Cancer Burden Is Controlled by Mural Cell-ß3-Integrin Regulated Crosstalk with Tumor Cells.

Enhanced blood vessel (BV) formation is thought to drive tumor growth through elevated nutrient delivery. However, this observation has overlooked potential roles for mural cells in directly affecting tumor growth independent of BV function. Here we provide clinical data correlating high percentages of mural-ß3-integrin-negative tumor BVs with increased tumor sizes but no effect on BV numbers. Mural-ß3-integrin loss also enhances tumor growth in implanted and autochthonous mouse tumor models with no detectable effects on BV numbers or function. At a molecular level, mural-cell ß3-integrin loss enhances signaling via FAK-p-HGFR-p-Akt-p-p65, driving CXCL1, CCL2, and TIMP-1 production. In particular, mural-cell-derived CCL2 stimulates tumor cell MEK1-ERK1/2-ROCK2-dependent signaling and enhances tumor cell survival and tumor growth. Overall, our data indicate that mural cells can control tumor growth via paracrine signals regulated by ß3-integrin, providing a previously unrecognized mechanism of cancer growth control.

PI(3,4)P2-mediated membrane tubulation promotes integrin trafficking and invasive cell migration.

Invadopodia are integrin-mediated adhesions with abundant PI(3,4)P2 However, the functional role of PI(3,4)P2 in adhesion signaling remains unclear. Here, we find that the PI(3,4)P2 biogenesis regulates the integrin endocytosis at invadopodia. PI(3,4)P2 is locally produced by PIK3CA and SHIP2 and is concentrated at the trailing edge of the invadopodium arc. The PI(3,4)P2-rich compartment locally forms small puncta (membrane buds) in a SNX9-dependent manner, recruits dynein activator Hook1 through AKTIP, and rearranges into micrometer-long tubular invaginations (membrane tubes). The uncurving membrane tube extends rapidly, follows the retrograde movement of dynein along microtubule tracks, and disconnects from the plasma membrane. Activated integrin-beta3 is locally internalized through the pathway of PI(3,4)P2-mediated membrane invagination and is then actively recycled. Blockages of PI3K, SHIP2, and SNX9 suppress integrin-beta3 endocytosis, delay adhesion turnover, and impede transwell invasion of MEF-Src and MDA-MB-231 cells. Thus, the production of PI(3,4)P2 promotes invasive cell migration by stimulating the trafficking of integrin receptor at the invadopodium.

Application of Funnel Metadynamics to the Platelet Integrin αIIbß3 in Complex with an RGD Peptide.

Integrin αIIbß3 mediates platelet aggregation by binding the Arginyl-Glycyl-Aspartic acid (RGD) sequence of fibrinogen. RGD binding occurs at a site topographically proximal to the αIIb and ß3 subunits, promoting the conformational activation of the receptor from bent to extended states. While several experimental approaches have characterized RGD binding to αIIbß3 integrin, applying computational methods has been significantly more challenging due to limited sampling and the need for a priori information regarding the interactions between the RGD peptide and integrin. In this study, we employed all-atom simulations using funnel metadynamics (FM) to evaluate the interactions of an RGD peptide with the αIIb and ß3 subunits of integrin. FM incorporates an external history-dependent potential on selected degrees of freedom while applying a funnel-shaped restraint potential to limit RGD exploration of the unbound state. Furthermore, it does not require a priori information about the interactions, enhancing the sampling at a low computational cost. Our FM simulations reveal significant molecular changes in the ß3 subunit of integrin upon RGD binding and provide a free-energy landscape with a low-energy binding mode surrounded by higher-energy prebinding states. The strong agreement between previous experimental and computational data and our results highlights the reliability of FM as a method for studying dynamic interactions of complex systems such as integrin.

Integrin ß3 Mediates Sepsis and Mechanical Ventilation-Associated Pulmonary Fibrosis Through Glycometabolic Reprogramming.

