IRF5 suppresses metastasis through the regulation of tumor-derived extracellular vesicles and pre-metastatic niche formation.

Metastasis is driven by extensive cooperation between a tumor and its microenvironment, resulting in the adaptation of molecular mechanisms that evade the immune system and enable pre-metastatic niche (PMN) formation. Little is known of the tumor-intrinsic factors that regulate these mechanisms. Here we show that expression of the transcription factor interferon regulatory factor 5 (IRF5) in osteosarcoma (OS) and breast carcinoma (BC) clinically correlates with prolonged survival and decreased secretion of tumor-derived extracellular vesicles (t-dEVs). Conversely, loss of intra-tumoral IRF5 establishes a PMN that supports metastasis. Mechanistically, IRF5-positive tumor cells retain IRF5 transcripts within t-dEVs that contribute to altered composition, secretion, and trafficking of t-dEVs to sites of metastasis. Upon whole-body pre-conditioning with t-dEVs from IRF5-high or -low OS and BC cells, we found increased lung metastatic colonization that replicated findings from orthotopically implanted cancer cells. Collectively, our findings uncover a new role for IRF5 in cancer metastasis through its regulation of t-dEV programming of the PMN.

Rare and de novo variants in 827 congenital diaphragmatic hernia probands implicate LONP1 as candidate risk gene.

Congenital diaphragmatic hernia (CDH) is a severe congenital anomaly that is often accompanied by other anomalies. Although the role of genetics in the pathogenesis of CDH has been established, only a small number of disease-associated genes have been identified. To further investigate the genetics of CDH, we analyzed de novo coding variants in 827 proband-parent trios and confirmed an overall significant enrichment of damaging de novo variants, especially in constrained genes. We identified LONP1 (lon peptidase 1, mitochondrial) and ALYREF (Aly/REF export factor) as candidate CDH-associated genes on the basis of de novo variants at a false discovery rate below 0.05. We also performed ultra-rare variant association analyses in 748 affected individuals and 11,220 ancestry-matched population control individuals and identified LONP1 as a risk gene contributing to CDH through both de novo and ultra-rare inherited largely heterozygous variants clustered in the core of the domains and segregating with CDH in affected familial individuals. Approximately 3% of our CDH cohort who are heterozygous with ultra-rare predicted damaging variants in LONP1 have a range of clinical phenotypes, including other anomalies in some individuals and higher mortality and requirement for extracorporeal membrane oxygenation. Mice with lung epithelium-specific deletion of Lonp1 die immediately after birth, most likely because of the observed severe reduction of lung growth, a known contributor to the high mortality in humans. Our findings of both de novo and inherited rare variants in the same gene may have implications in the design and analysis for other genetic studies of congenital anomalies.

Limiting hospital resources for acute appendicitis in children: Lessons learned from the U.S. epicenter of the COVID-19 pandemic.

INTRODUCTION: The COVID-19 pandemic resulted in the suspension of nonemergent surgeries throughout New York. Our tertiary care children's hospital pivoted towards a brief trial of intravenous (IV) antibiotic therapy in all patients in order to limit operating room (OR) utilization and avoid prolonged hospital stays. We describe our pandemic-based strategy for non-operative management (NOM) of appendicitis but with a limited duration of IV antibiotics. METHODS: We performed a retrospective study of children treated for acute appendicitis at our center from 3/31/2020 to 5/3/2020 during the peak of the New York pandemic. We compared appendicitis volume to similar months in prior years. We evaluated failure of NOM, length of stay, and compared characteristics of children we successfully treated with our expanded NOM protocol to previously published inclusion criteria for NOM. RESULTS: 45.5% of children (25/55) with acute appendicitis underwent NOM. Of the 30 who underwent surgery, 13 had complicated appendicitis while 17 had simple appendicitis. Three patients were COVID-positive, although none had respiratory symptoms. The majority of patients presenting with acute appendicitis (78.2%) did not meet previously published criteria for NOM. CONCLUSIONS: We treated a similar volume of children with acute appendicitis during the pandemic compared to prior years. We applied non-operative management to nearly half our patients, even as we expanded inclusion criteria for NOM to reduce OR utilization, but limited the duration of the antibiotic trial to avoid prolonged hospital stays. TYPE OF STUDY: Retrospective study. LEVEL OF EVIDENCE: IV.

