Degree Of Phosphorylation Research Articles

P-Glycoprotein Modulation Facilitates the Selective Inhibition of Oxidative Phosphorylation in Alloreactive T Cells to Prevent Graft-Versus-Host Disease after Hematopoietic Stem Cell Transplant

T lymphocytes play a central role in many human immunologic disorders including both autoimmune and alloimmune diseases. In hematopoietic stem cell transplant (HSCT), acute graft-versus-host-disease (GVHD) is caused by an attack on the recipient's tissues from donor allogeneic T cells. Ex vivo application of phototherapy to selectively deplete GVHD-causing cells prior to transplant may prevent GVHD. However, none of the photosensitive agents in use today have demonstrated selectivity without significant toxicity occurring in resting cells. We have designed the first-in-class, novel photosensitizer 2-Se-Cl with the ability to accumulate in pathogenic T cells in proportion to degree of oxidative phosphorylation (OXPHOS). Unique to 2-Se-Cl is the ability to potently stimulate P-glycoprotein (P-pg). Enhanced P-gp activity promotes the efficient removal of photosensitizer not sequestered in mitochondria, and protects resting lymphocytes essential for antipathogen and antitumor responses. To confirm that 2-Se-Cl selectively depletes antigen-specific immune responses, human lymphocytes were cultured with staphylococcal enterotoxin B (SEB) for 72 hours. Cells were then pulsed with 2-Se-Cl and exposed to 5 J/cm2 of light, which resulted in the impedance of OXPHOS and induction of apoptosis in stimulated T cells. After photodepletion (PD), resting cells remained intact with the ability to respond to stimulation by Toxic Shock Syndrome Toxin-1 (TSST-1) but not SEB. To evaluate the selective depletion of alloimmune responses, a well-established complete mHC antigen-mismatched murine model of HSCT was employed. To prepare the PD - treated primed splenocytes, donor C57BL/6 splenocytes were cocultured for 5 days with irradiated Balb/c splenocytes, and then photodepleted. In vitro analysis of PD - treated primed splenocytes demonstrated selective depletion of antihost immune responses by CFSE dilution, with complete retention of third-party responses (C3H/HeJ mice). On the day of HSCT, recipient Balb/c mice were irradiated with 900 cGy, and received 5x106 T cell-depleted bone marrow cells accompanied by 5x106 PD - treated (treatment group) or untreated (control group) primed splenocytes, and then monitored for signs of GVHD according to an established mouse GVHD grading system. Five animals underwent HSCT in each group in 3 independent experiments. All mice died of acute GVHD after the addition of 5x106 untreated primed C57BL/6 cells at a median of 25 days after HSCT. In contrast, > 90% of mice that received the same number of PD - treated cells survived > 60 days without evidence of GVHD (see figure). Additionally, third-party C3H/Hej mice that received the same number of PD-treated cells died of GVHD, confirming the selective depletion of the alloimmune response for BalB/c by 2-Se-Cl. The high selectivity of this novel photosensitizer may have broad applications, including targeting the bioenergetics in alloimmune, autoimmune, and malignant T cells to provide alternative treatment options and improve clinical outcomes for patients with diseases such as GVHD, systemic lupus erythematosus, or peripheral T cell lymphoma. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

The anti-tumor NC1 domain of collagen XIX inhibits the FAK/ PI3K/Akt/mTOR signaling pathway through αvβ3 integrin interaction.

Type XIX collagen is a minor collagen associated with basement membranes. It was isolated for the first time in a human cDNA library from rhabdomyosarcoma and belongs to the FACITs family (Fibril Associated Collagens with Interrupted Triple Helices). Previously, we demonstrated that the NC1 domain of collagen XIX (NC1(XIX)) exerts anti-tumor properties on melanoma cells by inhibiting their migration and invasion. In the present work, we identified for the first time the integrin αvβ3 as a receptor of NC1(XIX). Moreover, we demonstrated that NC1(XIX) inhibits the FAK/PI3K/Akt/mTOR pathway, by decreasing the phosphorylation and activity of the major proteins involved in this pathway. On the other hand, NC1(XIX) induced an increase of GSK3β activity by decreasing its degree of phosphorylation. Treatments targeting this central signaling pathway in the development of melanoma are promising and new molecules should be developed. NC1(XIX) seems to have the potential for the design of new anti-cancer drugs.

Cytotoxic T Lymphocyte Antigen-4 Down-Regulates T Helper 1 Cells by Increasing Expression of Signal Transducer and Activator of Transcription 3 in Acute Graft-versus-Host Disease.

