Activated platelets interact with lung cancer cells through P-selectin glycoprotein ligand-1

Glycan-Lectin interactions between platelets and tumor cells drive hematogenous metastasis

Glycosylation is a ubiquitous cellular or microenvironment-specific post-translational modification that occurs on the surface of normal cells and tumor cells. Tumor cell-associated glycosylation is involved in hematogenous metastasis. A wide variety of tumors undergo aberrant glycosylation to interact with platelets. As platelets have many opportunities to engage circulating tumor cells, they represent an important avenue into understanding the role glycosylation plays in tumor metastasis. Platelet involvement in tumor metastasis is evidenced by observations that platelets protect tumor cells from damaging shear forces and immune system attack, aid metastasis through the endothelium at specific sites, and facilitate tumor survival and colonization. During platelet-tumor-cell interactions, many opportunities for glycan-ligand binding emerge. This review integrates the latest information about glycans, their ligands, and how they mediate platelet-tumor interactions. We also discuss adaptive changes that tumors undergo upon glycan-lectin binding and the impact glycans have on targeted therapeutic strategies for treating tumors in clinical settings.

Revisiting the association between pretreatment thrombocytosis and cancer survival outcomes: an umbrella review of meta-analyses

BACKGROUND

Although associations have been reported linking pretreatment thrombocytosis to cancer survival outcomes, the validity and strength of existing observational evidence have been contested. This study aimed to conduct an umbrella review to comprehensively appraise the strength, validity and credibility of these reported associations.

METHODS

We searched Medline, Embase and Cochrane Database of Systematic Reviews from inception to 8 April 2023 to retrieve meta-analyses of observational studies. Meta-analyses were re-performed using a random-effect model and the strength of evidence was graded as convincing, highly suggestive, suggestive and weak according to seven pre-defined quantitative criteria reflecting statistical significance, amount of data, heterogeneity, and evidence of bias. The quality of review was appraised using the AMSTAR2 checklist. The umbrella review was reported adhering to the PRISMA guideline and was registered on PROSPERO (CRD42023455391).

RESULTS

A total of 21 unique meta-analyses investigating ten cancer subtypes were included. All meta-analyses reported inferior survival outcome in cancer patients with pretreatment thrombocytosis, and 18 of them (85.7%) yielded statistically significant results (P < 0.05). Consistent effects were observed across meta-analyses that adopted different cut-off values (i.e. platelet count > 300 or 400 × 109 /L) to define thrombocytosis. Although evidence appraisal did not identify convincing evidence (Class I), the associations of thrombocytosis with inferior overall survival of lung, gastric, colorectal cancer and malignant mesothelioma were classified as highly suggestive evidence (Class II). According to AMSTAR2 ratings, no meta-analysis was identified with high or moderate quality.

CONCLUSIONS

Our findings consolidated the association between pretreatment thrombocytosis and poor survival outcomes in various cancers. Nonetheless, the absence of convincing associations indicates a need for further large-scale, high-quality evidence to confirm whether platelets can serve as a prognostic predictor or a therapeutic target.

The interaction of platelet-related factors with tumor cells promotes tumor metastasis

Platelets not only participate in thrombosis and hemostasis but also interact with tumor cells and protect them from mechanical damage caused by hemodynamic shear stress and natural killer cell lysis, thereby promoting their colonization and metastasis to distant organs. Platelets can affect the tumor microenvironment via interactions between platelet-related factors and tumor cells. Metastasis is a key event in cancer-related death and is associated with platelet-related factors in lung, breast, and colorectal cancers. Although the factors that promote platelet expression vary slightly in terms of their type and mode of action, they all contribute to the overall process. Recognizing the correlation and mechanisms between these factors is crucial for studying the colonization of distant target organs and developing targeted therapies for these three types of tumors. This paper reviews studies on major platelet-related factors closely associated with metastasis in lung, breast, and colorectal cancers.

The updates on metastatic mechanism and treatment of colorectal cancer

Colorectal cancer (CRC) is a main cause of cancer death worldwide. Metastasis is a major cause of cancer-related death in CRC. The treatment of metastatic CRC has progressed minimally. However, the potential molecular mechanisms involved in CRC metastasis have remained to be comprehensively clarified. An improved understanding of the CRC mechanistic determinants is needed to better prevent and treat metastatic cancer. In this review, based on evidence from a growing body of research in metastatic cancers, we discuss the cellular and molecular mechanisms involved in CRC metastasis. This review reveals both the molecular mechanisms of metastases and identifies new opportunities for developing more effective strategies to target metastatic relapse and improve CRC patient outcomes.

Targeting protein glycosylation to regulate inflammation in the respiratory tract: novel diagnostic and therapeutic candidates for chronic respiratory diseases

Protein glycosylation is a widespread posttranslational modification that can impact the function of proteins. Dysregulated protein glycosylation has been linked to several diseases, including chronic respiratory diseases (CRDs). CRDs pose a significant public health threat globally, affecting the airways and other lung structures. Emerging researches suggest that glycosylation plays a significant role in regulating inflammation associated with CRDs. This review offers an overview of the abnormal glycoenzyme activity and corresponding glycosylation changes involved in various CRDs, including chronic obstructive pulmonary disease, asthma, cystic fibrosis, idiopathic pulmonary fibrosis, pulmonary arterial hypertension, non-cystic fibrosis bronchiectasis, and lung cancer. Additionally, this review summarizes recent advances in glycomics and glycoproteomics-based protein glycosylation analysis of CRDs. The potential of glycoenzymes and glycoproteins for clinical use in the diagnosis and treatment of CRDs is also discussed.

