Dextran sulphate induces fibrinogen receptor activation through a novel Syk-independent PI-3 kinase-mediated tyrosine kinase pathway in platelets

2013 ◽  
Vol 109 (06) ◽  
pp. 1131-1140 ◽  
Author(s):  
Todd M. Getz ◽  
Bhanu Manne ◽  
Lorena Buitrago ◽  
Yingying Mao ◽  
Satya P. Kunapuli
Keyword(s):  
Platelet Aggregation ◽  
Tyrosine Kinase ◽  
Kinase Inhibitor ◽  
Receptor Activation ◽  
Dependent Manner ◽  
Akt Phosphorylation ◽  
Glycoprotein Vi ◽  
Fibrinogen Receptor ◽  
Adp Receptor Antagonists ◽  
Kinase Pathway

SummaryIn our attempt to find a physiological agonist that activates PAR3 receptors, we screened several coagulation proteases using PAR4 null platelets. We observed that FXIIa and heat inactivated FXIIa, but not FXII, caused platelet aggregation. We have identified a contaminant activating factor in FXIIa preparation as dextran sulfate (DxS), which caused aggregation of both human and mouse platelets. DxS-induced platelet aggregation was unaffected by YM254890, a Gq inhibitor, but abolished by pan-Src family kinase (SFK) inhibitor PP2, suggesting a role for SFKs in this pathway. However, DxS-induced platelet aggregation was unaffected in FcRγ-chain null murine platelets, ruling out the possibility of glycoprotein VI-mediated events. More interesting, OXSI-2 and Go6976, two structurally unrelated inhibitors shown to affect Syk, had only a partial effect on DxS-induced PAC-1 binding. DxS-induced platelet aggregation and intracellular calcium increases were abolished by the pan PI-3 kinase inhibitor LY294002, or an isoform-specific PI-3 kinase β inhibitor TGX-221. Pretreatment of platelets with Syk inhibitors or ADP receptor antagonists had little effect on Akt phosphorylation following DxS stimulation. These results, for the first time, establish a novel tyrosine kinase pathway in platelets that causes fibrinogen receptor activation in a PI-3 kinase-dependent manner without a crucial role for Syk.

TGF-β1-induced EMT can occur independently of its proapoptotic effects and is aided by EGF receptor activation

2006 ◽  
Vol 290 (5) ◽  
pp. F1202-F1212 ◽  
Author(s):  
Neil G. Docherty ◽  
Orfhlaith E. O'Sullivan ◽  
Declan A. Healy ◽  
Madeline Murphy ◽  
Amanda J. O'Neill ◽  
...  
Keyword(s):  
Growth Factor ◽  
Western Blotting ◽  
Egf Receptor ◽  
Transforming Growth Factor ◽  
Kinase Inhibitor ◽  
Receptor Activation ◽  
Concomitant Treatment ◽  
Dependent Manner ◽  
Akt Phosphorylation

Apoptosis and epithelial-mesenchymal transdifferentiation (EMT) occur in stressed tubular epithelial cells and contribute to renal fibrosis. Transforming growth factor (TGF)-β1 promotes these responses and we examined whether the processes were interdependent in vitro. Direct (caspase inhibition) and indirect [epidermal growth factor (EGF) receptor stimulation] strategies were used to block apoptosis during TGF-β1 stimulation, and the subsequent effect on EMT was assessed. HK-2 cells were exposed to TGF-β1 with or without preincubation with ZVAD-FMK (pan-caspase inhibitor) or concomitant treatment with EGF plus or minus preincubation with LY-294002 (PI3-kinase inhibitor). Cells were then assessed for apoptosis and proliferation by flow cytometry, crystal violet assay, and Western blotting. Markers of EMT were assessed by microscopy, immunofluorescence, real-time RT-PCR, Western blotting, PAI-1 reporter assay, and collagen gel contraction assay. TGF-β1 caused apoptosis and priming for staurosporine-induced apoptosis. This was blocked by ZVAD-FMK. However, ZVAD-FMK did not prevent EMT following TGF-β1 treatment. EGF inhibited apoptosis and facilitated TGF-β1 induction of EMT by increasing proliferation and accentuating E-cadherin loss. Additionally, EGF significantly enhanced TGF-β1-induced collagen I gel contraction. EGF increased Akt phosphorylation during EMT, and the prosurvival effect of this was confirmed using LY-294002, which reduced EGF-induced Akt phosphorylation and reversed its antiapoptotic and proproliferatory effects. TGF-β1 induces EMT independently of its proapoptotic effects. TGF-β1 and EGF together lead to EMT. EGF increases proliferation and resistance to apoptosis during EMT in a PI3-K Akt-dependent manner. In vivo, EGF receptor activation may assist in the selective survival of a transdifferentiated, profibrotic cell type.

