Expression of the c-Met oncogene by tumor cells predicts a favorable outcome in classical Hodgkin's lymphoma.

BACKGROUND: The c-Met signaling pathway regulates a variety of biological processes, including proliferation, survival and migration. Deregulated c-Met activation has been implicated in the pathogenesis and prognosis of many human malignancies. We studied the function and prognostic significance of c-Met and hepatocyte growth factor protein expression in patients with classical Hodgkin's lymphoma. DESIGN AND METHODS: Expression of c-Met and its ligand, hepatocyte growth factor, were determined by immunohistochemistry. Prognostic values were defined in cohorts of German and Dutch patients with classical Hodgkin's lymphoma. Functional studies were performed on Hodgkin's lymphoma cell lines. RESULTS: Expression of c-Met was detected in the tumor cells of 52% (80/153) of the patients and expression of its ligand, hepatocyte growth factor, in 8% (10/121) of the patients. c-Met expression correlated with a 5-year freedom from tumor progression of 94%, whereas lack of expression correlated with a 5-year freedom from tumor progression of 73% (P<0.001) in the combined cohort. In multivariate analysis both c-Met (hazard ratio 5.0, 95% confidence interval 1.9-13.3, P<0.001) and stage (hazard ratio 2.8, 95% confidence interval 1.2-6.4, P=0.014) were independent predictors for freedom from tumor progression. In functional studies activation with hepatocyte growth factor did not affect cell growth, while the c-Met inhibitor SU11274 suppressed cell growth by inducing G2/M cell cycle arrest. CONCLUSIONS: Although functional studies showed an oncogenic role of the hepatocyte growth factor/c-Met signaling pathway in cell cycle progression, expression of c-Met in tumor cells from patients with classical Hodgkin's lymphoma strongly correlated with a favorable prognosis in two independent cohorts.

Plasma thymus and activation-regulated chemokine as an early response marker in classical Hodgkin's lymphoma.

BACKGROUND: Plasma thymus and activation-regulated chemokine is a potential biomarker for classical Hodgkin's lymphoma. To define its value as a marker to monitor treatment response, we correlated serial plasma thymus and activation-regulated chemokine levels with clinical response in newly diagnosed and relapsed classical Hodgkin's lymphoma patients. DESIGN AND METHODS: Plasma was collected from 60 (39 early stage and 21 advanced stage) newly diagnosed classical Hodgkin's lymphoma patients before, during, and after treatment, and from 12 relapsed patients before and after treatment. Plasma thymus and activation-regulated chemokine levels were determined by enzyme-linked immunosorbent assay and were related to pre-treatment metabolic tumor volume, as measured by quantification of 2-[18F]fluoro-2-deoxyglucose positron emission tomography images, and to treatment response. RESULTS: Baseline plasma thymus and activation-regulated chemokine levels correlated with stage of disease and bulky disease, and more closely with metabolic tumor volume. Response to treatment was observed among 38 of 39 early stage and 19 of 21 advanced stage patients. Reduction in plasma thymus and activation-regulated chemokine to normal range levels could be observed as early as after one cycle of chemotherapy in all responsive patients, while plasma levels remained elevated during and after treatment in the 3 non-responsive patients. Plasma thymus and activation-regulated chemokine was elevated in all 12 relapsed patients at time of relapse and remained elevated after salvage treatment in the 4 non-responsive patients. CONCLUSIONS: Baseline plasma thymus and activation-regulated chemokine levels correlate with classical Hodgkin's lymphoma tumor burden and serial levels correlate with response to treatment in patients with classical Hodgkin's lymphoma.

Prothrombotic gene variants and mortality after cerebral ischemia of arterial origin.

