Platelet microparticle-mediated transfer of miR-939 to epithelial ovarian cancer cells promotes epithelial to mesenchymal transition. Oncotarget. 2017;8:97464-97475. [PMID: 29228624 PMCID: PMC5722576 DOI: 10.18632/oncotarget.22136]

Unlocking the Intricacies: Exploring the Complex Interplay Between Platelets and Ovarian Cancer

Ovarian cancer, an aggressive malignancy of the female reproductive tract, is frequently linked to an elevated risk of thrombotic events. This association is manifested by a pronounced rise in platelet counts and activation levels. Current research firmly supports the pivotal role of platelets in the oncogenic processes of ovarian cancer, influencing tumor cell proliferation and metastasis. Platelets influence these processes through direct interactions with tumor cells or by secreting cytokines and growth factors that enhance tumor growth, angiogenesis, and metastasis. This review aims to thoroughly dissect the interactions between platelets and ovarian cancer cells, emphasizing their combined role in tumor progression and associated thrombotic events. Additionally, it summarizes therapeutic strategies targeting platelet-cancer interface which show significant promise. Such approaches could not only be effective in managing the primary ovarian tumor but also play a pivotal role in preventing metastasis and attenuating thrombotic complications associated with ovarian cancer.

miR-939, as an important regulator in various cancers pathogenesis, has diagnostic, prognostic, and therapeutic values: a review

BACKGROUND

MicroRNAs (miRNAs or miRs) are highly conserved non-coding RNAs with a short length (18-24 nucleotides) that directly bind to a complementary sequence within 3'-untranslated regions of their target mRNAs and regulate gene expression, post-transcriptionally. They play crucial roles in diverse biological processes, including cell proliferation, apoptosis, and differentiation. In the context of cancer, miRNAs are key regulators of growth, angiogenesis, metastasis, and drug resistance.

MAIN BODY

This review primarily focuses on miR-939 and its expanding roles and target genes in cancer pathogenesis. It compiles findings from various investigations. MiRNAs, due to their dysregulated expression in tumor environments, hold potential as cancer biomarkers. Several studies have highlighted the dysregulation of miR-939 expression in human cancers.

CONCLUSION

Our study highlights the potential of miR-939 as a valuable target in cancer diagnosis, prognosis, and treatment. The aberrant expression of miR-939, along with other miRNAs, underscores their significance in advancing our understanding of cancer biology and their promise in personalized cancer care.

TEP RNA: a new frontier for early diagnosis of NSCLC

BACKGROUND

Non-small cell lung cancer (NSCLC) is the most common type of lung cancer (LC), which is the leading cause of tumor mortality. In recent years, compared with tissue biopsy, which is the diagnostic gold standard for tumor diagnosis, Liquid biopsy (LB) is considered to be a more minimally invasive, sensitive, and safer alternative or auxiliary diagnostic method. However, the current value of LB in early diagnosis of LC is not ideal, so it is particularly important to study the changes in blood composition during the process of tumorigenesis and find more sensitive biomarkers.

PURPOSE

Platelets are a type of abundant blood cells that carry a large amount of RNA. In the LC regulatory network, activated platelets play an important role in the process of tumorigenesis, development, and metastasis. In order to identify predictive liquid biopsy biomarkers for the diagnosis of NSCLC, we summarized the development and function of platelets, the interaction between platelets and tumors, the value of TEP RNA in diagnosis, prognosis, and treatment of NSCLC, and the method for detecting TEP RNA of NSCLC in this article.

CONCLUSION

The application of platelets in the diagnosis and treatment of NSCLC remains at a nascent stage. In addition to the drawbacks of low platelet count and complex experimental processes, the diagnostic accuracy of TEP RNA-seq for cancer in different populations still needs to be improved and validated. At present, a large number of studies have confirmed significant differences in the expression of TEP RNA in platelets between NSCLC patients and healthy individuals. Continuous exploration of the diagnostic value of TEP RNA in NSCLC is of utmost importance. The integration of NSCLC platelet-related markers with other NSCLC markers can improve current tumor diagnosis and prognostic evaluation systems, providing broad prospects in tumor screening, disease monitoring, and prognosis assessment.

Dual targeting of H2S synthesizing enzymes; cystathionine β-synthase and cystathionine γ-lyase by miR-939-5p effectively curbs triple negative breast cancer

Introduction

Hydrogen sulfide (H2S) has been recently scrutinized for its critical role in aggravating breast cancer (BC) tumorigenicity. Several cancers aberrantly express H2S synthesizing enzymes; Cystathionine-β-synthase (CBS) and cystathionine-γ-lyase (CSE). However, their levels and interdependence in BC require further studies.

Objectives

Firstly, this study aimed to demonstrate a comparative expression profile of H2S synthesizing enzymes in BC vs normal tissue. Moreover, to investigate the reciprocal relationship between CBS and CSE and highlight the importance of dual targeting. Finally, to search for a valid dual repressor of the H2S synthesizing enzymes that could cease H2S production and reduce TNBC pathogenicity.

Methods

Pairwise analysis of tumor vs. normal tissues of 40 BC patients was carried out. The TNBC cell line MDA-MB-231 was transfected with oligonucleotides to study the H2S mediated molecular mechanisms. In silico screening was performed to identify dual regulator(s) for CBS and CSE. Gene expression analysis was performed using qRT-PCR and was confirmed on protein level using Western blot. TNBC hallmarks were evaluated using MTT, migration, and clonogenicity assays. H2S levels were detected using a AzMc fluorescent probe.

Results

BC tissues exhibited elevated levels of both CBS and CSE. Interestingly, upon CBS knockdown, CSE levels increased compensating for H2S production in TNBC cells, underlining the importance of dually targeting both enzymes in TNBC. In silico screening suggested miR-939-5p as a regulator of both CBS and CSE with high binding scores. Low expression levels of miR-939-5p were found in BC tissues, especially the aggressive subtypes. Ectopic expression of miR-939-5p significantly repressed CBS and CSE transcript and protein levels, diminished H2S production and attenuated TNBC hallmarks. Moreover, it improved the immune surveillance potency of TNBC cells through up regulating the NKG2D ligands, MICB and ULBP2 and reducing the immune suppressive cytokine IL-10.

Conclusion

This study sheds light on the reciprocal relationship between CBS and CSE and on the importance of their dual targeting, particularly in TNBC. It also postulates miR-939-5p as a potent dual repressor for CBS and CSE overcoming their redundancy in H2S production, a mechanism that can potentially attenuate TNBC oncogenicity and improves the immunogenic response.

The critical role of platelet in cancer progression and metastasis

Platelets play a crucial role in cancer blood metastasis. Various cancer-related factors such as Toll-like receptors (TLRs), adenosine diphosphate (ADP) or extracellular matrix (ECM) can activate these small particles that function in hemostasis and thrombosis. Moreover, platelets induce Epithelial Mesenchymal Transition (EMT) to promote cancer progression and invasiveness. The activated platelets protect circulating tumor cells from immune surveillance and anoikis. They also mediate tumor cell arrest, extravasation and angiogenesis in distant organs through direct or indirect modulation, creating a metastatic microenvironment. This review summarizes the recent advances and progress of mechanisms in platelet activation and its interaction with cancer cells in metastasis.

Shedding Light on the Cell Biology of Platelet-Derived Extracellular Vesicles and Their Biomedical Applications

EVs are membranous subcellular structures originating from various cells, including platelets which consist of biomolecules that can modify the target cell's pathophysiological functions including inflammation, cell communication, coagulation, and metastasis. EVs, which are known to allow the transmission of a wide range of molecules between cells, are gaining popularity in the fields of subcellular treatment, regenerative medicine, and drug delivery. PEVs are the most abundant EVs in circulation, being produced by platelet activation, and are considered to have a significant role in coagulation. PEV cargo is extremely diverse, containing lipids, proteins, nucleic acids, and organelles depending on the condition that induced their release and can regulate a wide range of biological activities. PEVs, unlike platelets, can overcome tissue barriers, allowing platelet-derived contents to be transferred to target cells and organs that platelets cannot reach. Their isolation, characterization, and therapeutic efficacy, on the other hand, are poorly understood. This review summarizes the technical elements of PEV isolation and characterization methods as well as the pathophysiological role of PEVs, including therapeutic potential and translational possibility in diverse disciplines.