The platelet pannexin 1-IL-1β axis orchestrates pancreatic ductal adenocarcinoma invasion and metastasis

We aimed to investigate the protumor mechanisms of platelets in pancreatic ductal adenocarcinoma (PDAC). Serum samples were collected from 656 PDAC patients and 3105 healthy people, and a Panx1 knockout tumor model and an adoptive platelet transfusion mouse model were established. We showed that the blood platelet counts were not significantly different between stage III/IV and stage I/II patients, while the number of the CD41+/CD62P+ platelets was significantly elevated in stage III/IV patients, indicating that CD41+/CD62P+ platelets are associated with a poor prognosis. Further analysis showed that a high level of CD41+/CD62P+ platelets was significantly correlated with microvascular invasion (P = 0.002), advanced 8th edition AJCC stage (P < 0.001), and a high CA19-9 level (P = 0.027) and independently predicted a poor prognosis for resectable I/II PDAC. Furthermore, we found significantly higher Panx1 expression in CD41+/CD62P+ platelets than in CD41+/CD62P- platelets in PDAC patients. Mechanistically, Panx1 was able to enhance IL-1β secretion in CD41+/CD62P+ platelets by phosphorylating p38 MAPK and consequently promoted the invasion and metastasis of PDAC cells. Finally, we synthesized a novel compound named PC63435 by the ligation of carbenoxolone (a Panx1 inhibitor) and PSGL-1 (a CD62P ligand). PC63435 specifically bound to CD41+/CD62P+ platelets, then blocked the Panx1/IL-1β pathway and reduced the proportion of CD41+/CD62P+ platelets, which suppressed PDAC tumor invasion and metastasis in vivo. These results demonstrated that the Panx1/IL-1β axis in CD41+/CD62P+ platelets enhanced PDAC cell malignancy and that this axis may be a promising target for PDAC therapy.

PSGL-1 is a novel tumor microenvironment prognostic biomarker with cervical high-grade squamous lesions and more

Background

Macrophages secrete many cytokines and chemokines, which can provoke either an anti-tumor or pro-tumor immune response. P-selectin glycoprotein ligand-1 (PSGL-1) is expressed in macrophages and plays a vital role in synergizing for a more robust anti-tumor response. However, there are few studies about PSGL-1 expression status and clinical value of biological function in cervical cancer.

Methods

In this study, 565 participants were enrolled. PSGL-1 mRNA was detected by real-time quantitative PCR (qPCR) with cervical cytology specimens. The relationship between PSGL-1 and cervical intraepithelial neoplasia in two grades and more (CIN2+) was analyzed, and the optimal cut-off values of PSGL-1 to predict CIN2+ were calculated. In addition, the clinical significance of PSGL-1 in cervical cancer was determined by Kaplan-Meier Cox regression based on the database.

Results

The mean PSGL-1 increased significantly with cervical lesion development, especially compared with CIN2+ (p&lt;0.05). Moreover, the expression of PSGL-1 increased significantly in HPV-16/18 positive and HPV-18 positive, but not in HPV-16 positive and other HR-HPV positive. And then, it demonstrated that the area under the receiver operating characteristic curve (AUC) of PSGL-1 was 0.820, and an optimal cut-off 0.245. Furthermore, the PSGL-1 had the highest odds ratio and highest OR (OR= 8.707; 95% CI (.371-19.321)) for the detection of CIN 2+. In addition, our result also indicated that higher PSGL-1 expression was significantly related to a better prognosis in cervical cancer due to immune cell infiltration.

Conclusions

PSGL-1≥0.245 in cervical cytology specimens is a new auxiliary biomarker of CIN2+, and it may be a promising prognosis predictor and potential immunotherapy target linked with immune infiltration of cervical cancer.

Interactions between Platelets and Tumor Microenvironment Components in Ovarian Cancer and Their Implications for Treatment and Clinical Outcomes

Platelets, the primary operatives of hemostasis that contribute to blood coagulation and wound healing after blood vessel injury, are also involved in pathological conditions, including cancer. Malignancy-associated thrombosis is common in ovarian cancer patients and is associated with poor clinical outcomes. Platelets extravasate into the tumor microenvironment in ovarian cancer and interact with cancer cells and non-cancerous elements. Ovarian cancer cells also activate platelets. The communication between activated platelets, cancer cells, and the tumor microenvironment is via various platelet membrane proteins or mediators released through degranulation or the secretion of microvesicles from platelets. These interactions trigger signaling cascades in tumors that promote ovarian cancer progression, metastasis, and neoangiogenesis. This review discusses how interactions between platelets, cancer cells, cancer stem cells, stromal cells, and the extracellular matrix in the tumor microenvironment influence ovarian cancer progression. It also presents novel potential therapeutic approaches toward this gynecological cancer.

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.

Tumor Cell Capture Using Platelet-Based and Platelet-Mimicking Modified Human Serum Albumin Submicron Particles

The co-localization of platelets and tumor cells in hematogenous metastases has long been recognized. Interactions between platelets and circulating tumor cells (CTCs) contribute to tumor cell survival and migration via the vasculature into other tissues. Taking advantage of the interactions between platelets and tumor cells, two schemes, direct and indirect, were proposed to target the modified human serum albumin submicron particles (HSA-MPs) towards tumor cells. HSA-MPs were constructed by the Co-precipitation-Crosslinking-Dissolution (CCD) method. The anti-CD41 antibody or CD62P protein was linked to the HSA-MPs separately via 1-ethyl-3-(-3-dimethyl aminopropyl) carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) EDC/NHS chemistry. The size of modified HSA-MPs was measured at approximately 1 µm, and the zeta potential was around -24 mV. Anti-CD41-HSA-MPs adhered to platelets as shown by flowcytometry and confocal laser scanning microscopy. In vitro, we confirmed the adhesion of platelets to tumor lung carcinoma cells A549 under shearing conditions. Higher cellular uptake of anti-CD41-HSA-MPs in A549 cells was found in the presence of activated platelets, suggesting that activated platelets can mediate the uptake of these particles. RNA-seq data in the Cancer Cell Lineage Encyclopedia (CCLE) and The Cancer Genome Atlas (TCGA) database showed the expression of CD62P ligands in different types of cancers. Compared to the non-targeted system, CD62P-HSA-MPs were found to have higher cellular uptake in A549 cells. Our results suggest that the platelet-based and platelet-mimicking modified HSA-MPs could be promising options for tracking metastatic cancer.

Circulating tumor cell-blood cell crosstalk: Biology and clinical relevance

Circulating tumor cells (CTCs) are the seeds of distant metastasis, and the number of CTCs detected in the blood of cancer patients is associated with a worse prognosis. CTCs face critical challenges for their survival in circulation, such as anoikis, shearing forces, and immune surveillance. Thus, understanding the mechanisms and interactions of CTCs within the blood microenvironment is crucial for better understanding of metastatic progression and the development of novel treatment strategies. CTCs interact with different hematopoietic cells, such as platelets, red blood cells, neutrophils, macrophages, natural killer (NK) cells, lymphocytes, endothelial cells, and cancer-associated fibroblasts, which can affect CTC survival in blood. This interaction may take place either via direct cell-cell contact or through secreted molecules. Here, we review interactions of CTCs with blood cells and discuss the potential clinical relevance of these interactions as biomarkers or as targets for anti-metastatic therapies.

