A proposal for integrated efficacy-to-effectiveness (E2E) clinical trials.

We propose an "efficacy-to-effectiveness" (E2E) clinical trial design, in which an effectiveness trial would commence seamlessly upon completion of the efficacy trial. Efficacy trials use inclusion/exclusion criteria to produce relatively homogeneous samples of participants with the target condition, conducted in settings that foster adherence to rigorous clinical protocols. Effectiveness trials use inclusion/exclusion criteria that generate heterogeneous samples that are more similar to the general patient spectrum, conducted in more varied settings, with protocols that approximate typical clinical care. In E2E trials, results from the efficacy trial component would be used to design the effectiveness trial component, to confirm and/or discern associations between clinical characteristics and treatment effects in typical care, and potentially to test new hypotheses. An E2E approach may improve the evidentiary basis for selecting treatments, expand understanding of the effectiveness of treatments in subgroups with particular clinical features, and foster incorporation of effectiveness information into regulatory processes.

Randomized trial of filgrastim versus chemotherapy and filgrastim mobilization of hematopoietic progenitor cells for rescue in autologous transplantation.

Peripheral blood cell (PBC) rescue has become the mainstay for autologous transplantation in patients with lymphoma, multiple myeloma, and solid tumors. Different methods of hematopoietic progenitor cell (HPC) mobilization are in use without an established standard. Forty-seven patients with relapsed or refractory lymphoma received salvage chemotherapy and were randomized to have HPC mobilization using filgrastim [granulocyte-colony-stimulating factor (G-CSF)] alone for 4 days at 10 microg/kg per day (arm A) or cyclophosphamide (5 g/m(2)) and G-CSF at 10 microg/kg per day until hematologic recovery (arm B). Engraftment and ease of PBC collection were primary outcomes. All patients underwent the same high-dose chemotherapy followed by reinfusion of PBCs. There were no differences in median time to neutrophil engraftment (11 days in both arms; P =.5) or platelet engraftment (14 days in arm A, 13 days in arm B; P =.35). Combined chemotherapy and G-CSF resulted in higher CD34(+) cell collection than G-CSF alone (median, 7.2 vs 2.5 x 10(6) cells/kg; P =.004), but this did not impact engraftment. No differences were found in other PBC harvest outcomes or resource utilization measures. A high degree of tumor contamination, as studied by consensus CDR3 polymerase chain reaction of the mobilized PBCs, was present in both arms (92% in arm A vs 90% in arm B; P = 1). No differences were found in overall survival or progression-free survival at a median follow-up of 21 months. This randomized trial provides clinical evidence that the use of G-CSF alone is adequate for HPC mobilization, even in heavily pretreated patients with relapsed lymphoma.

Hormone replacement therapy after breast cancer: a systematic review and quantitative assessment of risk.

PURPOSE: Hormone replacement therapy (HRT) is typically withheld from women with breast cancer because of concern that it might increase the risk of recurrence. The purpose of this study was to quantify the risk of recurrent breast cancer associated with HRT among breast cancer survivors. METHODS: We performed a systematic literature review through May 1999, calculating the relative risk (RR) of breast cancer recurrence in each study by comparing the number of recurrences in the HRT group to those in the control group. In studies that did not contain a control group, we constructed one by estimating the expected number of recurrences based on data from the Early Breast Cancer Trialists' Collaborative Group, adjusting for nodal status and disease-free interval. RRs across all studies were combined using random-effects models. RESULTS: Of the 11 eligible studies, four had control groups and included 214 breast cancer survivors who began HRT after a mean disease-free interval of 52 months. Over a mean follow-up of 30 months, 17 of 214 HRT users experienced recurrence (4.2% per year), compared with 66 of 623 controls (5.4% per year). HRT did not seem to affect breast cancer recurrence risk (RR = 0.64, 95% confidence interval [CI], 0.36 to 1.15). Including all 11 studies in the analyses (669 HRT users), using estimated control groups for the seven uncontrolled trials, the combined RR was 0.82 (95% CI, 0.58 to 1.15). CONCLUSION: Although our analyses suggest that HRT has no significant effect on breast cancer recurrence, these findings were based on observational data subject to a variety of biases.