BACKGROUND: Several functional prothrombotic gene variants have been associated with cerebral ischemia and myocardial infarction. We hypothesized that such gene variants may also be associated with mortality after cerebral ischemia of arterial origin because of an increased risk of fatal vascular events. METHODS: We performed a case-control study in 316 long-term survivors and 887 patients with recent cerebral ischemia of arterial origin. False discovery rate q values were calculated to account for multiple testing. The mean duration between occurrence of cerebral ischemia and DNA collection was 16.8 years in long-term survivors and 3.2 months in recent patients. RESULTS: Two of 23 variants were associated with mortality: the 95Arg allele of the coagulation factor XIII subunit B (F13B) His95Arg variant (OR, 1.5 for Arg/Arg and His/Arg vs. His/His genotype; 95% CI, 1.1-2.2, q = 0.29) and the 4G allele of the plasminogen activator inhibitor-1 (PAI-1) 4G/5G variant (OR, 1.5 for 4G/4G and 5G/4G vs. 5G/5G genotype; 95% CI, 1.1-2.0, q = 0.29). Both associations disappeared after accounting for multiple testing. Data analysis restricted to recently deceased patients (n = 133) yielded similar results. CONCLUSIONS: In this hospital-based study none of 23 prothrombotic gene variants were associated with long-term mortality after cerebral ischemia of arterial origin. Prothrombotic gene variants do not appear to play an important role in long-term mortality after cerebral ischemia.

Contribution of amino acid region 659-663 of Factor Va heavy chain to the activity of factor Xa within prothrombinase .

Factor Va, the cofactor of prothrombinase, is composed of heavy and light chains associated noncovalently in the presence of divalent metal ions. The COOH-terminal region of the heavy chain contains acidic amino acid clusters that are important for cofactor activity. In this work, we have investigated the role of amino acid region 659-663, which contains five consecutive acidic amino acid residues, by site-directed mutagenesis. We have generated factor V molecules in which all residues were mutated to either lysine (factor V(5K)) or alanine (factor V(5A)). We have also constructed a mutant molecule with this region deleted (factor V(Δ659-663)). The recombinant molecules along with wild-type factor V (factor V(WT)) were transiently expressed in mammalian cells, purified, and assessed for cofactor activity. Two-stage clotting assays revealed that the mutant molecules had reduced clotting activities compared to that of factor Va(WT). Kinetic analyses of prothrombinase assembled with the mutant molecules demonstrated diminished k(cat) values, while the affinity of all mutant molecules for factor Xa was similar to that for factor Va(WT). Gel electrophoresis analyses of plasma-derived and recombinant mutant prothrombin activation demonstrated delayed cleavage of prothrombin at both Arg(320) and Arg(271) by prothrombinase assembled with the mutant molecules, resulting in meizothrombin lingering throughout the activation process. These results were confirmed after analysis of the cleavage of FPR-meizothrombin. Our findings provide new insights into the structural contribution of the acidic COOH-terminal region of factor Va heavy chain to factor Xa activity within prothrombinase and demonstrate that amino acid region 659-663 from the heavy chain of the cofactor contributes to the regulation of the rate of cleavage of prothrombin by prothrombinase.

Polymorphisms in the protein C gene as risk factor for venous thrombosis.

Protein C is an important inhibitor of blood coagulation. We investigated the effect of two polymorphisms within the promoter region of the protein C gene (C/T at position 2405 and A/G at position 2418) on risk of venous thrombosis and on plasma protein C levels. In addition the combined effect of the two polymorphisms with factor V Leiden and oral contraceptive use was investigated. Previous studies on these polymorphisms were small and were not able to investigate synergistic effects. In the Multiple Environmental and Genetic Assessment of risk factors for venous thrombosis (MEGA study), protein C levels were determined in 2,043 patients with venous thrombosis and 2,857 control subjects, and the two polymorphisms in 4,285 patients and 4,863 control subjects. The CC/GG genotype was associated with the lowest protein C levels. Compared to carriers of the TT/AA genotype - a genotype associated with higher protein C levels - the risk of venous thrombosis in CC/GG carriers was 1.3-fold increased (95% confidence interval 1.09-1.48). The combination of factor V Leiden with the CC/GG genotype led to a 4.7-fold increased risk, compared to non-carriers with the TT/AA genotype. Oral contraceptive use together with the CC/GG genotype resulted in a 5.2-fold increased risk. In conclusion, the CC/GG genotype is associated with lower levels of protein C and an elevated risk of venous thrombosis compared to the TT/AA genotype. There is no clear synergistic effect of the CC/GG genotype with factor V Leiden or oral contraceptive use on thrombotic risk.

