Acquired immune thrombotic thrombocytopenic purpura (TTP) associated with inactivated COVID-19 vaccine CoronaVac.

Corona virus disease 2019 (COVID-19) due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has affected the whole world. Acquired thrombotic thrombocytopenic purpura (TTP) has been reported after administration of mRNA- or adenoviral vector-based COVID-19 vaccines, including Ad26.COV2-S, BNT162b2, mRNA-1273, and ChAdOx1 nCov-19. However, whether inactivated vaccines, such as CoronaVac, could cause TTP and whether the symptoms in TTPs caused by inactivated vaccines are different from previously reported cases are unknown. In this study, two cases were reported. Both cases developed TTP after the second CoronaVac vaccination shot, but not the first. They demonstrated symptoms of fever, neurological abnormalities, renal dysfunction, thrombocytopenia, and hemolysis. Both patients achieved complete remission through several sessions of plasma exchanges and immune suppression. The incidence of TTP in Nanjing area was analyzed. The number of patients with TTP was 12 in 2019, 6 in 2020, 16 in 2021, and 19 in 2022. To the authors' knowledge, this report is the first report of TTP associated with inactivated COVID-19 vaccine (CoronaVac). The rarity and delayed onset may be due to the relatively milder immune response caused by the inactivated vaccines than mRNA-based ones. Timely plasma exchange is a vital treatment for CoronaVac-related TTP, similar to activated vaccine-related TTP.

Thrombotic events associated with immune checkpoint inhibitors and novel antithrombotic strategies to mitigate bleeding risk.

Although immunotherapy is expanding treatment options for cancer patients, the prognosis of advanced cancer remains poor, and these patients must contend with both cancers and cancer-related thrombotic events. In particular, immune checkpoint inhibitors are associated with an increased risk of atherosclerotic thrombotic events. Given the fundamental role of platelets in atherothrombosis, co-administration of antiplatelet agents is always indicated. Platelets are also involved in all steps of cancer progression. Classical antithrombotic drugs can cause inevitable hemorrhagic side effects due to blocking integrin ß3 bidirectional signaling, which regulates simultaneously thrombosis and hemostasis. Meanwhile, many promising new targets are emerging with minimal bleeding risk and desirable anti-tumor effects. This review will focus on the issue of thrombosis during immune checkpoint inhibitor treatment and the role of platelet activation in cancer progression as well as explore the mechanisms by which novel antiplatelet therapies may exert both antithrombotic and antitumor effects without excessive bleeding risk.

Arsenic Inhibits Proliferation and Induces Autophagy of Tumor Cells in Pleural Effusion of Patients with Non-Small Cell Lung Cancer Expressing EGFR with or without Mutations via PI3K/AKT/mTOR Pathway.

To clarify whether arsenic could exert inhibitory effects on tumor cells in pleural effusions of patients with non-small cell lung cancer (NSCLC), 36 NSCLC pleural effusion samples were collected from Changzheng Hospital and Ruijin Hospital, from 2019 to 2022. The genotype of epidermal growth factor receptor (EGFR) was identified. Tumor cells were isolated and treated with arsenic trioxide (ATO) or/and gefitinib. Additionally, six patients were intrapleurally administrated with ATO. Results showed that 25 samples bore EGFR wild type (WT) and 11 harbored EGFR mutations, including 6 with L858R, 3 with ΔE746-A750, and 2 with T790M. ATO diminished the number of tumor cells from patients with WT and mutant EGFR, down-regulated the expression or phosphorylation of EGFR, pmTOR, PI3K, PTEN, and p4E-BP1, and up-regulated the expression of LC3. Immunofluorescent experiments showed that ATO enhanced LC3 and P62. By contrast, gefitinib was only effective in those harboring EGFR sensitizing mutations. Notably, in patients with intrapleural ATO injection, the pleural effusion underwent a bloody to pale yellow color change, the volume of the pleural effusion was reduced, and the number of the tumor cells was significantly reduced. In conclusion, arsenic is effective against NSCLC with various EGFR genotypes in vitro and in vivo, and potentially circumvents gefitinib resistance.