Tumor educated platelet: the novel BioSource for cancer detection

Platelets, involved in the whole process of tumorigenesis and development, constantly absorb and enrich tumor-specific substances in the circulation during their life span, thus called "Tumor Educated Platelets" (TEPs). The alterations of platelet mRNA profiles have been identified as tumor markers due to the regulatory mechanism of post-transcriptional splicing. Small nuclear RNAs (SnRNAs), the important spliceosome components in platelets, dominate platelet RNA splicing and regulate the splicing intensity of pre-mRNA. Endogenous variation at the snRNA levels leads to widespread differences in alternative splicing, thereby driving the development and progression of neoplastic diseases. This review systematically expounds the bidirectional tumor-platelets interactions, especially the tumor induced alternative splicing in TEP, and further explores whether molecules related to alternative splicing such as snRNAs can serve as novel biomarkers for cancer diagnostics.

Research progress on the interaction between oxidative stress and platelets: Another avenue for cancer?

Oxidative stress (OS) is a chemical imbalance between an oxidant and an antioxidant, causing damage to redox signaling and control or causing molecular damage. Unbalanced oxidative metabolism can produce excessive reactive oxygen species (ROS). These excess ROS can cause drastic changes in platelet metabolism and further affect platelet function. It will also lead to an increase in platelet procoagulant phenotype and cell apoptosis, which will increase the risk of thrombosis. The creation of ROS and subsequent platelet activation, adhesion, and recruitment are then further encouraged in an auto-amplifying loop by ROS produced from platelets. Meanwhile, cancer cells produce a higher concentration of ROS due to their fast metabolism and high proliferation rate. However, excessive ROS can result in damage to and modification of cellular macromolecules. The formation of cancer and its progression is strongly associated with oxidative stress and the resulting oxidative damage. In addition, platelets are an important part of the tumor microenvironment, and there is a significant cross-communication between platelets and cancer cells. Cancer cells alter the activation status of platelets, their RNA spectrum, proteome, and other properties. The "cloaking" of cancer cells by platelets providing physical protection，avoiding destruction from shear stress and the attack of immune cells, promoting tumor cell invasion.We explored the vicious circle interaction between ROS, platelets, and cancer in this review, and we believe that ROS can play a stimulative role in tumor growth and metastasis through platelets.

The role of tumor-platelet interplay and micro tumor thrombi during hematogenous tumor metastasis

BACKGROUND

In addition to their pivotal roles in coagulation and thrombosis, platelets are crucial in tumor progression, with plenty of clinical and experimental data demonstrating that the interplay of platelets and tumor cells is essential for hematogenous tumor metastasis. After detach from primary sites, tumor cells intravasate into the blood circulation becoming circulating tumor cells and induce platelet activation, aggregation and encasement around tumor cells to form micro tumor thrombi, which create a permissive tumor microenvironment for metastasis. Platelets in micro tumor thrombi protect tumor cells from immune surveillance and anoikis (detachment-triggered apoptosis) through various pathways, which are significant for tumor cell survival in the bloodstream. Moreover, platelets can facilitate tumor metastasis by expediting epithelial-mesenchymal transition (EMT), adhesion to the endothelium, angiogenesis, tumor proliferation processes and platelet-derived microvesicle (PMV) formation.

CONCLUSIONS

Here, we provide a synopsis of the current understanding of the formation of micro tumor thrombi and the role of micro tumor thrombi in tumor hematogenous metastasis based on the tumor-platelet interplay. We also highlight potential therapeutic strategies targeting platelets for tumor treatment, including cancer-associated platelet-targeted nanomedicines.

Tumor-Educated Platelet Extracellular Vesicles: Proteomic Profiling and Crosstalk with Colorectal Cancer Cells

BACKGROUND

Platelet-cancer cell interactions modulate tumor metastasis and thrombosis in cancer. Platelet-derived extracellular vesicles (EVs) can contribute to these outcomes.

METHODS

We characterized the medium-sized EVs (mEVs) released by thrombin-stimulated platelets of colorectal cancer (CRC) patients and healthy subjects (HS) on the capacity to induce epithelial-mesenchymal transition (EMT)-related genes and cyclooxygenase (COX)-2(PTGS2), and thromboxane (TX)B₂ production in cocultures with four colorectal cancer cell lines. Platelet-derived mEVs were assessed for their size distribution and proteomics signature.

RESULTS

The mEV population released from thrombin-activated platelets of CRC patients had a different size distribution vs. HS. Platelet-derived mEVs from CRC patients, but not from HS, upregulated EMT marker genes, such as TWIST1 and VIM, and downregulated CDH1. PTGS2 was also upregulated. In cocultures of platelet-derived mEVs with cancer cells, TXB₂ generation was enhanced. The proteomics profile of mEVs released from activated platelets of CRC patients revealed that 119 proteins were downregulated and 89 upregulated vs. HS.

CONCLUSIONS

We show that mEVs released from thrombin-activated platelets of CRC patients have distinct features (size distribution and proteomics cargo) vs. HS and promote prometastatic and prothrombotic phenotypes in cancer cells. The analysis of platelet-derived mEVs from CRC patients could provide valuable information for developing an appropriate treatment plan.

A narrative review for platelets and their RNAs in cancers: New concepts and clinical perspectives

Recent years have witnessed a growing body of evidence suggesting that platelets are involved in several stages of the metastatic process via direct or indirect interactions with cancer cells, contributing to the progression of neoplastic malignancies. Cancer cells can dynamically exchange components with platelets in and out of blood vessels, and directly phagocytose platelets to hijack their proteome, transcriptome, and secretome, or be remotely regulated by metabolites or microparticles released by platelets, resulting in phenotypic, genetic, and functional modifications. Moreover, platelet interactions with stromal and immune cells in the tumor microenvironment lead to alterations in their components, including the ribonucleic acid (RNA) profile, and complicate the impact of platelets on cancers. A deeper understanding of the roles of platelets and their RNAs in cancer will contribute to the development of anticancer strategies and the optimization of clinical management. Encouragingly, advances in high-throughput sequencing, bioinformatics data analysis, and machine learning have allowed scientists to explore the potential of platelet RNAs for cancer diagnosis, prognosis, and guiding treatment. However, the clinical application of this technique remains controversial and requires larger, multicenter studies with standardized protocols. Here, we integrate the latest evidence to provide a broader insight into the role of platelets in cancer progression and management, and propose standardized recommendations for the clinical utility of platelet RNAs to facilitate translation and benefit patients.

