Platelet-tumor Cell Interactions Research Articles

Identification of Podoplanin Aptamers by SELEX for Protein Detection and Inhibition of Platelet Aggregation Stimulated by C-Type Lectin-like Receptor 2.

Tumor cell-induced platelet aggregation (TCIPA) is a mechanism for the protection of tumor cells in the bloodstream and the promotion of tumor progression and metastases. The platelet C-type lectin-like receptor 2 (CLEC-2) can bind podoplanin (PDPN) on a cancer cell surface to facilitate TCIPA. Selective blockage of PDPN-mediated platelet-tumor cell interaction is a plausible strategy for inhibiting metastases. In this study, we aimed to screen for aptamers, which are the single-stranded DNA oligonucleotides that form a specific three-dimensional structure, bind to specific molecular targets with high affinity and specificity, bind to PDPN, and interfere with PDPN/CLEC-2 interactions. The systematic evolution of ligands by exponential enrichment (SELEX) was employed to enrich aptamers that recognize PDPN. The initial characterization of ssDNA pools enriched by SELEX revealed a PDPN aptamer designated as A1 displaying parallel-type G-quadruplexes and long stem-and-loop structures and binding PDPN with a material with a dissociation constant (Kd) of 1.3 ± 1.2 nM. The A1 aptamer recognized both the native and denatured form of PDPN. Notably, the A1 aptamer was able to quantitatively detect PDPN proteins in Western blot analysis. The A1 aptamer could interfere with the interaction between PDPN and CLEC-2 and inhibit PDPN-induced platelet aggregation in a concentration-dependent manner. These findings indicated that the A1 aptamer is a candidate for the development of biosensors in detecting the levels of PDPN expression. The action by A1 aptamer could result in the prevention of tumor cell metastases, and if so, could become an effective pharmacological agent in treating cancer patients.

Ginsenoside Rb prevents the metastasis of hepatocarcinoma by blocking the platelet-tumor cell interaction.

The interaction between platelets and tumor cells is a crucial step in the progression of tumor metastasis. Blocking platelet-tumor cell interaction is a potential target against metastasis. Ginsenoside Rb (G-Rb) exhibits potential anti-tumor pharmacological properties and may offer a therapeutic option for cancer. This study aimed to investigate anti-metastatic effects of G-Rb through regulating the crosstalk of platelets with tumor cells. In order to explore anti-metastatic effects of G-Rb in vitro, HepG2 cell and platelets were co-cultured to mimic the interaction of platelets with tumor cells. Wound healing and Transwell assays were used to assess the effect of G-Rb on cell migration and invasion. The expression of epithelial-mesenchymal transition (EMT)-related markers was determined by RT-qPCR and western blot assays. The aggregation and activation of platelets were detected by flow cytometry. Moreover, a lung metastasis model of mice was established to evaluate inhibitory effects of G-Rb in vivo. Metastatic nodules on the lung surface were counted and sections of lung tissues were stained by H&E. G-Rb effectively suppressed tumor metastasis in the co-culture of platelets with HepG2 cell. First, G-Rb treatment significantly inhibited the migration and invasion of HepG2 cells induced by platelets. Second, the expressions of EMT-related markers, including N-cadherin, Snail, and MMP9, were decreased by the treatment of G-Rb in the presence of platelets. Meanwhile, G-Rb also suppressed platelet hyperactivity by regulating the adhesion to tumor cells, activation, TCIPA, and TGF-β1 secretion of platelets in vitro. In addition, the results of in vivo experiments proved G-Rb administration not only significantly decreased lung metastasis but also attenuated platelets aberrant aggregation and activation in vivo. Our findings showed that G-Rb inhibited tumor metastasis and platelet activation through mediating platelet-tumor cell interaction, indicating the potential values of G-Rb in tumor metastasis therapy.