Fibrinogen gamma gene 3'-end polymorphisms and risk of venous thromboembolism in the African-American and Caucasian population.

Genetic determinants of venous thromboembolism (VTE) in the African-American population are poorly characterised. It was recently shown that fibrinogen gamma gene (FGG) polymorphisms 10034C>T and 9340T>C influence VTE risk in the Caucasian population. In the African-American population these polymorphisms are common, with allele frequencies above 25%. Here we evaluated whether these and other FGG 3'-end polymorphisms were associated with VTE risk in the African-American population and aimed to replicate the association in the Caucasian population. We examined 557 Caucasian patients and 678 Caucasian controls, and 537 African-American patients and 586 African-American controls from the ;Genetic Attributes and Thrombosis Epidemiology' (GATE) study. In the African-American population, 10034C>T and 9340T>C marginally influenced VTE-risk, with a 20% increase in risk for 10034TT carriers and a 20% reduction in risk for 9340CC carriers. In the Caucasian population, 10034TT was associated with a 1.7-fold increase in risk, which increased to 2.1-fold for idiopathic VTE patients. 9340CC significantly reduced VTE risk approximately two-fold. In conclusion, both FGG polymorphisms 10034C>T and 9340T>C influence VTE-risk, with the strongest effects observed in the Caucasian population, confirming previous data on these polymorphisms in this population.

Fibrinogen gamma' in ischemic stroke: a case-control study.

BACKGROUND AND PURPOSE: To determine the contribution of fibrinogen gamma' levels and FGG haplotypes to ischemic stroke. METHODS: Associations between fibrinogen gamma' levels, fibrinogen gamma'/total fibrinogen ratio, and FGG haplotypes with the risk of ischemic stroke were determined in 124 cases and 125 controls. RESULTS: Fibrinogen gamma'/total fibrinogen ratio was higher in patients than in controls during the acute phase of the stroke and lower in the convalescent phase 3 months after the stroke. FGG haplotype 3 (H3) was associated with a reduced risk of ischemic stroke (odds ratio 0.60; 95% CI, 0.38 to 0.94), but not with the fibrinogen gamma'/total fibrinogen ratio. In contrast, FGG-H2 was associated with a decreased fibrinogen gamma'/total fibrinogen ratio, but not with risk of stroke. CONCLUSIONS: Fibrinogen gamma'/total fibrinogen ratio is associated with ischemic stroke, especially in the acute phase of the disease. In addition, FGG-H3 haplotype appears to be protective against ischemic stroke.

Haplotypes of IL1B, IL1RN, IL1R1, and IL1R2 and the risk of venous thrombosis.

OBJECTIVE: It has been suggested that the overall effect of the major proinflammatory cytokine interleukin-1 (IL-1) on coagulation and fibrinolysis is prothrombotic. The aim of this study was to investigate whether common variations in IL1B, IL1RN, IL1R1, and IL1R2 influence the risk of venous thrombosis. METHODS AND RESULTS: In a case-control study on the causes of deep venous thrombosis, the Leiden Thrombophilia Study (LETS), we genotyped 18 single nucleotide polymorphisms (SNPs) in IL1B, IL1RN, IL1R1, and IL1R2, enabling us to tag a total of 25 haplotype groups. Overall testing of the haplotype frequency distribution in patients and controls indicated that a recessive effect was present in IL1RN (P=0.031). Subsequently the risk of venous thrombosis was calculated for each haplotype of IL1RN. Increased thrombotic risk was found for homozygous carriers of haplotype 5 (H5, tagged by SNP 13888T/G, rs2232354) of IL1RN (Odds ratio=3.9; 95% confidence interval: 1.6 to 9.7; P=0.002). No risk was associated with haplotype 3 of IL1RN, which contains the frequently examined allele 2 variant of the intron 2 VNTR. CONCLUSIONS: We found that IL1RN-H5H5 carriership increases the risk of venous thrombosis.

