Diagnostic and Prognostic Value of 11C-Methionine PET for Nonenhancing Gliomas.

BACKGROUND AND PURPOSE: Noninvasive radiologic evaluation of glioma can facilitate correct diagnosis and detection of malignant transformation. Although positron-emission tomography is considered valuable in the care of patients with gliomas, (18)F-fluorodeoxyglucose and (11)C-methionine have reportedly shown ambiguous results in terms of grading and prognostication. The present study compared the diagnostic and prognostic capabilities of diffusion tensor imaging, FDG, and (11)C-methionine PET in nonenhancing gliomas. MATERIALS AND METHODS: Thirty-five consecutive newly diagnosed, histologically confirmed nonenhancing gliomas that underwent both FDG and (11)C-methionine PET were retrospectively investigated (23 grade II and 12 grade III gliomas). Apparent diffusion coefficient, fractional anisotropy, and tumor-to-normal tissue ratios of both FDG and (11)C-methionine PET were compared between grade II and III gliomas. Prognostic values of these parameters were also tested by using progression-free survival. RESULTS: Grade III gliomas showed significantly higher average tumor-to-normal tissue and maximum tumor2-to-normal tissue than grade II gliomas in (11)C-methionine (P = .013, P = .0017, respectively), but not in FDG-PET imaging. There was no significant difference in average ADC, minimum ADC, average fractional anisotropy, and maximum fractional anisotropy. (11)C-methionine PET maximum tumor-to-normal tissue ratio of 2.0 was most suitable for detecting grade III gliomas among nonenhancing gliomas (sensitivity, 83.3%; specificity, 73.9%). Among patients not receiving any adjuvant therapy, median progression-free survival was 64.2 ± 7.2 months in patients with maximum tumor-to-normal tissue ratio of <2.0 for (11)C-methionine PET and 18.6 ± 6.9 months in patients with maximum tumor-to-normal tissue ratio of >2.0 (P = .0044). CONCLUSIONS: (11)C-methionine PET holds promise for World Health Organization grading and could offer a prognostic imaging biomarker for nonenhancing gliomas.

Recurrent mutations of CD79B and MYD88 are the hallmark of primary central nervous system lymphomas.

AIMS: Primary central nervous system lymphoma (PCNSL) manifest aggressive clinical behaviour and have poor prognosis. Although constitutive activation of the nuclear factor-κB (NF-κB) pathway has been documented, knowledge about the genetic alterations leading to the impairment of the NF-κB pathway in PCNSLs is still limited. This study was aimed to unravel the underlying genetic profiles of PCNSL. METHODS: We conducted the systematic sequencing of 21 genes relevant to the NF-κB signalling network for 71 PCNSLs as well as the pyrosequencing of CD79B and MYD88 mutation hotspots in a further 35 PCNSLs and 46 glioblastomas (GBMs) for validation. RESULTS: The results showed that 68 out of 71 PCNSLs had mutations in the NF-κB gene network, most commonly affecting CD79B (83%), MYD88 (76%), TBL1XR1 (23%), PRDM1 (20%) and CREBBP1 (20%). These mutations, particularly CD79B and MYD88, frequently coincided within each tumour in various combinations, simultaneously affecting diverse pathways within the network. No GBMs had hotspot mutation of CD79B Y196 and MYD88 L265. CONCLUSIONS: The prevalence of CD79B and MYD88 mutations in PCNSLs was considerably higher than reported in systemic diffuse large B-cell lymphomas. This observation could reflect the paucity of antigen stimuli from the immune system in the central nervous system (CNS) and the necessity to substitute them by the constitutive activation of CD79B and MYD88 that would initiate the signalling cascades. These hotspot mutations may serve as a genetic hallmark for PCNSL serving as a genetic marker for diagnose and potential targets for molecular therapy.

Pituitary-Targeted Dynamic Contrast-Enhanced Multisection CT for Detecting MR Imaging-Occult Functional Pituitary Microadenoma.

