GITR ligand provided by thrombopoietic cells inhibits NK cell antitumor activity

Inhibition of NK Reactivity Against Solid Tumors by Platelet-Derived RANKL

NK cells play an important role in tumor immunosurveillance. Their reactivity is governed by various activating and inhibitory surface receptors, which include several members of the TNF/TNF receptor family. For more than 50 years, it has been recognized that tumor immunosurveillance and in particular NK cell antitumor reactivity is largely influenced by platelets, but the underlying mechanisms remain to be fully elucidated. Here we report that upon activation, which reportedly occurs following interaction with cancer cells, platelets upregulate the TNF family member RANKL. Comparative analysis of the expression of RANK among different NK cell subsets and RANKL on platelets in cancer patients and healthy volunteers revealed a distinct malignant phenotype, and platelet-derived RANKL was found to inhibit the activity of normal NK cells against cancer cells. Notably, NK cell antitumor reactivity could be partially restored by application of denosumab, a RANKL-neutralizing antibody approved for treatment of benign and malignant osteolysis. Together, our data not only unravel a novel mechanism of tumor immune evasion mediated by platelets, but they also provide a functional explanation for the clinical observation that denosumab, beyond protecting from bone loss, may prolong disease-free survival in patients with solid tumors.

NK Cell-Based Immunotherapy in Cancer Metastasis

Metastasis represents the leading cause of cancer-related death mainly owing to the limited efficacy of current anticancer therapies on advanced malignancies. Although immunotherapy is rendering promising results in the treatment of cancer, many adverse events and factors hampering therapeutic efficacy, especially in solid tumors and metastases, still need to be solved. Moreover, immunotherapeutic strategies have mainly focused on modulating the activity of T cells, while Natural Killer (NK) cells have only recently been taken into consideration. NK cells represent an attractive target for cancer immunotherapy owing to their innate capacity to eliminate malignant tumors in a non-Major Histocompatibility Complex (MHC) and non-tumor antigen-restricted manner. In this review, we analyze the mechanisms and efficacy of NK cells in the control of metastasis and we detail the immunosubversive strategies developed by metastatic cells to evade NK cell-mediated immunosurveillance. We also share current and cutting-edge clinical approaches aimed at unleashing the full anti-metastatic potential of NK cells, including the adoptive transfer of NK cells, boosting of NK cell activity, redirecting NK cell activity against metastatic cells and the release of evasion mechanisms dampening NK cell immunosurveillance.

Anti-platelet treatments in cancer: Basic and clinical research

Over the past few decades the central role that platelets play in cancer development and progression, and especially in metastasis, has been elucidated. The molecular mechanisms responsible for initiating and mediating tumor cell-induced platelet aggregation and secretion have been largely unravelled. Considerable mechanistic insight into how platelets contribute to tumor angiogenesis, immunoevasion and cancer cell invasion have been clarified and, consequently, platelets have been identified as potential new drug targets for cancer therapy. This article gives an overview of the platelet-targeted pharmacologic approaches that have been attempted in the prevention of cancer development, progression and metastasis, including the application of antiplatelet drugs currently used for cardiovascular disease and of new and novel strategies.

Role of platelets and platelet receptors in cancer metastasis

The interaction of tumor cells with platelets is a prerequisite for successful hematogenous metastatic dissemination. Upon tumor cell arrival in the blood, tumor cells immediately activate platelets to form a permissive microenvironment. Platelets protect tumor cells from shear forces and assault of NK cells, recruit myeloid cells by secretion of chemokines, and mediate an arrest of the tumor cell platelet embolus at the vascular wall. Subsequently, platelet-derived growth factors confer a mesenchymal-like phenotype to tumor cells and open the capillary endothelium to expedite extravasation in distant organs. Finally, platelet-secreted growth factors stimulate tumor cell proliferation to micrometastatic foci. This review provides a synopsis on the current literature on platelet-mediated effects in cancer metastasis and particularly focuses on platelet adhesion receptors and their role in metastasis. Immunoreceptor tyrosine-based activation motif (ITAM) and hemi ITAM (hemITAM) comprising receptors, especially, glycoprotein VI (GPVI), FcγRIIa, and C-type lectin-like-2 receptor (CLEC-2) are turned in the spotlight since several new mechanisms and contributions to metastasis have been attributed to this family of platelet receptors in the last years.