Megestrol and tamoxifen in patients with advanced endometrial cancer: an Eastern Cooperative Oncology Group Study (E4882).

To investigate the effect of adding tamoxifen to megestrol in the hormonal therapy for advanced endometrial cancer, 66 patients were entered in this study. Initially, 41 patients were randomized to either the standard progestin therapy of megestrol or to the combination of megestrol and tamoxifen between October 1982 and October 1984. The megestrol arm was terminated because of poor accrual and 25 patients were directly assigned to the combination arm. Among the 20 eligible cases on the megestrol arm, the response rate of 20% consisted of I complete response and 3 partial responses. The response rate on the megestrol plus tamoxifen arm was 19% with 1 (2%) complete response and 7 (17%) partial responses among 42 eligible cases. The median survival times were 12.0 months and 8.6 months, respectively. Only mild and moderate toxicities were observed on megestrol compared with more toxic complications observed on the combination of megestrol and tamoxifen, including a life-threatening case of pulmonary embolism. Although we could not carry out a comparative evaluation as intended, we conclude that the combination of megestrol and tamoxifen offers no clinical advantage over megestrol alone in the treatment of advanced endometrial carcinoma.

Conventional-dose chemotherapy compared with high-dose chemotherapy plus autologous hematopoietic stem-cell transplantation for metastatic breast cancer. Philadelphia Bone Marrow Transplant Group.

BACKGROUND: We conducted a randomized trial in which we compared high-dose chemotherapy plus hematopoietic stem-cell rescue with a prolonged course of monthly conventional-dose chemotherapy in women with metastatic breast cancer. METHODS: Women 18 to 60 years of age who had metastatic breast cancer received four to six cycles of standard combination chemotherapy. Patients who had a complete or partial response to induction chemotherapy were then randomly assigned to receive either a single course of high doses of carboplatin, thiotepa, and cyclophosphamide plus transplantation of autologous hematopoietic stem cells or up to 24 cycles of cyclophosphamide, methotrexate, and fluorouracil in conventional doses. The primary end point was survival. RESULTS: The median follow-up was 37 months. Of 553 patients who enrolled in the study, 58 had a complete response to induction chemotherapy and 252 had a partial response. Of these, 110 patients were assigned to receive high-dose chemotherapy plus hematopoietic stem cells and 89 were assigned to receive conventional-dose chemotherapy. In an intention-to-treat analysis, we found no significant difference in survival overall at three years between the two treatment groups (32 percent in the transplantation group and 38 percent in the conventional-chemotherapy group). There was no significant difference between the two treatments in the median time to progression of the disease (9.6 months for high-dose chemotherapy plus hematopoietic stem cells and 9.0 months for conventional-dose chemotherapy). CONCLUSIONS: As compared with maintenance chemotherapy in conventional doses, high-dose chemotherapy plus autologous stem-cell transplantation soon after the induction of a complete or partial remission with conventional-dose chemotherapy does not improve survival in women with metastatic breast cancer.

A phase II study of docetaxel in patients with paclitaxel-resistant metastatic breast cancer.

PURPOSE: To evaluate the efficacy and safety of docetaxel in patients with paclitaxel-resistant metastatic breast cancer (MBC). PATIENTS AND METHODS: Docetaxel (100 mg/m2) was administered every 3 weeks to 46 patients registered at four centers. Patients had previously received < or = two chemotherapy regimens for MBC. All patients had progressive disease while receiving paclitaxel therapy. Treatment was repeated until there was evidence of disease progression or for a maximum of three cycles after best response. RESULTS: Objective responses were seen in eight of 44 assessable patients (18.1%; 95% confidence interval [CI], 6.7% to 29.5%). Seven patients had partial responses and one patient responded completely. Response rates were not significantly different by previously received paclitaxel dose or resistance. No responses were seen in 12 patients who had previously received paclitaxel by 24-hour infusion, but the response rate in 32 patients who had received paclitaxel by 1- to 3-hour infusion was 25%. The median response duration was 29 weeks and the median time to disease progression was 10 weeks. Median survival was 10.5 months. Clinically significant (severe) adverse events included neutropenic fever (24% of patients), asthenia (22%), infection (13%), stomatitis (9%), neurosensory changes (7%), myalgia (7%), and diarrhea (7%). CONCLUSION: Docetaxel is active in patients with paclitaxel-resistant breast cancer, particularly in those who failed to respond to brief infusions of paclitaxel. Response rates were comparable to or better than those seen with other therapies for patients with paclitaxel-resistant MBC. This confirms preclinical studies, which indicated only partial cross-resistance between paclitaxel and docetaxel.

