Non-viral nitric oxide-based gene therapy improves perfusion and liposomal doxorubicin sonopermeation in neuroblastoma models

Neuroblastoma (NB) is a pediatric malignancy that accounts for 15% of cancer-related childhood mortality. High-risk NB requires an aggressive chemoradiotherapy regimen that causes significant off-target toxicity. Despite this invasive treatment, many patients either relapse or do not respond adequately. Recent studies suggest that improving tumor perfusion can enhance drug accumulation and distribution within the tumor tissue, potentially augmenting treatment effects without inflicting systemic toxicity. Accordingly, methods that transiently increase tumor perfusion prior to treatment may help combat this disease. Here, we show the use of gene therapy to confer inducible nitric oxide synthase (iNOS) expression solely in the tumor space, using focused ultrasound targeting. NOS catalyzes the reaction that generates nitric oxide (NO), a potent endogenous vasodilator. This study reports the development of a targeted non-viral image-guided platform to deliver iNOS-expressing plasmid DNA (pDNA) to vascular endothelial cells encasing tumor blood vessels. Following transfection, longitudinal quantitative contrast-enhanced ultrasound (qCEUS) imaging revealed an increase in tumor perfusion over 72 h, attributed to elevated intratumoral iNOS expression. Methods: To construct a gene delivery vector, cationic ultrasound-responsive agents (known as "microbubbles") were employed to carry pDNA in circulation and transfect tumor vascular endothelial cells in vivo using focused ultrasound (FUS) energy. This was followed by liposomal doxorubicin (L-DOX) treatment. The post-transfection tumor response was monitored longitudinally using qCEUS imaging to determine relative changes in blood volumes and perfusion rates. After therapy, ex vivo analysis of tumors was performed to examine the bioeffects associated with iNOS expression. Results: By combining FUS therapy with cationic ultrasound contrast agents (UCAs), we achieved selective intratumoral transfection of pDNA encoding the iNOS enzyme. While transitory, the degree of expression was sufficient to induce significant increases in tumoral perfusion, to appreciably enhance the chemotherapeutic payload and to extend survival time in an orthotopic xenograft model. Conclusion: We have demonstrated the ability of a novel targeted non-viral gene therapy strategy to enhance tumor perfusion and improve L-DOX delivery to NB xenografts. While our results demonstrate that transiently increasing tumor perfusion improves liposome-encapsulated chemotherapeutic uptake and distribution, we expect that our iNOS gene delivery paradigm can also significantly improve radio and immunotherapies by increasing the delivery of radiosensitizers and immunomodulators, potentially improving upon current NB treatment without concomitant adverse effects. Our findings further suggest that qCEUS imaging can effectively monitor changes in tumor perfusion in vivo, allowing the identification of an ideal time-point to administer therapy.

Histotripsy induces apoptosis and reduces hypoxia in a neuroblastoma xenograft model

BACKGROUND

Neuroblastoma (NB) is the most common extracranial solid tumor of childhood, and high-risk disease is resistant to intensive treatment. Histotripsy is a focused ultrasound therapy under development for tissue ablation via bubble activity. The goal of this study was to assess outcomes of histotripsy ablation in a xenograft model of high-risk NB.

METHODS

Female NCr nude mice received NGP-luciferase cells intrarenally. Under ultrasound image guidance, histotripsy pulses were applied over a distance of 4-6 mm within the tumors. Bioluminescence indicative of tumor viability was quantified before, immediately after, and 24 h after histotripsy exposure. Tumors were immunostained to assess apoptosis (TUNEL), endothelium (endomucin), pericytes (αSMA), hypoxia (pimonidazole), vascular endothelial growth factor A (VEGFA), and platelet-derived growth factor-B (PDGF-B). The apoptotic cytokine TNFα and its downstream effector cleaved caspase-3 (c-casp-3) were assessed with SDS-PAGE.

RESULTS

Histotripsy induced a 50% reduction in bioluminescence compared to untreated controls, with an absence of nuclei in the treatment core surrounded by a dense rim of TUNEL-positive cells. Tumor regions not targeted by histotripsy also showed an increase in TUNEL staining density. Increased apoptosis in histotripsy samples was consistent with increases in TNFα and c-casp-3 relative to controls. Treated tumors exhibited a decrease in hypoxia, VEGF, PDGF-B, and pericyte coverage of vasculature compared to control samples. Further, increases in vasodilation were found in histotripsy-treated specimens.

CONCLUSIONS

In addition to ablative effects, histotripsy was found to drive tumor apoptosis through intrinsic pathways, altering blood vessel architecture, and reducing hypoxia.

Abstract 376: Sonoporated size selected microbubblesand liposomal doxorubicinadditively induce apoptosis in neuroblastoma xenografts

Background: Neuroblastoma (NB) is the second most common malignancy diagnosed in infants, accounting for 15% of pediatric tumor deaths. Half of children with NB receive an intensive regimen including high-dose chemotherapy with 50% survival, resulting in acute and long term toxicities. One of the challenges of chemotherapy is irregular tumor vasculature. Thus, increasing targeted drug delivery without increasing drug dosage can result in enhanced drug efficacy and improved patient outcomes. We have shown that sonoporation (focused ultrasound-guided gas-filled microbubbles) increases high dose liposomal doxorubicin (L-DOX) uptake in NB xenografts by increasing tumor perfusion. However, these studies used polydisperse microbubbles (PMB), which were developed for imaging purposes. We hypothesized that MB size restriction would control their response to ultrasound pressure, yielding a higher L-DOX payload despite using using lower L-DOX dosages.

Methods: Nude mice received 1x10^6 NGP cells (NB cells) intrarenally. When tumors reached 1 gram, NB xenografts received an intravenous polydisperse (PMB) or 4-5uM (SIMB) microbubble infusion with or without 1mg/kg liposomal doxorubicin (L-DOX) under focused ultrasound. Tumors were measured over 7 days with calipers, others sacrificed 24 hours after treatment for histology and immunohistochemistry. We assessed endomucin and isolectin-B4 (endothelium), Zona occludens-1 (ZO-1) (tight junction), and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL, apoptosis).

Results: Tumors receiving low dose L-DOX alone or PMB sonoporation with L-DOX were not different from untreated controls after 7 days. SIMB alone resulted in a slower tumor growth than control tumors (20 vs 100% p<0.05); L-DOX coupled with SIMB resulted in further tumor growth restriction 7 days after treatment (0 vs 100% p<0.05). SIMB increased tumor apoptosis (TUNEL staining) in the absence of L-DOX compared to controls (7 vs 58% of area p=0.003) as well as in the presence of L-DOX (7 vs 78% of area p<0.001). PMBs did not change TUNEL levels regardless of L-DOX. Tumor vascular lumens (widest axis within the endothelial marker endomucin) confirmed PMB duplicates lumen diameter compared to controls (p<0.05), and revealed SIMB triplicates lumen diameter (p<0.01) regardless of L-DOX. SIMB resulted in loss of tight junction protein ZO-1 both in vasculature and tumor cells and widespread L-DOX uptake. Together, our data shows SIMB sonoporation increases tumor blood volume and vascular permeability leading to higher chemotherapy uptake and apoptosis.

Conclusions: Together, our data shows SIMB sonoporation enables chemotherapy uptake in poorly perfused NB xenografts by increasing perfusion and permeability, potentiating apoptotic effects. SIMB sonoporation could reduce acute and long term toxicities.

Citation Format: Sonia L. Hernandez, Rachael Sundland, Donia Ballan, Aditi Bellary, Jessica J. Kandel, Jameel Feshitan, Shashank Sirsi. Sonoporated size selected microbubblesand liposomal doxorubicinadditively induce apoptosis in neuroblastoma xenografts [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 376.