Blocking tumor-platelet crosstalk to prevent tumor metastasis via reprograming glycolysis using biomimetic membrane-hybridized liposomes

Activated platelets promote tumor progression and metastasis through active interactions with cancer cells, especially in promoting epithelial-mesenchymal transition (EMT) of tumor cells and shedding tumor cells into the blood. Blocking platelet-tumor cell interactions can be a potential strategy to inhibit tumor metastasis. Platelet activation requires energy produced from aerobic glycolysis. Based on this, we propose a platelet suppression strategy by reprogramming glucose metabolism of platelets, which has an advantage over conventional antiplatelet treatment that has a risk of serious hemorrhage. We develop a biomimetic delivery system using platelet membrane-hybridized liposomes (PM-Lipo) for codelivery of quercetin and shikonin to simultaneously inhibit lactate transporter MCT-4 and a glycolytic enzyme PKM2 for achieving metabolic reprogramming of platelets and suppressing platelet activation. Notably, PM-Lipo can also inhibit glycolysis in cancer cells, which actually takes “two-birds-one-stone” action. Consequently, the platelet-tumor cell interactions are inhibited. Moreover, PM-Lipo can bind with circulating tumor cells and reduce their seeding in the premetastatic microenvironment. The in vivo studies further demonstrated that PM-Lipo can effectively suppress primary tumor growth and reduce lung metastasis without affecting inherited functions of platelets. Reprogramming glycolysis of platelets can remodel the tumor immune microenvironment, including suppression of Treg and stimulation of CTLs.

Enzyme-Induced Shape-Shifting Peptide Nanocarrier Coloaded with Paclitaxel and Dipyridamole Inhibits Platelet Function and Tumor Metastasis.

Tumor-associated platelets can bind to tumor cells and protect circulating tumor cells from NK-mediated immune surveillance. Tumor-associated platelets secrete cytokines to induce the epithelial-mesenchymal transition (EMT) in tumor cells, which promotes tumor metastasis. Combining chemotherapeutic agents with antiplatelet drugs can reduce the occurrence of metastasis, but the systemic application of chemotherapeutic agents and antiplatelet drugs is prone to causing serious side effects. Therefore, delivering drugs to the tumor microthrombus site for long-lasting inhibition is a problem that needs to be addressed. Here, we show that small molecule peptide nanoparticles containing the Cys-Arg-Glu-Lys-Ala (CREKA) peptide can deliver the platelet inhibitor dipyridamole (DIP) and the chemotherapeutic drug paclitaxel (PTX) to tumor tissues, thereby inhibiting tumor-associated platelet function while killing tumor cells. The drug-loaded nanoparticles PD/Pep1 inhibited platelet-tumor cell interactions, were effectively taken up by tumor cells, and underwent morphological transformation induced by alkaline phosphatase (ALP) to prolong the retention time of the drugs. After intravenous injection, PD/Pep1 can target tumors and inhibit tumor metastasis. Thus, this small molecule peptide nanoformulation provides a simple strategy for efficient drug delivery and shows promise as a novel cancer therapy platform.

PB0739 Study of a Low Anticoagulant Bovine Heparin as a Drug Capable of Disrupting Tumor Cell-Platelet Interaction and Preventing Hematogenous Metastasis

PB0739 Study of a Low Anticoagulant Bovine Heparin as a Drug Capable of Disrupting Tumor Cell-Platelet Interaction and Preventing Hematogenous Metastasis

The role of platelets in the regulation of tumor growth and metastasis: the mechanisms and targeted therapy.

