A combination of platelet features allows detection of early-stage cancer

Cancer progression and tumor hypercoagulability: a platelet perspective

Venous thromboembolism, which is common in cancer patients and accompanies or even precedes malignant tumors, is known as cancer-related thrombosis and is an important cause of cancer- associated death. At present, the exact etiology of the elevated incidence of venous thrombosis in cancer patients remains elusive. Platelets play a crucial role in blood coagulation, which is intimately linked to the development of arterial thrombosis. Additionally, platelets contribute to tumor progression and facilitate immune evasion by tumors. Tumor cells can interact with the coagulation system through various mechanisms, such as producing hemostatic proteins, activating platelets, and directly adhering to normal cells. The relationship between platelets and malignant tumors is also significant. In this review article, we will explore these connections.

The use of platelets as a clinical tool in oncology: opportunities and challenges

Platelets are small circulating anucleated cells mainly involved in thrombosis and hemostasis processes. Moreover, platelets play an active role in tumorigenesis and cancer progression, stimulating angiogenesis and vascular remodelling, and protecting circulating cancer cells from shear forces and immune surveillance. Several reports indicate that platelet number in the blood circulation of cancer patients is associated with prognosis and response to treatment. However, the mechanisms of platelets "education" by cancer cells and the crosstalk between platelets and tumor are still unclear, and the role of "tumor educated platelets" (TEPs) is achieving growing interest in cancer research. TEPs are a biological source of cancer-derived biomarkers, especially RNAs that are protected by platelets membrane from circulating RNases, and could serve as a non-invasive tool for tumor detection, molecular profiling and evolution during therapy in clinical practice. Moreover, short platelet lifespan offers the possibility to get a snapshot assessment of cancer molecular profile, providing a real-time tool. We review and discuss the potential and the clinical utility, in terms of cancer diagnosis and monitoring, of platelet count together with other morphological parameters and of the more recent and innovative TEP profiling.

Prospects of liquid biopsy in the prognosis and clinical management of gastrointestinal cancers

Gastrointestinal (GI) cancers account for one-fourth of the global cancer incidence and are incriminated to cause one-third of cancer-related deaths. GI cancer includes esophageal, gastric, liver, pancreatic, and colorectal cancers, mostly diagnosed at advanced stages due to a lack of accurate markers for early stages. The invasiveness of diagnostic methods like colonoscopy for solid biopsy reduces patient compliance as it cannot be frequently used to screen patients. Therefore, minimally invasive approaches like liquid biopsy may be explored for screening and early identification of gastrointestinal cancers. Liquid biopsy involves the qualitative and quantitative determination of certain cancer-specific biomarkers in body fluids such as blood, serum, saliva, and urine to predict disease progression, therapeutic tolerance, toxicities, and recurrence by evaluating minimal residual disease and its correlation with other clinical features. In this review, we deliberate upon various tumor-specific cellular and molecular entities such as circulating tumor cells (CTCs), tumor-educated platelets (TEPs), circulating tumor DNA (ctDNA), cell-free DNA (cfDNA), exosomes, and exosome-derived biomolecules and cite recent advances pertaining to their use in predicting disease progression, therapy response, or risk of relapse. We also discuss the technical challenges associated with translating liquid biopsy into clinical settings for various clinical applications in gastrointestinal cancers.

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.

The dynamic role of platelets in cancer progression and their therapeutic implications

Systemic antiplatelet treatment represents a promising option to improve the therapeutic outcomes and therapeutic efficacy of chemotherapy and immunotherapy due to the critical contribution of platelets to tumour progression. However, until recently, targeting platelets as a cancer therapeutic has been hampered by the elevated risk of haemorrhagic and thrombocytopenic (low platelet count) complications owing to the lack of specificity for tumour-associated platelets. Recent work has advanced our understanding of the molecular mechanisms responsible for the contribution of platelets to tumour progression and metastasis. This has led to the identification of the biological changes in platelets in the presence of tumours, the complex interactions between platelets and tumour cells during tumour progression, and the effects of platelets on antitumour therapeutic response. In this Review, we present a detailed picture of the dynamic roles of platelets in tumour development and progression as well as their use in diagnosis, prognosis and monitoring response to therapy. We also provide our view on how to overcome challenges faced by the development of precise antiplatelet strategies for safe and efficient clinical cancer therapy.

Modeling critical interaction for metastasis between circulating tumor cells (CTCs) and platelets adhered to the capillary wall

BACKGROUND AND OBJECTIVE

We used a 2D fluid-solid interaction (FSI) model to investigate the critical conditions for the arrest of the CTCs traveling through the narrowed capillary with a platelet attached to the capillary wall. This computational model allows us to determine the deformations and the progression of the passage of the CTC through different types of microvessels with platelet included.

METHODS

The modeling process is obtained using the strong coupling approach following the remeshing procedure. Also, the 1D FE rope element for simulating active ligand-receptor bonds is implemented in our computational tool (described below).

RESULTS

A relationship between the CTCs properties (size and stiffness), the platelet size and stiffness, and the ligand-receptor interaction intensity, on one side, and the time in contact between the CTCs and platelet and conditions for the cell arrest, on the other side, are determined. The model is further validated in vitro by using a microfluidic device with metastatic breast tumor cells.

CONCLUSIONS

The computational framework that is presented, with accompanying results, can be used as a powerful tool to study biomechanical conditions for CTCs arrest in interaction with platelets, giving a prognosis of disease progression.

Pancreatic Cancer-Secreted Proteins: Targeting Their Functions in Tumor Microenvironment

Pancreatic Ductal Adenocarcinoma (PDAC) is a ravaging disease with a poor prognosis, requiring a more detailed understanding of its biology to foster the development of effective therapies. The unsatisfactory results of treatments targeting cell proliferation and its related mechanisms suggest a shift in focus towards the inflammatory tumor microenvironment (TME). Here, we discuss the role of cancer-secreted proteins in the complex TME tumor-stroma crosstalk, shedding lights on druggable molecular targets for the development of innovative, safer and more efficient therapeutic strategies.

Superresolution Fluorescence Microscopy of Platelet Subcellular Structures as a Potential Tumor Liquid Biopsy

Blood-based tumor liquid biopsies are promising as an alternative or complement to tissue biopsies due to their noninvasiveness, convenience, and safety, and there is still a great demand for the discovery of new biomarkers for these biopsies. Here, nanoscale distribution patterns of subcellular structures in platelets, as imaged by structured illumination superresolution fluorescence microscopy, as a new type of potential biomarker for tumor liquid biopsies are presented. A standardized protocol for platelet sample preparation and developed an automated high-throughput image analysis workflow is established. The diagnostic capability based on the statistical analysis of 280 000 superresolution images of individual platelets from a variety of tumor patients, benign mass patients, and healthy volunteers (n = 206) is explored. These results suggest that the nanoscale distribution patterns of α-granules in platelets have the potential to be biomarkers for several cancers, including glioma and cervical, endometrial, and ovarian cancers, facilitating not only diagnosis but also therapeutic monitoring. This study provides a promising novel type of platelet parameter for tumor liquid biopsies at the subcellular level rather than the existing cellular or molecular level and opens up a new avenue for clinical applications of superresolution imaging techniques.