Pharmacological prevention of surgery-accelerated metastasis in an animal model of osteosarcoma.

BACKGROUND: Osteosarcoma is a highly metastatic primary bone tumor that predominantly affects adolescents and young adults. A mainstay of treatment in osteosarcoma is removal of the primary tumor. However, surgical excision itself has been implicated in promoting tumor growth and metastasis, an effect known as surgery-accelerated metastasis. The underlying mechanisms contributing to surgery-accelerated metastasis remain poorly understood, but pro-tumorigenic alterations in macrophage function have been implicated. METHODS: The K7M2-BALB/c syngeneic murine model of osteosarcoma was used to study the effect of surgery on metastasis, macrophage phenotype, and overall survival. Pharmacological prevention of surgery-accelerated metastasis was examined utilizing gefitinib, a receptor interacting protein kinase 2 inhibitor previously shown to promote anti-tumor macrophage phenotype. RESULTS: Surgical excision of the primary tumor resulted in increases in lung metastatic surface nodules, overall metastatic burden and number of micrometastatic foci. This post-surgical metastatic enhancement was associated with a shift in macrophage phenotype within the lung to a more pro-tumor state. Treatment with gefitinib prevented tumor-supportive alterations in macrophage phenotype and resulted in reduced metastasis. Removal of the primary tumor coupled with gefitinib treatment resulted in enhanced median and overall survival. CONCLUSIONS: Surgery-accelerated metastasis is mediated in part through tumor supportive alterations in macrophage phenotype. Targeted pharmacologic therapies that prevent pro-tumor changes in macrophage phenotype could be utilized perioperatively to mitigate surgery-accelerated metastasis and improve the therapeutic benefits of surgery.

Gefitinib Inhibits Invasion and Metastasis of Osteosarcoma via Inhibition of Macrophage Receptor Interacting Serine-Threonine Kinase 2.

Most patients with osteosarcoma have subclinical pulmonary micrometastases at diagnosis. Mounting evidence suggests that macrophages facilitate metastasis. As the EGFR has been implicated in carcinoma-macrophage cross-talk, in this study, we asked whether gefitinib, an EGFR inhibitor, reduces osteosarcoma invasion and metastatic outgrowth using the K7M2-Balb/c syngeneic murine model. Macrophages enhanced osteosarcoma invasion in vitro, which was suppressed by gefitinib. Oral gefitinib inhibited tumor extravasation in the lung and reduced the size of metastatic foci, resulting in reduced metastatic burden. Gefitinib also altered pulmonary macrophage phenotype, increasing MHCII and decreasing CD206 expression compared with controls. Surprisingly, these effects are mediated through inhibition of macrophage receptor interacting protein kinase 2 (RIPK2), rather than EGFR. Supporting this, lapatinib, a highly specific EGFR inhibitor that does not inhibit RIPK2, had no effect on macrophage-promoted invasion, and RIPK2-/- macrophages failed to promote invasion. The selective RIPK2 inhibitor WEHI-345 blocked tumor cell invasion in vitro and reduced metastatic burden in vivo In conclusion, our results indicate that gefitinib blocks macrophage-promoted invasion and metastatic extravasation by reprogramming macrophages through inhibition of RIPK2.

The incidence of Marfan syndrome and cardiac anomalies in patients presenting with pectus deformities.