Biology and pharmacology of platelet-type 12-lipoxygenase in platelets, cancer cells, and their crosstalk

Platelet-type lipoxygenase (pl12-LOX), encoded by ALOX12, catalyzes the production of the lipid mediator 12S-hydroperoxyeicosa-5,8,10,14-tetraenoic acid (12S-HpETE), which is quickly reduced by cellular peroxidases to form 12(S)-hydroxy-5,8,10,14-eicosatetraenoic acid (12S-HETE). Platelets express high levels of pl12-LOX and generate considerable amounts of 12S-HETE from arachidonic acid (AA; C20:4, n-6). The development of sensitive chiral liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods has allowed the accurate quantification of 12S-HETE in biological samples. Moreover, advances in the knowledge of the mechanism of action of 12S-HETE have been achieved. The orphan G-protein-coupled receptor 31 (GPR31) has been identified as the high-affinity 12S-HETE receptor. Moreover, upon platelet activation, 12S-HETE is produced, and significant amounts are found esterified to membrane phospholipids (PLs), such as phosphatidylethanolamine (PE) and phosphatidylcholine (PC), promoting thrombin generation. Platelets play many roles in cancer metastasis. Among them, the platelets' ability to interact with cancer cells and transfer platelet molecules by the release of extracellular vesicles (EVs) is noteworthy. Recently, it was found that platelets induce epithelial-mesenchymal transition(EMT) in cancer cells, a phenomenon known to confer high-grade malignancy, through the transfer of pl12-LOX contained in platelet-derived EVs. These cancer cells now generate 12-HETE, considered a key modulator of cancer metastasis. Interestingly, 12-HETE was mainly found esterified in plasmalogen phospholipids of cancer cells. This review summarizes the current knowledge on the regulation and functions of pl12-LOX in platelets and cancer cells and their crosstalk.Novel approaches to preventing cancer and metastasis by the pharmacological inhibition of pl12-LOX and the internalization of mEVs are discussed.

Extracellular vesicles and lipoproteins - Smart messengers of blood cells in the circulation

Blood cell-derived extracellular vesicles (BCEVs) and lipoproteins are the major circulating nanoparticles in blood that play an important role in intercellular communication. They have attracted significant interest for clinical applications, given their endogenous characteristics which make them stable, biocompatible, well tolerated, and capable of permeating biological barriers efficiently. In this review, we describe the basic characteristics of BCEVs and lipoproteins and summarize their implications in both physiological and pathological processes. We also outline well accepted workflows for the isolation and characterization of these circulating nanoparticles. Importantly, we highlight the latest progress and challenges associated with the use of circulating nanoparticles as diagnostic biomarkers and therapeutic interventions in multiple diseases. We spotlight novel engineering approaches and designs to facilitate the development of these nanoparticles by enhancing their stability, targeting capability, and delivery efficiency. Therefore, the present work provides a comprehensive overview of composition, biogenesis, functions, and clinical translation of circulating nanoparticles from the bench to the bedside.

Insights Into Platelet-Derived MicroRNAs in Cardiovascular and Oncologic Diseases: Potential Predictor and Therapeutic Target

Non-communicable diseases (NCDs), represented by cardiovascular diseases and cancer, have been the leading cause of death globally. Improvements in mortality from cardiovascular (CV) diseases (decrease of 14%/100,000, United States) or cancers (increase 7.5%/100,000, United States) seem unsatisfactory during the past two decades, and so the search for innovative and accurate biomarkers of early diagnosis and prevention, and novel treatment strategies is a valuable clinical and economic endeavor. Both tumors and cardiovascular system are rich in angiological systems that maintain material exchange, signal transduction and distant regulation. This pattern determines that they are strongly influenced by circulating substances, such as glycolipid metabolism, inflammatory homeostasis and cyclic non-coding RNA and so forth. Platelets, a group of small anucleated cells, inherit many mature proteins, mRNAs, and non-coding RNAs from their parent megakaryocytes during gradual formation and manifest important roles in inflammation, angiogenesis, atherosclerosis, stroke, myocardial infarction, diabetes, cancer, and many other diseases apart from its classical function in hemostasis. MicroRNAs (miRNAs) are a class of non-coding RNAs containing ∼22 nucleotides that participate in many key cellular processes by pairing with mRNAs at partially complementary binding sites for post-transcriptional regulation of gene expression. Platelets contain fully functional miRNA processors in their microvesicles and are able to transport their miRNAs to neighboring cells and regulate their gene expression. Therefore, the importance of platelet-derived miRNAs for the human health is of increasing interest. Here, we will elaborate systematically the roles of platelet-derived miRNAs in cardiovascular disease and cancer in the hope of providing clinicians with new ideas for early diagnosis and therapeutic strategies.

Platelet-Derived miR-126-3p Directly Targets AKT2 and Exerts Anti-Tumor Effects in Breast Cancer Cells: Further Insights in Platelet-Cancer Interplay

Among the surrounding cells influencing tumor biology, platelets are recognized as novel players as they release microvesicles (MVs) that, once delivered to cancer cells, modulate signaling pathways related to cell growth and dissemination. We have previously shown that physiological delivery of platelet MVs enriched in miR-126 exerted anti-tumor effects in different breast cancer (BC) cell lines. Here, we seek further insight by identifying AKT2 kinase as a novel miR-126-3p direct target, as assessed by bioinformatic analysis and validated by luciferase assay. Both ectopic expression and platelet MV-mediated delivery of miR-126-3p downregulated AKT2 expression, thus suppressing proliferating and invading properties, in either triple negative (BT549 cells) or less aggressive Luminal A (MCF-7 cells) BC subtypes. Accordingly, as shown by bioinformatic analysis, both high miR-126 and low AKT2 levels were associated with favorable long-term prognosis in BC patients. Our results, together with the literature data, indicate that miR-126-3p exerts suppressor activity by specifically targeting components of the PIK3/AKT signaling cascade. Therefore, management of platelet-derived MV production and selective delivery of miR-126-3p to tumor cells may represent a useful tool in multimodal therapeutic approaches in BC patients.

The transcription factor ZEB1 mediates the progression of epithelial ovarian cancer by promoting the transcription of CircANKRD17

Zinc finger E-box-binding homeobox 1 (ZEB1) is a key transcription factor that regulates the process of epithelial-mesenchymal transition (EMT) in various tumors. However, its role in epithelial ovarian cancer (EOC) is far from understood. The present study aimed to explore the role and potential mechanism of action of ZEB1 in EOC. A quantitative reverse transcription-polymerase chain reaction was used to detect ZEB1 expression levels. The Cell Counting Kit-8 assay, transwell assays, and flow cytometry were used to verify the effects of ZEB1 on the proliferation, invasion, migration, apoptosis, and EMT of EOC, respectively. RNA sequencing identified the effect of knocking down ZEB1 on circular RNAs in EOC cells. Dual-luciferase activity assay and chromatin immunoprecipitation experiments were used to verify the regulatory effect of ZEB1 on the circular RNA ANKRD17 (CircANKRD17; ID: hsa_circ_0007883) at the transcriptional level. Higher ZEB1 expression was found in EOC tissues and cells and was closely related to tumor metastasis, advanced stages, and lower survival rates. Furthermore, silencing ZEB1 inhibited the proliferation, invasion, migration, and EMT of EOC cells but enhanced cell apoptosis. Mechanistically, knockdown of ZEB1 resulted in the greatest downregulation of CircANKRD17 in EOC cells, and ZEB1 significantly promoted the expression of CircANKRD17 and had no significant effect on ANKRD17 messenger RNA expression. Further experiments verified that ZEB1 mediates the regulation of EOC processes by CircANKRD17. Highly expressed ZEB1 promoted proliferation, invasion, migration, and EMT while it inhibited cell apoptosis in EOC by promoting the transcription of CircANKRD17, providing a potential target for the treatment of EOC.

Microparticles: biogenesis, characteristics and intervention therapy for cancers in preclinical and clinical research

Extracellular vesicles (EVs), spherical biological vesicles, mainly contain nucleic acids, proteins, lipids and metabolites for biological information transfer between cells. Microparticles (MPs), a subtype of EVs, directly emerge from plasma membranes, and have gained interest in recent years. Specific cell stimulation conditions, such as ultraviolet and X-rays irradiation, can induce the release of MPs, which are endowed with unique antitumor functionalities, either for therapeutic vaccines or as direct antitumor agents. Moreover, the size of MPs (100–1000 nm) and their spherical structures surrounded by a lipid bilayer membrane allow MPs to function as delivery vectors for bioactive antitumor compounds, with favorable phamacokinetic behavior, immunostimulatory activity and biological function, without inherent carrier-specific toxic side effects. In this review, the mechanisms underlying MP biogenesis, factors that influence MP production, properties of MP membranes, size, composition and isolation methods of MPs are discussed. Additionally, the applications and mechanisms of action of MPs, as well as the main hurdles for their applications in cancer management, are introduced.

