Nanoscale Organization of TRAIL Trimers using DNA Origami to Promote Clustering of Death Receptor and Cancer Cell Apoptosis.

Through inducing death receptor (DR) clustering to activate downstream signaling, tumor necrosis factor related apoptosis inducing ligand (TRAIL) trimers trigger apoptosis of tumor cells. However, the poor agonistic activity of current TRAIL-based therapeutics limits their antitumor efficiency. The nanoscale spatial organization of TRAIL trimers at different interligand distances is still challenging, which is essential for the understanding of interaction pattern between TRAIL and DR. In this study, a flat rectangular DNA origami is employed as display scaffold, and an "engraving-printing" strategy is developed to rapidly decorate three TRAIL monomers onto its surface to form DNA-TRAIL3 trimer (DNA origami with surface decoration of three TRAIL monomers). With the spatial addressability of DNA origami, the interligand distances are precisely controlled from 15 to 60 nm. Through comparing the receptor affinity, agonistic activity and cytotoxicity of these DNA-TRAIL3 trimers, it is found that ≈40 nm is the critical interligand distance of DNA-TRAIL3 trimers to induce death receptor clustering and the resulting apoptosis.Finally, a hypothetical "active unit" model is proposed for the DR5 clustering induced by DNA-TRAIL3 trimers.

Combination of tumour-infarction therapy and chemotherapy via the co-delivery of doxorubicin and thrombin encapsulated in tumour-targeted nanoparticles.

Drugs that induce thrombosis in the tumour vasculature have not resulted in long-term tumour eradication owing to tumour regrowth from tissue in the surviving rim of the tumour, where tumour cells can derive nutrients from adjacent non-tumoral blood vessels and tissues. Here, we report the performance of a combination of tumour-infarction therapy and chemotherapy, delivered via chitosan-based nanoparticles decorated with a tumour-homing peptide targeting fibrin-fibronectin complexes overexpressed on tumour-vessel walls and in tumour stroma, and encapsulating the coagulation-inducing protease thrombin and the chemotherapeutic doxorubicin. Systemic administration of the nanoparticles into mice and rabbits bearing subcutaneous or orthotopic tumours resulted in higher tumour growth suppression and decreased tumour recurrence than nanoparticles delivering only thrombin or doxorubicin, with histological and haematological analyses indicating an absence of detectable toxicity. The co-administration of a cytotoxic payload and a protease to elicit vascular infarction in tumours with biodegradable tumour-targeted nanoparticles represents a promising strategy for improving the therapeutic index of coagulation-based tumour therapy.

Targeting Delivery of Platelets Inhibitor to Prevent Tumor Metastasis.

Activated platelets have a high affinity for tumor cells, and consequently, they can protect tumor cells from environmental stress and immune attacks. Therefore, preventing platelet-tumor cell interaction can lead to the elimination of circulating tumor cells via natural killer cells and finally metastasis inhibition. It is also shown that CREKA (Cys-Arg-Glu-Lys-Ala), a tumor-homing pentapeptide, targets fibrin-fibronectin complexes that are found on the tumor stroma and the vessel walls. In this study, we linked CREKA to Ticagrelor, a reversible antagonist of the P2Y12 receptor on platelets. In vitro experiments indicated that CREKA-Ticagrelor could not only inhibit the platelet-induced migration of tumor cells with an invasive phenotype but also prevent tumor-platelet interaction. In vivo antitumor and antimetastasis results of this drug showed that CREKA-Ticagrelor could specifically target the tumor tissues within 24 h post intravenous injection and suppress lung metastasis. Meanwhile, by having this antiplatelet drug targeted, its side effects were minimized, and bleeding risk was decreased. Thus, CREKA-Ticagrelor offers an efficient antimetastatic agent.

Epidermal Growth Factor Receptor-Targeting Peptide Nanoparticles Simultaneously Deliver Gemcitabine and Olaparib To Treat Pancreatic Cancer with Breast Cancer 2 ( BRCA2) Mutation.