Emerging Role of Tumor-Educated Platelets as a New Liquid Biopsy Tool for Colorectal Cancer

Colorectal cancer (CRC) is a major cause of cancer-associated death universally. Currently, the diagnosis, prognosis, and treatment monitoring of CRC mostly depends on endoscopy integrated with tissue biopsy. Recently, liquid biopsy has gained more and more attention in the area of molecular detection and monitoring of tumors due to ease of sampling, and its safe, non-invasive, and dynamic nature. Platelets, despite their role in hemostasis and thrombosis, are known to have an active, bifacial relationship with cancers. Platelets are the second most common type of cell in the blood and are one of the wealthy liquid biopsy biosources. These cells have the potential to absorb nucleic acids and proteins and modify their transcriptome with regard to external signals, which are termed tumor-educated platelets (TEPs). Liquid biopsies depend on TEPs' biomarkers which can be used to screen and also detect cancer in terms of prognosis, personalized treatment, monitoring, and prediction of recurrence. The value of TEPs as an origin of tumor biomarkers is relatively new, but platelets are commonly isolated using formidable and rapid techniques in clinical practice. Numerous preclinical researches have emphasized the potential of platelets as a new liquid biopsy biosource for detecting several types of tumors. This review discusses the potential use of platelets as a liquid biopsy for CRC.

Tumor-educated platelet blood tests for Non-Small Cell Lung Cancer detection and management

Liquid biopsy approaches offer a promising technology for early and minimally invasive cancer detection. Tumor-educated platelets (TEPs) have emerged as a promising liquid biopsy biosource for the detection of various cancer types. In this study, we processed and analyzed the TEPs collected from 466 Non-small Cell Lung Carcinoma (NSCLC) patients and 410 asymptomatic individuals (controls) using the previously established thromboSeq protocol. We developed a novel particle-swarm optimization machine learning algorithm which enabled the selection of an 881 RNA biomarker panel (AUC 0.88). Herein we propose and validate in an independent cohort of samples (n = 558) two approaches for blood samples testing: one with high sensitivity (95% NSCLC detected) and another with high specificity (94% controls detected). Our data explain how TEP-derived spliced RNAs may serve as a biomarker for minimally-invasive clinical blood tests, complement existing imaging tests, and assist the detection and management of lung cancer patients.

Current Applications of Liquid Biopsy in Gastrointestinal Cancer Disease-From Early Cancer Detection to Individualized Cancer Treatment

Worldwide, gastrointestinal (GI) cancers account for a significant amount of cancer-related mortality. Tests that allow an early diagnosis could lead to an improvement in patient survival. Liquid biopsies (LBs) due to their non-invasive nature as well as low risk are the current focus of cancer research and could be a promising tool for early cancer detection. LB involves the sampling of any biological fluid (e.g., blood, urine, saliva) to enrich and analyze the tumor's biological material. LBs can detect tumor-associated components such as circulating tumor DNA (ctDNA), extracellular vesicles (EVs), and circulating tumor cells (CTCs). These components can reflect the status of the disease and can facilitate clinical decisions. LBs offer a unique and new way to assess cancers at all stages of treatment, from cancer screenings to prognosis to management of multidisciplinary therapies. In this review, we will provide insights into the current status of the various types of LBs enabling early detection and monitoring of GI cancers and their use in in vitro diagnostics.

Combinatorial Blood Platelets-Derived circRNA and mRNA Signature for Early-Stage Lung Cancer Detection

Despite the diversity of liquid biopsy transcriptomic repertoire, numerous studies often exploit only a single RNA type signature for diagnostic biomarker potential. This frequently results in insufficient sensitivity and specificity necessary to reach diagnostic utility. Combinatorial biomarker approaches may offer a more reliable diagnosis. Here, we investigated the synergistic contributions of circRNA and mRNA signatures derived from blood platelets as biomarkers for lung cancer detection. We developed a comprehensive bioinformatics pipeline permitting an analysis of platelet-circRNA and mRNA derived from non-cancer individuals and lung cancer patients. An optimal selected signature is then used to generate the predictive classification model using machine learning algorithm. Using an individual signature of 21 circRNA and 28 mRNA, the predictive models reached an area under the curve (AUC) of 0.88 and 0.81, respectively. Importantly, combinatorial analysis including both types of RNAs resulted in an 8-target signature (6 mRNA and 2 circRNA), enhancing the differentiation of lung cancer from controls (AUC of 0.92). Additionally, we identified five biomarkers potentially specific for early-stage detection of lung cancer. Our proof-of-concept study presents the first multi-analyte-based approach for the analysis of platelets-derived biomarkers, providing a potential combinatorial diagnostic signature for lung cancer detection.

Systemic inflammation with sarcopenia predicts survival in patients with gastric cancer

OBJECTIVE

The levels of platelet-related inflammation indicators and sarcopenia have been reported to affect the survival of patients with cancer. To evaluate the prognostic influence of platelet count (PLT), platelet lymphocyte ratio (PLR), and systemic immune inflammation index (SII), and SII combined with sarcopenia on the survival of patients with gastric cancer (GC).

METHODS

A total of 1133 patients with GC (812 male and 321 female, average age: 59.43 years) were evaluated. Receiver-operating characteristic curves were used to determine the best cutoff values of PLT, PLR, and SII, and univariate and multivariate Cox risk regression models were used to evaluate whether SII is an independent predictor of overall survival (OS). The prognostic SS (SII-sarcopenia) was established based on SII and sarcopenia. Finally, a comprehensive analysis of the prognostic SS was performed.

RESULTS

SII had the strongest prognostic effect. The SII and OS of patients with GC were in an inverted U-shape (adjusted HR = 1.07; 95% CI 0.97-1.19; adjusted P = 0.179). In patients with SII > 1800, SII was negatively correlated with OS (adjusted HR = 0.57; 95% CI 0.29-1.12; adjusted P = 0.102), however, there is no statistical difference. Interestingly, a high SS was associated with a poorer prognosis. The higher the SS score was, the worse the OS (P < 0.001).

CONCLUSION

SII is an independent prognostic indicator of GC, and high SII is related to poor prognosis. A higher SS score had worse survival. Thus, the prognostic SS is a reliable predictor of OS in patients with GC.

Contents in tumor-educated platelets as the novel biosource for cancer diagnostics

Liquid biopsy, a powerful non-invasive test, has been widely used in cancer diagnosis and treatment. Platelets, the second most abundant cells in peripheral blood, are becoming one of the richest sources of liquid biopsy with the capacity to systematically and locally respond to the presence of cancer and absorb and store circulating proteins and different types of nucleic acids, thus called "tumor-educated platelets (TEPs)". The contents of TEPs are significantly and specifically altered, empowering them with the potential as cancer biomarkers. The current review focuses on the alternation of TEP content, including coding and non-coding RNA and proteins, and their role in cancer diagnostics.