Abstract 1729: Novel liposomal topotecan formulation has a lower IC50 than the free form on neuroblastoma cells

Introduction: Neuroblastomas (NB) are the most common solid tumor in children and infants, and are frequently resistant to all standard therapies. Patients are accordingly vulnerable to acute and long-term systemic effects of toxic chemotherapy. These drugs target rapidly dividing cells throughout the body, leading to severe side effects. One strategy to reduce off-target toxicities is to selectively increase drug uptake in the tumor. In pilot studies, we found that microbubbles containing liposomal doxorubicin, an agent that is effective against NB, and focused ultrasound (sonoporation) increased doxorubicin uptake in NB xenografts. However, NB is typically treated with multidrug chemotherapy, raising the importance of testing additional agents. In these studies, we evaluated a novel liposomal formulation of topotecan, an agent used in NB treatment which is both effective and associated with significant systemic toxicities. In vitro studies are needed to determine the IC50 (concentration of the drug needed to reduce the number of live cells by half). A required esterase cleavage at the delivery site can inhibit liposome encapsulated drug release. Therefore, we hypothesized that liposomal topotecan (2T-T) would have a higher IC50 than free topotecan.

Methods: We tested the effect of 2T-T on nine different NB cell lines:LA1-55n, LA-1-5S, LAN-5, NGP, SK-N-AS, BE2, SHEP, NBL-WN, and SH-SY5Y;five N-type (invasive), three S-type (noninvasive), seven MYCN-amplified (poor prognosis). We have tested free topotecan in 3 of these (LA-1-5S, NBL-WN, SH-SY5Y). Cells were plated in full RPMI at 80% confluence. 2T-T or topotecan (0 to 50 uM) were added to cells 24 hours later for 72 hours. Viable cells were estimated using a WST cell counting kit. 50uM empty liposomes and lysis buffer were used as controls. Experiments were performed in triplicate, with p≥0.05deemed significant (student t-test or ratio-paired t-test using PRISM).

Results: 2T-T had a mean IC50 of 0.37±0.58uM(mean R2=0.9±0.07).Empty liposomes caused no cytotoxicity in any cell line. We found no difference in IC50 according to S or N type (0.50±0.65vs 0.35±0.58(p=ns)). The mean IC50 of MYCN-amplified cells was 0.47±0.63,while that of non-MYCN-amplified was 0.031±0.029(n=2), suggesting no difference in cytotoxicity based on MYCN status. 2T-T had a 2 fold lower IC50 than free topotecan (1.14±1.19vs 0.48±0.82,p=0.046), suggesting liposomes did not inhibit topotecan release.

Conclusion: These findings suggest that liposomal topotecan (T2-T) has a lower IC50 than free topotecan in NB, and that MYCN amplification and phenotype do not modify 2T-T cytotoxicity. Our results suggest that liposomal encapsulation does not inhibit topotecan release, but could increase its cytotoxicity by increasing topotecan half-life. We predict that, in vivo 2T-T could reduce toxicities and side effects, warranting the investigation of 2T-T sonoporation in NB xenografts.

Citation Format: Paula Viza Gomes, Stephanie Shen, Meghan Hill, Kilkee Flynn, Mendi Marquez, Liliya Frolova, Jessica J. Kandel, Michaelann Tartis, Sonia L. Hernandez. Novel liposomal topotecan formulation has a lower IC50 than the free form on neuroblastoma cells [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1729.

Perfusion-guided sonopermeation of neuroblastoma: a novel strategy for monitoring and predicting liposomal doxorubicin uptake in vivo

Neuroblastoma (NB) is the most common extracranial solid tumor in infants and children, and imposes significant morbidity and mortality in this population. The aggressive chemoradiotherapy required to treat high-risk NB results in survival of less than 50%, yet is associated with significant long-term adverse effects in survivors. Boosting efficacy and reducing morbidity are therefore key goals of treatment for affected children. We hypothesize that these may be achieved by developing strategies that both focus and limit toxic therapies to the region of the tumor. One such strategy is the use of targeted image-guided drug delivery (IGDD), which is growing in popularity in personalized therapy to simultaneously improve on-target drug deposition and assess drug pharmacodynamics in individual patients. IGDD strategies can utilize a variety of imaging modalities and methods of actively targeting pharmaceutical drugs, however in vivo imaging in combination with focused ultrasound is one of the most promising approaches already being deployed for clinical applications. Over the last two decades, IGDD using focused ultrasound with "microbubble" ultrasound contrast agents (UCAs) has been increasingly explored as a method of targeting a wide variety of diseases, including cancer. This technique, known as sonopermeation, mechanically augments vascular permeability, enabling increased penetration of drugs into target tissue. However, to date, methods of monitoring the vascular bioeffects of sonopermeation in vivo are lacking. UCAs are excellent vascular probes in contrast-enhanced ultrasound (CEUS) imaging, and are thus uniquely suited for monitoring the effects of sonopermeation in tumors. Methods: To monitor the therapeutic efficacy of sonopermeation in vivo, we developed a novel system using 2D and 3D quantitative contrast-enhanced ultrasound imaging (qCEUS). 3D tumor volume and contrast enhancement was used to evaluate changes in blood volume during sonopermeation. 2D qCEUS-derived time-intensity curves (TICs) were used to assess reperfusion rates following sonopermeation therapy. Intratumoral doxorubicin (and liposome) uptake in NB was evalauted ex vivo along with associated vascular changes. Results: In this study, we demonstrate that combining focused ultrasound therapy with UCAs can significantly enhance chemotherapeutic payload to NB in an orthotopic xenograft model, by improving delivery and tumoral uptake of long-circulating liposomal doxorubicin (L-DOX) nanoparticles. qCEUS imaging suggests that changes in flow rates are highly sensitive to sonopermeation and could be used to monitor the efficacy of treatment in vivo. Additionally, initial tumor perfusion may be a good predictor of drug uptake during sonopermeation. Following sonopermeation treatment, vascular biomarkers show increased permeability due to reduced pericyte coverage and rapid onset of doxorubicin-induced apoptosis of NB cells but without damage to blood vessels. Conclusion: Our results suggest that significant L-DOX uptake can occur by increasing tumor vascular permeability with microbubble sonopermeation without otherwise damaging the vasculature, as confirmed by in vivo qCEUS imaging and ex vivo analysis. The use of qCEUS imaging to monitor sonopermeation efficiency and predict drug uptake could potentially provide real-time feedback to clinicians for determining treatment efficacy in tumors, leading to better and more efficient personalized therapies. Finally, we demonstrate how the IGDD strategy outlined in this study could be implemented in human patients using a single case study.

Pediatric Modification of the Medically Necessary, Time-Sensitive Scoring System for Operating Room Procedure Prioritization During the COVID-19 Pandemic

BACKGROUND

The COVID-19 pandemic forced surgeons to reconsider concepts of "elective" operations. Perceptions about the time sensitivity and medical necessity of a procedure have taken on greater significance during the pandemic. The evolving ethical and clinical environment requires reappraisal of perioperative factors, such as personal protective equipment conservation; limiting the risk of exposure to COVID-19 for patients, families, and healthcare workers; preservation of hospital beds and ICU resources; and minimizing COVID-19-related perioperative risk to patients.

STUDY DESIGN

A scaffold for the complex decision-making required for prioritization of medically necessary, time-sensitive (MeNTS) operations was developed for adult patients by colleagues at the University of Chicago. Although adult MeNTS scoring can be applied across adult surgical specialties, some variables were irrelevant in a pediatric population. Pediatric manifestations of chronic diseases and congenital anomalies were not accounted for. To account for the unique challenges children face, we modified the adult MeNTS system for use across pediatric subspecialties.

RESULTS

This pediatric MeNTS scoring system was applied to 101 cases both performed and deferred between March 23 and April 19, 2020 at the University of Chicago Comer Children's Hospital. The pediatric MeNTS scores provide a safe, equitable, transparent, and ethical strategy to prioritize children's surgical procedures.

CONCLUSIONS

This process is adaptable to individual institutions and we project it will be useful during the acute phase of the pandemic (maximal limitations), as well as the anticipated recovery phase.

Evaluation of a water-soluble contrast protocol for nonoperative management of pediatric adhesive small bowel obstruction

BACKGROUND/PURPOSE

We examined outcomes before and after implementing an enteral water-soluble contrast protocol for management of pediatric adhesive small bowel obstruction (ASBO).

METHODS

Medical records were reviewed retrospectively for all children admitted with ASBO between November 2010 and June 2017. Those admitted between November 2010 and October 2013 received nasogastric decompression with decision for surgery determined by surgeon judgment (preprotocol). Patients admitted after October 2013 (postprotocol) received water-soluble contrast early after admission, were monitored with serial examinations and radiographs, and underwent surgery if contrast was not visualized in the cecum by 24 h. Group outcomes were compared.