Pancreatic Cancer and Platelets Crosstalk: A Potential Biomarker and Target

Platelets have been recognized as key players in hemostasis, thrombosis, and cancer. Preclinical and clinical researches evidenced that tumorigenesis and metastasis can be promoted by platelets through a wide variety of crosstalk between cancer cells and platelets. Pancreatic cancer is a devastating disease with high morbidity and mortality worldwide. Although the relationship between pancreatic cancer and platelets in clinical diagnosis is described, the interplay between pancreatic cancer and platelets, the underlying pathological mechanism and pathways remain a matter of intensive study. This review summaries recent researches in connections between platelets and pancreatic cancer. The existing data showed different underlying mechanisms were involved in their complex crosstalk. Typically, pancreatic tumor accelerates platelet aggregation which forms thrombosis. Furthermore, extracellular vesicles released by platelets promote communication in a neoplastic microenvironment and illustrate how these interactions drive disease progression. We also discuss the advantages of novel model organoids in pancreatic cancer research. A more in-depth understanding of tumor and platelets crosstalk which is based on organoids and translational therapies may provide potential diagnostic and therapeutic strategies for pancreatic cancer progression.

Platelets induce free and phospholipid-esterified 12-hydroxyeicosatetraenoic acid generation in colon cancer cells by delivering 12-lipoxygenase

Platelets promote tumor metastasis by inducing promalignant phenotypes in cancer cells and directly contributing to cancer-related thrombotic complications. Platelet-derived extracellular vesicles (EVs) can promote epithelial-mesenchymal transition (EMT) in cancer cells, which confers high-grade malignancy. 12S-hydroxyeicosatetraenoic acid (12-HETE) generated by platelet-type 12-lipoxygenase (12-LOX) is considered a key modulator of cancer metastasis through unknown mechanisms. In platelets, 12-HETE can be esterified into plasma membrane phospholipids (PLs), which drive thrombosis. Using cocultures of human platelets and human colon adenocarcinoma cells (line HT29) and LC-MS/MS, we investigated the impact of platelets on cancer cell biosynthesis of 12S-HETE and its esterification into PLs and whether platelet ability to transfer its molecular cargo might play a role. To this aim, we performed coculture experiments with CFSE[5-(and-6)-carboxyfluorescein diacetate, succinimidyl ester]-loaded platelets. HT29 cells did not generate 12S-HETE or express 12-LOX. However, they acquired the capacity to produce 12S-HETE mainly esterified in plasmalogen phospholipid forms following the uptake of platelet-derived medium-sized EVs (mEVs) expressing 12-LOX. 12-LOX was detected in plasma mEV of patients with adenomas/adenocarcinomas, implying their potential to deliver the protein to cancer cells in vivo. In cancer cells exposed to platelets, endogenous but not exogenous 12S-HETE contributed to changes in EMT gene expression, mitigated by three structurally unrelated 12-LOX inhibitors. In conclusion, we showed that platelets induce the generation of primarily esterified 12-HETE in colon cancer cells following mEV-mediated delivery of 12-LOX. The modification of cancer cell phospholipids by 12-HETE may functionally impact cancer cell biology and represent a novel target for anticancer agent development.

Platelet-Cancer Interplay: Molecular Mechanisms and New Therapeutic Avenues

Although platelets are critically involved in thrombosis and hemostasis, experimental and clinical evidence indicate that platelets promote tumor progression and metastasis through a wide range of physical and functional interactions between platelets and cancer cells. Thrombotic and thromboembolic events are frequent complications in patients with solid tumors. Hence, cancer modulates platelet function by directly inducing platelet-tumor aggregates and triggering platelet granule release and altering platelet turnover. Also, platelets enhance tumor cell dissemination by activating endothelial cell function and recruiting immune cells to primary and metastatic tumor sites. In this review, we summarize current knowledge on the complex interactions between platelets and tumor cells and the host microenvironment. We also critically discuss the potential of anti-platelet agents for cancer prevention and treatment.

Platelet Microparticles Decrease Daunorubicin-Induced DNA Damage and Modulate Intrinsic Apoptosis in THP-1 Cells

Platelets can modulate cancer through budding of platelet microparticles (PMPs) that can transfer a plethora of bioactive molecules to cancer cells upon internalization. In acute myelogenous leukemia (AML) this can induce chemoresistance, partially through a decrease in cell activity. Here we investigated if the internalization of PMPs protected the monocytic AML cell line, THP-1, from apoptosis by decreasing the initial cellular damage inflicted by treatment with daunorubicin, or via direct modulation of the apoptotic response. We examined whether PMPs could protect against apoptosis after treatment with a selection of inducers, primarily associated with either the intrinsic or the extrinsic apoptotic pathway, and protection was restricted to the agents targeting intrinsic apoptosis. Furthermore, levels of daunorubicin-induced DNA damage, assessed by measuring gH2AX, were reduced in both 2N and 4N cells after PMP co-incubation. Measuring different BCL2-family proteins before and after treatment with daunorubicin revealed that PMPs downregulated the pro-apoptotic PUMA protein. Thus, our findings indicated that PMPs may protect AML cells against apoptosis by reducing DNA damage both dependent and independent of cell cycle phase, and via direct modulation of the intrinsic apoptotic pathway by downregulating PUMA. These findings further support the clinical relevance of platelets and PMPs in AML.

Horizontal MicroRNA Transfer by Platelets - Evidence and Implications

For decades, platelets have been known for their central role in hemostasis and their ability to release bioactive molecules, allowing inter-platelet communication and crosstalk with the immune system and vascular cells. However, with the detection of microRNAs in platelets and platelet-derived microvesicles (MVs), a new level of inter-cellular regulation was revealed. By shedding MVs from their plasma membrane, platelets are able to release functional microRNA complexes that are protected from plasma RNases. Upon contact with macrophages, endothelial cells and smooth muscle cells platelet microRNAs are rapidly internalized and fine-tune the functionality of the recipient cell by post-transcriptional reprogramming. Moreover, microRNA transfer by platelet MVs allows infiltration into tissues with limited cellular access such as solid tumors, thereby they not only modulate tumor progression but also provide a potential route for drug delivery. Understanding the precise mechanisms of horizontal transfer of platelet microRNAs under physiological and pathological conditions allows to design side-specific therapeutic (micro)RNA delivery systems. This review summarizes the current knowledge and the scientific evidence of horizontal microRNA transfer by platelets and platelet-derived MVs into vascular and non-vascular cells and its physiological consequences.

New Insights Into Platelet-enriched miRNAs: Production, Functions, Roles in Tumors, and Potential Targets for Tumor Diagnosis and Treatment

In view of the increasing number of malignant tumors worldwide and their high mortality, efforts are being made to find effective biomarkers for early detection and effective treatment measures of cancer. In recent years, the roles of platelets in tumors have attracted considerable attention. Although platelets do not have nuclei, they are rich in miRNAs, which are important molecules in platelet regulation of tumors. Platelet miRNA expression in tumor patients is abnormal and tumor-specific. Platelet miRNAs have higher accuracy and specificity than conventional tumor detection markers and circulating miRNAs in tumor diagnosis. Platelets enriched miRNAs are involved in the regulation of tumor proliferation, metastasis, tumor-related immunity, tumor-related thrombosis, and antitumor therapy. To understand the role of platelet miRNAs in tumors, this article reviews the biological functions of miRNAs in platelets and summarizes the regulatory roles of platelet miRNAs in tumors and the potential roles of platelet miRNAs in tumor diagnosis and treatment.