BACKGROUND AND PURPOSE: Although resection of a tumor by trans-sphenoidal surgery is considered the criterion standard for successful surgical treatment of functional pituitary microadenoma, MR imaging occasionally fails to visualize and identify the tumor and supplementary imaging modalities are necessary. We tested the possibility of dynamic contrast-enhanced multisection CT of the pituitary gland accompanying image reconstruction of contrast agent dynamics to identify the localizations of microadenomas and compared the diagnostic performance with conventional pituitary-targeted MR imaging. MATERIALS AND METHODS: Twenty-eight patients with surgically confirmed functional pituitary microadenomas (including growth hormone-, adrenocorticotropic hormone-, and prolactin-secreting adenomas) who underwent pituitary-targeted dynamic contrast-enhanced multisection CT were retrospectively investigated. We undertook image reconstruction of the dynamics of the contrast agent around the pituitary gland in a voxelwise manner, visualizing any abnormality and enabling qualification of contrast dynamics within the tumor. RESULTS: Fifteen cases were correctly diagnosed by MR imaging, while dynamic contrast-enhanced multisection CT correctly diagnosed 26 cases. The accuracy of localization was markedly better for adrenocorticotropic hormone-secreting microadenomas, increasing from 32% on MR imaging to 85% by dynamic contrast-enhanced multisection CT. Compared with the normal pituitary gland, adrenocorticotropic hormone-secreting adenoma showed the least difference in contrast enhancement of the different functional microadenomas. Images acquired at 45-60 seconds after contrast agent injection showed the largest difference in contrast enhancement between an adenoma and the normal pituitary gland. CONCLUSIONS: Dynamic contrast-enhanced multisection CT combined with image reconstruction of the contrast-enhanced dynamics holds promise in detecting MR imaging-occult pituitary microadenomas.

Overexpression of nucleostemin contributes to an advanced malignant phenotype and a poor prognosis in oral squamous cell carcinoma.

BACKGROUND: Nucleostemin (NS) is essential for the maintenance of stem cell properties, the functions of which remain poorly understood in cancer cells. The purpose of this study was to explore the impact of NS on malignancy and its clinical significance in oral squamous cell carcinoma (OSCC) patients. METHODS: We investigated the effects of NS on the proliferation and invasion of OSCC using NS-overexpressing or -knockdown OSCC cells. We assessed the activation of the STAT3 (signal transducer and activator of transcription 3) signalling pathway and the downstream targets in the cells with different expression levels of NS. An immunohistochemical analysis of NS was also performed in 54 OSCC patients who were treated with preoperative chemoradiotherapy and surgery. RESULTS: The overexpression of NS significantly enhanced the proliferation and invasive potential of OSCC cells. On the other hand, downregulation of NS suppressed the invasiveness of the cells. The alterations of these malignant phenotypes were associated with the activation of STAT3 signalling and its downstream targets. An immunohistochemical analysis demonstrated that a high NS tumour expression level significantly correlated with an advanced T-stage and N-stage. Furthermore, a Cox regression analysis revealed that the NS status (hazard ratio, 9.09; P=0.002) was a significant progression factor for OSCC patients. CONCLUSIONS: Our results suggest that targeting NS may provide a promising treatment for highly malignant OSCC.

Objective assessment of nerve injury after greater saphenous vein stripping.

AIM: The complication of nerve injury after greater saphenous vein stripping for varicosity is subjective, and a method for objective evaluation has never been established. The aim of this study was to evaluate postoperative sensory changes by quantitative assessment of current perception threshold (CPT), and to clarify the relation between CPT and symptoms. PATIENTS AND METHODS: Between January 2003 and August 2005, 27 limbs in 18 patients were enrolled. Quantitative sensory function was determined through CPT using a Neurometer (Neurotron, Inc., USA), with which saphenous nerve neural fiber selective minimum sensing values against three electrical stimuli (2000, 250, 5 Hz) were measured. CPT measurements were scheduled on the day before the operation, and 2-7 days, 1, 3, and 6 months after the operation. RESULTS: An increase in CPT value of more than 20% or decrease to below 50% compared to the preoperative value with at least two stimuli was defined as CPT abnormality. Subjective symptoms were observed in 13 limbs in the early postoperative period, and 10 limbs showed CPT abnormality. In 6 limbs with a CPT increase over 20% with all three stimuli, neurological symptoms continued for 6 months. CONCLUSIONS: CPT evaluation provides an objective indication of neurological symptoms in the lower limb following varicose vein surgery.