RESULTS

Twenty-six patients experienced 29 admissions preprotocol, and 11 patients experienced 12 admissions postprotocol. Thirteen (45%) patients admitted preprotocol underwent surgery, versus 2 (17%) postprotocol patients (p = 0.04). Contrast study diagnostic sensitivity as a predictor for ASBO resolution was 100%, with 90% specificity. Median overall hospital LOS trended shorter in the postprotocol group, though was not statistically significant (6.2 days (preprotocol) vs 3.6 days (postprotocol) p = 0.12). Pre- vs. postprotocol net operating cost per admission yielded a savings of $8885.42.

CONCLUSIONS

Administration of water-soluble contrast after hospitalization for pediatric ASBO may play a dual diagnostic and therapeutic role in management with decreases in surgical intervention, LOS, and cost.

TYPE OF STUDY

Retrospective comparative study.

LEVEL OF EVIDENCE

Level III.

Lack of evidence for tissue hypoxia as a contributing factor in anastomotic leak following colon anastomosis and segmental devascularization in rats

PURPOSE

Current surgical dogma dictates that tissue ischemia and hypoxia are major contributing factors in anastomotic leak despite scant evidence. The aim of this study was to determine if tissue hypoxia is a feature of anastomotic leakage in rats following colon resection and segmental devascularization.

METHODS

Rats were randomly assigned to undergo sham operation, segmental colon devascularization alone, colectomy alone, or segmental devascularization plus colectomy. Tissue hypoxia present at the colon anastomosis site across the various treatment groups was determined at sacrifice on postoperative day 6. Pimonidazole HCl was injected 30 min prior to sacrifice. Anastomotic tissues were examined and scored for healing versus leakage using an anastomotic healing score (AHS). Collagen content, hypoxia, enteric smooth muscle and periendothelial stromal patterning, and apoptosis were evaluated histologically.

RESULTS

No differences in tissue hypoxia were noted in the 16% of anastomotic tissues with poor healing compared to the remaining 84% of rats whose anastomoses healed well. No significant changes were found in cell death in the submucosa of any group. Consistent with previous findings, poor healing was associated with lower collagen content. Submucosal thickness correlated with increased arteriole diameter (R ² = 0.25, p < 0.005).

CONCLUSIONS

These results demonstrate that tissue hypoxia is not a distinctive feature of anastomotic tissues that fail to heal and leak, even when their blood supply is interrupted. These findings suggest that compensatory factors may mitigate the effects of ischemia and hypoxia during healing of anastomotic tissues and that the process of leakage involves factors beyond their acute effects.

Pediatric lymphatic malformations: evolving understanding and therapeutic options

Multimodal treatment of lymphatic malformations continues to expand as new information about the biology and genetics of these lesions is discovered, along with knowledge gained from clinical practice. A patient-centered approach, ideally provided by a multidisciplinary medical and surgical team, should guide timing and modality of treatment. Current treatment options include observation, surgery, sclerotherapy, radiofrequency ablation, and laser therapy. New medical and surgical therapies are emerging, and include sildenafil, propranolol, sirolimus, and vascularized lymph node transfer. The primary focus of management is to support and optimize these patients' quality of life. Researchers continue to study lymphatic malformations with the goal of increasing therapeutic options and developing effective clinical pathways for these complicated lesions.

Quality and extent of locum tenens coverage in pediatric surgical practices

The prevalence and quality of locum tenens coverage in pediatric surgery have not been determined. An Internet-based survey of American Pediatric Surgical Association members was conducted: 1) practice description; 2) use and frequency of locum tenens coverage; 4) whether the surgeon provided such coverage; and 5) Likert scale responses (strongly disagree, disagree, neutral, agree, strongly agree) to statements addressing its acceptability and quality (two × five contingency table and χ(2) analyses, significance at P < 0.05). Three hundred sixteen of 1163 members (27.2% response rate) responded. One-fourth (24.1%) used a locum tenens regularly. Reasons were long-term inability to recruit a full-time surgeon (35.2%) and short-term vacancies (32.4%). One-fifth (20.4%) did locum tenens work; one-fourth (27.0%) plan to do so in the future. Two-thirds (64.2%) believe that surgical care in a locum tenens situation does not provide the same level of care as a full-time community-based surgeon. Most support locum tenens for short-term coverage (87.3%) and recruitment problems (72.1%), but not long-term vacancies (38.8%; P < 0.001) or permanent coverage (27.0%; P < 0.001). locum tenens coverage is an established feature of pediatric surgery. Most view it as a stopgap solution to the surgical workforce shortage.

Quality and Extent of Locum Tenens Coverage in Pediatric Surgical Practices

The prevalence and quality of locum tenens coverage in pediatric surgery have not been determined. An Internet-based survey of American Pediatric Surgical Association members was conducted: 1) practice description; 2) use and frequency of locum tenens coverage; 4) whether the surgeon provided such coverage; and 5) Likert scale responses (strongly disagree, disagree, neutral, agree, strongly agree) to statements addressing its acceptability and quality (two x five contingency table and χ2 analyses, significance at P < 0.05). Three hundred sixteen of 1163 members (27.2% response rate) responded. One-fourth (24.1%) used a locum tenens regularly. Reasons were long-term inability to recruit a full-time surgeon (35.2%) and short-term vacancies (32.4%). One-fifth (20.4%) did locum tenens work; one-fourth (27.0%) plan to do so in the future. Two-thirds (64.2%) believe that surgical care in a locum tenens situation does not provide the same level of care as a full-time community-based surgeon. Most support locum tenens for short-term coverage (87.3%) and recruitment problems (72.1%), but not long-term vacancies (38.8%; P < 0.001) or permanent coverage (27.0%; P < 0.001). Locum tenens coverage is an established feature of pediatric surgery. Most view it as a stopgap solution to the surgical workforce shortage.

Notch suppresses angiogenesis and progression of hepatic metastases

The Notch pathway plays multiple key roles in tumorigenesis, and its signaling components have therefore aroused great interest as targets for emerging therapies. Here, we show that inhibition of Notch, using a soluble receptor Notch1 decoy, unexpectedly caused a remarkable increase in liver metastases from neuroblastoma and breast cancer cells. Increased liver metastases were also seen after treatment with the γ-secretase inhibitor PF-03084014. Transgenic mice with heterozygous loss of Notch1 demonstrated a marked increase in hepatic metastases, indicating that Notch1 signaling acts as metastatic suppressor in the liver microenvironment. Inhibition of DLL1/4 with ligand-specific Notch1 decoys increased sprouting of sinusoidal endothelial cells into micrometastases, thereby supporting early metastatic angiogenic growth. Inhibition of tumor-derived JAG1 signaling activated hepatic stellate cells, increasing their recruitment to vasculature of micrometastases, thereby supporting progression to macrometastases. These results demonstrate that inhibition of Notch causes pathologic activation of liver stromal cells, promoting angiogenesis and growth of hepatic metastases. Our findings have potentially serious implications for Notch inhibition therapy.

Aberrant lymphatic endothelial progenitors in lymphatic malformation development

Lymphatic malformations (LMs) are vascular anomalies thought to arise from dysregulated lymphangiogenesis. These lesions impose a significant burden of disease on affected individuals. LM pathobiology is poorly understood, hindering the development of effective treatments. In the present studies, immunostaining of LM tissues revealed that endothelial cells lining aberrant lymphatic vessels and cells in the surrounding stroma expressed the stem cell marker, CD133, and the lymphatic endothelial protein, podoplanin. Isolated patient-derived CD133+ LM cells expressed stem cell genes (NANOG, Oct4), circulating endothelial cell precursor proteins (CD90, CD146, c-Kit, VEGFR-2), and lymphatic endothelial proteins (podoplanin, VEGFR-3). Consistent with a progenitor cell identity, CD133+ LM cells were multipotent and could be differentiated into fat, bone, smooth muscle, and lymphatic endothelial cells in vitro. CD133+ cells were compared to CD133− cells isolated from LM fluids. CD133− LM cells had lower expression of stem cell genes, but expressed circulating endothelial precursor proteins and high levels of lymphatic endothelial proteins, VE-cadherin, CD31, podoplanin, VEGFR-3 and Prox1. CD133− LM cells were not multipotent, consistent with a differentiated lymphatic endothelial cell phenotype. In a mouse xenograft model, CD133+ LM cells differentiated into lymphatic endothelial cells that formed irregularly dilated lymphatic channels, phenocopying human LMs. In vivo, CD133+ LM cells acquired expression of differentiated lymphatic endothelial cell proteins, podoplanin, LYVE1, Prox1, and VEGFR-3, comparable to expression found in LM patient tissues. Taken together, these data identify a novel LM progenitor cell population that differentiates to form the abnormal lymphatic structures characteristic of these lesions, recapitulating the human LM phenotype. This LM progenitor cell population may contribute to the clinically refractory behavior of LMs.