Numerous previous studies have suggested that cytotoxic T lymphocyte antigen-4 (CTLA-4) plays an important role in acute graft-versus-host disease (GVHD). How CTLA-4 acts in regulating acute GVHD remains unknown, however. In the present study, we found that, compared with healthy controls, CTLA-4 plasma and relative mRNA levels in patients with acute GVHD were initially decreased and then markedly elevated after 28days of treatment. CTLA-4 levels were higher in patients with grade I-II acute GVHD compared with those with grade III-IV acute GVHD both before and after treatment. Up-regulation of CTLA-4 significantly increased the luciferase activity and degree of phosphorylation of signal transducer and activator of transcription 3 (STAT3). Meanwhile, T cell activation was significantly inhibited, and levels of IFN-γ, IL-17, and IL-22 decreased. These findings suggest that CTLA-4 might be involved in the pathogenesis of acute GVHD, and may down-regulate T helper 1 cells by increasing STAT3 expression in acute GVHD.

Tolerance to the sedative and anxiolytic effects of diazepam is associated with different alterations of GABAA receptors in rat cerebral cortex

The clinical use of benzodiazepines is limited by the development of tolerance to their pharmacological effects. Tolerance to each of the pharmacological actions of benzodiazepines develops at different rates. The aim of this work was to investigate the mechanism of tolerance by performing behavioral tests in combination with biochemical studies. To this end, we administered prolonged treatments of diazepam to rats for 7 or 14days. Tolerance to the sedative effects of diazepam was detected by means of the open field test after the 7- and 14-day treatments, whereas tolerance to the anxiolytic actions of benzodiazepine manifested following only the 14-day treatment in the elevated plus maze. The cerebral cortical concentrations of diazepam did not decline after the diazepam treatments, indicating that tolerance was not due to alterations in pharmacokinetic factors. The uncoupling of GABA/benzodiazepine site interactions and an increase in the degree of phosphorylation of the GABAA receptor γ2 subunit at serine 327 in the cerebral cortex were produced by day 7 of diazepam treatment and persisted after 14days of exposure to benzodiazepine. Thus, these alterations could be part of the mechanism of tolerance to the sedative effects of diazepam. An increase in the percentage of α1-containing GABAA receptors in the cerebral cortex was observed following the 14-day treatment with diazepam but not the 7-day treatment, suggesting that tolerance to the anxiolytic effects is associated with a change in receptor subunit composition. The understanding of the molecular bases of tolerance could be important for the development of new drugs that maintain their efficacies over long-term treatments.

YangZheng XiaoJi exerts anti-tumour growth effects by antagonising the effects of HGF and its receptor, cMET, in human lung cancer cells.

BackgroundHepatocyte growth factor (HGF) is a cytokine that has a profound effect on cancer cells by stimulating migration and invasion and acting as an angiogenic factor. In lung cancer, the factor also plays a pivotal role and is linked to a poor outcome in patients. In particular, HGF is known to work in combination with EGF on lung cancer cells. In the present study, we investigated the effect of a traditional Chinese medicine reported in cancer therapies, namely YangZheng XiaoJi (YZXJ) on lung cancer and on HGF mediated migration and invasion of lung cancer cells.MethodsHuman lung cancer cells, SKMES1 and A549 were used in the study. An extract from the medicine was used. Cell migration was investigated using the EVOS and by ECIS. Cell–matrix adhesion and in vitro invasion were assessed. In vivo growth of lung cancer was tested using an in vivo xenograft tumour model and activation of the HGF receptor in lung tumours by an immunofluorescence method.ResultsBoth lung cancer cells increased their migration in response to HGF and responded to YZXJ by reducing their speed of migration. YZXJ markedly reduced the migration and in vitro invasiveness induced by HGF. It worked synergistically with PHA665752 and SU11274, HGF receptor inhibitors on the lung cancer cells both on HGF receptor activation and on cell functions. A combination of HGF and EGF resulted in a greater increase in cell migration, which was similarly inhibited by YZXJ, and in combination with the HGF receptor and EGF receptor inhibitors. In vivo, YZXJ reduced the rate of tumour growth and potentiated the effects of PHA665752 on tumour growth. It was further revealed that YZXJ significantly reduced the degree of phosphorylation of the HGF receptor in lung tumours.ConclusionYZXJ has a significant role in reducing the migration, invasion and in vivo tumour growth of lung cancer and acts to inhibit the migratory and invasive effects induced by HGF and indeed by HGF/EGF. This effect is likely attributed to the inhibition of the HGF receptor activation. These results indicate that YZXJ has a therapeutic role in lung cancer and that combined strategy with methods to block HGF and EGF should be considered.Electronic supplementary materialThe online version of this article (doi:10.1186/s12967-015-0639-1) contains supplementary material, which is available to authorized users.

