The effect of platelets on invasiveness and protease production of human mammary tumor cells

Efficacy and Safety of Aspirin for Prevention of Hepatocellular Carcinoma: An Updated Meta-analysis

BACKGROUND AND AIMS

Previous meta-analyses have shown that aspirin use may reduce the risk of hepatocellular carcinoma (HCC). However, the optimal dose, frequency, and duration of aspirin use or the safety and efficacy of aspirin in target populations for HCC prevention remain unclear. The study aim was to investigate the efficacy and safety of aspirin for prevention of HCC.

METHODS

Publications were retrieved by a comprehensive literature research of several databases. Based on a random-effects model, hazard ratios (HRs) and the corresponding 95% confidence intervals (CIs) were used to assess the pooled risk. The dose-response relationship between aspirin use and HCC risk was assessed with a restricted cubic spline model.

RESULTS

Twenty-two studies were included in the meta-analysis. Aspirin use was associated with a reduced risk of HCC (HR=0.64, 95% CI: 0.56-0.75). The effect was robust across sex and age; however, women and the non-elderly had the greatest benefit from aspirin use. The preventive effect was well reproduced in those with comorbidities. Daily use and long-term use of aspirin appeared to offer greater benefits. Aspirin 100 mg/d was associated with maximum reduction of HCC risk. Aspirin use did slightly increase the risk of bleeding (HR=1.14, 95% CI: 1.02-1.27).

CONCLUSIONS

Our meta-analysis confirmed that use of aspirin significantly reduced the incident risk of HCC. Regular and long-term aspirin use offers a greater advantage. Aspirin use was associated with an increased risk of bleeding. We recommend 100 mg/d aspirin as a feasible dose for further research on primary prevention of HCC in a broad at-risk population.

Tumor educated platelets, a promising source for early detection of hepatocellular carcinoma: Liquid biopsy an alternative approach to tissue biopsy

PURPOSE

Liver cancer is considered to be the sixth deadliest cancer worldwide. Hepatocellular carcinoma (HCC) is known to be the most prevalent type of liver cancer. The number of deaths due to HCC reported per year is on a constant rise especially in lesser developed countries. There are several contributing factors to this rise in number. Among other contributing factors is the late diagnosis of HCC. Patients are usually diagnosed when the disease reaches its advance stage. The present study was conducted with total 30 samples. It was designed for investigating the potential of TGF-β, NF-κβ, VEGF, AKT and PI3K as RNA based biomarkers in tumor educated platelets for early detection of HCC.

RESULTS

The results obtained from the transcriptional analysis revealed a significant high expression of TGF-β, NF-κβ, VEGF by 2.48, 2.35 and 2.78 folds respectively in comparison to the control. On the other hand, a decrease in expression by 0.6 and 0.65 folds was observed in AKT and PI3K respectively in comparison to controls. Although all selected RNA biomarkers showed promising potential to detect HCC however, AKT and PI3K were better able to detect early stage HCC.

CONCLUSIONS

The results obtained clearly indicate the increased expression of TGF-β, NF-κβ, VEGF in HCC patients. All these biomarkers are previously known for cancer initiation, progression and metastasis. The significant decrease in expression of AKT and PI3K in HCC patients needs further investigation. All the selected RNA biomarkers can be used for detection of HCC as they were able to distinguish HCC patients from controls successfully with AKT and PI3K showing better potential to detect early stage HCC. However, translational analysis for all these RNA biomarkers should be performed to gain further evidence for the ability of these biomarkers to be used for early HCC detection.

Serum neutrophil-to-lymphocyte ratio and platelet-to-lymphocyte ratio in prognosticating immunotherapy efficacy

Aim: To examine neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) in prognosticating immunotherapy efficacy. Methods: A retrospective study of 156 patients with metastatic melanoma and non-small-cell lung cancer on PD-1 inhibitors. Results: Baseline NLR ≥5 was associated with worse progression-free survival (hazard ratio [HR]: 1.53; 95% CI: 1.01-2.31; p = 0.043) but nonsignificant worse overall survival trend (HR: 1.51; 95% CI: 0.98-2.34; p = 0.064). PLR ≥200 was associated with worse overall survival (HR: 1.94; 95% CI: 1.29-2.94; p = 0.002) and worse progression-free survival (HR: 1.894; 95% CI: 1.27-2.82; p = 0.002). NLR or PLR are prognosticating factors regardless of cancer types, with PLR having a stronger association with outcomes than NLR. Conclusion: High baseline NLR or PLR (alone and combined) were associated with worse immunotherapy efficacy regardless of cancer type, indicating their potential role as an agnostic marker for immunotherapy efficacy.

CXCL12-CXCL4 heterodimerization prevents CXCL12-driven breast cancer cell migration

Despite improvements in cancer early detection and treatment, metastatic breast cancer remains deadly. Current therapeutic approaches have very limited efficacy in patients with triple negative breast cancer. Among the many mechanisms associated that contribute to cancer progression, signaling through the CXCL12-CXCR4 is an essential step in cancer cell migration. We previously demonstrated the formation of CXCL12-CXCL4 heterodimers (Carlson et al., 2013). Here, we investigated whether CXCL12-CXCL4 heterodimers alter tumor cell migration. CXCL12 alone dose-dependently promoted the MDA-MB 231 cell migration (p < .05), which could be prevented by blocking the CXCR4 receptor. The addition of CXCL4 inhibited the CXCL12-induced cell migration (p < .05). Using NMR spectroscopy, we identified the CXCL4-CXCL12 binding interface. Moreover, we generated a CXCL4-derived peptide homolog of the binding interface that mimicked the activity of native CXCL4 protein. These results confirm the formation of CXCL12-CXCL4 heterodimers and their inhibitory effects on the migration of breast tumors cells. These findings suggest that specific peptides mimicking heterodimerization of CXCL12 might prevent breast cancer cell migration.

Structure⁻Activity Relationship Study of Newly Synthesized Iridium-III Complexes as Potential Series for Treating Thrombotic Diseases

Platelets play a major role in hemostatic events and are associated with various pathological events, such as arterial thrombosis and atherosclerosis. Iridium (Ir) compounds are potential alternatives to platinum compounds, since they exert promising anticancer effects without cellular toxicity. Our recent studies found that Ir compounds show potent antiplatelet properties. In this study, we evaluated the in vitro antiplatelet, in vivo antithrombotic and structure⁻activity relationship (SAR) of newly synthesized Ir complexes, Ir-1, Ir-2 and Ir-4, in agonists-induced human platelets. Among the tested compounds, Ir-1 was active in inhibiting platelet aggregation induced by collagen; however, Ir-2 and Ir-4 had no effects even at their maximum concentrations of 50 μM against collagen and 500 μM against U46619-induced aggregation. Similarly, Ir-1 was potently inhibiting of adenosine triphosphate (ATP) release, calcium mobilization ([Ca²⁺]i) and P-selectin expression induced by collagen-induced without cytotoxicity. Likewise, Ir-1 expressively suppressed collagen-induced Akt, PKC, p38MAPKs and JNK phosphorylation. Interestingly, Ir-2 and Ir-4 had no effect on platelet function analyzer (PFA-100) collagen-adenosine diphosphate (C-ADP) and collagen-epinephrine (C-EPI) induced closure times in mice, but Ir-1 caused a significant increase when using C-ADP stimulation. Other in vivo studies revealed that Ir-1 significantly prolonged the platelet plug formation, increased tail bleeding times and reduced the mortality of adenosine diphosphate (ADP)-induced acute pulmonary thromboembolism in mice. Ir-1 has no substitution on its phenyl group, a water molecule (like cisplatin) can replace its chloride ion and, hence, the rate of hydrolysis might be tuned by the substituent on the ligand system. These features might have played a role for the observed effects of Ir-1. These results indicate that Ir-1 may be a lead compound to design new antiplatelet drugs for the treatment of thromboembolic diseases.

