Protracted fibrinolysis resistance following cardiac surgery with cardiopulmonary bypass: A prospective observational study of clinical associations and patient outcomes

BACKGROUND

Surgery on cardiopulmonary bypass (CPB) elicits a pleiomorphic systemic host response which, when severe, requires prolonged intensive care support. Given the substantial cross-talk between inflammation, coagulation, and fibrinolysis, the aim of this hypothesis-generating observational study was to document the kinetics of fibrinolysis recovery post-CPB using ClotPro® point-of-care viscoelastometry. Tissue plasminogen activator-induced clot lysis time (TPA LT, s) was correlated with surgical risk, disease severity, organ dysfunction and intensive care length of stay (ICU LOS).

RESULTS

In 52 patients following CPB, TPA LT measured on the first post-operative day (D1) correlated with surgical risk (EuroScore II, Spearman's rho .39, p < .01), time on CPB (rho = .35, p = .04), disease severity (APACHE II, rho = .52, p < .001) and organ dysfunction (SOFA, rho = .51, p < .001) scores, duration of invasive ventilation (rho = .46, p < .01), and renal function (eGFR, rho = -.65, p < .001). In a generalized linear regression model containing TPA LT, CPB run time and markers of organ function, only TPA LT was independently associated with the ICU LOS (odds ratio 1.03 [95% CI 1.01-1.05], p = .01). In a latent variables analysis, the association between TPA LT and the ICU LOS was not mediated by renal function and thus, by inference, variation in the clearance of intraoperative tranexamic acid.

CONCLUSIONS

This observational hypothesis-generating study in patients undergoing cardiac surgery with cardiopulmonary bypass demonstrated an association between the severity of fibrinolysis resistance, measured on the first post-operative day, and the need for extended postoperative ICU level support. Further examination of the role of persistent fibrinolysis resistance on the clinical outcomes in this patient cohort is warranted through large-scale, well-designed clinical studies.

Targeting RNA Polymerase I Transcription Activity in Osteosarcoma: Pre-Clinical Molecular and Animal Treatment Studies

The survival rate of patients with osteosarcoma (OS) has not improved over the last 30 years. Mutations in the genes TP53, RB1 and c-Myc frequently occur in OS and enhance RNA Polymerase I (Pol I) activity, thus supporting uncontrolled cancer cell proliferation. We therefore hypothesised that Pol I inhibition may be an effective therapeutic strategy for this aggressive cancer. The Pol I inhibitor CX-5461 has demonstrated therapeutic efficacy in different cancers in pre-clinical and phase I clinical trials; thus, the effects were determined on ten human OS cell lines. Following characterisation using genome profiling and Western blotting, RNA Pol I activity, cell proliferation and cell cycle progression were evaluated in vitro, and the growth of TP53 wild-type and mutant tumours was measured in a murine allograft model and in two human xenograft OS models. CX-5461 treatment resulted in reduced ribosomal DNA (rDNA) transcription and Growth 2 (G2)-phase cell cycle arrest in all OS cell lines. Additionally, tumour growth in all allograft and xenograft OS models was effectively suppressed without apparent toxicity. Our study demonstrates the efficacy of Pol I inhibition against OS with varying genetic alterations. This study provides pre-clinical evidence to support this novel therapeutic approach in OS.

Targeting Mutant Dicer Tumorigenesis in Pleuropulmonary Blastoma via Inhibition of RNA Polymerase I

DICER1 mutations predispose to increased risk for various cancers, particularly pleuropulmonary blastoma (PPB), the commonest lung malignancy of childhood. There is a paucity of directly actionable molecular targets as these tumors are driven by loss-of-function mutations of DICER1. Therapeutic development for PPB is further limited by a lack of biologically and physiologically-representative disease models. Given recent evidence of Dicer's role as a haploinsufficient tumor suppressor regulating RNA polymerase I (Pol I), Pol I inhibition could abrogate mutant Dicer-mediated accumulation of stalled polymerases to trigger apoptosis. Hence, we developed a novel sub-pleural orthotopic PPB patient-derived xenograft (PDX) model that retained both RNase IIIa and IIIb hotspot mutations and recapitulated the cardiorespiratory physiology of intra-thoracic disease, and with it evaluated the tolerability and efficacy of first-in-class Pol I inhibitor CX-5461. In PDX tumors, CX-5461 significantly reduced H3K9 di-methylation and increased nuclear p53 expression, within 24 hours' exposure. Following treatment at the maximum tolerated dosing regimen (12 doses, 30mg/kg), tumors were smaller and less hemorrhagic than controls, with significantly decreased cellular proliferation, and increased apoptosis. As demonstrated in a novel intra-thoracic tumor model of PPB, Pol I inhibition with CX-5461 could be a tolerable and clinically-feasible therapeutic strategy for mutant Dicer tumors, inducing anti-tumor effects by decreasing H3K9 methylation and enhancing p53-mediated apoptosis.