Clinical spectrum of capillary malformation-arteriovenous malformation syndrome presenting to a pediatric dermatology practice: a retrospective study

Capillary malformation-arteriovenous malformation syndrome (CM-AVM) is an autosomal dominant disorder caused by RASA1 mutations. The prevalence and phenotypic spectrum are unknown. Evaluation of patients with multiple CMs is challenging because associated AVMs can be life threatening. The objective of this study was to describe the clinical characteristics of children presenting with features of CM-AVM to an academic pediatric dermatology practice. After institutional review board approval was received, a retrospective chart review was performed of patients presenting between 2009 and 2012 with features of CM-AVM. We report nine cases. Presenting symptoms ranged from extensive vascular stains and cardiac failure to CMs noted incidentally during routine skin examination. All demonstrated multiple CMs, two had Parkes Weber syndrome, and two had multiple infantile hemangiomas. Seven patients had family histories of multiple CMs; three had family histories of large, atypical CMs. Six had personal or family histories of AVMs. Genetic evaluation was recommended for all and was pursued by six families; four RASA1 mutations were identified, including one de novo. Consultations with neurology, cardiology, and orthopedics were recommended. Most patients (89%) have not required treatment to date. CM-AVM is an underrecognized condition with a wide clinical spectrum that often presents in childhood. Further evaluation may be indicated in patients with multiple CMs. This study is limited by its small and retrospective nature.

Serendipity: translational research, high quality care, and the children's hospital. Jay and Margie Grosfeld Lecture

The word "serendipity" was coined by Horace Walpole, Earl of Orford, in a letter he wrote in January 1754. He defined serendipity as the making of "….discoveries, by accidents and sagacity, of things which [you] were not in quest of….you must observe that no discovery of a thing you are looking for comes under this description." I would like to make the case that a children's hospital can be a superb setting in which to attempt this feat-to generate Serendipity. I would also like to convince you that this attribute is absolutely essential to providing the very best care for children.

Congenital cutaneous hemangioma causing cardiac failure: a case report and review of the literature

We present a case of a large congenital hemangioma (CH) on the neck causing cardiac failure and thrombocytopenia in a female neonate. A trial of medical therapy with corticosteroids and propranolol was attempted, but the patient ultimately underwent definitive treatment with embolization and surgical resection with a positive outcome. A review of the English language literature revealed 16 previously reported cases of CHs complicated by congestive heart failure. This series supports known demographic features of CHs, including a lack of gender discrepancy and a predilection to affect the head and neck. These CHs are rarely diagnosed in utero; most patients present with a mass at birth. Cardiac failure is identified prenatally or in the first days of life. A mild to moderate thrombocytopenia and coagulopathy, which is likely transient and distinct from classic Kasabach-Merritt phenomenon, accompanies many of these cases. There is a 30% associated mortality rate. Both medical and interventional treatment modalities have been reported. Steroids are the most commonly used medication, but without any clear benefit. We hypothesize that, based on its possible mechanisms of action,propranolol may be a more effective treatment for CHs requiring treatment. As surgical intervention may be necessary, we recommend a multidisciplinary approach to treating patients with problematic CHs.

Notch and VEGF pathways play distinct but complementary roles in tumor angiogenesis

BACKGROUND

Anti-angiogenesis is a validated strategy to treat cancer, with efficacy in controlling both primary tumor growth and metastasis. The role of the Notch family of proteins in tumor angiogenesis is still emerging, but recent data suggest that Notch signaling may function in the physiologic response to loss of VEGF signaling, and thus participate in tumor adaptation to VEGF inhibitors.

METHODS

We asked whether combining Notch and VEGF blockade would enhance suppression of tumor angiogenesis and growth, using the NGP neuroblastoma model. NGP tumors were engineered to express a Notch1 decoy construct, which restricts Notch signaling, and then treated with either the anti-VEGF antibody bevacizumab or vehicle.

RESULTS

Combining Notch and VEGF blockade led to blood vessel regression, increasing endothelial cell apoptosis and disrupting pericyte coverage of endothelial cells. Combined Notch and VEGF blockade did not affect tumor weight, but did additively reduce tumor viability.

CONCLUSIONS

Our results indicate that Notch and VEGF pathways play distinct but complementary roles in tumor angiogenesis, and show that concurrent blockade disrupts primary tumor vasculature and viability further than inhibition of either pathway alone.

Abstract 2809: Deficiency of Notch-1 signaling in liver increases neuroblastoma hepatic metastases

Purpose: The Notch signaling pathway has been extensively studied for its role in tumor angiogenesis but its function in tumor metastasis is largely elusive. In the present study we investigated the role of a notch receptor, Notch-1, in the regulation of neuroblastoma liver metastatic process.

Methods: To investigate the function of Notch-1 in neuroblastoma liver metastasis we first generated immunodeficient (rag2gammaC deletion) Notch-1 heterozygous (+/-) mice. We crossed a Notch1 heterozygous (+/-) mouse with a rag2/gamma-c double knockout (-/-) mouse. The mouse with Notch1(+/-)rag2(+/-)gammaC(+/-) genotype was then backcrossed with a rag2gammaC double knockout (-/-) mouse to generate rag2(-/-)gammaC(-/-)Notch1(+/-) mouse or rag2(-/-)gammaC(-/-)Notch1(+/+)control mouse . These mice (n=5) were intracardically injected with 105 neuroblastoma NGP (MYCN amplified) cells expressing Firefly luciferase. The mice were subjected to IVIS- bioluminescence imaging, once in a week, to monitor the metastatic spread. All mice were sacrificed at week 8. At the time of sacrifice, mice were injected with Luciferin, sacrificed and liver was then dissected out, imaged and bioluminescence flux was measured (ex vivo imaging). The liver tissues were also sectioned (5um, paraffin) and H&E stained at multiple levels to further confirm the presence of metastases.

Result: Intracardically injected NGP cells formed increased liver metastases in rag2(-/-)gammaC(-/-)Notch1(+/-) mice compared to littermate control rag2(-/-)gammaC(-/-)Notch1(+/+) mice. 4 out of 5 (80%) mice in Notch-het group and only 1 out of 5 (20%) mice in control group developed hepatic metastases. Notch-het livers showed multiple metastatic lesions with diameter ranged from 1-5 mm. Ex vivo bioluminescence imaging showed total flux (photon/sec) of Notch1 (+/-) livers were significantly higher (p&lt;0.01) compared to Notch1 (+/+) control livers. Immunohistochemical staining against blood vessel markers such as Collagen IV, endomucin (endothelial cells) and aSMA (pericyte) showed extensive network of angiogenesis in Notch1 (+/-) liver metastases.

Conclusion: Deficiency of Notch1 signaling in liver microenvironment presented an increase in metastases in Notch-het mice in NGP intracardiac injection metastatic model. Therefore our study indicates that Notch1 acts as tumor suppressor in neuroblastoma liver metastasis.

Citation Format: Debarshi Banerjee, Alejandro Garcia, John Andrews, Emily Sbiroli, Jessica J. Kandel, Darrel J. Yamashiro. Deficiency of Notch-1 signaling in liver increases neuroblastoma hepatic metastases. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2809. doi:10.1158/1538-7445.AM2013-2809

Correlation of tumor-associated macrophages and clinicopathological factors in Wilms tumor

Background/purpose

Despite high long-term survival rates in patients with Wilms tumor, there is a need to develop better prognostic biomarkers in order to maximize cure while avoiding treatment-associated morbidities. Tumor-associated macrophages have been recently associated with poorer prognosis and increased disease progression in a number of adult cancers. We investigated the relationship between macrophages and clinicopathological fators in this pediatric solid tumor.