Prognostic value of platelet count and lymphocyte to monocyte ratio combination in stage IV non-small cell lung cancer with malignant pleural effusion

Introduction

A combination of platelet and lymphocyte to monocyte ratio (LMR) (abbreviated as COP-LMR) has been recently evaluated as systemic inflammatory marker for prognostication in lung cancer. While previous study on COP-LMR has evaluated its prognostic value in NSCLC patients who underwent curative resections, the combination of these two markers has not been evaluated in advanced NSCLC yet.

Objectives

In this study, we evaluated the prognostic value of COP-LMR in stage IV NSCLC with malignant pleural effusion under active anticancer treatment.

Methods

Between January 2012 and July 2016, 217 patients with stage IV NSCLC and MPE undergoing active anticancer treatment were selected for evaluation. If patients had both low LMR (< 2.47) and increased platelet (> 30.0 ×10⁴ mm-3), they were assigned to COP-LMR group 2. Patients with one parameter were assigned to COP-LMR group 1. If none, patients were assigned to COP-LMR group 0.

Results

Median overall survival (OS) (P < 0.001), progression free survival (PFS) (P < 0.001) and histological feature (P = 0.003) showed significant differences among COP-LMR groups. For COP-LMR groups 0, 1 and 2, median survival times were 35.9, 14.7 and 7.4 months, respectively, while median progression free times were 19.2, 13.3 and 7.4 months, respectively. Older age, male, low albumin, high CRP and high COP-LMR (0 vs 1, P = 0.021, hazard ratio (HR): 1.822, 95% confidence interval (CI): 1.096–3.027 and 0 vs 2, P = 0.003, HR: 2.464, 95% CI: 1.373–4.421) were independent predictive factors for shorter OS. Age, sex, histology, albumin, or CRP had no significant influence on PFS. High COP-LMR was the significant factor in predicting shorter PFS (0 vs 1, P = 0.116 and 0 vs 2, P = 0.007, HR: 1.902, 95% CI: 1.194–3.028).

Conclusions

A combination of pretreatment LMR and platelet levels can be used to predict short survival in stage IV NSCLC patients who underwent active anticancer treatment.

Possible Molecular Targets of Novel Ruthenium Complexes in Antiplatelet Therapy

In oncotherapy, ruthenium (Ru) complexes are reflected as potential alternatives for platinum compounds and have been proved as encouraging anticancer drugs with high efficacy and low side effects. Cardiovascular diseases (CVDs) are mutually considered as the number one killer globally, and thrombosis is liable for the majority of CVD-related deaths. Platelets, an anuclear and small circulating blood cell, play key roles in hemostasis by inhibiting unnecessary blood loss of vascular damage by making blood clot. Platelet activation also plays a role in cancer metastasis and progression. Nevertheless, abnormal activation of platelets results in thrombosis under pathological settings such as the rupture of atherosclerotic plaques. Thrombosis diminishes the blood supply to the heart and brain resulting in heart attacks and strokes, respectively. While currently used anti-platelet drugs such as aspirin and clopidogrel demonstrate efficacy in many patients, they exert undesirable side effects. Therefore, the development of effective therapeutic strategies for the prevention and treatment of thrombotic diseases is a demanding priority. Recently, precious metal drugs have conquered the subject of metal-based drugs, and several investigators have motivated their attention on the synthesis of various ruthenium (Ru) complexes due to their prospective therapeutic values. Similarly, our recent studies established that novel ruthenium-based compounds suppressed platelet aggregation via inhibiting several signaling cascades. Our study also described the structure antiplatelet-activity relationship (SAR) of three newly synthesized ruthenium-based compounds. This review summarizes the antiplatelet activity of newly synthesized ruthenium-based compounds with their potential molecular mechanisms.

Ir-6: A Novel Iridium (III) Organometallic Derivative for Inhibition of Human Platelet Activation

Platelet activation has been reported to play a major role in arterial thrombosis, cancer metastasis, and progression. Recently, we developed a novel Ir(III)-based compound, [Ir(Cp^∗)1-(2-pyridyl)-3-(4-dimethylaminophenyl)imidazo[1,5-a]pyridine Cl]BF₄ or Ir-6 and assessed its effectiveness as an antiplatelet drug. Ir-6 exhibited higher potency against human platelet aggregation stimulated by collagen. Ir-6 also inhibited ATP-release, intracellular Ca²⁺ mobilization, P-selectin expression, and the phosphorylation of phospholipase Cγ2 (PLCγ2), protein kinase C (PKC), v-Akt murine thymoma viral oncogene (Akt)/protein kinase B, and mitogen-activated protein kinases (MAPKs), in collagen-activated platelets. Neither the adenylate cyclase inhibitor SQ22536 nor the guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one significantly reversed the Ir-6-mediated inhibition of collagen-induced platelet aggregation. Moreover, Ir-6 did not considerably diminish OH radical signals in collagen-activated platelets or Fenton reaction solution. At 2 mg/kg, Ir-6 markedly prolonged the bleeding time in experimental mice. In conclusion, Ir-6 plays a crucial role by inhibiting platelet activation through the inhibition of signaling pathways, such as the PLCγ2-PKC cascade and the subsequent suppression of Akt and MAPK activation, thereby ultimately inhibiting platelet aggregation. Therefore, Ir-6 is a potential therapeutic agent for preventing or treating thromboembolic disorders or disrupting the interplay between platelets and tumor cells, which contributes to tumor cell growth and progression.

Molecular mechanisms of platelet activation and aggregation induced by breast cancer cells

Tumor cell-induced platelet aggregation represents a critical process both for successful metastatic spread of the tumor and for the development of thrombotic complications in cancer patients. To get further insights into this process, we investigated and compared the molecular mechanisms of platelet aggregation induced by two different breast cancer cell lines (MDA-MB-231 and MCF7) and a colorectal cancer cell line (Caco-2). All the three types of cancer cells were able to induce comparable platelet aggregation, which, however, was observed exclusively in the presence of CaCl₂ and autologous plasma. Aggregation was supported both by fibrinogen binding to integrin αIIbβ3 as well as by fibrin formation, and was completely prevented by the serine protease inhibitor PPACK. Platelet aggregation was preceded by generation of low amounts of thrombin, possibly through tumor cells-expressed tissue factor, and was supported by platelet activation, as revealed by stimulation of phospholipase C, intracellular Ca²⁺ increase and activation of Rap1b GTPase. Pharmacological inhibition of phospholipase C, but not of phosphatidylinositol 3-kinase or Src family kinases prevented tumor cell-induced platelet aggregation. Tumor cells also induced dense granule secretion, and the stimulation of the P2Y12 receptor by released ADP was found to be necessary for complete platelet aggregation. By contrast, prevention of thromboxane A₂ synthesis by aspirin did not alter the ability of all the cancer cell lines analyzed to induce platelet aggregation. These results indicate that tumor cell-induced platelet aggregation is not related to the type of the cancer cells or to their metastatic potential, and is triggered by platelet activation and secretion driven by the generation of small amount of thrombin from plasma and supported by the positive feedback signaling through secreted ADP.