Platelets are a class of pluripotent cells that, in addition to hemostasis and maintaining vascular endothelial integrity, are also involved in tumor growth and distant metastasis. The tumor microenvironment is a complex and comprehensive system composed of tumor cells and their surrounding immune and inflammatory cells, tumor-related fibroblasts, nearby interstitial tissues, microvessels, and various cytokines and chemokines. As an important member of the tumor microenvironment, platelets can promote tumor invasion and metastasis through various mechanisms. Understanding the role of platelets in tumor metastasis is important for diagnosing the risk of metastasis and prolonging survival. In this study, we more fully elucidate the underlying mechanisms by which platelets promote tumor growth and metastasis by modulating processes, such as immune escape, angiogenesis, tumor cell homing, and tumor cell exudation, and further summarize the effects of platelet-tumor cell interactions in the tumor microenvironment and possible tumor treatment strategies based on platelet studies. Our summary will more comprehensively and clearly demonstrate the role of platelets in tumor metastasis, so as to help clinical judgment of the potential risk of metastasis in cancer patients, with a view to improving the prognosis of patients.

Activated platelets facilitate hematogenous metastasis of breast cancer by modulating the PDGFR-β/COX-2 axis

Platelets have been widely recognized as a bona fide mediator of malignant diseases, and they play significant roles in influencing various aspects of tumor progression. Paracrine interactions between platelets and tumor cells have been implicated in promoting the dissemination of malignant cells to distant sites. However, the underlying mechanisms of the platelet-tumor cell interactions for promoting hematogenous metastasis are not yet fully understood. We found that activated platelets with high expression of CD36 were prone to release a plethora of growth factors and cytokines, including high levels of PDGF-B, compared to resting platelets. PDGF-B activated the PDGFR-β/COX-2 signaling cascade, which elevated an array of pro-inflammatory factors levels, thereby aggravating tumor metastasis. The collective administration of CD36 inhibitor and COX-2 inhibitor resolved the interactions between platelets and tumor cells. Collectively, our findings demonstrated that targeting the crosstalk between platelets and tumor cells offers potential therapeutic strategies for inhibiting tumor metastasis.

Liquid biopsy: an examination of platelet RNA obtained from head and neck squamous cell carcinoma patients for predictive molecular tumor markers.

Recently, a tumor cell-platelet interaction was identified in different tumor entities, resulting in a transfer of tumor-derived RNA into platelets, named further "tumor-educated platelets (TEP)". The present pilot study aims to investigate whether such a tumor-platelet transfer of RNA occurs also in patients suffering from head and neck squamous cell carcinoma (HNSCC). Sequencing analysis of RNA derived from platelets of tumor patients (TPs) and healthy donors (HDs) were performed. Subsequently, quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was used for verification of differentially expressed genes in platelets from TPs and HDs in a second cohort of patients and HDs. Data were analyzed by applying bioinformatic tools. Sequencing of RNA derived from the tumor as well as from platelets of TPs and HDs revealed 426 significantly differentially existing RNA, at which 406 RNA were more and 20 RNA less abundant in platelets from TPs in comparison to that of HDs. In TPs' platelets, abundantly existing RNA coding for 49 genes were detected, characteristically expressed in epithelial cells and RNA, the products of which are involved in tumor progression. Applying bioinformatic tools and verification on a second TP/HD cohort, collagen type I alpha 1 chain (COL1A1) and zinc finger protein 750 (ZNF750) were identified as the strongest potentially platelet-RNA-sequencing (RNA-seq)-based biomarkers for HNSCC. These results indicate a transfer of tumor-derived messenger RNA (mRNA) into platelets of HNSCC patients. Therefore, analyses of a patient's platelet RNA could be an efficient option for liquid biopsy in order to diagnose HNSCC or to monitor tumorigenesis as well as therapeutic responses at any time and in real time.

Microparticle Phosphatidylserine Mediates Coagulation: Involvement in Tumor Progression and Metastasis

