Drug delivery using platelet cancer cell interaction

Platelets and their biomimetics for regenerative medicine and cancer therapies

Platelets, circulating blood cells derived from megakaryocytes, play a key role in various physical activities, including coagulation, hemostasis, the body's innate immune response, and cancer metastasis. By taking advantage of their key traits, researchers have developed strategies to exploit platelets and platelet-mimicking nanoassemblies to treat a number of conditions, including wounds, cancers, and bacterial infections. Compared to traditional polymer, lipsosome, and inorganic nanoparticles-based delivery systems, platelets and platelet-mimicking vehicles hold many advantages. Among these are their enhanced circulation time, their large volumes and surface areas for drug loading or conjugation, and their inherent ability to target some diseases. In this review, we will highlight the recent progress made in the development of disease-targeting platelets- and platelet-mimicking-vehicles as therapeutic platforms.

Platelet for drug delivery

Platelets play a vital physiological role in hemostasis, inflammation and tissue regeneration, which are associated with wound healing as well as cancer development and metastasis. These years, a variety of platelet-mediated drug delivery approaches have been developed due to their unique properties, such as quick replenishment and site-specific activation/adhesion. In this Current Opinion, focuses are put on strategies leveraging the physiological functions of platelets for the design of drug delivery systems, including platelet engineering, platelet hitchhiking, membrane coating, synthetic platelet fabrication and platelet-triggered drug release for different applications.

Platelet-mimicking nanoparticles co-loaded with W18O49 and metformin alleviate tumor hypoxia for enhanced photodynamic therapy and photothermal therapy

W₁₈O₄₉-mediated photodynamic therapy (PDT) and photothermal therapy (PTT) are limited by the easily oxidized property and tumor hypoxia. Here, we report the development of platelet membranes as nanocarriers to co-load W₁₈O₄₉ nanoparticles (NPs) and metformin (PM-W₁₈O₄₉-Met NPs). Platelet membranes can protect W₁₈O₄₉ from oxidation and immune evasion, and increase the accumulation of W₁₈O₄₉ in tumor sites via the passive EPR effect and active adhesion between platelets and cancer cells. The introduction of metformin (Met), a typical anti-diabetic drug, can alleviate the tumor hypoxia through reducing oxygen consumption. As a result, ROS and heat generation are both greatly increased, as revealed by ROS/hypoxia imaging in vitro, IR thermal imaging in vivo and PET imaging in vivo. PM-W₁₈O₄₉-Met NPs show the improved therapeutic effects with greatly inhibited tumor growth and induced tumor cell apoptosis. Therefore, our work provides a novel strategy for simultaneous enhanced PDT and PTT, which is promising in bioapplication. STATEMENTE OF SIGNIFICANCE: W₁₈O₄₉-mediated photodynamic therapy and photothermal therapy are limited by the poor delivery of nanoparticles to tumors, the easily oxidized property, and tumor hypoxia environment, which will induce tumor treatment failure. Herein, we report the development of platelet membranes as nanocarriers to co-load W₁₈O₄₉ nanoparticles and metformin (PM-W₁₈O₄₉-Met NPs). Platelet membranes can protect W₁₈O₄₉ from oxidation and immune evasion, and increase the accumulation of W₁₈O₄₉ in tumor sites via the passive EPR effect and active adhesion. Metformin can alleviate the tumor hypoxia through reducing oxygen consumption. Hence, ROS and heat generation are both greatly increased. PM-W₁₈O₄₉-Met NPs show the improved therapeutic effects with greatly inhibited tumor growth and induced apoptosis. Therefore, our work provides a novel strategy in bioapplication.