Association of HLA-A*3303-B*4403-DRB1*1302 haplotype, but not of TNFA promoter and NKp30 polymorphism, with postherpetic neuralgia (PHN) in the Japanese population.

Herpes zoster is a common disease caused by reactivation of the varicella zoster virus (VZV). In a small number of herpes zoster patients, pain persists beyond 4 weeks or more after healing of vesicular eruptions; this condition is termed postherpetic neuralgia (PHN). Positive associations of human histocompatibility leukocyte antigens (HLA) class I antigens, A33 and B44, with PHN in the Japanese population have been reported. Our hypothesis is that susceptibility genes to PHN might exist in the HLA region and the study objective is to further examine possible associations of genes in HLA class I, II and III regions, HLA-A, -B, -DRB1, tumor necrosis factor alpha (TNFA) promoter, and a natural killer cell activating receptor, NKp30 polymorphisms with PHN. Although TNFA or NKp30 in the class III region had been considered as a candidate locus, we found no associations of TNFA promoter or NKp30 polymorphisms with PHN in this study. We demonstrated that HLA-A*3303, -B*4403 and -DRB1*1302 alleles were significantly associated with PHN (P = 0.0007 for A*3303, P = 0.001 for B*4403 and P = 0.001 for DRB1*1302). The frequency of the HLA-A*3303-B*4403-DRB1*1302 haplotype was also significantly higher in the PHN patients than in the healthy controls (P = 0.0039). Our results suggest that this haplotype might be related to the pathogenesis of PHN.

Prevention of allergic inflammation by a novel prostaglandin receptor antagonist, S-5751.

Prostaglandin (PG) D2, the major cyclooxygenase metabolite generated from immunologically stimulated mast cells, is thought to contribute to the pathogenesis of allergic diseases due to its various inflammatory effects. However, since no DP receptor antagonist has been developed as an antiallergic drug, the role of PGD2 in the pathogenesis of allergic diseases remains uncertain. Here, we report the in vivo efficacy of our newly established DP receptor antagonist, S-5751 [((Z)-7-[(1R,2R,3S,5S)-2-(5-hydroxy benzo[b]thiophen-3-ylcarbonylamino)-10-norpinan-3-yl]hept-5- enoic acid)], using various allergic inflammation guinea pig models. In allergic rhinitis models, oral administration of S-5751 dramatically inhibited not only early nasal responses, as assessed by sneezing, mucosal plasma exudation, and nasal blockage, but also late responses such as mucosal plasma exudation and eosinophil infiltration. Even when S-5751 was administered after recovery from the early responses, these late phase responses were almost completely suppressed. In addition, S-5751 alleviated allergen-induced plasma exudation in the conjunctiva in an allergic conjunctivitis model and antigen-induced eosinophil infiltration into the lung in an asthma model. These findings provide evidence for the crucial role of PGD2 as a mediator of allergic inflammation in guinea pigs and suggest that DP receptor antagonists may be useful in the treatment of allergic diseases triggered by mast cell activation.

[Preliminary report: the efficacy of clonidine hydrochloride ointment for postherpetic neuralgia].

The combination of clonidine hydrochloride, alpha 2-agonist, and opioid is useful for relieving the pain due to surgical procedures or cancer. The routes of administrations used are intravenous, intramuscular as well as intrathecal, epidural and transmucosal. However, transdermal clonidine has not been reported. We, therefore, investigated the analgesic effect of local administration of clonidine ointment. Ten patients with postherpetic neuralgia (PHN) were selected randomly. They were requested to fill out a questionnaire after applying clonidine ointment (150 micrograms/ointment 1 g) to the painful area. Items included in the questionnaire were: effectiveness, visual analog scale (VAS) before and after the administration of clonidine ointment, onset time, with or without allodynia and effectiveness to allodynia in the former case, side effects, and patients' background. Analysis of the answers indicates that clonidine ointment produced a satisfactory effect in nine patients. Onset time was within a few minutes in most patients. No patients suffered any side effects. Specific mechanism of effectiveness or the site affected has not been confirmed in this study, but considering the quick onset, it is presumed that the site where the ointment was applied was the very site that was affected. Clonidine hydrochloride ointment was effective in relieving the symptoms of PHN.