Fine Tuning of a Type 1 Interferon Antagonist.

Type I interferons are multi-potent cytokines that serve as first line of defense against viruses and other pathogens, posses immunomudolatory functions and elicit a growth inhibitory response. In recent years it has been shown that interferons are also detrimental, for example in lupus, AIDS, tuberculosis and cognitive decline, highlighted the need to develop interferon antagonists. We have previously developed the antagonist IFN-1ant, with much reduced binding to the IFNAR1 receptor and enhanced binding to IFNAR2. Here, we further tune the IFN-1ant by producing three additional antagonists based on IFN-1ant but with altered activity profiles. We show that in all three cases the antiproliferative activity of interferons is blocked and the induction of gene transcription of immunomudolatory and antiproliferative associated genes are substantially decreased. Conversely, each of the new antagonists elicits a different degree of antiviral response, STAT phosphorylation and related gene induction. Two of the new antagonists promote decreased activity in relation to the original IFN-1ant, while one of them promotes increased activity. As we do not know the exact causes of the detrimental effects of IFNs, the four antagonists that were produced and analyzed provide the opportunity to investigate the extent of antagonistic and agonistic activity optimal for a given condition.

Platelet endothelial aggregation receptor-1: a novel modifier of neoangiogenesis.

Platelet endothelial aggregation receptor-1 (PEAR1) is a cell membrane protein, expressed on platelets and endothelial cells (ECs). PEAR1 sustains αIIbβ3 activation in aggregating platelets and attenuates megakaryopoiesis via controlling the degree of Akt phosphorylation. Its role in EC biology is unknown. The aim of this study was to determine the expression of PEAR1 in the human endothelium of various tissues and to investigate its role in ECs in vitro and in angiogenesis, using Pear1(-/-) mice. PEAR1 is present on the membrane and on filo- and lamellipodia of human cultured ECs, and its expression coincides with CD31 in various tissues. PEAR1 expression is variable in ECs of different origin. Lentiviral knockdown of PEAR1 in cultured ECs doubled EC proliferation and significantly stimulated EC migration, in turn enhancing in vitro tube formation on matrigel through the Akt/PTEN-dependent p21/CDC2 pathway. Even when physiological blood vessel formation was unaffected in Pear1(-/-) mice, neoangiogenesis in these mice was significantly increased both in a hind limb ischaemia ligation model [4.7-fold increase in capillary density in the ligated limb of Pear1(-/-) mice compared with ligated limbs in wild-type (WT) mice] and in a skin wound-healing model, resulting in a two-fold faster wound closure in Pear1(-/-) mice compared with WT littermates. We established an inverse correlation between endothelial PEAR1 expression and vascular assembly both in vitro and in vivo. These findings identify PEAR1 as a novel modifier of neoangiogenesis.

On the role of titin phosphorylation in the development of muscular atrophy

From our earlier experiments on the study of changes in titin content and the level of its phosphorylation in skeletal muscles, atrophied during space flight, hibernation, and also because of the development of alcohol-induced lesions it has been suggested that an increase in the degree of titin phosphorylation results in increased proteolytic degradation of this protein, that contributes to the development of skeletal muscle atrophy.

Src regulates cigarette smoke-induced ceramide generation via neutral sphingomyelinase 2 in the airway epithelium.

We previously demonstrated that the neutral sphingomyelinase (nSMase) 2 is the sole sphingomyelinase activated during cigarette smoke (CS)-induced oxidative stress of human airway epithelial cells, leading to ceramide generation and subsequent apoptosis of affected cells. Since then, we reported that nSMase2 is a phosphoprotein, the degree of enzymatic activity and stability of which are dictated by its degree of phosphorylation. Simultaneously, the non-receptor tyrosine kinase and proto-oncogene Src has increasingly become a target of interest in both smoking-related lung injury, such as chronic obstructive pulmonary disease, and lung cancer. Within this context, we tested and now present Src as a regulator of ceramide generation via modulation of nSMase2 phosphorylation and activity during CS-induced oxidative stress. Specifically, we provide evidence that Src activity is necessary for both CS-induced ceramide accumulation in vivo (129/Sv mice) and in vitro (human airway epithelial cells) and for nSMase2 activity during CS-induced oxidative stress. Moreover, because nSMase2 is exclusively phosphorylated on serines, we show that this occurs through Src-dependent activation of the serine/threonine kinase p38 mitogen-activated protein kinase during oxidative stress. Finally, we provide evidence that Src and p38 mitogen-activated protein kinase activities are critical for regulating nSMase2 phosphorylation. This study provides insights into a molecular target involved in smoking-related lung injury, represented here as nSMase2, and its modulation by the oncogene Src.