No association between the common MTHFR 677C->T polymorphism and venous thrombosis: results from the MEGA study.

BACKGROUND: Increased homocysteine levels are related to the occurrence of venous thrombosis, but whether this relation is causal is unclear. The T-variant of the common methylenetetrahydrofolate reductase (MTHFR) 677C-->T polymorphism mildly increases homocysteine levels. Meta-analyses have demonstrated a weak effect of the MTHFR 677TT genotype on risk but are sensitive to selective publication of positive results. The aim of the present study was to evaluate the effect of the MTHFR genotype on the risk of venous thrombosis, overall and in subgroups of known risk factors, in a single large study. METHODS: In the Multiple Environmental and Genetic Assessment of risk factors for venous thrombosis (MEGA Study), a population-based case-control study, we collected DNA from 4375 patients with a first deep vein thrombosis of the leg or pulmonary embolism and from 4856 control subjects. Information about risk factors for venous thrombosis was obtained from questionnaires. RESULTS: MTHFR 677C-->T was not associated with the risk of venous thrombosis (odds ratio [95% confidence interval], 0.99 [0.91-1.08] for the CT genotype and 0.94 [0.81-1.08] for the TT genotype). Stratification by known risk factors for venous thrombosis provided no evidence of an association in specific groups. CONCLUSIONS: In a single large study, MTHFR 677C-->T was not associated with the risk of venous thrombosis, and the narrow confidence interval excludes even a small effect. Therefore, mildly elevated homocysteine levels as a result of MTHFR 677TT do not seem to cause venous thrombosis. There is no rationale for measuring the MTHFR 677C-->T variant for clinical purposes.

Strongly enhanced IL-10 production using stable galectin-1 homodimers.

Galectin-1 is the homodimeric form of a protein, which is present in a dynamic equilibrium with the beta-galactoside monomeric form and has potent anti-inflammatory and immunomodulating effects. These favorable effects are probably related to the induction of apoptosis in activated T cells and the induction of IL-10, which have been demonstrated to be characteristic for the dimeric form of the protein. Based on these findings it can be speculated that the in vivo effects of galectin-1 can be improved by the generation of stable galectin-1 homodimers (dGal). To test this hypothesis we produced leucine-zipper based stable galectin-1 homodimers and tested its apoptosis inducing effects on MOLT-4 cells and its immunomodulatory effects in vitro on PBMC of five independent donors. Phosphatidylserine exposure and a drop in mitochondrial membrane potential was strongly enhanced on MOLT-4 cells upon treatment with dGal as compared to wtGal. The minimal effective concentration was 20-fold reduced as compared to the minimal effective wtGal concentration. dGal showed enhanced induction of IL-10 on total PBMC as compared to treatment with wild-type protein (wtGal). The minimal effective dGal concentration was 100-fold lower than that of wtGal. Of the purified cell populations monocytes are the strongest IL-10 producers, whereas T cells induce IL-10 at a lower level and no induction is observed in B cells. Besides induction of IL-10, dGal caused an increase in IL-1beta production in all donors and a reduction of IL-2 production in 3 out of 5 donors, whereas no consistent changes were observed for other inflammatory cytokines. In summary, we demonstrated that dGal shows enhanced effects at strongly reduced concentrations. Application of dGal may therefore serve as an improved treatment of chronic inflammatory diseases.

ABO blood group genotypes, plasma von Willebrand factor levels and loading of von Willebrand factor with A and B antigens.