The integration of systemic and tumor PD-L1 as a predictive biomarker of clinical outcomes in patients with advanced NSCLC treated with PD-(L)1blockade agents

BACKGROUND

Tumor PD-L1 expression is a predictive biomarker for patients with NSCLC receiving PD-(L)1 blockade agents. However, although increased tumor PD-L1 expression predicts responsiveness, clinical benefit has been observed regardless of tumor PD-L1 expression, suggesting the existence of other PD-L1 sources. The aim of our study was to analyze whether integrating systemic and tumor PD-L1 is more predictive of efficacy in patients with advanced NSCLC receiving PD-(L)1 blockade agents.

MATERIAL AND METHODS

Twenty-nine healthy donors and 119 consecutive patients with advanced NSCLC treated with PD-(L)1 drug were prospectively included. Pretreatment blood samples were collected to evaluate PD-L1 levels on circulating immune cells, platelets (PLTs), platelet microparticles (PMPs), and the plasma soluble PD-L1 concentration (sPD-L1). Tumor PD-L1 status was assessed by immunohistochemistry. The percentages of circulating PD-L1 + leukocytes, sPD-L1 levels, and tumor PD-L1 were correlated with efficacy.

RESULTS

No differences in the percentages of circulating PD-L1 + leukocytes were observed according to tumor PD-L1 expression. Significantly longer progression-free survival was observed in patients with higher percentages of PD-L1 + CD14 + , PD-L1 + neutrophils, PD-L1 + PLTs, and PD-L1 + PMPs and significantly longer overall survival was observed in patients with higher percentages of PD-L1 + CD14 + and high tumor PD-L1 expression. Integrating the PD-L1 data of circulating and tumor PD-L1 results significantly stratified patients according to the efficacy of PD-(L1) blockade agents.

CONCLUSIONS

Our results suggest that integrating circulating PD-L1 + leukocytes, PLT, PMPs, and sPD-L1 and tumor PD-L1 expression may be helpful to decide on the best treatment strategy in patients with advanced NSCLC who are candidates for PD-(L)1 blockade agents.

Integrated tissue proteome and metabolome reveal key elements and regulatory pathways in cutaneous squamous cell carcinoma

Cutaneous squamous cell carcinoma (CSCC) is a widespread malignancy but has a very low long-term survival rate for patients at the metastatic stage. Therefore, it is urgent to identify prognostic biomarkers for CSCC and improve our understanding of disease progression. Here we took advantage of a data-independent acquisition (DIA)-based nano liquid chromatography equipped with an orbitrap mass spectrometry (nLC-MS/MS) and ultraperformance LC coupled to a time-of-flight tandem MS (UPLC-TOF-MS/MS) technique to analyze cancer and corresponding noncancerous tissues from 20 CSCC patients for integrated proteomic and metabolomic analyses. Overall, 6241 tissue proteins were detected, while 136 proteins were significantly expressed in CSCC tissues. Further functional analysis revealed that various biological processes were highly enriched and participated in the pathogenesis of CSCC, especially DNA damage responses. Moreover, 641 named metabolites in total were identified, among which 181 were significantly changed in CSCC tissues. A total of 101 pathways were significantly enriched including apoptosis, autophagy, PI3K-Akt and mTOR signaling pathways. Interestingly, two pathways, protein digestion & absorption and platelet activation were both enriched in proteomic and metabolomic studies involving 5 proteins and 11 metabolites. Accordingly, a four-metabolite panel consisting of arachidonate, glutamine, glutamic acid, and proline (all area under the curve (AUC) values more than 0.9) was developed with a high accuracy (0.971) to distinguish the 20 detected cancer tissues from their noncancerous tissues. Collectively, our work highlighted the key elements and regulatory pathways involved in the pathogenesis of CSCC. More importantly, the present study not only provided potential biomarkers for the early diagnosis of CSCC, but also expanded our knowledge of the physiopathology of the disease. SIGNIFICANCE: CSCC is the second most common human cancer but has few treatment options and few sensitive biomarkers for diagnosis. Here we comprehensively revealed its molecular characteristics by performing integrated tissue proteomic and metabolomic analyses. Significantly distinct profiles and certain enriched pathways including DNA damage responses were identified as associated with CSCC. Moreover, protein digestion & absorption and platelet activation were both enriched in the proteome and metabolome. These identified molecular changes probably play significant roles in CSCC development. Finally, we developed a four-metabolite panel to distinguish CSCC with high accuracy. Overall, our data not only provided potential diagnostic biomarkers, but also extended knowledge on the pathogenesis of CSCC.

Airborne particulate matter upregulates expression of early and late adhesion molecules and their receptors in a lung adenocarcinoma cell line

BACKGROUND

Epidemiological evidence associates chronic exposure to particulate matter (PM) with respiratory damage and lung cancer. Inhaled PM may induce systemic effects including inflammation and metastasis. This study evaluated whether PM induces expression of adhesion molecules in lung cancer cells promoting interaction with monocytes.

METHODS

The expression of early and late adhesion molecules and their receptors was evaluated in A549 (human lung adenocarcinoma) cells using a wide range of concentrations of PM_2.5 and PM₁₀. Then we evaluated cellular adhesion between A549 cells and U937 (human monocytes) cells after PM exposure.

RESULTS

We found higher expression of both early and late adhesion molecules and their ligands in lung adenocarcinoma cells exposed to PM_2.5 and PM₁₀ particles present in the air pollution at Mexico City from 0.03 μg/cm² with a statistically significant difference (p ≤ 0.05). PM₁₀ had stronger effect than PM_2.5. Both PM also stimulated cellular adhesion between tumor cells and monocytes.

CONCLUSIONS

This study reveals a comprehensive expression profile of adhesion molecules and their ligands upregulated by PM_2.5 and PM₁₀ in A549 cells. Additionally these particles induced cellular adhesion of lung cancer cells to monocytes. This highlights possible implications of PM in two cancer hallmarks i.e. inflammation and metastasis, underlying the high cancer mortality associated with air pollution.