Enhanced tissue expression and elevated circulating level of phospholipase A(2) receptor during murine endotoxic shock.

Phospholipase A(2) receptor (PLA(2)R) mediates a variety of biological responses elicited by mammalian secretory phospholipase A(2) (sPLA(2)). In mice, group IB sPLA(2) (sPLA(2)-IB) acts as an endogenous ligand of PLA(2)R, and analysis of PLA(2)R-deficient mice has demonstrated a critical role of the sPLA(2)-IB/PLA(2)R system in the production of proinflammatory cytokines such as tumor necrosis factor alpha (TNF-alpha) in the development of endotoxic shock. Here, we generated specific antibodies against a recombinant soluble form of PLA(2)R and examined its expression in the lung and spleen where a remarkable elevation of TNF-alpha expression has been observed during endotoxemia. Immunohistochemical analysis revealed the expression of PLA(2)R in type II alveolar epithelial cells and a subset of splenic lymphocytes, and its expression levels were markedly enhanced at 1 h after endotoxin challenge. Analysis with a newly developed sandwich enzyme-linked immunosorbent assay system revealed the presence of a soluble form of PLA(2)R in plasma of wild-type mice compared with its absence in plasma of PLA(2)R-deficient mice. After exposure to endotoxin, its circulating level was significantly elevated to the maximum level at 2-3 h after the treatment. These results suggest that tissue expression and the circulating level of PLA(2)R are elevated during murine endotoxemia, which might be relevant to its potential roles in the production of proinflammatory mediators during the development of inflammatory conditions.

Identification of a novel eosinophil chemotactic cytokine (ECF-L) as a chitinase family protein.

A novel eosinophil chemotactic cytokine (ECF-L) was purified from the culture supernatant of splenocytes of mice by a combination of anion-exchange chromatography, Procion red-agarose affinity chromatography, size exclusion high performance liquid chromatography (HPLC), and reverse phase HPLC. The NH(2)-terminal amino acid sequence was determined by direct protein sequencing. An ECF-L cDNA clone of 1,506 nucleotides was isolated from a cDNA library, and the nucleotide sequence predicted a mature protein of 397 amino acids. A recombinant ECF-L showed a level of eosinophil chemotactic activity comparable with that of natural ECF-L, and the activity was inhibited by a monoclonal antibody to ECF-L. ECF-L also attracted T lymphocytes and bone marrow polymorphonuclear leukocytes in vitro, whereas it caused selective extravasation of eosinophils in vivo. ECF-L mRNA was highly expressed in spleen, bone marrow, lung, and heart. A comprehensive GenBank data base search revealed that ECF-L is a chitinase family protein. ECF-L retains those amino acids highly conserved among chitinase family proteins, but Asp and Glu residues essential for the proton donation in hydrolysis were replaced by Asn and Gln, respectively. Although ECF-L contains a consensus CXC sequence near the NH(2) terminus akin to chemokine family proteins, the rest of ECF-L shows poor homology with chemokines.

Potential role of group X secretory phospholipase A(2) in cyclooxygenase-2-dependent PGE(2) formation during colon tumorigenesis.

Although the cyclooxygenase-2 (COX-2) pathway of the arachidonic acid cascade has been suggested to play an important role in colon carcinogenesis, there is little information concerning the identity of phospholipase A(2) (PLA(2)) involved in the arachidonic acid release in colon tumors. Here, we compared the potencies of three types of secretory PLA(2)s (group IB, IIA and X sPLA(2)s) for the arachidonic acid release from cultured human colon adenocarcinoma cells, and found that group X sPLA(2) has the most powerful potency in the release of arachidonic acid leading to COX-2-dependent prostaglandin E(2) (PGE(2)) formation. Furthermore, immunohistological analysis revealed the elevated expression of group X sPLA(2) in human colon adenocarcinoma neoplastic cells in concert with augmented expression of COX-2. These findings suggest a critical role of group X sPLA(2) in the PGE(2) biosynthesis during colon tumorigenesis.