PURPOSE: The incidence of Marfan syndrome in the general population is 0.3%. Two-thirds of patients with Marfan syndrome have concurrent pectus deformity. However, incidence of Marfan syndrome and cardiac abnormalities in patients presenting with an isolated pectus deformity remains unknown. We sought to establish the degree of association between pectus deformities and these abnormalities, and whether referral of these patients for cardiac and genetic workup is warranted. METHODS: Our pediatric surgery group refers patients with pectus deformities for genetic and cardiac evaluation. We examined 415 records from 2009 to 2016, and identified 241 patients with a chief complaint of a pectus deformity. Patient characteristics, echocardiogram results, Haller indices, and genetic results were analyzed. RESULTS: The frequency of Marfan syndrome in our study was 5.3%. The incidence of Marfan was highest among patients with combined type pectus deformity (20%). Cardiac anomalies showed an overall incidence of 35%. Of those diagnosed with Marfan, 84% had cardiac abnormalities. CONCLUSION: More than 5% of patients presenting with a chief complaint of pectus deformity will have a diagnosis of Marfan syndrome, compared to 0.3% in the general population. Approximately a third of this population will have cardiac abnormalities. Referral of patients with pectus deformities for evaluation for Marfan syndrome and cardiac abnormalities is appropriate. LEVEL OF EVIDENCE: Level IV.

Intratibial Injection Causes Direct Pulmonary Seeding of Osteosarcoma Cells and Is Not a Spontaneous Model of Metastasis: A Mouse Osteosarcoma Model.

BACKGROUND: Although metastasis is the major cause of mortality in patients with osteosarcoma, little is known about how micrometastases progress to gross metastatic disease. Clinically relevant animal models are necessary to facilitate development of new therapies to target indolent pulmonary metastases. Intratibial injection of human and murine osteosarcoma cell lines have been described as orthotopic models that develop spontaneous pulmonary metastasis over time. However, there is variability in reported injection techniques and metastatic efficiency. QUESTIONS/PURPOSES: We aimed to characterize a widely used murine model of metastatic osteosarcoma, determine whether it is appropriate to study spontaneous pulmonary metastasis by establishing a reliable volume for intratibial injection, determine the incidence of primary tumor and metastatic formation, determine the kinetics of pulmonary metastatic seeding and outgrowth, and the contribution of the primary tumor to subsequent development of metastasis. METHODS: The metastatic mouse osteosarcoma cell line K7M2 was injected into the tibia of mice. The maximum volume that could be injected without leakage was determined using Evan's blue dye (n = 8 mice). Primary tumor formation and metastatic efficiency were determined by measuring the incidence of primary tumor and metastatic formation 4 weeks after intratibial injection (n = 30). The kinetics of metastatic development were determined by performing serial euthanasia at 1, 2, 3, and 4 weeks after injection (n = 24; five to six mice per group). Number of metastatic foci/histologic lung section and metastatic burden/lung section (average surface area of metastatic lesions divided by the total surface area of the lung) was calculated in a blinded fashion. To test the contribution of the primary tumor to subsequent metastases, amputations were performed 30 minutes, 4 hours, or 24 hours after injection (n = 21; five to six mice per group). Mice were euthanized after 4 weeks and metastatic burden calculated as described previously, comparing mice that had undergone amputation with control, nonamputated mice. Differences between groups were calculated using Kruskal-Wallis and one-way analysis of variance. RESULTS: The maximum volume of cell suspension that could be injected without leakage was 10 µL. Intratibial injection of tumor cells led to intramedullary tumor formation in 93% of mice by 4 weeks and resulted in detectable pulmonary metastases in 100% of these mice as early as 1 week post-injection. Metastatic burden increased over time (0.88% ± 0.58, week 1; 6.6% ± 5.3, week 2; 16.1% ± 12.5, week 3; and 40.3% ± 14.83, week 4) with a mean difference from week 1 to week 4 of -39.38 (p < 0.001; 95% confidence interval [CI], -57.39 to -21.37), showing pulmonary metastatic growth over time. In contrast, the mean number of metastatic foci did not increase from week 1 to week 4 (36.4 ± 33.6 versus 49.3 ± 26.3, p = 0.18). Amputation of the injected limb at 30 minutes, 4 hours, and 24 hours after injection did not affect pulmonary metastatic burden at 4 weeks, with amputation as early as 30 minutes post-injection resulting in a metastatic burden equivalent to tumor-bearing controls (48.9% ± 6.1% versus 40.9% ± 15.3%, mean difference 7.96, p = 0.819; 95% CI, -33.9 to 18.0). CONCLUSIONS: There is immediate seeding of the metastatic site after intratibial injection of the K7M2 osteosarcoma cell line, independent of a primary tumor. This is therefore not a model of spontaneous metastasis. CLINICAL RELEVANCE: This model should not be used to study the early components of the metastatic cascade, but rather used as an experimental model of metastasis. Improved understanding of this commonly used model will allow for proper interpretation of existing data and inform the design of future studies exploring the biology of metastasis in osteosarcoma.