Application of tumor-educated platelets as new fluid biopsy markers in various tumors

The incidence of malignant tumors is increasing year by year. Early detection and diagnosis of malignant tumors can improve the prognosis of patients and prolong their life. Pathological biopsy is the current gold standard for diagnosis, but the results of pathological biopsy are affected by the sampling site and cannot fully reflect the nature of the disease. Moreover, the invasive nature of pathological biopsy limits repeated detection. Liquid biopsies are non-invasive and can be used for early detection and monitoring of tumors, which considered to represent a promising tool. Platelets make themselves to be one of the richest liquid biopsy sources by the capacity to take up proteins and nucleic acids and alter their megakaryocyte-derived transcripts and proteins in response to external signals, which are called tumor-educated platelets (TEPs). In this article, we will review the application of tumor-educated platelets in various malignancies (nasopharyngeal carcinoma, prostate cancer, lung cancer, glioblastoma, colorectal cancer, pancreas cancer, ovarian cancer, sarcoma, breast cancer and hepatocellular carcinoma) and provide theoretical basis for the research of TEPs in tumor diagnosis, monitoring and treatment.

Scoping Review on Platelets and Tumor Angiogenesis: Do We Need More Evidence or Better Analysis?

Platelets are an active component of the tumor microenvironment (TME), involved in the regulation of multiple tumor processes, including angiogenesis. They are generated rich in angiogenic factors in their granules to actively participate in the hemostatic process by megakaryocytes and further enriched in angiogenic factors by all components of the tumor microenvironment to control the angiogenic process because of their preferential relationship with the endothelial component of vessels. In recent decades, the literature has reported a great deal of evidence on the role of platelets in tumor angiogenesis; however, it is unclear whether the number or mean volume of platelets and/or their content and localization in TME may have clinical relevance in the choice and management of therapy for the cancer patient. In this scoping review, we collected and critically reviewed the scientific evidence supporting a close relationship between platelets, cancer, and angiogenesis. The aim of this work was to define the landscape of platelet-activated angiogenesis in cancer progression and analyze what and how much evidence is present in the last 20 years in the literature at both the preclinical and clinical levels, to answer whether platelets could be a useful determinant for analyzing tumor angiogenesis. In conclusion, this scoping review indicates that there is much evidence, both preclinical and clinical, but in the preclinical context, studies demonstrate the direct involvement of platelets in tumor angiogenesis; in the clinical context the evidence is indirect, though strong, and the indication of how and to what extent platelet content contributes to tumor angiogenesis is lacking. So, do we need more evidence or better analysis? More molecular and quali-quantitative data is needed to translate the results obtained in preclinical studies into the clinical setting. This information about platelets, if correlated with tumor type and its biology, including tumor vasculature, type of angiogenesis, and patient characteristics (age, sex, comorbidities, drug treatments for chronic diseases) could be an important pa- rameter for correlating platelet biology to angiogenesis, for personalizing cancer therapy, and for clinical prognosis.

Platelet detection as a new liquid biopsy tool for human cancers

Cancer is still a leading cause of death worldwide and liquid biopsy is a powerful tool that can be applied to different stages of cancer screening and treatment. However, as the second most abundant cell type in the bloodstream, platelets are isolated through well-established and fast methods in clinic but their value as a BioSource of cancer biomarkers is relatively recent. Many studies demonstrated the bidirectional interaction between cancer cells and platelets. Platelets transfer various proteins (e.g., growth factors, cytokine, chemokines) and RNAs (e.g., mRNA, lncRNA, miRNA, circRNA) into the tumor cells and microenvironment, leading the stimulation of tumor growth and metastasis. In turn, the platelet clinical characteristics (e.g., count and volume) and contents (e.g., RNA and protein) are altered by the interactions with cancer cells and this enables the early cancer detection using these features of platelets. In addition, platelet-derived microparticles also demonstrate the prediction power of being cancer biomarkers. In this review, we focus on the clinical applications of platelet detection using the platelet count, mean platelet volume, platelet RNA and protein profiles for human cancers and discuss the gap in bringing these implementations into the clinic.

Detection and localization of early- and late-stage cancers using platelet RNA

Cancer patients benefit from early tumor detection since treatment outcomes are more favorable for less advanced cancers. Platelets are involved in cancer progression and are considered a promising biosource for cancer detection, as they alter their RNA content upon local and systemic cues. We show that tumor-educated platelet (TEP) RNA-based blood tests enable the detection of 18 cancer types. With 99% specificity in asymptomatic controls, thromboSeq correctly detected the presence of cancer in two-thirds of 1,096 blood samples from stage I-IV cancer patients and in half of 352 stage I-III tumors. Symptomatic controls, including inflammatory and cardiovascular diseases, and benign tumors had increased false-positive test results with an average specificity of 78%. Moreover, thromboSeq determined the tumor site of origin in five different tumor types correctly in over 80% of the cancer patients. These results highlight the potential properties of TEP-derived RNA panels to supplement current approaches for blood-based cancer screening.

Preoperative Platelet Distribution Width Represents a Novel Prognostic Biomarker in Patients With Nonmetastatic Renal Cell Carcinoma: A Retrospective Clinical Analysis

Purpose

The study aimed to explore the prognostic value of platelet distribution width (PDW) in patients with nonmetastatic renal cell carcinoma (RCC).

Methods

We retrospective analyzed 706 patents with nonmetastatic RCC from January 2015 to December 2017. Clinicopathologic data and platelet indices were collected and analyzed by univariable and multivariable cox proportional hazard model. Progression-free survival (PFS) was analyzed using the Kaplan–Meier curve. Net reclassification improvement (NRI) and integrated discrimination improvement (IDI) were performed to evaluate the improvement of predictive accuracy.

Results

Patients were divided into low PDW (N = 241, PDW ≤11.7%), intermediate PDW (N = 232, 11.7%< PDW ≤15.6%), and high PDW (N = 233, PDW >15.6%) groups according to the tertiles. Patients with low PDW were associated with more symptoms at presentation, larger tumor size, higher AJCC tumor stage, and more sarcomatoid differentiation. Besides, patients with low PDW had significantly shorter PFS compared to intermediate PDW and high PDW groups. On the multivariable model, AJCC tumor stage, nuclear grade, and PDW (either continuous or categorical variables) were independent factors correlated with PFS. The NRI and IDI showed adding PDW to SSIGN score improves its predictive accuracy related to 2-, 3-, and 4-year PFS.

Conclusions

Low PDW was related to advanced clinicopathologic features and worse prognosis in patients with nonmetastatic RCC. Thus, PDW could serve as a novel biomarker for risk stratification in these patients when used pre-or postoperatively.