Cancer and platelet crosstalk: opportunities and challenges for aspirin and other antiplatelet agents

Platelets have long been recognized as key players in hemostasis and thrombosis; however, growing evidence suggests that they are also significantly involved in cancer, the second leading cause of mortality worldwide. Preclinical and clinical studies showed that tumorigenesis and metastasis can be promoted by platelets through a wide variety of crosstalk between platelets and cancer cells. For example, cancer changes platelet behavior by directly inducing tumor-platelet aggregates, triggering platelet granule and extracellular vesicle release, altering platelet phenotype and platelet RNA profiles, and enhancing thrombopoiesis. Reciprocally, platelets reinforce tumor growth with proliferation signals, antiapoptotic effect, and angiogenic factors. Platelets also activate tumor invasion and sustain metastasis via inducing an invasive epithelial-mesenchymal transition phenotype of tumor cells, promoting tumor survival in circulation, tumor arrest at the endothelium, and extravasation. Furthermore, platelets assist tumors in evading immune destruction. Hence, cancer cells and platelets maintain a complex, bidirectional communication. Recently, aspirin (acetylsalicylic acid) has been recognized as a promising cancer-preventive agent. It is recommended at daily low dose by the US Preventive Services Task Force for primary prevention of colorectal cancer. The exact mechanisms of action of aspirin in chemoprevention are not very clear, but evidence has emerged that suggests a platelet-mediated effect. In this article, we will introduce how cancer changes platelets to be more cancer-friendly and highlight advances in the modes of action for aspirin in cancer prevention. We also discuss the opportunities, challenges, and opposing viewpoints on applying aspirin and other antiplatelet agents for cancer prevention and treatment.

Platelet-activating factor podoplanin: from discovery to drug development

Tumor cell-induced platelet aggregation facilitates hematogenous metastasis by promoting tumor embolization, preventing immunological assaults and shear stress, and the platelet-releasing growth factors support tumor growth and invasion. Podoplanin, also known as Aggrus, is a type I transmembrane mucin-like glycoprotein and is expressed on wide range of tumor cells. Podoplanin has a role in platelet aggregation and metastasis formation through the binding to its platelet receptor, C-type lectin-like receptor 2 (CLEC-2). The podoplanin research was originally started from the cloning of highly metastatic NL-17 subclone from mouse colon 26 cancer cell line and from the establishment of 8F11 monoclonal antibody (mAb) that could neutralize NL-17-induced platelet aggregation and hematogenous metastasis. Later on, podoplanin was identified as the antigen of 8F11 mAb, and its ectopic expression brought to cells the platelet-aggregating abilities and hematogenous metastasis phenotypes. From the 8F11 mAb recognition epitopes, podoplanin is found to contain tandemly repeated, highly conserved motifs, designated platelet aggregation-stimulating (PLAG) domains. Series of analyses using the cells expressing the mutants and the established neutralizing anti-podoplanin mAbs uncovered that both PLAG3 and PLAG4 domains are associated with the CLEC-2 binding. The neutralizing mAbs targeting PLAG3 or PLAG4 could suppress podoplanin-induced platelet aggregation and hematogenous metastasis through inhibiting the podoplanin–CLEC-2 binding. Therefore, these domains are certainly functional in podoplanin-mediated metastasis through its platelet-aggregating activity. This review summarizes the platelet functions in metastasis formation, the role of platelet aggregation-inducing factor podoplanin in pathological and physiological situations, and the possibility to develop podoplanin-targeting drugs in the future.