Point-of-care diagnosis and monitoring of fibrinolysis resistance in the critically ill: results from a feasibility study

BACKGROUND

Fibrinolysisis is essential for vascular blood flow maintenance and is triggered by endothelial and platelet release of tissue plasminogen activator (t-PA). In certain critical conditions, e.g. sepsis, acute respiratory failure (ARF) and trauma, the fibrinolytic response is reduced and may lead to widespread thrombosis and multi-organ failure. The mechanisms underpinning fibrinolysis resistance include reduced t-PA expression and/or release, reduced t-PA and/or plasmin effect due to elevated inhibitor levels, increased consumption and/or clearance. This study in critically ill patients with fibrinolysis resistance aimed to evaluate the ability of t-PA and plasminogen supplementation to restore fibrinolysis with assessment using point-of-care ClotPro viscoelastic testing (VET).

METHODS

In prospective, observational studies, whole-blood ClotPro VET evaluation was carried out in 105 critically ill patients. In 32 of 58 patients identified as fibrinolysis-resistant (clot lysis time > 300 s on the TPA-test: tissue factor activated coagulation with t-PA accelerated fibrinolysis), consecutive experimental whole-blood VET was carried out with repeat TPA-tests spiked with additional t-PA and/or plasminogen and the effect on lysis time determined. In an interventional study in a patient with ARF and fibrinolysis resistance, the impact of a 24 h intravenous low-dose alteplase infusion on coagulation and fibrinolysis was prospectively monitored using standard ClotPro VET.

RESULTS

Distinct response groups emerged in the ex vivo experimental VET, with increased fibrinolysis observed following supplementation with (i) t-PA only or (ii) plasminogen and t-PA. A baseline TPA-test lysis time of > 1000 s was associated with the latter group. In the interventional study, a gradual reduction (25%) in serial TPA-test lysis times was observed during the 24 h low-dose alteplase infusion.

CONCLUSIONS

ClotPro viscoelastic testing, the associated TPA-test and the novel experimental assays may be utilised to (i) investigate the potential mechanisms of fibrinolysis resistance, (ii) guide corrective treatment and (iii) monitor in real-time the treatment effect. Such a precision medicine and personalised treatment approach to the management of fibrinolysis resistance has the potential to increase treatment benefit, while minimising adverse events in critically ill patients.

TRIAL REGISTRATION

VETtiPAT-ARF, a clinical trial evaluating ClotPro-guided t-PA (alteplase) administration in fibrinolysis-resistant patients with ARF, is ongoing (ClinicalTrials.gov NCT05540834 ; retrospectively registered September 15th 2022).

Achieving haemostasis in thrombocytopenia in remote settings: an in vitro comparison of frozen and lyophilized products

BACKGROUND

Platelet concentrates have a limited shelf life due to room temperature storage and therefore, are not kept in regional centres where turnover is low. Cryopreserved platelets have been proposed as an alternative to platelet transfusion in austere circumstances and fibrinogen concentrate has improved thromboelastometry parameters in thrombocytopenia. This study compared the ability of stored haemostatic products and platelets to correct thromboelastometry parameters in thrombocytopenia.

MATERIALS AND METHODS

Blood from eight patients with severe thrombocytopenia was combined with platelet concentrates, cryoprecipitate, fibrinogen concentrate, factor VIII, factor XIII and cryopreserved platelets in ratios equivalent to transfusion. Tissue factor initiated thromboelastometry (EXTEM) was compared between the products.