Factors determining outcome for breast-conserving irradiation with margin-directed dose escalation to the tumor bed.

PURPOSE: A prospectively applied treatment policy for breast-conserving therapy used margin assessment as the exclusive guide to the intensity of therapy directed at the tumor-bearing quadrant. METHODS AND MATERIALS: From 1982-1994, there were 509 treated Stage I and II breast carcinomas with a median follow-up of 72 months. For operational purposes, tumor excision margins were prospectively defined as: > 5 mm, 2.1-5 mm, > 0 < or = 2 mm, and positive. If a margin was assessed as < or = 2 mm or indeterminate, and it was deemed cosmetically feasible, a reexcision of the tumor bed would be performed. All patients received whole breast irradiation to 50-50.4 Gy. The following scheme for tumor bed boost irradiation as a function of final margin status (FMS) was observed: (a) Minimal risk = no tumor found on reexcision, no boost performed; (b) low risk = FMS > 5 mm, boost of 10 Gy; intermediate risk = FMS 2.1-5 mm, boost to 14 Gy; high risk = FMS < or = 2 mm or positive, boost to 20 Gy. Cases were analyzed for local failure (LF) with respect to histology (invasive ductal (IDC), IDC with associated DCIS (IDC/DCIS), invasive lobular (ILC)), age, tumor size, total excision volume, reexcision, total dose, tamoxifen therapy, and chemotherapy. RESULTS: There were 19 breast recurrences for a Kaplan-Meier local failure rate for all cases at 5 and 10 years of 2.7% and 7.1%, respectively. Local failure in the first 4 years of follow-up was rare, with a mean annual incidence rate of 0.25% that rose to a mean of 1.1% in subsequent years. Univariate results of Cox proportional hazards regression survival models found positive FMS (p = 0.02), IDC/DCIS (p = 0.04) and age (0.0006) as significantly associated with local failure. In a multivariable model of FMS and IDC/DCIS, FMS retained significance (p = 0.01) but IDC/DCIS was borderline (p = 0.06). When FMS and age were included in a multivariable model, there was a significant interaction (p = 0.01) between the two variables. There was a significant increase in the relative risk of LF for age < or = 45 years (range 11.1-17.4), irrespective of FMS category. Although excellent overall control rates were achieved for patients > 45 years, for younger patients LF rates appeared to remain proportional to the relative closeness of the FMS, despite rigorous dose escalation. CONCLUSIONS: Graded tumor-bed dose escalation in response to FMS results in an exceptionally low risk of "early" local recurrence within the first 5 years of follow-up. However, this strategy is unable to completely overcome the longer term adverse influence of young age and positive FMS.

The effects of postradiation treatment with tamoxifen on local control and cosmetic outcome in the conservatively treated breast.

BACKGROUND: The aim of this study was to evaluate the impact on disease recurrence and cosmetic outcome of tamoxifen treatment initiated after breast-conserving therapy (BCT). METHODS: Between 1982 and 1994, 498 women (509 breasts) were treated with BCT in accordance with a highly standardized institutional protocol. Adjuvant tamoxifen was administered to 130 patients (134 breasts), beginning 1-6 weeks after irradiation. The median ages and duration of follow-up for groups who received tamoxifen (TAM+) and no tamoxifen (TAM-) were 62.5 years/56 months and 53 years/60 months, respectively. The members of the TAM+ group were significantly older (P = 0.0001) and had increased incidences of positive axillary lymph nodes or undissected axilla (P = 0.001). There was a significant (P = 0.001) difference between the TAM+ and TAM- groups in the distribution of histopathologic subtypes; this reflected an increased proportion of associated ductal carcinoma in situ in the TAM- group. More extensive regional lymphatic irradiation was administered to the TAM+ group. Chemotherapy was administered to 15% of TAM+ and 28% (P = 0.003) of TAM- patients. There were no significant differences between the groups with respect to tumor size, reexcision, total excised tissue volume, final margin status, total radiation dose, or use of interstitial implant boost. RESULTS: There was no significant difference between the TAM+ and TAM- groups in the overall distribution of cosmetic scores (P = 0.18). The 5-, 7-, and 10-year actuarial local failure rates for TAM+ versus TAM- patients were 0% versus 3.1%, 1.9% versus 5.4%, and 1.9% versus 8.4%, respectively. Multivariate regression analyses of potentially confounding variables revealed no significant associations between tamoxifen and either cosmetic outcome or local failure. CONCLUSIONS: Radiotherapy followed by tamoxifen has no adverse interactive effect on cosmesis, and tamoxifen is associated with a trend toward enhanced 5-year local control probability.

