Optical Tomographic and Magnetic Resonance Imaging of Tumor Growth and Regression in Mice treated with VEGF Blockade.

Small animal imaging systems now allow researchers to non-invasively monitor the progression of diseases in living small animals and study the efficacy of drugs and treatment protocols. Magnetic resonance imaging (MRI) is an established imaging modality capable of obtaining high resolution anatomical images which are sensitive to blood volume, blood flow, and metabolic rate of oxygen. Optical tomography, on the other hand, is an emerging imaging modality, which, while much lower in spatial resolution and insensitive to blood flow, can separate the effects of oxyhemoglobin, deoxyhemoglobin, and blood volume with high temporal resolution. We illustrate how these imaging modalities can supplement each other and cross validation can be performed by applying both modalities to imaging of tumors growth & regression in mice that are treated with a vascular endothelial growth factor (VEGF) antagonist.

Outcomes of unrelated cord blood transplantation in pediatric recipients.

We report results of unrelated cord blood transplants (UCBT) in 29 pediatric recipients in one center and the risk factors associated with survival. Median age: 9 years (0.5-20); diagnosis: ALL (9), AML (4), CML (1), HD (3), HLH (1), NHL (3), NBL (2); B-thal (1), FA (1), FEL (1), Krabbe (1), WAS (1), SAA (1); median follow-up: 11 months; conditioning: total body irradiation (TBI)-ablative (14), chemotherapy-ablative (6) and reduced intensity chemotherapy (9); GVHD prophylaxis: MMF/FK506 (18), cyclosporin A (CsA)+steroids+/-MMF (7) or CsA+methotrexate (MTX) (4); median total nucleated cells (TNC): 3.8 x 10(7)/kg (1.1-11); median CD34+: 2.3 x 10(5)/kg (0.2-9.9); and HLA match: 2 (6/6), 5 (5/6), 22 (4/6). Neutrophil engraftment by cumulative incidence curves 63% (median 28 (95% confidence interval (CI) 18-32)). Probability of >/=grade II acute graft-versus-host disease (aGVHD) by day +60 27%, >/=grade III aGVHD 20% and chronic graft-versus-host disease 3%. Estimated 1-year overall survival (OS) 46% (95% CI 30-71) and standard risk 60% (95% CI 29-100%). Variables associated with improved survival by multivariate analysis include non-TBI-ablative conditioning (P=0.024), CD34+/kg (P=0.038) and gender (P=0.048). These results suggest that CD34/kg cell dose and non-TBI-ablative conditioning may be important variables influencing OS following UCBT in pediatric recipients. Given the small number of patients, these results should be viewed cautiously.

A pilot study of reduced intensity conditioning and allogeneic stem cell transplantation from unrelated cord blood and matched family donors in children and adolescent recipients.

Reduced intensity (RI) allogeneic stem cell transplantation (AlloSCT) was initially demonstrated in adults following HLA-matched family and unrelated adult donor AlloSCT. There is little information about RI AlloSCT in children. We report results of a pilot study of RI AlloSCT in 21 recipients (< or =21 years). Age: median 13 (0.5-21) years, 8F:13M, 14 unrelated cord blood units (UCB) (10 4/6, 4 5/6), two related BM (6/6, 5/6), four related PBSC (2 6/6, 2 5/6), and one related BM+PBSC (6/6). RI: fludarabine, busulfan (n=14); fludarabine, cyclophosphamide (n=4); fludarabine, melphalan (n=1); total body irradiation, fludarabine, cyclophosphamide (n=1); or fludarabine, cyclophosphamide, and etoposide (n=1). Graft-versus-host disease prophylaxis: FK506 0.03 mg/kg/day and mycophenolate mofetil 15 mg/kg/q 12 h. UCB median nuc/kg and CD34/kg was 4.3 x 10(7)/kg (0.9-10.8) and 1.9 x 10(5)/kg (0.3-6.9), and related BM/PBSC median nuc/kg and CD34/kg was 8.3 x 10(8) (4.7-18.9) and 5.0 x 10(6)/kg (4.6-6.4). Maximal chimerism following unrelated cord blood transplantation, 100% x 7, 98% x 1, 95% x 2, 55% x 1, and 0% x 3; related PBSC/BM, 100% x 5, 65% x 1, and 55% x 1. Graft failure occurred in 5/21 (24%). In summary, RI AlloSCT in children is feasible and tolerable (< or =25% GF) and results in > or =85% of recipients initially achieving > or =50% donor chimerism.