Hypoxia, cytokines and stromal recruitment: parallels between pathophysiology of encapsulating peritoneal sclerosis, endometriosis and peritoneal metastasis

Peritoneal response to various kinds of injury involves loss of peritoneal mesothelial cells (PMC), danger signalling, epithelial-mesenchymal transition and mesothelial-mesenchymal transition (MMT). Encapsulating peritoneal sclerosis (EPS), endometriosis (EM) and peritoneal metastasis (PM) are all characterized by hypoxia and formation of a vascularized connective tissue stroma mediated by vascular endothelial growth factor (VEGF). Transforming growth factor-β1 (TGF-β1) is constitutively expressed by the PMC and plays a major role in the maintenance of a transformed, inflammatory micro-environment in PM, but also in EPS and EM. Persistently high levels of TGF-β1 or stimulation by inflammatory cytokines (interleukin-6 (IL-6)) induce peritoneal MMT, adhesion formation and fibrosis. TGF-β1 enhances hypoxia inducible factor-1α expression, which drives cell growth, extracellular matrix production and cell migration. Disruption of the peritoneal glycocalyx and exposure of the basement membrane release low molecular weight hyaluronan, which initiates a cascade of pro-inflammatory mediators, including peritoneal cytokines (TNF-α, IL-1, IL-6, prostaglandins), growth factors (TGF-α, TGF-β, platelet-derived growth factor, VEGF, epidermal growth factor) and the fibrin/coagulation cascade (thrombin, Tissue factor, plasminogen activator inhibitor [PAI]-1/2). Chronic inflammation and cellular transformation are mediated by damage-associated molecular patterns, pattern recognition receptors, AGE-RAGE, extracellular lactate, pro-inflammatory cytokines, reactive oxygen species, increased glycolysis, metabolomic reprogramming and cancer-associated fibroblasts. The pathogenesis of EPS, EM and PM shows similarities to the cellular transformation and stromal recruitment of wound healing.

Systemic immune-inflammation index in germ-cell tumours

Background:

We evaluated systemic immune-inflammation index (SII) and its association with patient outcome in germ-cell tumours (GCTs).

Methods:

Two independent cohorts of patients were analysed; the discovery set (n=171) from a single institution and the validation set (n=181) previously included in a study evaluating PD-L1 in GCTs. The SII was calculated using platelet (P), neutrophil (N) and lymphocyte (L) counts before chemotherapy and correlated with survival using regression analyses and Kaplan–Meier method.

Results:

In the discovery cohort, the SII was associated with poor risk clinical features. Patients with low SII had significantly longer progression-free survival (HR=0.22, 95% CI 0.12–0.41, P<0.001) and overall survival (OS) (HR=0.16, 95% CI 0.08–0.32, P<0.001) compared to high SII. This index was independent of International Germ Cell Cancer Collaborative Group criteria in multivariable Cox regression analysis for OS and was validated in an independent cohort. When combining PD-L1 expression on tumour infiltrating lymphocytes (TILs) and SII, we identified three distinctive prognostic groups.

Conclusions:

High SII was associated with poor outcome in GCTs. Combination of PD-L1 positive TILs and SII could further refine prognosis in GCTs.

Platelet-mediated shedding of NKG2D ligands impairs NK cell immune-surveillance of tumor cells

Platelets promote metastasis, among others by coating cancer cells traveling through the blood, which results in protection from NK cell immune-surveillance. The underlying mechanisms, however, remain to be fully elucidated. Here we report that platelet-coating reduces surface expression of NKG2D ligands, in particular MICA and MICB, on tumor cells, which was mirrored by enhanced release of their soluble ectodomains. Similar results were obtained upon exposure of tumor cells to platelet-releasate and can be attributed to the sheddases ADAM10 and ADAM17 that are detectable on the platelet surface and in releasate following activation and at higher levels on platelets of patients with metastasized lung cancer compared with healthy controls. Platelet-mediated NKG2DL-shedding in turn resulted in impaired "induced self" recognition by NK cells as revealed by diminished NKG2D-dependent lysis of tumor cells. Our results indicate that platelet-mediated NKG2DL-shedding may be involved in immune-evasion of (metastasizing) tumor cells from NK cell reactivity.

