Involvement of platelets in tumor cell metastasis

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.

Distinct characteristics of neonatal platelet reactivity

Platelets undergo a process of developmental maturation, and hence its regulation of vascular integrity and control of hemostasis at various stages of neonatal ages deserves better characterization. Functional assays for platelets require a larger volume of blood than what is feasible to collect in neonates, creating a technical hurdle that has been a challenge to investigate neonatal platelets. For this reason, the current knowledge of neonatal platelet function has been based on studies from cord blood-derived platelets as a surrogate for neonatal peripheral blood. Studies indicate that neonatal platelets are hypofunctional to various agonists, although neonates tend to maintain normal hemostasis. This apparently paradoxical finding may be due to several factors, such as elevated functionally potent von Willebrand factor multimers or hematocrit levels, in the neonatal blood that enhance the platelet and vessel wall interaction, and counteract platelet hyporeactivity. This review describes the functional characteristics of neonatal platelets, differences in platelet reactivity between neonates and adults, and potential biomarkers of platelet activation.

Evaluation of ALCAM, PECAM-1 and selectin levels in intracranial meningiomas

OBJECTIVES

Cell adhesion molecules play a major role in various pathological states. The aim of this study was to evaluate the tissue levels of selectins (E-, L-, and P-Selectins), activated leukocyte cell adhesion molecule (ALCAM) and platelet endothelial cell adhesion molecule-1 (PECAM-1) in intracranial meningiomas and compare with the levels in control tissues.

PATIENTS AND METHODS

20 consecutive patients who were operated on meningiomas (grade-I: 17 and grade-II: 3) and 15 cerebral tissues obtained during the autopsy procedures as a resource for the healthy controls were included in this study.

RESULTS

All three selectins', ALCAM and PECAM-1 levels were found to be significantly higher in meningiomas when compared with the control tissues (p<0.001, p<0.001, p<0.001, p<0.05, p<0.001), respectively.

CONCLUSIONS

According to our results, the adhesion molecules were found to be higher in meningiomas suggesting that they may be involved in the pathological process of this type of brain tumors. We conceive that developing alternate therapies such as immunotherapeutic approaches against brain tumors might be amendatory in the treatment. Since this is the first study performed in meningioma type brain tumors demonstrating and comparing the levels of various adhesion molecules with control tissues, further clinical and experimental studies are needed to support our current findings with higher number of patients.

Epithelial-mesenchymal plasticity and circulating tumor cells: Travel companions to metastases

Epithelial-mesenchymal transitions (EMTs) associated with metastatic progression may contribute to the generation of hybrid phenotypes capable of plasticity. This cellular plasticity would provide tumor cells with an increased potential to adapt to the different microenvironments encountered during metastatic spread. Understanding how EMT may functionally equip circulating tumor cells (CTCs) with an enhanced competence to survive in the bloodstream and niche in the colonized organs has thus become a major cancer research axis. We summarize here clinical data with CTC endpoints involving EMT. We then review the work functionally linking EMT programs to CTC biology and deciphering molecular EMT-driven mechanisms supporting their metastatic competence. Developmental Dynamics 247:432-450, 2018. © 2017 Wiley Periodicals, Inc.

Resveratrol suppresses pulmonary tumor metastasis by inhibiting platelet-mediated angiogenic responses

BACKGROUND

To explore the impact of Resveratrol (RSV) on the angiogenic potential of activated platelets and to elucidate the underlying mechanism.

METHODS

Vascular endothelial growth factor concentrations were measured by enzyme-linked immunosorbent assay. Capillary tube formation assay was used to examine the impact of RSV on the angiogenic potential of activated platelets. The levels of cyclic adenosine monophosphate and cyclic guanosine monophosphate (cGMP) in the supernatant were evaluated using corresponding enzyme-linked immunosorbent assay kits. Immunoblotting assays were used to determine the expression of vasodilator-stimulated phosphoprotein and Akt phosphorylation. A pulmonary metastasis experiment with male nude mice model was performed to test the effect of RSV on pulmonary metastasis and angiogenesis in vivo.