Effect of sialylation on EGFR phosphorylation and resistance to tyrosine kinase inhibition

Epidermal growth factor receptor (EGFR) is a heavily glycosylated transmembrane receptor tyrosine kinase. Upon EGF-binding, EGFR undergoes conformational changes to dimerize, resulting in kinase activation and autophosphorylation and downstream signaling. Tyrosine kinase inhibitors (TKIs) have been used to treat lung cancer by inhibiting EGFR phosphorylation. Previously, we demonstrated that EGFR sialylation suppresses its dimerization and phosphorylation. In this report, we further investigated the effect of sialylation on the phosphorylation profile of EGFR in TKI-sensitive and TKI-resistant cells. Sialylation was induced in cancer progression to inhibit the association of EGFR with EGF and the subsequent autophosphorylation. In the absence of EGF the TKI-resistant EGFR mutant (L858R/T790M) had a higher degree of sialylation and phosphorylation at Y1068, Y1086, and Y1173 than the TKI-sensitive EGFR. In addition, although sialylation in the TKI-resistant mutants suppresses EGFR tyrosine phosphorylation, with the most significant effect on the Y1173 site, the sialylation effect is not strong enough to stop cancer progression by inhibiting the phosphorylation of these three sites. These findings were supported further by the observation that the L858R/T790M EGFR mutant, when treated with sialidase or sialyltransferase inhibitor, showed an increase in tyrosine phosphorylation, and the sensitivity of the corresponding resistant lung cancer cells to gefitinib was reduced by desialylation and was enhanced by sialylation.

Starch phosphorylation in potato tubers is influenced by allelic variation in the genes encoding glucan water dikinase, starch branching enzymes I and II, and starch synthase III.

Starch phosphorylation is an important aspect of plant metabolism due to its role in starch degradation. Moreover, the degree of phosphorylation of starch determines its physicochemical properties and is therefore relevant for industrial uses of starch. Currently, starch is chemically phosphorylated to increase viscosity and paste stability. Potato cultivars with elevated starch phosphorylation would make this process unnecessary, thereby bestowing economic and environmental benefits. Starch phosphorylation is a complex trait which has been previously shown by antisense gene repression to be influenced by a number of genes including those involved in starch synthesis and degradation. We have used an association mapping approach to discover genetic markers associated with the degree of starch phosphorylation. A diverse collection of 193 potato lines was grown in replicated field trials, and the levels of starch phosphorylation at the C6 and C3 positions of the glucosyl residues were determined by mass spectrometry of hydrolyzed starch from tubers. In addition, the potato lines were genotyped by amplicon sequencing and microsatellite analysis, focusing on candidate genes known to be involved in starch synthesis. As potato is an autotetraploid, genotyping included determination of allele dosage. Significant associations (p < 0.001) were found with SNPs in the glucan water dikinase (GWD), starch branching enzyme I (SBEI) and the starch synthase III (SSIII) genes, and with a SSR allele in the SBEII gene. SNPs in the GWD gene were associated with C6 phosphorylation, whereas polymorphisms in the SBEI and SBEII genes were associated with both C6 and C3 phosphorylation and the SNP in the SSIII gene was associated with C3 phosphorylation. These allelic variants have potential as genetic markers for starch phosphorylation in potato.

A click approach to novel D-ring-substituted 16α-triazolylestrone derivatives and characterization of their antiproliferative properties.

A simple and efficient synthesis of novel, D-ring substituted estrone derivatives containing a 16α-triazolyl moiety is described. Two epimeric azido alcohols (16α-azido-17α-hydroxy and 16α-azido-17β-hydroxy) of estra-1,3,5(10)-triene-3-methyl ether were prepared, followed by copper(I)-catalyzed azide-alkyne cycloaddition with various terminal alkynes. The steroidal triazoles were obtained in high yields and their activities against three human cancer cell lines (HeLa, MCF7 and A431) were screened. The most effective analogs were submitted to additional experiments in order to characterize their antiproliferative properties. As evidenced by flow cytometry, the selected steroids induced a disturbance in the HeLa cell cycle in a concentration- and exposure-dependent manner, through an increase of the hypodiploid population (subG1) and a cell cycle arrest in the G2/M phase. A noncancerous human fibroblast cell line (MRC5) was used to determine the selectivities of these compounds. Fluorescent microscopy after Hoechst 33258 - propidium iodide (HOPI) double staining revealed nuclear condensation and disturbed cell membrane integrity. The enhanced activities of caspase-3 and caspase-9 without activation of caspase-8 in the treated cells indicated the activation of the intrinsic pathway of apoptosis. The levels of cell cycle regulators (CDK1, cyclin B1/B2 and cdc25B) were decreased and the ratio Bax/Bcl-2 was increased 24 h after the treatment of HeLa cells (determined at an mRNA level by means of an RT-PCR technique). Under the same conditions, two agents elicited substantially increased degrees of phosphorylation of stathmin, as evidenced by Western blotting. The presented results demonstrate that these steroids can be regarded as appropriate structural scaffolds for the design and synthesis of further steroid analogs as innovative drug candidates with good efficacy.