Platelets impair natural killer cell reactivity and function in endometriosis through multiple mechanisms

Study question

Do platelets have any role in the reduced cytotoxicity of natural killer (NK) cells in endometriosis?

Summary answer

Platelets impair NK cell reactivity and function in endometriosis through multiple mechanisms.

What is known already

Platelets play an important role in the development of endometriosis, and platelet-derived transforming growth factor-β1 (TGF-β1) suppresses the expression of NK Group 2, Member D (NKG2D) on NK cells, resulting in reduced cytotoxicity in women with endometriosis.

Study design size, duration

Experiments on mice with induced endometriosis in which either platelets, NK cells or both were depleted and controls (none depleted). In vitro experiments with NK cells, platelets and, as target cells, endometriotic epithelial cell and endometrial stromal cell lines.

Participants/materials setting methods

Immunohistochemistry analysis of ectopic endometrial tissues from mice with induced endometriosis receiving either platelet depletion (PD), NK cell depletion, or both or none. Immunofluorescence, flow cytometry and gene expression analysis for major histocompatibility complex class I (MHC-I) expression in target cells. Cytotoxicity and degranulation assays and the measurement of interferon (IFN)-γ secretion for the evaluation of NK cytotoxicity. Flow cytometry and gene expression for the expression of NK cell receptors.

Main results and the role of chance

PD resulted in significantly reduced lesion weight in mice with induced endometriosis, but NK cell depletion as well as concomitant platelet and NK cell depletion increased the weight, suggesting that the anti-endometriosis effect of PD is mediated, at least in part, by increased NK cell cytotoxicity against endometriotic cells. Co-incubation of target cells with platelets resulted in rapid platelet coating as well as increased MHC-I expression in these cells, effectively providing a cloak of 'pseudo-self' to these cells to shield against NK cell lysis. It also reduced the expression of NKG2D ligands MICA and MICB and reduced the NK cell cytotoxicity. In addition, co-incubation of NK cells with platelets impaired the NK cell cytotoxicity as well. This impaired NK cell cytotoxicity was not due to the increased NK cell apoptosis, but, rather, through reduced NK cell degranulation and IFN-γ production, and reduced expression of activating receptors NKG2D and NKp46 and increased expression of inhibitory receptor KIR2DL1 in NK cells. Inhibition of TGF-β1 signaling partially restored the aberrant expression of NKG2D, NKp46 and KIR2DL1, and partially restored the impaired NK cell cytotoxicity induced by activated platelets and their releasate.

Large scale data

Not applicable.

Limitations reasons for caution

This study is confined by the limitation of animal and in vitro experimentation and the lack of direct human data.

Wider implications of the findings

Anti-platelet treatment holds promise in treating endometriosis.

Study funding/competing interests

The National Natural Science Foundation of China (81471434 to S.W.G., 81270676 to S.W.G., 81370695 to X.S.L. and 81671436 to X.S.L). None of the authors has anything to disclose.

Tailoring Natural Killer cell immunotherapy to the tumour microenvironment

Natural killer (NK) cells are cytotoxic and cytokine-secreting cells that can mediate potent anti-tumour activity. Accumulating evidence indicates that NK cell functions are severely compromised within the confines of the tumour microenvironment thus impairing the efficacy and development of NK cell-based therapies. Here we review the various cellular and molecular pathways that tumours have supplanted to evade NK cell surveillance. We highlight novel strategies designed to alleviate or circumvent the immunosuppressive conditions of the tumour microenvironment in order to emancipate NK cell function and stifle the inexorable growth and metastasis of malignant cells.