Novel iridium (III)‑derived organometallic compound for the inhibition of human platelet activation

Since cisplatin achieved clinical success, transition metal platinum (Pt) drugs have been effectively used for the treatment of cancer. Iridium (Ir) compounds are considered to be potential alternatives to Pt compounds, as they possess promising anticancer effects with minor side effects. Platelet activation is associated with the metastasis and progression of cancer, and also with arterial thrombosis. Therefore, it is necessary to develop novel, effective antithrombotic agents. An Ir (III)-derived complex, [Ir (Cp*) 1-(2-pyridyl)-3-(3-me-thoxyphenyl)imidazo[1,5-a]pyridine Cl]BF₄ (Ir-3), was developed as a novel antiplatelet drug. Ir-3 exerted more potent inhibitory activity on platelet aggregation stimulated by collagen compared with other agonists, including thrombin. In collagen-activated platelets, Ir-3 also inhibited adenosine trisphosphate release, intracellular Ca⁺² mobilization and surface P-selectin expression, as well as the phosphorylation of phospholipase Cγ2 (PLCγ2), protein kinase C (PKC), protein kinase B (Akt) and c-Jun N-terminal kinase (JNK) 1, but not p38 mitogen-activated protein kinase or extracellular signal-regulated kinases. Ir-3 did not markedly affect phorbol 12, 13-dibutyrate-stimulated platelet aggregation. Neither the adenylate cyclase inhibitor SQ22536 nor the guanylate cyclase inhibitor 1H-[1, 2, 4] oxadiazolo [4,3-a]quinoxalin-1-one significantly reversed the Ir-3-mediated inhibition of platelet aggregation. Furthermore, Ir-3 had no considerable diminishing effects on OH radical signals in collagen-stimulated platelets or Fenton reaction solution. In conclusion, Ir-3 serves a novel function in the inhibition of platelet aggregation through inhibiting the PLCγ2-PKC cascade, and the subsequent suppression of Akt and JNK1 activation. Therefore, Ir-3 may be a potential novel therapeutic agent for the treatment of thromboembolic disorders, or the interplay between platelets and tumor cells which contributes to tumor cell proliferation and progression.

Activated platelets inhibit hepatocellular carcinoma cell differentiation and promote tumor progression via platelet-tumor cell binding

Lack of differentiation in hepatocellular carcinoma (HCC) is associated with increased circulating platelet size. We measured platelet activation and plasma adenosine diphosphate (ADP) levels in HCC patients based on differentiation status. Local platelet accumulation and platelet-hepatoma cell binding were measured using immunohistochemistry (IHC) or flow cytometry. Using a xenograft assay in NON/SCID mice, we tested the effects of the anti-platelet drug clopidogrel on platelet activation, platelet infiltration, platelet-tumor cell binding and tumor cell differentiation. HCC patients with poor differentiation status displayed elevated platelet activation and higher ADP levels. Platelets accumulated within poorly differentiated tissues and localized at hepatoma cell membranes. Platelet-tumor cell binding was existed in carcinoma tissues, largely mediated by P-selectin on platelets. NOD/SCID mice with xenograft tumors also exhibited increased platelet activation and platelet-tumor cell binding. Clopidogrel therapy triggered hepatoma cell differentiation by attenuating platelet activation and platelet-tumor cell binding. TCF4 knockdown promoted HepG-2 cell differentiation and inhibited tumor formation, and TCF4 could be the potential downstream target for clopidogrel therapy.

New Therapeutic Agent against Arterial Thrombosis: An Iridium(III)-Derived Organometallic Compound

Platelet activation plays a major role in cardio and cerebrovascular diseases, and cancer progression. Disruption of platelet activation represents an attractive therapeutic target for reducing the bidirectional cross talk between platelets and tumor cells. Platinum (Pt) compounds have been used for treating cancer. Hence, replacing Pt with iridium (Ir) is considered a potential alternative. We recently developed an Ir(III)-derived complex, [Ir(Cp*)1-(2-pyridyl)-3-(2-hydroxyphenyl)imidazo[1,5-a]pyridine Cl]BF₄ (Ir-11), which exhibited strong antiplatelet activity; hence, we assessed the therapeutic potential of Ir-11 against arterial thrombosis. In collagen-activated platelets, Ir-11 inhibited platelet aggregation, adenosine triphosphate (ATP) release, intracellular Ca²⁺ mobilization, P-selectin expression, and OH· formation, as well as the phosphorylation of phospholipase Cγ2 (PLCγ2), protein kinase C (PKC), mitogen-activated protein kinases (MAPKs), and Akt. Neither the adenylate cyclase inhibitor nor the guanylate cyclase inhibitor reversed the Ir-11-mediated antiplatelet effects. In experimental mice, Ir-11 prolonged the bleeding time and reduced mortality associated with acute pulmonary thromboembolism. Ir-11 plays a crucial role by inhibiting platelet activation through the inhibition of the PLCγ2–PKC cascade, and the subsequent suppression of Akt and MAPK activation, ultimately inhibiting platelet aggregation. Therefore, Ir-11 can be considered a new therapeutic agent against either arterial thrombosis or the bidirectional cross talk between platelets and tumor cells.

Platelets and matrix metalloproteinases

Matrix metalloproteinases (MMPs) and their inhibitors essentially contribute to a variety of pathophysiologies by modulating cell migration, tissue degradation and inflammation. Platelet-associated MMP activity appears to play a major role in these processes. First, platelets can concentrate leukocyte-derived MMP activity to sites of vascular injury by leukocyte recruitment. Second, platelets stimulate MMP production in e.g. leukocytes, endothelial cells, or tumour cells by direct receptor interaction or/and by paracrine pathways. Third, platelets synthesise and secrete a variety of MMPs including MMP-1, MMP-2, MMP-3, and MMP-14 (MT1-MMP), and potentially MMP-9 as well as the tissue inhibitors of metalloproteinase (TIMPs). This review focuses on platelet-derived and platelet-induced MMPs and their inhibitors.

Prognostic value of combination of preoperative platelet count and mean platelet volume in patients with resectable non-small cell lung cancer

The aim of the present study was to investigate the prognostic value of the combination of preoperative platelet count (PLT) and mean platelet volume (MPV) in patients with primary operable non-small cell lung cancer (NSCLC). We retrospectively analysed data from 546 patients with NSCLC who underwent complete resection at our institution from 2006 to 2010. Patients’ clinical characteristics and laboratory test data at initial diagnosis were collected. Both preoperative PLT and MPV (COP-MPV) were calculated on the basis of the data obtained using the recommended cut-off values of 300 × 10⁹ L⁻¹ and 11.0 fL, respectively. Patients with both an elevated PLT (≥300× 10⁹ L⁻¹) and a decreased MPV (<11.0 fL) were assigned a score of 2, and patients showing one or neither were allocated a score of 1 or 0, respectively. Multivariate analysis of the 9 clinical laboratory variables selected by univariate analysis revealed that preoperative COP-MPV was a significantly independent prognostic factor for overall survival (OS) (hazard ratio, 1.775; 95% confidence interval, 1.500–2.101; P< 0.001) and disease-free survival (DFS) (hazard ratio, 1.719; 95% confidence interval, 1.454–2.033; P< 0.001). In subgroup analyses for tumour pathological stage (I/II/IIIA) patients, we found that the level of COP-MPV was significantly associated with OS and DFS in each subgroup (P< 0.001, P< 0.001, P<0.001 for OS and P<0.001, P< 0.001, P=0.001 for DFS, respectively). In conclusion, the preoperative COP-MPV is a promising predictor of postoperative survival in patients with NSCLC and could classify these patients into three independent groups before surgery.