Platelet Microparticles Protect Acute Myelogenous Leukemia Cells against Daunorubicin-Induced Apoptosis

The role of platelets in cancer development and progression is increasingly evident, and several platelet-cancer interactions have been discovered, including the uptake of platelet microparticles (PMPs) by cancer cells. PMPs inherit a myriad of proteins and small RNAs from the parental platelets, which in turn can be transferred to cancer cells following internalization. However, the exact effect this may have in acute myelogenous leukemia (AML) is unknown. In this study, we sought to investigate whether PMPs could transfer their contents to the THP-1 cell line and if this could change the biological behavior of the recipient cells. Using acridine orange stained PMPs, we demonstrated that PMPs were internalized by THP-1 cells, which resulted in increased levels of miR-125a, miR-125b, and miR-199. In addition, co-incubation with PMPs protected THP-1 and primary AML cells against daunorubicin-induced cell death. We also showed that PMPs impaired cell growth, partially inhibited cell cycle progression, decreased mitochondrial membrane potential, and induced differentiation toward macrophages in THP-1 cells. Our results suggest that this altering of cell phenotype, in combination with decrease in cell activity may offer resistance to daunorubicin-induced apoptosis, as serum starvation also yielded a lower frequency of dead and apoptotic cells when treated with daunorubicin.

The Role of Platelet Cell Surface P-Selectin for the Direct Platelet-Tumor Cell Contact During Metastasis Formation in Human Tumors

Mammalian platelets, devoid of nuclei, are the smallest cells in the blood stream. They are essential for hemostasis, but also transmit cell signals that are necessary for regenerative and generative processes such as inflammation, immunity and tissue repair. In particular, in malignancies they are also associated with cell proliferation, angiogenesis, and epithelial-mesenchymal transition. Platelets promote metastasis and resistance to anti-tumor treatment. However, fundamental principles of the interaction between them and target cells within tumors are complex and still quite obscure. When injected into animals or circulating in the blood of cancer patients, cancer cells ligate platelets in a timely manner closely related to platelet activation either by direct contact or by cell-derived substances or microvesicles. In this context, a large number of different surface molecules and transduction mechanisms have been identified, although the results are sometimes species-specific and not always valid to humans. In this mini-review, we briefly summarize the current knowledge on the role of the direct and indirect platelet-tumor interaction for single steps of the metastatic cascade and specifically focus on the functional role of P-selectin.

LncRNA HEIH/miR-939-5p interplay modulates triple-negative breast cancer progression through NOS2-induced nitric oxide production

This study aimed to unravel the regulatory role of noncoding RNAs (ncRNA) on the nitric oxide (NO) machinery system in triple-negative breast cancer (TNBC) patients and to further assess the influence of NO-modulating ncRNAs on TNBC progression, immunogenic profile, and the tumor microenvironment (TME). The results revealed miR-939-5p and lncRNA HEIH as novel ncRNAs modulating NO machinery in TNBC. MiR-939-5p, an underexpressed microRNA (miRNA) in BC patients, showed an inhibitory effect on NOS2 and NOS3 transcript levels on TNBC cells. In contrast, HEIH was found to be markedly upregulated in TNBC patients and showed a modulatory role on miR-939-5p/NOS2/NO axis. Functionally, miR-939-5p was characterized as a tumor suppressor miRNA while HEIH was categorized as a novel oncogenic lncRNA in TNBC. Finally, knocking down of HEIH resulted in improvement of immunogenic profile of TNBC cells through inducing MICA/B and suppressing the immune checkpoint inhibitor PDL1. In the same context, knockdown of HEIH resulted in the alleviation of the immune-suppressive TME by repressing interleukin-10 and tumor necrosis factor-α levels. In conclusion, this study identifies miR-939-5p as a tumor suppressor miRNA while HEIH as an oncogenic lncRNA exhibiting its effect through miR-939-5p/NOS2/NO axis. Therefore, repressing BC hallmarks, improving TNBC immunogenic profile, and trimming TME.

Multifaceted Functions of Platelets in Cancer: From Tumorigenesis to Liquid Biopsy Tool and Drug Delivery System

Platelets contribute to several types of cancer through plenty of mechanisms. Upon activation, platelets release many molecules, including growth and angiogenic factors, lipids, and extracellular vesicles, and activate numerous cell types, including vascular and immune cells, fibroblasts, and cancer cells. Hence, platelets are a crucial component of cell-cell communication. In particular, their interaction with cancer cells can enhance their malignancy and facilitate the invasion and colonization of distant organs. These findings suggest the use of antiplatelet agents to restrain cancer development and progression. Another peculiarity of platelets is their capability to uptake proteins and transcripts from the circulation. Thus, cancer-patient platelets show specific proteomic and transcriptomic expression patterns, a phenomenon called tumor-educated platelets (TEP). The transcriptomic/proteomic profile of platelets can provide information for the early detection of cancer and disease monitoring. Platelet ability to interact with tumor cells and transfer their molecular cargo has been exploited to design platelet-mediated drug delivery systems to enhance the efficacy and reduce toxicity often associated with traditional chemotherapy. Platelets are extraordinary cells with many functions whose exploitation will improve cancer diagnosis and treatment.

Role of platelets and breast cancer stem cells in metastasis

The high mortality rate of breast cancer is mainly caused by the metastatic ability of cancer cells, resistance to chemotherapy and radiotherapy, and tumor regression capacity. In recent years, it has been shown that the presence of breast cancer stem cells is closely associated with the migration and metastatic ability of cancer cells, as well as with their resistance to chemotherapy and radiotherapy. The tumor microenvironment is one of the main molecular factors involved in cancer and metastatic processes development, in this sense it is interesting to study the role of platelets, one of the main communicator cells in the human body which are activated by the signals they receive from the microenvironment and can generate more than one response. Platelets can ingest and release RNA, proteins, cytokines and growth factors. After the platelets interact with the tumor microenvironment, they are called "tumor-educated platelets." Tumor-educated platelets transport material from the tumor microenvironment to sites adjacent to the tumor, thus helping to create microenvironments conducive for the development of primary and metastatic tumors. It has been observed that the clone capable of carrying out the metastatic process is a cancer cell with stem cell characteristics. Cancer stem cells go through a series of processes, including epithelial-mesenchymal transition, intravasation into blood vessels, movement through blood vessels, extravasation at the site of the establishment of a metastatic focus, and site colonization. Tumor-educated platelets support all these processes. 

Platelet Microparticle Controversial Role in Cancer

Platelet-derived microparticles (PMPs) are a group of micrometer-scale extracellular vesicles released by platelets upon activation that are responsible for the majority of microvesicles found in plasma. PMPs’ physiological properties and functions have long been investigated by researchers. In this regard, a noticeable area of studies has been devoted to evaluating the potential roles and effects of PMPs on cancer progression. Clinical and experimental evidence conflictingly implicates supportive and suppressive functions for PMPs regarding cancer. Many of these functions could be deemed as a cornerstone for future considerations of PMPs usage in cancer targeted therapy. This review discusses what is currently known about PMPs and provides insights for new and possible research directions for further grasping the intricate interplay between PMPs and cancer.

Platelets, Thrombocytosis, and Ovarian Cancer Prognosis: Surveying the Landscape of the Literature

Platelets are critical components of a number of physiologic processes, including tissue remodeling after injury, wound healing, and maintenance of vascular integrity. Increasing evidence suggests that platelets may also play important roles in cancer. In ovarian cancer, thrombocytosis, both at the time of initial diagnosis and at recurrence, has been associated with poorer prognosis. This review describes current evidence for associations between thrombocytosis and ovarian cancer prognosis and discusses the clinical relevance of platelet count thresholds and timing of assessment. In addition, we discuss several mechanisms from in vitro, in vivo, and clinical studies that may underlie these associations and recommend potential approaches for novel therapeutic targets for this lethal disease.