Intravascular Survival and Extravasation of Tumor Cells

Most metastasizing tumor cells reach distant sites by entering the circulatory system. Within the bloodstream, they are exposed to severe stress due to loss of adhesion to extracellular matrix, hemodynamic shear forces, and attacks of the immune system, and only a few cells manage to extravasate and to form metastases. We review the current understanding of the cellular and molecular mechanisms that allow tumor cells to survive in the intravascular environment and that mediate and promote tumor cell extravasation. As these processes are critical for the metastatic spread of tumor cells, we discuss implications for potential therapeutic approaches and future research.

Recombinant Antibodies to Arm Cytotoxic Lymphocytes in Cancer Immunotherapy

Immunotherapy has the potential to support and expand the body's own armamentarium of immune effector functions, which have been circumvented during malignant transformation and establishment of cancer and is presently considered to be the most promising treatment option for cancer patients. Recombinant antibody technologies have led to a multitude of novel antibody formats, which are in clinical development and hold great promise for future therapies. Among these formats, bispecific antibodies are extremely versatile due to their high efficacy to recruit and activate anti-tumoral immune effector cells, their excellent safety profile, and the opportunity for use in combination with cellular therapies. This review article summarizes the latest developments in cancer immunotherapy using immuno-engagers for recruiting T cells and NK cells to the tumor site. In addition to antibody formats, malignant cell targets, and immune cell targets, opportunities for combination therapies, including check point inhibitors, cytokines and adoptive transfer of immune cells, will be summarized and discussed.

Platelet-derived TGF-β1 mediates the down-modulation of NKG2D expression and may be responsible for impaired natural killer (NK) cytotoxicity in women with endometriosis

STUDY QUESTION

Does platelet-derived transforming growth factor-β1 (TGF-β1) have any role in the reduced cytotoxicity of natural killer (NK) cells in women with endometriosis?

SUMMARY ANSWER

Platelet-derived TGF-β1 suppresses the expression of NK Group 2, Member D (NKG2D) on NK cells, resulting in reduced cytotoxicity in women with endometriosis, but neutralization of TGF-β1 reverses the reduction.

WHAT IS KNOWN ALREADY

NK cells are cytotoxic lymphocytes that play an important role in peritoneal immune surveillance, and their function is known to be impaired in women with endometriosis. There is increased platelet aggregation in endometriotic lesions and increased platelet activation rate in the peripheral blood in women with endometriosis, yet activated platelets release copiousTGF-β1, which is known to be a potent immunosuppressive molecule that suppresses NK cell function and NKG2D expression.

STUDY DESIGN, SIZE, DURATION

Cross-sectional clinical studies of 30 women with endometriosis and 33 women without endometriosis and in vitro experimentation with and without TGF-β1 blockade.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Peritoneal fluid (PF) samples from premenopausal women with endometriosis and age- and menstrual phase-matched controls were collected. Platelet count, white blood cell (WBC) count, mean platelet volume (MPV), platelet activation rate, TGF-β1 concentration, expression levels of NKG2D on NK cells in the PF were evaluated. The apoptosis of freshly isolated NK cells treated with PF from women with endometriosis, the NK cytotoxicity and NKG2D expression treated with PF in the presence or absence of an anti-TGF-β1 antibody were also determined.

MAIN RESULTS AND THE ROLE OF CHANCE

The platelet count, WBC count, MPV, platelet activation rate and the TGF-β1 concentration in the PF from women with endometriosis were significantly elevated when compared with those of women without endometriosis. The TGF-β1 concentration correlated positively with the platelet activation rate (r = 0.59, P < 0.01), suggesting that activated platelets are responsible, at least in part, for the increased TGF-β1 concentration. The cytotoxicity of freshly isolated NK cells treated with PF of women with endometriosis is significantly reduced when compared with that of women without endometriosis. Both the platelet activation rate and the TGF-β1 concentration in the PF correlated negatively with the NKG2D expression in NK cells isolated from the PF (r = -0.36, P < 0.01, and r = -0.45, P < 0.01, respectively). In addition, the NKG2D expression level and the cytotoxicity in freshly isolated NK cells were found to be significantly reduced if co-cultured with PF from women with endometriosis, but the TGF-β1 blockade effectively reverses the reduction.