The Role of Circulating Biomarkers in Lung Cancer

Lung cancer is the leading cause of cancer morbidity and mortality worldwide and early diagnosis is crucial for the management and treatment of this disease. Non-invasive means of determining tumour information is an appealing diagnostic approach for lung cancers as often accessing and removing tumour tissue can be a limiting factor. In recent years, liquid biopsies have been developed to explore potential circulating tumour biomarkers which are considered reliable surrogates for understanding tumour biology in a non-invasive manner. Most common components assessed in liquid biopsy include circulating tumour cells (CTCs), cell-free DNA (cfDNA), circulating tumour DNA (ctDNA), microRNA and exosomes. This review explores the clinical use of circulating tumour biomarkers found in liquid biopsy for screening, early diagnosis and prognostication of lung cancer patients.

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.

Bidirectional Interaction Between Cancer Cells and Platelets Provides Potential Strategies for Cancer Therapies

Platelets are essential components in the tumor microenvironment. For decades, clinical data have demonstrated that cancer patients have a high risk of thrombosis that is associated with adverse prognosis and decreased survival, indicating the involvement of platelets in cancer progression. Increasing evidence confirms that cancer cells are able to induce production and activation of platelets. Once activated, platelets serve as allies of cancer cells in tumor growth and metastasis. They can protect circulating tumor cells (CTCs) against the immune system and detachment-induced apoptosis while facilitating angiogenesis and tumor cell adhesion and invasion. Therefore, antiplatelet agents and platelet-based therapies should be developed for cancer treatment. Here, we discuss the mechanisms underlying the bidirectional cancer-platelet crosstalk and platelet-based therapeutic approaches.

The Analysis of Platelet-Derived circRNA Repertoire as Potential Diagnostic Biomarker for Non-Small Cell Lung Cancer

Tumor-educated Platelets (TEPs) have emerged as rich biosources of cancer-related RNA profiles in liquid biopsies applicable for cancer detection. Although human blood platelets have been found to be enriched in circular RNA (circRNA), no studies have investigated the potential of circRNA as platelet-derived biomarkers for cancer. In this proof-of-concept study, we examine whether the circRNA signature of blood platelets can be used as a liquid biopsy biomarker for the detection of non-small cell lung cancer (NSCLC). We analyzed the total RNA, extracted from the platelet samples collected from NSCLC patients and asymptomatic individuals, using RNA sequencing (RNA-Seq). Identification and quantification of known and novel circRNAs were performed using the accurate CircRNA finder suite (ACFS), followed by the differential transcript expression analysis using a modified version of our thromboSeq software. Out of 4732 detected circRNAs, we identified 411 circRNAs that are significantly (p-value < 0.05) differentially expressed between asymptomatic individuals and NSCLC patients. Using the false discovery rate (FDR) of 0.05 as cutoff, we selected the nuclear receptor-interacting protein 1 (NRIP1) circRNA (circNRIP1) as a potential biomarker candidate for further validation by reverse transcription-quantitative PCR (RT-qPCR). This analysis was performed on an independent cohort of platelet samples. The RT-qPCR results confirmed the RNA-Seq data analysis, with significant downregulation of circNRIP1 in platelets derived from NSCLC patients. Our findings suggest that circRNAs found in blood platelets may hold diagnostic biomarkers potential for the detection of NSCLC using liquid biopsies.

Effects of Cancer Presence and Therapy on the Platelet Proteome

Platelets are involved in tumor angiogenesis and cancer progression. Previous studies indicated that cancer could affect platelet content. In the current study, we investigated whether cancer-associated proteins can be discerned in the platelets of cancer patients, and whether antitumor treatment may affect the platelet proteome. Platelets were isolated from nine patients with different cancer types and ten healthy volunteers. From three patients, platelets were isolated before and after the start of antitumor treatment. Mass spectrometry-based proteomics of gel-fractionated platelet proteins were used to compare patients versus controls and before and after treatment initiation. A total of 4059 proteins were detected, of which 50 were significantly more abundant in patients, and 36 more in healthy volunteers. Eight of these proteins overlapped with our previous cancer platelet proteomics study. From these data, we selected potential biomarkers of cancer including six upregulated proteins (RNF213, CTSG, PGLYRP1, RPL8, S100A8, S100A9) and two downregulated proteins (GPX1, TNS1). Antitumor treatment resulted in increased levels of 432 proteins and decreased levels of 189 proteins. In conclusion, the platelet proteome may be affected in cancer patients and platelets are a potential source of cancer biomarkers. In addition, we found in a small group of patients that anticancer treatment significantly changes the platelet proteome.

Tyrosine Kinase Inhibitor Sunitinib Delays Platelet-Induced Coagulation: Additive Effects of Aspirin

BACKGROUND

 Sunitinib is a multitarget tyrosine kinase inhibitor (TKI) used for cancer treatment. In platelets, sunitinib affects collagen-induced activation under noncoagulating conditions. We investigated (1) the effects of sunitinib on thrombus formation induced by other TK-dependent receptors, and (2) the effects under coagulating conditions. Cardiovascular disease is a comorbidity in cancer patients, resulting in possible aspirin treatment. Sunitinib and aspirin are associated with increased bleeding risk, and therefore we also investigated (3) the synergistic effects of these compounds on thrombus and fibrin formation.

METHODS

 Blood or isolated platelets from healthy volunteers or cancer patients were incubated with sunitinib and/or aspirin or vehicle. Platelet activation was determined by TK phosphorylation, flow cytometry, changes in [Ca²⁺]_i, aggregometry, and whole blood perfusion over multiple surfaces, including collagen with(out) tissue factor (TF) was performed.

RESULTS

 Sunitinib reduced thrombus formation and phosphatidylserine (PS) exposure under flow on collagen type I and III. Also, sunitinib inhibited glycoprotein VI-induced TK phosphorylation and Ca²⁺ elevation. Upon TF-triggered coagulation, sunitinib decreased PS exposure and fibrin formation. In blood from cancer patients more pronounced effects of sunitinib were observed in lung and pancreatic as compared to neuroglioblastoma and other cancer types. Compared to sunitinib alone, sunitinib plus aspirin further reduced platelet aggregation, thrombus formation, and PS exposure on collagen under flow with(out) coagulation.

CONCLUSION

 Sunitinib suppresses collagen-induced procoagulant activity and delays fibrin formation, which was aggravated by aspirin. Therefore, we urge for awareness of the combined antiplatelet effects of TKIs with aspirin, as this may result in increased risk of bleeding.

Platelets as messengers of early-stage cancer

Platelets have an important role in tumor angiogenesis, growth, and metastasis. The reciprocal interaction between cancer and platelets results in changes of several platelet characteristics. It is becoming clear that analysis of these platelet features could offer a new strategy in the search for biomarkers of cancer. Here, we review the human studies in which platelet characteristics (e.g., count, volume, protein, and mRNA content) are investigated in early-stage cancer. The main focus of this paper is to evaluate which platelet features are suitable for the development of a blood test that could detect cancer in its early stages.