Methods

Tissue microarray sections of 124 Wilms tumor cases obtained from the Cooperative Human Tissue Network were stained with CD68, a macrophage marker using standard immunohistochemical techniques and quantified using digital image processing techniques. Macrophage densities were correlated by tumor stage, and survival analyses were conducted with available clinical data. Immunohistochemistry was performed on 25 additional Wilms tumor cases obtained from the tumor bank at Columbia University Medical Center and correlated with presence of tumor microvascular invasion.

Results

Mean macrophage count densities in stage IV tumors were significantly greater than densities in stage I and III tumors (p=.021, .036). Although the overall and disease-free survival did not differ between high and low macrophage presence groups across all stages, increased macrophage presence was associated with decreased disease-free survival in patients with stage II tumors (p=0.035). Increased macrophage presence may have also correlated with decreased disease-free survival in stage IV patients, but the sample size was too small to allow detection of this difference with significance (p=0.575). Increased macrophage presence was associated with tumor microvascular invasion (p=0.0004).

Conclusion

Our results suggest that macrophage recruitment may be associated with disease progression in Wilms tumor. Quantitation of macrophage presence may therefore be a useful adjunct in refining staging algorithms for patients with stage II Wilms tumor. Such data might be useful in the effort to reduce the risk of adverse effects associated with under- or overtreatment of this neoplasm.

Severe Mycoplasma pneumoniae infection requiring extracorporeal membrane oxygenation with concomitant ischemic stroke in a child

Mycoplasma pneumoniae is one of the most common agents causing respiratory disease in children. The most common extra-pulmonary manifestations of M. pneumoniae include central nervous system involvement, with stroke being an uncommon but devastating consequence. We present a 13-year-old girl with severe respiratory disease requiring extracorporeal membrane oxygenation, who developed ischemic stroke associated with clinical and serologic evidence of M. pneumoniae. A case of M. pneumoniae causing this degree of respiratory failure associated with stroke has not been previously reported. Prompt recognition of severe mycoplasmal infection may allow for earlier treatment and concomitant evaluation of neurologic injury.

Primary nephrectomy and intraoperative tumor spill: report from the Children's Oncology Group (COG) renal tumors committee

PURPOSE

Initial Children's Oncology Group (COG) management for Wilms' tumor (WT) consists of primary nephroureterectomy with lymph node sampling. While this provides accurate staging to define further treatment, it may result in intraoperative spill (IOS), which is associated with higher recurrence rates and therefore requires more intensive therapy. The purpose of this study is to determine current rates and identify factors which may predispose a patient to IOS.

METHODS

The study population was drawn from the AREN03B2 renal tumor banking and classification study of the Children's Oncology Group. All children with a first time occurrence of a renal mass were eligible for the study. At the time of enrollment and prior to risk stratification, the institution is required to submit operative notes, pathology specimens, a chest computed tomography scan (CT), and a contrast-enhanced CT or magnetic resonance imaging (MRI) of the abdomen and pelvis for central imaging review. These data are then used to determine an initial risk classification and therapeutic protocol eligibility. Patients who had a unilateral nephroureterectomy for favorable histology WT underwent further review to assure data accuracy and to clarify details regarding the spill. Analyses were performed using chi square and logistic regression. Odd ratios (OR) are shown with 95% confidence intervals.

RESULTS

There were 1,131 primary nephrectomies for unilateral WT with an IOS rate of 9.7% with an additional 1.8% having possible tumor spill during renal vein or IVC tumor thrombectomy. IOS correlated with diameter (>12 cm, p<0.0001) and laterality (right, p=0.0414). Simple logistic regression indicated that IOS increased 2.7% [p=0.0240, OR 1.027 (1.004, 1.052)] with each 1 cm increase in diameter (3 - 21 cm) and 4.7% [p=0.0147 OR 1.047 (1.009, 1.086)] with each 100 g increase in weight (80 - 1800 g). Multiple logistic regression indicated that laterality [right p=0.048, OR 1.46 (1.004, 2.110)] and weight (p=0.03, OR 1.039 (1.003, 1.075) were predictive of IOS when diameter was included as a continuous variable. Diameter as a binary variable was highly prognostic of IOS (p=0.0002), while laterality and weight were not significant.

CONCLUSIONS

Intraoperative tumor spill occurs in about one out of every ten cases of primary nephroureterectomies for WT. Right-sided and larger tumors are at higher risk of IOS.

CM-AVM syndrome in a neonate: case report and treatment with a novel flow reduction strategy

Mutations in the RASA-1 gene underlie several related disorders of vasculogenesis. Capillary malformation-arteriovenous malformation (CM-AVM) is one such entity and was recently encountered in a neonate who demonstrated its clinical and radiologic features. A single mutation in the RASA-1 gene was detected.A novel flow reduction strategy was employed to a large AVM affecting the patient's upper limb. The imaging findings, surgical procedure and patient's improved post-operative state are described.

Image-guided esophageal anastomosis in esophageal atresia

Infants with tracheoesophageal fistulas may present with complex cardiac disease that may obviate or disrupt a safe operative repair. Here we present a case of an infant who developed cardiac instability during esophageal atresia repair, precluding formal anastomosis after approximation of the distal and proximal esophageal segments. Postoperatively, anastomosis of the esophagus was achieved using an image-guided technique with subsequent dilation. This approach may provide an alternative approach for establishment of esophageal continuity in patients who are high-risk operative candidates.

Contrast ultrasound imaging for identification of early responder tumor models to anti-angiogenic therapy

Agents targeting vascular endothelial growth factor (VEGF) have been validated as cancer therapeutics, yet efficacy can differ widely between tumor types and individual patients. In addition, such agents are costly and can have significant toxicities. Rapid noninvasive determination of response could provide significant benefits. We tested if response to the anti-VEGF antibody bevacizumab (BV) could be detected using contrast-enhanced ultrasound imaging (CEUS). We used two xenograft model systems with previously well-characterized responses to VEGF inhibition, a responder (SK-NEP-1) and a non-responder (NGP), and examined perfusion-related parameters. CEUS demonstrated that BV treatment arrested the increase in blood volume in the SK-NEP-1 tumor group only. Molecular imaging of α(V)β(3) with targeted microbubbles was a more sensitive prognostic indicator of BV efficacy. CEUS using RGD-labeled microbubbles showed a robust decrease in α(V)β(3) vasculature following BV treatment in SK-NEP-1 tumors. Paralleling these findings, lectin perfusion assays detected a disproportionate pruning of smaller, branch vessels. Therefore, we conclude that the response to BV can be identified soon after initiation of treatment, often within 3 days, by use of CEUS molecular imaging techniques. The use of a noninvasive ultrasound approach may allow for earlier and more effective determination of efficacy of antiangiogenic therapy.

Notch: a key regulator of tumor angiogenesis and metastasis

The Notch signaling pathway is critical for many developmental processes including physiologic angiogenesis. Notch is also implicated in having a key role in tumor angiogenesis. Preclinical and clinical experience with anti-angiogenic strategies indicates that they may be limited by tumor resistance and recurrence, which has led to the search for alternative angiogenic treatment strategies. Significant progress has been made in shedding light on the complex mechanisms by which Notch signaling can influence tumor growth by disrupting vasculature in an array of tumor models (Ridgway et al., 2006). These results have led to the consideration of Notch as an attractive target to block tumor angiogenesis and inhibit growth. However, studies of inhibition of Notch signaling in different tumor models have uncovered similarly variable results, and some unexpected adverse effects. The ability of Notch to function in a context-dependent manner as a determinant of cell fate, a tumor suppressor, and an oncogene may partially explain the complexity in interpreted the role of Notch signaling inhibitors in preclinical tumor studies. In addition, Notch may also play an important role in metastasis via its direct effects on the vasculature and by modulation of epithelial-mesenchymal transition in tumor cells. Here we present a current understanding of Notch signaling in tumor angiogenesis, and discuss recent work on the role of Notch in tumor metastatic progression.