Aspirin and antiplatelet treatments in cancer

Platelets have been hypothesized to promote certain neoplastic malignancies; however, antiplatelet drugs are still not part of routine pharmacological cancer prevention and treatment protocols. Paracrine interactions between platelets and cancer cells have been implicated in potentiating the dissemination, survival within the circulation, and extravasation of cancer cells at distant sites of metastasis. Signals from platelets have also been suggested to confer epigenetic alterations, including upregulating oncoproteins in circulating tumor cells, and secretion of potent growth factors may play roles in promoting mitogenesis, angiogenesis, and metastatic outgrowth. Thrombocytosis remains a marker of poor prognosis in patients with solid tumors. Experimental data suggest that lowering of platelet count may reduce tumor growth and metastasis. On the basis of the mechanisms by which platelets could contribute to cancer growth and metastasis, it is conceivable that drugs reducing platelet count or platelet activation might attenuate cancer progression and improve outcomes. We will review select pharmacological approaches that inhibit platelets and may affect cancer development and propagation. We begin by presenting an overview of clinical cancer prevention and outcome studies with low-dose aspirin. We then review current nonclinical development of drugs targeted to platelet binding, activation, and count as potential mitigating agents in cancer.

PSGL-1 Immune Checkpoint Inhibition for CD4+ T Cell Cancer Immunotherapy

Immune checkpoint inhibition targeting T cells has shown tremendous promise in the treatment of many cancer types and are now standard therapies for patients. While standard therapies have focused on PD-1 and CTLA-4 blockade, additional immune checkpoints have shown promise in promoting anti-tumor immunity. PSGL-1, primarily known for its role in cellular migration, has also been shown to function as a negative regulator of CD4+ T cells in numerous disease settings including cancer. PSGL-1 is highly expressed on T cells and can engage numerous ligands that impact signaling pathways, which may modulate CD4+ T cell differentiation and function. PSGL-1 engagement in the tumor microenvironment may promote CD4+ T cell exhaustion pathways that favor tumor growth. Here we highlight that blocking the PSGL-1 pathway on CD4+ T cells may represent a new cancer therapy approach to eradicate tumors.

PSGL-1 Inhibits the Incorporation of SARS-CoV and SARS-CoV-2 Spike Glycoproteins into Pseudovirions and Impairs Pseudovirus Attachment and Infectivity

P-selectin glycoprotein ligand-1 (PSGL-1) is a cell surface glycoprotein that binds to P-, E-, and L-selectins to mediate the tethering and rolling of immune cells on the surface of the endothelium for cell migration into inflamed tissues. PSGL-1 has been identified as an interferon-γ (INF-γ)-regulated factor that restricts HIV-1 infectivity, and has recently been found to possess broad-spectrum antiviral activities. Here we report that the expression of PSGL-1 in virus-producing cells impairs the incorporation of SARS-CoV and SARS-CoV-2 spike (S) glycoproteins into pseudovirions and blocks pseudovirus attachment and infection of target cells. These findings suggest that PSGL-1 may potentially inhibit coronavirus replication in PSGL-1+ cells.

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.

PSGL-1 inhibits the virion incorporation of SARS-CoV and SARS-CoV-2 spike glycoproteins and impairs virus attachment and infectivity

P-selectin glycoprotein ligand-1 (PSGL-1) is a cell surface glycoprotein that binds to P-, E-, and L-selectins to mediate the tethering and rolling of immune cells on the surface of the endothelium for cell migration into inflamed tissues. PSGL-1 has been identified as an interferon-γ (INF-γ)-regulated factor that restricts HIV-1 infectivity, and has recently been found to possess broad-spectrum antiviral activities. Here we report that the expression of PSGL-1 in virus-producing cells impairs the incorporation of SARS-CoV and SARS-CoV-2 spike (S) glycoproteins into pseudovirions and blocks virus attachment and infection of target cells. These findings suggest that PSGL-1 may potentially inhibit coronavirus replication in PSGL-1+ cells.

EMT-Associated Heterogeneity in Circulating Tumor Cells: Sticky Friends on the Road to Metastasis

Epithelial-mesenchymal transitions (EMTs) generate hybrid phenotypes with an enhanced ability to adapt to diverse microenvironments encountered during the metastatic spread. Accordingly, EMTs play a crucial role in the biology of circulating tumor cells (CTCs) and contribute to their heterogeneity. Here, we review major EMT-driven properties that may help hybrid Epithelial/Mesenchymal CTCs to survive in the bloodstream and accomplish early phases of metastatic colonization. We then discuss how interrogating EMT in CTCs as a companion biomarker could help refine cancer patient management, further supporting the relevance of CTCs in personalized medicine.

Quantification of heparin's antimetastatic effect by single-cell force spectroscopy

In circulation, cancer cells induce platelet activation, leading to the formation of a cancer cell-encircling platelet cloak which facilitates each step of the metastatic cascade. Since cancer patients treated with the anticoagulant heparin showed reduced metastasis rates and improved survival, it is supposed that heparin suppresses the cloak's formation by inhibiting the interaction between platelet's adhesion molecule P-selectin with its ligands on cancer cells. To quantify this heparin effect, we developed a single-cell force spectroscopy approach and quantified the adhesion (maximum adhesion force [F_A ] and detachment work [W_D ]) between platelets and human non-small cell lung cancer cells (A549). A configuration was used in which A549 cells were glued to tipless cantilevers and force-distance (F-D) curves were recorded on a layer of activated platelets. The concentration-response relationship was determined for heparin at concentrations between 1 and 100 U/mL. Sigmoid dose-response fit revealed half-maximal inhibitory concentration (IC₅₀ ) values of 8.01 U/mL (F_A ) and 6.46 U/mL (W_D ) and a maximum decrease of the adhesion by 37.5% (F_A ) and 38.42% (W_D ). The effect of heparin on P-selectin was tested using anti-P-selectin antibodies alone and in combination with heparin. Adding heparin after antibody treatment resulted in an additional reduction of 9.52% (F_A ) and 7.12% (W_D ). Together, we quantified heparin's antimetastatic effect and proved that it predominantly is related to the blockage of P-selectin. Our approach represents a valuable method to investigate the adhesion of platelets to cancer cells and the efficiency of substances to block this interaction.