Pancreatic cancer (PCa) is one of the most lethal malignancies, with a 5 year survival rate of less than 8%. Current treatment regiments have a low response rate in unselected patients. However, the subgroup of PCa patients with BRCA mutations may benefit from poly-ADP-ribose polymerase inhibitors (PARPi) due to their biological properties in DNA repair. Dose-limiting toxicity in normal tissues is frequently observed when PARPi are combined with other chemotherapies, and the co-delivery of two drugs to tumor sites at an adequate concentration is challenging. To address this issue, we have engineered an epidermal growth factor receptor (EGFR) targeting (with GE11 peptide) self-assembly amphiphilic peptide nanoparticle (GENP) to co-deliver gemcitabine and the PARPi olaparib to treat BRCA mutant PCa. The GENP was relatively stable, exhibited high encapsulation efficiency, and could coordinately release the two drugs in tumor milieu. Gemcitabine and olaparib showed strong synergistic actions in optimized conditions in vitro. The nanoparticle prolonged the half-life of both drugs and resulted in their tumor accumulation at the optimal therapeutic ratio in vivo. The drug-loaded nanoparticles were able to significantly suppress tumor growth in a murine PCa model with minimal side effects. Drug co-delivery of DNA damaging agents and PARP inhibitors via the GENP represents a promising approach for treatment of pancreatic cancers with molecular defects in the DNA repair pathway.

Specific tissue factor delivery using a tumor-homing peptide for inducing tumor infarction.

Targeting the human blood coagulation-inducing protein tissue factor (TF) to the tumor vasculature to induce infarction and disrupt the blood vessels has proven to be an effective approach for tumor therapy. In this study, we investigated the thrombogenic activity and anti-tumor potential of a novel fusion protein (tTF-CREKA) comprising the extracellular domain of human tissue factor (truncated TF, tTF) and a tumor targeting pentapeptide, Cys-Arg-Glu-Lys-Ala (CREKA). tTF is soluble and inactive in its free state, but when it is targeted to the plasma membrane of both tumor vessel endothelial cells and stromal cells by the CREKA peptide, its native coagulation-inducing activity is restored. Systemic administration of the tTF-CREKA fusion protein into tumor-bearing mice induced tumor-selective intravascular thrombosis and reduced tumor blood perfusion, consequently inhibiting tumor growth. The development of tTF-CREKA introduces a new method for treating a wide spectrum of solid tumors by selectively blocking tumor blood supply.

pHLIP-mediated targeting of truncated tissue factor to tumor vessels causes vascular occlusion and impairs tumor growth.

Occluding tumor blood supply by delivering the extracellular domain of coagulation-inducing protein tissue factor (truncated tissue factor, tTF) to tumor vasculature has enormous potential to eliminate solid tumors. Yet few of the delivery technologies are moved into clinical practice due to their non-specific tissue biodistribution and rapid clearance by the reticuloendothelial system. Here we introduced a novel tTF delivery method by generating a fusion protein (tTF-pHLIP) consisting of tTF fused with a peptide with a low pH-induced transmembrane structure (pHLIP). This protein targets the acidic tumor vascular endothelium and effectively induces local blood coagulation. tTF-pHLIP, wherein pHLIP is cleverly designed to mimic the natural tissue factor transmembrane domain, triggered thrombogenic activity of the tTF by locating it to the endothelial cell surface, as demonstrated by coagulation assays and confocal microscopy. Systemic administration of tTF-pHLIP into tumor-bearing mice selectively induced thrombotic occlusion of tumor vessels, reducing tumor perfusion and impairing tumor growth without overt side effects. Our work introduces a promising strategy for using tTF as an anti-cancer drug, which has great potential value for clinical applications.

Mechanism of platelet functional changes and effects of anti-platelet agents on in vivo hemostasis under different gravity conditions.