Therapeutics incorporating blood constituents

Blood deficiency and dysfunctionality can result in adverse events, which can primarily be treated by transfusion of blood or the re-introduction of properly functioning sub-components. Blood constituents can be engineered on the sub-cellular (i.e., DNA recombinant technology) and cellular level (i.e., cellular hitchhiking for drug delivery) for supplementing and enhancing therapeutic efficacy, in addition to rectifying dysfunctioning mechanisms (i.e., clotting). Herein, we report the progress of blood-based therapeutics, with an emphasis on recent applications of blood transfusion, blood cell-based therapies and biomimetic carriers. Clinically translated technologies and commercial products of blood-based therapeutics are subsequently highlighted and perspectives on challenges and future prospects are discussed.

STATEMENT OF SIGNIFICANCE

Blood-based therapeutics is a burgeoning field and has advanced considerably in recent years. Blood and its constituents, with and without modification (i.e., combinatorial), have been utilized in a broad spectrum of pre-clinical and clinically-translated treatments. This review article summarizes the most up-to-date progress of blood-based therapeutics in the following contexts: synthetic blood substitutes, acellular/non-recombinant therapies, cell-based therapies, and therapeutic sub-components. The article subsequently discusses clinically-translated technologies and future prospects thereof.

Human Cancer and Platelet Interaction, a Potential Therapeutic Target

Cancer patients experience a four-fold increase in thrombosis risk, indicating that cancer development and progression are associated with platelet activation. Xenograft experiments and transgenic mouse models further demonstrate that platelet activation and platelet-cancer cell interaction are crucial for cancer metastasis. Direct or indirect interaction of platelets induces cancer cell plasticity and enhances survival and extravasation of circulating cancer cells during dissemination. In vivo and in vitro experiments also demonstrate that cancer cells induce platelet aggregation, suggesting that platelet-cancer interaction is bidirectional. Therefore, understanding how platelets crosstalk with cancer cells may identify potential strategies to inhibit cancer metastasis and to reduce cancer-related thrombosis. Here, we discuss the potential function of platelets in regulating cancer progression and summarize the factors and signaling pathways that mediate the cancer cell-platelet interaction.

Cellular Cyborgs: On the Precipice of a Drug Delivery Revolution

Cell-based drug delivery systems offer the prospect of biocompatibility, large-loading capacity, long in vivo lifespan, and active targeting of diseased sites. However, these opportunities are offset by an array of challenges, including safeguarding the integrity of the drug cargo and the cellular host, as well as ensuring that drug release occurs at the appropriate time and place. Emerging strategies that address these, and related, issues, are described herein.

Platelet-targeted pharmacologic treatments as anti-cancer therapy

Platelets act as multifunctional cells participating in immune response, inflammation, allergy, tissue regeneration, and lymphoangiogenesis. Among the best-established aspects of a role of platelets in non-hemostatic or thrombotic disorders, there is their participation in cancer invasion and metastasis. The interaction of many different cancer cells with platelets leads to platelet activation, and on the other hand platelet activation is strongly instrumental to the pro-carcinogenic and pro-metastatic activities of platelets. It is thus obvious that over the last years a lot of interest has focused on the possible chemopreventive effect of platelet-targeted pharmacologic treatments. This article gives an overview of the platelet-targeted pharmacologic approaches that have been attempted in the prevention of cancer development, progression, and metastasis, including the application of anti-platelet drugs currently used for cardiovascular disease and of new and novel pharmacologic strategies. Despite the fact that very promising results have been obtained with some of these approaches in pre-clinical models, with the exclusion of aspirin, clinical evidence of a beneficial effect of anti-platelet agents in cancer is however still largely missing. Future studies with platelet-targeted drugs in cancer must carefully deal with design issues, and in particular with the careful selection of patients, and/or explore novel platelet targets in order to provide a solution to the critical issue of the risk/benefit profile of long-term anti-platelet therapy in the prevention of cancer progression and dissemination.