Tumor progression and cancer metastasis has been linked to the release of microparticles (MPs), which are shed upon cell activation or apoptosis and display parental cell antigens, phospholipids such as phosphatidylserine (PS), and nucleic acids on their external surfaces. In this review, we highlight the biogenesis of MPs as well as the pathophysiological processes of PS externalization and its involvement in coagulation activation. We review the available evidence, suggesting that coagulation factors (mainly tissue factor, thrombin, and fibrin) assist in multiple steps of tumor dissemination, including epithelial-mesenchymal transition, extracellular matrix remodeling, immune escape, and tumor angiogenesis to support the formation of the pre-metastatic niche. Platelets are not just bystander cells in circulation but are functional players in primary tumor growth and metastasis. Tumor-induced platelet aggregation protects circulating tumor cells (CTCs) from the blood flow shear forces and immune cell attack while also promoting the binding of CTCs to endothelial cells and extravasation, which activates tumor invasion and sustains metastasis. Finally, in terms of therapy, lactadherin can inhibit coagulation by competing effectively with coagulation factors for PS binding sites and may similarly delay tumor progression. Furthermore, we also investigate the therapeutic potential of coagulation factor inhibitors within the context of cancer treatment. The development of multiple therapies targeting platelet activation and platelet-tumor cell interactions may not only reduce the lethal consequences of thrombosis but also impede tumor growth and spread.

Correction Notice: Microscopy and Plate Reader-based Methods for Monitoring the Interaction of Platelets and Tumor Cells in vitro.

Platelets and their activation status play an essential role in cancer metastasis. Therefore, the anti-metastatic potential of antiplatelet drugs has been investigated for many years. However, the initial screening of these antiplatelet drugs to determine which agents can inhibit the interactions of platelets and tumor cells is very limited due to reliance upon expensive, time-consuming, and low-throughput animal experiments for screening. In vitro models of the platelet-tumor cell interaction can be a useful tool to rapidly screen multiple antiplatelet drugs and compare their ability to disrupt platelet-tumor cell interactions, while also identifying optimal concentrations to move forward for in vivo validation. Hence, we adopted methods used in platelet activation research to isolate and label platelets before mixing them with tumor cells (MDA-MB-231-RFP cells) in vitro in a static co-culture model. Platelets were isolated from other blood components by centrifugation, followed by fluorescent labeling using the dye CMFDA (CellTrackerTM Green). Labeling platelets allows microscopic observation of the introduced platelets with tumor cells grown in cell culture dishes. These methods have facilitated the study of platelet-tumor cell interactions in tissue culture. Here, we provide details of the methods we have used for platelet isolation from humans and mice and their staining for further interaction with tumor cells by microscopy and plate reader-based quantification. Moreover, we show the utility of this assay by demonstrating decreased platelet-tumor cell interactions in the presence of the T-Prostanoid receptor (TPr) inhibitor ifetroban. The methods described here will aid in the rapid discovery of antiplatelet agents, which have potential as anti-metastatic agents as well. Key features • Analysis of platelet-tumor cell binding dynamics. • In vitro methods developed for measuring platelet-tumor cell binding to enable rapid testing of antiplatelet and other compounds. • Complementary analysis of platelet-tumor cell binding by imaging and fluorimetry-based readings. • Representative results screening the effect of the antiplatelet drug, ifetroban, on platelet-tumor cell binding using the protocol. • Validation results were presented with both a TPr agonist and ifetroban (antagonist).

Emerging roles of platelets in cancer biology and their potential as therapeutic targets.

The main role of platelets is to control bleeding and repair vascular damage via thrombosis. They have also been implicated to promote tumor metastasis through platelet-tumor cell interactions. Platelet-tumor cell interactions promote tumor cell survival and dissemination in blood circulation. Tumor cells are known to induce platelet activation and alter platelet RNA profiles. Liquid biopsies based on tumor-educated platelet biomarkers can detect tumors and correlate with prognosis, personalized therapy, treatment monitoring, and recurrence prediction. Platelet-based strategies for cancer prevention and tumor-targeted therapy include developing drugs that target platelet receptors, interfere with the release of platelet particles, inhibit platelet-specific enzymes, and utilize platelet-derived “nano-platelets” as a targeted drug delivery platform for tumor therapy. This review elaborates on platelet-tumor cell interactions and the molecular mechanisms and discusses future research directions for platelet-based liquid biopsy techniques and platelet-targeted anti-tumor strategies.