Serious thrombotic and hemorrhagic problems or even fatalities evoked by either microgravity or hypergravity occur commonly in the world. We recently reported that platelet functions are inhibited in microgravity environments and activated under high-G conditions, which reveals the pathogenesis for gravity change-related hemorrhagic and thrombotic diseases. However, the mechanisms of platelet functional variations under different gravity conditions remain unclear. In this study we show that the amount of filamin A coimmunoprecipitated with GPIbalpha was enhanced in platelets exposed to modeled microgravity and, in contrast, was reduced in 8 G-exposed platelets. Hypergravity induced actin filament formation and redistribution, whereas actin filaments were reduced in platelets treated with modeled microgravity. Furthermore, intracellular Ca2+ levels were elevated by hypergravity. Pretreatment of platelets with the cell-permeable Ca2+ chelator BAPTA-AM had no effect on cytoskeleton reorganization induced by hypergravity but significantly reduced platelet aggregation induced by ristocetin/hypergravity. Two anti-platelet agents, aspirin and tirofiban, effectively reversed the shortened tail bleeding time and reduced the death rate of mice exposed to hypergravity. Furthermore, the increased P-selectin surface expression was obviously reduced in platelets from mice treated with aspirin/hypergravity compared with those from mice treated with hypergravity alone. These data suggest that the actin cytoskeleton reorganization and intracellular Ca2+ level play key roles in the regulation of platelet functions in different gravitational environments. The results with anti-platelet agents not only further confirm the activation of platelets in vivo but also suggest a therapeutic potential for hypergravity-induced thrombotic diseases.

Calmodulin antagonists induce platelet apoptosis.

Calmodulin (CaM) antagonists induce apoptosis in various tumor models and inhibit tumor cell invasion and metastasis, thus some of which have been extensively used as anti-cancer agents. In platelets, CaM has been found to bind directly to the cytoplasmic domains of several platelet receptors. Incubation of platelets with CaM antagonists impairs the receptors-related platelet functions. However, it is still unknown whether CaM antagonists induce platelet apoptosis. Here we show that CaM antagonists N-(6-aminohexyl)-5-chloro-1-naphthalene sulfonamide (W7), tamoxifen (TMX), and trifluoperazine (TFP) induce apoptotic events in human platelets, including depolarization of mitochondrial inner transmembrane potential, caspase-3 activation, and phosphatidylserine exposure. CaM antagonists did not incur platelet activation as detected by P-selectin surface expression and PAC-1 binding. However, ADP-, botrocetin-, and alpha-thrombin-induced platelet aggregation, platelet adhesion and spreading on von Willebrand factor surface were significantly reduced in platelets pre-treated with CaM antagonists. Furthermore, cytosolic Ca(2+) levels were obviously elevated by both W7 and TMX, and membrane-permeable Ca(2+) chelator BAPTA-AM significantly reduced apoptotic events in platelets induced by W7. Therefore, these findings indicate that CaM antagonists induce platelet apoptosis. The elevation of the cytosolic Ca(2+) levels may be involved in the regulation of CaM antagonists-induced platelet apoptosis.

Hyperthermia induces platelet apoptosis and glycoprotein Ibalpha ectodomain shedding.

Hemorrhage is a significant pathological feature of some fever or hyperthermia-related diseases, such as dengue fever and heatstroke. Although the mechanisms of hemorrhage in these diseases are thought to be complex, whether there is an association between hemorrhage and hyperthermia or fever remains unclear. Platelets play a central role in maintaining integrity of endothelium and biological hemostasis. To explore the effect of hyperthermia on platelet physiology, platelet-rich plasma or washed platelets were incubated at hypothermia (22 degrees C), normothermia (37 degrees C) or hyperthermia (40 and 42 degrees C) for 1 or 2 hours. ADP and alpha-thrombin induced platelet aggregations were obviously reduced in platelets incubated at hyperthermia. Hyperthermia induced apoptotic events in platelets, including depolarization of mitochondrial inner transmembrane potential, caspase-3 dependent gelsolin cleavage and phosphatidylserine exposure. Furthermore, hyperthermia incurred platelet glycoprotein Ibalpha ectodomain shedding. Thus, these data suggest that hyperthermia induces platelet apoptosis and dysfunction. These findings have important implications for the pathogenesis of hemorrhage in fever or hyperthermia-related diseases, and also suggest that attention should be paid to platelet apoptosis under relatively high temperature conditions.