RESULTS

EXTEM amplitude at 20 minutes (A20) improved by 13.1 mm with platelets (p<0.01). The 5mm increase in A20 seen with cryoprecipitate (p=0.06) was not statistically different from platelets (p=0.19). No improvement in A20 was observed with cryopreserved platelets or factor concentrates. EXTEM clotting times (CT) improved with cryopreserved platelets (19.4 s, p=0.001) and cryoprecipitate (24.1 s, p<0.05), but not fibrinogen, and both were superior to platelets (9.9 s, p<0.05). Clotting concentrates did not improve EXTEM parameters although further studies suggested the improvement in A20 was largely driven by higher fibrinogen concentrations in cryoprecipitate.

DISCUSSION

These results suggest that cryopreserved platelets enhance clot initiation but do not contribute to clot strength in thrombocytopenia. When platelets are not available for transfusion, cryoprecipitate may be of value, however this requires further clinical studies.

Superior Hemostatic and Wound-Healing Properties of Gel and Sponge Forms of Non-Oxidized Cellulose Nanofibers: In Vitro and In Vivo Studies

Many materials have been engineered and commercialized as hemostatic agents. However, there is still a gap in the availability of hemostats that offer biocompatibility and biodegradability in combination with effective hemostatic properties. Cellulose nanofibers were investigated as hemostatic materials with most studies focusing on oxidized cellulose-derived hemostats. Our recent studies demonstrated that by optimizing the morphological properties of non-oxidized cellulose nanofibers (CNFs) enhanced hemostasis is achieved. Herein, we investigate the hemostatic and wound-healing properties of CNFs with optimized morphology using two forms, gel and sponge. In vitro thromboelastometry studies demonstrate that CNFs reduce clotting time by 68% (±SE 2%) and 88% (±SE 5%) in gel and sponge forms, respectively. In an in vivo murine liver injury model, CNFs significantly reduce blood loss by 38% (±SE 10%). The pH-neutral CNFs do not damage red blood cells, nor do they impede the proliferation of fibroblast or endothelial cells. Subcutaneously-implanted CNFs show a foreign body reaction resolving with the degradation of CNFs on histological examination and there is no scarring in the skin after 8 weeks. Demonstrating superior hemostatic performance in a variety of forms, as well as biocompatibility and biodegradability, CNFs hold significant potential for use in surgical and first-aid environments. This article is protected by copyright. All rights reserved.

Interactions with Asialo-Glycoprotein Receptors and Platelets Are Dispensable for CD8+ T Cell Localization in the Murine Liver

Liver-resident CD8⁺ T cells can play critical roles in the control of pathogens, including Plasmodium and hepatitis B virus. Paradoxically, it has also been proposed that the liver may act as the main place for the elimination of CD8⁺ T cells at the resolution of immune responses. We hypothesized that different adhesion processes may drive residence versus elimination of T cells in the liver. Specifically, we investigated whether the expression of asialo-glycoproteins (ASGPs) drives the localization and elimination of effector CD8⁺ T cells in the liver, while interactions with platelets facilitate liver residence and protective function. Using murine CD8⁺ T cells activated in vitro, or in vivo by immunization with Plasmodium berghei sporozoites, we found that, unexpectedly, inhibition of ASGP receptors did not inhibit the accumulation of effector cells in the liver, but instead prevented these cells from accumulating in the spleen. In addition, enforced expression of ASGP on effector CD8⁺ T cells using St3GalI-deficient cells lead to their loss from the spleen. We also found, using different mouse models of thrombocytopenia, that severe reduction in platelet concentration in circulation did not strongly influence the residence and protective function of CD8⁺ T cells in the liver. These data suggest that platelets play a marginal role in CD8⁺ T cell function in the liver. Furthermore, ASGP-expressing effector CD8⁺ T cells accumulate in the spleen, not the liver, prior to their destruction.