Lessons to learn from tumor-educated platelets

Platelets have long been known to play important roles beyond hemostasis and thrombosis. Now recognized as a bona fide mediator of malignant disease, platelets influence various aspects of cancer progression, most notably tumor cell metastasis. Interestingly, platelets isolated from cancer patients often display distinct RNA and protein profiles, with no clear alterations in hemostatic activity. This phenotypically distinct population, termed tumor-educated platelets, now receive significant attention for their potential use as a readily available liquid biopsy for early cancer detection. Although the mechanisms underpinning platelet education are still being defined, direct uptake and storage of tumor-derived factors, signal-dependent changes in platelet RNA processing, and differential platelet production by tumor-educated megakaryocytes are the most prominent scenarios. This article aims to cover the various modalities of platelet education by tumors, in addition to assessing their diagnostic potential.

Circulating platelets as liquid biopsy sources for cancer detection

Nucleic acids and proteins are shed into the bloodstream by tumor cells and can be exploited as biomarkers for the detection of cancer. In addition, cancer detection biomarkers can also be nontumor‐derived, having their origin in other organs and cell types. Hence, liquid biopsies provide a source of direct tumor cell‐derived biomolecules and indirect nontumor‐derived surrogate markers that circulate in body fluids or are taken up by circulating peripheral blood cells. The capacity of platelets to take up proteins and nucleic acids and alter their megakaryocyte‐derived transcripts and proteins in response to external signals makes them one of the richest liquid biopsy biosources. Platelets are the second most abundant cell type in peripheral blood and are routinely isolated through well‐established and fast methods in clinical diagnostics but their value as a source of cancer biomarkers is relatively recent. Platelets do not have a nucleus but have a functional spliceosome and protein translation machinery, to process RNA transcripts. Platelets emerge as important repositories of potential cancer biomarkers, including several types of RNAs (mRNA, miRNA, circRNA, lncRNA, and mitochondrial RNA) and proteins, and several preclinical studies have highlighted their potential as a liquid biopsy source for detecting various types and stages of cancer. Here, we address the usability of platelets as a liquid biopsy for the detection of cancer. We describe several studies that support the use of platelet biomarkers in cancer diagnostics and discuss what is still lacking for their implementation into the clinic.

Integration of platelet features in blood and platelet rich plasma for detection of lung cancer

OBJECTIVES

To determine whether the integration platelet features in blood and platelet rich plasma can establish a model to diagnose lung cancer and colon cancer, even differentiate lung malignancy from lung benign diseases.

METHODS

245 individuals including 159 lung cancer and 86 normal participants were divided into the training cohort and testing cohort randomly. Then, 32 colon cancers, 37 lung cancers, and 21 benign patients were enrolled into validate cohort. The whole blood and corresponding platelet rich plasma (PRP) samples from all participants were prospectively collected, and the platelet features were determined. The features which are statistically significant at the univariate analysis in the training cohort and reported significant features were entered the diagnostic model. A receiver operator characteristic (ROC) curve was drawn to evaluate the accuracy of the model in each cohort.

RESULTS

In the training cohort, multiple platelet features were significantly different in lung cancer patients, including MPV in whole blood, MPV, and platelet count in PRP and platelet recovery rate (PRR). For the training cohort, the diagnostic model for lung cancer performed well (AUC = 0.92). The probability distribution of lung cancers and controls in testing cohort were also separated well by the diagnostic model (AUC = 0.79). The diagnostic model for colon cancer also performed well (AUC = 0.79). The model also has a potential value in differentiating the lung malignancy from the benign (AUC = 0.69).

CONCLUSION

The PRR was first raised and used in the detection of lung cancer. This study identified a diagnostic model based on PRR and other platelet features in whole blood and PRP samples with the potential to distinguish patients with lung cancer or colon cancer from healthy controls. The model could also be used to distinguish between lung cancer from the benign disease.

The aegis: platelets as biomarkers of tumor progression

There is increasing awareness that platelets play a significant role in creating a hypercoagulable environment that mediates tumor progression, beyond their classical hemostatic function. Platelets have heterogenic responses to agonists, and differential release and uptake of bioactive molecules may be manipulated via reciprocal cross-talk with cells of the tumor microenvironment. Platelets thus promote tumor progression by enhancing tumor growth, promoting the development of tumor-associated vasculature and encouraging invasion. In the metastatic process, platelets form the shield that protects tumor cells from high-velocity forces and immunosurveillance, while ensuring the establishment of the pre-metastatic niche. This review presents the complexity of these concepts, considering platelets as biomarkers for diagnosis, prognosis and potentially as therapeutic targets in cancer.

Platelets: the holy grail in cancer blood biomarker research?

We would like to promote the fact that platelets are increasingly emerging as a rich source of potential biomarkers for cancer. Blood platelets contain vast amounts of bioactive proteins, such as growth factors, chemokines, and cytokines. These proteins are either synthesized by the megakaryocytes that produce the platelets or are sequestered by the circulating platelets from the blood, in which case these proteins may originate from the tumor. Recent studies in patients have demonstrated that the presence of cancer influences multiple platelet characteristics (e.g., platelet count, volume, activation status, proteins, and RNA content). Interestingly, these changes happened already in early stages of the disease before metastasis had occurred. Additionally, exploiting these platelet alterations enabled discrimination of patients with early-stage cancer from healthy sex- and age-matched individuals. Therefore, we challenge clinicians and researchers to look beyond traditional fluid sources such as plasma or serum, and to take platelets and their content into account as they may become the holy grail in cancer blood biomarker research.

Exploring and validating the clinical risk factors for pancreatic cancer in chronic pancreatitis patients using electronic medical records datasets: three cohorts comprising 2,960 patients

Background

Patients with chronic pancreatitis (CP) have an increased risk of developing pancreatic cancer (PC). The purpose of this study was to identify predictors of PC in CP patients.

Methods

Electronic medical records (EMRs) of CP patients from two cohorts were collected, and a logistic regression analysis was performed to investigate the risk factors for PC. Subsequently, we validated the value of the risk prediction model with the EMRs of a third cohort.

Results

The derivation cohort consisted of 2,545 CP patients, and among them, 14 patients developed PC 7 years after CP diagnosis. Cyst of the pancreas [COP; odds ratio (OR): 4.37, 95% confidence interval (CI): 1.11 to 18.40, P=0.033], loss of weight (LW; OR: 3.21, 95% CI: 0.76 to 12.91, P=0.096) and high platelet (PLT) count (OR: 1.01 per 1 increment, 95% CI: 1.00 to 1.01, P=0.042) were independent risk factors for PC among CP patients. A risk prediction equation was constructed as follows: ln[p/(1–p)] = –6.68 + 1.55COP + 1.23LW + 0.0046PLT. The areas under the receiver operating characteristic (ROC) curve of our risk score were 0.83 and 0.72 in the derivation and validation cohorts, respectively. A score >0.0128 and >0.0122 had the best balance between sensitivity and specificity in the derivation and validation cohorts, respectively.

