derived suppressor cell-driven immune suppression and support that phenformin improves the anti-tumor activity of PD-1 blockade immunotherapy in melanoma.

Cabozantinib Eradicates Advanced Murine Prostate Cancer by Activating Antitumor Innate Immunity

Several kinase inhibitors that target aberrant signaling pathways in tumor cells have been deployed in cancer therapy. However, their impact on the tumor immune microenvironment remains poorly understood. The tyrosine kinase inhibitor cabozantinib showed striking responses in cancer clinical trial patients across several malignancies. Here, we show that cabozantinib rapidly eradicates invasive, poorly differentiated PTEN/p53-deficient murine prostate cancer. This was associated with enhanced release of neutrophil chemotactic factors from tumor cells, including CXCL12 and HMGB1, resulting in robust infiltration of neutrophils into the tumor. Critically, cabozantinib-induced tumor clearance in mice was abolished by antibody-mediated granulocyte depletion or HMGB1 neutralization or blockade of neutrophil chemotaxis with the CXCR4 inhibitor plerixafor. Collectively, these data demonstrate that cabozantinib triggers a neutrophil-mediated anticancer innate immune response, resulting in tumor clearance.Significance: This study is the first to demonstrate that a tyrosine kinase inhibitor can activate neutrophil-mediated antitumor innate immunity, resulting in invasive cancer clearance. Cancer Discov; 7(7); 750-65. ©2017 AACR.This article is highlighted in the In This Issue feature, p. 653.

β-Arrestin 1-dependent regulation of Rap2 is required for fMLP-stimulated chemotaxis in neutrophil-like HL-60 cells

β-Arrestins have emerged as key regulators of cytoskeletal rearrangement that are required for directed cell migration. Whereas it is known that β-arrestins are required for formyl-Met-Leu-Phe receptor (FPR) recycling, less is known about their role in regulating FPR-mediated neutrophil chemotaxis. Here, we show that β-arrestin 1 (ArrB1) coaccumulated with F-actin within the leading edge of neutrophil-like HL-60 cells during chemotaxis, and its knockdown resulted in markedly reduced migration within fMLP gradients. The small GTPase Ras-related protein 2 (Rap2) was found to bind ArrB1 under resting conditions but dissociated upon fMLP stimulation. The FPR-dependent activation of Rap2 required ArrB1 but was independent of Gα_i activity. Significantly, depletion of either ArrB1 or Rap2 resulted in reduced chemotaxis and defects in cellular repolarization within fMLP gradients. These data strongly suggest a model in which FPR is able to direct ArrB1 and other bound proteins that are required for lamellipodial extension to the leading edge in migrating neutrophils, thereby orientating and directing cell migration.

An Evidence-Based Review of Alternating Electric Fields Therapy for Malignant Gliomas

OPINION STATEMENT

Glioblastoma is a deadly disease and even aggressive neurosurgical resection followed by radiation and chemotherapy only extends patient survival to a median of 1.5 years. The challenge in treating this type of tumor stems from the rapid proliferation of the malignant glioma cells, the diffuse infiltrative nature of the disease, multiple activated signal transduction pathways within the tumor, development of resistant clones during treatment, the blood brain barrier that limits the delivery of drugs into the central nervous system, and the sensitivity of the brain to treatment effect. Therefore, new therapies that possess a unique mechanism of action are needed to treat this tumor. Recently, alternating electric fields, also known as tumor treating fields (TTFields), have been developed for the treatment of glioblastoma. TTFields use electromagnetic energy at an intermediate frequency of 200 kHz as a locoregional intervention and act to disrupt tumor cells as they undergo mitosis. In a phase III clinical trial for recurrent glioblastoma, TTFields were shown to have equivalent efficacy when compared to conventional chemotherapies, while lacking the typical side effects associated with chemotherapies. Furthermore, an interim analysis of a recent clinical trial in the upfront setting demonstrated superiority to standard of care cytotoxic chemotherapy, most likely because the subjects' tumors were at an earlier stage of clonal evolution, possessed less tumor-induced immunosuppression, or both. Therefore, it is likely that the efficacy of TTFields can be increased by combining it with other anti-cancer treatment modalities.

Dexamethasone exerts profound immunologic interference on treatment efficacy for recurrent glioblastoma

Background:

Patients with recurrent glioblastoma have a poor outcome. Data from the phase III registration trial comparing tumour-treating alternating electric fields (TTFields) vs chemotherapy provided a unique opportunity to study dexamethasone effects on patient outcome unencumbered by the confounding immune and myeloablative side effects of chemotherapy.