Dexmedetomidine directly increases tau phosphorylation.

Exposure to anesthetic agents has been linked to abnormal tau protein phosphorylation, an antecedent to the development of neurofibrillary tangles. This study evaluates the direct and indirect effects of dexmedetomidine. Primary culture of cortical neurons established from Sprague-Dawley (SD) rat embryos were exposed to dexmedetomidine for 1 or 6 hours, and the degree of tau phosphorylation at the AT8, AT180, and S396 sites was assessed by western blot analysis. To assess and compare their relative in vivo effects, the same agent was administered intravenously to 8 to 10 week old male SD rats and titrated to the loss of the righting reflex for 2 hours. After 1 hour of recovery, the rats were sacrificed and samples taken from the cortex and hippocampus were subjected to western blot and immunohistochemical analysis. The in vitro studies reviewed significant hyperphosphorylation only at the S396 site, and these changes have largely disappeared at 6 hours. With temperature maintenance, dexmedetomidine induced significant changes in hyperphosphorylation at the AT8 site in the cortex and hippocampus and at the AT180 in the hippocampus. The direct effect of anesthetic agents on fully differentiated cortical neurons is epitope-specific and short-lived. The in vivo effects are comparatively more complicated and depend not only on the phosphorylation site but the regions of the brain examined. These findings suggest that dexmedetomidine increases tau phosphorylation both in vitro and in vivo under normothermic conditions, and further studies are warranted to determine the long-term impact of this anesthetic on the tau pathology and even cognitive function.

Erythrocyte deformability and nitric oxide mobilization under pannexin-1 and PKC dependence

The erythrocyte adenosine triphosphate (ATP) is utilised for protein phosphorylation and exported through the pannexin 1 hemichannel (Px1) in the microcirculation. The physiological stimuli for ATP release are dependent of blood shear rate level and of the tissue oxygen content. The deoxygenated and oxygenated states of haemoglobin are respectively bound and unbound to N terminal domain of the protein band 3 of the erythrocyte membrane in dependence of its degree of phosphorylation. The protein tyrosine kinase (PTK) and protein tyrosine phosphatase (PTP) contribute to the phosphorylation degree of band 3 and are modulated by protein kinase C (PKC). Chelerythrine (Che) is a competitive inhibitor of ATP for PKC and a negative modulator of erythrocyte deformability. The aim of this study was to assess the mobilization of nitric oxide (NO) in erythrocyte in absence and presence of Che and Px1 inhibitor (carbenoxolone). Erythrocyte deformability was evaluated in presence of carbenoxolone (Carb). Regarding the effects observed in the erythrocyte by presence of Che or Carb, the values of efflux of NO and the concentration of nitrosogluthatione are similar and with no changes in relation to their absence. Px1inhibition by Carb 10 μM ameliorates the erythrocyte deformability at a shear force of 0.6 and 1.2 Pa. The PKC inhibitor shows similar effects to the Carb on the mobilization of nitric oxide in erythrocyte. The blockage of ATP release by Carb from erythrocytes suggests a possible benefit to develop in ischemia reperfusion or in inflammatory response where will be needed to rescue the excess of NO present and ameliorate the red blood cell deformability at low shear rates.