Mechanical ventilation (MV) has become a clinical first-line treatment option for patients with respiratory failure. However, it was unclear whether MV further aggravates the process of sepsis-associated pulmonary fibrosis and eventually leads to sepsis and mechanical ventilation-associated pulmonary fibrosis (S-MVPF). This study aimed to explore the mechanism of S-MVPF concerning integrin ß3 activation in glycometabolic reprogramming of lung fibroblasts. We found that MV exacerbated sepsis-associated pulmonary fibrosis induced by lipopolysaccharide, which was accompanied by proliferation of lung fibroblasts, increased deposition of collagen in lung tissue, and increased procollagen type I carboxy-terminal propeptide in the bronchoalveolar lavage fluid. A large number of integrin ß3- and pyruvate kinase M2-positive fibroblasts were detected in lung tissue after stimulation with lipopolysaccharide and MV, with an increase in lactate dehydrogenase A expression and lactate levels. S-MVPF was primarily attenuated in integrin ß3-knockout mice, which also resulted in a decrease in the levels of pyruvate kinase M2, lactate dehydrogenase A, and lactate. In conclusion, MV aggravated sepsis-associated pulmonary fibrosis, with glycometabolic reprogramming mediated by integrin ß3 activation. Thus, integrin ß3-mediated glycometabolic reprogramming might be a potential therapeutic target for S-MVPF.

Screening a DNA Aptamer Specifically Targeting Integrin ß3 and Partially Inhibiting Tumor Cell Migration.

Due to its key roles in malignant tumor progression and reprograming of the tumor microenvironment, integrin ß3 has attracted great attention as a new target for tumor therapy. However, the structure-function relationship of integrins ß3 remains incompletely understood, leading to the shortage of specific and effective targeting probes. This work uses a purified extracellular domain of integrin ß3 and integrin ß3-positive cells to screen aptamers, specifically targeting integrin ß3 in the native conformation on live cells through the SELEX approach. Following meticulous truncation and characterization of the initial aptamer candidates, the optimized aptamer S10yh2 was produced, exhibiting a low equilibrium dissociation constant (Kd) in the nanomolar range. S10yh2 displays specific recognition of cancer cells with varying levels of integrin ß3 expression and demonstrates favorable stability in serum. Subsequent analysis of docking sites revealed that S10yh2 binds to the seven amino acid residues located in the core region of integrin ß3. The S10yh2 aptamer can downregulate the level of integrin heterodimer αvß3 on integrin ß3 overexpressed cancer cells and partially inhibit cell migration behavior. In summary, S10yh2 is a promising probe with a small size, simple synthesis, good stability, high binding affinity, and selectivity. It therefore holds great potential for investigating the structure-function relationship of integrins.

Protein kinase B (AKT) upregulation and Thy-1-αvß3 integrin-induced phosphorylation of Connexin43 by activated AKT in astrogliosis.