Structure, signal transduction, activation, and inhibition of integrin αIIbß3.

Integrins are heterodimeric receptors comprising α and ß subunits. They are expressed on the cell surface and play key roles in cell adhesion, migration, and growth. Several types of integrins are expressed on the platelets, including αvß3, αIIbß3, α2ß1, α5ß1, and α6ß1. Among these, physically αIIbß3 is exclusively expressed on the platelet surface and their precursor cells, megakaryocytes. αIIbß3 adopts at least three conformations: i) bent-closed, ii) extended-closed, and iii) extended-open. The transition from conformation i) to iii) occurs when αIIbß3 is activated by stimulants. Conformation iii) possesses a high ligand affinity, which triggers integrin clustering and platelet aggregation. Platelets are indispensable for maintaining vascular system integrity and preventing bleeding. However, excessive platelet activation can result in myocardial infarction (MI) and stroke. Therefore, finding a novel strategy to stop bleeding without accelerating the risk of thrombosis is important. Regulation of αIIbß3 activation is vital for this strategy. There are a large number of molecules that facilitate or inhibit αIIbß3 activation. The interference of these molecules can accurately control the balance between hemostasis and thrombosis. This review describes the structure and signal transduction of αIIbß3, summarizes the molecules that directly or indirectly affect integrin αIIbß3 activation, and discusses some novel antiαIIbß3 drugs. This will advance our understanding of the activation of αIIbß3 and its essential role in platelet function and tumor development.

[Promoting Effect of Rat FVIII Light Chain Delivered by Adeno-Associated Virus Vector Serotype 8 on the Activity of Human FVIII Heavy Chain with Different Length].

OBJECTIVE: To explore the effects of the rat FVIII light chain (rLC) on the activity of human FVIII heavy chain hHC745 and hHC1690. METHODS: hHC745, hHC1690, human FVIII light chain (hLC) and rLC were cloned into adeno-associated virus serotype 8 (AAV8) expression vectors with CB promoter (ubiquitous expression), respectively, and transfected into 293T cells using a dual-chain strategy of co-expression of HC and LC. The cultured cell supernatant was collected at 48 hours after transfection. The plasmids (pAAV8-CB-hHC745, pAAV8-CB-hHC1690, pAAV8-CB-hLC and pAAV8-CB-rLC) were hydrodynamically injected into hemophilia A (HA) mice via lateral tail vein. Forty-eight hours after injection, the peripheral blood of the mice was collected through retroorbital venous plexus and the plasma was obtained by centrifugation. The activity of FVIII was detected by activated partial thromboplastin time (aPTT) assay, and the antigen expression level of FVIII was determined by enzyme-linked immunosorbent assay (ELISA). The specific activity of FVIII was calculated based on the activity and the antigen expression level. RESULTS: In 293T cells, the coagulation activity of FVIII was significantly enhanced when hHC745 and hHC1690 combined with rLC compared with them combined with hLC. The FVIII activity of hHC745+rLC was about 4.6 times higher than that of hHC745+hLC, while hHC1690+rLC was about 2.9 times higher than that of hHC1690+hLC. The data from ELISA showed that there was no significant difference in FVIII antigen expression when hHC745 and hHC1690 combined with rLC and hLC. The specific activity of hHC745+rLC increased to about 4.1 times compared with hHC745+hLC, while that of hHC1690+rLC increased to about 2.8 times compared with hHC1690+hLC. In HA mice administrated with hydrodynamic injection, the FVIII activity of hHC745+rLC and hHC1960+rLC was significantly higher than that of hHC745+hLC and hHC1690+hLC at comparable expression level. The FVIII activity of hHC745+rLC was significantly higher than that of hHC745+hLC, increasing to about 5.1 times, while, that of hHC1690+rLC increasing to about 2.1 times than hHC1690+hLC. ELISA results also showed that there was no significant difference in FVIII antigen expression when hHC745 and hHC1690 combined with rLC and hLC. The specific activity of hHC745+rLC increased to about 4.2 times compared with hHC745+hLC, while that of hHC1690+rLC increased to about 1.8 times compared with hHC1690+hLC. In addition, the activity of hHC1690 combined with rLC was significantly higher than that of hHC745 combined with rLC. CONCLUSION: rLC can significantly enhance the coagulation activity of FVIII when co-expressed with hHC of different length including hHC745 and hHC1690.