ETV6/ARG Oncoprotein Induces Autonomous Cell Growth By Enhancing c-Myc Expression through STAT5 Activation in the Acute Promyelocytic Leukemia Cell Line HT93A

Background: A fusion gene comprising ETS-variant gene 6 (ETV6) and ABL- related gene (ARG) has been identified in some patients with acute leukemia. Although the ETV6/ARG fusion gene is considered to contribute to the leukemogenesis, the detailed underlying mechanism is still unknown. Here, we investigated the role of ETV6/ARG fusion genes by exposing the HT93A cell line, which was established from a patient with relapsed acute promyelocytic leukemia carrying ETV6/ARG fusion gene, to the tyrosine kinase inhibitor, nilotinib.Material and Methods: HT93A cells were maintained in RPMI-1640 medium supplemented with 10% fetal bovine serum with or without nilotinib ± 50 ng/ml of granulocyte colony-stimulating factor (G-CSF). The cells were intracellularly stained anti-phosphorylated ARG (Y429), anti-phosphorylated STAT3 (Y705), anti-phosphorylated STAT5 (Y694), anti-p21/Waf1, anti-p27/Kip1, and anti-c-Myc polyclonal antibodies. Thereafter, protein expression and the degree of phosphorylation were evaluated with a flow cytometer. Cell growth was evaluated by trypan blue exclusion test, cell cycle analysis, and by intracellular staining with propidium iodide followed by flow cytometric analysis. Experiments were independently repeated at least thrice. Results shown are the mean ± standard deviation (SD) values. Data were analyzed using Student’s t-test, and p < 0.05 was considered statistically significant.Results: ARG was predominantly activated in HT93A cells and nilotinib treatment inhibited ARG phosphorylation. HT93A cells were sensitive to nilotinib, which inhibited cell growth in a dose-dependent manner for 96 h of incubation. Nilotinib treatment for 48 h significantly increased the probability of cells in the G0/G1 phase and decreased that in the S+G2/M phase. Further, nilotinib alone inhibited the expression of both phosphorylated STAT3 and STAT5. Moreover, nilotinib downregulated the expression levels of p21/Waf1 and c-Myc. However, p27/Kip expression level did not alter. Because the activation of STAT3 and/or STAT5 was assumed as the major pathway induced by ETV6/ARG oncoprotein, HT93A cells were coincubated with 50 ng/mL G-CSF in the presence or absence of nilotinib. After stimulation with G-CSF for 60 min, STAT5 was significantly phosphorylated in both nilotinib-treated and untreated cells; the expression level of phosphorylated STAT5 returned to the control level when treated with nilotinib and G-CSF together. In contrast, STAT3 phosphorylation was unaltered by G-CSF stimulation in nilotinib-treated and untreated cells. G-CSF alone had an insignificant effect on cell growth. The downregulation of the expression levels of p21/Waf1 and c-Myc by nilotinib was abolished by the combination of G-CSF. G-CSF had slight effect on HT93A cell cycle distribution; results of the combination therapy with nilotinib and G-CSF returned the cell cycle distribution to the control level.Conclusions: We demonstrated that ETV6/ARG inhibition by nilotinib abrogates autonomous cell growth via the downregulation of c-Myc through the inactivation of STAT5 but not of STAT3. Our data suggest that ETV6/ARG oncoprotein has a contributory effect for the autonomous cell growth and is a potential target in the treatment of leukemia. DisclosuresIriyama:Novartis: Honoraria; Kyowa Hakko Kirin: Honoraria. Hatta:Novartis: Honoraria; Kyowa Hakko Kirin: Honoraria. Takei:Novartis: Research Funding; Kyowa Hakko Kirin: Research Funding.

Ongoing Activation of the BCR, NFκB, and Proliferation Pathways in Mantle Cell Lymphoma: Direct in Vivo Evidence for the Role of the Lymph Node Microenvironnment