BACKGROUND: In response to brain injury or inflammation, astrocytes undergo hypertrophy, proliferate, and migrate to the damaged zone. These changes, collectively known as "astrogliosis", initially protect the brain; however, astrogliosis can also cause neuronal dysfunction. Additionally, these astrocytes undergo intracellular changes involving alterations in the expression and localization of many proteins, including αvß3 integrin. Our previous reports indicate that Thy-1, a neuronal glycoprotein, binds to this integrin inducing Connexin43 (Cx43) hemichannel (HC) opening, ATP release, and astrocyte migration. Despite such insight, important links and molecular events leading to astrogliosis remain to be defined. METHODS: Using bioinformatics approaches, we analyzed different Gene Expression Omnibus datasets to identify changes occurring in reactive astrocytes as compared to astrocytes from the normal mouse brain. In silico analysis was validated by both qRT-PCR and immunoblotting using reactive astrocyte cultures from the normal rat brain treated with TNF and from the brain of a hSOD1G93A transgenic mouse model. We evaluated the phosphorylation of Cx43 serine residue 373 (S373) by AKT and ATP release as a functional assay for HC opening. In vivo experiments were also performed with an AKT inhibitor (AKTi). RESULTS: The bioinformatics analysis revealed that genes of the PI3K/AKT signaling pathway were among the most significantly altered in reactive astrocytes. mRNA and protein levels of PI3K, AKT, as well as Cx43, were elevated in reactive astrocytes from normal rats and from hSOD1G93A transgenic mice, as compared to controls. In vitro, reactive astrocytes stimulated with Thy-1 responded by activating AKT, which phosphorylated S373Cx43. Increased pS373Cx43 augmented the release of ATP to the extracellular medium and AKTi inhibited these Thy-1-induced responses. Furthermore, in an in vivo model of inflammation (brain damage), AKTi decreased the levels of astrocyte reactivity markers and S373Cx43 phosphorylation. CONCLUSIONS: Here, we identify changes in the PI3K/AKT molecular signaling network and show how they participate in astrogliosis by regulating the HC protein Cx43. Moreover, because HC opening and ATP release are important in astrocyte reactivity, the phosphorylation of Cx43 by AKT and the associated increase in ATP release identify a potential therapeutic window of opportunity to limit the adverse effects of astrogliosis.

An alternate covalent form of platelet αIIbß3 integrin that resides in focal adhesions and has altered function.

The αIIbß3 integrin receptor coordinates platelet adhesion, activation, and mechanosensing in thrombosis and hemostasis. Using differential cysteine alkylation and mass spectrometry, we have identified a disulfide bond in the αIIb subunit linking cysteines 490 and 545 that is missing in ∼1 in 3 integrin molecules on the resting and activated human platelet surface. This alternate covalent form of αIIbß3 is predetermined as it is also produced by human megakaryoblasts and baby hamster kidney fibroblasts transfected with recombinant integrin. From coimmunoprecipitation experiments, the alternate form selectively partitions into focal adhesions on the activated platelet surface. Its function was evaluated in baby hamster kidney fibroblast cells expressing a mutant integrin with an ablated C490-C545 disulfide bond. The disulfide mutant integrin has functional outside-in signaling but extended residency time in focal adhesions due to a reduced rate of clathrin-mediated integrin internalization and recycling, which is associated with enhanced affinity of the αIIb subunit for clathrin adaptor protein 2. Molecular dynamics simulations indicate that the alternate covalent form of αIIb requires higher forces to transition from bent to open conformational states that is in accordance with reduced affinity for fibrinogen and activation by manganese ions. These findings indicate that the αIIbß3 integrin receptor is produced in various covalent forms that have different cell surface distribution and function. The C490, C545 cysteine pair is conserved across all 18 integrin α subunits, and the disulfide bond in the αV and α2 subunits in cultured cells is similarly missing, suggesting that the alternate integrin form and function are also conserved.

Crystal structure of the FERM-folded talin head reveals the determinants for integrin binding.

Binding of the intracellular adapter proteins talin and its cofactor, kindlin, to the integrin receptors induces integrin activation and clustering. These processes are essential for cell adhesion, migration, and organ development. Although the talin head, the integrin-binding segment in talin, possesses a typical FERM-domain sequence, a truncated form has been crystallized in an unexpected, elongated form. This form, however, lacks a C-terminal fragment and possesses reduced ß3-integrin binding. Here, we present a crystal structure of a full-length talin head in complex with the ß3-integrin tail. The structure reveals a compact FERM-like conformation and a tightly associated N-P-L-Y motif of ß3-integrin. A critical C-terminal poly-lysine motif mediates FERM interdomain contacts and assures the tight association with the ß3-integrin cytoplasmic segment. Removal of the poly-lysine motif or disrupting the FERM-folded configuration of the talin head significantly impairs integrin activation and clustering. Therefore, structural characterization of the FERM-folded active talin head provides fundamental understanding of the regulatory mechanism of integrin function.

Design, Synthesis and Anti-Melanoma Activity of Novel Annexin V Derivative with ß3-Integrin Affinity.