Chemically modified in-vitro-transcribed mRNA encoding thrombopoietin stimulates thrombopoiesis in mice.

The use of messenger RNA (mRNA) enables the transient production of therapeutic proteins with stable and predictable translational kinetics and without the risk of insertional mutagenesis. Recent findings highlight the enormous potential of mRNA-based therapeutics. Here, we describe the synthesis of chemically modified thrombopoietin (TPO) mRNA through in vitro transcription and in vivo delivery via lipid nanoparticles (LNPs). After delivery of TPO mRNA in mice, compared with normal physiological values, plasma TPO protein levels increased over 1000-fold in a dose-dependent manner. Moreover, through a single intravenous dose of TPO mRNA-loaded LNPs, both reticulated and total platelet count increased significantly in mice, demonstrating that TPO protein derived from the exogenous mRNA was able to maintain normal activity. Submicrogram quantity of N1-methylpseudouridine-modified TPO mRNA showed a similar effect in promoting thrombopoiesis as that by the TPO receptor agonist romiplostim. In addition, a therapeutic value was established in anti-GPIbα (CD42b) antibody-induced thrombocytopenia mouse models that showed a fast recovery of platelet count. Our study demonstrated chemically modified in-vitro-transcribed TPO mRNA as a potentially safe therapeutic intervention to stimulate thrombopoiesis.

Targeting the RT loop of Src SH3 in Platelets Prevents Thrombosis without Compromising Hemostasis.

Conventional antiplatelet agents indiscriminately inhibit both thrombosis and hemostasis, and the increased bleeding risk thus hampers their use at more aggressive dosages to achieve adequate effect. Blocking integrin αIIbß3 outside-in signaling by separating the ß3/Src interaction, yet to be proven in vivo, may nonetheless resolve this dilemma. Identification of a specific druggable target for this strategy remains a fundamental challenge as Src SH3 is known to be responsible for binding to not only integrin ß3 but also the proteins containing the PXXP motif. In vitro and in vivo mutational analyses show that the residues, especially E97, in the RT loop of Src SH3 are critical for interacting with ß3. DCDBS84, a small molecule resulting from structure-based virtual screening, is structurally validated to be directed toward the projected target. It specifically disrupts ß3/Src interaction without affecting canonical PXXP binding and thus inhibits the outside-in signaling-regulated platelet functions. Treatment of mice with DCDBS84 causes a profound inhibition of thrombosis, equivalent to that induced by extremely high doses of αIIbß3 antagonist, but does not compromise primary hemostasis. Specific targets are revealed for a preferential inhibition of thrombosis that may lead to new classes of potent antithrombotics without hemorrhagic side effects.

Long-term correction of hemorrhagic diathesis in hemophilia A mice by an AAV-delivered hybrid FVIII composed of the human heavy chain and the rat light chain.

Conventional therapies for hemophilia A (HA) are prophylactic or on-demand intravenous FVIII infusions. However, they are expensive and inconvenient to perform. Thus, better strategies for HA treatment must be developed. In this study, a recombinant FVIII cDNA encoding a human/rat hybrid FVIII with an enhanced procoagulant potential for adeno-associated virus (AAV)-delivered gene therapy was developed. Plasmids containing human FVIII heavy chain (hHC), human light chain (hLC), and rat light chain (rLC) were transfected into cells and hydrodynamically injected into HA mice. Purified AAV viruses were intravenously injected into HA mice at two doses. Results showed that the hHC + rLC protein had a higher activity than the hHC + hLC protein at comparable expression levels. The specific activity of hHC + rLC was about 4- to 8-fold higher than that of their counterparts. Hydrodynamic injection experiments obtained consistent results. Notably, the HA mice undergoing the AAV-delivered hHC + rLC treatment exhibited a visibly higher activity than those treated with hHC + hLC, and the therapeutic effects lasted for up to 40 weeks. In conclusion, the application of the hybrid FVIII (hHC + rLC) via an AAV-delivered gene therapy substantially improved the hemorrhagic diathesis of the HA mice. These data might be of help to the development of optimized FVIII expression cassette for HA gene therapy.