The therapeutic potential of RNA Polymerase I transcription inhibitor, CX-5461, in uterine leiomyosarcoma

Background. Uterine leiomyosarcoma is a rare aggressive smooth muscle cancer with poor survival rates. RNA Polymerase I (Pol I) activity is elevated in many cancers supporting tumour growth and prior studies in uterine leiomyosarcoma revealed enlarged nucleoli and upregulated Pol I activity-related genes. This study aimed to investigate the anti-tumour potential of CX-5461, a Pol I transcription inhibitor currently being evaluated in clinical trials for several cancers, against the human uterine leiomyosarcoma cell line, SK-UT-1. Methods. SK-UT-1 was characterised using genome profiling and western blotting. The anti-tumour effects of CX-5461 were investigated using cell proliferation assays, expression analysis using qRT-PCR, and BrdU/PI based cell cycle analysis. Results. Genetic analysis of SK-UT-1 revealed mutations in TP53, RB1, PTEN, APC and TSC1 & 2, all potentially associated with increased Pol I activity. Protein expression analysis showed dysregulated p53, RB1 and c-Myc. CX-5461 treatment resulted in an anti-proliferation response, G2 phase cell-cycle arrest and on-target activity demonstrated by reduced ribosomal DNA transcription. Conclusions. SK-UT-1 was confirmed as a representative model of uterine leiomyosarcoma and CX-5461 has significant potential as a novel adjuvant for this rare cancer.

Cryoprecipitate as an alternative to platelet transfusion in thrombocytopenia

Platelet transfusions are not always available for bleeding in severe thrombocytopenia, as storage outside of major centers is limited by their short shelf-life. Data are lacking to support alternative available blood products; however, additional fibrinogen has been shown to enhance clot formation in vitro. To test the hypothesis that cryoprecipitate supplementation could improve clot formation in severe thrombocytopenia, eight hematological malignancy patients with platelet counts under 10 × 109/L each had 10 units of apheresis cryoprecipitate transfused prior to planned prophylactic platelet transfusions. The primary endpoint of thromboelastometry amplitude at 20 min increased by a mean of 5.1 mm (p < 0.01) following cryoprecipitate transfusion despite persisting thrombocytopenia. Thromboelastometry clotting times reduced by a mean of 7.8 s (p < 0.05) and alpha angle increased by a mean of 10.6⁰ (p < 0.01). These results are consistent with cryoprecipitate enhancing the strength of the fibrin/platelet meshwork within the forming thrombus. While platelet transfusion remains the standard of care, where platelet supplies are limited, these data provide a rationale for the use of cryoprecipitate to obtain hemostasis in bleeding thrombocytopenic patients.

Circulating platelet-neutrophil aggregates characterize the development of type 1 diabetes in humans and NOD mice

Platelet-neutrophil aggregates (PNAs) facilitate neutrophil activation and migration and could underpin the recruitment of neutrophils to the pancreas during type 1 diabetes (T1D) pathogenesis. PNAs, measured by flow cytometry, were significantly elevated in the circulation of autoantibody-positive (Aab⁺) children and new-onset T1D children, as well as in pre-T1D (at 4 weeks and 10–12 weeks) and T1D-onset NOD mice, compared with relevant controls, and PNAs were characterized by activated P-selectin⁺ platelets. PNAs were similarly increased in pre-T1D and T1D-onset NOD isolated islets/insulitis, and immunofluorescence staining revealed increased islet-associated neutrophil extracellular trap (NET) products (myeloperoxidase [MPO] and citrullinated histones [CitH3]) in NOD pancreata. In vitro, cell-free histones and NETs induced islet cell damage, which was prevented by the small polyanionic drug methyl cellobiose sulfate (mCBS) that binds to histones and neutralizes their pathological effects. Elevated circulating PNAs could, therefore, act as an innate immune and pathogenic biomarker of T1D autoimmunity. Platelet hyperreactivity within PNAs appears to represent a previously unrecognized hematological abnormality that precedes T1D onset. In summary, PNAs could contribute to the pathogenesis of T1D and potentially function as a pre-T1D diagnostic.

Non-oxidized cellulose nanofibers as a topical hemostat: In vitro thromboelastometry studies of structure vs function

Hemorrhage remains a significant cause of morbidity and mortality following trauma and during complex surgeries. A variety of nanomaterials, including oxidized cellulose nanofibers (OCNFs), have been studied to overcome the disadvantages of current commercial topical hemostats. However, the relationship between nano-structural characteristics and hemostatic efficacy of non-oxidized cellulose nanofibers (CNFs) has not been elucidated. Herein, we present the first report of the correlation between structure and hemostatic performance of CNFs. In vitro thromboelastometry studies on CNFs, synthesized by ball-milling, showed that there is an optimum balance point between the aspect ratio (AR) and specific surface area (SSA) of nanofibers in terms of their maximum contribution to platelet function and plasma coagulation. The optimized CNFs with high SSA (17 m²/g) and a high AR (166) shortened normal whole blood clotting time by 68 %, outperforming cellulose-based hemostats. Additionally, CNFs reduced clotting time in platelet-deficient blood (by 80 %) and heparinized blood (by 54 %).