RESULTS

RSV inhibited platelets-mediated angiogenic responses induced by adenosine diphosphate (ADP)ADP through increased cGMP generation and cGMP-mediated vasodilator-stimulated phosphoprotein phosphorylation along with reduced intracellular Ca²⁺ mobilization. In addition, RSV attenuated the platelet secretion and angiogenic responses induced by A549 cells in vitro and suppressed A549 lung cancer metastasis and angiogenesis in nude mice.

CONCLUSIONS

RSV is a potential therapeutic drug for the prevention of tumor metastasis by interrupting the platelet-tumor cell amplification loop.

Inhibition of platelet function using liposomal nanoparticles blocks tumor metastasis

Extensive evidence has shown that platelets support tumor metastatic progression by inducing epithelial-mesenchymal transition of cancer cells and by shielding circulating tumor cells from immune-mediated elimination. Therefore, blocking platelet function represents a potential new avenue for therapy focused on eliminating metastasis. Here we show that liposomal nanoparticles bearing the tumor-homing pentapeptide CREKA (Cys-Arg-Glu-Lys-Ala) can deliver a platelet inhibitor, ticagrelor, into tumor tissues to specifically inhibit tumor-associated platelets. The drug-loaded nanoparticles (CREKA-Lipo-T) efficiently blocked the platelet-induced acquisition of an invasive phenotype by tumor cells and inhibited platelet-tumor cell interaction in vitro. Intravenously administered CREKA-Lipo-T effectively targeted tumors within 24 h, and inhibited tumor metastasis without overt side effects. Thus, the CREKA-Lipo formulation provides a simple strategy for the efficient delivery of anti-metastatic drugs and shows considerable promise as a platform for novel cancer therapeutics.

Gemcitabine-induced thrombocytosis as a potential predictive factor in non-small cell lung cancer: analysis of 318 patients

INTRODUCTION

In spite of the progress in the treatment of non-small-cell lung cancer (NSCLC), the majority of patients with advanced disease still receive chemotherapy. Gemcitabine alone or combined with a platinum compound is a valid option. Thrombocytosis is a recognized prognostic factor in lung cancer and an adverse event that may occur during gemcitabine infusion.

METHODS

We retrospectively evaluated all patients with NSCLC treated with first-line gemcitabine-based chemotherapy in two Italian hospitals. We assessed the onset of thrombocytosis within the third cycle of therapy and the relation between thrombocytosis and survival.

RESULTS

We included 318 patients. Thrombocytosis occurred in 156 patients (49.1%). Median progression-free survival (PFS) was 5.6 months (95% CI, 4.7-6.9 months) in patients who developed thrombocytosis versus 6 months (95% CI, 5.1-7.2 months) in patients without thrombocytosis (p = 0.21). Median overall survival (OS) was 11.2 months (95% CI, 9.8-13.4 months) in patients with thrombocytosis versus 12 months (95% CI, 10.1-14.4 months) in patients without thrombocytosis (p = 0.25). We observed no difference in terms of PFS or OS according to age, sex, stage, chemotherapy (single-agent versus combination chemotherapy) and thrombocytosis.

CONCLUSIONS

Thrombocytosis is neither a prognostic nor a predictive factor for PFS or OS in patients with advanced NSCLC treated with first-line gemcitabine-based chemotherapy.

The nuts and bolts of the platelet release reaction

Secretion is essential to many of the roles that platelets play in the vasculature, e.g., thrombosis, angiogenesis, and inflammation, enabling platelets to modulate the microenvironment at sites of vascular lesions with a myriad of bioactive molecules stored in their granules. Past studies demonstrate that granule cargo release is mediated by Soluble NSF Attachment Protein Receptor (SNARE) proteins, which are required for granule-plasma membrane fusion. Several SNARE regulators, which control when, where, and how the SNAREs interact, have been identified in platelets. Additionally, platelet SNAREs are controlled by post-translational modifications, e.g., phosphorylation and acylation. Although there have been many recent insights into the mechanisms of platelet secretion, many questions remain: have we identified all the important regulators, does calcium directly control the process, and is platelet secretion polarized. In this review, we focus on the mechanics of platelet secretion and discuss how the secretory machinery functions in the pathway leading to membrane fusion and cargo release.