Characteristics of the Thrombus Formation in Transgenic Mice with Platelet-Targeted Factor VIII Expression.

Platelet-targeted FVIII gene therapy can efficiently recover bleeding phenotype for hemophilia A (HA), yet characteristics of thrombus formation with this ectopic expression of factor VIII (FVIII) in platelets remain unclear. Here, we generated 2bF8trans mice restrictively expressing human B-domain-deleted FVIII (hBDD FVIII) in platelets on a hemophilic (FVIIInull) mice background. The results showed no statistical difference in clot strength and stability between wild-type (WT) and 2bF8trans mice, but with a prolonged reaction time (R-time), by thromboelastography. Fluid dynamics analysis showed that at the shear rates of 500 to 1,500 s-1, where physiological hemostasis often develops, the thrombi formed in 2bF8trans mice were more stable than those in FVIIInull mice, while at high pathological shear rates (2,500 s-1), mimicking atherosclerosis, thrombus size and fibrin deposition in 2bF8trans mice were less than those in WT mice. Thrombus morphology analysis showed that there was a locally concentrated deposition of fibrin in thrombus at the injured site and fibrin co-localized with activated platelets in 2bF8trans mice. Moreover, a higher ratio of fibrin to platelets was found in thrombus from 2bF8trans mice following laser-induced injury in cremaster arterioles, which might be the underlying mechanism of thrombus stability in 2bF8trans mice at physiological arterial circumstance. These observations suggest that specific morphological features of the thrombi might contribute to the efficacy and safety of platelet-targeted FVIII gene therapy for HA.

Inherent hepatocytic heterogeneity determines expression and retention of edited F9 alleles post-AAV/CRISPR infusion.

Infusing CRISPR/donor-loaded adeno-associated viral vectors (AAV/CRISPR) could enable in vivo hepatic gene editing to remedy hemophilia B (HB) with inherited deficiency of clotting factor IX (FIX). Yet, current regimens focus on correcting HB with simple mutations in the coding region of the F9, overlooking those carrying complicated mutations involving the regulatory region. Moreover, a possible adverse effect of treatment-related inflammation remains unaddressed. Here we report that a single DNA cutting-mediated long-range replacement restored the FIX-encoding function of a mutant F9 (mF9) carrying both regulatory and coding defects in a severe mouse HB model, wherein incorporation of a synthetic Alb enhancer/promoter-mimic (P2) ensured FIX elevation to clinically meaningful levels. Through single-cell RNA sequencing (scRNA-seq) of liver tissues, we revealed that a subclinical hepatic inflammation post-AAV/CRISPR administration regulated the vulnerability of the edited mF9-harboring host cells to cytotoxic T lymphocytes (CTLs) and the P2 activity in a hepatocytic subset-dependent manner via modulating specific sets of liver-enriched transcription factors (LETFs). Collectively, our study establishes an AAV/CRISPR-mediated gene-editing protocol applicable to complicated monogenetic disorders, underscoring the potentiality of improving therapeutic benefits through managing inflammation.

Activated factor X targeted stored in platelets as an effective gene therapy strategy for both hemophilia A and B.