The Macrophage Inhibitor CNI-1493 Blocks Metastasis in a Mouse Model of Ewing Sarcoma through Inhibition of Extravasation.

Metastatic Ewing Sarcoma carries a poor prognosis, and novel therapeutics to prevent and treat metastatic disease are greatly needed. Recent evidence demonstrates that tumor-associated macrophages in Ewing Sarcoma are associated with more advanced disease. While some macrophage phenotypes (M1) exhibit anti-tumor activity, distinct phenotypes (M2) may contribute to malignant progression and metastasis. In this study, we show that M2 macrophages promote Ewing Sarcoma invasion and extravasation, pointing to a potential target of anti-metastatic therapy. CNI-1493 is a selective inhibitor of macrophage function and has shown to be safe in clinical trials as an anti-inflammatory agent. In a xenograft mouse model of metastatic Ewing Sarcoma, CNI-1493 treatment dramatically reduces metastatic tumor burden. Furthermore, metastases in treated animals have a less invasive morphology. We show in vitro that CNI-1493 decreases M2-stimulated Ewing Sarcoma tumor cell invasion and extravasation, offering a functional mechanism through which CNI-1493 attenuates metastasis. These data indicate that CNI-1493 may be a safe and effective adjuvant agent for the prevention and treatment of metastatic Ewing Sarcoma.

Neonatal esophageal perforation: nonoperative management.

BACKGROUND: Esophageal perforation is a rare complication of enteric instrumentation in neonates. Enteric tube placement in micro-preemies poses a particular hazard to the narrow lumen and thin wall of the developing esophagus. The complication may be difficult to recognize or misdiagnosed as esophageal atresia, and is associated with considerable mortality. Historically, management of this life-threatening iatrogenic disease was operative, but trends have shifted toward nonoperative treatment. Here, we review neonatal esophageal perforation at our own institution for management techniques, risk factors, and outcomes. MATERIALS AND METHODS: Seven neonatal patients with esophageal perforation were identified and charts reviewed for demographics, comorbidities, etiology of perforation, diagnostic modalities, management decisions, complications, and outcomes. RESULTS: Mean gestational age was 27.2 ± 4.0 wk, and weight at diagnosis was 892 ± 674 g. All seven patients had esophageal perforation resulting from endotracheal or enterogastric intubation and were managed nonoperatively. Treatment included removal of the offending tube, nil per os, and antibiotics. Five patients required additional interventions: four tube thoracostomies for pneumothoraces and one peritoneal drain for pneumoperitoneum. Three patients died because of sequelae of prematurity (intraventricular hemorrhage, necrotizing enterocolitis, and sepsis). One patient was diagnosed as having esophageal atresia; esophagoscopy before surgical repair established the correct diagnosis. CONCLUSIONS: Neonates, particularly those under 1500 g, are at substantial risk for iatrogenic esophageal perforation during enterogastric intubation. Nonoperative management may be a safe initial strategy in the neonatal setting, but more aggressive interventions may ultimately be required. Despite recent improvement in early recognition of this injury, misdiagnosis still occurs.

Celecoxib inhibits Ewing sarcoma cell migration via actin modulation.