Antiplatelet Activity of a Newly Synthesized Novel Ruthenium (II): A Potential Role for Akt/JNK Signaling

In oncotherapy, ruthenium complexes are considered as potential alternatives for platinum compounds, and have been proved as promising anticancer drugs with high efficacy and lesser side effects. Platelet activation plays a major role in cancer metastasis and progression. Hence, this study explored the effect of a newly synthesized ruthenium complex, [Ru(η⁶-cymene)(L)Cl]BF₄(TQ5), where L = 4-phenyl-2-pyridin-2-yl-quinazoline), on human platelet activation. TQ5 (3–5 µM) inhibited concentration-dependent collagen-induced platelet aggregation in washed human platelets. However, this compound only inhibited platelet aggregation at a maximum concentration of 500 and 100 µM against thrombin and 9,11-dideoxy-11α, 9α-epoxymethanoprostaglandin (U46619)-induced stimulation, respectively. TQ5 inhibited collagen-induced ATP release and calcium mobilization ([Ca²⁺]_i), without inducing cell cytotoxicity. In addition, neither SQ22536, an adenylate cyclase inhibitor, nor 1H-[1,2,4] oxadiazolo [4,3-a]quinoxalin-1-one (ODQ), a guanylate cyclase inhibitor, significantly reversed the TQ5-mediated inhibition of platelet aggregation. TQ5 inhibited the collagen-induced phosphorylation of protein kinase B (Akt) and c-Jun N-terminal kinase (JNK), but did not effectively inhibit extracellular signal-regulated kinase 1/2 (ERK1/2) and p38-mitogen-activated protein kinase (p38-MAPK) in human platelets. Additionally, TQ5 significantly prolonged the closure time in whole blood and increased the occlusion time of thrombotic platelet plug formation in mice. This study demonstrates, for the first time, that a newly synthesized ruthenium complex, TQ5, exhibits potent antiplatelet activity by hindering ATP release and [Ca²⁺]_i, and by decreasing the activation of Akt/JNK signals. Together, these results suggest that TQ5 could be developed as a therapeutic agent that helps prevent or treat thromboembolic disorders, since it is found to be potently more effective than a well-established antithrombotic aspirin.

Matrix Metalloproteinases and Platelet Function

Platelets contain and release several matrix metalloproteinases (MMPs) and their tissue inhibitors of matrix metalloproteinases (TIMPs), including MMP-1, -2, -3, -9, and -14 and TIMP-1, -2, and -4. Although devoid of a nucleus, platelets also synthesize TIMP-2 upon activation. Platelet-released MMPs/TIMPs, as well as MMPs generated by other cells within the cardiovascular system, modulate platelet function in health and disease. In particular, a normal hemostatic platelet response to vessel wall injury may be transformed into pathologic thrombus formation by the release from platelets and/or by the local generation of some MMPs. Moreover, platelets may localize the production of leukocyte-derived MMPs to sites of vascular damage, contributing to atherosclerosis development and complications and to arterial aneurysm formation. Finally, the interaction between platelets and tumor cells is strongly influenced by MMPs/TIMPs. All these mechanisms are emerging as important in atherothrombosis, inflammatory disease, and cancer growth and dissemination. Increasing knowledge of these mechanisms may open the way to novel therapeutic approaches.

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.

Paraneoplastic thrombocytosis independently predicts poor prognosis in patients with locally advanced pancreatic cancer

BACKGROUND AND AIMS

Platelets are believed to promote tumor growth and metastasis but their prognostic role in locally advanced pancreatic cancer (LAPC) remains largely unknown. We assessed whether pretreatment platelet counts independently predict survival outcomes in patients with LAPC treated with chemoradiation (CRT).

METHODS

We retrospectively reviewed the MD Anderson pancreatic cancer database and identified 199 patients with LAPC treated with CRT between 2006 and 2012. Induction chemotherapy was used prior to consolidative CRT in 177 (89%) patients. Median radiation dose was 50.4 Gy. Concurrent radiosensitizers were gemcitabine-based (13%) or capecitabine-based (84%) regimens. Actuarial univariate and multivariate statistical methods were used to determine significant prognostic factors for overall survival (OS) and progression-free survival (PFS) calculated from the start of treatment.

RESULTS

Median follow-up was 9.9 months. Median OS and PFS durations were 17.7 and 10.7 months, respectively. On univariate analysis, platelet count > 300 K/μl, KPS ≤ 80, ≥ 5% weight loss and pretreatment CA19-9 above the median were associated with inferior OS or PFS. Median OS was lower in patients with platelet count > 300 K/μl compared to patients with platelet count ≤ 300 K/μl (10.2 vs. 19 months; p = 0.0002). Corresponding median PFS times were 7.8 months and 11.1 months (p = 0.004), respectively. On multivariate analysis, platelet count > 300 K/μl (p = 0.012), ≥ 5% weight loss (p = 0.002) and elevated pretreatment CA19-9 (p = 0.005) were independent prognostic factors for OS. Platelet count > 300 K/μl (p = 0.03) and KPS ≤ 80 (p = 0.05) independently predicted PFS.

CONCLUSIONS

Our analysis suggests that pretreatment thrombocytosis independently predicts inferior OS and PFS in LAPC.

Activation of tumour cell ECM degradation by thrombin-activated platelet membranes: potentially a P-selectin and GPIIb/IIIa-dependent process

The promotion of tumour metastasis by platelets may occur through several mechanisms including the induction of a more metastatic phenotype in tumour cells and assisted extravasation of circulating tumour cells. Whilst the mechanisms underlying platelet-assisted extravasation have been extensively studied, much less attention has been paid to the mechanisms underlying platelet promotion of an aggressive phenotype within a tumour cell population. Herein, we demonstrate in vitro that MDA-MB-231 breast carcinoma cells incubated with washed thrombin-activated platelet membranes adopt a Matrigel-degrading phenotype in a dose- and contact time-dependent manner. The same phenotypic change was observed with three other human tumour cell lines of diverse anatomical origin. Moreover, tumour cell lines that had been cultured with washed thrombin-activated platelet membranes had a greater metastatic capacity when injected into mice. This in vivo effect was reliant upon a co-incubation period of >2 h implying a mechanism involving more than platelet membrane binding that occurred within 5 min. Upon further investigation it was found that simultaneous blocking of the platelet-membrane proteins P-selectin and GPIIb/IIIa prevented interactions between platelet membranes and MDA-MB-231 cells but also significantly reduced the ability of tumour cells to degrade Matrigel. These results confirm that platelets induce a more aggressive phenotype in tumour cells but also identify the platelet proteins involved in this effect. P-selectin and GPIIb/IIIa also play a role in assisting tumour cell extravasation and, thus, are ideal targets for the therapeutic intervention of both stages of platelet-assisted metastasis.

Platelets, coagulation and fibrinolysis in breast cancer progression

The progression of breast cancer from early-stage to metastatic disease results from a series of events during which malignant cells invade and travel within the bloodstream to distant sites, leading to a clonogenic accumulation of tumor cells in non-breast tissue. While mechanistically complex, an emerging literature supports hemostatic elements as an important patient factor that facilitates the metastatic potential of breast cancer. Hemostatic elements involved include platelets, coagulation, and fibrinolysis. Key steps in breast tumor progression, including cellular transformation, proliferation, tumor cell survival, and angiogenesis, can be mediated by components of the hemostatic system. Thus, the hemostatic system provides potential targets for novel therapeutic approaches to breast cancer therapy with drugs in current use and in development. The present article provides a comprehensive overview of the evidence and mechanisms supporting the roles played by platelets, coagulation activation, and the fibrinolytic system in breast cancer progression.

Metastasis review: from bench to bedside

Cancer is the final result of uninhibited cell growth that involves an enormous group of associated diseases. One major aspect of cancer is when cells attack adjacent components of the body and spread to other organs, named metastasis, which is the major cause of cancer-related mortality. In developing this process, metastatic cells must successfully negotiate a series of complex steps, including dissociation, invasion, intravasation, extravasation, and dormancy regulated by various signaling pathways. In this review, we will focus on the recent studies and collect a comprehensive encyclopedia in molecular basis of metastasis, and then we will discuss some new potential therapeutics which target the metastasis pathways. Understanding the new aspects on molecular mechanisms and signaling pathways controlling tumor cell metastasis is critical for the development of therapeutic strategies for cancer patients that would be valuable for researchers in both fields of molecular and clinical oncology.