Abstract 259: Study of a low anticoagulant bovine heparin as a drug capable of disrupting tumor cell-platelet interaction and preventing hematogenous metastasis

Abstract Metastasis is the leading cause of death in cancer patients. During metastatic dissemination, circulating tumor cells need to survive in the bloodstream and their interaction with platelets through P-selectin-ligand seems to be crucial. It has been demonstrated that heparin (from porcine mucosa, porcine UFH), a glycosaminoglycan composed by repetitive disaccharides of uronic acid and glucosamine, may interfere with P-selectin interaction. Recently our research group purified by ion exchange chromatography a fraction of bovine heparin displaying very low anticoagulant potential, named LABH (~20 IU/mg LABH x ~200 IU/mg porcine UFH x ~100 IU/mg bovine UFH). The advantage of bovine UFH and, especially of LABH, is their reduced risk of bleeding side effect. Our aim in this work was to investigate the potential use of LABH as an antimetastatic agent in vitro and in vivo, evaluating its ability to interfere with tumor cell-platelet interaction, tumor cell binding to P-selectin and preventing induced metastasis in mice. For this, we challenged 8-12 weeks C57Bl/6 mice with 4 or 8 mg/kg of porcine UFH, bovine UFH or LABH followed by intravenous injection of B16F10 cells (murine melanoma cell line). After 21 days, lungs were analyzed and metastatic foci were counted. The number of metastatic foci was significantly reduced when animals were pretreated with heparins (50-70 foci in control mice and 10-15 in treated mice). In other attempt, isolated platelets from healthy volunteers were incubated for 1h with MV3 cells (human melanoma cell line) in vitro in the presence or absence of heparin. All three heparins tested were efficient in blocking MV3-platelet interaction in a dose-response manner, but LABH required higher doses than porcine and bovine UFH. When analyzing the direct binding of U937 cell (human lymphoma cell line) to immobilized P-selectin, we could observe that porcine and bovine UFH inhibited at the same level (~ 60% of inhibition with 100 μg/mL), while LABH was less effective (~ 45% of inhibition with 100 μg/mL). Collectively our results demonstrate that despite presenting distinct patterns of sulfation and anticoagulant potential, all heparins significantly reduced lung metastasis, platelet-tumor cell adhesion and P-selectin binding. On the other hand, we hypothesize that LABH may act suppressing metastasis also by other mechanisms since its effect on in vitro experiments was less pronounced in comparison to porcine and bovine UFH. Citation Format: Juliana Maria Motta, Carlos Roberto-Fernandes, Kayene Vitória Micheli, Ana Maria Tovar, Paulo Antônio Mourão, Mariana Sá Pereira. Study of a low anticoagulant bovine heparin as a drug capable of disrupting tumor cell-platelet interaction and preventing hematogenous metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 259.

Platelet-Mediated Protection of Cancer Cells From Immune Surveillance - Possible Implications for Cancer Immunotherapy.

The growing insights in the complex interactions between metastatic cancer-cells and platelets have revealed that platelet tumor cell interactions in the blood stream are an important factor supporting tumor metastasis. An increased coagulability of platelets facilitates the vascular evasion and establishment of solid tumor metastasis. Furthermore, platelets can support an immunosuppressive tumor microenvironment or shield tumor cells directly from engagement of cytotoxic lymphocytes as e.g., natural killer (NK) cells. Platelets are both in the tumor microenvironment and systemically the quantitatively most important source of TGF-β, which is a key cytokine for immunosuppression in the tumor microenvironment. If similar platelet-tumor interactions are of physiological relevance in hematological malignancies remains less well-studied. This might be important, as T- and NK cell mediated graft vs. leukemia effects (GvL) are well-documented and malignant hematological cells have a high exposure to platelets compared to solid tumors. As NK cell-based immunotherapies gain increasing attention as a therapeutic option for patients suffering from hematological and other malignancies, we review the known interactions between platelets and NK cells in the solid tumor setting and discuss how these could also apply to hematological cancers. We furthermore explore the possible implications for NK cell therapy in patients with solid tumors and patients who depend on frequent platelet transfusions. As platelets have a protective and supportive effect on cancer cells, the impact of platelet transfusion on immunotherapy and the combination of immunotherapy with platelet inhibitors needs to be evaluated.