Novel use of an established agent: Topotecan is anti-angiogenic in experimental Wilms tumor.

BACKGROUND/PURPOSE: Antiangiogenic agents offer a new approach to the treatment of aggressive neoplasms, yet very few agents are available for current use. The authors have shown previously the efficacy of antiangiogenic therapy in experimental Wilms tumor, using an investigative antibody. They hypothesized that topotecan, administered in a regimen targeting endothelial cells, would suppress tumor growth and angiogenesis in experimental Wilms tumor. METHODS: Experimental tumors were induced in the left kidneys of athymic mice by injection of cultured Wilms tumor cells. Topotecan (0.36, 0.6, 1.0, 2.0, and 3.0 mg/kg) or vehicle was injected intraperitoneally in 2 cycles over a 6-week period. Fluorescein angiograms and platelet endothelial cell adhesion molecule-1 staining of primary tumors were performed to ascertain vascular architecture. Endothelial apoptosis was assessed by TdT-mediated dUTP nick end labeling assay. RESULTS: Tumor weights were reduced significantly in treated versus control animals, even in the lowest-dose group. Endothelial cell staining and angiography results showed relatively sparse vascularity in treated xenografts. Endothelial apoptosis was observed in treated but not control tumors. CONCLUSIONS: Topotecan, delivered in an "antiangiogenic" regimen, even at very low doses, significantly inhibited growth of experimental Wilms tumors. No adverse effects were noted at low doses. Thus, the established chemotherapy agent topotecan may be useful in a novel role: as antiangiogenic therapy. J Pediatr Surg 36:1781-1784.

Combination antiangiogenic therapy: increased efficacy in a murine model of Wilms tumor.

BACKGROUND/PURPOSE: Antibody to vascular endothelial growth factor (anti-VEGF) suppresses tumor growth and metastasis in experimental Wilms tumor. However, tumor growth accelerates if antibody is withdrawn. As recently shown, low-dose, frequently administered topotecan, a topoisomerase-1 inhibitor, has anti-angiogenic activity. The authors hypothesized that combined topotecan/anti-VEGF therapy would suppress tumor growth and metastasis more durably than either agent alone. METHODS: Xenografts were induced by intrarenal injection of human Wilms tumor cells in athymic mice (n = 59). Mice were divided into control (n = 10), anti-VEGF (n = 16), topotecan (n = 17), and topotecan plus anti-VEGF (n = 16) groups. All control and half the treated mice were killed at week 6. Remaining ("rebound") mice were maintained without treatment until week 8. Tumor vasculature was mapped by fluorescein angiography/PECAM immunostaining. Endothelial apoptosis was assessed by TUNEL assay. RESULTS: 6 weeks: Tumor weights were reduced significantly in treated mice (P <.003 v control). Seven of ten control and 1 of 25 treated mice displayed lung metastases (P <.003). Rebound tumors were largest in topotecan-only, intermediate in antibody-treated, and smallest in combination-treated mice. Immunostaining and angiography results showed sparse vascularity in treated xenografts. Endothelial apoptosis was observed only in treated tumors. CONCLUSION: Combination low-dose topotecan and anti-VEGF antibody therapy is antiangiogenic and suppresses tumor growth and metastasis in experimental Wilms tumor more durably than either agent alone.

Effective therapy of a vascular tumor of infancy with vincristine.

