Monitoring of circulating angiogenic factors in dendritic cell-based cancer immunotherapy

Involvement of Matricellular Proteins in Cellular Senescence: Potential Therapeutic Targets for Age-Related Diseases

Senescence is a physiological and pathological cellular program triggered by various types of cellular stress. Senescent cells exhibit multiple characteristic changes. Among them, the characteristic flattened and enlarged morphology exhibited in senescent cells is observed regardless of the stimuli causing the senescence. Several studies have provided important insights into pro-adhesive properties of cellular senescence, suggesting that cell adhesion to the extracellular matrix (ECM), which is involved in characteristic morphological changes, may play pivotal roles in cellular senescence. Matricellular proteins, a group of structurally unrelated ECM molecules that are secreted into the extracellular environment, have the unique ability to control cell adhesion to the ECM by binding to cell adhesion receptors, including integrins. Recent reports have certified that matricellular proteins are closely involved in cellular senescence. Through this biological function, matricellular proteins are thought to play important roles in the pathogenesis of age-related diseases, including fibrosis, osteoarthritis, intervertebral disc degeneration, atherosclerosis, and cancer. This review outlines recent studies on the role of matricellular proteins in inducing cellular senescence. We highlight the role of integrin-mediated signaling in inducing cellular senescence and provide new therapeutic options for age-related diseases targeting matricellular proteins and integrins.

Human expression patterns: qualitative and quantitative analysis of thrombospondin-1 under physiological and pathological conditions

Thrombospondin-1 (TSP-1), a matricellular protein and one of the first endogenous anti-angiogenic molecules identified, has long been considered a potent modulator of human diseases. While the therapeutic effect of TSP-1 to suppress cancer was investigated in both research and clinical settings, the mechanisms of how TSP-1 is regulated in cancer remain elusive, and the scientific answers to the question of whether TSP-1 expressions can be utilized as diagnostic or prognostic marker for patients with cancer are largely inconsistent. Moreover, TSP-1 plays crucial functions in angiogenesis, inflammation and tissue remodelling, which are essential biological processes in the progression of many cardiovascular diseases, and therefore, its dysregulated expressions in such conditions may have therapeutic significance. Herein, we critically analysed the literature pertaining to TSP-1 expression in circulating blood and pathological tissues in various types of cancer as well as cardiovascular and inflammation-related diseases in humans. We compare the secretion rates of TSP-1 by different cancer and non-cancer cells and discuss the potential connection between the expression changes of TSP-1 and vascular endothelial growth factor (VEGF) observed in patients with cancer. Moreover, the pattern and emerging significance of TSP-1 profiles in cardiovascular disease, such as peripheral arterial disease, diabetes and other related non-cancer disorders, are highlighted. The analysis of published TSP-1 data presented in this review may have implications for the future exploration of novel TSP-1-based treatment strategies for cancer and cardiovascular-related diseases.

Shift in the Balance between Circulating Thrombospondin-1 and Vascular Endothelial Growth Factor in Cancer Patients: Relationship to Platelet α-Granule Content and Primary Activation

Tumoral angiogenesis is regulated by the balance between factors that activate and inhibit angiogenesis. Elevated levels of activators have been associated with a poor prognosis in cancer patients, but little is known about the net balance between circulating activators and inhibitors in these patients. This study was designed to determine whether the balance between circulating concentrations of the angiogenesis inhibitor TSP-1 and the activator VEGF differs from that in healthy persons, and to shed light on the possible role of platelets in this balance. Twenty-five cancer patients and 18 healthy subjects were included. Serum and plasma concentrations of VEGF, TSP-1 and PF4 were measured by ELISA. Our results showed that in healthy subjects the balance between the TSP-1 and VEGF concentrations in serum and in serum minus plasma was twice to three times as high as in cancer patients (p<0.05). The theoretical TSP-1 content per platelet was greater in healthy subjects than in patients (94 vs. 53.6 ng/mL, p<0.05), and platelet activation (determined indirectly as the plasma concentration of PF4) was greater in cancer patients (129 vs. 48 IU/mL, p<0.01). Platelet activation correlated significantly with serum concentration of TSP-1 (r=0.470, p=0.018) and showed a tendency toward correlation with plasma concentration of TSP-1 (r=0.382, p=0.059). Our findings show that the circulating TSP-1/VEGF balance is diminished in cancer patients. Platelet activation may play an important role in this decrease and may ultimately lead to increased angiogenic activity in these patients.

