The Innate Immune System in Cardiovascular Diseases and Its Role in Doxorubicin-Induced Cardiotoxicity.

Innate immune cells are the early responders to infection and tissue damage. They play a critical role in the initiation and resolution of inflammation in response to insult as well as tissue repair. Following ischemic or non-ischemic cardiac injury, a strong inflammatory response plays a critical role in the removal of cell debris and tissue remodeling. However, persistent inflammation could be detrimental to the heart. Studies suggest that cardiac inflammation and tissue repair needs to be tightly regulated such that the timely resolution of the inflammation may prevent adverse cardiac damage. This involves the recognition of damage; activation and release of soluble mediators such as cytokines, chemokines, and proteases; and immune cells such as monocytes, macrophages, and neutrophils. This is important in the context of doxorubicin-induced cardiotoxicity as well. Doxorubicin (Dox) is an effective chemotherapy against multiple cancers but at the cost of cardiotoxicity. The innate immune system has emerged as a contributor to exacerbate the disease. In this review, we discuss the current understanding of the role of innate immunity in the pathogenesis of cardiovascular disease and dox-induced cardiotoxicity and provide potential therapeutic targets to alleviate the damage.

Bempegaldesleukin (BEMPEG; NKTR-214) efficacy as a single agent and in combination with checkpoint-inhibitor therapy in mouse models of osteosarcoma.

Survival of patients with relapsed/refractory osteosarcoma has not improved in the last 30 years. Several immunotherapeutic approaches have shown benefit in murine osteosarcoma models, including the anti-programmed death-1 (anti-PD-1) and anti-cytotoxic T-lymphocyte antigen-4 (anti-CTLA-4) immune checkpoint inhibitors. Treatment with the T-cell growth factor interleukin-2 (IL-2) has shown some clinical benefit but has limitations due to poor tolerability. Therefore, we evaluated the efficacy of bempegaldesleukin (BEMPEG; NKTR-214), a first-in-class CD122-preferential IL-2 pathway agonist, alone and in combination with anti-PD-1 or anti-CTLA-4 immune checkpoint inhibitors in metastatic and orthotopic murine models of osteosarcoma. Treatment with BEMPEG delayed tumor growth and increased overall survival of mice with K7M2-WT osteosarcoma pulmonary metastases. BEMPEG also inhibited primary tumor growth and metastatic relapse in lungs and bone in the K7M3 orthotopic osteosarcoma mouse model. In addition, it enhanced therapeutic activity of anti-CTLA-4 and anti-PD-1 checkpoint blockade in the DLM8 subcutaneous murine osteosarcoma model. Finally, BEMPEG strongly increased accumulation of intratumoral effector T cells and natural killer cells, but not T-regulatory cells, resulting in improved effector:inhibitory cell ratios. Collectively, these data in multiple murine models of osteosarcoma provide a path toward clinical evaluation of BEMPEG-based regimens in human osteosarcoma.

Up-regulation of pro-angiogenic molecules and events does not relate with an angiogenic switch in metastatic osteosarcoma cells but to cell survival features.