Towards the Manufacture of Megakaryocytes and Platelets for Clinical Application

Platelet transfusions are used in standard clinical practice to prevent hemorrhage in patients suffering from thrombocytopenia or platelet dysfunctions. Recently, a constant rise on the demand of platelets for transfusion has been registered. This may be associated with several factors including demographic changes, population aging as well as incidence and prevalence of hematological diseases. In addition, platelet-regenerative properties have been started to be exploited in different areas such as tissue remodeling and anti-cancer therapies. These new applications are also expected to increase the future demand on platelets. Thus, in vitro generated platelets may constitute a highly desirable alternative to meet the rising demand on platelets. Several factors have been considered in the road trip of producing in vitro megakaryocytes and platelets for clinical application. From selection of the cell source, differentiation protocols and culture conditions to the design of optimal bioreactors, several strategies have been proposed to maximize production yields while preserving functionality. This review summarizes new advances in megakaryocyte and platelet differentiation and their production upscaling.

Doxorubicin-loaded platelets conjugated with anti-CD22 mAbs: a novel targeted delivery system for lymphoma treatment with cardiopulmonary avoidance

B-cell lymphoma accounts for approximately 85% of all adult non-Hodgkin's lymphoma cases. Doxorubicin (DOX) is an indispensable drug for the treatment of non-Hodgkin's lymphoma. However, DOX causes severe cardiotoxicity, which limits its use in conventional treatment strategies. In this study, we developed a novel drug delivery system for lymphoma treatment: DOX-loaded platelets that were conjugated with anti-CD22 monoclonal antibodies (mAbs) (DOX-platelet-CD22). Platelets are bio- and immune-compatible drug carriers that can prolong the circulation time of drugs. Anti-CD22 mAb-labeled platelets can precisely deliver DOX to tumor cells. Our in vitro and in vivo experiments showed the enhanced antitumor activity and attenuated cardiotoxicity of DOX when delivered as DOX-platelet-CD22. Compared with other delivery systems, the uptake of DOX-platelet-CD22 by macrophage-like cells decreased. Moreover, DOX-platelet-CD22 showed platelet properties, such as tumor cell-induced platelet aggregation. Therefore, targeted chemotherapy that is mediated by DOX-platelet-CD22 is a promising option for lymphoma treatment.

Doxorubicin-loaded platelets as a smart drug delivery system: An improved therapy for lymphoma

Chemotherapy is majorly used for the treatment of many cancers, including lymphoma. However, cytotoxic drugs, utilized in chemotherapy, can induce various side effects on normal tissues because of their non-specific distribution in the body. Natural platelets are used as drug carriers because of their biocompatibility and specific targeting to vascular disorders, such as cancer, inflammation, and thrombosis. In this work, doxorubicin (DOX) was loaded in natural platelets for treatment of lymphoma. Results showed that DOX was loaded into platelets with high drug loading and encapsulation efficiency. DOX did not significantly induce morphological and functional changes in platelets. DOX-platelet facilitated intracellular drug accumulation through “tumor cell-induced platelet aggregation” and released DOX into the medium in a pH-controlled manner. This phenomenon reduced the adverse effects and enhanced the therapeutic efficacy. The growth inhibition of lymphoma Raji cells was enhanced, and the cardiotoxicity of DOX was reduced when DOX was loaded in platelets. DOX-platelet improved the anti-tumor activity of DOX by regulating the expression of apoptosis-related genes. Thus, platelets can serve as potential drug carriers to deliver DOX for clinical treatment of lymphoma.

Advances of blood cell-based drug delivery systems

Blood cells, including erythrocytes, leukocytes and platelets are used as drug carriers in a wide range of applications. They have many unique advantages such as long life-span in circulation (especially erythrocytes), target release capacities (especially platelets), and natural adhesive properties (leukocytes and platelets). These properties make blood cell based delivery systems, as well as their membrane-derived carriers, far superior to other drug delivery systems. Despite the advantages, the further development of blood cell-based delivery systems was hindered by limitations in the source, storage, and mass production. To overcome these problems, synthetic biomaterials that mimic blood cell and nanocrystallization of blood cells have been developed and may represent the future direction for blood cell membrane-based delivery systems. In this paper, we review recent progress of the rising blood cell-based drug delivery systems, and also discuss their challenges and future tendency of development.