BACKGROUND: Treatment of hemophiliacs with inhibitors remains challenging, and new treatments are in urgent need. Coagulation factor X plays a critical role in the downstream of blood coagulation cascade, which could serve as a bypassing agent for hemophilia therapy. Base on platelet-targeted gene therapy for hemophilia by our and other groups, we hypothesized that activated factor X (FXa) targeted stored in platelets might be effective in treating hemophilia A (HA) and B (HB) with or without inhibitors. METHODS: To achieve the storage of FXa in platelets, we constructed a FXa precursor and used the integrin αIIb promoter to control the targeted expression of FXa precursor in platelets. The expression cassette (2bFXa) was carried by lentivirus and introduced into mouse hematopoietic stem and progenitor cells (HSPCs), which were then transplanted into HA and HB mice. FXa expression and storage in platelets was examined in vitro and in vivo. We evaluated the therapeutic efficacy of platelet-stored FXa by tail bleeding assays and the thrombelastography. In addition, thrombotic risk was assessed in the recipient mice and the lipopolysaccharide induced inflammation mice. RESULTS: By transplanting 2bFXa lentivirus-transduced HSPCs into HA and HB mice, FXa was observed stably stored in platelet α-granules, the stored FXa is releasable and functional upon platelet activation. The platelet-stored FXa can significantly ameliorate bleeding phenotype in HA and HB mice as well as the mice with inhibitors. Meanwhile, no FXa leakage in plasma and no signs of increased risk of hypercoagulability were found in transplantation recipients and lipopolysaccharide induced septicemia recipients. CONCLUSIONS: Our proof-of-principle data indicated that target expression of the FXa precursor to platelets can generate a storage pool of FXa in platelet α-granules, the platelet-stored FXa is effective in treating HA and HB with inhibitors, suggesting that this could be a novel choice for hemophilia patients with inhibitors.

Synchronous diagnosis of anaplastic large cell lymphoma and multiple myeloma in a patient: A case report.

RATIONALE: Synchronous development of both anaplastic large cell lymphoma (ALCL) and multiple myeloma (MM) in a patient is rare. To our knowledge, until now only one case has been reported. Treatment needs to cover both and is a challenge. Here we reported another case and discussed the diagnosis and treatment. PATIENT CONCERNS: This is a 63-year old woman who presented with a mass in upper abdominal skin. Positron emission tomography/computed tomography (PET/CT) showed the high metabolism in left abdominal skin and left axillary lymph nodes. Histopathologic and immunohistochemical evaluation identified the cutaneous mass as an ALK-negative ALCL. Bone marrow smear showed increased plasma cells which expressed CD38, CD138, and cLambda concomitantly. The increased monoclonal immunoglobulin IgD λ was detected by immunofixation electrophoresis. DIAGNOSES: Diagnosis of both ALCL and MM was confirmed. INTERVENTIONS: The patient successively received 6 cycles of B-CHOD regimen, one cycle of ID regimen, 2 cycles of DHAX regimen, one cycle of L-DA-EPOCH and autologous stem cell transplantation (ASCT). Then lenalidomide was performed as a maintenance therapy. OUTCOMES: Both ALCL and MM achieved complete remission. LESSONS: We reported a very rare case with synchronous development of ALCL and MM, in whom a good therapeutic response to chemotherapies followed by ASCT has been observed.

Establishment and characterization of a novel 'double-hit' follicular lymphoma cell line, FL-SJC.

About 5 per cent of follicular lymphoma (FL) cases are double-hit (DH) lymphomas. Double-hit follicular lymphoma (DHFL) cell lines can improve our understanding and drug development on FL. But there are only few DHFL cell lines. Here, we established a new MYC/BCL2 DHFL cell line, FL-SJC. The cells were obtained from the hydrothorax of a patient with MYC/BCL2 DHFL and cultured for 140 passages in vitro. FL-SJC cells demonstrated CD19++ , CD20+ , CD22++ , HLA-DR+ , CD10+ , CD38+ , Lambda+ CD23- , CD5- and Kappa- . The chromosome karyotypic analysis confirmed the co-existence of t(8;22)(q24;q11) and t(14;18)(q32;q21), as well as additional abnormalities involving chromosomes 2 and 3. Fluorescence in situ hybridization analysis (FISH) showed IGH/BCL2 fusion gene and the MYC rearrangement. In addition, the FL-SJC cells displayed KMT2D/MLL2 and CREBBP gene mutations. After subcutaneous inoculation of FL-SJC cells, the SCID mice developed solid tumour masses within 6-8 weeks. FL-SJC cells were proven to be free of Epstein-Barr (EB) virus infection and be multidrug-resistant. In a conclusion, the FL-SJC cell line has been identified as a novel MYC/BCL2 double-hit follicular lymphoma that can be used as a potentially available tool for the clinical and basic research, together with the drug development for MYC/BCL2 DHFL.