Tumor tissues often exhibit unique integrin receptor presentation during development, such as high exposures of αvß3 and αIIbß3 integrins. These features are not present in normal tissues. The induction of selective thrombosis and infarction in the tumor-feeding vessels, as well as specific antagonism of αvß3 integrin on the surface of tumor endothelial cells, is a potential novel antitumor strategy. The Echistatin-Annexin V (EAV) fusion protein is a novel Annexin V (ANV) derivative that possesses a high degree of αvß3 and αIIbß3 integrin receptor recognition and binding characteristics while retaining the specific binding ability of the natural ANV molecule for phosphatidylserine (PS). We systematically investigated the biological effects of this novel molecule with superimposed functions on mouse melanoma. We found that EAV inhibited the viability and migration of B16F10 murine melanoma cells in a dose-dependent manner, exhibited good tumor suppressive effects in a xenograft mouse melanoma model, strongly induced tumor tissue necrosis in mice, and targeted the inhibition of angiogenesis in mouse melanoma tumor tissue. EAV exhibited stronger biological effects than natural ANV molecules in inhibiting melanoma in mice. The unique biological effects of EAV are based on its high ß3-type integrin receptor-specific recognition and binding ability, as well as its highly selective binding to PS molecules. Based on these findings, we propose that EAV-mediated tumor suppression is a novel and promising antitumor strategy that targets both PS- and integrin ß3-positive tumor neovascularization and the tumor cells themselves, thus providing a possible mechanism for the treatment of melanoma.

Integrin ß3-Mediated Cell Senescence Associates with Gut Inflammation and Intestinal Degeneration in Models of Alzheimer's Disease.

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by memory loss and personality changes that ultimately lead to dementia. Currently, 50 million people worldwide suffer from dementia related to AD, and the pathogenesis underlying AD pathology and cognitive decline is unknown. While AD is primarily a neurological disease of the brain, individuals with AD often experience intestinal disorders, and gut abnormalities have been implicated as a major risk factor in the development of AD and relevant dementia. However, the mechanisms that mediate gut injury and contribute to the vicious cycle between gut abnormalities and brain injury in AD remain unknown. In the present study, a bioinformatics analysis was performed on the proteomics data of variously aged AD mouse colon tissues. We found that levels of integrin ß3 and ß-galactosidase (ß-gal), two markers of cellular senescence, increased with age in the colonic tissue of mice with AD. The advanced artificial intelligence (AI)-based prediction of AD risk also demonstrated the association between integrin ß3 and ß-gal and AD phenotypes. Moreover, we showed that elevated integrin ß3 levels were accompanied by senescence phenotypes and immune cell accumulation in AD mouse colonic tissue. Further, integrin ß3 genetic downregulation abolished upregulated senescence markers and inflammatory responses in colonic epithelial cells in conditions associated with AD. We provide a new understanding of the molecular actions underpinning inflammatory responses during AD and suggest integrin ß3 may function as novel target mediating gut abnormalities in this disease.

SHIP1 Controls Internal Platelet Contraction and αIIbß3 Integrin Dynamics in Early Platelet Activation.

The Src homology 2 domain-containing inositol 5-phosphatase 1 (SHIP1) is known to dephosphorylate PtdIns(3,4,5)P3 into PtdIns(3,4)P2 and to interact with several signaling proteins though its docking functions. It has been shown to negatively regulate platelet adhesion and spreading on a fibrinogen surface and to positively regulate thrombus growth. In the present study, we have investigated its role during the early phase of platelet activation. Using confocal-based morphometric analysis, we found that SHIP1 is involved in the regulation of cytoskeletal organization and internal contractile activity in thrombin-activated platelets. The absence of SHIP1 has no significant impact on thrombin-induced Akt or Erk1/2 activation, but it selectively affects the RhoA/Rho-kinase pathway and myosin IIA relocalization to the cytoskeleton. SHIP1 interacts with the spectrin-based membrane skeleton, and its absence induces a loss of sustained association of integrins to this network together with a decrease in αIIbß3 integrin clustering following thrombin stimulation. This αIIbß3 integrin dynamics requires the contractile cytoskeleton under the control of SHIP1. RhoA activation, internal platelet contraction, and membrane skeleton integrin association were insensitive to the inhibition of PtdIns(3,4,5)P3 synthesis or SHIP1 phosphatase activity, indicating a role for the docking properties of SHIP1 in these processes. Altogether, our data reveal a lipid-independent function for SHIP1 in the regulation of the contractile cytoskeleton and integrin dynamics in platelets.