scholarly journals Src family kinase–mediated and Erk-mediated thromboxane A2 generation are essential for VWF/GPIb-induced fibrinogen receptor activation in human platelets

Blood ◽  
2005 ◽  
Vol 106 (10) ◽  
pp. 3410-3414 ◽  
Author(s):  
Analia Garcia ◽  
Todd M. Quinton ◽  
Robert T. Dorsam ◽  
Satya P. Kunapuli
Keyword(s):  
Platelet Aggregation ◽  
Phospholipase C ◽  
Platelet Activation ◽  
Kinase Inhibitor ◽  
Thromboxane A2 ◽  
Receptor Activation ◽  
Src Family Kinases ◽  
Mitogen Activated Protein Kinase ◽  
Dependent Manner ◽  
Src Family Kinase

AbstractThe binding of von Willebrand factor (VWF) to the platelet membrane glycoprotein Ib-IX (GPIb-IX) results in platelet activation. In this study, we sought to clarify previous conflicting reports and to elucidate the mechanism of activation and the precise role of extracellular signal-regulated kinase (Erk) in VWF-induced platelet activation. Erk2 is activated in platelets on stimulation with VWF/ristocetin in a time-dependent manner. VWF-induced Erk2 phosphorylation and thromboxane A2 (TXA2) release were completely blocked by PP2, an Src family kinase inhibitor, suggesting that Erk is downstream of Src family kinases. U73122, a phospholipase C inhibitor, also abolished TXA2 generation and Erk phosphorylation. Although VWF fostered the agglutination of platelets regardless of any additional treatment, the inhibition of mitogen-activated protein kinase kinase (MEK) with U0126 abolished VWF-induced platelet aggregation and thromboxane production in non–aspirin-treated washed platelets. However, in platelets treated with aspirin, VWF failed to cause any aggregation. Thus, we conclude that VWF stimulation of platelets results in phospholipase A2 activation through Erk stimulation and that Src family kinases and phospholipase C play essential roles in this event. We further conclude that VWF-induced platelet aggregation does not directly depend on Erk activation but has an absolute requirement for Src/Erk-mediated TXA2 generation.

Glycoprotein VI–mediated platelet fibrinogen receptor activation occurs through calcium-sensitive and PKC-sensitive pathways without a requirement for secreted ADP

Blood ◽  
2002 ◽  
Vol 99 (9) ◽  
pp. 3228-3234 ◽  
Author(s):  
Todd M. Quinton ◽  
Fatih Ozdener ◽  
Carol Dangelmaier ◽  
James L. Daniel ◽  
Satya P. Kunapuli
Keyword(s):  
Protein Kinase C ◽  
Platelet Aggregation ◽  
Protein Kinase ◽  
Response Curve ◽  
Receptor Activation ◽  
Glycoprotein Vi ◽  
Fibrinogen Receptor ◽  
Kinase C ◽  
The Right ◽  
Concentration Response Curve

Abstract Collagen activates platelets by transducing signals through glycoprotein VI (GPVI). It is not clear whether collagen can directly activate fibrinogen receptors on the adherent platelets without a role for positive feedback agonists. We investigated the contribution of secondary G protein signaling to the mechanism of GPVI-stimulated platelet aggregation using the GPVI-selective agonists, convulxin and collagen-related peptide (CRP) as well as collagen. Adenosine diphosphate (ADP) scavengers or ADP receptor antagonists shifted the concentration-response curve slightly to the right at low concentrations of convulxin, whereas platelet aggregation at higher concentrations of convulxin was unaffected by these agents. ADP receptor antagonists shifted the concentration-response curve of collagen- or CRP-induced platelet aggregation to the right at all the concentrations. Protein kinase C inhibitor, Ro 31-8220, or a calcium chelator 5,5′-dimethyl-BAPTA shifted the concentration-response curve of convulxin-induced platelet aggregation to the right. In addition, pretreatment with both Ro 31-8220 and dimethyl-BAPTA resulted in total inhibition of convulxin-mediated aggregation. Blockade of either the calcium- or protein kinase C–regulated pathway leads to inhibition of fibrinogen receptor activation on platelets adherent to collagen, but inhibition of both pathways leads to abolished fibrinogen receptor activation. We conclude that collagen-induced activation of fibrinogen receptor on adherent platelets through GPVI signaling occurs without any significant role for secreted ADP or thromboxane A2. Furthermore, protein kinase C– and calcium-regulated pathways independently contribute to GPVI-mediated platelet aggregation.