The matricellular protein TSP1 promotes human and mouse endothelial cell senescence through CD47 and Nox1

Senescent cells withdraw from the cell cycle and do not proliferate. The prevalence of senescent compared to normally functioning parenchymal cells increases with age, impairing tissue and organ homeostasis. A contentious principle governing this process has been the redox theory of aging. We linked matricellular protein thrombospondin 1 (TSP1) and its receptor CD47 to the activation of NADPH oxidase 1 (Nox1), but not of the other closely related Nox isoforms, and associated oxidative stress, and to senescence in human cells and aged tissue. In human endothelial cells, TSP1 promoted senescence and attenuated cell cycle progression and proliferation. At the molecular level, TSP1 increased Nox1-dependent generation of reactive oxygen species (ROS), leading to the increased abundance of the transcription factor p53. p53 mediated a DNA damage response that led to senescence through Rb and p21cip, both of which inhibit cell cycle progression. Nox1 inhibition blocked the ability of TSP1 to increase p53 nuclear localization and p21cip abundance and its ability to promote senescence. Mice lacking TSP1 showed decreases in ROS production, p21cip expression, p53 activity, and aging-induced senescence. Conversely, lung tissue from aging humans displayed increases in the abundance of vascular TSP1, Nox1, p53, and p21cip Finally, genetic ablation or pharmacological blockade of Nox1 in human endothelial cells attenuated TSP1-mediated ROS generation, restored cell cycle progression, and protected against senescence. Together, our results provide insights into the functional interplay between TSP1 and Nox1 in the regulation of endothelial senescence and suggest potential targets for controlling the aging process at the molecular level.

Discrimination between circulating endothelial cells and blood cell populations with overlapping phenotype reveals distinct regulation and predictive potential in cancer therapy

BACKGROUND

Circulating endothelial cells (CECs) have been proposed to predict patient response to antiangiogenic cancer therapy. However, contradictory reports and inconsistency in the phenotypic identification of CECs have led us to compare three cell populations with partially overlapping phenotype in cancer patients receiving chemotherapy and the antiangiogenic agent bevacizumab.

METHODS

Patients (n = 20) with locally advanced pancreatic cancer were monitored during 16 weeks of neoadjuvant treatment with gemcitabine and bevacizumab. Detection of circulating cell populations was based on the marker combination CD45, CD31, and CD146; levels of viable and dead (7-aminoactinomycin D-positive) cells were evaluated by flow cytometry in 2-week intervals.

RESULTS

We were able to discriminate and concomitantly monitor three cell populations elevated in cancer patients. Whereas CECs were defined as CD45(-) CD31(+) CD146(+), the distinct populations of CD45(-) CD31(-) CD146(+) and CD45(-) CD31(high) CD146(-) cells were partly positive for CD3 and CD41, respectively. CECs and CD45(-) CD31(-) CD146(+) cells increased during therapy; the rise in dead cells was positively correlated with patient response or survival. Conversely, CD45(-) CD31(high) CD146(-) cells decreased in neoadjuvant treatment. A highly significant correlation was established for improved patient response and a minor decrease in viable cell counts.

CONCLUSIONS

Flow cytometric CEC analysis based on CD45, CD31, and CD146 requires careful discrimination between blood cell populations with overlapping phenotype showing hallmarks of activated T cells and large platelets. However, these three cell populations show distinct regulation during cancer therapy, and their concomitant analysis may offer extended prognostic and predictive information.