Methods:

Using an unsupervised binary partitioning algorithm, we segregated both cohorts of the trial based on the dexamethasone dose that yielded the greatest statistical difference in overall survival (OS). The results were validated in a separate cohort treated in a single institution with TTFields and their T lymphocytes were correlated with OS.

Results:

Patients who used dexamethasone doses >4.1 mg per day had a significant reduction in OS when compared with those who used ⩽4.1 mg per day, 4.8 vs 11.0 months respectively (χ²=34.6, P<0.0001) in the TTField-treated cohort and 6.0 vs 8.9 months respectively (χ²=10.0, P<0.0015) in the chemotherapy-treated cohort. In a single institution validation cohort treated with TTFields, the median OS of patients who used dexamethasone >4.1 mg per day was 3.2 months compared with those who used ⩽4.1 mg per day was 8.7 months (χ²=11.1, P=0.0009). There was a significant correlation between OS and T-lymphocyte counts.

Conclusions:

Dexamethasone exerted profound effects on both TTFields and chemotherapy efficacy resulting in lower patient OS. Therefore, global immunosuppression by dexamethasone likely interferes with immune functions that are necessary for the treatment of glioblastoma.

Tumor treating fields perturb the localization of septins and cause aberrant mitotic exit

The anti-tumor effects of chemotherapy and radiation are thought to be mediated by triggering G₁/S or G₂/M cell cycle checkpoints, while spindle poisons, such as paclitaxel, block metaphase exit by initiating the spindle assembly checkpoint. In contrast, we have found that 150 kilohertz (kHz) alternating electric fields, also known as Tumor Treating Fields (TTFields), perturbed cells at the transition from metaphase to anaphase. Cells exposed to the TTFields during mitosis showed normal progression to this point, but exhibited uncontrolled membrane blebbing that coincided with metaphase exit. The ability of such alternating electric fields to affect cellular physiology is likely to be dependent on their interactions with proteins possessing high dipole moments. The mitotic Septin complex consisting of Septin 2, 6 and 7, possesses a high calculated dipole moment of 2711 Debyes (D) and plays a central role in positioning the cytokinetic cleavage furrow, and governing its contraction during ingression. We showed that during anaphase, TTFields inhibited Septin localization to the anaphase spindle midline and cytokinetic furrow, as well as its association with microtubules during cell attachment and spreading on fibronectin. After aberrant metaphase exit as a consequence of TTFields exposure, cells exhibited aberrant nuclear architecture and signs of cellular stress including an overall decrease in cellular proliferation, followed by apoptosis that was strongly influenced by the p53 mutational status. Thus, TTFields are able to diminish cell proliferation by specifically perturbing key proteins involved in cell division, leading to mitotic catastrophe and subsequent cell death.

Clinical benefit in recurrent glioblastoma from adjuvant NovoTTF-100A and TCCC after temozolomide and bevacizumab failure: a preliminary observation

The NovoTTF-100A is a device that emits alternating electric fields and it is approved for the treatment of recurrent glioblastoma. It works by perturbing tumor cells during mitosis as they enter anaphase leading to aneuploidy, asymmetric chromosome segregation and cell death with evidence of increased immunogenicity. Clinical trial data have shown equivalent efficacy when compared to salvage chemotherapies in recurrent disease. Responders were found to have had a lower dexamethasone usage and a higher rate of prior low-grade histology. We treated a series of patients with NovoTTF-100A and bevacizumab alone (n = 34) or in combination with a regimen consisting of 6-thioguanine, lomustine, capecitabine, and celecoxib (TCCC) (n = 3). Compared to the former cohort, the latter cohort exhibited a trend for prolonged overall survival, median 4.1 (0.3–22.7) months versus 10.3 (7.7–13.6) months respectively (P = 0.0951), with one experiencing an objective response with a 50% reduction in tumor size on magnetic resonance imaging despite possessing a larger tumor size at baseline and more severe neurologic dysfunction than the median for either group. These observations illustrate the possibility of improving survival and achieving a response in patients with end-stage recurrent glioblastoma by biasing the tumor toward anti-tumor immunologic response with a combination of NovoTTF-100A and TCCC, as well as the continuation of bevacizumab in order to limit dexamethasone use due to its global immunosuppressive effect on the patient.