Potential contrasting effects of platelets on the migration and invasion of sarcomas versus carcinomas

The ability of platelets to promote carcinoma and melanoma progression has been thoroughly studied and occurs in numerous ways. In contrast, the effect of platelets on sarcomas, tumors arising from mesenchymal cells, has received very little attention. This study was undertaken to simultaneously compare the effects of platelets on murine and human sarcomas and carcinomas. In contrast to their effect on carcinomas, platelets inhibited the invasion of some murine- and all human sarcomas tested in vitro. Further invasion studies with TGFβ treatment only partially recapitulated the results seen with whole platelets. In a spontaneous tumor growth and lung metastasis model, platelets promoted 4T1 mammary carcinoma metastasis but not MCA-1 fibrosarcoma metastasis. Gene expression analysis of the platelet-promoted MDA-MB-231 breast carcinoma, and the platelet-inhibited HT1080 fibrosarcoma cell lines revealed that exposure of MDA-MB-231 to platelets, resulted in upregulation of oncogenes and EMT-associated genes whereas in HT1080 a tumor-suppressor gene was significantly upregulated. Thus, this study has revealed a potential diametrically opposing effect of platelets on mesenchymal and epithelial cancers, a finding that warrants further investigation.

Fibrin exposure triggers αIIbβ3-independent platelet aggregate formation, ADAM10 activity and glycoprotein VI shedding in a charge-dependent manner

BACKGROUND

Collagen and fibrin engagement and activation of glycoprotein (GP) VI induces proteolytic cleavage of the GPVI ectodomain generating shed soluble GPVI (sGPVI). Collagen-mediated GPVI shedding requires intracellular signalling to release the sGPVI, mediated by A Disintegrin And Metalloproteinase 10 (ADAM10); however, the precise mechanism by which fibrin induces GPVI shedding remains elusive. Plasma sGPVI levels are elevated in patients with coagulopathies, sepsis, or inflammation and can predict onset of sepsis and sepsis-related mortality; therefore, it is clinically important to understand the mechanisms of GPVI shedding under conditions of minimal collagen exposure.

OBJECTIVES

Our aim was to characterize mechanisms by which fibrin-GPVI interactions trigger GPVI shedding.

METHODS

Platelet aggregometry, sGPVI ELISA, and an ADAM10 fluorescence resonance energy transfer assay were used to measure fibrin-mediated platelet responses.

RESULTS

Fibrin induced αIIbβ3-independent washed platelet aggregate formation, GPVI shedding, and increased ADAM10 activity, all of which were insensitive to pre-treatment with inhibitors of Src family kinases but were divalent cation- and metalloproteinase-dependent. In contrast, treatment of washed platelets with other GPVI ligands, collagen, and collagen-related peptide caused αIIbβ3-dependent platelet aggregation and GPVI release but did not increase constitutive ADAM10 activity.

CONCLUSIONS

Fibrin engages GPVI in a manner that differs from other GPVI ligands. Inclusion of polyanionic molecules disrupted fibrin-induced platelet aggregate formation and sGPVI release, suggesting that electrostatic charge may play a role in fibrin/GPVI engagement. It may be feasible to exploit this property and specifically disrupt GPVI/fibrin interactions whilst sparing GPVI/collagen engagement.Fibrin engages GPVI in a manner that differs from other GPVI ligands. Inclusion of polyanionic molecules disrupted fibrin-induced platelet aggregate formation and sGPVI release, suggesting that electrostatic charge may play a role in fibrin/GPVI engagement. It may be feasible to exploit this property and specifically disrupt GPVI/fibrin interactions whilst sparing GPVI/collagen engagement.