Nitric oxide-matrix metaloproteinase-9 interactions: biological and pharmacological significance--NO and MMP-9 interactions

Nitric oxide (NO) and matrix metalloproteinase 9 (MMP-9) levels are found to increase in inflammation states and in cancer, and their levels may be reciprocally modulated. Understanding interactions between NO and MMP-9 is of biological and pharmacological relevance and may prove crucial in designing new therapeutics. The reciprocal interaction between NO and MMP-9 have been studied for nearly twenty years but to our knowledge, are yet to be the subject of a review. This review provides a summary of published data regarding the complex and sometimes contradictory effects of NO on MMP-9. We also analyse molecular mechanisms modulating and mediating NO-MMP-9 interactions. Finally, a potential therapeutic relevance of these interactions is presented.

Platelets, selectins, and the control of tumor metastasis

The significant role of platelets and P-selectin in assisting tumor cell metastasis to the lungs has been frequently reported and reviewed. However, evidence recently has come to light on other pro-metastatic mechanisms of platelets beyond that of tumor cell protection from immune cell attack and aiding extravasation, such as promoting epithelial to mesenchymal transition in tumor cells and conveying signals from the primary tumor to distant tissues that optimize conditions for metastasis. Moreover, the role of platelets and selectins in hematogenous metastasis to frequently targeted organs other than the lungs has been less well examined. This review aims to summarize the literature on the roles of platelets in all stages of the metastatic process and to examine the participation of platelets and selectins in hematogenous metastasis to the lungs, liver, bone, and brain. In the light of the available evidence, potential therapeutic avenues for the control of metastasis are also discussed.

Overview of platelet physiology: its hemostatic and nonhemostatic role in disease pathogenesis

Platelets are small anucleate cell fragments that circulate in blood playing crucial role in managing vascular integrity and regulating hemostasis. Platelets are also involved in the fundamental biological process of chronic inflammation associated with disease pathology. Platelet indices like mean platelets volume (MPV), platelets distributed width (PDW), and platelet crit (PCT) are useful as cheap noninvasive biomarkers for assessing the diseased states. Dynamic platelets bear distinct morphology, where α and dense granule are actively involved in secretion of molecules like GPIIb , IIIa, fibrinogen, vWf, catecholamines, serotonin, calcium, ATP, ADP, and so forth, which are involved in aggregation. Differential expressions of surface receptors like CD36, CD41, CD61 and so forth have also been quantitated in several diseases. Platelet clinical research faces challenges due to the vulnerable nature of platelet structure functions and lack of accurate assay techniques. But recent advancement in flow cytometry inputs huge progress in the field of platelets study. Platelets activation and dysfunction have been implicated in diabetes, renal diseases, tumorigenesis, Alzheimer's, and CVD. In conclusion, this paper elucidates that platelets are not that innocent as they keep showing and thus numerous novel platelet biomarkers are upcoming very soon in the field of clinical research which can be important for predicting and diagnosing disease state.

Platelets and cancer: a casual or causal relationship: revisited

Human platelets arise as subcellular fragments of megakaryocytes in bone marrow. The physiologic demand, presence of disease such as cancer, or drug effects can regulate the production circulating platelets. Platelet biology is essential to hemostasis, vascular integrity, angiogenesis, inflammation, innate immunity, wound healing, and cancer biology. The most critical biological platelet response is serving as "First Responders" during the wounding process. The exposure of extracellular matrix proteins and intracellular components occurs after wounding. Numerous platelet receptors recognize matrix proteins that trigger platelet activation, adhesion, aggregation, and stabilization. Once activated, platelets change shape and degranulate to release growth factors and bioactive lipids into the blood stream. This cyclic process recruits and aggregates platelets along with thrombogenesis. This process facilitates wound closure or can recognize circulating pathologic bodies. Cancer cell entry into the blood stream triggers platelet-mediated recognition and is amplified by cell surface receptors, cellular products, extracellular factors, and immune cells. In some cases, these interactions suppress immune recognition and elimination of cancer cells or promote arrest at the endothelium, or entrapment in the microvasculature, and survival. This supports survival and spread of cancer cells and the establishment of secondary lesions to serve as important targets for prevention and therapy.

Discovery and validation of urinary biomarkers for detection of renal cell carcinoma

INTRODUCTION

Renal cell carcinoma (RCC) is often accompanied by non-specific symptoms. The increase of incidentally discovered small renal masses also presents a diagnostic dilemma. This study investigates whether RCC-specific peptides with diagnostic potential can be detected in urine and whether a combination of such peptides could form a urinary screening tool.

MATERIALS AND METHODS

For the discovery of RCC-specific biomarkers, we have employed CE-MS to analyze urine samples from patients with RCC (N=40) compared to non-diseased controls (N=68).

RESULTS AND DISCUSSION

86 peptides were found to be specifically associated to RCC, of which sequence could be obtained for 40. A classifier based on these peptides was evaluated in an independent set of 76 samples, resulting in 80% sensitivity and 87% specificity. The specificity of the marker panel was further validated in a historical dataset of 1077 samples including age-matched controls (N=218), patients with related cancer types and renal diseases (N=859). In silico protease prediction based on the cleavage sites of differentially excreted peptides, suggested modified activity of certain proteases including cathepsins, ADAMTS and kallikreins some of which were previously found to be associated to RCC.

CONCLUSIONS

RCC can be detected with high accuracy based on specific urinary peptides.

BIOLOGICAL SIGNIFICANCE

Clear cell renal cell carcinoma (RCC) has the highest incidence among the renal malignancies, often presenting non-specific or no symptoms at all. Moreover, with no diagnostic marker being available so far, almost 30% of the patients are diagnosed with metastatic disease and 30-40% of the patients initially diagnosed with localized tumor relapse. These facts introduce the clinical need of early diagnosis. This study is focused on the investigation of a marker model based on urinary peptides, as a tool for the detection of RCC in selected patients at risk. Upon evaluation of the marker model in an independent blinded set of 76 samples, 80% sensitivity and 87% specificity were reported. An additional dataset of 1077 samples was subsequently employed for further evaluation of the specificity of the classifier.

Platelet CLEC-2 and podoplanin in cancer metastasis

It has long been recognised that the function of platelets in health and disease span far beyond their roles in haemostasis and thrombosis. The observation that tumour cells induce platelet aggregation was followed by extensive experimental evidence linking platelets to cancer progression. Aggregated platelets coat tumour cells during their transit through the bloodstream and mediate adherence to vascular endothelium, protection from shear stresses, evasion from immune molecules, and release of an array of bioactive molecules that facilitate tumour cell extravasation and growth at metastatic sites. The sialyated membrane glycoprotein podoplanin is found on the leading edge of tumour cells and is thought to influence their migratory and invasive properties. Podoplanin elicits powerful platelet aggregation and is the endogenous ligand for the platelet C-type lectin receptor, CLEC-2, which itself regulates podoplanin signalling. Here, the bidirectional relationship between CLEC-2 and podoplanin is described and considered in the context of tumour growth and metastasis.

Significant downregulation of platelet gene expression in metastatic lung cancer

Platelets play a major role in the metastatic dissemination of tumor cells in vivo . Recent evidence reveals megakaryocyte-derived platelet pre-mRNA is spliced to mRNA and then translated into functional proteins in response to external stimulation. Employing a human lung cancer model, we hypothesized a subset of megakaryocyte/platelet genes exists that are significantly over or underexpressed in metastasis compared with noncancer. Microarray analysis employing platelet mRNA followed by unsupervised hierarchical clustering revealed an expression profile that includes decreased expression of 197 of the 200 platelet genes with the most altered expression (p < 1.0 × 10(-4)). Among the 608 splicing events identified between the metastasis and negative control groups, 33 highly variable genes were identified with between 3 and 13 splicing events each. In conclusion, this preliminary study reveals a platelet-based gene expression signature that differentiates metastatic lung cancer from negative controls on the basis of decreased expression of 197 of the 200 genes with the most altered expression levels. Further study may yield a prognostic tool for future metastasis among subsets of early stage lung cancer patients.