Response assessment of NovoTTF-100A versus best physician's choice chemotherapy in recurrent glioblastoma

The NovoTTF-100A device emits frequency-tuned alternating electric fields that interfere with tumor cell mitosis. In phase III trial for recurrent glioblastomas, NovoTTF-100A was shown to have equivalent efficacy and less toxicity when compared to Best Physician's Choice (BPC) chemotherapy. We analyzed the characteristics of responders and nonresponders in both cohorts to determine the characteristics of response and potential predictive factors. Tumor response and progression were determined by Macdonald criteria. Time to response, response duration, progression-free survival (PFS) ± Simon–Makuch correction, overall survival (OS), prognostic factors, and relative hazard rates were compared between responders and nonresponders. Median response duration was 7.3 versus 5.6 months for NovoTTF-100A and BPC chemotherapy, respectively (P = 0.0009). Five of 14 NovoTTF-100A responders but none of seven BPC responders had prior low-grade histology. Mean cumulative dexamethasone dose was 35.9 mg for responders versus 485.6 mg for nonresponders in the NovoTTF-100A cohort (P < 0.0001). Hazard analysis showed delayed tumor progression in responders compared to nonresponders. Simon–Makuch-adjusted PFS was longer in responders than in nonresponders treated with NovoTTF-100A (P = 0.0007) or BPC chemotherapy (P = 0.0222). Median OS was longer for responders than nonresponders treated with NovoTTF-100A (P < 0.0001) and BPC chemotherapy (P = 0.0235). Pearson analysis showed strong correlation between response and OS in NovoTTF-100A (P = 0.0002) but not in BPC cohort (P = 0.2900). Our results indicate that the response characteristics favor NovoTTF-100A and data on prior low-grade histology and dexamethasone suggest potential genetic and epigenetic determinants of NovoTTF-100A response.

Response assessment of novoTTF-100A versus best physician’s choice chemotherapy in recurrent glioblastoma

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Background: The NovoTTF-100A device emits tumor treating electric fields and was tested against Best Physician’s Choice (BPC) chemotherapy in a randomized phase III trial. We analyzed post hoc the characteristics of responders and non-responders in both cohorts. Methods: Macdonald criteria were used to determine tumor response and progression. Kaplan-Meier and Chi-squared statistics were computed for time to response, response duration, progression-free survival (PFS) with and without Simon-Makuch correction, and overall survival (OS). Prognostic factors were compared using the Wilconox rank sum test. Relative hazard rates for responders and non-responders were plotted. Results: The median response duration was 7.3 versus 5.6 months for NovoTTF-100A and BPC chemotherapy respectively (p=0.0009). Five of 14 NovoTTF-100A responders but none of 7 BPC responders had prior low-grade histology. The mean cumulative dexamethasone dose was 35.9 mg for responders versus 485.6 mg for non-responders in the NovoTTF-100A cohort (p<0.0001) as compared to 525.6 mg for responders and 431.0 mg for non-responders in the BPC cohort (p=0.9520). Hazard rate analysis showed delayed tumor progression in responders compared to non-responders. The Simon-Makuch conditional plot, which adjusted for unequal progression-free states, still showed longer PFS in responders than non-responders treated with NovoTTF-100A (χ2=11.5, P=0.0007) or BPC chemotherapy (χ2=5.2, P=0.0222). The median OS was 24.8 months for responders that is longer than 6.2 months for non-responders treated with NovoTTF-100A (χ2=25.7, P<0.0001). In the BPC chemotherapy cohort, the median OS was 20.0 months for responders and 6.8 months for non-responders (χ2=5.1, P=0.0235). There was strong Pearson correlation between response and OS in NovoTTF-100A (P<0.0002) but not in BPC cohort (P=0.2952). Conclusions: Response duration, adjusted Simon-Makuch PFS and OS favor NovoTTF-100A over BPC chemotherapy. Data on prior low-grade histology and dexamethasone dose suggest potential genetic and epigenetic determinants of NovoTTF-100A response. Clinical trial information: NCT00379470.

Macrophages require Skap2 and Sirpα for integrin-stimulated cytoskeletal rearrangement