Recent advancements in erythrocytes, platelets, and albumin as delivery systems

In the past few years, nanomaterial-based drug delivery systems have been applied to enhance the efficacy of therapeutics and to alleviate negative effects through the controlled delivery of targeting and releasing agents. However, few drug carriers can achieve high targeting efficacy, even when targeting modalities and surface markers are introduced. Immunological problems have also limited their wide applications. Biological drug delivery systems, such as erythrocytes, platelets, and albumin, have been extensively investigated because of their unique properties. In this review, erythrocytes, platelets, and albumin are described as efficient drug delivery systems. Their properties, applications, advantages, and limitations in disease treatment are explained. This review confirms that these systems can be used to facilitate a specific, biocompatible, and smart drug delivery.

Generation of HLA-Universal iPSC-Derived Megakaryocytes and Platelets for Survival Under Refractoriness Conditions

Platelet (PLT) transfusion is indispensable to maintain homeostasis in thrombocytopenic patients. However, PLT transfusion refractoriness is a common life-threatening condition observed in multitransfused patients. The most frequent immune cause for PLT transfusion refractoriness is the presence of alloantibodies specific for human leukocyte antigen (HLA) class I epitopes. Here, we have silenced the expression of HLA class I to generate a stable HLA-universal induced pluripotent stem cell (iPSC) line that can be used as a renewable cell source for the generation of low immunogenic cell products. The expression of HLA class I was silenced by up to 82% and remained stable during iPSC cultivation. In this study, we have focused on the generation of megakaryocytes (MK) and PLTs from a HLA-universal iPSC source under feeder- and xeno-free conditions. On d 19, differentiation rates of MKs and PLTs with means of 58% and 76% were observed, respectively. HLA-universal iPSC-derived MKs showed polyploidy with DNA contents higher than 4n and formed proPLTs. Importantly, differentiated MKs remained silenced for HLA class I expression. HLA-universal MKs produced functional PLTs. Notably, iPSC-derived HLA-universal MKs were capable to escape antibody-mediated complement- and cellular-dependent cytotoxicity. Furthermore, HLA-universal MKs were able to produce PLTs after in vivo transfusion in a mouse model indicating that they might be used as an alternative to PLT transfusion. Thus, in vitro produced low immunogenic MKs and PLTs may become an alternative to PLT donation in PLT-based therapies and an important component in the management of severe alloimmunized patients.

Smart blood cell and microvesicle-based Trojan horse drug delivery: Merging expertise in blood transfusion and biomedical engineering in the field of nanomedicine

Therapeutic and diagnostic applications of nanomedicine are playing increasingly important roles in human health. Various types of synthetic nanoparticles, including liposomes, micelles, and other nanotherapeutic platforms and conjugates, are being engineered to encapsulate or carry drugs for treating diseases such as cancer, cardiovascular disorders, neurodegeneration, and inflammations. Nanocarriers are designed to increase the half-life of drugs, decrease their toxicity and, ideally, target pathological sites. Developing smart carriers with the capacity to deliver drugs specifically to the microenvironment of diseased cells with minimum systemic toxicity is the goal. Blood cells, and potentially also the liposome-like micro- and nano-vesicles they generate, may be regarded as ideally suited to perform such specific targeting with minimum immunogenic risks. Blood cell membranes are "decorated" with complex physiological receptors capable of targeting and communicating with other cells and tissues and delivering their content to the surrounding pathological microenvironment. Blood cells, such as erythrocytes, have been developed as permeable carriers to release drugs to diseased tissues or act as biofactory allowing enzymatic degradation of a pathological substrate. Interestingly, attempts are also being made to improve the targeting capacity of synthetic nanoparticles by "decorating" their surface with blood cell membrane receptor-like biochemical structures. Research is needed to further explore the benefits that blood cell-derived microvesicles, as a Trojan horse delivery systems, can bring to the arsenal of therapeutic micro- and nanotechnologies. This short review focuses on the therapeutic roles that red blood cells and platelets can play as smart drug-delivery systems, and highlights the benefits that blood transfusion expertise can bring to this exciting and novel biomedical engineering field.