Conclusions

In CP patients, LW, COP and high PLT count were identified as novel predictors of PC. A risk prediction model based on these factors exhibited moderate predictive value for CP patients.

Platelet lysates in Hepatocellular Carcinoma patients after radiofrequency ablation facilitate tumor proliferation, invasion and vasculogenic mimicry

Background: Platelets play important roles in tumorigenesis, angiogenesis and metastatic dissemination of tumor cells. Radiofrequency ablation (RFA) could increase the circulating tumor cells in patients with primary or metastatic lung tumors. Whether platelet lysates in hepatocellular carcinoma (HCC) after RFA promote tumor progression has not been elaborated. Methods: HCC patients within Milan Criteria and without taking anti-platelet drugs were selected in the study. MTT assay, colony formation assay, transwell assay, tube formation and western blot were used to evaluate the effect of platelet lysates on HCC cells in vitro. Lung metastatic assay was performed in vivo. Results: Platelet lysates from patients after RFA promoted cell proliferation, colony formation, migration, invasion and vasculogenic mimicry in Hep3B and HCCLM3 cells compared with those from patients before RFA. Platelet lysates after RFA significantly increased the expression of p-Akt, p-Smad3 and snail, and decreased the expression of E-cadherin compared with those before RFA in Hep3B and HCCLM3 cells. Hep3B-Luc2-tdT cells incubation with platelet lysates from patients after RFA displayed enhanced lung metastasis compared with those before RFA. Conclusions: Platelet lysates from HCC patients after RFA promoted the proliferation, migration, invasion and vasculogenic mimicry of HCC cells, which indicated that RFA in combination with anti-platelet drug may be used to improve the prognosis of HCC.

Liquid Biopsy in Non-Small Cell Lung Cancer: Highlights and Challenges

Non-small cell lung cancer is one leading cause of death worldwide, and patients would greatly benefit from an early diagnosis. Since targeted and immunotherapies have emerged as novel approaches for more tailored treatments, repeated assessments of the tumor biology have become pivotal to drive clinical decisions. Currently, tumor tissue biopsy is the gold standard to investigate potentially actionable biomarkers, but this procedure is invasive and may prove inadequate to represent the whole malignancy. In this regard, liquid biopsy represents a minimally invasive and more comprehensive option for early detection and investigation of this tumor. Today, cell-free DNA is the only approved circulating marker to select patients for a targeted therapy. Conversely, the other tumor-derived markers (i.e., circulating tumor cells, miRNAs, exosomes, and tumor educated platelets) are still at a pre-clinical phase, although they show promising results for their application in screening programs or as prognostic/predictive biomarkers. The main challenges for their clinical translation are the lack of reliable cutoffs and, especially for miRNAs, the great variability among the studies. Moreover, no established tool has been approved for circulating tumor cells and exosome isolation. Finally, large prospective clinical trials are mandatory to provide evidence of their clinical utility.

TIMP1 mRNA in tumor-educated platelets is diagnostic biomarker for colorectal cancer

Platelets have been shown to promote the growth of tumors, including colorectal cancer. The RNA profile of tumor-educated platelets has the possibility for cancer diagnosis. We used RNA sequencing to identified the gene expression signature in platelets from colorectal cancer patients and healthy volunteers. We then verified the selected biomarkers from the RNA sequencing in a two-step case-control study using quantitative reverse-transcription polymerase chain reaction. We found that TIMP1 mRNA levels are higher in platelets from colorectal cancer patients than in platelets from healthy volunteers and patients with inflammatory bowel diseases. Additionally, TIMP1 mRNA expressed in platelets from colorectal cancer patients can be carried into colorectal cancer cells, where it promotes tumor growth in vivo and in vitro. These findings show that the TIMP1 mRNA in platelets is a potential independent diagnostic biomarker for colorectal cancer, and that platelets can carry RNAs into colorectal cancer cells to promote colorectal cancer development.

Platelets in myeloproliferative neoplasms have a distinct transcript signature in the presence of marrow fibrosis

Marrow fibrosis is a significant complication of myeloproliferative neoplasms (MPN) that affects up to 20% of patients and is associated with a poor prognosis. The pathological processes that lead to fibrotic progression are not well understood, but megakaryocytes have been implicated in the process. The aim of this study was to determine whether platelets, derived from megakaryocytes, have transcriptomic alterations associated with fibrosis. Platelets from MPN patients with and without fibrosis and non-malignant control individuals were assessed using next generation sequencing. Results from the initial training cohort showed discrete changes in platelet transcripts in the presence of marrow fibrosis. We identified more than 1000 differentially expressed transcripts from which a putative 3-gene fibrotic platelet signature (CCND1, H2AX [previously termed H2AFX] and CEP55) could be identified. This fibrosis-associated signature was assessed blinded on platelets from an independent test MPN patient cohort. The 3-gene signature was able to discriminate between patients with and without marrow fibrosis with a positive predictive value of 71% (93% specificity, 71% sensitivity). This demonstrates that assessment of dysregulated transcripts in platelets may be a useful monitoring tool in MPN to identify progression to marrow fibrosis. Further, sequential monitoring could have clinical applications for early prediction of progression to fibrosis.

Exploring the Extracellular Regulation of the Tumor Angiogenic Interaction Network Using a Systems Biology Model

Tumor angiogenesis is regulated by pro- and anti-angiogenic factors. Anti-angiogenic agents target the interconnected network of angiogenic factors to inhibit neovascularization, which subsequently impedes tumor growth. Due to the complexity of this network, optimizing anti-angiogenic cancer treatments requires detailed knowledge at a systems level. In this study, we constructed a tumor tissue-based model to better understand how the angiogenic network is regulated by opposing mediators at the extracellular level. We consider the network comprised of two pro-angiogenic factors: vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (FGF2), and two anti-angiogenic factors: thrombospondin-1 (TSP1) and platelet factor 4 (PF4). The model's prediction of angiogenic factors' distribution in tumor tissue reveals the localization of different factors and indicates the angiogenic state of the tumor. We explored how the distributions are affected by the secretion of the pro- and anti-angiogenic factors, illustrating how the angiogenic network is regulated in the extracellular space. Interestingly, we identified a counterintuitive result that the secretion of the anti-angiogenic factor PF4 can enhance pro-angiogenic signaling by elevating the levels of the interstitial and surface-level pro-angiogenic species. This counterintuitive situation is pertinent to the clinical setting, such as the release of anti-angiogenic factors in platelet activation or the administration of exogenous PF4 for anti-angiogenic therapy. Our study provides mechanistic insights into this counterintuitive result and highlights the role of heparan sulfate proteoglycans in regulating the interactions between angiogenic factors. This work complements previous studies aimed at understanding the formation of angiogenic complexes in tumor tissue and helps in the development of anti-cancer strategies targeting angiogenesis.