Macrophages migrate to sites of insult during normal inflammatory responses. Integrins guide such migration, but the transmission of signals from integrins into the requisite cytoskeletal changes is poorly understood. We have discovered that the hematopoietic adaptor protein Skap2 is necessary for macrophage migration, chemotaxis, global actin reorganization and local actin reorganization upon integrin engagement. Binding of phosphatidylinositol [3,4,5]-triphosphate to the Skap2 pleckstrin-homology (PH) domain, which relieves its conformational auto-inhibition, is critical for this integrin-driven cytoskeletal response. Skap2 enables integrin-induced tyrosyl phosphorylation of Src-family kinases (SFKs), Adap, and Sirpα, establishing their roles as signaling partners in this process. Furthermore, macrophages lacking functional Sirpα unexpectedly have impaired local integrin-induced responses identical to those of Skap2(-/-) macrophages, and Skap2 requires Sirpα for its recruitment to engaged integrins and for coordinating downstream actin rearrangement. By revealing the positive-regulatory role of Sirpα in a Skap2-mediated mechanism connecting integrin engagement with cytoskeletal rearrangement, these data demonstrate that Sirpα is not exclusively immunoinhibitory, and illuminate previously unexplained observations implicating Skap2 and Sirpα in mouse models of inflammatory disease.

Mitosis interference of cancer cells during anaphase by electric field from NovoTTF-100A: An update

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Background: The NovoTTF-100A is a device that emits an alternating electric field (TTField) that kills mitotic cells and has been FDA-approved for the treatment of recurrent glioblastoma. Exposure to the TTField resulted in impaired cytokinesis and asymmetric chromosome segregation. To further elucidate its mechanism of action, we performed experiments using synchronized tumor cells and TTField-treated xenografts. Methods: Biochemical analysis of cell cycle-specific proteins, timelapse movies, and immunoflourescence microsopy were used to examine the effects of TTField on synchronized tumor cells. Xenografts treated with TTField were analyzed for the presence of phospho-Histone H3 and cell cycle-specific epitopes. Results: Cells exposed to TTField as they transited through M-phase exhibited persistence of phospho-Histone H3 while Securin levels decreased, suggesting that these cells transit through metaphase to anaphase but were delayed in mitotic exit. Immunoflourescence of treated cells showed evidence of impaired cytokinesis together with disordered separation of chromosomes from metaphase plates. Lagging chromosomes, dispersion of chromosomes, chromosomes decondensation in the absence of cytokinesis, and asymmetric chromosomal segregation were also observed in treated samples. The number of 4N cells increased following TTField exposure compared to parallel cultures that had entered the G1-phase of the cell cycle indicating a failure of mitosis. Exposed cells showed no detectable p53 induction indicating that cell death is achieved by a p53-independent mechanism. Lastly, immunostaining of treated xenografts for phospho-Histone H3 revealed the presence of significantly higher numbers of immunopositive mitotic figures compared to untreated samples. Conclusions: These data suggest that TTField exposure resulted in defective entry into anaphase and interfered with orderly exit from mitosis, a mechanism of mitotic perturbation that differs from currently used spindle poisons. NovoTTF-100A may therefore exhibit synergism when combined with conventional cancer treatments. Supported in part by a grant from NovoCure, Inc. and A Reason To Ride research fund.

Metabolomics of human cerebrospinal fluid identifies signatures of malignant glioma

Cerebrospinal fluid is routinely collected for the diagnosis and monitoring of patients with neurological malignancies. However, little is known as to how its constituents may change in a patient when presented with a malignant glioma. Here, we used a targeted mass-spectrometry based metabolomics platform using selected reaction monitoring with positive/negative switching and profiled the relative levels of over 124 polar metabolites present in patient cerebrospinal fluid. We analyzed the metabolic profiles from 10 patients presenting malignant gliomas and seven control patients that did not present malignancy to test whether a small sample size could provide statistically significant signatures. We carried out multiple unbiased forms of classification using a series of unsupervised techniques and identified metabolic signatures that distinguish malignant glioma patients from the control patients. One subtype identified contained metabolites enriched in citric acid cycle components. Newly diagnosed patients segregated into a different subtype and exhibited low levels of metabolites involved in tryptophan metabolism, which may indicate the absence of an inflammatory signature. Together our results provide the first global assessment of the polar metabolic composition in cerebrospinal fluid that accompanies malignancy, and demonstrate that data obtained from high throughput mass spectrometry technology may have suitable predictive capabilities for the identification of biomarkers and classification of neurological diseases.