The ß8 integrin EGF domains support a constitutive extended conformation, and the cytoplasmic domain impairs outside-in signaling.

Integrins are transmembrane proteins that transmit bi-directional signals across the cell membrane through global structural rearrangement among three different conformational states: bent, extended- closed, and extended-open conformations. However, the ß8 integrin is distinctive and may adopt only one conformation, that is, extended-closed conformation, with high affinity for ligands under physiological conditions, and may not transmit bi-directional signals like other integrin members. It is unclear how different ß8 domains affect its unique conformation and signaling. We swapped different domains of integrin ß3 with those of ß8 and investigated how they affected integrin ligand binding, global conformation, and outside-in signaling. We found that the ß8 epidermal growth factor (EGF) domains increased integrin ligand binding ability and contributed to its extended conformation. By comparison, the ß8 transmembrane and cytoplasmic domains had little effect on ligand binding or global conformation. The ß8 EGF and transmembrane domains did not affect integrin-mediated cell adhesion, cell spreading, focal adhesion formation, or colocalization of integrin with other proteins, but the cytoplasmic domain had a defective effect on outside-in signaling. Our results showed that different domains of ß8 play various roles on its unique conformation, ligand binding, and signaling, which are considered atypical among integrin members.

Positive feedback regulation of lncRNA TPT1-AS1 and ITGB3 promotes cell growth and metastasis in pancreatic cancer.

Emerging evidence has indicated that long noncoding RNAs (lncRNAs) are potential biomarkers and play crucial roles in cancer development. However, the functions and underlying mechanisms of lncRNA TPT1-AS1 in pancreatic ductal adenocarcinoma (PDAC) remain elusive. RNAseq data of PDAC tissues and normal tissues were analyzed, and lncRNAs which were associated with PDAC prognosis were identified. The clinical relevance of TPT1-AS1 for PDAC patients was explored, and the effects of TPT1-AS1 in PDAC progression were investigated in vitro and in vivo. LncRNA TPT1-AS1 was highly expressed in PDAC, and high TPT1-AS1 levels predicted a poor prognosis. Moreover, functional experiments revealed that TPT1-AS1 promoted pancreatic cancer cell proliferation, migration, invasion, and epithelial-to-mesenchymal transition (EMT) process in vitro and in vivo. Mechanistically, TPT1-AS1 functioned as an endogenous sponge for miR-30a-5p, which increased integrin ß3 (ITGB3) level in pancreatic cancer cells. Conversely, our data revealed that ITGB3 could activate the transcription factor signal transducer and activator of transcription 3 (STAT3), which in turn bound directly to the TPT1-AS1 promoter and affected the expression of TPT1-AS1, thus forming a positive feedback loop with TPT1-AS1. Taken together, our results uncovered a reciprocal loop of TPT1-AS1 and ITGB3 which contributed to pancreatic cancer growth and development, and indicated that TPT1-AS1 might serve as a novel potential diagnostic biomarker and therapeutic target for PDAC patients.

The F1 loop of the talin head domain acts as a gatekeeper in integrin activation and clustering.