ABO blood group is a genetic determinant of von Willebrand factor (VWF) levels. We investigated the effect of ABO genotypes on VWF and factor VIII (FVIII) levels and on the degree to which VWF is loaded with A- and B-antigens, expressed as normalized ratios, nA-ratio and nB-ratio, respectively, in the Leiden Thrombophilia Study, a large case-control study on venous thrombosis. We found that the ABO locus had an allele-specific, dosage dependent effect on VWF and FVIII levels and on the loading of VWF with A-antigen and B-antigen. The highest mean nA- and nB-ratios were found in A(1)A(1) and BB genotypes, respectively. Four A(1)O carriers had four 43-bp repeats in the minisatellite region of the ABO gene in stead of the expected one repeat. All had a reduced nA-ratio compared to A(1)O carriers with one repeat in their A(1) allele. The amount of A- and B-antigens expressed onVWF (nA-ratio and nB-ratio) explained about 18% (R(2)) of the variation in VWF levels.

Interleukin-6 induction of protein s is regulated through signal transducer and activator of transcription 3.

OBJECTIVE: The protein C anticoagulant pathway is an essential process for attenuating thrombin generation by the membrane-bound procoagulant complexes tenase and prothrombinase. In this pathway, protein S (PS) serves as a cofactor for activated protein C. PS circulates in plasma both in a free form and in complex with complement component 4b-binding protein (C4BP). C4BP is a known acute phase reactant, thereby suggesting a relation between PS and the acute phase response. Interleukin (IL)-6 has been shown to increase both PS and C4BP gene expression. Our objective was to study the regulation of PS gene expression by IL-6 in detail. METHODS AND RESULTS: IL-6 upregulates both PS mRNA and protein levels in liver-derived HepG2 cells. The promoter of the PS gene (PROS1) was cloned upstream from a luciferase reporter gene. After transfection in HepG2 cells, the luciferase activity was shown to be stimulated by the addition of IL-6. IL-6 exerts its effect through Signal Transducer and Activator of Transcription 3 (STAT3) that interacts with the PROS1 promoter at a binding site in between nucleotides 229 to 207 upstream from the translational start. CONCLUSIONS: IL-6 induces PS expression via STAT3. A possible function for IL-6-induced PS expression in cell survival is discussed.

Genetic variation in the first-pass metabolism of ethinylestradiol, sex hormone binding globulin levels and venous thrombosis risk.

BACKGROUND: Use of ethinylestradiol, one of the active ingredients in combined oral contraceptives, affects the incidence of venous thrombosis. To explain why some women develop thrombosis when using oral contraceptives and others do not, we hypothesized a role for the first-pass metabolism of ethinylestradiol in the liver. We set out to determine the association between genetic variation in the first-pass metabolism of ethinylestradiol, venous thrombosis risk and the effect on Sex-hormone-binding-globulin (SHBG) levels. METHODS: Premenopausal women were included from two case-control studies: LETS (103 cases; 159 controls) and MEGA (397 cases; 796 controls). Haplotype-tagging SNPs were selected in 11 candidate genes; COMT, CYP1A2, CYP2C9, CYP3A4, CYP3A5, SULT1A1, SULT1E1, UGT1A1, UGT1A3, UGT1A9, UGT2B7. Venous thrombosis risk was expressed as odds ratios (OR) with 95% confidence intervals (CI). For SHBG levels, mean differences with 95%CI were estimated in combined oral contraceptive-using control subjects from the MEGA study. RESULTS: Two copies of haplotype D in the UGT2B7 gene increased venous thrombosis risk (ORLETS: 3.78; ORMEGA: 2.61) as well as SHBG levels (mean difference 27.6nmol/L, 95%CI: -61.7 to 116.9 compared with no copies) in oral contraceptive users and not in non-users. In oral contraceptive users, haplotype A and B in the CYP3A4 gene were associated with venous thrombosis risk, but not in non-users; however, the effect on SHBG levels was not directional with the risk. None of the other haplotypes were associated with venous thrombosis. CONCLUSION: Genetic variation in the UGT2B7 gene may, in part, explain venous thrombosis risk in combined oral contraceptive users.