Osteosarcoma (OS) is the most frequent malignant bone tumor, affecting predominantly children. Metastases represent a major clinical challenge and an estimated 80% would present undetectable micrometastases at diagnosis. The identification of metastatic traits and molecules would impact in micrometastasis management. We demonstrated that OS LM7 metastatic cells secretome was able to induce microvascular endothelium cell rearrangements, an angiogenic-related trait. A proteomic analysis indicated a gain in angiogenic-related pathways in these cells, as compared to their parental-non-metastatic OS SAOS2 cells counterpart. Further, factors with proangiogenic functions like VEGF and PDGF were upregulated in LM7 cells. However, no differential angiogenic response was induced by LM7 cells in vivo. Regulation of the Fas-FasL axis is key for OS cells to colonize the lungs in this model. Analysis of the proteomic data with emphasis in apoptosis pathways and related processes revealed that the percentage of genes associated with those, presented similar levels in SAOS2 and LM7 cells. Further, the balance of expression levels of proteins with pro- and antiapoptotic functions in both cell types was subtle. Interestingly and of relevance to the model, Fas associated Factor 1 (FAF1), which participates in Fas signaling, was present in LM7 cells and was not detected in SAOS2 cells. The subtle differences in apoptosis-related events and molecules, together with the reported cell-survival functions of the identified angiogenic factors and the increased survival features that we observed in LM7 cells, suggest that the gain in angiogenesis-related pathways in metastatic OS cells would relate to a prosurvival switch rather to an angiogenic switch as an advantage feature to colonize the lungs. OS metastatic cells also displayed higher adhesion towards microvascular endothelium cells suggesting an advantage for tissue colonization. A gain in angiogenesis pathways and molecules does not result in major angiogenic potential. Together, our results suggest that metastatic OS cells would elicit signaling associated to a prosurvival phenotype, allowing homing into the hostile site for metastasis. During the gain of metastatic traits process, cell populations displaying higher adhesive ability to microvascular endothelium, negative regulation of the Fas-FasL axis in the lung parenchyma and a prosurvival switch, would be selected. This opens a new scenario where antiangiogenic treatments would affect cell survival rather than angiogenesis, and provides a molecular panel of expression that may help in distinguishing OS cells with different metastatic potential.

Anthracycline-Induced Cardiotoxicity: Causes, Mechanisms, and Prevention.

Doxorubicin is an anthracycline and one of the more effective chemotherapy agents used in the treatment of children, adolescents, and adults with osteosarcoma. Despite its effectiveness, cardiotoxicity is a major late effect that compromises the survival and quality of life of survivors of this and other cancers. Cardiotoxicity is the inability of the heart to pump blood through the body effectively. Doxorubicin-induced cardiotoxicity is dose dependent. Additionally, the age of the patients plays a role in susceptibility with younger patients having a greater risk for cardiotoxicity and heart failure years after treatment is complete. The exact mechanism(s) responsible for doxorubicin-induced cardiotoxicity is poorly understood, and further research needs to be done to elucidate the mechanisms. This chapter summarizes the identified mechanisms that may play a role in anthracycline-induced cardiotoxicity. We will also summarize the types of cardiomyopathies that have been described in survivors treated with doxorubicin and the current recommendations for monitoring survivor for the development of cardiomyopathies. Included will be the important search for defining early biomarkers to identify patients and survivors at risk. Finally, we will summarize some of the interventions proposed for decreasing anthracycline-induced cardiotoxicity.

The Fas/FasL Signaling Pathway: Its Role in the Metastatic Process and as a Target for Treating Osteosarcoma Lung Metastases.

Understanding how the tumor microenvironment participates in inhibiting or supporting tumor growth is critical for the development of novel therapies. Osteosarcoma (OS) metastasizes almost exclusively to the lung, an organ where Fas ligand (FasL) is constitutively expressed. This chapter focuses on our studies dedicated to the interaction of OS cells with the lung microenvironment. We will summarize our studies conducted over the past 20 years showing the importance of the Fas/FasL signaling pathway to the establishment and progression of OS metastases in the lung. We demonstrated that the FasL+ lung microenvironment eliminates Fas-positive (Fas+) OS cells that metastasize to the lungs, through apoptosis induced by Fas signaling following interaction of Fas on the tumor cell surface with FasL on the lung epithelial cells. Expression of the Fas receptor on OS cells inversely correlated with the ability of OS cells to form lung metastases. Blocking this pathway interferes with this process, allowing Fas+ cells to grow in the lung. By contrast, upregulation of Fas on Fas- OS cells inhibited their ability to metastasize to the lung. We demonstrated how the FasL+ lung microenvironment can be leveraged for therapeutic intent through the upregulation of Fas expression. To this end, we demonstrated that the histone deacetylase inhibitor entinostat upregulated Fas expression on OS cells, reduced their ability to form lung metastases, and induced regression of established micrometastases. Fas expression in OS cells is regulated epigenetically by the microRNA miR-20a. We showed that expressions of Fas and miR-20a are inversely correlated, and that delivery of anti-miR-20a in vivo to mice with established osteosarcoma lung metastases resulted in upregulation of Fas and tumor regression. Therefore, targeting the Fas signaling pathway may present therapeutic opportunities, which target the lung microenvironment for elimination of OS lung metastases. We have also shown that in addition to being critically involved in the metastatic potential, the Fas signaling pathway may also contribute to the efficacy of chemotherapy. We demonstrated that the chemotherapeutic agent gemcitabine (GCB) increased Fas expression in both human and mouse OS cells in vitro. In vivo, aerosol GCB therapy induced upregulation of Fas expression and the regression of established osteosarcoma lung metastases. The therapeutic efficacy of GCB was contingent upon a FasL+ lung microenvironment as aerosol GCB had no effect in FasL-deficient mice. Manipulation of Fas expression and the Fas pathway should be considered, as this concept may provide additional novel therapeutic approaches for treating patients with OS lung metastases.