ACh and adenosine activate PI3-kinase in rabbit hearts through transactivation of receptor tyrosine kinases

2002 ◽  
Vol 283 (6) ◽  
pp. H2322-H2330 ◽  
Author(s):  
Thomas Krieg ◽  
Qining Qin ◽  
Elizabeth C. McIntosh ◽  
Michael V. Cohen ◽  
James M. Downey
Keyword(s):  
Tyrosine Kinase ◽  
Tyrosine Kinases ◽  
Receptor Tyrosine Kinases ◽  
Kinase Inhibitor ◽  
Growth Factor Receptor ◽  
Pi3 Kinase ◽  
Dependent Manner ◽  
Src Tyrosine Kinase ◽  
Akt Phosphorylation ◽  
Downstream Target

Adenosine and acetylcholine (ACh) trigger preconditioning through different signaling pathways. We tested whether either could activate myocardial phosphatidylinositol 3-kinase (PI3-kinase), a putative signaling protein in ischemic preconditioning. We used phosphorylation of Akt, a downstream target of PI3-kinase, as a reporter. Exposure of isolated rabbit hearts to ACh increased Akt phosphorylation 2.62 ± 0.33 fold ( P = 0.001), whereas adenosine caused a significantly smaller increase (1.52 ± 0.08 fold). ACh-induced activation of Akt was abolished by the tyrosine kinase blocker genistein indicating at least one tyrosine kinase between the muscarinic receptor and Akt. ACh-induced Akt activation was blocked by the Src tyrosine kinase inhibitor 4-amino-5-(4-chlorophenyl)-7-( t-butyl)pyrazolo[3,4- d]pyrimidine (PP2) and by 4-(3-chloroanilino)-6,7-dimethoxyquinazoline (AG-1478), an epidermal growth factor receptor (EGFR) inhibitor, suggesting phosphorylation of a receptor tyrosine kinase in an Src tyrosine kinase-dependent manner. ACh caused tyrosine phosphorylation of the EGFR, which could be blocked by PP2, thus supporting this receptor hypothesis. AG-1478 failed to block the cardioprotection of ACh, however, suggesting that other receptor tyrosine kinases might be involved. Therefore, Gi protein-coupled receptors can activate PI3-kinase/Akt through transactivation of receptor tyrosine kinases in an Src tyrosine kinase-dependent manner.

Abstract 384: The Prothrombotic Profile of BCR-ABL Inhibitors Ponatinib, Nilotinib and Imatinib

2014 ◽  
Vol 34 (suppl_1) ◽  
Author(s):  
Cassandra P Loren ◽  
Rachel A Rigg ◽  
Joseph E Aslan ◽  
Laura D Healy ◽  
Andras Gruber ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Tyrosine Kinase ◽  
Platelet Activation ◽  
Kinase Inhibitor ◽  
Lymphoblastic Leukemia ◽  
Philadelphia Chromosome ◽  
Myelogenous Leukemia ◽  
Dependent Manner ◽  
Thrombotic Complications ◽  
Platelet Spreading

Background: Thrombotic complications observed in patients treated with the tyrosine kinase inhibitor ponatinib resulted in the temporary suspension of the drug by the FDA in late 2013. Ponatinib is a pan-BCR-ABL inhibitor designed for treatment of chronic myelogenous leukemia and Philadelphia chromosome-positive acute lymphoblastic leukemia. Ponatinib has been shown to inhibit a subset of the class III/IV family of receptor tyrosine kinases. The pathogenic mechanism underlying the prothrombotic phenotype associated with ponatinib remains ill-defined. Hypothesis: We tested the hypothesis that BCR-ABL inhibitors regulate platelet activation, spreading, and aggregation. Methods & Results: Our results show that treatment of platelets with ponatinib (1 μM) abrogated platelet spreading on fibrinogen (50 μg/ml) or collagen (100 μg/ml). Both nilotinib and imatinib inhibited platelet spreading, although not to the same extent as ponatinib at equimolar concentrations. We next examined the effects of BCR-ABL inhibitors on platelet activation and aggregation in response to the GPVI-agonist, CRP, which mediates platelet activation in a receptor tyrosine kinase-dependent manner. Intriguingly, our results show that ponatinib abrogated platelet aggregation in response to CRP (1 μg/ml), whereas equimolar concentrations of nilotinib or imatinib had minimal effects on CRP-induced platelet aggregation. Conclusions: While tyrosine kinase inhibitors are generally associated with bleeding diathesis, thrombotic complications have been observed in patients treated with ponatinib. Our results indicate that ponatinib, nilotinib, and imatinib inhibit platelet spreading and aggregation, with ponatinib having the most significant effect, suggesting that ponatinib may act as a platelet antagonist. Our future work will be focused on identifying platelet proteins affected by the BCR-ABL inhibitors as well as the pathogenic mechanisms underlying the prothrombotic phenotype associated with ponatinib.