Androgen Receptor Enhances p27 Degradation in Prostate Cancer Cells through Rapid and Selective TORC2 Activation

Androgen receptor (AR) plays a central role in prostate cancer (PCa) growth, with androgen deprivation or AR down-regulation causing cell-cycle arrest and accumulation of the p27 cyclin-dependent kinase inhibitor. The molecular basis for this AR regulation of cell-cycle progression remains unclear. Here we demonstrate that androgen can rapidly reduce p27 protein in PCa cells by increasing its proteasome-mediated degradation. This rapid androgen-stimulated p27 degradation was mediated by AKT through the phosphorylation of p27 T157. Significantly, androgen increased TORC2-mediated AKT S473 phosphorylation without affecting the PDK1-mediated AKT T308 phosphorylation or TORC1 activity. The TORC2 activation was further supported by enhanced mTOR/RICTOR association and increased phosphorylation of additional TORC2 substrates, SGK1 and PKCα. The androgen-stimulated nuclear translocation of AR was associated with markedly-increased nuclear SIN1, a critical component of TORC2. Finally, the androgen-mediated TORC2/AKT activation targets a subset of AKT substrates including p27 and FOXO1, but not PRAS40. This study reveals a pathway linking AR to a selective activation of TORC2, the subsequent activation of AKT, and phosphorylation of a discrete set of AKT substrates that regulate cellular proliferation and survival. These findings establish that TORC2 can function as a central regulator of growth in response to signals that are distinct from those regulating TORC1, and support efforts to target TORC2 for cancer therapy.

Evidence for an alternative glycolytic pathway in rapidly proliferating cells

Proliferating cells, including cancer cells, require altered metabolism to efficiently incorporate nutrients such as glucose into biomass. The M2 isoform of pyruvate kinase (PKM2) promotes the metabolism of glucose by aerobic glycolysis and contributes to anabolic metabolism. Paradoxically, decreased pyruvate kinase enzyme activity accompanies the expression of PKM2 in rapidly dividing cancer cells and tissues. We demonstrate that phosphoenolpyruvate (PEP), the substrate for pyruvate kinase in cells, can act as a phosphate donor in mammalian cells because PEP participates in the phosphorylation of the glycolytic enzyme phosphoglycerate mutase (PGAM1) in PKM2-expressing cells. We used mass spectrometry to show that the phosphate from PEP is transferred to the catalytic histidine (His11) on human PGAM1. This reaction occurred at physiological concentrations of PEP and produced pyruvate in the absence of PKM2 activity. The presence of histidine-phosphorylated PGAM1 correlated with the expression of PKM2 in cancer cell lines and tumor tissues. Thus, decreased pyruvate kinase activity in PKM2-expressing cells allows PEP-dependent histidine phosphorylation of PGAM1 and may provide an alternate glycolytic pathway that decouples adenosine triphosphate production from PEP-mediated phosphotransfer, allowing for the high rate of glycolysis to support the anabolic metabolism observed in many proliferating cells.

The melanoma-associated transmembrane glycoprotein Gpnmb controls trafficking of cellular debris for degradation and is essential for tissue repair

Kidney damage due to injury rarely resolves completely, and there are currently no therapies capable of promoting repair. In addition to understanding mechanisms by which tissues are damaged, illuminating mechanisms of repair and regeneration is also of great importance. Here we show that the melanoma-associated, transmembrane glycoprotein, Gpnmb, is up-regulated 15-fold following ischemic damage in kidney tissue and by more than 10-fold in macrophages and 3-fold in surviving epithelial cells. Gpnmb-expressing macrophages and epithelial cells were found to contain apoptotic bodies at 3 times the rate of nonexpressing cells. Either mutation of Gpnmb or ablation of inflammatory macrophages prevents normal repair of the kidney. Significantly, the kidneys from postischemic Gpnmb mutant mice exhibited a 5-fold increase in apoptotic cellular debris compared to wild-type mice. These mice also experienced an 85% increase in mortality following bilateral ischemic kidney. Finally, we demonstrate that Gpnmb is a phagocytic protein that is necessary for recruitment of the autophagy protein LC3 to the phagosome where these proteins are colocalized and for lysosomal fusion with the phagosome and hence bulk degradation of their content. Therefore, Gpnmb is a novel prorepair gene that is necessary for crosstalk between the macroautophagic degradation pathway and phagocytosis.

The Skap-hom dimerization and PH domains comprise a 3'-phosphoinositide-gated molecular switch

PH domains, by binding to phosphoinositides, often serve as membrane-targeting modules. Using crystallographic, biochemical, and cell biological approaches, we have uncovered a mechanism that the integrin-signaling adaptor Skap-hom uses to mediate cytoskeletal interactions. Skap-hom is a homodimer containing an N-terminal four-helix bundle dimerization domain, against which its two PH domains pack in a conformation incompatible with phosphoinositide binding. The isolated PH domains bind PI[3,4,5]P(3), and mutations targeting the dimerization domain or the PH domain's PI[3,4,5]P(3)-binding pocket prevent Skap-hom localization to ruffles. Targeting is retained when the PH domain is deleted or by combined mutation of the PI[3,4,5]P(3)-binding pocket and the PH/dimerization domain interface. Thus, the dimerization and PH domain form a PI[3,4,5]P(3)-responsive molecular switch that controls Skap-hom function.