Differential effects of the loss of intrachain- versus interchain-disulfide bonds in the cystine-knot domain of von Willebrand factor on the clinical phenotype of von Willebrand disease.

Von Willebrand factor (VWF) contains a large number of cysteine residues, which all form disulfide bonds. Mutations of cysteines located in the cystine-knot (CK) domain of VWF have been identified in both qualitative type 2A (IID) and quantitative type 3 von Willebrand disease (VWD). Our objective was to test the hypothesis that the difference in phenotype is related to whether the mutated cysteine residue is involved in either interchain- or intrachain-disulfide-bond formation. The effects of three cysteine mutations which are all located in the CK-domain of VWF, C2773S (type 2A(IID)), C2739Y (type 3), and C2754W (type 3), were studied by transient expression in 293T cells. Cotransfection of wild-type (wt) and C2773S VWF constructs reproduced the plasma phenotype of heterozygous type 2A(IID) patients, with normal to high levels of VWF antigen (VWF:Ag), absence of high-molecular-weight multimers, and the presence of intervening bands between the normal multimers. In contrast, single transfections of C2739Y or C2754W resulted in a quantitative VWF defect with low VWF:Ag levels, and co-transfections of wt and mutant constructs resulted in a 50% reduction of VWF:Ag and only a minor effect on VWF multimerization. We demonstrated N-terminal dimerization of VWF-C2773S and both N- and C-terminal dimerization of VWF-C2754W. Our data suggest that loss of a single disulfide bond in the CK-domain of VWF leads to a recessive, quantitative VWF deficiency if an intrachain-disulfide bond is involved, and to a dominant-negative, qualitative defect of VWF if an interchain-disulfide bond is involved.

Haplotypes encoding the factor VIII 1241 Glu variation, factor VIII levels and the risk of venous thrombosis.

Levels of factor VIII (FVIII) are associated with the risk of venous thrombosis. The FVIII variation D1241E has been reported to be associated with decreased levels of FVIII. Our objective was to study whether D1241E is associated with levels of FVIII and the risk of venous thrombosis and whether this association is caused by D1241E or another linked variation. We analyzed the association of three FVIII gene haplotypes encoding 1241E (further denoted as HT1, HT3, and HT5) with FVIII levels and thrombosis risk. This analysis was performed in the Leiden Thrombophilia Study (LETS). The control populations of two case-controls studies on arterial thrombosis in men and women, respectively, were used to confirm the effects observed on FVIII:C in the LETS. In men, HT1 was associated with a 6% reduction in FVIII:C and with a reduced risk of venous thrombosis [odds ratio 0.4 (CI95 0.2-0.8)]. Logistic regression showed that the risk reduction was only partially dependent of the reduction in FVIII levels. HT1 showed no effects in women on either FVIII:C or risk of thrombosis. The number of carriers of HT3 and HT5 was too low to make an accurate estimate of the risk of venous thrombosis. Neither HT3 nor HT5 showed effects on levels of FVIII:C. When we consider that all three haplotypes encoding 1241E show different effects on FVIII:C and thrombosis risk, it is possible that D1241E is not the functional variation. However, FVIII gene variations do contribute to both levels of FVIII and the risk of thrombosis.

Comparison of optimal cutoff points for single and multiple tests in personnel selection.

This paper compares the determination of optimal cutoff points for single and multiple tests in the field of personnel selection. Decisional skills of predictor tests composing the multiple test are assumed to be endogenous variables that depend on the cutting points to be set. It is shown how the predictor cutoffs and the collective decision rule are determined dependently by maximizing the multiple test's common expected utility. Our main result specifies the condition that determines the relationship between the optimal cutoff points for single and multiple tests, given the number of predictor tests, the collective decision rule (aggregation procedure of predictor tests' recommendations) and the function relating the tests' decisional skills to the predictor cutoff points. The proposed dichotomous decision-making method is illustrated by an empirical example of selecting trainees by means of the Assessment Center method.

