Development of Convolutional Neural Network to Segment Ultrasound Images of Histotripsy Ablation

OBJECTIVE

Histotripsy is a focused ultrasound therapy that ablates tissue via the action of bubble clouds. It is under investigation to treat a number of ailments, including renal tumors. Ultrasound imaging is used to monitor histotripsy, though there remains a lack of definitive imaging metrics to confirm successful treatment outcomes. In this study, a convolutional neural network (CNN) was developed to segment ablation on ultrasound images.

METHODS

A transfer learning approach was used to replace classification layers of the residual network ResNet-18. Inputs to the classification layers were based on ultrasound images of ablated red blood cell phantoms. Digital photographs served as the ground truth. The efficacy of the CNN was compared to subtraction imaging, and manual segmentation of images by two board-certified radiologists.

RESULTS

The CNN had a similar performance to manual segmentation, though was improved relative to segmentation with subtraction imaging. Predictions of the network improved over the course of treatment, with the Dice similarity coefficient less than 20% for fewer than 500 applied pulses, but 85% for more than 750 applied pulses. The network was also applied to ultrasound images of ex vivo kidney exposed to histotripsy, which indicated a morphological shift in the treatment profile relative to the phantoms. These findings were consistent with histology that confirmed ablation of the targeted tissue.

CONCLUSION

Overall, the CNN showed promise as a rapid means to assess outcomes of histotripsy and automate treatment.

SIGNIFICANCE

Data collected in this study indicate integration of CNN image segmentation to gauge outcomes for histotripsy ablation holds promise for automating treatment procedures.

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.

Histotripsy Bubble Cloud Contrast With Chirp-Coded Excitation in Preclinical Models

Histotripsy is a focused ultrasound therapy for tissue ablation via the generation of bubble clouds. These effects can be achieved noninvasively, making sensitive and specific bubble imaging essential for histotripsy guidance. Plane-wave ultrasound imaging can track bubble clouds with an excellent temporal resolution, but there is a significant reduction in echoes when deep-seated organs are targeted. Chirp-coded excitation uses wideband, long-duration imaging pulses to increase signals at depth and promote nonlinear bubble oscillations. In this study, we evaluated histotripsy bubble contrast with chirp-coded excitation in scattering gel phantoms and a subcutaneous mouse tumor model. A range of imaging pulse durations were tested, and compared to a standard plane-wave pulse sequence. Received chirped signals were processed with matched filters to highlight components associated with either fundamental or subharmonic (bubble-specific) frequency bands. The contrast-to-tissue ratio (CTR) was improved in scattering media for subharmonic contrast relative to fundamental contrast (both chirped and standard imaging pulses) with the longest-duration chirped-pulse tested (7.4 [Formula: see text] pulse duration). The CTR was improved for subharmonic contrast relative to fundamental contrast (both chirped and standard imaging pulses) by 4.25 dB ± 1.36 dB in phantoms and 3.84 dB ± 6.42 dB in vivo. No systematic changes were observed in the bubble cloud size or dissolution rate between sequences, indicating image resolution was maintained with the long-duration imaging pulses. Overall, this study demonstrates the feasibility of specific histotripsy bubble cloud visualization with chirp-coded excitation.

Estimating the mechanical energy of histotripsy bubble clouds with high frame rate imaging

Mechanical ablation with the focused ultrasound therapy histotripsy relies on the generation and action of bubble clouds. Despite its critical role for ablation, quantitative metrics of bubble activity to gauge treatment outcomes are still lacking. Here, plane wave imaging was used to track the dissolution of bubble clouds following initiation with the histotripsy pulse. Information about the rate of change in pixel intensity was coupled with an analytic diffusion model to estimate bubble size. Accuracy of the hybrid measurement/model was assessed by comparing the predicted and measured dissolution time of the bubble cloud. Good agreement was found between predictions and measurements of bubble cloud dissolution times in agarose phantoms and murine subcutaneous SCC VII tumors. The analytic diffusion model was extended to compute the maximum bubble size as well as energy imparted to the tissue due to bubble expansion. Regions within tumors predicted to have undergone strong bubble expansion were collocated with ablation. Further, the dissolution time was found to correlate with acoustic emissions generated by the bubble cloud during histotripsy insonation. Overall, these results indicate a combination of modeling and high frame rate imaging may provide means to quantify mechanical energy imparted to the tissue due to bubble expansion for histotripsy.