Vascular tumors are common in infancy, affecting as many as 10% of children. These lesions often follow a benign course, with an initial proliferative phase followed by spontaneous involution, and require no therapy. Others manifest explosive early growth and Kasabach-Merritt phenomenon, requiring therapeutic intervention. Occasionally, some bulky tumors threaten life or vision because of mass effect, also mandating intervention. Steroids are the mainstay of therapy, but often are ineffective. Interferon alpha (2a and 2b) has been used as second-line therapy in cases of steroid failure. However, interferon therapy has been associated with a significant incidence of spastic diplegia. The authors present the case of a 3-month-old girl in whom respiratory distress secondary to tracheal compression developed. Magnetic resonance imaging and magnetic resonance angiography showed a large cervicothoracic lesion encasing the great vessels and displacing the airway. She did not display associated Kasabach-Merritt phenomenon. The lesion proved refractory to standard steroid therapy, but responded dramatically to 4 cycles of vincristine (0.05 mg/kg). Although this agent has been used in children with life-threatening Kasabach-Merritt phenomenon, this is the first time it has been described in the setting of compromised vital function. Vinca alkaloids recently have been shown to have potent antiangiogenic activities in experimental models. Given the low predicted incidence of side effects at this dose, vincristine used as an antiangiogenic agent may prove an attractive alternative therapy for patients with life-threatening vascular tumors of infancy.

All angiogenesis is not the same: Distinct patterns of response to antiangiogenic therapy in experimental neuroblastoma and Wilms tumor.

BACKGROUND/PURPOSE: Neuroblastoma and Wilms tumor exhibit different patterns of metastasis, invasion, and therapeutic response. Vascular endothelial growth factor (VEGF) is an angiogenic factor expressed in both tumors. The authors hypothesized that because the clinical behavior of these tumors differs, the response to anti-VEGF therapy would be distinct, and tumor vascular architectures would reflect this distinction. METHODS: Xenografts were induced by intrarenal injection of cultured cells in athymic mice. After 1 week, anti-VEGF antibody or vehicle were administered for 5 weeks before sacrifice. Additional animals were maintained for 3 weeks after termination of antibody injections to assess rebound growth of tumors. Fluorescein angiography was performed in selected animals. RESULTS: Neuroblastoma control and treated tumor weights were not significantly different (1.48 g v 0.77 g, P =.34). By comparison, as previously reported, antibody-treated Wilms tumors were growth inhibited. Angiograms of treated (but not control) neuroblastomas displayed novel rounded structures at vessel branches, which the authors term terminal vascular bodies (TVBs). Wilms tumor vessels displayed no such alteration. CONCLUSIONS: Neuroblastoma xenografts are less effectively suppressed by anti-VEGF antibody than Wilms tumors. Neuroblastoma vascular architecture displays a novel alteration during antibody administration, which attenuates when antibody is withdrawn. These studies suggest that angiogenesis is differently regulated in experimental neuroblastoma and Wilms tumor.

Highly specific antiangiogenic therapy is effective in suppressing growth of experimental Wilms tumors.

BACKGROUND/PURPOSE: Pathologic angiogenesis in tumors is a potential target for novel therapies. Vascular endothelial growth factor (VEGF) is an angiogenic promoter present in a wide variety of human tumors. VEGF is expressed as 4 isoforms; one of these, VEGF165, predominates in human tumors. The authors hypothesized that antagonism of VEGF165 by a specific aptamer would block tumor growth in an experimental model of Wilms tumor. METHODS: VEGF isoform expression in clinical (n = 2) and experimental tumors were evaluated by reverse transcription polymerase chain reaction (RT-PCR). Tumors were induced in NCR nude mice (n = 32) by intrarenal injection of 10(6) cultured Wilms tumor cells. At 1 week, aptamer (n = 16) or vehicle (n = 16) treatment was started and continued daily for 5 weeks. RESULTS: At 6 weeks tumors weighed 84% less in treated versus control animals (0.69 v 4.41 g; P <.028), without observed adverse effects and similar to suppression previously reported using nonisoform-specific anti-VEGF antibody (94% to 96%). CONCLUSIONS: Anti-VEGF165 aptamer effectively suppressed primary tumor growth in experimental animals with no observed adverse effects. Development of highly specific antiangiogenic therapies may be of particular benefit to pediatric patients.