Mantle cell lymphoma (MCL) is a mature CD5+ B-cell malignancy that represents ~6% of non-Hodgkin’s lymphoma, and continues to have a high fatality rate approaching 65%. The high rate of clinical responses to the BTK inhibitor ibrutinib in this disease (ORR 68%, CR 23%) was unexpected, given the putative derivation of this malignancy from naïve B cells. Despite considerable advances in MCL research, evidence of BCR engagement in-vivo continues to be very limited. The location of such BCR engagement, and in-vivo consequences on tumor biology remain largely unknown.Using gene expression profiling (Affymetrix HU133 plus), we previously reported that MCL cells in the lymph node (LN) up-regulate BCR and NFκB target genes, and display higher expression of proliferation genes compared to the peripheral blood (PB). Here we present an extension of our initial report. Using flow cytometry, we measured levels of activated SYK, PLCγ, ERK, AKT, and P65 (RELA) in (CD5+ and CD19+ gated) MCL cells of 2 LN samples and 2 PB samples concomitantly collected from the same patients, and in a cohort of 16 PB samples. Consistent with the observed difference in BCR genes signature score (BCR score), we show that LN-resident MCL cells retain stronger kinases activity (SYK, PLCγ, ERK, AKT, and P65) as evidenced by their remarkably higher degree of phosphorylation when compared to their matched PB. A gene signature consists of a group of co-regulated genes whose combined expression pattern defines a distinct cell type or a cellular process. A gene signature score represents the average of the expression level of its genes. Moreover, levels of pSYK and pAKT strongly correlate with the BCR score (pSYKY348: r =.64, P <.02; pAKTT308: r =.53, P <.05), and levels of pP65 strongly correlate with the NFκB gene signature score (NFκB score) (r =.64, P<.02). pP65 levels also correlated with the BCR score (r =.54, P <.05) suggesting that the BCR pathway is responsible, at least in part, of NFκB activation. Furthermore, the BCR score in MCL whole LN biopsies (N = 30) strongly correlates with the chemokine CCL3 serum levels in the corresponding patients (r =.46; P =.008). CCL3 is one of the most strikingly upregulated genes upon BCR activation and while its role in MCL pathogenesis is unclear, it may serve as a biomarker of BCR activation. In concordance with an increased proliferation in the LN at the gene expression level, we detected a higher level of Ki67-positive MCL cells in the LN compared to PB. (P <.001). To test whether the proliferation signature is a surrogate for tumor proliferation, we studied the correlation between Ki67 positivity and proliferation score in both PB (by flow cytometry) and LN (IHC). We found that Ki67 and proliferation score strongly correlate with a correlation coefficient of 0.88 and 0.79 for PB and LN respectively (P <.0001 for both). The correlation between the BCR score and Ki67 was also high and significant (PB, r =.7, P =.006; LN, r =.39; P =.03)which suggests a role for BCR in driving tumor proliferation. To test ongoing pathway activation in MCL cell lines, mRNA from 10 MCL was profiled on Affymetrix HU133 arrays. BCR, NFκB, and proliferation scores were calculated. The BCR score was distinctly high in SP53 cell line, while the NFκB score was high in SP53 and JVM2, in the later this may be due to EBV infection. Higher baseline levels of activated BCR pathway kinases were observed in SP53 cells when compared to 3 other cell lines (Jeko, UPN1, and JVM2) that represent the spectrum of different levels of BCR and NFκB scores. The proliferation score was comparable in all cell lines. These 4 cell lines were tested against increasing concentration of ibrutinib for 48 and 72 h. Ibrutinib induced a greater growth inhibition in SP53 and JVM2, and resulted in apoptotic induction and cell cycle arrest. Ibrutinib however failed to induce apoptosis in Jeko and UPN1, and resulted only in cell cycle inhibition. Ibrutinib decreased ERK, PLCγ, and P65 phosphorylation in SP53 after 1h incubation.In conclusion, we demonstrated activation of the BCR, and NFκB pathways in-vivo that is preferentially localized in the LN microenvironment. A high degree of BCR activation correlates with increased tumor proliferation. We also identified SP53 as an MCL cell line with active BCR and NFκB signaling that is ibrutinib sensitive.Supported by the Intramural Research Program of NHLBI and NCI, NIH. We thank our patients for donating samples to make this research possible. DisclosuresWiestner:Pharmacyclics Inc.: Research Funding.

The benefits and limitations of reaction cell and sector field inductively coupled plasma mass spectrometry in the detection and quantification of phosphopeptides.

The phosphorylation of proteins is one of the most important post-translational modifications in nature. Knowledge of the quantity or degree of protein phosphorylation in biological samples is extremely important. A combination of liquid chromatography (LC) and inductively coupled plasma mass spectrometry (ICP-MS) allows the absolute and relative quantification of the phosphorus signal. A comparison between dynamic reaction cell quadrupole ICP-MS (DRC-Q-ICP-MS) and high-resolution sector field ICP-MS (SF-ICP-MS) in detecting signals of phosphorus-containing species using identical capillary LC (reversed-phase technology) and nebulizer settings was performed. A method to diminish the reversed-phase gradient-related signal instability in phosphorus detection with LC/ICP-MS applications was developed. Bis(4-nitrophenyl)phosphate (BNPP) was used as a standard to compare signal-to-noise ratios and limits of detection (LODs) between the two instrumental setups. The LOD reaches a value of 0.8 µg L(-1) when applying the DRC technology in Q-ICP-MS and an LOD of 0.09 µg L(-1) was found with the SF-ICP-MS setup. This BNPP standard was further used to compare the absolute quantification possibilities of phosphopeptides in these two setups. This one-to-one comparison of two interference-reducing ICP-MS instruments demonstrates that absolute quantification of individual LC-separated phosphopeptides is possible. However, based on the LOD values, SF-ICP-MS has a higher sensitivity in detecting phosphorus signals and thus is preferred in phosphopeptide analysis.