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.

Retinol binding protein 3 is increased in the retina of patients with diabetes resistant to diabetic retinopathy

The Joslin Medalist Study characterized people affected with type 1 diabetes for 50 years or longer. More than 35% of these individuals exhibit no to mild diabetic retinopathy (DR), independent of glycemic control, suggesting the presence of endogenous protective factors against DR in a subpopulation of patients. Proteomic analysis of retina and vitreous identified retinol binding protein 3 (RBP3), a retinol transport protein secreted mainly by the photoreceptors, as elevated in Medalist patients protected from advanced DR. Mass spectrometry and protein expression analysis identified an inverse association between vitreous RBP3 concentration and DR severity. Intravitreal injection and photoreceptor-specific overexpression of RBP3 in rodents inhibited the detrimental effects of vascular endothelial growth factor (VEGF). Mechanistically, our results showed that recombinant RBP3 exerted the therapeutic effects by binding and inhibiting VEGF receptor tyrosine phosphorylation. In addition, by binding to glucose transporter 1 (GLUT1) and decreasing glucose uptake, RBP3 blocked the detrimental effects of hyperglycemia in inducing inflammatory cytokines in retinal endothelial and Müller cells. Elevated expression of photoreceptor-secreted RBP3 may have a role in protection against the progression of DR due to hyperglycemia by inhibiting glucose uptake via GLUT1 and decreasing the expression of inflammatory cytokines and VEGF.

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.

Abstract 2055: Staphylococcus aureus alpha toxin activates Notch in endothelial cells

Background. Staphylococcus aureus infection is one of the leading causes of morbidity in hospitalized patients in the United States. The secreted agent hemolysin alpha toxin (Hla) requires the receptor A Disintegrin And Metalloproteinase domain-containing protein 10 (ADAM10) to mediate its toxic effects; ADAM10 in turn activates the Notch pathway. Notch proteins function in developmental and pathological angiogenesis via the modulation of key pathways in endothelial (EC) and perivascular cells. Thus, we hypothesized that Hla would activate Notch in EC in vitro and in vivo.

Methods. Human umbilical vein endothelial cells (HUVEC) were treated with recombinant Hla (rHla), Hla-H35L (genetically inactivated Hla), 5mM EDTA (a known Notch activator), or HBSS, and probed with a Luciferase reporter regulated by a Notch promoter. Mice engineered to express yellow fluorescent protein (YFP) upon Notch activation received a non-lethal daily subcutaneous injection of rHla (0.025 µg/5µL) or vehicle (PBS) and their retinal endothelial YFP interrogated at p6. 6 week old male Notch reporter mice received a 1-4 × 107 50 µl subcutaneous inoculation of S. aureus strains USA300/LAC (WT), or its isogenic Δhla mutant lacking Hla, and their skin biopsies were analyzed by histology after 36 hours, 8 and 16 days. Notch activation in endothelial cells of human liver sections from patients whose blood cultures were positive or negative for S. aureus was evaluated by immunohistochemistry.

Results. Luciferase assays demonstrated that Hla (0.01 µg/mL) increased Notch activation by 1.75±0.5-fold as compared to HBSS controls (p<0.05) and EDTA (5.4±1.4-fold activation relative to HBSS, p<0.01), whereas Hla-H35L had no effect. Retinal EC in YFP Notch reporter mice revealed significantly greater YFP intensity in EC after Hla injection than controls in two independent litters. Subcutaneous infection of S. aureus in the Notch reporter mice revealed a significant upregulation of Notch activation in response to Hla 36 hours after infection, both in intensity and area (4.2X10-5 ±1.8X10-5 vs. 7.9X10-4 ±6X10-4 mean intensity relative to DAPI area, p=0.008, and 6.7x106

±3.1x106 vs. 7.7x10-5 ±6x105 YFP area/ DAPI area, p=0.002). Increased EC Notch activation in response to Hla was maintained 8 and 16 days after inoculation. IHC showed EC in human liver had higher Notch expression than controls.

In sum, our results demonstrate that the S. aureus toxin Hla can potently activate Notch in endothelial cells, an effect which could have effects in development and pathological angiogenesis such as cancer.

Citation Format: Sonia L. Hernandez, Mildred Nelson, Georgia Sampedro, Bianca Lec, Jared Emolo, Naina Bagrodia, Ann M. Defnet, Lydia Wu, Juliane Bubeck-Wardenburg, Jessica Kandel. Staphylococcus aureus alpha toxin activates Notch in endothelial cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2055.