Integrin activation and clustering by talin are early steps of cell adhesion. Membrane-bound talin head domain and kindlin bind to the ß integrin cytoplasmic tail, cooperating to activate the heterodimeric integrin, and the talin head domain induces integrin clustering in the presence of Mn2+ Here we show that kindlin-1 can replace Mn2+ to mediate ß3 integrin clustering induced by the talin head, but not that induced by the F2-F3 fragment of talin. Integrin clustering mediated by kindlin-1 and the talin head was lost upon deletion of the flexible loop within the talin head F1 subdomain. Further mutagenesis identified hydrophobic and acidic motifs in the F1 loop responsible for ß3 integrin clustering. Modeling, computational and cysteine crosslinking studies showed direct and catalytic interactions of the acidic F1 loop motif with the juxtamembrane domains of α- and ß3-integrins, in order to activate the ß3 integrin heterodimer, further detailing the mechanism by which the talin-kindlin complex activates and clusters integrins. Moreover, the F1 loop interaction with the ß3 integrin tail required the newly identified compact FERM fold of the talin head, which positions the F1 loop next to the inner membrane clasp of the talin-bound integrin heterodimer.This article has an associated First Person interview with the first author of the paper.

Talin-1 is the principal platelet Rap1 effector of integrin activation.

Ras-related protein 1 (Rap1) is a major convergence point of the platelet-signaling pathways that result in talin-1 binding to the integrin ß cytoplasmic domain and consequent integrin activation, platelet aggregation, and effective hemostasis. The nature of the connection between Rap1 and talin-1 in integrin activation is an important remaining gap in our understanding of this process. Previous work identified a low-affinity Rap1-binding site in the talin-1 F0 domain that makes a small contribution to integrin activation in platelets. We recently identified an additional Rap1-binding site in the talin-1 F1 domain that makes a greater contribution than F0 in model systems. Here we generated mice bearing point mutations, which block Rap1 binding without affecting talin-1 expression, in either the talin-1 F1 domain (R118E) alone, which were viable, or in both the F0 and F1 domains (R35E,R118E), which were embryonic lethal. Loss of the Rap1-talin-1 F1 interaction in platelets markedly decreases talin-1-mediated activation of platelet ß1- and ß3-integrins. Integrin activation and platelet aggregation in mice whose platelets express only talin-1(R35E, R118E) are even more impaired, resembling the defect seen in platelets lacking both Rap1a and Rap1b. Although Rap1 is important in thrombopoiesis, platelet secretion, and surface exposure of phosphatidylserine, loss of the Rap1-talin-1 interaction in talin-1(R35E, R118E) platelets had little effect on these processes. These findings show that talin-1 is the principal direct effector of Rap1 GTPases that regulates platelet integrin activation in hemostasis.

The 14-3-3ζ-c-Src-integrin-ß3 complex is vital for platelet activation.

Several adaptor molecules bind to cytoplasmic tails of ß-integrins and facilitate bidirectional signaling, which is critical in thrombosis and hemostasis. Interfering with integrin-adaptor interactions spatially or temporally to inhibit thrombosis without affecting hemostasis is an attractive strategy for the development of safe antithrombotic drugs. We show for the first time that the 14-3-3ζ-c-Src-integrin-ß3 complex is formed during platelet activation. 14-3-3ζ-c-Src interaction is mediated by the -PIRLGLALNFSVFYYE- fragment (PE16) on the 14-3-3ζ and SH2-domain on c-Src, whereas the 14-3-3ζ-integrin-ß3 interaction is mediated by the -ESKVFYLKMKGDYYRYL- fragment (EL17) on the 14-3-3ζ and -KEATSTF- fragment (KF7) on the ß3-integrin cytoplasmic tail. The EL17-motif inhibitor, or KF7 peptide, interferes with the formation of the 14-3-3ζ-c-Src-integrin-ß3 complex and selectively inhibits ß3 outside-in signaling without affecting the integrin-fibrinogen interaction, which suppresses thrombosis without causing significant bleeding. This study characterized a previously unidentified 14-3-3ζ-c-Src-integrin-ß3 complex in platelets and provided a novel strategy for the development of safe and effective antithrombotic treatments.

Shear and Integrin Outside-In Signaling Activate NADPH-Oxidase 2 to Promote Platelet Activation.