Myelosuppression of thrombocytes and monocytes is associated with a lack of synergy between chemotherapy and anti-VEGF treatment

PURPOSE

Chemotherapeutic agents that have shown improved patient outcome when combined with anti-vascular endothelial growth factor (VEGF) therapy were recently identified to induce the mobilization of proangiogenic Tie-2-expressing monocytes (TEMs) and endothelial progenitor cells (EPCs) by platelet release of stromal cell-derived factor 1α (SDF-1α). VEGF blockade was found to counteract cell mobilization. We aimed to determine why agents like gemcitabine do not elicit TEM and EPC recruitment and may therefore lack synergy with anti-VEGF therapy.

EXPERIMENTAL DESIGN

Locally advanced pancreatic cancer patients (n = 20) were monitored during 16 weeks of neoadjuvant therapy. Treatment was based on gemcitabine with or without the addition of bevacizumab. Blood levels of proangiogenic cell populations and angiogenesis factors were determined in 2-week intervals.

RESULTS

The lack of EPC mobilization during gemcitabine therapy was associated with severe thrombocytopenia and reduced SDF-1α blood concentrations. Furthermore, myelosuppression by gemcitabine correlated significantly with loss of TEMs. With respect to angiogenic factors stored and released by platelets, plasma levels of the angiogenesis inhibitor thrombospondin 1 (TSP-1) were selectively decreased and correlated significantly with thrombocytopenia in response to gemcitabine therapy.

CONCLUSIONS

A thorough literature screen identified thrombocytopenia as a common feature of chemotherapeutic agents that lack synergy with anti-VEGF treatment. Our results on gemcitabine therapy indicate that myelosuppression (in particular, with respect to thrombocytes and monocytes) interferes with the mobilization of proangiogenic cell types targeted by bevacizumab and may further counteract antiangiogenic therapy by substantially reducing the angiogenesis inhibitor TSP-1.

Biological variations in plasma VEGF and VEGFR-1 may compromise their biomarker value in colorectal cancer

INTRODUCTION

Vascular Endothelial Growth Factor (VEGF) plays a prominent role in tumor angiogenesis and plasma VEGF concentration may carry prognostic information in colorectal cancer. The VEGF receptor 1 (VEGFR-1) is a regulatory receptor which is shredded into plasma of patients with colorectal cancer. For both molecules, large biological variation and lack of standardization of assay procedures are major challenges.

METHODS

We investigated pre-analytical, analytical, as well as short term and long term biological variation of plasma VEGF and VEGFR-1 in volunteers. In addition, we evaluated plasma VEGF and VEGFR-1 as markers of colorectal disease in a case-control study on four groups of 77 individuals undergoing bowel endoscopy. Groups were categorized as 'no findings', 'non-malignant findings', 'adenoma', or 'colorectal cancer'.

RESULTS

In the studies on variation, temperature and delay before centrifugation significantly influenced plasma VEGF and, to a minor extent, plasma VEGFR-1 concentrations. In addition, we found large biological variations with CV up to 69.2% for VEGF and CV up to 35.9% for VEGFR-1. For both molecules the intra-subject variation exceeded the inter-subject variation. In the case control study neither plasma VEGF nor VEGFR-1 was able to differentiate between the four groups of individuals although plasma VEGFR-1 was significantly lower in patients with 'no findings'.

CONCLUSION

There was no difference in plasma VEGF or VEGFR-1 between patients with no findings, benign disease, pre-malignant findings, and malignant findings after endoscopy. The poor discrimination between patients may be explained by the large inter- and intra-subject variations found for both molecules in volunteers.

A novel function for dendritic cell: clearance of VEGF via VEGF receptor-1

It has been reported that the plasma levels of VEGF in tumor patients decreased during dendritic cell (DC)-based immunotherapy, but the underlying mechanism remains unclear. Our current report demonstrates that VEGF levels were significantly decreased in the supernatants of DCs incubated with rhVEGF or tumor conditioned medium (TCM) while the intracellular VEGF in DCs was increased. The increased intracellular VEGF was not due to the de novo VEGF synthesis by DCs because exogenous VEGF inhibited the mRNA expression of VEGF in DCs. More direct evidence was provided to demonstrate that Cy3-labeled VEGF could be internalized by DCs specifically and efficiently. In addition, the activity of DCs to internalize VEGF was abolished by neutralizing antibody against VEGF receptor-1 (Flt-1) and inhibitors of endocytosis such as carbonyl cyanide m-chlorophenyl hydrazone (CCCP) and genistein. This study highlights a novel function of DCs and allows a better understanding of the DC-VEGF interaction.