The platelet contribution to cancer progression

Traditionally viewed as major cellular components in hemostasis and thrombosis, the contribution of platelets to the progression of cancer is an emerging area of research interest. Complex interactions between tumor cells and circulating platelets play an important role in cancer growth and dissemination, and a growing body of evidence supports a role for physiologic platelet receptors and platelet agonists in cancer metastases and angiogenesis. Platelets provide a procoagulant surface facilitating amplification of cancer-related coagulation, and can be recruited to shroud tumor cells, thereby shielding them from immune responses, and facilitate cancer growth and dissemination. Experimental blockade of key platelet receptors, such as GP1b/IX/V, GPIIbIIIa and GPVI, has been shown to attenuate metastases. Platelets are also recognized as dynamic reservoirs of proangiogenic and anti-angiogenic proteins that can be manipulated pharmacologically. A bidirectional relationship between platelets and tumors is also seen, with evidence of 'tumor conditioning' of platelets. The platelet as a reporter of malignancy and a targeted delivery system for anticancer therapy has also been proposed. The development of platelet inhibitors that influence malignancy progression and clinical testing of currently available antiplatelet drugs represents a promising area of targeted cancer therapy.

Selectins promote tumor metastasis

Cancer metastasis is facilitated by cell-cell interactions between cancer cells and endothelial cells in distant tissues. In addition, cancer cell interactions with platelets and leukocytes contribute to cancer cell adhesion, extravasation, and the establishment of metastatic lesions. Selectins are carbohydrate-binding molecules that bind to sialylated, fucosylated glycan structures, and are found on endothelial cells, platelets and leukocytes. There are three members of the selectin family: P-selectin expressed on activated platelets and endothelial cells, L-selectin present on leukocytes and E-selectin expressed on activated endothelial cells. Besides the accepted roles of selectins in physiological processes, such as inflammation, immune response and hemostasis, there is accumulating evidence for the potential of selectins to contribute to a number of pathophysiological processes, including cancer metastasis. Cancer cell interactions with selectins are possible due to a frequent presence of carbohydrate determinants--selectin ligands on the cell surface of tumor cells from various type of cancer. The degree of selectin ligand expression by cancer cells is well correlated with metastasis and poor prognosis for cancer patients. Initial adhesion events of cancer cells facilitated by selectins result in activation of integrins, release of chemokines and are possibly associated with the formation of permissive metastatic microenvironment. While E-selectin has been evaluated as one of the initiating adhesion events during metastasis, it is becoming apparent that P-selectin and L-selectin-mediated interactions significantly contribute to this process as well. In this review we discuss the current evidence for selectins as potential facilitators of metastasis.

Platelet alpha-granules: basic biology and clinical correlates

alpha-Granules are essential to normal platelet activity. These unusual secretory granules derive their cargo from both regulated secretory and endocytotic pathways in megakaryocytes. Rare, inheritable defects of alpha-granule formation in mice and man have enabled identification of proteins that mediate cargo trafficking and alpha-granule formation. In platelets, alpha-granules fuse with the plasma membrane upon activation, releasing their cargo and increasing platelet surface area. The mechanisms that control alpha-granule membrane fusion have begun to be elucidated at the molecular level. SNAREs and SNARE accessory proteins that control alpha-granule secretion have been identified. Proteomic studies demonstrate that hundreds of bioactive proteins are released from alpha-granules. This breadth of proteins implies a versatile functionality. While initially known primarily for their participation in thrombosis and hemostasis, the role of alpha-granules in inflammation, atherosclerosis, antimicrobial host defense, wound healing, angiogenesis, and malignancy has become increasingly appreciated as the function of platelets in the pathophysiology of these processes has been defined. This review will consider the formation, release, and physiologic roles of alpha-granules with special emphasis on work performed over the last decade.

Activated platelets enhance ovarian cancer cell invasion in a cellular model of metastasis

Increased platelet counts and systemic coagulation activation are associated with ovarian cancer progression. Platelet activation occurs in the tumor microenvironment and may influence local invasion and metastasis. We used a cellular model of tumor invasion to investigate the effect of activated platelets on the human ovarian cancer cell line, SKOV3. SKOV3 cells were exposed to washed, thrombin receptor activating peptide (TRAP)-activated or TRAP-naïve platelets under various experimental conditions, and tumor cell invasion was assayed in Matrigel chambers. The effect of platelets on the content of urokinase plasminogen activator (uPA) and VEGF in SKOV3 cell conditioned medium was measured using an ELISA assay. TRAP-activated platelets stimulated a dose-dependent increase in SKOV3 cell invasion. Exposure to activated platelet membranes and to soluble proteins contained in activated platelet releasate both contributed to the observed increase in invasion. The inhibition of platelet activation with prostaglandin E1 (PGE(1)) attenuated the invasive capacity of SKOV3 cells. Exposure to platelets resulted in significantly increased uPA and VEGF content of SKOV3 cell conditioned medium. Activated platelets enhance SKOV3 human ovarian cancer cell invasion through Matrigel and increase the amount of uPA and VEGF secreted into SKOV3 cell conditioned medium. If generalizable to additional cell lines and human disease, this observation may partially explain the adverse prognosis associated with thrombocytosis in ovarian cancer. Platelets, therefore, may represent a potential target for therapeutic intervention in human ovarian cancer.

The role of platelet activation in tumor metastasis

Platelets are highly reactive components of the circulatory system, which exert not only haemostatic activity but also contribute to the modulation of various pathological conditions including inflammation, atherosclerosis and cancer metastasis through the release of cytokines, chemokines and the presentation of several adhesion molecules. During cancer metastasis, the formation of platelet-tumor cell aggregates in the circulation facilitates immune evasion and the microvascular arrest of tumor cells at distant sites. Several adhesion molecules, such as integrins and glycoproteins, were shown to be involved in this process. Recent findings indicate that P-selectin is another main mediator of platelet-tumor cell interactions. Other effects of activated platelets on cancer progression are associated with a release of platelet-derived factors stimulating tumor growth and angiogenesis. Any interference in platelet-tumor cell interactions resulted in attenuation of cancer metastasis. The well recognized, albeit not fully characterized function of platelets during cancer progression defines platelets as potential targets for cancer therapy. Specifically, the rapid expression of P-selectin on the cell surface of activated platelets and its strong association with metastasis provide a rationale for P-selectin inhibition as an antimetastatic treatment.

Tamoxifen and aromatase inhibitors differentially affect vascular endothelial growth factor and endostatin levels in women with breast cancer

PURPOSE

Circulating and cellular proangiogenic and antiangiogenic proteins such as vascular endothelial growth factor (VEGF) and endostatin contribute to the local angiogenic balance. We explored the effects of tamoxifen and aromatase inhibitors on concentrations of VEGF and endostatin in plasma, serum, and platelet releasate (induced by platelet activation).

EXPERIMENTAL DESIGN

VEGF and endostatin concentrations were measured with a quantitative immunoassay before and after 1 to 5 weeks of treatment in 30 women with breast cancer treated with either tamoxifen (n = 14) or aromatase inhibitors (n = 16). Platelet activation was induced by a thrombin receptor agonist.

RESULTS

Tamoxifen therapy resulted in an increase in platelet releasate concentrations of VEGF (P = 0.01) but no change in plasma VEGF. In contrast, aromatase inhibitor therapy did not affect serum, plasma, or platelet releasate VEGF. In univariate analysis, aspirin use attenuated the tamoxifen-associated increase in VEGF in the platelet releasate and decreased serum levels of VEGF (P = 0.03). Aromatase inhibitor therapy resulted in a decrease in serum endostatin concentrations (P = 0.04), whereas plasma concentrations of endostatin tended to be higher during treatment with aromatase inhibitors (P = 0.06). Tamoxifen therapy resulted in no change in serum or plasma endostatin concentrations. Platelet releasate concentrations of endostatin did not change with either treatment. Interindividual variability was noted among both aromatase inhibitor--and tamoxifen-treated patients.