Purified group X secretory phospholipase A(2) induced prominent release of arachidonic acid from human myeloid leukemia cells.

Group X secretory phospholipase A(2) (sPLA(2)-X) possesses several structural features characteristic of both group IB and IIA sPLA(2)s (sPLA(2)-IB and -IIA) and is postulated to be involved in inflammatory responses owing to its restricted expression in the spleen and thymus. Here, we report the purification of human recombinant COOH-terminal His-tagged sPLA(2)-X, the preparation of its antibody, and the purification of native sPLA(2)-X. The affinity-purified sPLA(2)-X protein migrated as various molecular species of 13-18 kDa on SDS-polyacrylamide gels, and N-glycosidase F treatment caused shifts to the 13- and 14-kDa bands. NH(2)-terminal amino acid sequencing analysis revealed that the 13-kDa form is a putative mature sPLA(2)-X and the 14-kDa protein possesses a propeptide of 11 amino acid residues attached at the NH(2) termini of the mature protein. Separation with reverse-phase high performance liquid chromatography revealed that N-linked carbohydrates are not required for the enzymatic activity and pro-sPLA(2)-X has a relatively weak potency compared with the mature protein. The mature sPLA(2)-X induced the release of arachidonic acid from phosphatidylcholine more efficiently than other human sPLA(2) groups (IB, IIA, IID, and V) and elicited a prompt and marked release of arachidonic acid from human monocytic THP-1 cells compared with sPLA(2)-IB and -IIA with concomitant production of prostaglandin E(2). A prominent release of arachidonic acid was also observed in sPLA(2)-X-treated human U937 and HL60 cells. Immunohistochemical analysis of human lung preparations revealed its expression in alveolar epithelial cells. These results indicate that human sPLA(2)-X is a unique N-glycosylated sPLA(2) that releases arachidonic acid from human myeloid leukemia cells more efficiently than sPLA(2)-IB and -IIA.

Cloning and characterization of novel mouse and human secretory phospholipase A(2)s.

Mammalian secretory phospholipase A(2)s (sPLA(2)s) are classified into several groups according to molecular structure and the localization of intramolecular disulfide bridges. Among them, group IIA sPLA(2) has been thought to be one of the key enzymes in the pathogenesis of inflammatory diseases owing to its augmented expression under various inflammatory conditions. However, in a number of inbred mouse strains, the group IIA sPLA(2) gene is naturally disrupted by a frameshift mutation. Here, we report the cloning of a cDNA encoding a novel sPLA(2) expressed in the spleen of group IIA sPLA(2)-deficient mouse. We also cloned its human homolog and mapped its gene location on chromosome 1p36.12 near the loci of group IIA and V sPLA(2) genes. The human mature sPLA(2) protein consists of 125 amino acids (M(r) = 14,500) preceded by a 20-residue prepeptide and is most similar to group IIA sPLA(2) with respect to the number and positions of cysteine residues as well as overall identity (48%). Based on these structural properties, the novel sPLA(2) should be categorized into group II, called group IID to follow the already identified IIA to IIC sPLA(2)s. When the cDNA was expressed in COS-7 cells, PLA(2) activity preferentially accumulated in the culture medium. It is maximally active at neutral to alkaline pH and with 2 mM Ca(2+). In assays with individual substrates, L-alpha-1-palmitoyl-2-linoleoyl phosphatidylethanolamine was more efficiently hydrolyzed than the other phospholipids examined. An RNA blot hybridized with the cDNA exhibited two transcripts (2.0 and 1.0 kb) in human spleen, thymus, and colon. The expression of a novel sPLA(2) mRNA was elevated in the thymus after treatment with endotoxin in rats as well as in group IIA sPLA(2)-deficient mice, suggesting its functional role in the progression of the inflammatory process.

[Anesthetic management of a patient with Saber-sheath trachea].

A 65-year-old man was scheduled for total gastrectomy. Preoperative chest radiograph showed significant narrowing of the trachea. On chest CT scan the trachea was U-shaped (tracheal index = 36%) and was diagnosed as saber-sheath trachea. During general anesthesia we took care to reduce the irritation by the endotracheal tube, particularly during intubation, and to avoid excessively high airway pressure. The trachea was watched carefully by bronchoscopy after intubation and during extubation not to neglect any complication. There was no complication after the operation.