LIMITATIONS, REASONS FOR CAUTION

This study is limited by the cross-sectional nature of the study.

WIDER IMPLICATIONS OF THE FINDINGS

NKG2D is known to potently activate NK cells, so potent that it even overrides inhibitory signals transduced by other inhibitory receptors. This is the first time we demonstrate that platelet-derived TGF-β1 may be responsible for reduced NKG2D expression as well as reduced cytotoxicity of NK cells in women with endometriosis. This study provides yet another piece of evidence that platelets play critical roles in the development of endometriosis, and anti-platelet treatment should improve NK cell functionality in treating endometriosis. Equally important, this study highlights the critical role of the lesion microenvironment in shaping NK cell-mediated anti-endometriotic immunity.

STUDY FUNDING/COMPETING INTERESTS

This research was supported in part by grants 81270676 (S.-W.G.), 81471434 (S.-W.G.), 81530040 (S.-W.G.), and 81370695 (X.L.) from the National Natural Science Foundation of China, and grant 2013ZYJB0019 (X.L.) from Shanghai Municipal Commission of Health and Family Planning. None of the authors has anything to disclose.

GITRL is associated with increased autoantibody production in patients with rheumatoid arthritis

The study aimed to determine the serum level of glucocorticoid-induced tumor necrosis factor receptor family-related protein ligand (GITRL) in patients with rheumatoid arthritis (RA) and investigate its clinical significance. GITRL levels were measured by enzyme-linked immunosorbent assay (ELISA) in 88 RA patients, 20 osteoarthritis (OA) patients, and 20 healthy controls (HCs). Anti-cyclic citrullinated peptide (anti-CCP) antibodies and rheumatoid factor immunoglobulin G (RF-IgG) were also tested by ELISA. RF-IgM, anti-keratin antibody (AKA), and anti-perinuclear factor (APF) antibodies and the erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and immunoglobulins were measured by standard laboratory techniques. The disease activity was evaluated by the 28-joint count Disease Activity Score (DAS28). GITRL concentrations were significantly elevated in both serum and synovial fluid (SF) of RA patients. GITRL levels in RA sera were significantly higher than those in matched SFs. Positive correlations were found between serum GITRL levels and inflammation parameters or autoantibody production. GITRL levels are significantly elevated in RA serum and SF and are positively correlated with autoantibody production in RA, suggesting a role of GITRL in the development of RA.

Platelet CD40 Exacerbates Atherosclerosis by Transcellular Activation of Endothelial Cells and Leukocytes

OBJECTIVE

Beyond their eminent role in hemostasis and thrombosis, platelets are recognized as mediators of inflammation. Platelet cluster of differentiation 40 (CD40) ligand (CD40L and CD154) plays a key role in mediating platelet-induced inflammation in atherosclerosis. CD40, the receptor for CD40L, is present on platelets; however, the role of CD40 on this cell type is until now undefined.

APPROACH AND RESULTS

We found that in both mice and humans, platelet CD40 mediates the formation of platelet-leukocyte aggregates and the release of chemokine (C-X-C motif) ligand 4. Leukocytes were also less prone to adhere to CD40-deficient thrombi. However, platelet CD40 was not involved in platelet aggregation. Activated platelets isolated from Cd40(-/-)Apoe(-/-) mice adhered less to the endothelium upon injection into Apoe(-/-) mice when compared with CD40-sufficient platelets. Furthermore, lack of CD40 on injected platelets led to reduced leukocyte recruitment to the carotid artery as assayed by intravital microscopy. This was accompanied by a decrease in endothelial vascular cell adhesion molecule-1, platelet endothelial cell adhesion molecule, VE-cadherin, and P-selectin expression. To investigate the effect of platelet CD40 in atherosclerosis, Apoe(-/-) mice received thrombin-activated Apoe(-/-) or Cd40(-/-)Apoe(-/-) platelets every 5 days for 12 weeks, starting at the age of 17 weeks, when atherosclerotic plaques had already formed. When compared with mice that received Apoe(-/-) platelets, those receiving Cd40(-/-)Apoe(-/-) platelets exhibited a >2-fold reduction in atherosclerosis. Plaques of mice receiving CD40-deficient platelets were less advanced, contained less macrophages, neutrophils, and collagen, and displayed smaller lipid cores.