Abstract LT011: Pharmacological blockade of platelet-CysLT1 receptor counteracts platelet protumoral action and prevents breast cancer cell metastasis to bone and lungs

Abstract Metastases are the main cause of death in cancer patients. However, few metastasis-specific targets have been exploited therapeutically. Blood platelets are well known to contribute to the poor survival of patients with advance cancers. Unfortunately, platelets are mandatory for human life due to their paramount function in hemostasis. In order to define new anti-metastasis therapies exhibiting a high specificity for the pathological tumor cell-platelet interactions without abrogating normal platelet functions we developed a high throughput assay that showed that pharmacological blockade of cysteinyl leukotriene receptor 1 (CysLT1) with two already FDA-approved drugs in asthma (Zarfirlukast and Montelukast), dose-dependently inhibited the mitogenic action of human platelets on human MDA-B02/Luc breast cancer cells. Both drugs had no impact on cell proliferation in presence of serum suggesting a specific alteration of platelet function. This effect was specific to CysLT1 as the CysLT2 inhibitor HAMI3379 remained inefficient even at high doses. All human breast cancer cells including MDA-B02/Luc cells used in this study did not express CysLT1 whereas platelets do suggesting that platelet-CysLT1 was the one contributing to the protumoral action of platelets. As described previously cysteinyl leukotriene D4 (LTD4), the strongest agonist of CysLT1, has no direct effect on platelet aggregation but instead potentiates the action of platelet agonists. We next injected MDA-B02/Luc cells into the tail artery of nude mice that received a daily treatment with Zafirlukast (0.4mg/kg per os). After 7 days bone marrow cells were collected and placed in culture in presence of puromycine for 14 day. After staining with crystal violet clones of tumor cells that colonized bone (TCB) were quantified. In these conditions Zafirlulast significantly inhibited by 90% the number of TCB. In order to confirm this anti-metastasis effect we used a syngenic animal model of spontaneous metastasis dissemination of murine 4T1 breast cancer cells after orthotopic xenograph in the mammary gland of BALB/c immunocompetent mice. Animals were treated with Zafirlukast (0.4mg/kg/day, i.p.), the common chemotherapeutic agent Paclitaxel (30mg/kg/2 days, i.p), or both drugs combined starting at day 3 post-tumor cell injections until sacrifice at day 12. Lungs were collected, minced, treated with collagenase and placed in culture for 14 days in presence of 6-Thioguanine. After staining with crystal violet clones of tumor cells that colonized the lungs (TCL) were quantified. In these conditions, the number of TCL was reduced by 88% with Zafirlulast compared with 60% with Paclitaxel. The combined treatment of Zafirlukast + Paclitaxel remarkably inhibited by 100% the number of TCL. In contrast, Zafirlukast alone or in combination with Paclitaxel had no significant effect on primary tumor growth. In conclusion we described for the first time that blockade of platelet-CysLT1 receptor altered the protumoral action of platelets and prevented breast cancer cell metastasis to bone and lungs. Citation Format: Lou Saier, Olivier Peyruchaud. Pharmacological blockade of platelet-CysLT1 receptor counteracts platelet protumoral action and prevents breast cancer cell metastasis to bone and lungs [abstract]. In: Proceedings of the AACR Virtual Special Conference on the Evolving Tumor Microenvironment in Cancer Progression: Mechanisms and Emerging Therapeutic Opportunities; in association with the Tumor Microenvironment (TME) Working Group; 2021 Jan 11-12. Philadelphia (PA): AACR; Cancer Res 2021;81(5 Suppl):Abstract nr LT011.