Abstract 2325: Increase in neuroblastoma metastasis after dual inhibition of VEGF and Notch

Purpose: Vascular endothelial growth factor (VEGF) inhibition is a validated cancer treatment. However, even in responsive tumors, acquired resistance is common. Notch proteins also function as key angiogenic effectors, and cross-regulate VEGF expression, raising the question of whether combined treatment would enhance tumor suppression. We hypothesized that dual VEGF/Notch blockade would inhibit tumor growth in experimental SY5Y neuroblastoma. Methods: SY5Y neuroblastoma cells were lentivirally transfected to express Notch1-decoy (N1D) or GFP (control). Proliferation was assessed in vitro under both hypoxia and normoxia using BrdU assays. To examine the effect of N1D on tumor growth, 10[6] cells were xenografted intrarenally in nude mice and treated with placebo or bevacizumab (BV) twice a week. Tumor progression was monitored by bioluminescence. Metastatic burden in target organs was quantified by bioluminescence and histology. Vascular disruption due to N1D and BV treatment was evaluated by immunostaining. IACUC approval was obtained for all experiments. Results: Expression of soluble N1D was confirmed by immunoblotting conditioned media. SY5Y+N1D cells proliferated more rapidly in hypoxia than control SY5Y+GFP cells (p&lt;0.01). In vivo, BV treatment alone significantly reduced tumor growth as compared to placebo (p=0.026). However, combined treatment (N1D + BV) did not further reduce SY5Y tumor growth as compared to BV treatment alone (p=0.684). Interestingly, dual-treated mice developed higher metastatic burdens in liver than mice treated with either agent alone or controls by bioluminescence (p=0.006). By histology, dual-treated mice displayed a higher incidence of liver metastasis (7/9 mice) vs. mice treated with BV only (3/10 mice). Immunostaining demonstrated disruption of tumor vessel architecture in BV- and N1D + BV-treated mice. Conclusion: Dual VEGF/Notch targeting of SY5Y tumors resulted in increased metastatic burden, without affecting primary tumor growth, as compared to either treatment alone. Recent data indicates that tumoral hypoperfusion can promote progression, potentially by selecting for biologically aggressive behaviors. Our results suggest that dual Notch/VEGF blockade causes an enhanced propensity to metastasize. These data warrant further preclinical investigation.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2325. doi:1538-7445.AM2012-2325

Monitoring early tumor response to drug therapy with diffuse optical tomography

Although anti-angiogenic agents have shown promise as cancer therapeutics, their efficacy varies between tumor types and individual patients. Providing patient-specific metrics through rapid noninvasive imaging can help tailor drug treatment by optimizing dosages, timing of drug cycles, and duration of therapy-thereby reducing toxicity and cost and improving patient outcome. Diffuse optical tomography (DOT) is a noninvasive three-dimensional imaging modality that has been shown to capture physiologic changes in tumors through visualization of oxygenated, deoxygenated, and total hemoglobin concentrations, using non-ionizing radiation with near-infrared light. We employed a small animal model to ascertain if tumor response to bevacizumab (BV), an anti-angiogenic agent that targets vascular endothelial growth factor (VEGF), could be detected at early time points using DOT. We detected a significant decrease in total hemoglobin levels as soon as one day after BV treatment in responder xenograft tumors (SK-NEP-1), but not in SK-NEP-1 control tumors or in non-responder control or BV-treated NGP tumors. These results are confirmed by magnetic resonance imaging T2 relaxometry and lectin perfusion studies. Noninvasive DOT imaging may allow for earlier and more effective control of anti-angiogenic therapy.

Human cancer cells express Slug-based epithelial-mesenchymal transition gene expression signature obtained in vivo

Background

The biological mechanisms underlying cancer cell motility and invasiveness remain unclear, although it has been hypothesized that they involve some type of epithelial-mesenchymal transition (EMT).

Methods

We used xenograft models of human cancer cells in immunocompromised mice, profiling the harvested tumors separately with species-specific probes and computationally analyzing the results.

Results

Here we show that human cancer cells express in vivo a precise multi-cancer invasion-associated gene expression signature that prominently includes many EMT markers, among them the transcription factor Slug, fibronectin, and α-SMA. We found that human, but not mouse, cells express the signature and Slug is the only upregulated EMT-inducing transcription factor. The signature is also present in samples from many publicly available cancer gene expression datasets, suggesting that it is produced by the cancer cells themselves in multiple cancer types, including nonepithelial cancers such as neuroblastoma. Furthermore, we found that the presence of the signature in human xenografted cells was associated with a downregulation of adipocyte markers in the mouse tissue adjacent to the invasive tumor, suggesting that the signature is triggered by contextual microenvironmental interactions when the cancer cells encounter adipocytes, as previously reported.

Conclusions

The known, precise and consistent gene composition of this cancer mesenchymal transition signature, particularly when combined with simultaneous analysis of the adjacent microenvironment, provides unique opportunities for shedding light on the underlying mechanisms of cancer invasiveness as well as identifying potential diagnostic markers and targets for metastasis-inhibiting therapeutics.

Inhibition of cyclo-oxygenase 2 reduces tumor metastasis and inflammatory signaling during blockade of vascular endothelial growth factor

Vascular endothelial growth factor (VEGF) blockade is an effective therapy for human cancer, yet virtually all neoplasms resume primary tumor growth or metastasize during therapy. Mechanisms of progression have been proposed to include genes that control vascular remodeling and are elicited by hypoperfusion, such as the inducible enzyme cyclooxygenase-2 (COX-2). We have previously shown that COX-2 inhibition by the celecoxib analog SC236 attenuates perivascular stromal cell recruitment and tumor growth. We therefore examined the effect of combined SC236 and VEGF blockade, using the metastasizing orthotopic SKNEP1 model of pediatric cancer. Combined treatment perturbed tumor vessel remodeling and macrophage recruitment, but did not further limit primary tumor growth as compared to VEGF blockade alone. However, combining SC236 and VEGF inhibition significantly reduced the incidence of lung metastasis, suggesting a distinct effect on prometastatic mechanisms. We found that SC236 limited tumor cell viability and migration in vitro, with effects enhanced by hypoxia, but did not change tumor proliferation or matrix metalloproteinase expression in vivo. Gene set expression analysis (GSEA) indicated that the addition of SC236 to VEGF inhibition significantly reduced expression of gene sets linked to macrophage mobilization. Perivascular recruitment of macrophages induced by VEGF blockade was disrupted in tumors treated with combined VEGF- and COX-2-inhibition. Collectively, these findings suggest that during VEGF blockade COX-2 may restrict metastasis by limiting both prometastatic behaviors in individual tumor cells and mobilization of macrophages to the tumor vasculature.

PDE-constrained multispectral imaging of tissue chromophores with the equation of radiative transfer

We introduce a transport-theory-based PDE-constrained multispectral model for direct imaging of the spatial distributions of chromophores concentrations in biological tissue. The method solves the forward problem (boundary radiance at each wavelength) and the inverse problem (spatial distribution of chromophores concentrations), in an all-at-once manner in the framework of a reduced Hessian sequential quadratic programming method. To illustrate the code's performance, we present numerical and experimental studies involving tumor bearing mice. It is shown that the PDE-constrained multispectral method accelerates the reconstruction process by up to 15 times compared to unconstrained reconstruction algorithms and provides more accurate results as compared to the so-called two-step approach to multi-wavelength imaging.

Abstract 1282: Notch and VEGF regulate tumor endothelial cell survival

Notch proteins function in the specification of endothelial cell (EC) identity during physiologic angiogenesis, in part through interaction with VEGF signaling. However, the role of Notch in tumor EC (TEC) survival and apoptosis is less well defined. In EC, Notch signaling regulates survival pathways such as AKT, and anti-apoptotic proteins such as Bcl-2, with feedback loops modulating the VEGF and Notch pathways. We therefore asked whether targeting the Notch pathway affects EC apoptosis in tumors, specifically by affecting EC dependence on VEGF, a key endothelial survival factor.

We used a Notch decoy (ND) construct composed of the extracellular domain of the Notch1 receptor, which we have reported blocks Notch activation by multiple ligands. Cultured NGP neuroblastoma cells were engineered to secrete ND construct (NGP-ND). 10[6] NGP-ND and NGP-Lacz cells were implanted intrarenally in nude mice, and treated with either placebo or the anti-VEGF antibody bevacizumab (BV). Tumors were harvested at 5 weeks.