The role of calpain in the regulation of ADAM17-dependent GPIbalpha ectodomain shedding.

There are evidence that both a disintegrin and metalloproteinase 17 (ADAM17) and calpain are involved in platelet glycoprotein (GP)Ibalpha ectodomain cleavage. However, the relationship between the two enzymes in the shedding process remains unclear. Here we show that calcium ionophore A23187- and alpha-thrombin-induced GPIbalpha shedding is completely inhibited by the metalloproteinase inhibitor GM6001, whereas it is only partially inhibited by calpain inhibitors. Calpain activator dibucaine-induced GPIbalpha shedding was completely inhibited by both metalloproteinase and calpain inhibitors. On the other hand, calpain inhibitors did not inhibit GPIbalpha shedding induced by the reagents that specifically activate ADAM17. Furthermore, A23187-induced GPIbalpha shedding in Chinese hamster ovary cells expressing wild-type or mutant GPIb-IX was also partially inhibited by calpain inhibitors and almost completely inhibited by GM6001. Therefore, these data indicate that calpain plays an important role in the regulation of ADAM17-dependent GPIbalpha ectodomain shedding in both platelets and nucleated cells.

[Establishment of Chinese hamster ovary cell line expressing recombinant GPIb-IX complex].

The aim of this study was to construct Chinese Hamster Ovary (CHO) cell models expressing recombinant wild-type GPIb-IX and mutant GPIb-IX complex, so as to provide the platform to study the related physiologic functions of GPIb-IX. The plasmids were extracted from E.coli expressing wild-type or deletion mutant GPIbalpha and were identified by digestion with EcoR I. Three plasmids containing GPIbalpha, GPIbbeta, and GPIX genes were co-transfected into CHO cells, and then the expression of GPIb-IX complex was detected by immune coprecipitation, Western blot and flow cytometry. The results showed that the expression of GPIb-IX complex could be detected in the lysate and on the surface of CHO cells at 48 hours after transfection. In conclusion, CHO cell models expressing recombinant wild-type or mutation GPIb-IX complex has been successfully constructed.

Effects of microgravity and hypergravity on platelet functions.

Many serious thrombotic and haemorrhagic diseases or fatalities have been documented in human being exposed to microgravity or hypergravity environments, such as crewmen in space, roller coaster riders, and aircrew subjected to high-G training. Some possible related organs have been examined to explore the mechanisms underlying these gravity change-related diseases. However, the role of platelets which are the primary players in both thrombosis and haemostasis is unknown. Here we show that platelet aggregation induced by ristocetin or collagen and platelet adhesion to von Willebrand factor (VWF) were significantly decreased after platelets were exposed to simulated microgravity. Conversely, these platelet functions were increased after platelets were exposed to hypergravity. The tail bleeding time in vivo was significantly shortened in mice exposed to high-G force, whereas, was prolonged in hindlimb unloaded mice. Furthermore, three of 23 mice died after 15 minutes of -8 Gx stress. Platelet thrombi disseminated in the heart ventricle and blood vessels in the brain, lung, and heart from the dead mice. Finally, glycoprotein (GP) Ibalpha surface expression and its association with the cytoskeleton were significantly decreased in platelets exposed to simulated microgravity, and obviously increased in hypergravity-exposed platelets. These data indicate that the platelet functions are inhibited in microgravity environments, and activated under high-G conditions, suggesting a novel mechanism for gravity change-related haemorrhagic and thrombotic diseases. This mechanism has important implications for preventing and treating gravity change-related diseases, and also suggests that special attentions should be paid to human actions under different gravity conditions.