Novel scientific approaches and future research directions in understanding ITP

Diagnosis of immune thrombocytopenia (ITP) and prediction of response to therapy remain significant and constant challenges in hematology. In patients who present with ITP, the platelet count is frequently used as a surrogate marker for disease severity, and so often determines the need for therapy. Although there is a clear link between thrombocytopenia and hemostasis, a direct correlation between the extent of thrombocytopenia and bleeding symptoms, especially at lower platelet counts is lacking. Thus, bleeding in ITP is heterogeneous, unpredictable, and nearly always based on a multitude of risk factors, beyond the platelet count. The development of an evidence-based, validated risk stratification model for ITP treatment is a major goal in the ITP community and this review discusses new laboratory approaches to evaluate the various pathobiologies of ITP that may inform such a model.

GSTZ1 genotypes correlate with dichloroacetate pharmacokinetics and chronic side effects in multiple myeloma patients in a pilot phase 2 clinical trial

Dichloroacetate (DCA) is an investigational drug targeting the glycolytic hallmark of cancer by inhibiting pyruvate dehydrogenase kinases (PDK). It is metabolized by GSTZ1, which has common polymorphisms altering enzyme or promoter activity. GSTZ1 is also irreversibly inactivated by DCA. In the first clinical trial of DCA in a hematological malignancy, DiCAM (DiChloroAcetate in Myeloma), we have examined the relationship between DCA concentrations, GSTZ1 genotype, side effects, and patient response. DiCAM recruited seven myeloma patients in partial remission. DCA was administered orally for 3 months with a loading dose. Pharmacokinetics were performed on day 1 and 8. Trough and peak concentrations of DCA were measured monthly. GSTZ1 genotypes were correlated with drug concentrations, tolerability, and disease outcomes. One patient responded and two patients showed a partial response after one month of DCA treatment, which included the loading dose. The initial half-life of DCA was shorter in two patients, correlating with heterozygosity for GSTZ1*A genotype, a high enzyme activity variant. Over 3 months, one patient maintained DCA trough concentrations approximately threefold higher than other patients, which correlated with a low activity promoter genotype (-1002A, rs7160195) for GSTZ1. This patient displayed the strongest response, but also the strongest neuropathy. Overall, serum concentrations of DCA were sufficient to inhibit the constitutive target PDK2, but unlikely to inhibit targets induced in cancer. Promoter GSTZ1 polymorphisms may be important determinants of DCA concentrations and neuropathy during chronic treatment. Novel dosing regimens may be necessary to achieve effective DCA concentrations in most cancer patients while avoiding neuropathy.

Prevention of erythrocyte fragility and anaemia induced by extracellular histones

Introduction

Neutrophil extracellular traps (NETs) are released from neutrophils following activation by pathogens and/or tissue injury and exhibit anti-microbial activity. Uncontrolled formation of NETs can, however, become pathogenic, particularly via their associated histones, and induce endothelial cell death, systemic vascular obstruction, multiple organ failure and initiate coagulation by both activating platelets and damaging erythrocytes such that they become pro-thrombotic.

Study Objectives

Recently we discovered an additional effect of histones on erythrocyte, which is to enhance their fragility when they are subjected to shear stress associated with blood flow through the vascular system and spleen in particular. Our laboratory has synthesised a family of small polyanions (SPAs) which have been screened for their ability to neutralise the pathogenic effects of histones and NETs.

Methods

We have used a novel mechanically-induced shear stress method as well as an in vitro spleen filtration model to investigate the effects of mammalian histones ± SPAs, on RBC fragility. The in vitro findings were mirrored in vivo with the injection of histones and SPAs in mice.

Results

Our results revealed that free histones bind to erythrocytes with high affinity and render erythrocytes susceptible to lysis by shear stress in a dose-dependent manner and some SPAs could totally inhibit or reverse this phenomenon.

Conclusions

Based on these data we propose that erythrocytes can neutralise the damaging effects of histones in the circulation and also transport them to the spleen for disposal. Overload of this disposal system could cause the unexplained anaemia associated with sepsis, cancer and other pathological conditions.