We have previously reported that Notch blockade disrupts NGP xenograft blood vessels. Here, we show that combining BV and ND further destabilizes tumor angiogenesis and architecture. Both tumor hypoxia and tumor cell apoptosis (quantified by pimonidazole and TUNEL stain, respectively) increased two-fold (p&lt;0.05). Quantification of the EC marker PECAM-1 demonstrated a 25% reduction in the EC coverage in the presence of either BV or ND, while there was a 75% decrease in BV + ND tumors (p&lt;0.05 vs BV and ND alone). TEC death also increased in BV + ND tumors as measured by the number of triple-immunopositive PECAM-1/TUNEL/DAPI+ cells. Regressing vessels can leave empty “sleeves” of vascular basement membrane. Therefore, we quantified type IV collagen on serial sections. In contrast to the decrease in TEC, none of the treatments altered the type IV collagen deposition (p=ns), consistent with loss of pre-existing endothelial vessels.

In cultured human umbilical vein endothelial cells (HUVEC) incubated with conditioned media (CM) containing ND, cell death increased twofold as compared to HUVEC cultured with control CM (p&lt;0.0001). VEGF could rescue this effect, as addition of rhVEGF (20ng/ml) to the CM reduced the cell death of both control and ND cells by 40% as compared to HUVEC in control CM (p=0.01). This striking reduction of cell death in ND-treated EC in response to VEGF is consistent with the ability of Notch to repress transcription of VEGFR2. Thus, when Notch signaling is blocked, endothelial VEGFR2 expression is derepressed, allowing VEGF/VEGFR2 survival signaling to rescue apoptosis.

In conclusion, we show that blocking the VEGF and Notch pathways increases TEC death in an additive manner. These results strongly suggest that VEGF signals from tumor cells can partially compensate for the apoptotic effects of Notch blockade, and provide a rationale for combined targeting of VEGF and Notch as a therapeutic approach.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1282.

Vascular characterization of clear cell sarcoma of the kidney in a child: a case report and review

Clear cell sarcoma of the kidney (CCSK) is uncommon pediatric renal tumor and can present a significant therapeutic challenge in those patients whose tumors spread beyond the kidney. Thus, identifying potential novel targets for treatment may be clinically important. Clear cell sarcoma of the kidney is characterized by a unique vascular pattern, in which nests of tumor cells are separated by regularly-spaced, fine fibrovascular septa. This distinctive histopathology raises the possibility that understanding the factors which drive angiogenesis in CCSK tumors may suggest new therapeutic targets. Here, we describe a case of CCSK and present immunohistochemical studies of its vasculature.

Vascular endothelial growth factor blockade rapidly elicits alternative proangiogenic pathways in neuroblastoma

Most children with neuroblastoma presenting after infancy have metastatic, chemoresistant disease. Amplification of the MYCN proto-oncogene is a significant marker of these poor-prognosis neuroblastoma tumors. Recent studies suggest that MYCN may function in part by promoting angiogenesis via vascular endothelial growth factor (VEGF). VEGF blockade has been validated as a therapeutic strategy in adult cancers. In these studies, we asked whether inhibition of VEGF signaling via VEGFR2 blockade in established MYCN-amplified neuroblastoma xenografts would: 1) restrict tumor growth; 2) induce hypoxia; and 3) alter tumor vasculature. The MYCN-amplified neuroblastoma human cell line NGP was implanted intrarenally in athymic female mice. After 5 weeks, mice with established tumors were selected, a cohort euthanized to provide day 0 controls, and the rest assigned to receive biweekly injections of DC101 (anti-murine VEGFR2 antibody) or vehicle. DC101 treatment did not inhibit progressive tumor growth in established NGP xenografts. Although tumor vasculature was not significantly disrupted, a modest increase in tumor hypoxia was demonstrated by pimonidazole staining, and expression of a previously described hypoxia metagene was increased by gene set enrichment analysis (GSEA) in DC101-treated tumors. DC101 treatment elicited increased: 1) expression of VEGFR1 and its ligand placental growth factor; and 2) increased Notch activation in tumor vasculature concurrent with expression of the Notch ligand Jagged1. This result suggests that established MYCN-amplified neuroblastoma tumors are relatively VEGF-independent, and display the ability to rapidly up-regulate hypoxia-responsive alternative proangiogenic mechanisms that may stabilize vasculature when VEGF is deficient.

Angiopoietin-1/Tie-2 activation contributes to vascular survival and tumor growth during VEGF blockade

Approval of the anti-vascular endothelial growth factor (VEGF) antibody bevacizumab by the FDA in 2004 reflected the success of this vascular targeting strategy in extending survival in patients with advanced cancers. However, consistent with previous reports that experimental tumors can grow or recur during VEGF blockade, it has become clear that many patients treated with VEGF inhibitors will ultimately develop progressive disease. Previous studies have shown that disruption of VEGF signaling in tumors induces remodeling in surviving vessels, and link increased expression of angiopoietin-1 (Ang-1) with this process. However, overexpression of Ang-1 in different tumors has yielded divergent results, restricting angiogenesis in some systems while promoting it in others. These data raise the possibility that effects of Ang-1/Tie-2 may be context-dependent. Expression of an Ang-1 construct (Ang1*) did not significantly change tumor growth in our model prior to treatment, although vessels exhibited changes consistent with increased Tie-2 signaling. During inhibition of VEGF, however, both overexpression of Ang1* and administration of an engineered Ang-1 agonist (Bow-Ang1) strikingly protected tumors and vasculature from regression. In this context, Ang-1/Tie-2 activation limited tumor hypoxia, increased vessel caliber, and promoted recruitment of mural cells. Thus, these studies support a model in which activation of Tie-2 is important for tumor and vessel survival when VEGF-dependent vasculature is stressed. Understanding such mechanisms of adaptation to this validated form of therapy may be important in designing regimens that make the best use of this approach.

A notch1 ectodomain construct inhibits endothelial notch signaling, tumor growth, and angiogenesis

Notch signaling is required for vascular development and tumor angiogenesis. Although inhibition of the Notch ligand Delta-like 4 can restrict tumor growth and disrupt neovasculature, the effect of inhibiting Notch receptor function on angiogenesis has yet to be defined. In this study, we generated a soluble form of the Notch1 receptor (Notch1 decoy) and assessed its effect on angiogenesis in vitro and in vivo. Notch1 decoy expression reduced signaling stimulated by the binding of three distinct Notch ligands to Notch1 and inhibited morphogenesis of endothelial cells overexpressing Notch4. Thus, Notch1 decoy functioned as an antagonist of ligand-dependent Notch signaling. In mice, Notch1 decoy also inhibited vascular endothelial growth factor-induced angiogenesis in skin, establishing a role for Notch receptor function in this process. We tested the effects of Notch1 decoy on tumor angiogenesis using two models: mouse mammary Mm5MT cells overexpressing fibroblast growth factor 4 (Mm5MT-FGF4) and NGP human neuroblastoma cells. Exogenously expressed FGF4 induced Notch ligand expression in Mm5MT cells and xenografts. Notch1 decoy expression did not affect tumorigenicity of Mm5MT-FGF4 cells in vitro but restricted Mm5MT-FGF4 xenograft growth in mice while markedly impairing neoangiogenesis. Similarly, Notch1 decoy expression did not affect NGP cells in vitro but disrupted vessels and decreased tumor viability in vivo. These results strongly suggest that Notch receptor signaling is required for tumor neoangiogenesis and provides a new target for tumor therapy.

Sustained VEGF blockade results in microenvironmental sequestration of VEGF by tumors and persistent VEGF receptor-2 activation

Vascular endothelial growth factor (VEGF) blockade has been validated clinically as a treatment for human cancers, yet virtually all patients eventually develop progressive disease during therapy. In order to dissect this phenomenon, we examined the effect of sustained VEGF blockade in a model of advanced pediatric cancer. Treatment of late-stage hepatoblastoma xenografts resulted in the initial collapse of the vasculature and significant tumor regression. However, during sustained treatment, vessels recovered, concurrent with a striking increase in tumor expression of perlecan, a heparan sulfate proteoglycan. Whereas VEGF mRNA was expressed at the periphery of surviving clusters of tumor cells, both secreted VEGF and perlecan accumulated circumferential to central vessels. Vascular expression of heparanase, VEGF receptor-2 ligand binding, and receptor activation were concurrently maintained despite circulating unbound VEGF Trap. Endothelial survival signaling via Akt persisted. These findings provide a novel mechanism for vascular survival during sustained VEGF blockade and indicate a role for extracellular matrix molecules that sequester and release biologically active VEGF.