SOS1 mutations are rare in human malignancies: implications for Noonan Syndrome patients

Germ line gain-of-function mutations in several members of the RAS/ERK pathway, including PTPN11, KRAS, and RAF1, cause the autosomal dominant genetic disorder Noonan Syndrome (NS). NS patients are at increased risk of leukemia/myeloproliferative disease and possibly some solid tumors, such as neuroblastoma. Recently, SOS1 gain of function mutations have also been shown to cause NS. Somatic PTPN11, KRAS, and RAF1 mutations occur (although at different frequencies) in a variety of sporadic neoplasms, but whether SOS1 mutations are associated with human cancer has not been evaluated. We sequenced DNA from a total of 810 primary malignancies, including pancreatic, lung, breast, and colon carcinomas, and acute myelogenous leukemia, as well as several neuroblastoma cell lines. From this large, diverse series, missense SOS1 mutations were identified in a single pancreatic tumor, one lung adenocarcinoma, and a T-cell acute lymphoblastic leukemia cell line. Our findings suggest that SOS1 is not a significant human oncogene in most cancers. Furthermore, NS patients with SOS1 mutations may not be at increased risk of developing cancer.

Germline gain-of-function mutations in SOS1 cause Noonan syndrome

Noonan syndrome, the most common single-gene cause of congenital heart disease, is characterized by short stature, characteristic facies, learning problems and leukemia predisposition. Gain-of-function mutations in PTPN11, encoding the tyrosine phosphatase SHP2, cause approximately 50% of Noonan syndrome cases. SHP2 is required for RAS-ERK MAP kinase (MAPK) cascade activation, and Noonan syndrome mutants enhance ERK activation ex vivo and in mice. KRAS mutations account for <5% of cases of Noonan syndrome, but the gene(s) responsible for the remainder are unknown. We identified missense mutations in SOS1, which encodes an essential RAS guanine nucleotide-exchange factor (RAS-GEF), in approximately 20% of cases of Noonan syndrome without PTPN11 mutation. The prevalence of specific cardiac defects differs in SOS1 mutation-associated Noonan syndrome. Noonan syndrome-associated SOS1 mutations are hypermorphs encoding products that enhance RAS and ERK activation. Our results identify SOS1 mutants as a major cause of Noonan syndrome, representing the first example of activating GEF mutations associated with human disease and providing new insights into RAS-GEF regulation.

PTPN11 (Shp2) mutations in LEOPARD syndrome have dominant negative, not activating, effects

Multiple lentigines/LEOPARD syndrome (LS) is a rare, autosomal dominant disorder characterized by Lentigines, Electrocardiogram abnormalities, Ocular hypertelorism, Pulmonic valvular stenosis, Abnormalities of genitalia, Retardation of growth, and Deafness. Like the more common Noonan syndrome (NS), LS is caused by germ line missense mutations in PTPN11, encoding the protein-tyrosine phosphatase Shp2. Enzymologic, structural, cell biological, and mouse genetic studies indicate that NS is caused by gain-of-function PTPN11 mutations. Because NS and LS share several features, LS has been viewed as an NS variant. We examined a panel of LS mutants, including the two most common alleles. Surprisingly, we found that in marked contrast to NS, LS mutants are catalytically defective and act as dominant negative mutations that interfere with growth factor/Erk-mitogen-activated protein kinase-mediated signaling. Molecular modeling and biochemical studies suggest that LS mutations contort the Shp2 catalytic domain and result in open, inactive forms of Shp2. Our results establish that the pathogenesis of LS and NS is distinct and suggest that these disorders should be distinguished by mutational analysis rather than clinical presentation.