The effect of confirmation calls on appointment-keeping behavior of patients in a children's hospital dental clinic.

PURPOSE: The objective of this prospective, randomized, controlled study was to evaluate whether confirmation calls made one or two working days before scheduled appointments reduce the percentage of broken appointments in a children's hospital dental clinic. METHODS: Patients were randomly assigned to three groups: 1) confirmation call made one working day before appointment, 2) confirmation call made two working days before appointment; and 3) control group (no confirmation call). Clinic staff made confirmation calls during normal office hours. Patient arrival was classified as 1) < or =15 minutes late; 2) > 15 minutes late; or 3) broken appointment. RESULTS: Three hundred and thirteen subjects were enrolled in the study: 77 subjects in group 1; 71 subjects in group 2; and 84 subjects in the control group. Eighty-one subjects (26%) could not be contacted by telephone. Overall, there was a 62% reduction in broken appointments among patients who received a confirmation call as compared to the control group. There was no significant difference between confirmation calls placed one or two working days prior to the appointment (P=0.51). Confirmation calls had no effect on punctuality. In comparing indigent care and private insurance, there was no significant difference in broken appointments. However, within the private insurance group, a confirmation call resulted in 93% of patients keeping their appointment as compared to 63% in the control group (P<0.001). No significant difference was noted in the indigent care group, with 79% of patients in the confirmation call group keeping their appointments as compared to 66% in the control group (P=. 093). CONCLUSIONS: Confirmation calls reduced the percentage of broken appointments in a pediatric dental clinic. There was no difference between calls placed one or two working days prior to the appointment. The greatest reduction in broken appointments was shown in the private insurance group.

Suppression of primary tumor growth in a mouse model of human neuroblastoma.

BACKGROUND/PURPOSE: Neuroblastoma is the most common tumor of the abdomen in children. Consistently effective treatments are lacking for aggressive disease. The authors previously reported that therapy with anti-vascular endothelial growth factor (VEGF) antibodies suppresses both growth and metastasis in an experimental model of Wilms' tumor. The authors hypothesized that, in a parallel model of neuroblastoma, anti-VEGF treatment would inhibit (1) growth and (2) metastasis. METHODS: Primary tumors were established in the kidneys of nude mice. In cohort 1 (n = 42), mice were killed at 3 time-points, and tissues were evaluated histologically. Tumors were assayed for VEGF. In cohort 2 (n = 28), anti-VEGF antibody or vehicle was administered. Tumor weights and the incidence of metastases in the 2 groups were compared. VEGF deposition was evaluated by immunohistochemistry. RESULTS: Mice displayed large tumors with liver and lung metastases. VEGF levels in tumors increased over time. Antibody-treated animals displayed significantly smaller tumors, but incidence and size of metastases were unaffected. VEGF was localized to tumor stroma immunohistochemically, with no difference in pattern observed in control and antibody-treated tumors. CONCLUSIONS: Anti-VEGF antibodies inhibit primary tumor growth in experimental neuroblastoma, but not metastasis. This may contrast with the effect of the same antibody in a parallel model of Wilms' tumor.

Anti-VEGF antibody suppresses primary tumor growth and metastasis in an experimental model of Wilms' tumor.

BACKGROUND/PURPOSE: Vascular endothelial growth factor (VEGF) has been shown previously to correlate with tumor growth and metastasis in an experimental model of anaplastic Wilms' tumor. The authors hypothesized that treatment with anti-VEGF antibodies would suppress both primary tumor growth and metastasis in this model. METHODS: Tumors were induced in the right kidneys of nude mice by the injection of cultured Wilms' tumor cells. After 1 week, anti-VEGF treatment was begun with injection of either vehicle or an anti-VEGF antibody intraperitoneally. Mice were killed after 4.5 weeks of treatment and tumor weights and the incidence of metastases evaluated. RESULTS: Anti-VEGF treatment resulted in a greater than 95% reduction in tumor weight (P < .0001). Anti-VEGF treatment also abolished the establishment of lung metastases (40% in control animals, P < .003). Cessation of treatment resulted in rebound tumor growth. CONCLUSION: Anti-VEGF therapy can suppress both primary tumor growth and the establishment of metastases in experimental anaplastic Wilms' tumor.