Phase I Trial and Pharmacokinetic Study of Bevacizumab in Pediatric Patients With Refractory Solid Tumors: A Children's Oncology Group Study

Purpose

We conducted a pediatric phase I trial of the vascular endothelial growth factor (VEGF)–neutralizing antibody bevacizumab (BV). Primary aims included estimating the maximum-tolerated dose (MTD) and determining the dose-limiting toxicities (DLTs), pharmacokinetics, and biologic effects of BV in children with cancer.

Patients and Methods

BV (5, 10, 15 mg/kg) was administered intravenously every 2 weeks in 28-day courses to children with refractory solid tumors.

Results

Twenty-one patients enrolled, 20 (median age, 13 years) were eligible, and 18 completed one course and were fully assessable for toxicity. A total of 67 courses were administered (median, three courses per patient; range, one to 16 courses). Treatment was well tolerated with no DLTs observed. Non-DLTs included infusional reaction, rash, mucositis, proteinuria, and lymphopenia. Increases in systolic and diastolic blood pressure not meeting Common Terminology Criteria for Adverse Events (CTCAEv3) pediatric-specific criteria for hypertension were observed. There was no hemorrhage or thrombosis. Growth perturbation was not detected in a limited sample over the first course. The serum exposure to BV as measured by area under the concentration-time curve (AUC) seemed to increase in proportion to dose. The median clearance of BV was 4.1 mL/d/kg (range, 3.1 to 15.5 mL/d/kg), and the median half-life was 11.8 days (range, 4.4 to 14.6 days). No objective responses were observed. Exploratory analyses on circulating endothelial mobilization and viability are consistent with the available adult data.

Conclusion

BV is well tolerated in children. Phase II pediatric studies of BV in combination with chemotherapy in dosing schedules similar to adults are planned.

Ovarian repositioning in pediatric cancer patients: Flexible techniques accommodate pelvic radiation fields

Treatments for childhood cancer and consequent long-term survival rates continue to improve. As the success of these therapies advances, premature ovarian failure and sterility have become an increasingly evident long-term morbidity. Abdominal and pelvic radiation have been specifically shown to induce early menopause and decreased fertility. In order to minimize radiation injury, we utilized novel techniques to reposition ovaries in two girls with pelvic tumors prior to initiation of pelvic radiation. One girl with a sacral Ewing sarcoma underwent laparoscopic anterior suspension of the ovaries, using a simple and easily reversible technique. The second patient, who underwent hysterectomy for a recurrent uterine rhabdomyosarcoma, underwent widely lateral and cephalad repositioning of the ovaries. Both procedures were well tolerated, with no significant morbidity. In both cases the ovaries were moved well beyond the planned radiation field. We propose that open or laparoscopic ovarian repositioning in children is a simple, flexible, and reversible option to reduce radiation injury to the ovaries in pediatric cancer patients.

Inhibition of cyclooxygenase-2 disrupts tumor vascular mural cell recruitment and survival signaling

Much evidence supports an important role for the inducible enzyme cyclooxygenase-2 (COX-2) in tumor angiogenesis. Previous studies have focused on the role of COX-2 in stimulating endothelial proliferation, with blockade of this enzyme impairing endothelial homeostasis. However, recent data suggest that COX-2 also regulates molecules implicated in endothelial trafficking with pericytes/vascular mural cells (VMC), an interaction crucial to vessel stability. We investigated the role of COX-2 in vascular assembly by testing the effect of the specific COX-2 inhibitor SC-236 in an orthotopic xenograft model of human Wilms' tumor. Tumor growth was significantly suppressed by SC-236 (78% at day 28, 55% at day 35). Perfusion studies and immunostaining showed a marked decrease in vasculature, particularly in small vessels. Specifically, SC-236 inhibited participation of VMC in xenograft vessels. SC-236-treated tumors developed segmentally dilated, architecturally erratic tumor vessels with decreased nascent pericytes and scant mature VMC. Although vascular endothelial growth factor expression was unchanged, expression of the chemokine receptor CXCR4 was decreased in tumor vessels, consistent with defective homing of vascular progenitor cells. Vascular expression of phosphorylated platelet-derived growth factor receptor-beta was also diminished, indicating impaired VMC-endothelial trafficking. Consistent with the key role of this interaction in vessel homeostasis, vascular cells in SC-236-treated tumors displayed markedly diminished phosphorylated Akt, indicating disrupted survival signaling. These results show that SC-236 causes defective vascular assembly by attenuating incorporation of VMC into tumor vessels, impairing endothelial survival, and raise the possibility that blockade of COX-2 may provide therapeutic synergies with antiangiogenic molecules that more selectively target endothelial cells.

Preoperative angiography with embolization and radiofrequency ablation as novel adjuncts to safe surgical resection of a large, vascular sacrococcygeal teratoma

Sacrococcygeal teratomas (SCTs) can present a challenging problem and can be associated with significant perinatal morbidity and mortality. A female child was born at 36 weeks' gestation with a large, vascular Type 1 SCT originally identified by prenatal ultrasound. A CT scan showed two large feeding vessels arising from both internal iliac arteries that were successfully embolized during angiography. A radiofrequency probe was then used to ablate a zone between normal tissue and the tumor. The SCT was subsequently surgically excised with minimal blood loss. This case is presented to illustrate two useful and previously unreported postnatal adjuncts to the surgical treatment of massive, hypervascular sacrococcygeal tumors.

Vascular remodeling and clinical resistance to antiangiogenic cancer therapy

When first conceived, antiangiogenic therapy for cancer offered the possibility of universal efficacy, low toxicity, and little possibility of resistance. Blockade of the vascular endothelial growth factor (VEGF) pathway has yielded the most promising results both in animal models and in patients. However, resistance to VEGF blockade has been found even when given in combination with chemotherapy or other antiangiogenic agents. This resistance is associated with remodeled vasculature and with increased expression of angiogenic factors, such as PDGF-B and angiopoietin-1, which may contribute to vessel stabilization. Future efforts must be directed towards the identification of factors associated with vascular remodeling in order to improve the efficacy of antiangiogenic therapy.

Effects of potent VEGF blockade on experimental Wilms tumor and its persisting vasculature

We characterized the effect of potent vascular endothelial growth factor (VEGF) blockade on early-stage Wilms tumor xenograft growth, vasculature and metastasis. VEGF is a key mediator of both physiologic and tumor angiogenesis. We recently described that potent VEGF blockade induces regression of established Wilms tumor xenografts and vessels, also reducing the size but not the incidence of pre-existing metastases. In these studies, we examined the effects of potent VEGF blockade on earlier stages of experimental Wilms tumors, focusing on tumor growth, vasculature and metastasis. Athymic mice received intrarenal human Wilms tumor cell implants. Biweekly treatment with vehicle or the VEGF-Trap, a high-affinity soluble decoy receptor incorporating regions of VEGFR1 and VEGFR2, was begun 1 week later (100 or 500 micrograms/dose, n=20 in each group). Mice were euthanized at week 6 to examine tumor weight, incidence of lung metastases, vascularity and expression of angiogenic factors. A cohort of mice was examined 2 weeks after cessation of treatment. Compared to controls, VEGF-Trap treated tumors were significantly smaller (100 micrograms/dose: 92.7% smaller, p=0.0017; 500 micro g/dose: 99.0% smaller, p=0.0009). The incidence of lung metastasis also decreased significantly (p<0.0055). VEGF-Trap nearly eradicated tumor vasculature. Rare persisting vessels were characterized by large caliber, quiescence (lacking proliferation/apoptosis) and arterialization (both phenotypic and molecular). Potent VEGF blockade caused near-arrest of experimental Wilms tumor growth, resulted in nearly avascular tumors, and also decreased the incidence and size of metastases. Persistent vessels in tumors treated with VEGF-Trap displayed specific morphologic and molecular features, suggestive of arterialization. Future strategies that target these persisting vessels may enhance the efficacy of VEGF blockade therapy.