Exosomes: Dynamic Mediators of Extracellular Communication in the Tumor Microenvironment.

It is becoming increasingly recognized that the tumor microenvironment significantly contributes to the development, progression, and metastasis of cancer and also plays a role in response to treatment. The tumor microenvironment is a complex and heterogeneous niche comprised of stromal cells, cancer cells, blood vessels, areas of hypoxia and necrotic tissue, fibrosis, and extracellular matrix. Cellular communication takes place within the tumor microenvironment, both via cell to cell contact, and through extracellular mechanisms such as exosomal signaling. Exosomes are very small membrane-bound vesicles that have been shown to play key roles in the progression of cancer including modulation of the tumor microenvironment through the induction of angiogenesis, the transfer of genetic information that confers drug resistance, and increased cell migration, invasion, proliferation, and survival, as well as the modulation of immune cell interactions. The role of exosomes in several different cancers has been investigated. In the context of osteosarcoma, understanding how exosomes may modulate the tumor microenvironment to support metastatic growth particularly in the lung, the most common site of metastases, may identify novel therapeutic targets for relapsed patients.

BMTP-11 is active in preclinical models of human osteosarcoma and a candidate targeted drug for clinical translation.

Osteosarcoma occurs predominantly in children and young adults. High-grade tumors require multidisciplinary treatment consisting of chemotherapy in the neoadjuvant and adjuvant settings, along with surgical intervention. Despite this approach, death from respiratory failure secondary to the development and progression of pulmonary metastases remains a significant problem. Here, we identify the IL-11 receptor α subunit (IL-11Rα) as a cell surface marker of tumor progression that correlates with poor prognosis in patients with osteosarcoma. We also show that both IL-11Rα and its ligand, IL-11, are specifically up-regulated in human metastatic osteosarcoma cell lines; engagement of this autocrine loop leads to tumor cell proliferation, invasion, and anchorage-independent growth in vitro. Consistently, IL-11Rα promotes lung colonization by human metastatic osteosarcoma cells in vivo in an orthotopic mouse model. Finally, we evaluate the IL-11Rα-targeted proapoptotic agent bone metastasis-targeting peptidomimetic (BMTP-11) in preclinical models of primary intratibial osteosarcomas, observing marked inhibition of both tumor growth and lung metastases. This effect was enhanced when BMTP-11 was combined with the chemotherapeutic drug gemcitabine. Our combined data support the development of approaches targeting IL-11Rα, and establish BMTP-11 as a leading drug candidate for clinical translation in patients with high-risk osteosarcoma.

Vascular modulation through exercise improves chemotherapy efficacy in Ewing sarcoma.