Activation of tumour cell ECM degradation by thrombin-activated platelet membranes: potentially a P-selectin and GPIIb/IIIa-dependent process

The promotion of tumour metastasis by platelets may occur through several mechanisms including the induction of a more metastatic phenotype in tumour cells and assisted extravasation of circulating tumour cells. Whilst the mechanisms underlying platelet-assisted extravasation have been extensively studied, much less attention has been paid to the mechanisms underlying platelet promotion of an aggressive phenotype within a tumour cell population. Herein, we demonstrate in vitro that MDA-MB-231 breast carcinoma cells incubated with washed thrombin-activated platelet membranes adopt a Matrigel-degrading phenotype in a dose- and contact time-dependent manner. The same phenotypic change was observed with three other human tumour cell lines of diverse anatomical origin. Moreover, tumour cell lines that had been cultured with washed thrombin-activated platelet membranes had a greater metastatic capacity when injected into mice. This in vivo effect was reliant upon a co-incubation period of >2 h implying a mechanism involving more than platelet membrane binding that occurred within 5 min. Upon further investigation it was found that simultaneous blocking of the platelet-membrane proteins P-selectin and GPIIb/IIIa prevented interactions between platelet membranes and MDA-MB-231 cells but also significantly reduced the ability of tumour cells to degrade Matrigel. These results confirm that platelets induce a more aggressive phenotype in tumour cells but also identify the platelet proteins involved in this effect. P-selectin and GPIIb/IIIa also play a role in assisting tumour cell extravasation and, thus, are ideal targets for the therapeutic intervention of both stages of platelet-assisted metastasis.

Heme oxygenase-1 deficiency alters erythroblastic island formation, steady-state erythropoiesis and red blood cell lifespan in mice

Heme oxygenase-1 is critical for iron recycling during red blood cell turnover, whereas its impact on steady-state erythropoiesis and red blood cell lifespan is not known. We show here that in 8- to 14-week old mice, heme oxygenase-1 deficiency adversely affects steady-state erythropoiesis in the bone marrow. This is manifested by a decrease in Ter-119(+)-erythroid cells, abnormal adhesion molecule expression on macrophages and erythroid cells, and a greatly diminished ability to form erythroblastic islands. Compared with wild-type animals, red blood cell size and hemoglobin content are decreased, while the number of circulating red blood cells is increased in heme oxygenase-1 deficient mice, overall leading to microcytic anemia. Heme oxygenase-1 deficiency increases oxidative stress in circulating red blood cells and greatly decreases the frequency of macrophages expressing the phosphatidylserine receptor Tim4 in bone marrow, spleen and liver. Heme oxygenase-1 deficiency increases spleen weight and Ter119(+)-erythroid cells in the spleen, although α4β1-integrin expression by these cells and splenic macrophages positive for vascular cell adhesion molecule 1 are both decreased. Red blood cell lifespan is prolonged in heme oxygenase-1 deficient mice compared with wild-type mice. Our findings suggest that while macrophages and relevant receptors required for red blood cell formation and removal are substantially depleted in heme oxygenase-1 deficient mice, the extent of anemia in these mice may be ameliorated by the prolonged lifespan of their oxidatively stressed erythrocytes.

Mice deficient in the putative phospholipid flippase ATP11C exhibit altered erythrocyte shape, anemia, and reduced erythrocyte life span

Transmembrane lipid transporters are believed to establish and maintain phospholipid asymmetry in biological membranes; however, little is known about the in vivo function of the specific transporters involved. Here, we report that developing erythrocytes from mice lacking the putative phosphatidylserine flippase ATP11C showed a lower rate of PS translocation in vitro compared with erythrocytes from wild-type littermates. Furthermore, the mutant mice had an elevated percentage of phosphatidylserine-exposing mature erythrocytes in the periphery. Although erythrocyte development in ATP11C-deficient mice was normal, the mature erythrocytes had an abnormal shape (stomatocytosis), and the life span of mature erythrocytes was shortened relative to that in control littermates, resulting in anemia in the mutant mice. Thus, our findings uncover an essential role for ATP11C in erythrocyte morphology and survival and provide a new candidate for the rare inherited blood disorder stomatocytosis with uncompensated anemia.