Preoperative platelet count improves the prognostic prediction of the FIGO staging system for operable cervical cancer patients

BACKGROUND

Increased platelet has been identified as an independent and unfavorable prognostic indicator in various cancers including cervical cancer. In our study, the prognostic value of preoperative platelet count combining with FIGO (International Federation of Gynecology and Obstetrics) stage in patients with operable cervical cancer was investigated.

METHODS

A large cohort study including 800 operable cervical cancer patients was conducted from May 2005 to December 2012. Cancer-related biomarkers such as platelet count, hematocrit, hemoglobin, RDW was evaluated together with FIGO staging system in stage IA1-IIA2 cervical cancer patients. The prediction validity of platelet together with FIGO stage was then evaluated by receiver operating characteristic (ROC) curve, and the areas under the curve (AUCs) were compared by Z test.

RESULTS

Univariate cox proportional hazard analysis demonstrated that hematocrit, platelet count, hemoglobin, FIGO stage, tumor differentiation, PLN (pelvic lymph node metastasis), LVSI (vascular lymph node invasion) were associated with overall survival (OS) and disease free survival (DFS), instead of RDW (red cell distribution width), age and histological subtype. Multivariate analysis demonstrated that preoperative platelet and FIGO stage were independent predictors for OS and DFS in cervical cancer. Furthermore, significant improvements were found after the combination of platelet count and FIGO stage in predicting OS and DFS for cervical cancer patients (P=0.0128 and P=0.0385, respectively).

CONCLUSIONS

Combination of platelet count and FIGO stage improved the prediction performance of FIGO staging and provide additional risk stratification for operable cervical cancer patients.

Is Autoimmune Thrombocytopenia Itself the Primary Disease in the Presence of Second Diseases Data from a Long-Term Observation

BACKGROUND

Dependent on the absence or presence of associated diseases, autoimmune thrombocytopenia (ITP) can be classified as primary or secondary form. The manifestation of the associated diseases is not temporally defined and may occur during observation. Thus the question which disease is the primary one remains unanswered.

METHODS

All 386 patients included in this study were treated by a single primary physician between 1996 and 2015 at the Charité Berlin and met current ITP criteria. Medical records and investigations were reviewed to assess diseases associated with ITP.

RESULTS

Initially, the vast majority of patients presented with primary ITP (isolated disease). Based on our findings, ITP was found to be associated with other abnormalities in most cases. These abnormalities included: positive direct antiglobulin test in 49 of 386 tested patients (13%), affections of the thyroid gland in 41 of 386 tested patients (11%), infections in 30 (8%), solid malignancies in 20 (5%) and hematological malignancies in 10 patients (3%), as well as many other miscellaneous diseases. Moreover, of 160 patients who did not receive prior intravenous immunoglobulin treatment, 40 (25%) showed antibody deficiency.

CONCLUSION

In conclusion, the incidence of 'true' ITP as a primary disease is less common than has yet been suggested. Additionally, there is evidence that ITP itself predispose affected subjects toward development of other diseases.

The Prognostic Role of the Platelet-Lymphocytes Ratio in Gastric Cancer: A Meta-Analysis

Background

Systemic inflammatory parameters, such as the elevator PLR (platelet-lymphocyte ratio), the NLR (neutrophil-lymphocyte ratio) and the platelet count (PLT), have been found to be associated with the prognosis in gastric cancer; however, these results, especially those relating to the PLR, remain inconsistent. So we aimed to evaluate the prognostic role of the PLR in gastric cancer by conducting and presenting the findings of this meta-analysis.