Platelet glycoprotein VI promotes metastasis through interaction with cancer cell–derived galectin-3

AbstractIncreasing evidence suggests that platelets play a predominant role in colon and breast cancer metastasis, but the underlying molecular mechanisms remain elusive. Glycoprotein VI (GPVI) is a platelet-specific receptor for collagen and fibrin that triggers platelet activation through immunoreceptor tyrosine-based activation motif (ITAM) signaling and thereby regulates diverse functions, including platelet adhesion, aggregation, and procoagulant activity. GPVI has been proposed as a safe antithrombotic target, because its inhibition is protective in models of arterial thrombosis, with only minor effects on hemostasis. In this study, the genetic deficiency of platelet GPVI in mice decreased experimental and spontaneous metastasis of colon and breast cancer cells. Similar results were obtained with mice lacking the spleen-tyrosine kinase Syk in platelets, an essential component of the ITAM-signaling cascade. In vitro and in vivo analyses supported that mouse, as well as human GPVI, had platelet adhesion to colon and breast cancer cells. Using a CRISPR/Cas9-based gene knockout approach, we identified galectin-3 as the major counterreceptor of GPVI on tumor cells. In vivo studies demonstrated that the interplay between platelet GPVI and tumor cell–expressed galectin-3 uses ITAM-signaling components in platelets and favors the extravasation of tumor cells. Finally, we showed that JAQ1 F(abʹ)2-mediated inhibition of GPVI efficiently impairs platelet–tumor cell interaction and tumor metastasis. Our study revealed a new mechanism by which platelets promote the metastasis of colon and breast cancer cells and suggests that GPVI represents a promising target for antimetastatic therapies.

Ticagrelor prevents tumor metastasis via inhibiting cell proliferation and promoting platelet apoptosis

Tumor cells can activate platelets, which in turn facilitate tumor cell survival and dissemination. Platelets inhibition or blocking platelet-tumor cell interactions has become a strategy to suppress tumor progression. In this study, we investigated the effect of ticagrelor, a new antiplatelet drug, on tumor cell proliferation and metastasis. Our results show that ticagrelor not only inhibits the proliferation, migration, and invasion of B16F10 and Lewis lung carcinoma cells but also induces platelet apoptosis. In addition, we find that apoptosis of the platelet cells is dose dependent. Further, the result of in-vivo experiments proved that ticagrelor treatment decreased the tumor metastasis. The results of this study demonstrate that ticagrelor may be a potential anti-tumor agent for tumor metastasis.

Blockade of Platelets Using Tumor-Specific NO-Releasing Nanoparticles Prevents Tumor Metastasis and Reverses Tumor Immunosuppression.

The tumor microenvironment maintains a sufficient immunosuppressive state owing to the existence of the immunosuppressive factors. The most prominent such factor is transforming growth factor β (TGF-β), which is mainly provided by platelets. Moreover, platelets have been shown to be the main accomplice in assisting tumor metastasis. Therefore, blocking tumor-associated platelets is endowed with functions of enhancing immunity and reducing metastasis. Herein, we designed a tumor microenvironment-responsive nitric oxide (NO) release nanoparticle, Ptx@AlbSNO, which was able to specifically and safely co-deliver the antiplatelet agent NO and the chemotherapeutic agent paclitaxel (Ptx) into tumor tissues and inhibit platelet-tumor cell interactions. We discovered that Ptx@AlbSNO could successfully block tumor-specific platelet functions, thereby suppressing the process of tumor epithelial-mesenchymal transition (EMT), preventing platelet adhesion around circulating tumor cells (CTCs) and reducing distant metastasis. In vivo studies demonstrate that the co-delivery of NO and Ptx can suppress primary tumor growth. With the ability to effectively inhibit activated platelets and TGF-β secretion in tumors, Ptx@AlbSNO can enhance intratumoral immune cell infiltration to reverse the immunosuppressive tumor microenvironment.