Recent studies in mouse models of cancer have shown that exercise improves tumor vascular function, thereby improving chemotherapy delivery and efficacy. However, the mechanisms underlying this improvement remain unclear and the effect of exercise on Ewing sarcoma (ES), a pediatric bone and soft tissue cancer, is unknown. The effect of exercise on tumor vascular hyperpermeability, which inversely correlates with drug delivery to the tumor, has also not been evaluated. We hypothesized that exercise improves chemotherapy efficacy by enhancing its delivery through improving tumor vascular permeability. We treated ES-bearing mice with doxorubicin with or without moderate treadmill exercise. Exercise did not significantly alter ES tumor vessel morphology. However, compared to control mice, tumors of exercised mice had significantly reduced hyperpermeability, significantly decreased hypoxia, and higher doxorubicin penetration. Compared to doxorubicin alone, doxorubicin plus exercise inhibited tumor growth more efficiently. We evaluated endothelial cell sphingosine-1-phosphate receptors 1 and 2 (S1PR1 and S1PR2) as potential mediators of the improved vascular permeability and increased function afforded by exercise. Relative to tumors from control mice, vessels in tumors from exercised mice had increased S1PR1 and decreased S1PR2 expression. Our results support a model in which exercise remodels ES vasculature to reduce vessel hyperpermeability, potentially via modulation of S1PR1 and S1PR2, thereby improving doxorubicin delivery and inhibiting tumor growth more than doxorubicin alone does. Our data suggest moderate aerobic exercise should be tested in clinical trials as a potentially useful adjuvant to standard chemotherapy for patients with ES.

Diet and exercise interventions for pediatric cancer patients during therapy: tipping the scales for better outcomes.

Obesity at diagnosis is a negative prognostic indicator for several pediatric cancers including acute leukemia and bone tumors. Incidence of obesity in children has increased three-fold over the past 2 decades, and causes for this include poor diet, excessive caloric intake, and lack of physical activity, which are collectively referred to as energy balance-related behaviors. Few energy balance interventions have been implemented in pediatric cancer patients during treatment, and here we will probe the rationale for pursuing such studies. The need to modify composition of calories consumed and to identify specific beneficial exercise regimens will be discussed, relative to weight reduction or management.

The narrow-spectrum HDAC inhibitor entinostat enhances NKG2D expression without NK cell toxicity, leading to enhanced recognition of cancer cells.

PURPOSE: Natural killer (NK) cell cytotoxicity correlates with the ligation of activating receptors (e.g., NKG2D) by their ligands (e.g., MHC class I-related chains [MIC] A and B) on target cells. Histone deacetylase inhibitors (HDACi) at high concentrations inhibit tumor growth and can increase NKG2D ligand expression on tumor targets, but are widely regarded as toxic to NK cells. METHODS: We investigated the mechanism of entinostat, a benzamide-derivative narrow-spectrum HDACi, in augmenting the cytotoxicity of NK cells against human colon carcinoma and sarcoma by assessing gene and protein expression, histone acetylation, and cytotoxicity in in vitro and murine models. RESULTS: We observed that entinostat dose- and time-dependent increase in MIC expression in tumor targets and NKG2D in primary human NK cells, both correlating with increased acetylated histone 3 (AcH3) binding to associated promoters. Entinostat pretreatment of colon carcinoma and sarcoma cells, NK cells, or both led to enhanced overall cytotoxicity in vitro, which was reversed by NKG2D blockade, and inhibited growth of tumor xenografts. Lastly, we showed decreased expression of MICA and ULBP2 transcription in primary human osteosarcoma. CONCLUSIONS: Entinostat enhances NK cell killing of cancer cells through upregulation of both NKG2D and its ligands, suggesting an attractive approach for augmenting NK cell immunotherapy of solid tumors such as colon carcinoma and sarcomas.

CD8+T cell-specific induction of NKG2D receptor by doxorubicin plus interleukin-12 and its contribution to CD8+T cell accumulation in tumors.

BACKGROUND: Increased infiltration of CD8+T cells into tumors has a positive impact on survival. Our previous study showed that doxorubicin (Dox) plus interleukin-12 (IL-12) boosted the accumulation of CD8+T cells in tumors and had a greater antitumor effect than did either agent alone. The purpose of this study was to determine the impact of NKG2D expression on CD8+T cell infiltration and antitumor efficacy. METHODS: Tumor-bearing mice were administered Dox, IL-12 plasmid DNA, or both via intraperitoneal injection or intramuscular electroporation. The induction of NKG2D on CD8+T cells and other lymphocytes was analyzed via flow cytometry, and NKG2D-positive CD8+T cell-specific localization in tumors was determined by using immunofluorescence staining in various types of immune cell-depleted mice. RESULTS: The combination of Dox plus IL-12 specifically increased expression of NKG2D in CD8+T cells but not in other types of immune cells, including NK cells, which naturally express NKG2D. This induced NKG2D expression in CD8+T cells was associated with increased accumulation of CD8+T cells in murine tumors. Administration of NKG2D-blocking antibody or CD8+T cell-depletion antibody abrogated the NKG2D+CD8+T cell detection in tumors, whereas administration of NK cell-depletion antibody had no effect. Increased NKG2D expression in CD8+T cells was associated with increased antitumor efficacy in vivo. CONCLUSION: We conclude that Dox plus IL-12 induces NKG2D in CD8+T cells in vivo and boosts NKG2D+CD8+T-dependent antitumor immune surveillance. This discovery reveals a novel mechanism for how chemoimmunotherapy synergistically promotes T cell-mediated antitumor immune surveillance.