Circulating tumor cells in cancer patients: developments and clinical applications for immunotherapy

Cancer metastasis is the leading cause of cancer-related death. Circulating tumor cells (CTCs) are shed into the bloodstream from either primary or metastatic tumors during an intermediate stage of metastasis. In recent years, immunotherapy has also become an important focus of cancer research. Thus, to study the relationship between CTCs and immunotherapy is extremely necessary and valuable to improve the treatment of cancer. In this review, based on the advancements of CTC isolation technologies, we mainly discuss the clinical applications of CTCs in cancer immunotherapy and the related immune mechanisms of CTC formation. In order to fully understand CTC formation, sufficiently and completely understood molecular mechanism based on the different immune cells is critical. This understanding is a promising avenue for the development of effective immunotherapeutic strategies targeting CTCs.

Molecular Requirements for the Expression of Antiplatelet Effects by Synthetic Structural Optimized Analogues of the Anticancer Drugs Imatinib and Nilotinib

Background

Platelets play important roles in cancer progression and metastasis, as well as in cancer-associated thrombosis (CAT). Tyrosine kinases are implicated in several intracellular signaling pathways involved in tumor biology, thus tyrosine kinase inhibitors (TKIs) represent an important class of anticancer drugs, based on the concept of targeted therapy.

Purpose

The objective of this study is the design and synthesis of analogues of the TKIs imatinib and nilotinib in order to develop tyrosine kinase inhibitors, by investigating their molecular requirements, which would express antiplatelet properties.

Methods

Based on a recently described by us improved approach in the preparation of imatinib and/or nilotinib analogues, we designed and synthesized in five-step reaction sequences, 8 analogues of imatinib (I-IV), nilotinib (V, VI) and imatinib/nilotinib (VII, VIII). Their inhibitory effects on platelet aggregation and P-selectin membrane expression induced by arachidonic acid (AA), adenosine diphosphate (ADP) and thrombin receptor activating peptide-6 (TRAP-6), in vitro, were studied. Molecular docking studies and calculations were also performed.

Results

The novel analogues V-VIII were well established with the aid of spectroscopic methods. Imatinib and nilotinib inhibited AA-induced platelet aggregation, exhibiting IC₅₀ values of 13.30 μΜ and 3.91 μΜ, respectively. Analogues I and II exhibited an improved inhibitory activity compared with imatinib. Among the nilotinib analogues, V exhibited a 9-fold higher activity than nilotinib. All compounds were less efficient in inhibiting platelet aggregation towards ADP and TRAP-6. Similar results were obtained for the membrane expression of P-selectin. Molecular docking studies showed that the improved antiplatelet activity of nilotinib analogue V is primarily attributed to the number and the strength of hydrogen bonds.

Conclusion

Our results show that there is considerable potential to develop synthetic analogues of imatinib and nilotinib, as TKIs with antiplatelet properties and therefore being suitable to target cancer progression and metastasis, as well as CAT by inhibiting platelet activation.

A Peptide Analogue of Selectin Ligands Attenuated Atherosclerosis by Inhibiting Monocyte Activation

Background

Circulating monocytes play a critical role in the pathogenesis of atherosclerosis. Monocyte homing to sites of atherosclerosis is primarily initiated by selectin. Thus, blockade of the interaction of selectins and their ligands holds a significant role in monocyte homing which might be a potential approach to treat atherosclerosis. Here, we investigated the efficacy of a novel peptide analogue of selectin ligands IELLQAR in atherosclerosis.

Methods and Results

In this study, we firstly measured the effect of the IELLQAR selectin-binding peptide on the inhibition of binding of selectins to monocytes by flow cytometry, which exhibited a dose-dependent inhibitory effect on the binding of the P-, E-, and L-selectins to monocytes, especially the inhibition of P-selectin binding to human peripheral blood monocytes (PBMCs) (half maximal inhibitory concentration (IC₅₀~5 μM)) and THP-1 cells (IC₅₀~10 μM). Furthermore, IELLQAR inhibited P-selectin-induced activation of CD11b on the surface of monocytes and decreased adhesion of monocytes to the endothelium. ApoE^-/- mice with or without IELLQAR (1 or 3 mg/kg) fed a Western-type diet (WTD) or which had disturbed blood flow-induced shear stress underwent partial left carotid artery ligation (PLCA) to induce atherosclerosis. In the WTD- and PLCA-induced atherosclerosis models, atherosclerotic plaque formation and monocyte/macrophage infiltration of the arterial wall both decreased in ApoE^-/- mice treated with the IELLQAR peptide. Our results also revealed that IELLQAR inhibited the differentiation of monocytes into macrophages through P-selectin-dependent activation of the nuclear factor- (NF-) κB and mammalian target of rapamycin (mTOR) pathways.

Conclusion

Collectively, our results demonstrated that IELLQAR, a peptide analogue of selectin ligands, inhibited selectin binding to monocytes, which led to subsequent attenuation of atherosclerosis via inhibition of monocyte activation. Hence, use of the IELLQAR peptide provides a new approach and represents a promising candidate for the treatment of atherosclerosis in the early stage of disease.

Elevated Platelet Count Appears to Be Causally Associated with Increased Risk of Lung Cancer: A Mendelian Randomization Analysis

BACKGROUND

Platelets are a critical element in coagulation and inflammation, and activated platelets are linked to cancer risk through diverse mechanisms. However, a causal relationship between platelets and risk of lung cancer remains unclear.

METHODS

We performed single and combined multiple instrumental variable Mendelian randomization analysis by an inverse-weighted method, in addition to a series of sensitivity analyses. Summary data for associations between SNPs and platelet count are from a recent publication that included 48,666 Caucasian Europeans, and the International Lung Cancer Consortium and Transdisciplinary Research in Cancer of the Lung data consisting of 29,266 cases and 56,450 controls to analyze associations between candidate SNPs and lung cancer risk.

RESULTS

Multiple instrumental variable analysis incorporating six SNPs showed a 62% increased risk of overall non-small cell lung cancer [NSCLC; OR, 1.62; 95% confidence interval (CI), 1.15-2.27; P = 0.005] and a 200% increased risk for small-cell lung cancer (OR, 3.00; 95% CI, 1.27-7.06; P = 0.01). Results showed only a trending association with NSCLC histologic subtypes, which may be due to insufficient sample size and/or weak effect size. A series of sensitivity analysis retained these findings.