Integrin ß3 Deficiency Results in Hypertriglyceridemia via Disrupting LPL (Lipoprotein Lipase) Secretion.

OBJECTIVE: Integrin ß3 is implicated in numerous biological processes such as its relevance to blood triglyceride, yet whether ß3 deficiency affects this metabolic process remains unknown. Approach and Results: We showed that the Chinese patients with ß3-deficient Glanzmann thrombasthenia had a 2-fold higher serum triglyceride level together with a lower serum LPL (lipoprotein lipase) level than those with an αIIb deficiency or healthy subjects. The ß3 knockout mice recapitulated these phenotypic features. The elevated plasma triglyceride level was due to impaired LPL-mediated triglyceride clearance caused by a disrupted LPL secretion. Further analysis revealed that ß3 directly bound LPL via a juxtamembrane TIH (threonine isoleucine histidine)720-722 motif in its cytoplasmic domain and functioned as an adaptor protein by interacting with LPL and PKD (protein kinase D) to form the PKD/ß3/LPL complex that is required for ß3-mediated LPL secretion. Furthermore, the impaired triglyceride clearance in ß3 knockout mice could be corrected by adeno-associated virus serotype 9 (AAV9)-mediated delivery of wild-type but not TIH720-722-mutated ß3 genes. CONCLUSIONS: This study reveals a hypertriglyceridemia in both ß3-deficient Chinese patients and mice and provides novel insights into the molecular mechanisms of the significant roles of ß3 in LPL secretion and triglyceride metabolism, drawing attention to the metabolic consequences in patients with ß3-deficient Glanzmann thrombasthenia.

Lymphadenopathy in POEMS syndrome: a correlation between clinical features and imaging findings.

Lymphadenopathy is an important characteristic of POEMS syndrome, and a Castleman disease (CD)-like pathologic change in the lymph nodes is one of the major diagnostic criteria. However, the characteristics of lymphadenopathy in POEMS still have not been completely elucidated. The lymph node biopsies are available only for a small proportion of patients. A simple and safe way is needed to rule CD in or out. This study aimed to analyse the features of lymphadenopathy and estimate the role of imaging methods, including computed tomography (CT) and positron emission tomography-CT (PET/CT), in the diagnosis of lymphadenopathy in patients with POEMS syndrome. We conducted a retrospective analysis of 23 patients with confirmed POEMS syndrome. All of the patients received chest and abdominal CT scan and/or superficial ultrasound examinations. Four patients underwent PET/CT examinations, and 6 patients received lymph node biopsies. Enlarged lymph nodes (short diameter ≥ 1 cm) were found in 48% (11/23) of patients, but only 1 patient had an enlarged lymph node with a diameter ≥ 2 cm. Lymph nodes with CD-like pathologic changes from 2 patients showed increased maximum standard uptake values (SUVmax) of 18F-deoxyglucose (18FDG) on PET/CT, while lymph nodes with reactive pathologic changes from 2 other patients showed a normal metabolic PET/CT profile. The extent of lymph node enlargement in patients with POEMS was less than that in patients with CD per se. We draw the conclusion that most of the enlarged lymph nodes had diameters ≤ 2 cm, which is less than that in cases of CD per se and PET/CT may be helpful in determining whether enlarged lymph nodes are characterized by CD-like changes or not.

Platelet integrin αIIbß3: signal transduction, regulation, and its therapeutic targeting.