EWS-FLI-1 regulates the neuronal repressor gene REST, which controls Ewing sarcoma growth and vascular morphology.

BACKGROUND: RE1-silencing transcription factor (REST), a neuronal repressor gene, regulates neuronal stem cell differentiation. Ewing sarcoma may originate from neural crest cells. In the current study, the authors investigated whether REST plays a role in the growth of this tumor. METHODS: REST expression was determined by Western blot analysis and reverse transcription-polymerase chain reaction in 3 human Ewing sarcoma cell lines and 7 patient tumor samples. The role of REST in tumor growth and tumor vascular morphology was determined using a Ewing sarcoma xenograft model. Immunofluorescence staining, Hypoxyprobe, and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assays were performed to investigate the impact of REST on pericyte marker expression, hypoxia, and apoptosis in vivo. RESULTS: High levels of REST were expressed in all 3 human Ewing sarcoma cell lines and in 6 of the 7 patient tumor samples. Overexpression of EWS-FLI-1 in human mesenchymal stem cells and human neural progenitor cells was found to increase REST expression. Inhibition of EWS-FLI-1 using small interfering RNA decreased REST expression in human Ewing sarcoma cells. Inhibition of REST did not affect EWS-FLI-1, but significantly suppressed tumor growth in vivo, reduced the tumor vessel pericyte markers α- smooth muscle actin (SMA) and desmin, increased hypoxia and apoptosis in tumor tissues, and decreased the expression of delta-like ligand 4 (DLL4) and Hes1. CONCLUSIONS: Inhibition of REST suppressed tumor growth, inhibited pericyte marker expression, and increased tumor hypoxia and apoptosis. Because tumor vessel function has been linked to tumor growth and metastases, REST may be a new therapeutic target in patients with Ewing sarcoma.

Aerosol interleukin-2 induces natural killer cell proliferation in the lung and combination therapy improves the survival of mice with osteosarcoma lung metastasis.

BACKGROUND: We have previously shown that aerosol interleukin-2 (IL-2) increased the number of intravenously injected human natural killer (NK) cells in the lungs. In this study we investigated whether this increase was secondary to NK cell proliferation and determined the site of the proliferation. MATERIALS AND METHODS: Nude mice with osteosarcoma lung metastases were injected with NK cells and treated with aerosol IL-2 or aerosol PBS. BrdU was injected prior to euthanasia to identify proliferating NK cells. The percentage of proliferating NK cells in the lung, bone marrow, spleen, and liver was determined using flow cytometry. Survival studies for mice with osteosarcoma lung metastasis treated with aerosol PBS, aerosol IL-2 alone, aerosol PBS plus NK cells, and aerosol IL-2 plus NK cells were also performed. RESULTS: Treatment with aerosol IL-2 induced the proliferation of injected NK cells in the lung. Aerosol IL-2 did not increase the proliferation of NK cells in the spleen and liver. Treatment with aerosol IL-2 and aerosol IL-2 plus NK cells increased the overall survival of mice with osteosarcoma lung metastasis. CONCLUSION: Aerosol IL-2 increases lung NK cell numbers by stimulating local NK cell proliferation. Aerosol IL-2's effect on NK cell proliferation is organ specific, which makes it ideal for the specific targeting of lung metastasis. Aerosol IL-2 plus NK cell therapy induced metastatic regression and increased overall survival demonstrating the potential of this therapeutic approach for patients with osteosarcoma.