CONCLUSIONS

Tamoxifen and aromatase inhibitor therapy affect VEGF and endostatin levels and likely contribute to the angiogenic balance in breast cancer patients. Aspirin decreased the proangiogenic effects of tamoxifen, suggesting that antiplatelet and/or antiangiogenic therapy might improve the effectiveness of tamoxifen in women with breast cancer.

Clinical significance of tissue levels of matrix metalloproteinases and tissue inhibitors of metalloproteinases in gastric cancer

BACKGROUND

Matrix metalloproteinases (MMPs) are one of the major classes of proteolytic enzymes involved in tumor invasion and metastasis, being inhibited by naturally occurring tissue inhibitors of metalloproteinases (TIMPs). In this study, we examined the expression of MMP-2, MMP-9, membrane-type 1 (MT1)-MMP, TIMP-1, and TIMP-2 in biopsy tissues of gastric cancer, and the correlation between their expression and clinicopathological parameters.

METHODS

Biopsy specimens from 66 patients with gastric carcinoma were available for this study. To determine the expression of MMP-2, MMP-9, MT1-MMP, TIMP-1, and TIMP-2, semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) was carried out on tumor and normal tissues, respectively, sampled during diagnostic gastroscopic examination. Immunohistochemical staining of representative samples using monoclonal antibody directed against MT1-MMP was done, and the clinicopathological variables were reviewed retrospectively.

RESULTS

The expression level of MMPs and TIMPs was evaluated using the tumor : normal (T/N) ratios of MMPs and TIMPs. The T/N ratio of MT1-MMP mRNA showed a significant correlation with lymph node metastasis and tumor stage (P < 0.05). The other RT-PCR data of MMP-2, MMP-9, TIMP-1, and TIMP-2 did not show any significant correlation with clinicopathological parameters. Immunohistochemistry for MT1-MMP showed a positive immunoreaction in gastric adenocarcinoma and negative staining in normal mucosa.

CONCLUSIONS

The correlation between the increased expression of MT1-MMP and clinicopathological variables reflects a role in predicting the aggressive behavior of gastric cancer. Because an RT-PCR assay can be performed on biopsy specimens obtained before surgery, an evaluation of MT1-MMP expression in biopsy specimens by RT-PCR may provide useful preoperative information on tumor aggressiveness.

Protein kinase C delta mediates platelet-induced breast cancer cell invasion

Platelets play an important role in carcinogenesis, but the underlying molecular mechanisms remain poorly understood. To investigate the effects of platelets on in vitro invasion of MCF7 human breast cancer cells, human MCF7 cells were used to study their interactions with platelets using aggregometry and cell invasion chambers. Zymography and quantitative polymerase chain reaction (PCR) were used to study matrix metalloproteinases (MMPs), whereas Western blot was used to study protein kinase C (PKC) delta in MCF7 cells. We observed that platelets promoted invasion of MCF7 cells (3-fold increase, p<0.05, n=3) and that this process correlated with a dramatic increase in MMP-9 (8 fold-increase, p<0.001, n=3), which is known to facilitate cancer cell invasion. Because both platelets and MCF7 cells have been shown to release MMP-9, we investigated the cellular source that accounted for this increase. The time course and the use of specific protein synthesis inhibitors demonstrated that most of the increase in MMP-9 levels derived from de novo synthesis of this protease by cancer cells. Furthermore, platelets activated PKCdelta in MCF7 cells after 1 h of incubation (18.45+/-4.75% increase, p<0.05, n=4-7), which, in turn, led to an up-regulation of MMP-9 mRNA (from 60+/-20 to 1040+/-100 pg, p<0.001, n=3) and protein levels (18-fold increase, p<0.001, n=3), with the subsequent cell invasion-promoting effects. PKCdelta plays a crucial role in transducing the invasion-promoting effects of platelets in breast cancer cells, and the specific inhibition of PKCdelta may be a strategy to decrease platelet-mediated cancer cell invasion.

Obese state leads to elevated levels of TGF-β and COX isoforms in platelets of Zucker rats

Platelets are rich sources of growth factors and enzymes that are implicated in a number of diseases including obesity, atherosclerosis, heart disease, syndrome X, liver and kidney diseases and certain types of cancers. In this research we investigated, if platelets in Zucker obese rats differ from their lean counterparts with respect to the levels of TGF-beta and COX isoforms, implicated in the pathogenesis of chronic diseases. In addition, we investigated if energy intake of the animals affects the platelet physiology. Platelets were isolated from obese and lean rats bearing preneoplastic lesions in their colon. Prior to platelet isolation these rats were fed either ad libitum (Ob or Ln) or energy restricted (Ob-ER or Ln-ER) diets for 8 weeks (n = 8/group). The levels of TGF-beta1/-beta2 and COX-1/-2 proteins in platelets were analyzed by Western blot. The platelets of the Ob rats had significantly higher levels of TGF-beta1, COX-1/-2 (p < 0.001) than did the platelets of the Ln rats and were not affected by moderate energy restriction. There were no significant differences in the protein expression of platelet TGF-beta2 among any of the groups. These results demonstrate that cytokines and candidates playing a role in the pathogenesis of chronic diseases, such as TGF-beta1 and COX-1/-2, are over-expressed in platelets of Zucker obese rats by comparison to their lean counterparts. These findings also demonstrate that the genotype of the animals exerts a significant effect on the biochemical composition of the platelets and could contribute to the pathogenesis of colon cancer and other metabolic abnormalities associated with obesity.

Platelet-derived lysophosphatidic acid supports the progression of osteolytic bone metastases in breast cancer

The role of lysophosphatidic acid (LPA) in cancer is poorly understood. Here we provide evidence for a role of LPA in the progression of breast cancer bone metastases. LPA receptors LPA(1), LPA(2), and LPA(3) were expressed in human primary breast tumors and a series of human breast cancer cell lines. The inducible overexpression of LPA(1) in MDA-BO2 breast cancer cells specifically sensitized these cells to the mitogenic action of LPA in vitro. In vivo, LPA(1) overexpression in MDA-BO2 cells enhanced the growth of subcutaneous tumor xenografts and promoted bone metastasis formation in mice by increasing both skeletal tumor growth and bone destruction. This suggested that endogenous LPA was produced in the tumor microenvironment. However, MDA-BO2 cells or transfectants did not produce LPA. Instead, they induced the release of LPA from activated platelets which, in turn, promoted tumor cell proliferation and the LPA(1)-dependent secretion of IL-6 and IL-8, 2 potent bone resorption stimulators. Moreover, platelet-derived LPA deprivation in mice, achieved by treatment with the platelet antagonist Integrilin, inhibited the progression of bone metastases caused by parental and LPA(1)-overexpressing MDA-BO2 cells and reduced the progression of osteolytic lesions in mice bearing CHO-beta3wt ovarian cancer cells. Overall, our data suggest that, at the bone metastatic site, tumor cells stimulate the production of LPA from activated platelets, which enhances both tumor growth and cytokine-mediated bone destruction.

Prognostic Significance of Stromelysin-3 and Tissue Inhibitor of Matrix Metalloproteinase-2 in Esophageal Cancer

OBJECTIVE

Stromelysins (matrix metalloproteinases: MMP-10 or ST-2 and MMP-11 or ST-3) and tissue inhibitors of matrix metalloproteinases (TIMP-1 and 2) have been shown to be associated with human tumor progression, invasion and metastasis. The aim of the present study was to determine the prognostic significance of these proteins in esophageal squamous cell carcinoma (ESCC).

METHODS

Immunohistochemical analysis was carried out in 65 surgically resected ESCCs and 49 distant histologically normal esophageal tissues and 16 cases of dysplasias. Statistical analyses were performed to determine the associations between the protein expression and clinicopathological parameters and survival of esophageal cancer patients.