Clinical biomarkers of angiogenesis inhibition

INTRODUCTION

An expanding understanding of the importance of angiogenesis in oncology and the development of numerous angiogenesis inhibitors are driving the search for biomarkers of angiogenesis. We review currently available candidate biomarkers and surrogate markers of anti-angiogenic agent effect.

DISCUSSION

A number of invasive, minimally invasive, and non-invasive tools are described with their potential benefits and limitations. Diverse markers can evaluate tumor tissue or biological fluids, or specialized imaging modalities.

CONCLUSIONS

The inclusion of these markers into clinical trials may provide insight into appropriate dosing for desired biological effects, appropriate timing of additional therapy, prediction of individual response to an agent, insight into the interaction of chemotherapy and radiation following exposure to these agents, and perhaps most importantly, a better understanding of the complex nature of angiogenesis in human tumors. While many markers have potential for clinical use, it is not yet clear which marker or combination of markers will prove most useful.

Neutralizing type I IFN antibodies trigger an IFN-like response in endothelial cells

Neutralizing Abs to type I IFNs are of therapeutic significance, i.e., are currently evaluated for the treatment of autoimmune diseases with pathogenic IFN-alpha production such as for systemic lupus erythematosus. Unexpectedly, we observed that several neutralizing Abs reportedly known to counteract IFN-alpha or IFN-beta activity triggered an "IFN-like" response in quiescent primary human endothelial cells leading to activation of the transcription factor IFN-stimulated gene factor 3 and the expression of IFN-responsive genes. Furthermore, these Abs were found to enhance rather than inhibit type I IFN signals, and the effect was also detectable for distinct other cell types such as PBMCs. The stimulatory capacity of anti-IFN-alpha/beta Abs was mediated by the constitutive autocrine production of "subthreshold" IFN levels, involved the type I IFNR and was dependent on the Fc Ab domain, as Fab or F(ab')(2) fragments potently inhibited IFN activity. We thus propose that a combined effect of IFN recognition by the Ab paratope and the concomitant engagement of the Fc domain may trigger an IFN signal via the respective type I IFNR, which accounts for the observed IFN-like response to the neutralizing Abs. With respect to clinical applications, the finding may be of importance for the design of recombinant Abs vs Fab or F(ab')(2) fragments to efficiently counteract IFN activity without undesirable activating effects.

Neoadjuvant treatment of colorectal cancer with bevacizumab: the perioperative angiogenic balance is sensitive to systemic thrombospondin-1 levels

PURPOSE

Colorectal cancer patients receiving neoadjuvant treatment with bevacizumab, a monoclonal antibody neutralizing vascular endothelial growth factor (VEGF), may suffer from wound healing complications after surgery as the antibody persists in patient blood. We characterized the systemic angiogenic balance in the perioperative period to evaluate its effect on physiologic angiogenesis.

EXPERIMENTAL DESIGN

Nineteen patients receiving combination chemotherapy and bevacizumab for six neoadjuvant cycles were compared with 14 patients receiving chemotherapy without bevacizumab. Plasma from perioperative days -1, +1, +7, and +21 was analyzed for VEGF, thrombospondin-1 (TSP-1), and PD-ECGF concentrations. The angiogenic capacity was further tested in an in vitro assay of endothelial cell proliferation and migration.