BACKGROUND: Ewing sarcoma (ES) is an aggressive childhood solid tumor in which 30% of cases are metastatic at presentation, and subsequently carry a poor prognosis. We have previously shown that treatment with celecoxib significantly reduces invasion and metastasis of ES cells in a cyclooxygenase-2-independent fashion. Celecoxib is known to downregulate ß-catenin independently of cyclooxygenase-2. Additionally, the actin cytoskeleton is known to play an important role in tumor micrometastasis. We hypothesized that celecoxib's antimetastatic effect in ES acts via modulation of one of these two targets. METHODS: ES cells were treated with celecoxib, and the levels of ß-catenin and total actin were examined by Western blot and quantitative polymerase chain reaction. Cells were transfected with small interfering RNA targeting ß-catenin, and invasion assays were performed. Immunofluorescence staining for ß-catenin and F-actin was performed on treated and untreated cells. Additionally, cells were subjected to a wound healing assay to assess migration. RESULTS: Celecoxib had no effect on the messenger RNA or protein levels of ß-catenin but did significantly decrease the amount of total actin within ES cells. Reduction of ß-catenin by small interfering RNA had no effect on invasion, and celecoxib treatment of the ß-catenin depleted cells continued to inhibit invasion. Immunofluorescence staining demonstrated no change in ß-catenin with treatment but did show a significant reduction in the amount of F-actin, as well as morphologic changes of the cells. Wound healing assays demonstrated that celecoxib significantly inhibited migration. CONCLUSIONS: Celecoxib does not exert its antimetastatic effects in ES through alteration of ß-catenin but does significantly modulate the actin cytoskeleton.

Celecoxib inhibits invasion and metastasis via a cyclooxygenase 2-independent mechanism in an in vitro model of Ewing sarcoma.

BACKGROUND/INTRODUCTION: Previously, we reported that celecoxib, a cyclooxygenase-2 (COX-2) inhibitor, prevented lung metastases but did not affect tumor growth in a model of Ewing sarcoma. Cyclooxygenase-2 inhibition has been proposed as an antimetastatic strategy. The mechanism of action remains unclear. METHODS: Ewing sarcoma cells were suspended in a soluble basement membrane extract (Cultrex; Trevigen, Inc, Gaithersburg, MD) and supplemented with celecoxib or with rofecoxib, a second COX-2 inhibitor, above a filter. Controls received solvent. After 48 hours, the cells that invaded through the basement membrane and filter were stained and counted. The assay was repeated with the addition of 500-nM prostaglandin E2 (PGE(2)). RESULTS: Invasion was significantly decreased in the celecoxib groups compared with the control. The addition of PGE(2) did not overcome celecoxib inhibition. Rofecoxib did not significantly affect invasion compared with control either with or without PGE(2). CONCLUSIONS: Celecoxib significantly inhibits invasion of Ewing sarcoma cells in vitro. Prostaglandin E2, a downstream product of COX-2, did not reverse in vitro inhibition, suggesting that celecoxib acts through a COX-2-independent mechanism. This is further supported by the failure of rofecoxib to inhibit invasion despite more selectively inhibiting COX-2.

A comparison of the cleft lift procedure vs wide excision and packing for the treatment of pilonidal disease in adolescents.

BACKGROUND/PURPOSE: The cleft lift for pilonidal disease is a flap procedure designed to counteract suspected causes of closed-technique failure. This study compares cleft lift with wide excision and packing in adolescents with respect to complications, healing, and recurrence. METHODS: Charts of all patients surgically treated for pilonidal disease at our institution from August 2000 to August 2009 were reviewed retrospectively. Wide excision was routinely performed until May 2007 when the cleft lift as described by Bascom was instituted here. Factors examined were postoperative complications, wound healing, and disease recurrence. RESULTS: Seventy patients (49 males, 21 females; mean age, 16 years; mean weight, 170.5 lb) with pilonidal disease underwent a total of 39 cleft lift procedures and 34 wide excision procedures. All but 1 cleft lift patient (97.4%) healed completely, whereas 25 (73.5%) of 34 patients in the excision group healed (P < .001). The remaining 9 excision patients had chronic wounds, 3 of whom have undergone cleft lift with full healing. One cleft lift patient had recurrent disease (2.5%) compared with 7 (20.6%) of 34 excision patients (P < .02). CONCLUSIONS: The cleft lift procedure is a superior treatment method of pilonidal disease in adolescents, resulting in primary healing, lower likelihood of recurrent disease, and simplified wound care.

Selective inhibition of cyclooxygenase-2 suppresses metastatic disease without affecting primary tumor growth in a murine model of Ewing sarcoma.