CONCLUSIONS

Our findings suggest a causal relationship between elevated platelet count and increased risk of lung cancer and provide evidence of possible antiplatelet interventions for lung cancer prevention.

IMPACT

These findings provide a better understanding of lung cancer etiology and potential evidence for antiplatelet interventions for lung cancer prevention.

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.

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.

Hypoxia and the Tumor Secretome

Metastasis remains the leading cause of cancer-related deaths. To date, there are no specific treatments targeting disseminated disease. New therapeutic options will become available only if we enhance our understanding of mechanisms underlying metastatic spread. A large body of literature shows that the metastatic potential of tumor cells is strongly influenced by microenvironmental cues such as low oxygen (hypoxia). Clinically, hypoxia is a hallmark of most solid tumors and is associated with increased metastasis and poor survival in a variety of cancer types. Mechanistically, hypoxia influences multiple steps within the metastatic cascade and particularly impacts the interactions between tumor cells and host stroma at both primary and secondary sites. Here we review current evidence for a hypoxia-induced tumor secretome and its impact on metastatic progression. These studies have identified potential biomarkers and therapeutic targets that could be integrated into strategies for preventing and treating metastatic disease.

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.

Peptidylarginine deiminase 4: a nuclear button triggering neutrophil extracellular traps in inflammatory diseases and aging

Peptidylarginine deiminase 4 (PAD4) is a nuclear citrullinating enzyme that is critically involved in the release of decondensed chromatin from neutrophils as neutrophil extracellular traps (NETs). NETs, together with fibrin, are implicated in host defense against pathogens; however, the formation of NETs (NETosis) has injurious effects that may outweigh their protective role. For example, PAD4 activity produces citrullinated neoantigens that promote autoimmune diseases, such as rheumatoid arthritis, to which PAD4 is genetically linked and where NETosis is prominent. NETs are also generated in basic sterile inflammatory responses that are induced by many inflammatory stimuli, including cytokines, hypoxia, and activated platelets. Mice that lack PAD4-deficient in NETosis-serve as an excellent tool with which to study the importance of NETs in disease models. In recent years, animal and human studies have demonstrated that NETs contribute to the etiology and propagation of many common noninfectious diseases, the focus of our review. We will discuss the role of NETs in thrombotic and cardiovascular disease, the induction of NETs by cancers and its implications for cancer progression and cancer-associated thrombosis, and elevated NETosis in diabetes and its negative impact on wound healing, and will propose a link between PAD4/NETs and age-related organ fibrosis. We identify unresolved issues and new research directions.-Wong, S. L., Wagner, D. D. Peptidylarginine deiminase 4: a nuclear button triggering neutrophil extracellular traps in inflammatory diseases and aging.

Platelets in cancer and thrombosis

Platelets are the smallest circulating blood cells and their major function is the maintenance of haemostasis. They do not have a nucleus, but instead a multitude of granules that contain molecules important for several physiological processes. These granules can be released after platelet activation and thereby platelets take part in haemostasis, wound repair or immunological processes. Furthermore, platelets are also involved in the pathophysiology of several diseases, including cancer. Platelets can support various steps of cancer development and progression by promoting tumour growth, angiogenesis and metastasis. Moreover, platelets contribute to the hypercoagulable state frequently observed in cancer patients, leading to an increased risk of venous thromboembolism (VTE). In previous studies a high platelet count was repeatedly found to be associated with an elevated risk of VTE and a worse prognosis in patients with cancer.

The aim of this review is to give an overview of the most important alterations of platelet physiology in cancer patients and how these alterations may influence cancer disease and contribute to cancer-associated VTE.

Platelet Integrins in Tumor Metastasis: Do They Represent a Therapeutic Target?

Platelets are small anucleated cell fragments that ensure the arrest of bleeding after a vessel wall injury. They are also involved in non-hemostatic function such as development, immunity, inflammation, and in the hematogeneous phase of metastasis. While the role of platelets in tumor metastasis has been recognized for 60 years, the molecular mechanism underlying this process remains largely unclear. Platelets physically and functionally interact with various tumor cells through surface receptors including integrins. Platelets express five integrins at their surface, namely α2β1, α5β1, α6β1, αvβ3, and αIIbβ3, which bind preferentially to collagen, fibronectin, laminin, vitronectin, and fibrinogen, respectively. The main role of platelet integrins is to ensure platelet adhesion and aggregation at sites of vascular injury. Two of these, α6β1 and αIIbβ3, were proposed to participate in platelet–tumor cell interaction and in tumor metastasis. It has also been reported that pharmacological agents targeting both integrins efficiently reduce experimental metastasis, suggesting that platelet integrins may represent new anti-metastatic targets. This review focuses on the role of platelet integrins in tumor metastasis and discusses whether these receptors may represent new potential targets for novel anti-metastatic approaches.

Targeting P-selectin blocks neuroblastoma growth

Selectins and their ligands have been implicated in tumor growth and progression in carcinomas, but their role in neuroblastoma has not been systematically examined. In the current study we evaluated L-, P- and E-selectin binding to neuroblastoma cells and the expression of some of their known ligands, namely CD44, CD24 and P-selectin glycoprotein ligand-1 (PSGL-1). Genetic loss of PSGL-1 or CD24 and pharmacological inhibition of P-selectin reduced P-selectin binding to neuroblastoma cells in vitro. Targeting P-selectin using specific antibodies promoted a significant reduction in the growth of neuroblastoma tumors in vivo. In mechanistic studies binding of P-selectin to neuroblastoma cells activated Src and several other pro-survival kinases such as ERK1, AKT, FAK and p38. Interestingly, comparative mass single cell cytometry (CyTOF) analyses revealed considerable intra- and inter-cell line heterogeneity with respect to response to P-selectin binding. Additionally, the downstream response to all selectins showed general similarity. Our findings reported here not only provide pre-clinical evidence in support of therapeutic targeting of P-selectin, but also highlight the heterogeneity in response of tumor cells to P-selectin binding. These observations provide the basis for combining P-selectin inhibition with other targeted therapies for neuroblastoma.