Tyrosine kinase inhibitors reduce bcl-2 expression and induce apoptosis in androgen-dependent cells

2000 ◽  
Vol 278 (1) ◽  
pp. C66-C72 ◽  
Author(s):  
Takashi Ohigashi ◽  
Munehisa Ueno ◽  
Shoichi Nonaka ◽  
Takashi Nakanoma ◽  
Yusuke Furukawa ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Tyrosine Kinase ◽  
Tyrosine Kinases ◽  
Kinase Inhibitors ◽  
Kinase Inhibitor ◽  
Flow Cytometric Analysis ◽  
Signal Transduction Pathway ◽  
Receptor Activation ◽  
Dependent Manner ◽  
Induced Apoptosis

The signal transduction pathway showing how androgen withdrawal induces apoptosis in androgen-dependent cells has not been clearly understood. In these studies, we focused on the behavior of tyrosine kinases in androgen-dependent cells and investigated its correlation with apoptosis and bcl-2 expression. We used SC2G, an androgen-dependent mouse mammary carcinoma cell line, which had been cloned from Shionogi Carcinoma 115 (SC115). When SC2G cells were cultured with herbimycin A (HMA), a potent tyrosine kinase inhibitor, the number of viable cells decreased significantly after 24 h. Terminal deoxyribonucleotidyltransferase-mediated dUTP-biotin nick end labeling and flow cytometric analysis of annexin V staining showed that HMA induced apoptosis of SC2G cells. The level of bcl-2 mRNA in SC2G cells was suppressed by HMA in a dose-dependent manner on RT-PCR. Preincubation with caspase inhibitors protected HMA-induced apoptosis of SC2G cells. When a human bcl-2 gene was transfected in SC2G cells and overexpressed, SC2G cells seemed to acquire tolerance for HMA. These data indicate that HMA-sensitive tyrosine kinase(s) can regulate apoptosis and inhibit bcl-2 expression in SC2G mouse androgen-dependent cells. Tyrosine kinase(s) seemed to be a member of signal transduction between androgen receptor activation and bcl-2 expression.

G12/13 Pathways Potentiate Akt Phosphorylation in Platelets Mediated by Gi/Gz Pathways in a Src Kinase-Dependent Manner.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 1570-1570
Author(s):  
Soochong Kim ◽  
Jianguo Jin ◽  
Satya P. Kunapuli
Keyword(s):  
Platelet Aggregation ◽  
Kinase Inhibitor ◽  
Partial Agonist ◽  
Src Kinase ◽  
Structural Analog ◽  
Human Platelets ◽  
Dependent Manner ◽  
Akt Phosphorylation ◽  
Low Concentrations ◽  
P2y12 Receptor Antagonist

Akt is a serine/threonine kinase that is activated by various agonists including thrombin and ADP in platelets, and activation of Akt in platelets is known to require Gi signaling pathways. Even though thrombin-induced Akt phosphorylation depends on secretion/Gi pathways, thrombin caused much stronger Akt phosphorylation than ADP and epinephrine. In this study, we investigated the contribution of G12/13 pathways to Akt phosphorylation mediated by Gi or Gz pathways. We used selective agonists to activate different G protein pathways. PAR4-activating peptide (AYPGKF) and thrombin failed to induce Akt phosphorylation in Gαq-deficient platelets, but Akt phosphorylation was restored to the levels achieved by AYPGKF and thrombin in wild-type platelets by selective supplement of either Gi or Gz signaling with 2-MeSADP and epinephrine, respectively. This phosphorylation of Akt was dramatically inhibited in the presence of PP2 (4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazole[3,4-d]pyrimidine), an inhibitor of Src family tyrosine kinase, but not by PP3, an inactive structural analog. Importantly, AYPGKF and thrombin induced the activation of Src kinase in Gαq-deficient platelets, suggesting the involvement of Src-dependent pathways in the G12/13 signaling in potentiation of Akt phosphorylation. When human platelets were stimulated with low concentrations of YFLLRNP, a PAR1-specific partial agonist, to selectively activate the G12/13 signaling cascade, Akt phosphorylation did not occur. However, combined stimulation of YFLLRNP-mediated G12/13 signaling and selective activation of Gi pathways caused the Akt phosphorylation. This Akt phosphorylation was blocked by the P2Y12 receptor antagonist AR-C69931MX, or the PI 3-kinase inhibitor LY294002. Platelet aggregation induced by co-activation of both G12/13 and Gi signaling was dramatically inhibited by ML-9 (1-(5-chloronaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine hydrochloride), an Akt selective inhibitor, suggesting an important role of Akt in platelet aggregation stimulated by combined G12/13 and Gi pathways. These data demonstrate that G12/13 signaling alone does not cause Akt phosphorylation in platelets, but G12/13 signaling has a significant role in potentiating Akt phosphorylation mediated by selective Gi or Gz signaling in human as well as mouse platelets. Finally, we conclude that Src family kinases play an important role in this Akt phosphorylation in platelets.