Natural killer cell therapy and aerosol interleukin-2 for the treatment of osteosarcoma lung metastasis.

BACKGROUND: Survival of patients with osteosarcoma lung metastases has not improved in 20 years. We evaluated the efficacy of combining natural killer (NK) cells with aerosol interleukin-2 (IL-2) to achieve organ-specific NK cell migration and expansion in the metastatic organ, and to decrease toxicity associated with systemic IL-2. PROCEDURE: Five human osteosarcoma cell lines and 103 patient samples (47 primary and 56 metastatic) were analyzed for NKG2D ligand (NKG2DL) expression. Therapeutic efficacy of aerosol IL-2 + NK cells was evaluated in vivo compared with aerosol IL-2 alone and NK cells without aerosol IL-2. RESULTS: Osteosarcoma cell lines and patient samples expressed various levels of NKG2DL. NK-mediated killing was NKG2DL-dependent and correlated with expression levels. Aerosol IL-2 increased NK cell numbers in the lung and within metastatic nodules but not in other organs. Therapeutic efficacy, as judged by tumor number, size, and quantification of apoptosis, was also increased compared with NK cells or aerosol IL-2 alone. There were no IL-2-associated systemic toxicities. CONCLUSION: Aerosol IL-2 augmented the efficacy of NK cell therapy against osteosarcoma lung metastasis, without inducing systemic toxicity. Our data suggest that lung-targeted IL-2 delivery circumvents toxicities induced by systemic administration. Combining aerosol IL-2 with NK cell infusions, may be a potential new therapeutic approach for patients with osteosarcoma lung metastasis.

Participation of the Fas/FasL signaling pathway and the lung microenvironment in the development of osteosarcoma lung metastases.

The lungs are the most common site for the metastatic spread of osteosarcoma. Success in using chemotherapy to improve overall survival has reached a plateau. Understanding the biologic properties that permit osteosarcoma cells to grow in the lungs may allow the identification of novel therapeutic approaches-the goal being to alter the tumor cells' expression of cell surface proteins so that there is no longer compatibility with the metastatic niche. We have demonstrated that the Fas Ligand positive (FasL(+)) lung microenvironment eliminates Fas(+) osteosarcoma cells that metastasize to the lungs. Indeed, osteosarcoma lung metastases from patients are Fas(-), similar to what we found in several different mouse models. The Fas(+) cells are cleared from the lungs through apoptosis induced by the Fas signaling pathway following interaction of Fas on the tumor cell surface with the lung FasL. Blocking the Fas signaling pathway interferes with this process, allowing the Fas(+) cells to grow in the lungs. Our investigations show that Fas expression in osteosarcoma cells is regulated epigenetically by the micro-RNA miR-20a, encoded by the miR-17-92 cluster. Our studies support the feasibility of finding agents that can re-induce Fas expression as a novel therapeutic approach to treat osteosarcoma patients with lung metastases. We have identified two such agents, the histone deacetylase inhibitor entinostat and the chemotherapeutic agent gemcitabine (GCB). Aerosol GCB and oral entinostat induce the upregulation of Fas and the regression of established osteosarcoma lung metastases. Aerosol GCB was not effective in the FasL-deficient gld mouse confirming that the lung microenvironment was central to the success of this therapy. Our studies establish the critical role of the lung microenvironment in the metastatic process of osteosarcoma to the lungs and suggest an alternative focus for therapy, that is, incorporating the lung microenvironment as part of the treatment strategy against established osteosarcoma disease in the lungs.

CD103+ cDC1 Dendritic Cell Vaccine Therapy for Osteosarcoma Lung Metastases.