Extracellular vesicles: how they interact with endothelium, potentially contributing to metastatic cancer cell implants

Extracellular vesicles (EV) are blebs of cellular membranes, which entrap small portions of subjacent cytosol. They are released from a variety of cells, circulate in the blood for an unknown length of time and come to rest on endothelial surfaces. They contribute to an array of physiologic pathways, the complexity of which is still being investigated. They contribute to metastatic malignant cell implants and tumor-related angiogenesis, possibly abetted by the tissue factor that they carry. It is thought that the adherence of the EV to endothelium is dependent upon a combination of their P-selectin glycoprotein ligand-1 and exposed phosphatidylserine, the latter of which is normally hidden on the inner bilayer of the intact cellular membrane. This manuscript reviews what is known about EV origins, their clearance from the circulation and how they contribute to malignant cell implants upon endothelium surfaces and subsequent tumor growth.

Targeting Platelets for the Treatment of Cancer

The majority of cancer-associated mortality results from the ability of tumour cells to metastasise leading to multifunctional organ failure and death. Disseminated tumour cells in the blood circulation are faced with major challenges such as rheological shear stresses and cell-mediated cytotoxicity mediated by natural killer cells. Nevertheless, circulating tumour cells with metastatic ability appear equipped to exploit host cells to aid their survival. Despite the long interest in targeting tumour-associated host cells such as platelets for cancer treatment, the clinical benefit of this strategy is still under question. In this review, we provide a summary of the latest mechanistic and clinical evidence to evaluate the validity of targeting platelets in cancer.

The Interaction of Selectins and PSGL-1 as a Key Component in Thrombus Formation and Cancer Progression

Cellular interaction is inevitable in the pathomechanism of human disease. Formation of heterotypic cellular aggregates, between distinct cells of hematopoietic and nonhematopoietic origin, may be involved in events leading to inflammation and the complex process of cancer progression. Among adhesion receptors, the family of selectins with their ligands have been considered as one of the major contributors to cell-cell interactions. Consequently, the inhibition of the interplay between selectins and their ligands may have potential therapeutic benefits. In this review, we focus on the current evidence on the selectins as crucial modulators of inflammatory, thrombotic, and malignant disorders. Knowing that there is promiscuity in selectin binding, we outline the importance of a key protein that serves as a ligand for all selectins. This dimeric mucin, the P-selectin glycoprotein ligand 1 (PSGL-1), has emerged as a major player in inflammation, thrombus, and cancer development. We discuss the interaction of PSGL-1 with various selectins in physiological and pathological processes with particular emphasis on mechanisms that lead to severe disease.

Decreased platelet reactivity in patients with cancer is associated with high risk of venous thromboembolism and poor prognosis

Platelets are suggested to play a crucial role in cancer progression and the prothrombotic state of cancer patients. Here, we aimed to examine the activation status of platelets in cancer patients and investigate their association with risk of death and occurrence of venous thromboembolism (VTE) in a prospective observational cohort study. We measured platelet surface P-selectin, activated glycoprotein (GP) IIb/IIIa and monocyte-platelet aggregate (MPA) formation in vivo and platelet response to ex vivo stimulation with agonists of protease-activated receptor (PAR) -1, -4, and GPVI, by whole blood flow cytometry, before beginning of chemotherapy and repeatedly during the first six months thereafter (total number of samples analysed: 230). Endpoints of the study were occurrence of death or VTE during a two-year follow-up, respectively. Of 62 patients (median age [interquartile range, IQR]: 63 [54-70] years, 48 % female), 32 (51.6 %) died and nine (14.5 %) developed VTE. Association with a higher risk of death was found for lower platelet surface expression of P-selectin and activated GPIIb/IIIa in vivo and in response to PAR-1, -4 and GPVI activation, but not for MPA formation. Furthermore, reduced platelet responsiveness to PAR-1 and GPVI agonists was associated with higher risk of VTE (hazard ratio per decile increase of percentage P-selectin positive platelets: 0.73 [0.56-0.92, p=0.007] and 0.77 [0.59-0.98, p=0.034], respectively). In conclusion, cancer patients with a poor prognosis showed decreased platelet reactivity, presumably as a consequence of continuous activation. Our data suggest that decreased platelet reactivity is associated with increased mortality and VTE in cancer.

Inhibition of the Biosynthesis of Prostaglandin E2 By Low-Dose Aspirin: Implications for Adenocarcinoma Metastasis

Meta-analyses have demonstrated that low-dose aspirin reduces the risk of developing adenocarcinoma metastasis, and when colon cancer is detected during aspirin treatment, there is a remarkable 83% reduction in risk of metastasis. As platelets participate in the metastatic process, the antiplatelet action of low-dose aspirin likely contributes to its antimetastatic effect. Cycloxooxygenase-2 (COX-2)-derived prostaglandin E₂ (PGE₂) also contributes to metastasis, and we addressed the hypothesis that low-dose aspirin also inhibits PGE₂ biosynthesis. We show that low-dose aspirin inhibits systemic PGE₂ biosynthesis by 45% in healthy volunteers (P < 0.0001). Aspirin is found to be more potent in colon adenocarcinoma cells than in the platelet, and in lung adenocarcinoma cells, its inhibition is equivalent to that in the platelet. Inhibition of COX by aspirin in colon cancer cells is in the context of the metastasis of colon cancer primarily to the liver, the organ exposed to the same high concentrations of aspirin as the platelet. We find that the interaction of activated platelets with lung adenocarcinoma cells upregulates COX-2 expression and PGE₂ biosynthesis, and inhibition of platelet COX-1 by aspirin inhibits PGE₂ production by the platelet-tumor cell aggregates. In conclusion, low-dose aspirin has a significant effect on extraplatelet cyclooxygenase and potently inhibits COX-2 in lung and colon adenocarcinoma cells. This supports a hypothesis that the remarkable prevention of metastasis from adenocarcinomas, and particularly from colon adenocarcinomas, by low-dose aspirin results from its effect on platelet COX-1 combined with inhibition of PGE₂ biosynthesis in metastasizing tumor cells. Cancer Prev Res; 9(11); 855-65. ©2016 AACR.