Methods

We conducted a systematic literature search in PubMed, Embase and the Cochrane Library to evaluate the prognostic value of the PLR in gastric cancer. The quality of the included studies was evaluated using the Newcastle Ottawa Quality Assessment Scale (NOS). The hazard ratio (HR) /Odds Ratio (OR) and its 95% confidence were pooled using a random effects model. A funnel plot based on overall survival was used to evaluate the publication bias.

Results

It total, 8 studies comprising 4513 patients with gastric cancer met the pre-setting inclusion criteria. In comparison to the normal PLR, an elevated PLR was correlated with a higher risk of lymph node metastasis with an OR of 1.50 (95% Cl:1.24–1.82; I² = 17%) and serosal invasion (T3 +T4) risk with an OR of 2.01 (95% Cl: 1.49–2.73; I² = 55%), and an elevated PLR also increased the advanced stage (III +IV) risk with an OR of 1.99 (95% Cl: 1.60–2.46; I² = 28%). An elevated PLR was not a reliable predictor for OS with an HR of 0.99 (95% CI: 0.9–1.1; I² = 12%).

Conclusions

An elevated PLR was correlated with a higher risk of lymph node metastasis, serosal invasion and advanced stage (III +IV) risk in gastric cancer; however, the PLR may not act as a negative predictor for the overall survival of gastric cancer.

Hunting for the ultimate liquid cancer biopsy - let the TEP dance begin

Non-protein coding RNAs in different flavors (miRNAs, piRNAs, snoRNAs, lncRNAs, SHOT-RNAs), exosomes, large oncosomes, exoDNA and now tumor-educated platelets (TEPs) have emerged as crucial signal transmitting, transporting and regulating devices of cells in the last two decades. They are also establishing themselves increasingly in the realm of tumor research. We are currently witnessing a mushrooming of candidate entities for diagnostic and prognostic cancer detection and characterization tests that could have a major impact on how this diverse group of diseases is initially spotted and subsequently treated in the near future. But how do the new kids on the block stand up to the more established circulating tumor cells (CTCs) and circulating tumor DNA (ctDNA)? Without question, much earlier disease detection would be expected to save numerous lives. With all these new players around, will we finally win a major battle in the never-ending war against cancer?

Targeting Selectins and Their Ligands in Cancer

Aberrant glycosylation is a hallmark of cancer cells with increased evidence pointing to a role in tumor progression. In particular, aberrant sialylation of glycoproteins and glycolipids has been linked to increased immune cell evasion, drug evasion, drug resistance, tumor invasiveness, and vascular dissemination, leading to metastases. Hypersialylation of cancer cells is largely the result of overexpression of sialyltransferases (STs). Differentially, humans express twenty different STs in a tissue-specific manner, each of which catalyzes the attachment of sialic acids via different glycosidic linkages (α2-3, α2-6, or α2-8) to the underlying glycan chain. One important mechanism whereby overexpression of STs contributes to an enhanced metastatic phenotype is via the generation of selectin ligands. Selectin ligand function requires the expression of sialyl-Lewis X and its structural isomer sialyl-Lewis A, which are synthesized by the combined action of alpha α1-3-fucosyltransferases, α2-3-sialyltransferases, β1-4-galactosyltranferases, and N-acetyl-β-glucosaminyltransferases. The α2-3-sialyltransferases ST3Gal4 and ST3Gal6 are critical to the generation of functional E- and P-selectin ligands and overexpression of these STs have been linked to increased risk of metastatic disease in solid tumors and poor outcome in multiple myeloma. Thus, targeting selectins and their ligands as well as the enzymes involved in their generation, in particular STs, could be beneficial to many cancer patients. Potential strategies include ST inhibition and the use of selectin antagonists, such as glycomimetic drugs and antibodies. Here, we review ongoing efforts to optimize the potency and selectivity of ST inhibitors, including the potential for targeted delivery approaches, as well as evaluate the potential utility of selectin inhibitors, which are now in early clinical development.