Super-resolution microscopy can identify specific protein distribution patterns in platelets incubated with cancer cells

Protein contents in platelets are frequently changed upon tumor development and metastasis. However, how cancer cells can influence protein-selective redistribution and release within platelets, thereby promoting tumor development, remains largely elusive. With fluorescence-based super-resolution stimulated emission depletion (STED) imaging we reveal how specific proteins, implicated in tumor progression and metastasis, re-distribute within platelets, when subject to soluble activators (thrombin, adenosine diphosphate and thromboxane A2), and when incubated with cancer (MCF-7, MDA-MB-231, EFO21) or non-cancer cells (184A1, MCF10A). Upon cancer cell incubation, the cell-adhesion protein P-selectin was found to re-distribute into circular nano-structures, consistent with accumulation into the membrane of protein-storing alpha-granules within the platelets. These changes were to a significantly lesser extent, if at all, found in platelets incubated with normal cells, or in platelets subject to soluble platelet activators. From these patterns, we developed a classification procedure, whereby platelets exposed to cancer cells, to non-cancer cells, soluble activators, as well as non-activated platelets all could be identified in an automatic, objective manner. We demonstrate that STED imaging, in contrast to electron and confocal microscopy, has the necessary spatial resolution and labelling efficiency to identify protein distribution patterns in platelets and can resolve how they specifically change upon different activations. Combined with image analyses of specific protein distribution patterns within the platelets, STED imaging can thus have a role in future platelet-based cancer diagnostics and therapeutic monitoring. The presented approach can also bring further clarity into fundamental mechanisms for cancer cell-platelet interactions, and into non-contact cell-to-cell interactions in general.

Prognostic Values of Platelet-Associated Indicators in Resectable Lung Cancers

Background:

Lung cancer is the leading cause of cancer death. Platelet-related indictors, including platelet count, plateletcrit, mean platelet volume, and platelet distribution width, not only associate with morphology and functions of platelet but also correlate with tumor development and metastasis. In the present study, we investigated the values of platelet-related indictors in the prognosis evaluation of resectable lung cancers.

Methods:

In total, 101 patients with resectable lung cancer were recruited in this study. Patients were divided into 2 groups according to the median pretreatment values. To evaluate the individual value changes after treatment, we introduced the concept of post-/pretreatment ratio (≤1 indicated value was not increased after treatment, while >1 suggested increased value).

Results:

The high pretreatment platelet count level was correlated with larger tumor size. High pretreatment plateletcrit level was associated with more lymph nodes metastasis. Patients with high pretreatment plateletcrit level had worse overall survival, whereas pretreatment platelet count, mean platelet volume, and platelet distribution width levels were not correlated with outcomes. Surgery had no impact on the values of platelet count, plateletcrit, mean platelet volume, or platelet distribution width. Adjuvant chemotherapy significantly decreased the values of platelet count and plateletcrit, whereas it had no effect on the values of mean platelet volume or platelet distribution width. Whole course of treatment (surgery combined with adjuvant chemotherapy) significantly decreased the values of platelet count and platelet distribution width, whereas it had no effect on the values of plateletcrit or mean platelet volume. Post-/pretreatment platelet count, plateletcrit, mean platelet volume, and platelet distribution width ratios were not correlated with outcomes. Univariate analyses demonstrated that American Joint Committee on Cancer stage and pretreatment plateletcrit level were significant risk factors for prognosis. Cox regression analysis revealed that no factor independently associated with worse survival.

Conclusion:

Pretreatment plateletcrit level could be a potential prognostic factor in resectable lung cancers.

Tumor-educated platelets

Liquid biopsies have been considered the holy grail in achieving effective cancer management, with blood tests offering a minimally invasive, safe, and sensitive alternative or complementary approach for tissue biopsies. Currently, blood-based liquid biopsy measurements focus on the evaluation of biomarker types, including circulating tumor DNA, circulating tumor cells, extracellular vesicles (exosomes and oncosomes), and tumor-educated platelets (TEPs). Despite the potential of individual techniques, each has its own advantages and disadvantages. Here, we provide further insight into TEPs.

Multifaceted role of cancer educated platelets in survival of cancer cells

Platelets, the derivatives of megakaryocytes, pose dynamic biological functions such as homeostasis and wound healing. The mechanisms involved in these processes are utilized by cancerous cells for proliferation and metastasis. Platelets through their activation establish an aggregate termed as Tumor cell induced platelet aggregation (TCIPA) that aids in establishing a niche for the primary tumor at secondary site while recruiting granulocytes and monocytes. The study of these close interactions between the tumor and the platelets can be exploited as biomarkers in liquid biopsy for early cancer detection, thereby increasing the life expectancy of cancer patients.

Preoperative monocyte-to-lymphocyte ratio predicts recurrence in gastrointestinal stromal tumors

BACKGROUND AND OBJECTIVES

Several inflammation markers were found to have a prognostic value in cancer. We investigated the significance of preoperative white cell ratios in determining gastrointestinal stromal tumors (GISTs) outcome.

METHODS

Clinicopathological features of patients who underwent surgery for GIST were reviewed. The following peripheral blood inflammation markers were calculated: neutrophil-lymphocyte ratio (NLR), monocyte-lymphocyte ratio (MLR), platelet-lymphocyte ratio (PLR), neutrophil-white blood cell ratio (NWR), lymphocyte-white cell ratio (LWR), monocyte-white cell ratio (MWR), and platelet-white cell ratio (PWR).

RESULTS

We analyzed 127 patients. Three- and five-year disease-free survival (DFS) were 89.7% and 86.9%, respectively. The univariate analysis selected tumor diameter (P = 0.003), gastric location ( P = 0.024), cell type ( P = 0.024), mitosis ( P < 0.001), MLR ( P = 0.014), NLR ( P = 0.016), and PLR ( P = 0.001) as the factors associated to DFS. The independent prognostic factors for DFS were mitosis ( P = 0.001), NLR ( P = 0.015), MLR ( P = 0.015), and PLR ( P = 0.031), with MLR showing the highest statistical significance and hazard ratio (HR) value. MLR, NLR, and PLR were the only prognostic factors in the subgroup of patients with moderate to high Miettinen's risk class. A high value of MLR was associated with reduced DFS.

CONCLUSION

MLR, NLR, and PLR are independent prognostic factors for DFS in GISTs. We first demonstrated the role of MLR as a predictor of recurrence in GIST. Its inclusion into clinical management may improve the recurrence estimation.