The Role of microRNAs in Epithelial Ovarian Cancer Metastasis

Epithelial ovarian cancer (EOC) is the deadliest gynecological cancer, and the major cause of death is mainly attributed to metastasis. MicroRNAs (miRNAs) are a group of small non-coding RNAs that exert important regulatory functions in many biological processes through their effects on regulating gene expression. In most cases, miRNAs interact with the 3′ UTRs of target mRNAs to induce their degradation and suppress their translation. Aberrant expression of miRNAs has been detected in EOC tumors and/or the biological fluids of EOC patients. Such dysregulation occurs as the result of alterations in DNA copy numbers, epigenetic regulation, and miRNA biogenesis. Many studies have demonstrated that miRNAs can promote or suppress events related to EOC metastasis, such as cell migration, invasion, epithelial-to-mesenchymal transition, and interaction with the tumor microenvironment. In this review, we provide a brief overview of miRNA biogenesis and highlight some key events and regulations related to EOC metastasis. We summarize current knowledge on how miRNAs are dysregulated, focusing on those that have been reported to regulate metastasis. Furthermore, we discuss the role of miRNAs in promoting and inhibiting EOC metastasis. Finally, we point out some limitations of current findings and suggest future research directions in the field.

Construction of circRNA-Associated ceRNA Network Reveals Novel Biomarkers for Esophageal Cancer

Objective

Esophageal cancer (ESCC) is reported to be the eighth most common malignant tumors worldwide with high mortality. However, the functions of majority circRNAs in ESCC requires to be further explored.

Methods

This study identified differently expressed circRNAs in 3 paired ESCC using RNA-sequencing method. The interactions among circRNAs, miRNAs, and mRNAs were predicted using bioinformatics analysis.

Results

In this study, using RNA-sequencing method and integrated bioinformatics analysis, 418 overexpressed circRNAs and 637 reduced circRNAs in ESCC sample were identified. Based on the mechanism that circRNAs could play as ceRNAs to modulate targets expression, circRNA-miRNA and circRNA-miRNA-mRNA networks were constructed in this study. Based on the network analysis, 7 circRNAs, including circ_0002255, circ_0000530, circ_0001904, circ_0001005, circ_0000513, circ_0000075, and circ_0001121, were identified as key circRNAs in ESCC. We found that circ_0002255 was related to the regulation of substrate adhesion-dependent cell spreading. circ_0001121 was involved in regulating nucleocytoplasmic transport. circ_0000513 played a key role in regulating Adherens junction, B cell receptor signaling pathway. Meanwhile, we observed circ_0000075 was involved in regulating zinc II ion transport, transition metal ion homeostasis, and angiogenesis.

Conclusion

We thought this study could provide novel biomarkers for the prognosis of ESCC.

Platelets Extracellular Vesicles as Regulators of Cancer Progression-An Updated Perspective

Extracellular vesicles (EVs) are a diverse group of membrane-bound structures secreted in physiological and pathological conditions by prokaryotic and eukaryotic cells. Their role in cell-to-cell communications has been discussed for more than two decades. More attention is paid to assess the impact of EVs in cancer. Numerous papers showed EVs as tumorigenesis regulators, by transferring their cargo molecules (miRNA, DNA, protein, cytokines, receptors, etc.) among cancer cells and cells in the tumor microenvironment. During platelet activation or apoptosis, platelet extracellular vesicles (PEVs) are formed. PEVs present a highly heterogeneous EVs population and are the most abundant EVs group in the circulatory system. The reason for the PEVs heterogeneity are their maternal activators, which is reflected on PEVs size and cargo. As PLTs role in cancer development is well-known, and PEVs are the most numerous EVs in blood, their feasible impact on cancer growth is strongly discussed. PEVs crosstalk could promote proliferation, change tumor microenvironment, favor metastasis formation. In many cases these functions were linked to the transfer into recipient cells specific cargo molecules from PEVs. The article reviews the PEVs biogenesis, cargo molecules, and their impact on the cancer progression.

A novel microRNA signature for pathological grading in lung adenocarcinoma based on TCGA and GEO data

Lung adenocarcinoma (LUAD) is one of the most common types of lung cancer and its poor prognosis largely depends on the tumor pathological stage. Critical roles of microRNAs (miRNAs) have been reported in the tumorigenesis and progression of lung cancer. However, whether the differential expression pattern of miRNAs could be used to distinguish early-stage (stage I) from mid-late-stage (stages II–IV) LUAD tumors is still unclear. In this study, clinical information and miRNA expression profiles of patients with LUAD were downloaded from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus databases. TCGA-LUAD (n=470) dataset was used for model training and validation, and the GSE62182 (n=94) and GSE83527 (n=36) datasets were used as external independent test datasets. The diagnostic model was created through miRNA feature selection followed by SVM classifier and was confirmed by 5-fold cross-validation. A receiver operating characteristic curve was calculated to evaluate the accuracy and robustness of the model. Using the DX score and LIBSVM tool, a 16-miRNA signature that could distinguish LUAD pathological stages was identified. The area under the curve rates were 0.62 [95% confidence interval (CI): 0.56–0.67], 0.66 (95% CI: 0.54–0.76) and 0.63 (95% CI: 0.43–0.82) in TCGA-LUAD internal validation dataset, the GSE62182 external validation dataset, and the GSE83527 external validation dataset, respectively. Kyoto Encyclopedia of Genes and Genomes and Gene Ontology enrichment analyses suggested that the target genes of the 16-miRNA signature were mainly involved in metabolic pathways. The present findings demonstrate that a 16-miRNA signature could serve as a promising diagnostic biomarker for pathological staging in LUAD.

The "Janus Face" of Platelets in Cancer

Besides their vital role in hemostasis and thrombosis, platelets are also recognized to be involved in cancer, where they play an unexpected central role: They actively influence cancer cell behavior, but, on the other hand, platelet physiology and phenotype are impacted by tumor cells. The existence of this platelet-cancer loop is supported by a large number of experimental and human studies reporting an association between alterations in platelet number and functions and cancer, often in a way dependent on patient, cancer type and treatment. Herein, we shall report on an update on platelet-cancer relationships, with a particular emphasis on how platelets might exert either a protective or a deleterious action in all steps of cancer progression. To this end, we will describe the impact of (i) platelet count, (ii) bioactive molecules secreted upon platelet activation, and (iii) microvesicle-derived miRNAs on cancer behavior. Potential explanations of conflicting results are also reported: Both intrinsic (heterogeneity in platelet-derived bioactive molecules with either inhibitory or stimulatory properties; features of cancer cell types, such as aggressiveness and/or tumour stage) and extrinsic (heterogeneous characteristics of cancer patients, study design and sample preparation) factors, together with other confounding elements, contribute to “the Janus face” of platelets in cancer. Given the difficulty to establish the univocal role of platelets in a tumor, a better understanding of their exact contribution is warranted, in order to identify an efficient therapeutic strategy for cancer management, as well as for better prevention, screening and risk assessment protocols.

miR-939-5p Contributes to the Migration and Invasion of Pancreatic Cancer by Targeting ARHGAP4

OBJECTIVE

Rho GTPase-activating protein 4 (ARHGAP4) is a GTPase-activating protein for the small GTPases of the Rho family that is involved in tumorigenesis. We recently reported that ARHGAP4 can mediate Warburg effect and malignant phenotype of pancreatic cancer. However, the regulation of ARHGAP4 remains unclear.

METHODS

ARHGAP4 and miR-939-5p expressions in pancreatic cancer tissues and cell lines were measured by real-time PCR or Western blotting. Pancreatic cancer cells were transfected with miR-939-5p inhibitor, miR-939-5p mimic and/or lentivirus expressing ARHGAP4, and the cell viability, invasion and migration were measured by CCK-8 and Transwell assay, respectively. The suppression of ARHGAP4 expression by miR-939-5p was revealed by luciferase reporter assay, real-time PCR or Western blotting.