Integrins are a family of transmembrane glycoprotein signaling receptors that can transmit bioinformation bidirectionally across the plasma membrane. Integrin αIIbß3 is expressed at a high level in platelets and their progenitors, where it plays a central role in platelet functions, hemostasis, and arterial thrombosis. Integrin αIIbß3 also participates in cancer progression, such as tumor cell proliferation and metastasis. In resting platelets, integrin αIIbß3 adopts an inactive conformation. Upon agonist stimulation, the transduction of inside-out signals leads integrin αIIbß3 to switch from a low- to high-affinity state for fibrinogen and other ligands. Ligand binding causes integrin clustering and subsequently promotes outside-in signaling, which initiates and amplifies a range of cellular events to drive essential platelet functions such as spreading, aggregation, clot retraction, and thrombus consolidation. Regulation of the bidirectional signaling of integrin αIIbß3 requires the involvement of numerous interacting proteins, which associate with the cytoplasmic tails of αIIbß3 in particular. Integrin αIIbß3 and its signaling pathways are considered promising targets for antithrombotic therapy. This review describes the bidirectional signal transduction of integrin αIIbß3 in platelets, as well as the proteins responsible for its regulation and therapeutic agents that target integrin αIIbß3 and its signaling pathways.

[Effect of Amino Acid Motifs in Integrin ß3 Cytoplasmic Tail on αâ ¡bß3-Mediated Cell function in 293T cell models].

OBJECTIVE: To establish 293T cell lines stably expressing Calpain-cleavage related α3 cytoplasmic tail mutants, and to explore the effect of amino acid motifs in integrin ß3 cytoplasmic tail on αⅡbß3-mediated cell function. METHODS: 293T cell lines stably co-expressing human wild type integrin αⅡb and full length ß3 or mutant ß3, including ß3-ΔNITY (ß3 cytoplasmic tail NITY motif deleted), ß3-Δ754 (ß3 cytoplasmic tail TNITYRGT motif deleted) and ß3-Δ759 (ß3 cytoplasmic tail RGT motif deleted) were established. Spreading and adhesion of these stable cell lines on immobilized fibrinogen were tested. RESULTS: 293T-αⅡbß3ΔNITY, 293T-αⅡbß3Δ754, 293T-αⅡbß3Δ759 and 293T-αⅡbß3 cell lines were successfully established. Compared with the 293T cells, 293T-αⅡbß3 cells which expressed full ß3, possessed well adhesion and spread ability on immobilized fibrinogen, suggesting it can be as a surrogate for platelet. Compared with 293T-αⅡbß3 cells, the 293T-αⅡbß3ΔNITY cells showed a partial impairment of adhesion and spreadability on immobilized fibrinogen. while the 293T-αⅡbß3Δ754 cells and 293T-αⅡbß3Δ759 cells failed to adhere or spread on immobilized fibrinogen. CONCLUSION: To the cell spreading function mediated by integrin ß3, RGT motif is vital, while NITY can be dispensable. These established 293T cell lines stably expressing different ß3 mutants provide a solid basis for a further analysis of mass spectrometry.

Homoharringtonine deregulates MYC transcriptional expression by directly binding NF-κB repressing factor.

Homoharringtonine (HHT), a known protein synthesis inhibitor, has an anti-myeloid leukemia effect and potentiates the therapeutic efficacy of anthracycline/cytarabine induction regimens for acute myelogenous leukemia (AML) with favorable and intermediate prognoses, especially in the t(8;21) subtype. Here we provide evidence showing that HHT inhibits the activity of leukemia-initiating cells (Lin-/Sca-1-/c-kit+; LICs) in a t(8;21) murine leukemia model and exerts a down-regulating effect on MYC pathway genes in human t(8;21) leukemia cells (Kasumi-1). We discovered that NF-κB repressing factor (NKRF) is bound directly by HHT via the second double-strand RNA-binding motif (DSRM2) domain, which is the nuclear localization signal of NKRF. A series of deletion and mutagenesis experiments mapped HHT direct binding sites to K479 and C480 amino acids in the DSRM2 domain. HHT treatment shifts NKRF from the nucleus (including nucleoli) to the cytoplasm by occupying the DSRM2 domain, strengthens the p65-NKRF interaction, and interferes with p65-p50 complex formation, thereby attenuating the transactivation activity of p65 on the MYC gene. Moreover, HHT significantly decreases the expression of KIT, a frequently mutated and/or highly expressed gene in t(8;21) AML, in concert with MYC down-regulation. Our work thus identifies a mechanism of action of HHT that is different from, but acts in concert with, the known mode of action of this compound. These results justify further clinical testing of HHT in AML.