Antitumor activity of CEP-751 (KT-6587) on human neuroblastoma and medulloblastoma xenografts.

Neuroblastoma (NBL) and medulloblastoma (MBL) are tumors of the neuroectoderm that occur in children. NBL and MBL express Trk family tyrosine kinase receptors, which regulate growth, differentiation, and cell death. CEP-751 (KT-6587), an indolocarbazole derivative, is an inhibitor of Trk family tyrosine kinases at nanomolar concentrations. This study was designed to determine the effect of CEP-751 on the growth of NBL and MBL cell lines as xenografts. In vivo studies were conducted on four NBL cell lines (IMR-5, CHP-134, NBL-S, and SY5Y) and three MBL cell lines (D283, D341, and DAOY) using two treatment schedules: (a) treatment was started after the tumors were measurable (therapeutic study); or (b) 4-6 days after inoculation, before tumors were palpable (prevention study). CEP-751 was given at 21 mg/kg/dose administered twice a day, 7 days a week; the carrier vehicle was used as a control. In therapeutic studies, a significant difference in tumor size was seen between treated and control animals with IMR-5 on day 8 (P = 0.01), NBL-S on day 17 (P = 0.016), and CHP-134 on day 15 (P = 0.034). CEP-751 also had a significant growth-inhibitory effect on the MBL line D283 (on day 39, P = 0.031). Inhibition of tumor growth of D341 did not reach statistical significance, and no inhibition was apparent with DAOY. In prevention studies, CEP-751 showed a modest growth-inhibitory effect on IMR5 (P = 0.062) and CHP-134 (P = 0.049). Furthermore, inhibition of growth was greater in the SY5Y cell line transfected with TrkB compared with the untransfected parent cell line expressing no detectable TrkB. Terminal deoxynucleotidyl transferase-mediated nick end labeling studies showed CEP-751 induced apoptosis in the treated CHP-134 tumors, whereas no evidence of apoptosis was seen in the control tumors. Finally, there was no apparent toxicity identified in any of the treated mice. These results suggest that CEP-751 may be a useful therapeutic agent for NBL or MBL.

Multipoint analysis of human chromosome 11p15/mouse distal chromosome 7: inclusion of H19/IGF2 in the minimal WT2 region, gene specificity of H19 silencing in Wilms' tumorigenesis and methylation hyper-dependence of H19 imprinting.

WT2 is defined by maternal-specific loss of heterozygosity (LOH) on chromosome 11p15.5 in Wilms' tumors (WTs). The imprinted H19 gene, in this region, is silenced and hypermethylated in most WTs, and this is linked to pathological biallelic expression of IGF2. However, H19 and IGF2 lie within a larger imprinted domain, and the gene specificity of H19 epimutation has been a persistent question. To address this, we assessed LOH, gene expression and DNA methylation at multiple sites in and around the imprinted domain. LOH mapping showed that the entire domain, including IGF2/H19, is within the minimal WT2 region. Genes within the domain, including IPL/TSSC3/BWR1C, IMPT1/ORCTL2/BWR1A/TSSC5, KvLQT1/KCNA9 and TAPA1/CD81, as well as the zinc finger gene ZNF195/ZNFP104 near the centromeric border, were expressed persistently in many WTs. DNA hypermethylation was not detected with 5" upstream probes for IPL, IMPT1, KvLQT1 and ZNF195 in WTs or WT-associated kidneys. Fully developed WTs showed variable hypomethylation at an imprinted CpG island in a KvLQT1 intron, but this was only complete in the cases with LOH and was not observed in pre-neoplastic WT-associated kidneys with H19 epimutation. Analysis of the corresponding region of mouse chromosome 7 using methyltransferase-hypomorphic mice showed that the H19 imprint was fully erased, but that the allelic bias at Ipl, Impt1, p57 Kip2 and, to a lesser extent, Kvlqt1, persisted. Pre-existing massive allelic asymmetry for DNA methylation and hyper-dependence of transcription on methylation status may underlie the mechanism of gene-specific silencing of H19 in Wilms' tumorigenesis.