RESULTS

ARHGAP4 expression was decreased, while miR-939-5p was increased in pancreatic cancer tissues compared with adjacent-normal pancreatic tissues. Higher miR-939-5p expression was correlated with advanced pathological stages and poor prognosis of pancreatic cancer patients. miR-939-5p directly targeted ARHGAP4. Either miR-939-5p down-regulation or ARHGAP4 overexpression inhibited viability, invasion and migration of pancreatic cancer cells. However, ARHGAP4 overexpression markedly inhibited the increased viability, migration, and invasion induced by miR-939-5p up-regulation in pancreatic cancer cells.

CONCLUSION

These observations suggested that miR-939-5p regulates the malignant phenotype of pancreatic cancer cells by targeting ARHGAP4, establishing miR-939-5p as a novel regulator of ARHGAP4 with a critical role in tumorigenesis in pancreatic cancer.

Delivery of platelet TPM3 mRNA into breast cancer cells via microvesicles enhances metastasis

Platelets are implicated in the pathophysiology of breast and other cancers through their role in exchanging biomolecules with tumor cells in the tumor microenvironment. Such exchange results in tumor‐educated platelets with altered RNA expression profiles. Multiple lines of evidence indicate that platelet RNA profiles may be suitable as diagnostic biomarkers for cancer‐related biological processes. In this study, we characterized the gene expression signatures of platelets in breast cancer (BC) by high‐throughput sequencing and quantitative real‐time RT‐PCR. Our results indicate that the expression of TPM3 (tropomyosin 3) mRNA is significantly elevated in platelets from patients with BC compared with age‐matched healthy control subjects. Furthermore, up‐regulation of TPM3 mRNA in platelets was found to be significantly correlated with metastasis in patients with BC. Finally, we report that platelet TPM3 mRNA is delivered into BC cells through microvesicles and leads to enhanced migrative phenotype of BC cells. In summary, our findings suggest that the transfer of platelet TPM3 mRNA into cancer cells via microvesicles promotes cancer cell migration, and thus platelet‐derived TPM3 mRNA may be a suitable biomarker for early diagnosis of metastatic BC.

Platelets are implicated in the pathophysiology of breast and other cancers through their role in exchanging biomolecules with tumor cells in the tumor microenvironment. In this study, we found that platelet TPM3 (tropomyosin 3) mRNA can be delivered into cancer cells via microvesicles to promote cancer cell migration. Platelet‐derived TPM3 mRNA may be a suitable biomarker for early diagnosis of metastatic breast cancer.

Polyunsaturated fatty acids modulate the delivery of platelet microvesicle-derived microRNAs into human breast cancer cell lines

Breast cancer is one of the most frequent and malignant types of cancer in women, with an increasing morbidity and mortality rate; in particular, treatment of triple negative breast cancer remains a challenge, since the efforts made with targeted therapies were ineffective. Among surrounding cells influencing the biology of cancer cells, platelets are recognizing as novel players. Activated platelets release microvesicles (MVs) that, once delivered to cancer cells, modulate signaling pathways related to cell growth and dissemination; among factors contained in platelet-derived MVs, microRNAs are highly involved in cancer development. The growing interest in ω3 and ω6 polyunsaturated fatty acids (PUFAs) as adjuvants in anti-cancer therapy prompted us to investigate the ability of arachidonic acid (AA) and docosahexaenoic acid (DHA) to modulate MV biological functions. AA induced differential enhancement of platelet-specific microRNAs (miR-223 and miR-126), an effect further enhanced by the presence of DHA. MVs can be delivered to and microRNAs internalized by breast cancer cells, although with different efficiency; analysis of kinetics of MV delivery, indeed, suggested that tumor cells fine-tune the uptake of specific microRNA. Finally, we demonstrated that physiological delivery of platelet miR-223 and miR-126 induced cellular effects in breast cancer cells, including cell cycle arrest, inhibition of migration and sensitivity to cisplatin. These results have been confirmed by exogenous expression of miR-223 and miR-126 through transient transfection experiments. Our preliminary data suggest that ω6/ω3-PUFA supplementation, by modulating microRNA delivery, enhances platelet anti-tumor activities, thus opening new avenues for add-on therapies in cancer patients.

Platelets and extracellular vesicles in cancer: diagnostic and therapeutic implications

Several pieces of evidence support the role of activated platelets in the development of the chronic inflammation-related diseases, such as atherothrombosis and cancer, mainly via the release of soluble factors and microparticles (MPs). Platelets and MPs contain a repertoire of proteins and genetic material (i.e., mRNAs and microRNAs) which may be influenced by the clinical condition of the individuals. In fact, platelets are capable of up-taking proteins and genetic material during their lifespan. Moreover, the content of platelet-derived MPs can be delivered to other cells, including stromal, immune, epithelial, and cancer cells, to change their phenotype and functions, thus contributing to cancer promotion and its metastasization. Platelets and MPs can play an indirect role in the metastatic process by helping malignant cells to escape from immunological surveillance. Furthermore, platelets and their derived MPs represent a potential source for blood biomarker development in oncology. This review provides an updated overview of the roles played by platelets and MPs in cancer and metastasis formation. The possible analysis of platelet and MP molecular signatures for the detection of cancer and monitoring of anticancer treatments is discussed. Finally, the potential use of MPs as vectors for drug delivery systems to cancer cells is put forward.

Platelets promote invasion and induce epithelial to mesenchymal transition in ovarian cancer cells by TGF-β signaling pathway

OBJECTIVE

To test whether platelets could increase invasion potential and initiate EMT in ovarian cancer cells via a TGF-β signaling pathway.

METHODS

Blood samples were collected in 69 patients with ovarian cancer, 16 patients with benign ovarian tumor and 64 healthy donors. SK-OV-3 and OVCAR-3 ovarian cancer cells were treated with platelets. Transwell assays were used to analyze the invasive capacity, and EMT was assessed by microarray analysis, quantitative real-time PCR (qPCR) and Western blotting. Activation of TGF-β pathway was examined by ELISA and Western blotting. TGF-β type I receptor (TβR I) inhibitor A83-01 was used to confirm the role of TGF-β pathway in vitro and in vivo.

RESULTS

Clinical data showed ovarian cancer patients with elevated platelet counts had a higher incidence of advanced stages. Treatment with platelets increased the invasive properties of both cell lines. Mesenchymal markers (snail family transcriptional repressor-1, vimentin, neural cadherin, fibronectin-1 and matrix metalloproteinase-2) were up-regulated in platelet-treated cells, while the epithelial marker (epithelial cadherin) was down-regulated. Higher TGF-β level was observed in patients with elevated platelet counts when compared to the subjects. Higher levels of TGF-β were also found in culture medium treated with platelets, and cells treated with platelets also showed increased phosphorylation of Smad2. TβR I inhibitor A83-01 reversed the EMT-like alterations and inhibited platelet-induced invasion in vitro and in vivo.

CONCLUSION

Platelet increased invasion potential and induced EMT in ovarian cancer cells in a TGF-β dependent pathway. Platelet-derived TGF-β may be useful as a new target treatment for ovarian cancer.

TANK-binding kinase 1 is a mediator of platelet-induced EMT in mammary carcinoma cells

Platelets can promote several stages of the metastatic process and thus contribute to malignant progression. As an example, platelets promote invasive properties of tumor cells by induction of epithelial to mesenchymal transition (EMT). In this study, we show that tumor necrosis factor receptor-associated factor (TRAF) family member-associated NF-κB activator (TANK)-binding kinase 1 (TBK1) is a previously unknown mediator of platelet-induced EMT in mammary carcinoma cells. Coculture of 2 mammary carcinoma cell lines, Ep5 from mice and MCF10A(MII) from humans, with isolated platelets induced morphologic as well as molecular changes characteristic of EMT, which was paralleled with activation of TBK1. TBK1 depletion using small interfering RNA impaired platelet-induced EMT in both Ep5 and MCF10A(MII) cells. Furthermore, platelet-induced activation of the NF-κB subunit p65 was suppressed after TBK1 knockdown, demonstrating that TBK1 mediates platelet-induced NF-κB signaling and EMT. Using an in vivo metastasis assay, we found that depletion of TBK1 from mammary carcinoma cells during in vitro preconditioning with platelets subsequently suppressed the formation of lung metastases in mice. Altogether, these results suggest that TBK1 contributes to tumor invasiveness and may be a driver of metastatic spread in breast cancer.-Zhang, Y., Unnithan, R. V. M., Hamidi, A., Caja, L., Saupe, F., Moustakas, A., Cedervall, J., Olsson, A.-K. TANK-binding kinase 1 is a mediator of platelet-induced EMT in mammary carcinoma cells.