Acquired free protein S deficiency associated with multiple myeloma: a case report.

Investigation of recurrent venous thromboembolic events in a 46-year-old man with progressive IgG kappa (total serum IgG, 74.3 mg/ml) multiple myeloma revealed profound reductions in free protein S (PS) antigen (<0.l U/ml) and PS activity (0.33 U/ml). Total PS antigen, protein C, antithrombin III, and C4b-binding protein levels were within normal limits. The patient had no family history suggestive of a congenital PS deficiency and no history of thrombosis predating the diagnosis of his plasma cell dyscrasia. Patient IgG was isolated from serum using a protein A-sepharose affinity column and characterized. PS-dependent clotting assays (Staclot Protein S, Diagnostica Stago, Asnieres sur-Seine, France) performed on normal pooled plasma mixed with dilutions of patient IgG (0.0-33.0 mg/ml) revealed a dose-dependent neutralization of PS activity by 43%. Total and free PS antigen levels were measured using Laurell rocket electroimmunodiffusion (Assera-Plate Protein S, Diagnostica Stago), which revealed a similar dose-dependent reduction in free PS antigen but preserved normal total PS antigen. Free PS antigen was reduced by 77% to 0.23 U/ml using an IgG concentration (16.5 mg/ml) less than one-fourth of that of the patient at time of serum collection. Specific binding of the patient IgG to commercially available purified human PS was demonstrated by Western immunoblot analysis. Whereas acquired free PS deficiency has been previously reported in association with nephrotic syndrome, inflammatory bowel disease, HIV infection, and varicella infection, this is the first reported case of a hypercoagulable syndrome associated with acquired free PS deficiency and multiple myeloma.

Large-volume leukapheresis for collection of mononuclear cells for hematopoietic rescue in Hodgkin's disease.

BACKGROUND: Peripheral blood mononuclear cells (MNCs) collected by leukapheresis contain hematopoietic stem and progenitor cells that provide autologous hematopoietic rescue after high-dose chemotherapy, an approach that offers a significant benefit to patients with recurrent Hodgkin's disease. However, patients with low MNC counts may require 10 or more standard leukapheresis procedures for the collection of sufficient cells for hematopoietic rescue. STUDY DESIGN AND METHODS: The effectiveness of steady-state large-volume leukapheresis (LVL; 15-35 L blood processed) was evaluated as a method for collecting MNCs for hematopoietic rescue in seven patients with recurrent Hodgkin's disease. LVL was performed on 2 consecutive days per week to collect 7 x 10(8) MNCs per kg. The circulating MNC counts on the first day of LVL and the total numbers of LVL, of MNCs collected, and of liters of blood processed were determined per patient. After high-dose chemotherapy and MNC transfusion, days to granulocyte and platelet engraftment were recorded. RESULTS: On the first day of LVL, patients had median circulating MNCs of 1536 (range, 504-3950) x 10(6) per L. The median number of LVL procedures per patient was four (range, 1.25-6), and the median L per kg of blood processed was 1.57 (range, 0.38-4.03). Simple regression analysis plotting L per kg against initial MNCs gave a curve with the equation y = e(1.42-(6.31 x 10E-4)x) (correlation coefficient = -0.97, R2 = 0.95, exponential fit). Without posttransfusion growth-factor support, median days to granulocyte engraftment were 19 (range, 12-26) and those to platelet transfusion independence were 34.5 (range, 10-57). CONCLUSION: LVL provides a useful method of collecting MNCs for hematopoietic rescue in patients with Hodgkin's disease. The patient's baseline MNC count provides a useful estimate of the volume required for LVL.