BACKGROUND: We generated a CD103+DC vaccine using K7M3 OS cell lysates (cDCV) and investigated its ability to induce regression of primary tumors, established lung metastases, and a systemic immune response. METHODS: A bilateral tumor model was used to assess cDCV therapy efficacy and systemic immunity induction. K7M3 cells were injected into mice bilaterally. Right-sided tumors received PBS (control) or cDCV. Left-sided tumors were untreated. Tumor growth was compared between the vaccine-treated and untreated tumor on the contralateral side and compared to the control group. The immune cell profiles of the tumors, and tumor-draining lymph nodes (TdLNs) and spleen were evaluated. To determine the efficacy of systemic cDCV therapy against established lung metastases, K7M3 cells were injected intratibially. Leg amputation was performed 5 weeks later. Mice were treated intravenously with PBS or cDCV and euthanized 6 weeks later. Lungs, TdLNs and spleen were collected. The number and size of the lung nodules were quantified. The immune cell profile of tumor, and lymph nodes and spleen were also evaluated. Using this same model, we evaluated the effect of cDCV + anti-CTLA-4. RESULTS: cDCV therapy inhibited the treated and untreated tumors and increased the number of T-cells in these tumors and the lymph nodes compared to control-treated mice. Systemic cDCV therapy administered following amputation decreased the size and number of lung metastases, and increased T-cell numbers in the tumor and lymph nodes. Combining anti-CTLA-4 with cDCV therapy increased cDCV efficacy against lung metastases. CONCLUSIONS: Intratumor cDCV generated a systemic immune response inhibiting the growth of both the treated and untreated tumors, with increased T-cells in the tumor and lymph nodes. Systemic cDCV was effective against established lung metastases. Efficacy was increased by anti-CTLA4. cDCVs may provide a novel therapeutic approach for relapsed/metastatic OS patients.

Delta-like ligand 4-Notch signaling regulates bone marrow-derived pericyte/vascular smooth muscle cell formation.

Delta-like ligand 4 (DLL4) is essential for the formation of mature vasculature. However, the role of DLL4-Notch signaling in pericyte/vascular smooth muscle cell (vSMC) development is poorly understood. We sought to determine whether DLL4-Notch signaling is involved in pericyte/vSMC formation in vitro and during vasculogenesis in vivo using 2 Ewing sarcoma mouse models. Inhibition of DLL4 with the antibody YW152F inhibited pericyte/vSMC marker expression by bone marrow (BM) cells in vitro. Conversely, transfection of 10T1/2 cells with the active domains of Notch receptors led to increased expression of pericyte/vSMC markers. Furthermore, the blood vessels of Ewing sarcoma tumors from mice treated with YW152F had reduced numbers of BM-derived pericytes/vSMCs, fewer open lumens, and were less functional than the vessels in tumors of control-treated mice. Tumor growth was also inhibited. These data demonstrate a specific role for DLL4 in the formation of BM-derived pericytes/vSMCs and indicate that DLL4 may be a novel therapeutic target for the inhibition of vasculogenesis.

Knockdown of autophagy-related protein 5, ATG5, decreases oxidative stress and has an opposing effect on camptothecin-induced cytotoxicity in osteosarcoma cells.

BACKGROUND: Autophagy induction can increase or decrease anticancer drug efficacy. Anticancer drug-induced autophagy induction is poorly characterized in osteosarcoma (OS). In this study, we investigated the impact of autophagy inhibition on camptothecin (CPT)-induced cytotoxicity in OS. METHODS: Autophagy-inhibited DLM8 and K7M3 metastatic murine OS cell lines were generated by infection with lentiviral shRNA directed against the essential autophagy protein ATG5. Knockdown of ATG5 protein expression and inhibition of autophagy was confirmed by immunoblot of ATG5 and LC3II proteins, respectively. Metabolic activity was determined by MTT assay and cell viability was determined by trypan blue exclusion. Acridine orange staining and immunoblotting for LC3II protein expression were used to determine autophagy induction. Oxidative stress was assessed by staining cells with HE and DCFH-DA followed by flow cytometry analysis. Mitochondrial membrane potential was determined by staining cells with TMRE followed by flow cytometry analysis. Immunoblotting was used to detect caspase activation, Parp cleavage and p53 phosphorylation. RESULTS: Autophagy inhibition caused a greater deficit in metabolic activity and cell growth in K7M3 cells compared to DLM8 cells. K7M3 cells exhibited higher basal autophagy levels than DLM8 cells and non-transformed murine MCT3 osteoblasts. Autophagy inhibition did not affect CPT-induced DNA damage. Autophagy inhibition decreased CPT-induced cell death in DLM8 cells while increasing CPT-induced cell death in K7M3 cells. Autophagy inhibition reduced CPT-induced mitochondrial damage and CPT-induced caspase activation in DLM8 cells. Buthionine sulfoximine (BSO)-induced cell death was greater in autophagy-competent DLM8 cells and was reversed by antioxidant pretreatment. Camptothecin-induced and BSO-induced autophagy induction was also reversed by antioxidant pretreatment. Significantly, autophagy inhibition not only reduced CPT-induced oxidative stress but also reduced basal oxidative stress. CONCLUSIONS: The results of this study indicate that autophagy inhibition can have an opposing effect on CPT-induced cytotoxicity within OS. The cytoprotective mechanism of autophagy inhibition observed in DLM8 cells involves reduced CPT-induced oxidative stress and not reduced DNA damage. Our results also reveal the novel finding that knockdown of ATG5 protein reduces both basal oxidative stress and drug-induced oxidative stress.