Conjugated bilirubin affects cytokine profiles in hepatitis A virus infection by modulating function of signal transducer and activator of transcription factors.

Hepatitis A virus (HAV) infection is the major cause of acute liver failure in paediatric patients. The clinical spectrum of infection is variable, and liver injury is determined by altered hepatic enzyme function and bilirubin concentration. We recently reported differences in cytokine profiles between distinct HAV-induced clinical courses, and bilirubin has been recognized as a potential immune-modulator. However, how bilirubin may affect cytokine profiles underlying the variability in the course of infection has not been determined. Herein, we used a transcription factor (TF) binding site identification approach to retrospectively analyse cytokine expression in HAV-infected children and to predict the entire set of TFs associated with the expression of specific cytokine profiles. The results suggested that modulation of the activity of signal transducers and activators of transcription proteins (STATs) may play a central role during HAV infection. This led us to compare the degree of STAT phosphorylation in peripheral blood lymphoid cells (PBLCs) from paediatric patients with distinct levels of conjugated bilirubin (CB). Low CB levels in sera were associated with increased STAT-1 and STAT-5 phosphorylation. A positive correlation was observed between the serum interleukin-6 (IL-6) content and CB values, whereas higher levels of CB correlated with reduced serum IL-8 values and with a reduction in the proportion of PBLCs positive for STAT-5 phosphorylation. When CB was used to stimulate patients' PBLCs in vitro, the levels of IL-6 and tumour necrosis factor-α were increased. The data showed that bilirubin plays a role in STAT function and affects cytokine profile expression during HAV infection.

Identification of isoform-specific dynamics in phosphorylation-dependent STAT5 dimerization by quantitative mass spectrometry and mathematical modeling.

STAT5A and STAT5B are important transcription factors that dimerize and transduce activation signals of cytokine receptors directly to the nucleus. A typical cytokine that mediates STAT5 activation is erythropoietin (Epo). Differential functions of STAT5A and STAT5B have been reported. However, the extent to which phosphorylated STAT5A and STAT5B (pSTAT5A, pSTAT5B) form homo- or heterodimers is not understood, nor is how this might influence the signal transmission to the nucleus. To study this, we designed a concept to investigate the isoform-specific dimerization behavior of pSTAT5A and pSTAT5B that comprises isoform-specific immunoprecipitation (IP), measurement of the degree of phosphorylation, and isoform ratio determination between STAT5A and STAT5B. For the main analytical method, we employed quantitative label-free and -based mass spectrometry. For the cellular model system, we used Epo receptor (EpoR)-expressing BaF3 cells (BaF3-EpoR) stimulated with Epo. Three hypotheses of dimer formation between pSTAT5A and pSTAT5B were used to explain the analytical results by a static mathematical model: formation of (i) homodimers only, (ii) heterodimers only, and (iii) random formation of homo- and heterodimers. The best agreement between experimental data and model simulations was found for the last case. Dynamics of cytoplasmic STAT5 dimerization could be explained by distinct nuclear import rates and individual nuclear retention for homo- and heterodimers of phosphorylated STAT5.

Tips on improving the efficiency of electrotransfer of target proteins from Phos-tag SDS-PAGE gel

The sensitivity of Western blotting analysis after Phos-tag SDS-PAGE is occasionally inferior to that after normal (Phos-tag-free) SDS-PAGE under similar experimental conditions, possibly as a result of inefficient electrotransfer from the Phos-tag gel to the blotting membrane. We therefore present tips on improving the efficiency of electrotransfer of proteins in semidry and wet-tank blotting. When model samples containing several standard phosphoproteins were subjected to semidry blotting, their electrotransfer efficiencies after Phos-tag SDS-PAGE were markedly inferior to those of their dephosphorylated counterparts in the same gel. This was ameliorated by immersing the electrophoresed Phos-tag gel in a transfer buffer containing 1 mM EDTA for 30 min before electroblotting. Similarly, phosphoproteomes in crude cell extracts were inefficiently transferred by semidry blotting, but the efficiencies of their electrotransfer were improved by pretreatment with EDTA. In contrast, the efficiencies of wet-tank blotting of the same samples were not dependent on the degree of phosphorylation, and the efficiencies of electrotransfer of all proteins from Phos-tag gels were similar to those from normal gels. In some cases involving the use of a Phos-tag gel, addition of 0.1% w/v of SDS to the transfer buffer significantly improved the electrotransfer.