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.

High-Dose, Single-Fraction Irradiation Rapidly Reduces Tumor Vasculature and Perfusion in a Xenograft Model of Neuroblastoma

PURPOSE

To characterize the effects of high-dose radiation therapy (HDRT) on neuroblastoma tumor vasculature, including the endothelial cell (EC)-pericyte interaction as a potential target for combined treatment with antiangiogenic agents.

METHODS AND MATERIALS

The vascular effects of radiation therapy were examined in a xenograft model of high-risk neuroblastoma. In vivo 3-dimensional contrast-enhanced ultrasonography (3D-CEUS) imaging and immunohistochemistry (IHC) were performed.

RESULTS

HDRT significantly reduced tumor blood volume 6 hours after irradiation compared with the lower doses used in conventionally fractionated radiation. There was a 63% decrease in tumor blood volume after 12-Gy radiation compared with a 24% decrease after 2 Gy. Analysis of tumor vasculature by lectin angiography showed a significant loss of small vessel ends at 6 hours. IHC revealed a significant loss of ECs at 6 and 72 hours after HDRT, with an accompanying loss of immature and mature pericytes at 72 hours.

CONCLUSIONS

HDRT affects tumor vasculature in a manner not observed at lower doses. The main observation was an early reduction in tumor perfusion resulting from a reduction of small vessel ends with a corresponding loss of endothelial cells and pericytes.

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.

Characterization of circulating and endothelial progenitor cells in patients with extreme-duration type 1 diabetes

OBJECTIVE

We characterized and correlated endothelial progenitor cells (EPCs) and circulating progenitor cells (CPCs) with lack of vascular complications in the Joslin Medalist Study in patients with type 1 diabetes for 50 years or longer.

RESEARCH DESIGN AND METHODS

EPC and CPC levels were ascertained by flow cytometry and compared among Medalists (n = 172) with or without diabetic retinopathy (DR; n = 84 of 162), neuropathy (n = 94 of 165), diabetic nephropathy (DN; n = 18 of 172), cardiovascular disease (CVD; n = 63 of 168), age-matched controls (n = 83), type 2 diabetic patients (n = 36), and younger type 1 diabetic patients (n = 31). Mitogens, inflammatory cytokines, and oxidative markers were measured in blood or urine. Migration of cultured peripheral blood mononuclear cells (PBMCs) from Medalists and age-matched controls were compared.

RESULTS

Medalists' EPC and CPC levels equaled those of their nondiabetic age-matched controls, were 10% higher than those in younger type 1 diabetic patients, and were 20% higher than those in age-matched type 2 diabetic patients. CPC levels were 15% higher in Medalists without CVD and nephropathy than in those affected, whereas EPC levels were significantly higher in those without peripheral vascular disease (PVD) than those with PVD. Stromal-derived factor 1 (SDF-1) levels were higher in Medalists with CVD, DN, and DR than in those not affected and their controls. IGF-I levels were lower in Medalists and correlated inversely with CPC levels. Additionally, cultured PBMCs from Medalists migrated more than those from nondiabetic controls.

CONCLUSIONS

Normal levels of EPC and CPC in the Medalists, unlike other groups with diabetes, especially those without CVD, support the idea that endogenous factors exist to neutralize the adverse effects of metabolic abnormalities of diabetes on vascular tissues.

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.

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.

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.

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.

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 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.

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.

Autogenic tooth transplantation: a report of ten cases

Modifications in the surgical procedure for transplantation of the unerupted mandibular third molar to the first molar socket are presented, and the clinical and radiographic data on ten cases with a 3-year follow-up are described. The proposed method of treatment makes it possible to stabilize the transplant without a splint by using a suture crossed over the occlusal surface of the tooth.

[Vital tooth autotransplantation]

Ten cases of dental transplants belonging to the authors' set of cases were selected and they proved to be successful according to the factors these authors' believe to be important. The operations were carried out on young patients by transplanting the not fully formed third molar to the place of the first molar, following the technique described in the text. The success of a vital dental autotransplant depends on some factors: the tooth to be transplanted should have completed the amelogenesis so that two thirds of its root and the floor of the pulp chamber are also formed; the receiving alveolus must be prepared before the giving area, thus reducing the time in which the third molar remains dislocated out of its alveolus and the lack of communication between the two surgical beds.