Phase I/II study of cyclophosphamide, carboplatin, and etoposide and autologous hematopoietic stem-cell transplantation with posttransplant interferon alfa-2b for patients with lymphoma and Hodgkin's disease.

PURPOSE: To evaluate the safety and toxicity of interferon alfa-2b (IFN) following an intensive preparative transplantation regimen in patients with relapsed Hodgkin's disease (HD) and non-Hodgkin's lymphoma (NHL). PATIENTS AND METHODS: Thirty-two patients with NHL or HD underwent autologous transplantation following cyclophosphamide 7,200 mg/m2, carboplatin 1,600 mg/m2, and etoposide 1,600 mg/m2 (CCV). Fourteen patients received an escalating dose of IFN. IFN was started at 1 x 10(6) U/m2 subcutaneously (SC) three times per week with a monthly dose escalation to a maximum of 3 x 10(6) U/m2 SC three times per week. IFN was continued for a total of 6 months. RESULTS: The preparative regiment was well tolerated. Renal dysfunction was noted more frequently in patients with a history of pretransplant cisplatin treatment, and cardiac dysfunction was responsible for the single transplant-related death (3%). IFN was well tolerated with no serious complications. Transient neutropenia and thrombocytopenia were noted in several patients. The mean maximal-dose IFN achieved was 2 x 10(6) IU/m2. The median duration of treatment with IFN was 5.2 months. The overall probability of survival (OS) and event-free survival (EFS) at 36 months, with a median follow-up duration of 18 months, was 42% OS and 14% EFS in HD and 70% OS and 56% EFS in NHL. The EFS at 36 months was 73% for all NHL patients who received IFN and 50% for patients who refused IFN treatment (P = .12), with OS estimates of 100% in the IFN group and 35% in the untreated group (P = .0002). CONCLUSION: CCV is a safe, effective conditioning regimen in patients with NHL or HD. Posttransplant IFN can be safely administered at 2.0 x 10(6) U/m2 three times per week for 6 months and may have a meaningful antitumor effect.

Breast conservation in elderly women for clinically negative axillary lymph nodes without axillary dissection.

BACKGROUND: A prospective study was initiated to explore an approach of limited therapy in elderly patients with early clinical stage breast cancer. METHODS: Between 1982 and 1989, 73 women with American Joint Committee on Cancer Stage I/II, clinically negative axillary lymph nodes aged 65 years or older (median age, 74 years) were enrolled in a treatment program consisting of tumor excision, breast and regional lymph node irradiation, and, in 66 patients, tamoxifen. Patients were assessed for disease outcome and complications. RESULTS: At a median follow-up of 54 months, 8-year rates of local and regional lymph node control were 92.5% and 100%, respectively. Eight-year probabilities of disease free, overall, and breast cancer specific survival were 84%, 52.5%, and 93.8%, respectively. There was minimal morbidity associated with either regional irradiation or tamoxifen. CONCLUSIONS: An approach to early breast cancer in the elderly that seeks to limit the aggressiveness of local and systemic therapies appears to result in a satisfactory disease outcome with few complications.

Adjusted-dose continuous-infusion cyclosporin A to prevent graft-versus-host disease following allogeneic bone marrow transplantation.