Identification Of a Novel Small Molecule Inhibitor Of ASK1 As a Potent Anti-Platelet Agent

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 20-20
Author(s):  
Meghna Ulhas Naik ◽  
Maloney David ◽  
Ramya Turaga ◽  
Hidinori Ichijo ◽  
Ulhas P Naik
Keyword(s):  
Platelet Aggregation ◽  
Bleeding Time ◽  
Conflicts Of Interest ◽  
Thrombus Formation ◽  
Receptor Activation ◽  
Human Platelets ◽  
Dependent Manner ◽  
Genetic Ablation ◽  
Fibrinogen Receptor ◽  
Molecule Inhibitor

Abstract Apoptosis signal-regulating kinase (ASK1) is a serine/threonine kinase, belonging to the MAP kinase-kinase-kinase family, which is activated in response to stress. However, its presence and role in platelets are not known. We found that ASK1 is expressed in platelets and is rapidly activated during platelet stimulation by various agonists in a dose-dependent manner. In addition, we found that TRAF2/6, known endogenous activators of ASK1, are expressed in platelets and associate with ASK1 upon platelet activation with agonists. Furthermore, genetic ablation of Ask1 significantly delayed tail-bleeding time (P=0.2x10-9). While WT mice showed an average bleeding time of 100 s, the Ask1 null mice had an average bleeding time of 576 s. A carotid artery injury induced by 10% FeCl3 showed a significantly increased (P=0.0003) time of occlusion and unstable thrombus formation in Ask1 null mice. Furthermore, we found that loss of Ask1 renders significant protection to the mice from pulmonary thromboembolism induced by a mixture of collagen and epinephrine as determined by increased survival and lack of large occlusive thrombi in the lung. We also found that ADP- and AYPGKF (PAR4 receptor peptide) -induced platelet aggregation was diminished in Ask1 null mice compared to WT mice. Furthermore, PAR4 peptide-induced alpha- and dense-granular secretion was also reduced in Ask1 null platelets compared to WT. Interestingly, we also found that Ask1 null platelets bind less FITC-fibrinogen compared to the WT upon activation by PAR4 peptide. Furthermore, thrombin failed to activate MKK6 and p38 in Ask1 knockout platelets, showing that Ask1 is indispensable for p38 activation by thrombin. These results indicated that ASK1 regulates platelet function by augmenting platelet secretion as well as fibrinogen receptor activation, making it an important target for combating thrombosis. We therefore synthesized a novel and highly specific ASK1 inhibitor, N-(6-(1H-imidazol-1-yl)imidazo[1,2-a]pyridin-2-yl)-4-(tert-butyl)benzamide (IPTB) based on the published report. IPTB has been found to be a very potent inhibitor that inhibits ASK1 activity at nM concentrations. IPTB is also highly specific to ASK1 and does not affect activities of related protein kinases such as ASK2, MEKK1, TAK1, and ERK1. We found that in human platelets, IPTB dose-dependently inhibits p38 activation induced by a variety of platelet agonists. Furthermore, IPTB dose-dependently inhibited ADP and PAR4 peptide-induced platelet aggregation. Interestingly, IPTB also dose-dependently inhibited platelet spreading on immobilized fibrinogen. Our results strongly suggest that the dose of IPTB could be adjusted so that it attenuates thrombosis without affecting hemostasis. This development would make IPTB a novel potential therapeutic agent to be used to combat thrombotic disorders. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Repurposing cabozantinib with therapeutic potential in KIT-driven t(8;21) acute myeloid leukaemias