Regulation of in vitro and in vivo immune functions by the cytosolic adaptor protein SKAP-HOM

SKAP-HOM is a cytosolic adaptor protein representing a specific substrate for the Src family protein tyrosine kinase Fyn. Previously, several groups have provided experimental evidence that SKAP-HOM (most likely in cooperation with the cytosolic adaptor protein ADAP) is involved in regulating leukocyte adhesion. To further assess the physiological role of SKAP-HOM, we investigated the immune system of SKAP-HOM-deficient mice. Our data show that T-cell responses towards a variety of stimuli are unaffected in the absence of SKAP-HOM. Similarly, B-cell receptor (BCR)-mediated total tyrosine phosphorylation and phosphorylation of Erk, p38, and JNK, as well as immunoreceptor-mediated Ca(2+) responses, are normal in SKAP-HOM(-/-) animals. However, despite apparently normal membrane-proximal signaling events, BCR-mediated proliferation is strongly attenuated in the absence of SKAP-HOM(-/-). In addition, adhesion of activated B cells to fibronectin (a ligand for beta1 integrins) as well as to ICAM-1 (a ligand for beta2 integrins) is strongly reduced. In vivo, the loss of SKAP-HOM results in a less severe clinical course of experimental autoimmune encephalomyelitis following immunization of mice with the encephalitogenic peptide of MOG (myelin oligodendrocyte glycoprotein). This is accompanied by strongly reduced serum levels of MOG-specific antibodies and lower MOG-specific T-cell responses. In summary, our data suggest that SKAP-HOM is required for proper activation of the immune system, likely by regulating the cross-talk between immunoreceptors and integrins.

AR and ER interaction with a p21-activated kinase (PAK6)

A human protein termed p21-activated kinase 6 (PAK6), based on homology to the PAK family of serine/threonine kinases, was cloned as an AR interacting protein. PAK6 was a 75-kDa protein with a predicted N-terminal Cdc42/Rac interactive binding domain and a C-terminal kinase domain. PAK6 bound strongly to GTP-Cdc42 and weakly to GTP-Rac. In contrast to most PAKs, kinase activity was not stimulated by Cdc42 or Rac, but could be stimulated by AR binding. PAK6 interacted with the intact AR in a mammalian one-hybrid assay and bound in vitro, without ligand, to the hinge region between the AR DNA- and ligand-binding domains. PAK6 also bound to the ERalpha, and binding was enhanced by 4-hydroxytamoxifen. AR and ERalpha transcriptional activities were inhibited by PAK6 in transient transfections with episomal and integrated reporter genes. AR inhibition was not reversed by transfection with an activated Cdc42 mutant, Cdc42V12, which by itself also inhibited AR transactivation. Epitope-tagged PAK6 was primarily cytoplasmic in the absence or presence of AR and hormone. PAK6 transcripts were expressed most highly in brain and testis, with lower levels in multiple tissues including prostate and breast. PAK6 interaction provides a mechanism for cross-talk between steroid hormone receptors and Cdc42-mediated signal transduction pathways and could contribute to the effects of tamoxifen in breast cancer and in other tissues.

SHPS-1 is a scaffold for assembling distinct adhesion-regulated multi-protein complexes in macrophages

Inhibitory immunoreceptors downregulate signaling by recruiting Src homology 2 (SH2) domain-containing tyrosine and/or lipid phosphatases to activating receptor complexes [1]. There are indications that some inhibitory receptors might also perform other functions [2] [3]. In adherent macrophages, two inhibitory receptors, SHPS-1 and PIR-B, are the major proteins binding to the tyrosine phosphatase SHP-1. SHPS-1 also associates with two tyrosine-phosphorylated proteins (pp55 and pp130) and a protein tyrosine kinase [4]. Here, we have identified pp55 and pp130 as the adaptor molecules SKAP55hom/R (Src-kinase-associated protein of 55 kDa homologue) and FYB/SLAP-130 (Fyn-binding protein/SLP-76-associated protein of 130 kDa), respectively, and the tyrosine kinase activity as PYK2. Two distinct SHPS-1 complexes were formed, one containing SKAP55hom/R and FYB/SLAP-130, and the other containing PYK2. Recruitment of FYB/SLAP-130 to SHPS-1 required SKAP55hom/R, whereas PYK2 associated with SHPS-1 independently. Formation of both complexes was independent of SHP-1 and tyrosine phosphorylation of SHPS-1. Finally, tyrosine phosphorylation of members of the SHPS-1 complexes was regulated by integrin-mediated adhesion. Thus, SHPS-1 provides a scaffold for the assembly of multi-protein complexes that might both transmit adhesion-regulated signals and help terminate such signals through SHP-1-directed dephosphorylation. Other inhibitory immunoreceptors might have similar scaffold-like functions.