RESULTS

Expression of ST-2, ST-3, TIMP-1 and TIMP-2 was observed in 43/65 (66%), 51/65 (78%), 43/65 (66%) and 47/65 (72%) ESCC cases, respectively. Univariate analysis showed that TIMP-2 expression was associated with tumor site (OR = 2.63, p = 0.017). TIMP-1+/TIMP-2+ phenotype was inversely correlated with nodal invasiveness of the tumor (OR = 0.4, p = 0.04). Interestingly, p53 expression was associated with increased levels of ST-3 (OR = 0.11, p = 0.02) and TIMP-1 (OR = 3.2, p = 0.007) suggesting possible involvement of p53 in the regulation of these proteins. An increased expression of ST-2, ST-3, TIMP-1 and TIMP-2 was observed in 11/16 (69%), 7/17 (44%), 11/16 (69%) and 8/16 (50%) dysplasias also suggesting that these alterations are early events in esophageal tumorigenesis. All the ESCC patients were followed up postesophagectomy for a maximum period of 59 months (mean disease-free survival = 12 months). Kaplan-Meier survival analysis showed that patients with ST-3-positive and TIMP-2-negative carcinoma had a significantly shorter disease-free survival (median disease-free survival time of 4 months) as compared to patients in the other groups (median disease-free survival time of 20 months; p = 0.0016). To our knowledge this is the first report showing that ST-3+/TIMP-2- phenotype remained of significant predictive value for disease-free survival (p = 0.0007) in multivariate analysis including a conventional clinicopathological factor, tumor stage (p = 0.051).

CONCLUSION

Our results suggest that ST-3+/TIMP-2- phenotype is an adverse prognosticator in esophageal cancer patients.

Gene expression of angiogenic factors correlates with metastatic potential of prostate cancer cells

We hypothesize that expression of proangiogenic genes correlates with the metastatic potential of prostate cancer cells. LNCaP, DU-145, and PC-3 are prostate cancer cell lines with low, moderate, and high metastatic potential, respectively, as we demonstrated by their capacity to invade an extracellular matrix, an established tumor invasion assay. The constitutive gene expression of the proangiogenic factors, vascular endothelial growth factor, intercellular adhesion molecule-1, interleukin-8, and transforming growth factor-beta2, was significantly greater in the more metastatic DU-145 and PC-3 cells as compared with LNCaP cells. Matrix metalloproteinase (MMP)-9 is thought to contribute to the invasive phenotype of tumor cells. PC-3 cells showed increased expression of MMP-9 and membrane type 4-MMP as compared with LNCaP and DU-145. Tissue inhibitors of metalloproteinase 1 and 4 gene expression were elevated in DU-145 and PC-3 cells, but paradoxically, LNCaP cells had undetectable levels of these genes. We transfected and overexpressed MMP-9 in poorly metastatic LNCaP cells and measured their invasive activity. Transient expression of human MMP-9 in LNCaP cells produced a 3-5-fold increase in MMP-9 activity with a comparable increase in invasiveness. Antisense ablation of the expression of MMP-9 in DU-145 and PC-3 cells produced concomitant inhibition of the gene expression of the proangiogenic factors, vascular endothelial growth factor, and intercellular adhesion molecule-1 (ICAM-1). Treatment of DU-145 and PC-3 cells with a selective chemical inhibitor of MMP-9 proteinase activity also inhibited their invasive activity. These results support our hypothesis that metastatic potential of prostate cancer cells correlates with expression of proangiogenic factors.

The influence of platelets on the promotion of invasion by tumor cells and inhibition by antiplatelet agents

OBJECTIVE

Using a chemoinvasion assay, we show that platelets promote invasiveness of 5 pancreatic adenocarcinoma cell lines.

METHODS

Gelatin zymography and Western blot analysis were performed to detect metalloproteinase-9 (MMP-9) secreted from tumor cells in the presence or absence of platelets. The effects of antiplatelet agents on the invasiveness of tumor cells and the secretion level of MMP-9 were evaluated.

RESULTS

The number of traversed tumor cells significantly increased when incubated with platelets compared without platelets in all cell lines. The MMP-9 band was detected in all tumor cell lines, and the intensity was obviously greater in conditions of incubation with platelets than without. In the experiment of antiplatelet agents effects, it was confirmed that invasiveness of tumor cells significantly decreased following incubation with cilostazol depending on the concentration in spite of the presence of platelets. The level of MMP-9 also significantly decreased in the ELISA analysis.

CONCLUSIONS

These data mean platelets activate invasiveness of tumor cells because of enhanced MMP-9 secretion. Furthermore, anti-platelet drugs may inhibit invasiveness of tumor cells due to decreased MMP-9 secretion, and this inhibition may lead to the suppression of tumor cell invasion. We propose that antiplatelet agents are applicable in clinical treatment to inhibit metastasis of malignant tumor cells.

Apigenin acts on the tumor cell invasion process and regulates protease production

Apigenin is a widely distributed plant flavonoid and was proposed as an antitumor agent. In this study, we investigated the apigenin effects on the protease-mediated invasiveness in an estrogen-insensitive breast tumor cell line MDA-MB231. The results show that apigenin at 22.8-45.5 microM (2.5-10 micrograms/ml) strongly inhibited, in a dose-dependent manner, tumor cell invasion through Matrigel, cell migration, and cell proliferation. We show that apigenin treatment from 22.8 microM (2.5 micrograms/ml) led to a partial decrease in urokinase-plasminogen activator expression and to a total inhibition of phorbol 12-myristate 13-acetate-induced matrix metalloproteinase-9 secretion. We also demonstrate in the apigenin-treated cells a defective adhesion to Matrigel and a G2-M cell cycle arrest. Taken together, our results demonstrate that apigenin is a pleiotropic effector affecting protease-dependent invasiveness and associated processes and proliferation of tumor cells.

Differential modulation of transforming growth factor-betas and cyclooxygenases in the platelet lysates of male F344 rats by dietary lipids and piroxicam

Platelets are implicated in the pathogenesis of various chronic diseases including cancer. The main objective of the present study was to determine if dietary fish oil and piroxicam, known modulators of colon tumorigenesis, effect transforming growth factor (TGF)-betas and cyclooxygenase (COX) isozymes in the platelets of colon tumor-bearing male F344 rats. TGF-betas and COXs are important in the development of chronic illnesses including colon cancer. Animals harboring preneoplastic colonic lesions were randomly allocated to a low fat diet (5% by weight--low corn oil, LFC) and three high fat diets (23% by weight--high corn oil, HFC; high corn oil containing 150-ppm piroxicam, HFC+P; and high fish oil, HFF) for 16 weeks. TGF-beta1, TGF-beta2, COX-1 and COX-2 protein levels were assessed in the platelets by Western blot analysis. Active TGF-beta1 (12.5 kDa) level was significantly lower in the platelets of the HFC+P group (p < 0.001), whereas precursor TGF-beta1 (39 kDa) level was significantly lower in the platelets of the HFF group (p < 0.001). The anti-rabbit TGF-beta2 polyclonal antibody did not detect the 13-kDa active TGF-beta2 protein in the platelets. However a 29-kDa protein, potentially a precursor of TGF-beta2, was detected in the platelets of all the groups and was significantly lower in the HFC+P and HFF groups than in LFC and HFC (p < 0.001). COX-1 level was significantly lower in the HFF group than the other three groups (p < 0.001). COX-2 protein was detected in the platelets of all diet groups. Piroxicam in the presence of high corn oil (HFC+P) significantly lowered the level of COX-2 (p < 0.001), without having any effect on COX-1 level. These findings conclusively show that LFC and HFC differ from HFF and HFC+P, and piroxicam differs from fish oil, in regulating the levels of TGF-betas and COX in the platelets. This supports the conjecture that the levels of bioactive constituents of the platelets are profoundly modulated by dietary lipids, which in turn could influence the pathogenesis of chronic illnesses.