BACKGROUND/PURPOSE: Mammalian target of rapamycin suppression by rapamycin inhibits tumor growth and neovascularization via cyclooxygenase-2 (COX-2) downregulation with no effect on lung metastases. We hypothesize that combining a selective COX-2 antagonist (celecoxib) with rapamycin would decrease lung metastases. METHODS: Ewing sarcoma cells (SK-NEP-1) were surgically implanted into the left kidney of athymic mice (n = 40). The mice were divided into 4 treatment groups (control, rapamycin only, celecoxib only, and combination) and then killed at 6 weeks. Primary tumors were weighed. Vasculature was examined using lectin angiography and immunohistochemistry, and lung metastases were examined using H&E and CD99 immunostaining. Tumor weight and lung metastases were analyzed. RESULTS: Mean primary tumor weights were significantly reduced in the rapamycin-treated groups but not in the celecoxib-only group. Lectin angiography and endothelial markers immunostaining showed markedly decreased vascularity in the rapamycin-treated groups but not in the celecoxib-only group. Celecoxib-treated groups showed significantly fewer mice with lung metastases than non-celecoxib-treated groups. CONCLUSION: Celecoxib prevents lung metastasis in a murine model of Ewing sarcoma with no effect on tumor size or neovascularization. Cyclooxygenase-2 may represent a future potential target for metastatic disease prevention.

Laparoscopic inguinal hernia inversion and ligation in female children: a review of 173 consecutive cases at a single institution.

PURPOSE: Laparoscopic inguinal hernia inversion and ligation (LIHIL) is a method of hernia repair in which the hernia sac is inverted into the peritoneal cavity and subsequently ligated and excised. Since 2003, 5 surgeons at our institution have been performing LIHIL in girls. METHODS: A retrospective review of inguinal hernias in girls from 2003 to 2009 was performed. RESULTS: Two hundred forty-one LIHILs were performed on 173 girls. The average age of children undergoing LIHIL was 57 months (range, 1-210 months). Fifteen cases were ex-premature babies (8.7%). Of the unilateral inguinal hernias, 34% were found to have bilateral hernias intraoperatively, and these were repaired at the same operation. There have been no intraoperative complications. Postoperatively, there have been no wound complications and 2 recurrences (0.83%). Both recurrences were repaired using an open technique. CONCLUSIONS: Laparoscopic inguinal hernia inversion and ligation is a safe and effective operation in girls with a low recurrence rate. Benefits of this procedure include diagnosis and repair of the contralateral side using the same incisions, diagnosis of androgen insensitivity and other dysgenic situations, and excellent cosmesis. This operation is a straightforward technique that can be performed by most pediatric surgeons with basic laparoscopic skills.

Nonoperative management of symptomatic urachal anomalies.

INTRODUCTION: Symptomatic urachal anomalies are rare disorders that consist of urachal remnants or fistulas with or without an associated cyst. Traditionally, when a urachal anomaly was recognized, operative excision was performed. There has been a shift toward the nonoperative management of urachal anomalies at many centers, although there is little in the literature to support this practice. METHODS: A retrospective chart review of patients with urachal anomalies was performed from January 2002 to March 2008. Children with a draining umbilicus and no radiographic or surgical confirmation of a urachal anomaly were excluded. RESULTS: Fifteen patients with symptomatic urachal anomalies were identified. The average age was 3.5 years (4 weeks to 14 years). Symptoms included umbilical drainage (n = 10), abdominal pain (n = 6), omphalitis (n = 4), intraabdominal mass (n = 3), dysuria (n = 1), recurrent urinary tract infections (n = 1), and fever (n = 4). The diagnosis was confirmed by ultrasound (n = 13) and/or computed tomographic scan (n = 4). The surgically treated cases included 7 urachal cysts (5 uninfected, 2 infected) and 1 patent urachal fistula. Mean follow-up is 37 months, and there have been no reported recurrences. Those treated without surgical excision included 4 patent urachal fistulas (mean follow-up, 20 months-no recurrences) and 3 infected urachal cysts (percutaneous drainage [n = 2] and laparoscopic drainage [n = 1]-no recurrences on ultrasound at 26 months). CONCLUSION: Nonoperative management of urachal anomalies is a reasonable approach and may be extended to infected urachal cysts after initial drainage. Infected cysts that are adequately drained seem to obliterate with time. Modern ultrasonography facilitates thorough follow-up. We propose a treatment algorithm for the management of suspected urachal anomalies.