Pathophysiology 2: The Role of Platelets in Cancer Biology

For over 100 years, a link has been recognized between thrombosis and cancer. However, whether this was a causal or correlational relationship was debated. It is now well established that cancer and thrombosis are mechanistically related in intricate ways and can directly fuel each other. Here, we present an historical perspective of platelets and how their physiological function in hemostasis can contribute to tumor development and metastasis. This emerging field has garnered great interest as aspirin therapy has been proposed as a prevention strategy for some malignancies. We highlight the advances that have been made, presenting platelets as a key component that supports many of the hallmarks of cancer that have been described and conclude with future directions and studies that are needed to clarify the role of platelets in cancer and solidify platelet modulating therapies within oncology.

Thrombosis and Hemostasis in Cancer. Scope of the Problem and Overview

"The frequent concurrence of phlegmasia alba dolens with an appreciable cancerous tumor, led me to the inquiry whether a relationship of cause and effect did not exist between the two, and whether the phlegmasia was not the consequence of the cancerous cachexia." (translated from the original French). This famous quote, delivered in a lecture by Armand Trousseau in 1865, is widely recognized as the initial and insightful understanding of the relationship of thrombosis and cancer.Although the association of thrombosis with cancer has been recognized for over 150 years, only recently has there been meaningful advances in our understanding of the relationship. Contemporary translational research tools have greatly enhanced our understanding the unique aspects of the pathophysiology of the relationship; how cancer cells exploit multiple aspects of the coagulation system for primary and metastatic growth leading, leading to an increased thrombotic risk. Further, there has been a growing appreciation of the complexity of the treatment of cancer-associated thrombosis. The superiority of low molecular weight heparin over warfarin, published in 2003, represented the first important divergence from the approach to management of thrombosis in the non-cancer population. With the introduction of the new generation of anticoagulants, the direct oral anticoagulants, there has been continued evolution of management guidelines.This text presents a much needed and comprehensive update of the field of thrombosis and hemostasis in cancer. We are fortunate to have so many leading authorities contribute their expertise and insight into this work. In the following chapters, the reader will find insight and guidance that will enhance scholarship, as well as patient care.

Platelets in cancer development and diagnosis

Platelets are involved in the development and progression of cancer through several mechanisms. Platelet activation at the site of tissue damage contributes to the initiation of a cascade of events which promote tumorigenesis. In fact, platelets release a wide array of proteins, including growth and angiogenic factors, lipids and extracellular vesicles rich in genetic material, which can mediate the induction of phenotypic changes in target cells, such as immune, stromal and tumor cells, and promote carcinogenesis and metastasis formation. Importantly, the role of platelets in tumor immune escape has been described. These lines of evidence open the way to novel strategies to fight cancer based on the use of antiplatelet agents. In addition to their ability to release factors, platelets are able of up-taking proteins and genetic material present in the bloodstream. Platelets are like 'sentinels' of the disease state. The evaluation of proteomics and transcriptomics signature of platelets and platelet-derived microparticles could represent a new strategy for the development of biomarkers for early cancer detection and/or therapeutic drug monitoring in cancer chemotherapy. Owing to the ability of platelets to interact with cancer cells and to deliver their cargo, platelets have been proposed as a 'biomimetic drug delivery system' for anti-tumor drugs to prevent the occurrence of off-target adverse events associated with the use of traditional chemotherapy.

Cancer metastasis versus stem cell homing: Role of platelets

One of the major obstacles in achieving a successful stem cell therapy is insufficient homing of transplanted cells. To overcome this obstacle, understanding the underlying mechanisms of stem cell homing is of obvious importance. Central to this review is the concept that cancer metastasis can be viewed as a role model to build up a comprehensive concept of stem cell homing. In this novel perspective, the prosurvival choices of the cancerous cells in the bloodstream, their arrest, extravasation, and proliferation at the secondary site can be exploited in favor of targeted stem cell homing. To date, tumor cells have been found to employ a wide variety of strategies to promote metastasis. One of these strategies is through their ability to activate platelets and subsequently activated platelets serve cancer cell survival and metastasis. Accordingly, in the first part of this review the roles of platelets in cancer metastasis as well as stem cell homing are discussed. Next, we provide some lessons learned from cancer metastasis in favor of developing strategies for improvement of stem cell homing with emphasis on the role of platelets. Based on direct or indirect evidence from metastasis, strategies such as manipulation of stem cells to enhance interaction with platelets, preconditioning-pretreatment of stem cells with platelets in vitro, and coinjection of both stem cells and platelets are proposed to improve stem cell homing.

Antithrombotic Agents and Cancer

Platelet activation is the first response to tissue damage and, if unrestrained, may promote chronic inflammation-related cancer, mainly through the release of soluble factors and vesicles that are rich in genetic materials and proteins. Platelets also sustain cancer cell invasion and metastasis formation by fostering the development of the epithelial-mesenchymal transition phenotype, cancer cell survival in the bloodstream and arrest/extravasation at the endothelium. Furthermore, platelets contribute to tumor escape from immune elimination. These findings provide the rationale for the use of antithrombotic agents in the prevention of cancer development and the reduction of metastatic spread and mortality. Among them, low-dose aspirin has been extensively evaluated in both preclinical and clinical studies. The lines of evidence have been considered appropriate to recommend the use of low-dose aspirin for primary prevention of cardiovascular disease and colorectal cancer by the USA. Preventive Services Task Force. However, two questions are still open: (i) the efficacy of aspirin as an anticancer agent shared by other antiplatelet agents, such as clopidogrel; (ii) the beneficial effect of aspirin improved at higher doses or by the co-administration of clopidogrel. This review discusses the latest updates regarding the mechanisms by which platelets promote cancer and the efficacy of antiplatelet agents.

A history of exploring cancer in context

The concept that progression of cancer is regulated by interactions of cancer cells with their microenvironment was postulated by Stephen Paget over a century ago. Contemporary tumour microenvironment (TME) research focuses on the identification of tumour-interacting microenvironmental constituents, such as resident or infiltrating non-tumour cells, soluble factors and extracellular matrix components, and the large variety of mechanisms by which these constituents regulate and shape the malignant phenotype of tumour cells. In this Timeline article, we review the developmental phases of the TME paradigm since its initial description. While illuminating controversies, we discuss the importance of interactions between various microenvironmental components and tumour cells and provide an overview and assessment of therapeutic opportunities and modalities by which the TME can be targeted.

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.

Platelet Metabolism and Other Targeted Drugs; Potential Impact on Immunotherapy

The role of platelets in cancer progression has been well recognized in the field of cancer biology. Emerging studies are elaborating further the additional roles and added extent that platelets play in promoting tumorigenesis. Platelets release factors that support tumor growth and also form heterotypic aggregates with tumor cells, which can provide an immune-evasive advantage. Their most critical role may be the inhibition of immune cell function that can negatively impact the body’s ability in preventing tumor establishment and growth. This review summarizes the importance of platelets in tumor progression, therapeutic response, survival, and finally the notion of immunotherapy modulation being likely to benefit from the inclusion of platelet inhibitors.