Transcription factor phosphorylation by pp90(rsk2). Identification of Fos kinase and NGFI-B kinase I as pp90(rsk2)

The in vitro phosphorylation of transcription factors by growth factor-activated protein kinases has resulted in the discovery of a number of activities whose identities and relationships to one another are unclear. Fos kinase is a growth factor-stimulated serine/threonine protein kinase that phosphorylates c-Fos at serine 362 within the carboxyl-terminal regulatory domain. Fos kinase activation is dependent on p21(ras) and mitogen-activated protein kinase/ERK kinase kinase (MEK) activity and is independent of phosphatidylinositol 3-kinase activity. We have purified Fos kinase by affinity chromatography using the Sepharose-linked protein kinase inhibitor, bisindolylmaleimide (BIM). Fos kinase has an apparent molecular mass of 88 kDa, and mass spectrophotometric analysis of the isolated protein showed that it produced tryptic fragments identical to those predicted for pp90(rsk2). Fos kinase isolated from nerve growth factor-stimulated PC12 cells is indistinguishable from NGFI-B kinase I, based on their chromatographic behavior, substrate specificities, and relative sensitivity to BIM. Furthermore, we have distinguished Fos kinase from calcium/cAMP response element-binding protein (CREB) kinase. Therefore, Fos kinase and NGFI-B kinase I and pp90(rsk2) represent the same protein kinase species. Moreover, we report that pp90(rsk2) exists within nerve growth factor-stimulated PC12 cells as two chromatographically and immunologically distinct species. Finally, we demonstrate that CREB kinase is distinct from pp90(rsk2).

ATP-stimulated activation of the mitogen-activated protein kinases through ionotrophic P2X2 purinoreceptors in PC12 cells. Difference in purinoreceptor sensitivity in two PC12 cell lines

Extracellular purine nucleotides elicit a diverse range of biological responses through binding to specific cell surface receptors. The ionotrophic P2X subclass of purinoreceptors respond to ATP by stimulation of calcium ion permeability; however, it is unknown how P2X purinoreceptor activation is linked to intracellular signaling pathways. We report that stimulation of PC12 cells with ATP results in the activation of the mitogen-activated protein (MAP) kinases ERK1 and ERK2 and was wholly dependent upon extracellular calcium ions. Treatment of the cells with adenosine, AMP, ADP, UTP, or alpha,beta-methylene ATP was without effect; however, MAP kinase activation was abolished by pretreatment with suramin and reactive blue 2. The calcium-activated tyrosine kinase, Pyk2, acts as an upstream regulator of the MAP kinases and became tyrosine phosphorylated following treatment of the cells with ATP. We have ruled out the involvement of depolarization-mediated calcium influx because specific blockers of voltage-gated calcium channels did not affect MAP kinase activation. These data provide direct evidence that calcium influx through P2X2 receptors results in the activation of the MAP kinase cascade. Finally, we demonstrate that a different line of PC12 cells respond to ATP through P2Y2 purinoreceptors, providing an explanation for the conflicting findings of purine nucleotide responsiveness in PC12 cells.

Isolation and characterization of a nerve growth factor-regulated Fos kinase from PC12 cells

Nerve growth factor (NGF) treatment of PC12 cells activates a protein kinase that phosphorylates c-Fos protein at a site near its C terminus, as well as a peptide corresponding to a C-terminal region of c-Fos (Taylor, L. K., Marshak, D. R., and Landreth, G. E. (1993) Proc. Natl. Acad. Sci. U. S. A. 90, 368-372). This serine/threonine kinase, termed Fos kinase, has been purified > 24,000-fold through five column steps to near homogeneity and is shown to be a 37-kDa protein as determined by SDS-polyacrylamide gel electrophoresis (PAGE) with a pI = 6.0. Fos kinase is distinguishable from previously characterized NGF-regulated kinases by its chromatographic behavior, its response to specific kinase inhibitors, and its substrate specificity. The concentration of NGF required to activate Fos kinase is consistent with signaling from the high affinity NGF receptor. Fos kinase phosphorylates c-Fos at its C terminus as indicated by competitive inhibition with a peptide corresponding to C-terminal phosphorylation sites and lack of phosphorylation of a C-terminal deletion mutant of c-Fos. Hyperphosphorylation of c-Fos in vivo, as detected by reduced electrophoretic mobility of c-Fos, is induced by the same ligands which activate Fos kinase. Moreover, Fos kinase phosphorylation of c-Fos in vitro results in a similar electrophoretic mobility shift, demonstrating that Fos kinase may be responsible for growth factor-stimulated alterations in mobility on SDS-PAGE and phosphorylation of this transcription factor. The ability of this unique growth factor-responsive kinase to phosphorylate c-Fos at its C terminus, a region essential for the transrepressive properties of c-Fos, suggests that Fos kinase may play a role in the regulation of the transcriptional repressive activity of c-Fos.