Schwann cell-conditioned medium promotes neuroblastoma survival and differentiation.

Neuroblastomas are histopathologically heterogeneous, ranging from immature malignant tumors to benign ganglioneuromas. The amount of Schwann cell stroma greatly increases with neuroblastoma differentiation, and these Schwann cells appear to be normal cells that infiltrate the tumor. To determine whether Schwann cells influence neuroblast differentiation, four human neuroblastoma cell lines were cultured in the presence or absence of human Schwann cell-conditioned medium for 7 days. Neuroblastoma cell survival, as determined by a colorimetric assay, more than doubled in three of the four neuroblastoma cell lines in the Schwann cell-conditioned medium. There was a corresponding reduction in apoptosis as measured by a nick-end labeling assay, with little change in mitotic rate. Schwann cell-conditioned medium induced extensive neurite outgrowth in all of the neuroblastoma cell lines, and these processes contained mature neurofilament in three of the cell lines. These results indicate that Schwann cells produce soluble substances capable of supporting survival and differentiation in neuroblastoma cell lines. This may represent a biological mechanism responsible for neuronal differentiation in stroma-rich neuroblastomas.

Articulation and nasality changes resulting from sustained palatal fistula obturation.

OBJECTIVE: The purpose of the study was to determine differences in articulation and nasality with obturation over time in children with a palatal fistula. DESIGN: Articulation and nasality were measured with the fistula open, immediately after obturation, and 4 to 7 weeks postobturation. SETTING, PATIENTS, PARTICIPANTS: Subjects were 15 patients with a palatal fistula secondary to a repaired cleft palate who were seen through the Orofacial Program, Utah Department of Health, ranging in age from 4 years 6 months to 13 years 1 month. INTERVENTIONS: Acrylic palatal obturators were designed to provide coverage specific to the unique shape and location of each child's fistula. Obturators were cemented to molar teeth using wire clasps for control of usage. MAIN OUTCOME MEASURES: Measurements consisted of listener judgments of hypernasality, hyponasality, and nasal emissions; instrumental ratings of nasalance using the Nasometer 6200-2; and performance on a standardized articulation test. RESULTS: Significant improvement occurred only on nasal emission measures from the preobturation condition to immediate postobturation. However, significant improvement was found in articulation, listener judgments of hypernasality, nasal emissions, and Nasometric Nasal Sentence mean scores from the preobturation condition to 4 to 7 weeks postobturation and from the immediate postobturation condition to 4 to 7 weeks postobturation. No significant differences were found between conditions for listener judgments of hyponasality and Nasometric Zoo and Rainbow Passage scores. Obturation of the palatal fistula over a 4- to 7-week period resulted in no adverse effect on articulation ability, perceptual ratings of nasality, or instrumental ratings of nasalance. CONCLUSIONS: Clinical management of patients with a palatal fistula can be enhanced with treatment using obturation over time. For subjects who continue to exhibit hypernasality immediately postobturation, sustained obturation is advocated prior to consideration of surgical intervention for treatment of a palatal fistula and/or velopharyngeal dysfunction.

Biology and genetics of human neuroblastomas.