A mechanistic and empirical review of antcins, a new class of phytosterols of formosan fungi origin

Tumor cell-induced platelet aggregation (TCIPA) is a mechanism that involves the protection of tumor cells in the circulation and the promotion of tumor cell invasion and metastases. The C-type lectin-like receptor 2 (CLEC-2) that binds podoplanin (PDPN) is on the platelet surface and facilitates the TCIPA. Selective blockage of the PDPN-mediated platelet-tumor cell interaction is thereby a plausible strategy for inhibiting metastases. In a search for antagonists of PDPN- and tumor cell-induced platelet aggregation, traditional Chinese medicines were screened and it was found that the water extract of Artemisia argyi leaves selectively inhibited the PDPN-induced platelet aggregation. Bioactivity-guided fractionation analysis was performed for defining a polysaccharide-containing fraction (AAWAP) characterized by inhibition of PDPN activity and tumor cell-induced platelet aggregation. The pharmacological effects of AAWAP on PDPN-activated CLEC-2 signaling were determined by using Western blot and alpha screening analyses. AAWAP was non-toxic to the cells and platelets and it suppressed PDPN- and tumor cell-induced platelet aggregation by irreversibly blocking the interaction between PDPN and CLEC-2 in a dose-dependent manner. These findings indicate that AAWAP is an antagonist of the PDPN-CLEC-2 interaction. This action by AAWAP may result in the prevention of tumor cell metastases, and if so, could become an effective pharmacological agent in treating cancer patients. © 2019

Non-Anticoagulant Heparan Sulfate from the Ascidian Phallusia nigra Prevents Colon Carcinoma Metastasis in Mice by Disrupting Platelet-Tumor Cell Interaction

Although metastasis is the primary cause of death in patients with malignant solid tumors, efficient anti-metastatic therapies are not clinically available currently. Sulfated glycosaminoglycans from marine sources have shown promising pharmacological effects, acting on different steps of the metastatic process. Oversulfated dermatan sulfates from ascidians are effective in preventing metastasis by inhibition of P-selectin, a platelet surface protein involved in the platelet-tumor cell emboli formation. We report in this work that the heparan sulfate isolated from the viscera of the ascidian Phallusia nigra drastically attenuates metastases of colon carcinoma cells in mice. Our in vitro and in vivo assessments demonstrate that the P. nigra glycan has very low anticoagulant and antithrombotic activities and a reduced hypotension potential, although it efficiently prevented metastasis. Therefore, it may be a promising candidate for the development of a novel anti-metastatic drug.

Glycosaminoglycans as Tools to Decipher the Platelet Tumor Cell Interaction: A Focus on P-Selectin.

Tumor cell–platelet interactions are regarded as an initial crucial step in hematogenous metastasis. Platelets protect tumor cells from immune surveillance in the blood, mediate vascular arrest, facilitate tumor extravasation, growth, and finally angiogenesis in the metastatic foci. Tumor cells aggregate platelets in the bloodstream by activation of the plasmatic coagulation cascade and by direct contact formation. Antimetastatic activities of unfractionated or low molecular weight heparin (UFH/LMWH) can undoubtedly be related to attenuated platelet activation, but molecular mechanisms and contribution of contact formation vs. coagulation remain to be elucidated. Using a set of non-anticoagulant heparin derivatives varying in size or degree of sulfation as compared with UFH, we provide insight into the relevance of contact formation for platelet activation. Light transmission aggregometry and ATP release assays confirmed that only those heparin derivatives with P-selectin blocking capacities were able to attenuate breast cancer cell-induced platelet activation, while pentasaccharide fondaparinux was without effects. Furthermore, a role of P-selectin in platelet activation and signaling could be confirmed by proteome profiler arrays detecting platelet kinases. In this study, we demonstrate that heparin blocks tumor cell-induced coagulation. Moreover, we identify platelet P-selectin, which obviously acts as molecular switch and controls aggregation and secretion of procoagulant platelets.