Interaction between circulating cancer cells and platelets: clinical implication

Metastasis is the main cause of cancer-associated mortality. During this complicated process, some cancer cells, also called circulating tumor cells (CTCs), detach from primary sites, enter bloodstream and extravasate at metastatic site. Thrombocytosis is frequently observed in patients with metastatic cancers suggesting the important role of platelets in metastasis. Therefore this review focuses on how platelets facilitate the generation of CTCs, protect them from various host attacks, such as immune assaults, apoptosis and shear stress, and regulate CTCs intravasation/extravasation. Platelet-derived cytokines and receptors are involved in this cascade. Identification the mechanisms underlie platelet-CTCs interactions could lead to the development of new platelet-targeted therapeutic strategy to reduce metastasis.

No evidence for increased platelet activation in patients with hepatitis B- or C-related cirrhosis and hepatocellular carcinoma

INTRODUCTION

Cancer is a major risk factor for developing venous thromboembolism (VTE). Plasma hypercoagulability is an established risk factor for cancer-related VTE. In addition, thrombocytosis and hyperreactive platelets have been implicated in VTE and cancer progression. Cirrhosis is associated with changes in platelet number and function. The platelet activation status of patients with cirrhosis and hepatocellular carcinoma has not yet been established. Here we assessed the platelet activation status in patients with hepatitis-related cirrhosis in presence or absence of HCC.

MATERIALS AND METHODS

We performed a cross-sectional study including thirty-eight consecutive patients with hepatitis B- or C- related liver cirrhosis in presence or absence of HCC. We studied basal and agonist-induced platelet activation using flow cytometry. In addition, we studied the plasma levels of von Willebrand factor (VWF) and the VWF-cleaving protease ADAMTS13. Twenty healthy volunteers served as controls.

RESULTS

We found no evidence of basal platelet activation in patients with cirrhosis compared to controls. However, we found reduced agonist-induced platelet activation in patients. No differences in the basal and agonist-induced platelets activation status between patients with or without HCC were detected. Plasma levels of VWF were increased and the levels of ADAMTS13 activity were decreased in patients compared to controls. No differences between the levels of VWF and ADAMTS13 in patients with or without HCC were detected.

CONCLUSIONS

HCC development or recurrence in patients with hepatitis B- or C-related cirrhosis does not appear to be associated with platelet activation and changes in pivotal proteins in primary hemostasis.

Involvement of platelet-tumor cell interaction in immune evasion. Potential role of podocalyxin-like protein 1

Besides their essential role in hemostasis and thrombosis, platelets are involved in the onset of cancer metastasis by interacting with tumor cells. Platelets release secretory factors that promote tumor growth, angiogenesis, and metastasis. Furthermore, the formation of platelet-tumor cell aggregates in the bloodstream provides cancer cells with an immune escape mechanism by protecting circulating malignant cells from immune-mediated lysis by natural killer (NK) cells. Platelet-tumor cell interaction is accomplished by specific adhesion molecules, including integrins, selectins, and their ligands. Podocalyxin-like protein 1 (PCLP1) is a selectin-ligand protein in which overexpression has been associated with several aggressive cancers. PCLP1 expression enhances cell adherence to platelets in an integrin-dependent process and through the interaction with P-selectin expressed on activated platelets. However, the involvement of PCLP1-induced tumor-platelet interaction in tumor immune evasion still remains unexplored. The identification of selectin ligands involved in the interaction of platelets with tumor cells may provide help for the development of effective therapies to restrain cancer cell dissemination. This article summarizes the current knowledge on molecules that participate in platelet-tumor cell interaction as well as discusses the potential role of PCLP1 as a molecule implicated in tumor immune evasion.

P-selectin expression in a colon tumor model exposed by sinusoidal electromagnetic fields

P-selectin is mainly involved in the initial process of tumor cell adhesion to platelets. The aim of the present study was to determine the expression level of P-selectin in a colon tumor model affected by sinusoidal electromagnetic fields (SMF). Male Wistar albino rats aged 2-2.5 months were used. The animals were divided into the I [N-Methyl-N-Nitrosurea (MNU)], II (SMF-MNU), III (SMF) and IV (control) groups. The rats were housed five per polycarbonate cage. Sixty milligrams of MNU was dissolved in 6 ml sterile 0.9% NaCl. Prepared solutions were administered intra rectally (i.r.) to the 1st and 3rd groups as 0.2 ml/per animal. The same procedure was applied to the 2nd and 4th groups, although 0.2 ml/per animal sterile isotonic solution was administered instead. This procedure was repeated once a week for 10 weeks. Following the administration of MNU, the 2nd and 3rd groups were exposed to a sinusoidal magnetic field (SMF, 50 Hz, 5 mT) for 6 h/day for 8 months. P-selectin expression of the four groups of rat colon tissues was determined using immunohistochemistry on paraffin sections. The labeled streptavidin biotin method was performed. Fisher's exact test was used for differences between proportions. Results showed that there was no statistically significant (P>0.05) change in the expression level of P-selectin. However, this result should be verified by both in vivo and in vitro experiments to determine the effects of the magnetic fields on P-selectin.

Over-sulfated glycosaminoglycans are alternative selectin ligands: insights into molecular interactions and possible role in breast cancer metastasis

Distant metastasis account for about 90 % of cancer associated deaths, and yet the oncology field is cruelly lacking tools to accurately predict and/or prevent metastasis. Distant metastasis occurs when circulating tumor cells interact with the endothelium of distant organs and extravasate from the blood vessel into the surrounding tissue. Selectins are a family of carbohydrate receptors well depicted for their role in tumor cells extravasation. They mediate primary interactions of cancer cells with endothelial cells, as well as secondary interactions with leucocytes and platelets, which are also promoting metastasis. The cancer associated carbohydrate antigen sialyl-Lewis x (sLe(x)) has been repeatedly shown to be involved, as selectin ligand, in these interactions. However, recent studies have highlighted that glycosaminoglycans (GAGs), another class of glycans, may also serve as ligands for selectins. We report herein that cancer-associated GAGs are differentially recognized by selectins according to their density of sulfation and the pH conditions of the binding. We also show that these parameters regulate platelets-cancer cells heterotypic aggregation, supporting the idea that GAGs may have pro-metastatic function. Combining our experimental results with in depth analyses of molecular dockings, we propose a model of GAG/selectin interactions robust enough to recapitulate the differential binding of selectins to GAGs, the competition between GAGs and sLe(x) for selectin binding and the effect of sub-physiological pH on GAGs affinities towards selectins. Altogether, our data suggest GAGs to be good ligands for selectins, potentially promoting distant metastasis in a complementary way to sLe(x).