Intrathoracic glial implants in a child with gliomatosis peritonei.

Glial peritoneal implants, commonly referred to as gliomatosis peritonei, are an occasional feature of ovarian teratomas. They are benign nodules of mature glial tissue and usually do not adversely affect outcome. We present the case of a 12-year-old girl who underwent excision of an immature ovarian teratoma, along with biopsies of multiple glial peritoneal implants. She also had a 2-cm right-sided pleural mass, which turned out to be normal glial tissue that was histologically indistinguishable from the peritoneal glial tissue. Pleural gliomatosis has not been described in the literature. The pathophysiology of gliomatosis peritonei was originally thought to be the direct extrusion or lymphatic spread of glial cells from the associated teratoma, although it has been postulated that the glial implants may instead be the result of pluripotent Mullerian stem cells that undergo metaplasia. This report provides evidence to bolster the metaplastic theory.

Cyclooxygenase 2 mediates the antiangiogenic effect of rapamycin in Ewing sarcoma.

BACKGROUND: Rapamycin can inhibit tumor growth and angiogenesis in various human cancers. Cyclooxygenase 2 (COX-2) is involved in the angiogenic process. We hypothesized that the antiangiogenic effect of rapamycin may be mediated by suppression of COX-2. METHODS: Ewing sarcoma (ES) cells were implanted in athymic mice. Selected animals were treated with rapamycin for 5 weeks. Tumor vascularity was assessed by lectin perfusion angiography and immunohistochemistry. Phosphorylation of mammalian target of rapamycin pathway proteins was determined by Western blot analysis. Staining of COX-2 protein was determined by immunohistochemistry, and expression of COX-2 messenger RNA levels was assessed with quantitative real-time (RT) polymerase chain reaction. RESULTS: Mean tumor weights were significantly reduced in the treated group (5.43 g +/- 1.43 SEM vs 0.49 g +/- 0.15 SEM, P < .003). There was abundant vasculature in the control group and blunted vascularity in the treated xenografts. The phosphorylation of p70s6k and Akt was not inhibited in the rapamycin-treated tumors. Cyclooxygenase 2 was suppressed in the treated xenografts at both the protein and messenger RNA levels. CONCLUSION: Low-dose rapamycin inhibits tumor growth and angiogenesis in human ES without inhibiting the phosphorylation of p70s6k and Akt. Cyclooxygenase 2 levels are inhibited by low-dose treatment of ES with rapamycin. Cyclooxygenase 2 suppression may mediate the antiangiogenic effect of rapamycin in Ewing sarcoma.

Vascular remodeling marks tumors that recur during chronic suppression of angiogenesis.

The potential for avoiding acquired resistance to therapy has been proposed as one compelling theoretical advantage of antiangiogenic therapy based on the normal genetic status of the target vasculature. However, previous work has demonstrated that tumors may resume growth after initial inhibition if antiangiogenic blockade is continued for an extended period. The mechanisms of this recurrent growth are unclear. In these studies, we characterized molecular changes in vasculature during apparent resumption of xenograft growth after initial inhibition by vascular endothelial growth factor blockade, "metronome" topotecan chemotherapy, and combined agents in a xenograft murine model of human Wilms' tumor. Tumors that grew during antiangiogenic blockade developed as viable clusters surrounding strikingly remodeled vessels. These vessels displayed significant increases in diameter and active proliferation of vascular mural cells and expressed platelet-derived growth factor-B, a factor that functions to enhance vascular integrity via stromal cell recruitment. In addition, remodeled vessels were marked by expression of ephrinB2, required for proper assembly of stromal cells into vasculature. Thus, enhanced vascular stability appears to characterize tumor vessel response to chronic antiangiogenesis, features that potentially support increased perfusion and recurrent tumor growth.