Suppression of murine endotoxic shock by sPLA2 inhibitor, indoxam, through group IIA sPLA2-independent mechanisms.

Endotoxic shock is a systemic inflammatory process, involving a variety of proinflammatory mediators. Two types of secretory phospholipase A2 (sPLA2) have been implicated in this process. Group IB sPLA2 (PLA2-IB) binds to the PLA2 receptor (PLA2R), and PLA2R-deficient mice exhibit resistance to endotoxin-induced lethality with reduced plasma levels of proinflammatory cytokines, such as TNF-alpha. Group IIA sPLA2 (PLA2-IIA) is found in many tissues and cell types, and local and systemic levels are elevated under numerous inflammatory conditions including sepsis. In this study, we investigated the effect of a specific sPLA2 inhibitor, indoxam, on murine endotoxic shock. Indoxam suppressed the elevation of plasma TNF-alpha with a similar potency in PLA2-IIA-expressing and PLA2-IIA-deficient mice after LPS challenge. In PLA2-IIA-deficient mice, indoxam also suppressed the elevation of plasma IL-1beta, IL-6 and NO, and prolonged survival after LPS challenge. Indoxam was found to block the PLA2-IB binding to murine PLA2R with a high potency (Ki=30 nM). The inhibitory effects of indoxam on the LPS-induced elevation of plasma TNF-alpha levels could not be observed in mice deficient in PLA2R. These findings suggest that indoxam blocks the production of proinflammatory cytokines during endotoxemia through PLA2-IIA-independent mechanisms, possibly via blockade of the PLA2R function.

[Body temperature changes during combined inhalational and epidural anesthesia].

We investigated the effects of combined inhalational and lumbar epidural anesthesia on body temperature in 8 women for long-lasting lower abdominal surgery. Probes for forehead deep temperature and skin-surface temperatures were placed on the forehead, forearm, fingertip and toe tip on patients' arrival at the operating room. Tympanic membrane temperature was also measured. Lumbar epidural block was established with 2% lidocaine 10 ml. Twenty minutes later, general anesthesia was induced and maintained with nitrous oxide-oxygen-isoflurane. Epidural anesthesia was maintained with intermittent dose of 1% mepivacaine. Before the end of surgery, isoflurane concentration was increased from about 0.5% to 2% and was maintained at this level for 20 minutes, after which it was reduced. With the establishment of epidural blockade, toe tip temperature increased and fingertip temperature decreased, while core temperature remained unchanged. After induction of general anesthesia, fingertip temperature increased, while core temperature decreased. The core temperature drop during the anesthetic induction was significantly affected by the increase in toe tip temperature. Before the end of surgery, core temperature remained at a reduced but constant level, while fingertip temperature continued to decrease. With the application of 2% isoflurane, fingertip temperature increased, while core temperature decreased. The core temperature drop was significantly affected by the increase in fingertip temperature. After the reduction of isoflurane concentration, these temperature changes were reversed fully. At the end of surgery, fingertip temperature decreased, while core temperature increased. During mild hypothermia, isoflurane depressed thermoregulatory vasoconstriction dose-dependently until its concentration reached 0.6-0.7%. In conclusion, anesthetics-induced redistribution of body heat significantly affects the core temperature throughout anesthesia. Peripheral hypothermia results in core temperature drop when the redistribution is induced by anesthetics. Thermoregulatory vasoconstriction may not only suppress heat loss but also increase core temperature through centralization of body heat.

Production of eosinophil chemotactic factor by CD8+ T-cells in Toxocara canis-infected mice.