Dynamic platelet function is markedly different in patients with cancer compared to healthy donors

Despite a fivefold increased risk of thromboembolism in patients with cancer, the mechanism of arterial thromboembolism is poorly understood. To address this, we investigated platelet function in cancer patients and healthy controls using an assay that mimics the arterial vasculature. Blood samples from cancer patients (n = 36) and healthy controls (n = 22) were perfused through custom-made parallel-plate flow chambers coated with von Willebrand factor (VWF) under arterial shear (1,500 s^-1). Multiparameter measurements of platelet interactions with the immobilized VWF surface were recorded by digital-image microscopy and analyzed using custom-designed platelet-tracking software. Six measured parameters that characterize in detail the surface motion and surface binding of several hundred platelets per blood sample differed significantly in those with cancer from the healthy donors. In particular, it was found that patients with cancer had decreased numbers of platelets interacting, translocating and adhering to VWF. There were also reductions in the speed and distances that platelets traveled on VWF in comparison to healthy controls. Platelet function differed between those with early-stage cancer compared to those with later stage cancer. Patients with advanced cancer had an increased number of platelets stably adhering to VWF and greater platelet surface coverage after a given time of interaction. To the best of our knowledge, our results demonstrate for the first time that dynamic platelet function is markedly different in patients with cancer compared to healthy donors.

Acquired platelet antagonism: off-target antiplatelet effects of malignancy treatment with tyrosine kinase inhibitors

Platelets can contribute to tumor progression and metastasis. Cancer patients are at increased risk of thrombosis, and advanced stages of cancer are associated with thrombocytosis or increased platelet reactivity. Tyrosine kinase inhibitors (TKIs) are widely used as a targeted strategy for cancer treatment, with the aim of prolonging progression-free survival of the patients. Because of their broad kinase target spectrum, most TKIs inevitably have off-target effects. Platelets rely on tyrosine kinase activity for their activation. Frequently observed side effects are lowering of platelet count and inhibition of platelet functions, whether or not accompanied by an increased bleeding risk. In this review, we aim to give insights into: (i) 38 TKIs that are currently used for the treatment of different types of cancer, either on the market or in clinical trials; (ii) how distinct TKIs can inhibit activation mechanisms in platelets; and (iii) the clinical consequences of the antiplatelet effects of TKI treatment. For several TKIs, the knowledge on affinity for their targets does not align with the published effects on platelets and reported bleeding events. This review should raise awareness of the potential antiplatelet effects of several TKIs, which will be enhanced in the presence of antithrombotic drugs.

RNA sequencing enables systematic identification of platelet transcriptomic alterations in NSCLC patients

Platelets are implicated as key players in the metastatic dissemination of tumor cells. Previous evidence demonstrated platelets retained cytoplasmic RNAs with physiologically activity, splicing pre-mRNA to mRNA and translating into functional proteins in response to external stimulation. Recently, platelets gene profile of healthy or diseased individuals were characterized with the help of RNA sequencing (RNA-Seq) in some studies, leading to new insights into the mechanisms underlying disease pathogenesis. In this study, we performed RNA-seq in platelets from 7 healthy individuals and 15 non-small cell lung cancer (NSCLC) patients. Our data revealed a subset of near universal differently expressed gene (DEG) profiles in platelets of metastatic NSCLC compared to healthy individuals, including 626 up-regulated RNAs (mRNAs and ncRNAs) and 1497 down-regulated genes. The significant over-expressed genes showed enrichment in focal adhesion, platelets activation, gap junction and adherens junction pathways. The DEGs also included previously reported tumor-related genes such as PDGFR, VEGF, EGF, etc., verifying the consistence and significance of platelet RNA-Seq in oncology study. We also validated several up-regulated DEGs involved in tumor cell-induced platelet aggregation (TCIPA) and tumorigenesis. Additionally, transcriptomic comparison analyses of NSCLC subgroups were conducted. Between non-metastatic and metastatic NSCLC patients, 526 platelet DEGs were identified with the most altered expression. The outcomes from subgroup analysis between lung adenocarcinoma and lung squamous cell carcinoma demonstrated the diagnostic potential of platelet RNA-Seq on distinguishing tumor histological types.

Exploration of the platelet proteome in patients with early-stage cancer

Platelets play an important role in tumor growth and, at the same time, platelet characteristics are affected by cancer presence. Therefore, we investigated whether the platelet proteome harbors differentially expressed proteins associated with early-stage cancer. For this proof-of-concept study, patients with early-stage lung (n = 8) or head of pancreas cancer (n = 4) were included, as were healthy sex- and age-matched controls for both subgroups. Blood samples were collected from controls and from patients before surgery. Furthermore, from six of the patients, a second sample was collected two months after surgery. NanoLC-MS/MS-based proteomics of gel-fractionated platelet proteins was used for comparative spectral count analyses of patients to controls and before to after surgery samples. The total platelet proteome dataset included 4384 unique proteins of which 85 were significantly (criteria Fc > 1.5 and p < 0.05) changed in early-stage cancer compared to controls. In addition, the levels of 81 platelet proteins normalized after tumor resection. When filtering for the most discriminatory proteins, we identified seven promising platelet proteins associated with early-stage cancer. In conclusion, this pioneering study on the platelet proteome in cancer patients clearly identifies platelets as a new source of candidate protein biomarkers of early-stage cancer.

BIOLOGICAL SIGNIFICANCE

Currently, most blood-based diagnostics/biomarker research is performed in serum or plasma, while the content of blood cells is usually neglected. It is known that especially blood platelets, which are the main circulating pool of many bioactive proteins, such as growth factors, chemokines, and cytokines, are a potentially rich source of biomarkers. The current study is the first to measure the effect of early-stage cancer on the platelet proteome of patients. Our study demonstrates that the platelet proteome of patients with early-stage lung or head of pancreas cancer differs considerably compared to that of healthy individuals of matched sex and age. In addition, the platelet proteome of cancer patients normalized after surgical resection of the tumor. Exploiting platelet proteome differences linked to both tumor presence and disease status, we were able to demonstrate that the platelet proteome can be mined for potential biomarkers of cancer.

Patterns and functional implications of platelets upon tumor "education"

While platelets are traditionally recognized to play a predominant role in hemostasis and thrombosis, increasing evidence verifies its involvement in malignancies. As a component of the tumor microenvironment, platelets influence carcinogenesis, tumor metastasis and chemotherapy efficiency. Platelets status is thus predictable as a hematological biomarker of cancer prognosis and a hot target for therapeutic intervention. On the other hand, the role of circulating tumor cells (CTCs) as an inducer of platelet activation and aggregation has been well acknowledged. The cross-talk between platelets and CTCs is reciprocal on that the CTCs activate platelets while platelets contribute to CTCs' survival and dissemination. This review covers some of the current issues related to the loop between platelets and tumor aggression, including the manners of tumor cells in "educating" platelets and biofunctional alterations of platelets upon tumor "education". We also highlight the potential clinical applications on the interplay between tumors and platelets. Further studies with well-designed prospective multicenter trials may contribute to clinical "liquid biopsy" diagnosis by evaluating the global changes of platelets.