Expression of c-FLIP in pulmonary metastases in osteosarcoma patients and human xenografts.

OBJECTIVE(S): We have previously shown that Fas expression inversely correlates with the metastatic potential of osteosarcoma (OS) to the lung. FasL is constitutively expressed in the lung microenvironment and eliminates Fas(+) OS cells leaving Fas(-) cells to form metastases. Absence of FasL in the lung epithelium or blocking the Fas-signaling pathway interfered with this clearance mechanism allowing Fas(+) cells to remain and form lung metastases. We also demonstrated that while the majority of patient OS lung metastases were Fas(-), 10-20% of the lesions contained Fas(+) cells, suggesting that these cells were not sensitive to FasL-induced apoptosis. The expression of c-FLIP, an inhibitor of the Fas pathway, has been associated with tumor development, progression, and resistance to chemotherapy. We therefore evaluated the expression of c-FLIP in OS patient tumor specimens and human xenograft lung metastases. METHODS: OS patient tissues, which included both primary and metastatic lesions, were evaluated for the expression of c-FLIP. In addition, tumors from human OS xenografts were examined for c-FLIP expression. RESULTS: c-FLIP expression was significantly higher in the lung metastases than in the primary tumors. CONCLUSION(S): c-FLIP may play an important role in the metastatic potential of OS to the lung. Inhibition of c-FLIP may be a future therapeutic target.

Early skeletal muscle loss in adolescent and young adult cancer patients treated with anthracycline chemotherapy.

BACKGROUND: Early skeletal muscle loss has been observed in adolescent and young adult (AYA) sarcoma patients undergoing treatment. Identification of individuals within the AYA populace that are at greatest risk of anthracycline-induced skeletal muscle loss is unknown. Moreover, investigations which seek out underlying causes of skeletal muscle degradation during chemotherapy are critical for understanding, preventing, and reducing chronic health conditions associated with poor skeletal muscle status. METHODS: Computed tomography (CT) scans were used to investigate changes in skeletal muscle of 153 AYA sarcoma and Hodgkin lymphoma patients at thoracic vertebra 4 after anthracycline treatment. Images were examined at three time points during the first year of treatment. In parallel, we used translational juvenile mouse models to assess the impact of doxorubicin (DOX) in the soleus and gastrocnemius on muscle wasting. RESULTS: Significant reductions in total skeletal muscle index and density were seen after chemotherapy in AYA cancer patients (p < 0.01 & p = 0.04, respectively). The severity of skeletal muscle loss varied by subgroup (i.e., cancer type, sex, and treatment). Murine models demonstrated a reduction in skeletal muscle fiber cross-sectional area, increased apoptosis and collagen volume for both the soleus and gastrocnemius after DOX treatment (all p < 0.05). After DOX, hindlimb skeletal muscle blood flow was significantly reduced (p < 0.01). CONCLUSION: Significant skeletal muscle loss is experienced early during treatment in AYA cancer patients. Reductions in skeletal muscle blood flow may be a key contributing factor to anthracycline doxorubicin induced skeletal muscle loss.