The plasminogen activator inhibitor-1 (PAI-1) promoter haplotype is related to PAI-1 plasma concentrations in lean individuals.

BACKGROUND: Elevated plasminogen activator inhibitor-1 (PAI-1) concentrations are associated with cardiovascular diseases. PAI-1 antigen levels are influenced by environmental factors such as body mass index (BMI), and by genetic factors. The PAI-1 promoter of the PAI-1 gene contains two common polymorphisms (-844A/G and -675(4G/5G)) and the 4G allele of the -675(4G/5G) variation has been associated with elevated PAI-1 concentrations and on some occasions with an increased risk of cardiovascular disease. OBJECTIVES: The aim of our study was to investigate the effect of the PAI-1 promoter haplotype on PAI-1 concentrations and to determine the role of BMI. METHODS: The association between the PAI-1 promoter haplotype and PAI-1 antigen levels was investigated in two independent populations, each including 600 healthy Caucasians. Furthermore, to assess the effect of the PAI-1 promoter haplotype on PAI-1 promoter activity, in vitro reporter gene assays were performed in HepG2 and BAEC cells. RESULTS: We observed significantly higher PAI-1 concentrations in A-4G homozygotes than in G-5G carriers in lean subjects (BMI in the lowest quartile). In these lean subjects, the PAI-1 concentrations in A-4G/G-5G heterozygotes were reduced to 60-75%, and the concentrations in G-5G homozygotes to 45-55%, compared to the PAI-1 concentrations of A-4G homozygotes (p < 0.01). PAI-1 concentrations increased approximately four-fold from the lowest to the highest BMI quartile (p < 0.01). The reporter gene assays did not support a direct effect of the PAI-1 promoter haplotype on promoter activity in HepG2 or BEAC cells. CONCLUSIONS: Our study suggests that the PAI-1 promoter haplotype and BMI affect PAI-1 concentrations and that BMI is a stronger determinant than PAI-1 promoter variation.

C-reactive protein does not directly induce tissue factor in human monocytes.

OBJECTIVE: It is generally assumed that C-reactive protein (CRP) induces synthesis of tissue factor (TF) in monocytic cells, thereby potentially initiating intravascular blood coagulation. We aimed to elucidate the mechanism of CRP-induced TF expression in monocytes and monocyte-derived macrophages (MDMs) in vitro. METHODS AND RESULTS: Monocytes were isolated from the blood of healthy donors and cultured with or without CRP or lipopolysaccharide (LPS) to study the time course of TF antigen and TF mRNA expression. Addition of 100 microg/mL CRP did not result in a significant increase in TF antigen (range: 9 to 163 pg/10(6) cells, n=11) and TF mRNA (relative number of TF transcripts; N(TF)=0.01 to 0.33), when compared with nonstimulated cells (TF antigen 7 to 46 pg/10(6) cells, N(TF)=0.01 to 0.13). Variation of CRP concentration and exposure time did not affect the TF response. Similar results were obtained in monocytes cultured in suspension and in MDMs. In contrast, TF was strongly induced by 10 microg/mL LPS (TF antigen 1125 to 6120 pg/10(6) cells, N(TF)=5.94 to 23.43). Cultured monocytes did express FcRgammaII, a putative CRP receptor, and addition of CRP induced a 7-fold increase in the production of monocyte chemoattractant protein-1 (MCP-1). Interestingly, CRP addition to peripheral blood mononuclear cells (PBMCs) did result in TF expression on monocytic cells. CONCLUSIONS: The absence of TF induction after incubation of purified monocytes with CRP indicates that CRP is unable to induce TF expression in monocytes and MDMs directly. The presence of CRP-induced TF expression in PBMCs suggests that CRP can induce TF indirectly, probably through cross-talk between cells.