Myeloid-derived suppressor cells (MDSC) facilitate distant metastasis of malignancies by shielding circulating tumor cells (CTC) from immune surveillance

The mechanisms of distant metastasis of malignancies largely remain unknown. Circulating tumor cells (CTC) derived from the primary cancer initiate distant metastasis by entering and traversing the bloodstream. Current methods to detect CTC are based on the notion that CTC do not express the common leukocyte antigen CD45. However, these methods neglect the fact that CTC can directly adhere to platelets and immune cells and therefore appear to be CD45-positive. The potential effects of interactions between CTC and adhesive immune cells have been largely overlooked, despite the fact that most CTC are killed by immune effector cells and only those that evade immune surveillance result in clonal expansion and metastatic lesions. It is crucial to define the characteristics that allow a select CTC population to escape immune surveillance; particularly, it must be determined whether interactions between CTC and adhesive immune cells provide a protective effect on CTC survival. If interactions between CTC and adhesive immune cells offer a selective advantage to those CTC cells, the next consideration is which characteristics of a CTC-immune cell population allow sufficient protection to facilitate immune evasion. Myeloid-derived suppressor cells (MDSC) are a large heterogeneous population of immature myeloid cells that accumulate during cancer progression to induce extensively systemic and local immunosuppression, a phenomenon that has been demonstrated to facilitate cancer distant metastasis. We hypothesize, therefore, that CTC populations interacting with adhesive immune cells will have different biological behavior than CTC populations alone. Further, we hypothesize that CTC can create a defensive shield consisting of adhesive MDSC, which allows evasion of immune surveillance and therefore facilitates distant metastatic lesions. This possibility highlights the importance of direct interactions between CTC and adhesive immune cells and suggests the potential target that the CTC-MDSC cluster represents for prevention and treatment of distant metastasis of malignancies.

Microparticle of drug and nanoparticle: a biosynthetic route

Microparticles (MPs) have great potentiality in material science- based applications. Their use in biology is however limited to clinics and has rarely been exploited in the pharmaceutical context. Unlike nanoparticles (NPs), they are amenable to routine detection by flow cytometry and confocal microscopy. Though MPs can constitute a wide variety of materials, including ceramics, glass, polymers, and metals and can be synthesized by chemical process but wet processes for the preparation of microparticles have rarely been attemped. In this paper, a thrombotic route is shown to successfully generate biocompatible MP of a model anticancer drug (doxorubicin hydrochloride). Synthesis of MPs from platelets and drug loading in to these MPs was confirmed by flow cytometry and confocal microscopy. Human cervical cancer cell line (HeLa) was treated with these drug-loaded MPs to investigate whether the loaded MPs have the capacity to deliver drug to the cancer cells. In addition, Magnetic force microscopy was used to detect the preparation of MPs loaded with magnetic NPs. The efficiency of the drug-loaded MPs in inducing cytotoxicity in cancer cell line, shown to be significantly higher than the free drug itself. The drug-loaded MP is shown to have a much higher cytotoxic propensity than the free drug applied at comparable doses. The thrombotic approach can also be applied to synthesize MP containing NPs which in turn can lead to generate a wide variety of new biocompatible materials.