PURPOSE: Neuroblastomas have a variety of clinical behaviors, from spontaneous regression or differentiation to early metastasis and death. We have examined a variety of genetic variables that might explain or predict the clinical behavior. PATIENTS AND METHODS: We have studied DNA or RNA from a number of children enrolled in clinical trials with the major pediatric oncology cooperative groups. RESULTS: We propose that neuroblastomas may be classified into three subsets with distinct biological features and clinical behavior. The first subset consists of those tumors with hyperdiploid modal karyotypes and high TRK-A expression. Patients with these tumors are usually infants with low stages of disease and a very favorable outcome. The second group consists of tumors that have a near-diploid DNA content, usually with 1p allelic loss or other structural changes, but they lack MYCN amplification, and TRK-A expression is low. The patients are generally older, with advanced stages of disease and an intermediate outcome. The third group is characterized by tumors with MYCN amplification, 1p allelic loss, and low or absent TRK-A expression. The patients are 1-5 years of age and have advanced stages of disease, rapid tumor progression, and a very poor prognosis. Current evidence suggests the tumor types are genetically distinct, and one type seldom if ever evolves into another. CONCLUSIONS: Identification of these genetic and clinical subsets permits a more accurate prediction of outcome. This, in turn, allows more appropriate selection of therapeutic intensity to minimize side effects in those with a favorable outcome but optimize the chance of cure in those requiring aggressive treatment.

Expression of TrkA, TrkB and TrkC in human neuroblastomas.

There is considerable interest in the role of the TRK family of neurotrophin receptors in regulating the survival, growth and differentiation of normal and neoplastic nerve cells. Indeed, there is increasing evidence that TRK genes play an important role in the biology and clinical behavior of neuroblastomas, tumors of the peripheral nervous system. Evidence from several independent studies suggests that high expression of TrkA is an indicator of favorable outcome, and there is an inverse correlation between TrkA expression and N-myc amplification. In addition, some primary neuroblastomas differentiate in vitro in the presence of NGF but die in its absence. We have evidence that coexpression of full-length TrkB and BDNF is associated with N-myc amplification and may represent an autocrine survival pathway. Conversely, truncated TrkB is expressed predominantly in differentiated tumors. Finally, Trk-C is expressed in favorable neuroblastomas, essentially all of which also express TrkA. In summary, the study of neurotrophin receptor expression and function in neuroblastomas may provide important insights into the role that these pathways play in the pathogenesis and clinical behavior of this tumor. Ultimately, these pathways may provide attractive targets for the development of therapy aimed at inducing differentiation or programmed cell death in these tumors.

Expression and function of Trk-C in favourable human neuroblastomas.

Human neuroblastomas express the neurotrophin receptors trk-A and trk-B. Favourable outcome is associated with expression of trk-A, while unfavourable, MYCN amplified tumours express trk-B. In this study we examined the expression of trk-C in primary neuroblastoma tumour-derived cell lines. We found by Northern blot analysis that trk-C mRNA is expressed in 14 of 55 (25%) primary tumours. Trk-C was expressed in significantly more lower stage tumours (stage 1, 2, 4S) than higher stage tumours (stage 3, 4, P < 0.04). The expression of trk-C was correlated positively with survival and negatively correlated with MYCN amplification. We also studied the function of trk-C in transfected cell lines and found that NT-3 promotes both cell survival and differentiation. Our results suggest that trk-C is involved in the biology of favourable neuroblastomas.

Expression of TrkC in favorable human neuroblastomas.

Human neuroblastomas have been found to express the neurotrophin receptors TrkA and TrkB. Expression of TrkA correlates with favorable outcome, while expression of full-length TrkB is associated with unfavorable, more aggressive, N-myc amplified tumors. In this study we have determined the expression of TrkC in neuroblastoma primary tumors and cell lines. Using probes for the extracellular domain and the tyrosine kinase domain of human TrkC, we found by Northern analysis that TrkC mRNA is expressed in 14 of 55 (25%) tumors from a representative panel of neuroblastomas. A 14 kb transcript was detected by both probes, indicating that it would encode the full-length TrkC protein. A significant association was found between TrkC mRNA expression detected by Northern analysis and lower stage tumors [stage 1, 2, 4S, 11 of 30 (37%); vs stage 3, 4, 3 of 25 (12%), chi2 = 4.4, P < 0.04]. Only one of eight primary tumors with N-myc amplification had detectable TrkC mRNA expression and none of the eight neuroblastoma cell lines expressed TrkC by Northern analysis. Our results suggest that TrkC is involved in the biology of favorable neuroblastomas.