RESULTS

On day +1, the onset of wound healing was reflected in a change of balance, i.e., an increase of proangiogenic factors VEGF and platelet-derived endothelial cell growth factor compared with low TSP-1 inhibitor levels in both treatment groups. Patients with bevacizumab therapy showed significantly higher blood levels of total VEGF throughout the evaluation period. However, most VEGF molecules were inactive, i.e., complexed with antibody. Nevertheless, the capacity to stimulate endothelial growth was higher for these plasma samples and was reflected in low TSP-1 levels and an altered TSP-1 sensitivity. When purified TSP-1 protein was added, plasma samples of the bevacizumab but not the chemotherapy group showed reduced endothelial growth.

CONCLUSIONS

Feedback mechanisms of bevacizumab therapy are not restricted to VEGF expression but seem to involve additional factors, such as TSP-1, which influences the systemic angiogenic balance and permits endothelial growth.

Dendritic cells as potential adjuvant for immunotherapy in adrenocortical carcinoma

OBJECTIVE

Adrenocortical carcinoma (ACC) is a rare malignancy associated with a dismal prognosis. Dendritic cells (DCs) are professional antigen-presenting cells leading to an antitumour immune response. The aim of this study was to elaborate two methods of antigen delivery to DCs and to evaluate an immunotherapy protocol in ACC patients.

DESIGN/PATIENTS

Autologous DCs were pulsed with autologous tumour lysate (TL). Fusion of DCs with tumour cells was based on a polyethylene glycol method. Two patients with metastasized hypersecretory ACC were vaccinated twice.

MEASUREMENTS

In vitro data were quantified by measurement of PBMC (peripheral blood mononuclear cell) responses and cytokine secretion and by flow cytometry analyses. Clinical response was monitored by CT scan of tumour mass and measurement of angiogenic factors.

RESULTS

The maximum loading of TL was obtained at 24 h as 48.2% (+/- 26.8%) of DCs were TL-positive. The DC/tumour cell fusion efficacy was approximately 45% as shown by double positive staining for ACTH receptor and DC-specific CD83. In vivo DC vaccination resulted in positive delayed-type hypersensitivity skin reactions reflecting specific memory T-lymphocyte reaction. In vitro analyses revealed specific T-cell proliferation in patient 1 (stimulation index: 5.7 compared to pretreatment) and induction of cytotoxic granzyme B secreting T cells in patient 2 (0.41% CD8 + cells vs. 0.06% pretreatment) as indicators of specific cytotoxic T cells. Although angiogenic serum markers could be stabilized, no impact on tumour growth could be observed.

CONCLUSION

Our data demonstrate that autologous dendritic cells induce antigen-specific Th1 immunity in adrenocortical carcinoma. The clinical outcome, however, was not improved in the patients studied here.

Dendritic cell vaccination in medullary thyroid carcinoma

PURPOSE

Prognosis and treatment effectiveness for medullary thyroid carcinoma (MTC) are strictly related to tumor stage. Palliative treatment options show no significant benefit. A promising treatment approach for human cancer is based on the vaccination of autologous dendritic cells (DCs).

EXPERIMENTAL DESIGN

The objective of this study was to evaluate the effectiveness of DC vaccines in MTC patients. Therefore, we generated autologous tumor lysate-pulsed DCs from 10 patients suffering from advanced MTC for repeated vaccination. Mature DCs were derived from peripheral blood monocytes by using CD14 magnetic bead selection and subsequent culture in the presence of granulocyte macrophage colony-stimulating factor, interleukin 4, and tumor necrosis factor alpha with or without addition of IFN-gamma. DCs were loaded with tumor lysate and further injected into a groin lymph node. Toxicity, tumor marker profile, immune response, and clinical response were determined.

RESULTS

Vaccination was well tolerated and induced a positive immunological response in all of the tested patients as evaluated by in vivo delayed-type hypersensitivity reactivity or in vitro intracytoplasmic IFN-gamma detection assay. Three patients had a partial response, 1 patient presented a minor response, and 2 patients showed stable disease. The remaining 4 patients had progressive disease.

CONCLUSIONS

These data provide strong evidence that vaccination with tumor-lysate pulsed DCs results in the induction of a specific immune response in patients suffering from MTC. Objective clinical responses could be observed even for far-advanced disease. Therefore, we suggest that MTC is particularly suited for DC-based immunotherapy.