Graft-versus-host disease (GVHD) remains a major obstacle to allogeneic bone marrow transplantation. We administered cyclosporin A (CsA) by continuous intravenous infusion for prophylaxis against GVHD and adjusted the dose to maintain a constant whole blood level. Forty-five patients, ranging in age from 16 to 56, mean 39.5 years, undergoing allogeneic transplantation for various hematological malignancies received CsA as a continuous intravenous infusion. CsA was started on day -1 and continued until day +22 when oral CsA was initiated. The whole blood level of CsA was determined and the dose adjusted to maintain a fixed level. Methotrexate 15 mg/m2 i.v. was given on day +1, followed by 10 mg/m2 on days +3 and +6. CsA administered as a continuous infusion was well tolerated. All patients required multiple adjustments of the infused dose of CsA to maintain the targeted whole blood level. The mean rise in creatinine was 0.89 mg/dl. There was an association between the concomitant administration of amphotericin B and CsA and the development of nephrotoxicity. Hypertension developed in 30/45 patients, and all responded to oral nifedipine. Tremors were noted in 16/45 patients. None of the patients developed serious neurological side effects. Greater than grade-I acute GVHD developed in only 13% of the patients. We conclude that administering CsA as an adjusted dose by continuous intravenous infusion is well tolerated and effective in preventing acute GVHD in patients undergoing allogeneic bone marrow transplantation.

Integrin alpha IIb beta 3 mediates binding of the Lyme disease agent Borrelia burgdorferi to human platelets.

Lyme disease is a chronic, multisystemic infection caused by the tick-borne spirochete Borrelia burgdorferi. Attachment of the spirochete to host cells via specific receptors is likely to be important in the establishment of infection. B. burgdorferi have previously been shown to bind to a variety of mammalian cells in vitro. Here we demonstrate that binding of B. burgdorferi to human platelets is mediated by the integrin alpha IIb beta 3 (glycoprotein IIb-IIIa), a critical receptor in thrombosis and hemostasis. Functional expression of this receptor requires platelet activation, and binding of the spirochete was observed only to activated platelets. Binding was inhibited by a synthetic Arg-Gly-Asp peptide that blocks ligand interaction with many integrins and by a synthetic peptide based on the gamma chain of fibrinogen that blocks binding to alpha IIb beta 3. In addition, attachment of the spirochete to platelets was inhibited by monoclonal antibodies directed against alpha IIb beta 3 that are known to block ligand-receptor interaction. No inhibition was seen with control peptides or with antibodies directed against other platelet receptors. B. burgdorferi bound efficiently to purified alpha IIb beta 3 but did not bind to platelets deficient in this integrin. Efficient platelet binding was displayed by a cloned, infectious B. burgdorferi strain, whereas a cloned noninfectious strain did not bind to platelets. Binding to integrins may be important for the ability of B. burgdorferi to establish infection in the diverse tissues affected by Lyme disease.

P-selectin and wound healing.

The history of the wound can by some accounts be traced nearly 5,000,000 years in the prehistoric ancestry of man (Majno, 1991). While there have been many descriptive accounts of the wound and wound healing over the centuries, in recent years rapid advances in the field of adhesion biology have added greatly to the understanding of the wound. Disruptions in the continuity of the vessel wall, whether by trauma or disease, induce a number of physiologic responses. The endothelium responds to fibrin contact in numerous ways including the rapid release of stored of von Willebrand factor and the expression of P-selectin upon the cell surface. Deposition of fibrin at the site of vascular injury serves other vital roles in the acute response to injury. Fibrin deposition stabilizes platelets as part of the development of a mural thrombus. Fibrin may also act to serve as a biological scaffold upon which inflammatory cells may adhere and participate in the acute response to injury. Finally, it is apparent that fibrin may act as a lattice upon which fibroblasts, smooth muscle cells and endothelial cells may adhere and migrate in order to return the vessel to its original state. In tumorigenesis, fibrinogen and fibrin may deposit in the perivascular space within the tumor and contribute by incompletely understood mechanisms to tumor growth and metastasis. The understanding of fibrin induced endothelial cell responses and how P-selectin and other endothelial cell adhesion molecules function in wound healing is important for understanding the vascular response to injury.

Activated platelets induce endothelial secretion of interleukin-8 in vitro via an interleukin-1-mediated event.