CONCLUSIONS

Platelet CD40 plays a crucial role in inflammation by stimulating leukocyte activation and recruitment and activation of endothelial cells, thereby promoting atherosclerosis.

NK cells and cancer: you can teach innate cells new tricks

Natural killer (NK) cells are the prototype innate lymphoid cells endowed with potent cytolytic function that provide host defence against microbial infection and tumours. Here, we review evidence for the role of NK cells in immune surveillance against cancer and highlight new therapeutic approaches for targeting NK cells in the treatment of cancer.

The Tumor-immune Index is Correlated With the Prognosis of Patients After Curative Resection for Nonsmall Cell Lung Cancer

We developed a novel tumor-immune index (TII) based on carcinoembryonic antigen levels, lymphocyte counts, and platelet counts, and explored its prognostic value in nonsmall cell lung cancer (NSCLC).The prognostic value of the TII was evaluated based on a retrospective study of 205 patients with early NSCLC, who underwent resection in the whole year of 2006, and validated in another group of 228 patients enrolled in the next year of 2007. The optimal cut-off point for the TII was 578 × 10(-9), and this value was used to stratify patients with NSCLC into low TII (≤ 578 × 10(-9)) and high TII (>578 × 10(-9)) groups. Univariate and multivariate analyses revealed that high TII was an independent predictor for overall survival and recurrence-free survival in both the training and validation cohorts. The areas under the curve of the TII for survival and recurrence were significantly larger than those for tumor, node, metastasis (TNM) stage and carcinoembryonic antigen. In the subgroup analysis, the TII was also significantly correlated with overall survival (P = 0.001, P = 0.009, and P = 0.007 in the TNM I, II, and IIIa subgroups, respectively) and recurrence-free survival (P < 0.001, P = 0.006, and P = 0.014 in the TNM I, II, and IIIa subgroups, respectively). Similarly, for patients with N2-positive tumors, the overall survival and recurrence-free survival rates for patients in the high TII group were also significantly lower than the respective values for patients in the low TII group (P = 0.026 and P = 0.007, respectively). The TII can be used to distinguish patients with similar pathologies and stages into high and low-risk categories based on the probability of recurrence according to a convenient blood-based test.

The role of platelets in the tumor microenvironment: From solid tumors to leukemia

Platelets are increasingly being recognized for promoting tumor growth and metastasis. Many cells derived from solid tumors have the ability to aggregate platelets, and this ability correlates with their metastatic potential. Over the past half century, our understanding of tumor cell-induced platelet aggregation (TCIPA) has grown beyond the simple concept that tumor cell-containing microthrombi mechanically embolize the microvasculature. Tumor cell-activated platelets secrete a multitude of factors that reciprocally act on tumor cells, as well as other cells within the tumor microenvironment; thus, affecting both parenychma and tumor-associated stroma. In this review, we summarize the current knowledge of tumor cell-platelet interactions and their influence on the tumor microenvironment, including how these interactions impact neoplastic epithelial cells, endothelial cells, pericytes, fibroblasts, immune cells, and early metastatic niches. In addition, we review the current knowledge of platelet-cancer cell interactions within hematological malignancies and speculate on how platelets may influence the leukemic microenvironment. This article is part of a Special Issue entitled: Tumor Microenvironment Regulation of Cancer Cell Survival, Metastasis, Inflammation, and Immune Surveillance edited by Peter Ruvolo and Gregg L. Semenza.