[Figure: see text].

Sortase A-mediated cyclization of novel polycyclic RGD peptides for ανß3 integrin targeting.

Cyclic arginine-glycine-aspartic (RGD) peptides that specifically bind to integrin ανß3 have been developed for drug delivery, tracers, and imaging for tumor diagnosis and treatment. Herein, a series of polycyclic RGD peptides containing dual, tri, and tetra rings were designed and synthesized through sortase A-mediated ligation. An in vitro test on cell adhesion inhibition indicated that the RGD peptide containing tricylic structure exhibited outstanding potency and selectivity for ανß3 integrin.

Recombinant expression a novel fibronectin-collage fusion peptide modulating stem cell stemness via integrin ß3.

Constructing bionic extracellular matrix (ECM) is an attractive proposition for tissue engineering and clinical regeneration therapy involving the stemness of stem cells. Here, a novel recombinant protein fibronectin-collagen peptide (FCP) was designed to modulate the function of ECM expressed by Picha. pastoris strain X33. This FCP promotes cell migration and adhesion and maintains rBMSC stemness by binding integrin ß3. Its effects were blocked by both integrin ß3 siRNA and the integrin ß3 inhibitor Cilengitide. A template-independent ab initio prediction modeling approach is the best approach to construct a stable FCP protein model, which predicts the binding sites between FCP and integrin ß3. FCP may be used in the in vitro culture and clinical regeneration of stem cells that highly express integrin ß3, such as hematopoietic stem cells. The study provides information on the molecular structure of FCP and its bioactivity, which can be used to design new compounds. KEY POINTS: • Design a novel recombinant fibronectin-collagen peptide biomimetic ECM. • FCP promotes cell adhesion, migration, and proliferation. • Predicted and verified FCP structure and affinity with integrin ß3. • FCP binds integrin ß3 to maintain rBMSC stemness.

Exploratory Use of Glycoprotein IIb/IIIa Inhibition in Prevention of Blalock-Taussig Shunt Thrombosis.

OBJECTIVES: Morbidity and mortality related to modified Blalock-Taussig shunt (mBTTS) thrombosis remain a significant risk. Platelet inhibition following mBTTS may reduce this risk. However, oral antiplatelet agents have variable absorption following surgery. We determine risk factors for mBTTS thrombosis and hypothesize that IV glycoprotein IIb/IIIa inhibitor (tirofiban) as a bridge to oral aspirin reduces the rate of shunt thrombosis in the immediate postoperative period. End points within the 14-day follow-up period include mBTTS thrombosis, overall thrombosis, bleeding, length of stay, and mortality. DESIGN: Retrospective, Institutional Review Board-approved cohort study. SETTING: Single-center cardiac ICU. PATIENTS: Patients under the age of 18 who had an mBTTS placed within the study period of January 2008 to December 2018 were included. INTERVENTIONS: Patients were divided into two groups: standard of care (SOC) anticoagulation alone and SOC with tirofiban as a bridge to oral aspirin. MEASUREMENTS AND MAIN RESULTS: Freedom from mBTTS thrombosis was estimated using the Kaplan-Meier method. A multivariable predictive model using the four most significant risk factors was developed using logistic regression. A total of 272 patients were included: 36 subjects in the SOC/tirofiban group and 236 in the SOC group. Shunt thrombosis occurred in 26 (11%) SOC group with zero in SOC/tirofiban group ( p = 0.03). The median time to thrombosis was 0 days (range, 0-12 d). The area under the curve for the predictive model (anticoagulation group, history of coagulopathy, intraoperative shunt clipping, and shunt size/weight ratio) is 0.790 ( p < 0.001). Prevalence of bleeding and mortality was not significantly different between the groups. CONCLUSIONS: Highest risk for shunt thrombosis following mBTTS occurs within the first few days after surgical procedure. Tirofiban is a safe addition to SOC and may be an effective strategy to prevent early mBTTS thrombosis.