Platelets, selectins, and the control of tumor metastasis

The significant role of platelets and P-selectin in assisting tumor cell metastasis to the lungs has been frequently reported and reviewed. However, evidence recently has come to light on other pro-metastatic mechanisms of platelets beyond that of tumor cell protection from immune cell attack and aiding extravasation, such as promoting epithelial to mesenchymal transition in tumor cells and conveying signals from the primary tumor to distant tissues that optimize conditions for metastasis. Moreover, the role of platelets and selectins in hematogenous metastasis to frequently targeted organs other than the lungs has been less well examined. This review aims to summarize the literature on the roles of platelets in all stages of the metastatic process and to examine the participation of platelets and selectins in hematogenous metastasis to the lungs, liver, bone, and brain. In the light of the available evidence, potential therapeutic avenues for the control of metastasis are also discussed.

Platelets and P-selectin control tumor cell metastasis in an organ-specific manner and independently of NK cells

The prometastatic role of platelets has long been recognized with proposed mechanisms of action including shielding tumor cells from natural killer (NK) cell destruction and aiding endothelial attachment and extravasation of tumor cells with platelet P-selectin being implicated in these processes. However, many aspects of the prometastatic function of platelets remain unclear. In this study, we used mouse models of metastatic breast cancer and melanoma to investigate the platelet effect, focusing on organ specificity, the relationship with NK cells and the relative importance of platelet-derived versus endothelial-derived P-selectin. We found that platelets promote lung metastasis in the absence of NK cells in both acute and spontaneous metastasis models. In addition, the prometastatic action of platelets was found to be organ specific, clearly enhancing lung metastasis but not affecting B16F1 liver metastasis, in fact, liver metastasis was enhanced in the absence of platelets. Furthermore, the profound antimetastatic activity of NK cells was equally effective in the presence or absence of platelets and chronologically distinct from the prometastatic role of platelets. Finally, it was shown that endothelial-derived P-selectin is just as important as platelet-derived P-selectin in promoting lung metastasis and also plays an important role in liver metastasis. Taken together, our findings help clarify the roles of platelets, NK cells and P-selectin in metastasis, and they identify P-selectin as an attractive therapeutic target for preventing metastasis in multiple organs.

A variant chronic B-cell lymphoma characterized by villous cells with novel immunophenotypic and cytogenetic profiles

The less common chronic B-cell lymphomas include hairy cell leukemia, hairy cell leukemia variant and splenic lymphoma with villous lymphocytes. These disease entities can sometimes cause a diagnostic dilemma; however, immunophenotypic markers have been identified as disease specific and scoring systems have been proposed to assist the process. This study reports a case of a chronic B-cell lymphoma with long cytoplasmic projections which does not fit into any of the published disease categories based upon a combination of clinical and morphological features and immunophenotyping. Furthermore, this case featured a combination of cytogenetic abnormalities not previously described in the published literature in association with a B-cell lymphoproliferative disorder.

Partial deletion of chromosome 1 in a case of acute myelocytic leukemia

Acute myelocytic leukemia (AML) is a malignant disease characterized by the proliferation of immature myelocytic precursor cells causing the disruption of normal bone marrow function. Many chromosomal aberrations have been described in AML including translocations, inversions, deletions, and additions. Here we describe a novel deletion of chromosome 1, del(1)(p34p36) in a case of AML, French-American-British classification M1, in a previously healthy 33-year-old male. This isolated cytogenetic abnormality occurred in 33% of the myeloblasts examined at diagnosis. Subsequent cytogenetic analyses conducted on marrow following induction and consolidation therapy demonstrated a normal male karyotype in all cells examined. The patient remains in clinical and hematological remission 22 months following diagnosis. The presence of 1p abnormalities in AML and other malignancies is reviewed, as are candidate tumor suppressor genes in the 1p34 approximately p36 region. The implications of chromosome 1p abnormalities on clinical outcome are also discussed.

Homologous mutations in two diverse sulphate transporters have similar effects

Mutations in the human sulphate transporter gene, DTDST, have been implicated in several diseases. Analysis of affected patients has linked disease symptoms to faulty sulphate transporter activity. We have reproduced two of these mutations in SHST1, a homologous member of the family isolated from the tropical legume, Stylosanthes hamata. Both mutations significantly reduce sulphate transport activity of SHST1. These results indicate that conserved residues between distinct members of the family may share essential roles in structure or function. The results also suggest that putative helix 9 may be important for stability and/or trafficking of SHST1 to the plasma membrane.