Systemic immune-inflammation index predicts prognosis of patients after curative resection for hepatocellular carcinoma

PURPOSE

We developed a novel systemic immune-inflammation index (SII) based on lymphocyte, neutrophil, and platelet counts and explored its prognostic value in hepatocellular carcinoma (HCC).

EXPERIMENTAL DESIGN

The SII was developed based on a retrospective study of 133 patients with HCC undergoing resection between 2005 and 2006, and validated in a prospective study of 123 patients enrolled from 2010 to 2011. The circulating tumor cell (CTC) level in the validation cohort was measured using the CellSearch system. Prediction accuracy was evaluated with area under the receiver operating characteristic curve (AUC).

RESULTS

An optimal cutoff point for the SII of 330 × 10(9) stratified the patients with HCC into high (≥330) and low SII (<330) groups in the training cohort. Univariate and multivariate analyses revealed the SII was an independent predictor for overall survival and relapse-free survival, and prognostic for patients with negative α-fetoprotein and Barcelona Clinic Liver Cancer stage 0+A. The AUCs of the SII for survival and recurrence were higher than other conventional clinical indices. An SII ≥ 330 was significantly associated with vascular invasion, large tumors, and early recurrence. CTC levels were significantly higher in the SII ≥ 330 group (1.71 ± 0.34 vs. 4.37 ± 1.04, P = 0.029). In patients with detectable CTCs, those with SII ≥ 330 had higher recurrence rates and shorter survival time than patients with SII < 330.

CONCLUSION

The SII was a powerful prognostic indicator of poor outcome in patients with HCC and is a promising tool for HCC treatment strategy decisions. The dismal outcome in patients with high SII scores might be related to higher CTC levels.

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.

Cancer vaccines: harnessing the potential of anti-tumor immunity

Although the presence of cancer suggests failure of the immune system to protect against development of tumors, the possibility that immunity can be redirected and focused to generate an anti-tumor response offers great translational possibility. The key to this is identifying antigens likely to be present in any given tumor and functionally critical to tumor survival and growth. Such tumor-associated antigens (TAAs) are varied and optimally should be absent from normal tissue. Of particular interest are TAAs associated with the tumor stroma, as immunity directed against the stroma may restrict the ability of the tumor to grow and metastasize. Important to directing the immune system toward an effect anti-tumor response is the understanding of how TAAs are processed and how the tumor is able to evade immune elimination. The process of immunoediting happens in response to the selective pressure that the immune system places upon tumor cell populations and allows for emergence of tumor cells capable of escaping immune destruction. Efforts to harness the immune system for clinical application has been aided by vaccines based on purified recombinant protein or nucleic acid TAAs. For example, a vaccine for canine melanoma has been developed and approved based on immunization with DNA components of tyrosinase, a glycoprotein essential to melanin synthesis. The performance of cancer vaccines has been aided in some cases when supplemented with immunostimulatory molecules such as interleukin 2 or a novel extracellular matrix vaccine adjuvant. Vaccines with the broadest menu of antigenic targets may be those most likely to succeed against cancer. For this reason, tissue vaccines produced from harvested tumor material may offer significant benefit. With several cancer vaccines on the veterinary and human markets, efforts to understand basic tumor immunology are soon to yield great dividends.

The TNF receptor-ligands 4-1BB-4-1BBL and GITR-GITRL in NK cell responses

Interactions between several tumor necrosis factor (TNF)-TNF receptor (TNFR) superfamily members that are expressed by T cells and natural killer (NK) cells and various other cell types modulate immune responses. This review summarizes the current understanding of how the TNF ligand-TNFR interactions 4-1BBL with 4-1BB, and GITRL with glucocorticoid-induced TNFR-related (GITR) regulate NK cell mediated antitumor responses and discuss its therapeutic implications.