Platelets in cancer metastasis: To help the "villain" to do evil

Cancer progress is accompanied by platelet activation and thrombotic complications. Platelets are a dangerous alliance of cancer cells, and are a close engager in multiple processes of cancer metastasis. Platelet adhesion to cancer cells forms a protective cloak that helps cancer cells to escape immune surveillance and natural killer cell-mediated cytolysis. Platelets facilitate tethering and arrest of disseminated cancer cells in the vasculature, enhance invasive potentials and thus extravasation of cancer cells. Moreover, platelets recruit monocytes and granulocytes to the sites of cancer cell arrest, and collaborate with them to establish a pro-metastatic microenvironment and metastatic niches. Platelets also secret a number of growth factors to stimulate cancer cell proliferation, release various angiogenic regulators to regulate tumor angiogenesis and subsequently promote cancer growth and progress. Albeit platelets are helping the "villain" cancer to do evil, the close engagements of platelets in cancer metastasis and progress can be used as the intervention targets for new anti-cancer therapeutic developments. Platelet-targeted anti-cancer strategy may bring in novel anti-cancer treatments that can synergize the therapeutic effects of chemotherapies and surgical treatments of cancer.

Non-genetic engineering of cells for drug delivery and cell-based therapy

Cell-based therapy is a promising modality to address many unmet medical needs. In addition to genetic engineering, material-based, biochemical, and physical science-based approaches have emerged as novel approaches to modify cells. Non-genetic engineering of cells has been applied in delivering therapeutics to tissues, homing of cells to the bone marrow or inflammatory tissues, cancer imaging, immunotherapy, and remotely controlling cellular functions. This new strategy has unique advantages in disease therapy and is complementary to existing gene-based cell engineering approaches. A better understanding of cellular systems and different engineering methods will allow us to better exploit engineered cells in biomedicine. Here, we review non-genetic cell engineering techniques and applications of engineered cells, discuss the pros and cons of different methods, and provide our perspectives on future research directions.

Platelets in cancer. From basic research to therapeutic implications

Platelets are well-known for their major role in primary hemostasis and thrombosis. Cancer patients frequently manifest thrombotic events and present abnormalities in blood coagulation which appear to be linked to altered platelet function and turnover. Moreover, numerous studies indicate an intimate cross-talk between platelets and tumor growth, angiogenesis and metastatic dissemination. Finally, several experimental data and clinical trials suggest possible benefits of anti-platelet drugs on some cancers. Here, we will review the current state of basic biological research regarding the role of platelets in cancer progression. We also critically review the possible clinical applicability of some anti-platelet therapies to limit tumor growth and prevent metastatic dissemination.

Nanodiagnostics, nanopharmacology and nanotoxicology of platelet–vessel wall interactions

In physiological conditions, the interactions between blood platelets and endothelial cells play a major role in vascular reactivity and hemostasis. By contrast, increased platelet activation contributes to the pathogenesis of vascular pathology such as atherosclerosis, thrombosis, diabetes mellitus, hypertension and carcinogenesis. Nanomedicine, including nanodiagnostics and nanotherapeutics is poised to be used in the management of vascular diseases. However, the inherent risk and potential toxicity resultant from the use of nanosized (<100 nm) materials need to be carefully considered. This review, basing on a systematic search of literature provides state-of-the-art and focuses on new discoveries, as well as the potential benefits and threats in the field of nanodiagnostics, nanopharmacology and nanotoxicology of platelet–vessel wall interactions.

Co-opting biology to deliver drugs

The goal of drug delivery is to improve the safety and therapeutic efficacy of drugs. This review focuses on delivery platforms that are either derived from endogenous pathways, long-circulating biomolecules and cells or that piggyback onto long-circulating biomolecules and cells. The first class of such platforms is protein-based delivery systems--albumin, transferrin, and fusion to the Fc domain of antibodies--that have a long-circulation half-life and are designed to transport different molecules. The second class is lipid-based delivery systems-lipoproteins and exosomes-that are naturally occurring circulating lipid particles. The third class is cell-based delivery systems--erythrocytes, macrophages, and platelets--that have evolved, for reasons central to their function, to exhibit a long life-time in the body. The last class is small molecule-based delivery systems that include folic acid. This article reviews the biology of these systems, their application in drug delivery, and the promises and limitations of these endogenous systems for drug delivery.