Migration of neutrophils through endothelial cells (EC) and induction of cytokine secretion are two well-documented events during the inflammatory reaction. The inflammatory, chemotactic cytokine interleukin-8 (IL-8) is secreted by EC in response to IL-1 stimulation. In this study, we show that platelets activated with either adenosine-5'-diphosphate or epinephrine induce IL-8 secretion by EC. This stimulatory activity was found to be associated with sedimented platelets after activation. Blockade of IL-1 receptors on EC with IL-1 receptor antagonist (IL-1Ra) decreased the stimulatory effect of whole activated platelet preparations by 59% (P < .05). Similarly, IL-1Ra pretreatment of EC reduced the stimulatory effect of sedimented activated platelets by 60% (P < .01). In addition, we treated human blood donors with 750 mg of oral aspirin, and evaluated the stimulatory effect of epinephrine-activated platelets on IL-8 secretion by EC. IL-8 synthesis after aspirin ingestion was inhibited by 90% (P < .01) as compared with the preaspirin stimulation. These observations show that activated platelets induce IL-8 secretion via membrane-associated IL-1 activity, and provide a novel relationship between coagulation and inflammation that could be relevant to several diseases.

A 130-kDa protein on endothelial cells binds to amino acids 15-42 of the B beta chain of fibrinogen.

Factors which stimulate the release of von Willebrand factor (vWf) from endothelial cell Weibel-Palade bodies and which induce the expression of the leukocyte-binding adhesion molecule P-selectin (PADGEM, GMP-140, CD62) on the endothelial cell surface remain incompletely characterized. Fibrin but not fibrinogen is a potent stimulus for the release of stored von Willebrand factor from endothelial cells. Removal of fibrinopeptides A and B from fibrinogen occurs during the formation of fibrin, and the removal of fibrinopeptide B is a requirement for fibrin to induce vWf secretion. The cleavage of fibrinopeptide A by reptilase enzyme forms a fibrin gel yet it is incapable of stimulating Weibel-Palade body degranulation. As a consequence of removing fibrinopeptide B, B beta 15-42 becomes the new NH2 terminus of the beta chain of fibrin. We have shown that the peptide B beta 15-42 in solution inhibits the release of vWf stimulated by fibrin. In addition, B beta 15-42 coupled to ovalbumin supports the binding and spreading of endothelial cells, while a scrambled form of this peptide coupled to the same carrier does not. We investigated whether these determinants near the amino terminus of the beta chain of fibrin bind to a specific protein on the surface of endothelial cells. A 130-kDa protein was isolated from surface-labeled human umbilical vein endothelial cells by specific binding to B beta 15-42 immobilized on Sepharose. This glycoprotein was eluted with the B beta 15-42 peptide in solution but not with the scrambled form of this peptide. The fibrin-derived peptides B beta 19-26 and B beta 37-56-cysteine were also incapable of eluting the 130-kDa protein bound to immobilized B beta 15-42 as were the arginine-glycine-aspartic acid-serine RGDS tetrapeptide and EDTA. The 130-kDa protein is recognized neither by antibodies to the known integrins found on endothelial cells nor by antibodies to CD31 (endoCAM, PECAM-1), a member of the immunoglobulin family of receptors found on endothelial cells. The beta chain of fibrin thus contains a sequence near its amino terminus which specifically binds to what is likely a novel endothelial cell surface protein. This glycoprotein may promote endothelial cell adhesion to fibrin during the wound healing process and is a candidate for a receptor involved in fibrin-mediated release of Weibel-Palade bodies from endothelial cells.

PADGEM protein: a receptor that mediates the interaction of activated platelets with neutrophils and monocytes.

PADGEM (platelet activation dependent granule-external membrane protein) is an integral membrane protein of the alpha granules of platelets and Weibel-Palade bodies of endothelial cells that is expressed on the plasma membrane upon cell activation and granule secretion. Activated platelets, but not resting platelets, bind to neutrophils, monocytes, HL60 cells, and U937 cells. This interaction is inhibited by anti-PADGEM antibodies, PADGEM, and EDTA; anti-GPIIb-IIIa, anti-thrombospondin, anti-GPIV, and thrombospondin produce no effect. Neutrophils and U937 cells, in contrast to Jurkatt cells, contain PADGEM recognition sites, as shown by binding of PADGEM contained in phospholipid vesicles. These results indicate that PADGEM mediates adhesion of activated platelets to monocytes and neutrophils. Therefore, PADGEM shares not only structural but also functional homology with ELAM-1 and MEL-14, members of a new family of vascular cell adhesion molecules.