2021 ◽  
Author(s):  
Kuan-Wei Su ◽  
Da-Liang Ou ◽  
Yu-Hsuan Fu ◽  
Hwei-Fang Tien ◽  
Hsin-An Hou ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Ribosome Biogenesis ◽  
Kinase Inhibitor ◽  
Therapeutic Potential ◽  
Xenograft Model ◽  
Sequencing Analysis ◽  
Dependent Manner ◽  
Leukocyte Activation ◽  
Mouse Xenograft Model ◽  
Acute Myeloid

AbstractCabozantinib is an orally available, multi-target tyrosine kinase inhibitor approved for the treatment of several solid tumours and known to inhibit KIT tyrosine kinase. In acute myeloid leukaemia (AML), aberrant KIT tyrosine kinase often coexists with t(8;21) to drive leukaemogenesis. Here we evaluated the potential therapeutic effect of cabozantinib on a selected AML subtype characterised by t(8;21) coupled with KIT mutation. Cabozantinib exerted substantial cytotoxicity in Kasumi-1 cells with an IC50 of 88.06 ± 4.32 nM, which was well within clinically achievable plasma levels. The suppression of KIT phosphorylation and its downstream signals, including AKT/mTOR, STAT3, and ERK1/2, was elicited by cabozantinib treatment and associated with subsequent alterations of cell cycle- and apoptosis-related molecules. Cabozantinib also disrupted the synthesis of an AML1-ETO fusion protein in a dose- and time-dependent manner. In a mouse xenograft model, cabozantinib suppressed tumourigenesis at 10 mg/kg and significantly prolonged survival of the mice. Further RNA-sequencing analysis revealed that mTOR-mediated signalling pathways were substantially inactivated by cabozantinib treatment, causing the downregulation of ribosome biogenesis and glycolysis, along with myeloid leukocyte activation. We suggest that cabozantinib may be effective in the treatment of AML with t(8;21) and KIT mutation. Relevant clinical trials are warranted.

Tyrosine Kinase Inhibitor Sunitinib Delays Platelet-Induced Coagulation: Additive Effects of Aspirin

2021 ◽  
Author(s):  
Delia I. Fernández ◽  
Alicia Veninga ◽  
Bibian M. E. Tullemans ◽  
Constance C. F. M. J. Baaten ◽  
Linsey J. F. Peters ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Tyrosine Kinase Inhibitor ◽  
Cancer Patients ◽  
Kinase Inhibitor ◽  
Synergistic Effects ◽  
Thrombus Formation ◽  
Type I ◽  
Glycoprotein Vi ◽  
Fibrin Formation ◽  
Increased Risk

Abstract Background Sunitinib is a multitarget tyrosine kinase inhibitor (TKI) used for cancer treatment. In platelets, sunitinib affects collagen-induced activation under noncoagulating conditions. We investigated (1) the effects of sunitinib on thrombus formation induced by other TK-dependent receptors, and (2) the effects under coagulating conditions. Cardiovascular disease is a comorbidity in cancer patients, resulting in possible aspirin treatment. Sunitinib and aspirin are associated with increased bleeding risk, and therefore we also investigated (3) the synergistic effects of these compounds on thrombus and fibrin formation. Methods Blood or isolated platelets from healthy volunteers or cancer patients were incubated with sunitinib and/or aspirin or vehicle. Platelet activation was determined by TK phosphorylation, flow cytometry, changes in [Ca2+]i, aggregometry, and whole blood perfusion over multiple surfaces, including collagen with(out) tissue factor (TF) was performed. Results Sunitinib reduced thrombus formation and phosphatidylserine (PS) exposure under flow on collagen type I and III. Also, sunitinib inhibited glycoprotein VI-induced TK phosphorylation and Ca2+ elevation. Upon TF-triggered coagulation, sunitinib decreased PS exposure and fibrin formation. In blood from cancer patients more pronounced effects of sunitinib were observed in lung and pancreatic as compared to neuroglioblastoma and other cancer types. Compared to sunitinib alone, sunitinib plus aspirin further reduced platelet aggregation, thrombus formation, and PS exposure on collagen under flow with(out) coagulation. Conclusion Sunitinib suppresses collagen-induced procoagulant activity and delays fibrin formation, which was aggravated by aspirin. Therefore, we urge for awareness of the combined antiplatelet effects of TKIs with aspirin, as this may result in increased risk of bleeding.

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