Production of eosinophil chemotactic factor by T-lymphocytes (ECF-L) was examined in Toxocara canis-infected mice. When spleen cells from T. canis-infected mice were cultured in serum-free RPMI1640, ECF-L production was detectable in an antigen-specific manner. The ECF-L production peaked at day 9 post-infection and then decreased. Depletion of Thy 1.2+ cells or CD8+ cells completely abrogated ECF-L production, whereas depletion of CD4+ cells did not, indicating that CD8+ T-cells are involved in the production of ECF-L. When bone marrow eosinophils obtained from T. canis-infected mice were preincubated with ECF-L, their chemotactic reactivity to parasite-derived ECFs was enhanced, whereas that of peritoneal cavity-derived eosinophils was not. Thus, ECF-L seems to be important not only as a chemoattractant but also as an activator of the chemotactic reactivity of naive eosinophils to the parasite-derived ECF in T. canis infection.

Cell adhesion to phosphatidylserine mediated by a product of growth arrest-specific gene 6.

Gas6, a product of a growth arrest-specific gene 6, potentiates proliferation of vascular smooth muscle cells and prevents cell death of vascular smooth muscle cells. It has been also demonstrated that Gas6 is a ligand of receptor tyrosine kinases Axl, Sky, and Mer. Gas6 contains gamma-carboxyglutamic acid residues, which are found in some blood coagulation factors and mediate the interaction of the coagulation factors with negatively charged phospholipid. In this study, we clarified that Gas6 specifically bound to phosphatidylserine and the binding was dependent on Ca2+ and gamma-carboxyglutamic acid residues. Furthermore, we found that U937 cells, which express Gas6 receptor on their surfaces, adhered to phosphatidylserine-coated enzyme-linked immunosorbent assay (ELISA) plate only in the presence of Gas6 and Ca2+. U937 cells also bound to ELISA plate coated with phosphatidylinositol, but the binding was independent of Gas6 and Ca2+. On the other hand, U937 cells did not adhere to phosphatidylcholine- or phosphatidylethanolamine-coated ELISA plate even in the presence of Gas6 and Ca2+. These findings suggest that Gas6 may play a role in recognition of cells exposing phosphatidylserine on their surfaces by phagocytic cells, which is supposed to be one of the mechanisms for clearing dying cells.

Roles of gamma-carboxylation and a sex hormone-binding globulin-like domain in receptor-binding and in biological activities of Gas6.

Gas6 is a ligand for an Axl/Sky receptor tyrosine kinase subfamily and has a structure composed of a Gla domain, four EGF-like domains and a C-terminal sex hormone-binding globulin (SHBG)-like domain. When examining the role of each domain in receptor-binding and biological activities of Gas6, we found that receptor-binding and mitogenic activities were markedly reduced by inhibiting gamma-carboxylation of the Gla domain, while a Gas6 mutant composed of only an SHBG-like domain retained both of these activities. Thus, the SHBG-like domain is apparently an entity indispensable for Gas6 activities, and gamma-carboxylation of the Gla domain has a regulatory role in retaining the activity of native Gas6.

Requirement of gamma-carboxyglutamic acid residues for the biological activity of Gas6: contribution of endogenous Gas6 to the proliferation of vascular smooth muscle cells.

Gas6 (encoded by growth-arrest-specific gene 6) is a gamma-carboxyglutamic acid (Gla)-containing protein which is released from growth-arrested vascular smooth muscle cells (VSMCs) and potentiates VSMC proliferation induced by Ca2+-mobilizing growth factors, but not that induced by receptor tyrosine kinases. In this study we examined the importance of Gla residues for the biological activities of Gas6 and tried to assess the importance of endogenous Gas6 in VSMC proliferation. We demonstrated that Gla-deficient Gas6 lacked receptor-binding and growth-potentiating activities. Therefore the vitamin K-dependent modification of Gas6 appeared to be essential for its biological activities. Next we used warfarin, an inhibitor of vitamin K-dependent gamma-carboxylation, to estimate the contribution of endogenous Gas6 to VSMC proliferation. Warfarin markedly inhibited the thrombin-induced proliferation of VSMC without affecting the mRNA or protein expression of Gas6. Therefore the inhibition seems to be due to prevention of the vitamin K-dependent modification of Gas6. However, warfarin did not affect epidermal growth factor-induced proliferation. A neutralizing antibody against Gas6 gave a similar result, i.e. it inhibited thrombin-induced VSMC proliferation but not that induced by epidermal growth factor. These results indicate that endogenously produced Gas6 is very important for VSMC proliferation induced by Ca2+-mobilizing growth factors.