Cross-talk between Schwann cells and neuroblasts influences the biology of neuroblastoma xenografts

Neuroblastoma (NB) tumors with abundant schwannian stroma have a differentiated phenotype, low vascularity, and are associated with a favorable prognosis. These observations suggest that cross-talk between Schwann cells and neuroblasts may influence tumor biology. To test this hypothesis, we developed a novel NB xenograft model with infiltrating mouse Schwann cells. Human SMS-KCNR NB cells were injected intrafascicularly (sciatic nerve-engrafted NB, n = 19) or outside the sciatic nerve (control, n = 12). Xenografts were harvested 4 to 12 weeks after tumor cell inoculation for histological studies. Schwann cells were immunostained with S-100 and species-specific p75(NGFR), major histocompatibility complex, and human leukocyte antigen antibodies. The number of proliferating cells, infiltrating Schwann cells, apoptotic cells, differentiated neuroblasts, and blood vessels in the sciatic nerve-engrafted NB tumors were compared to controls. Significantly more Schwann cells were detected in the sciatic nerve-engrafted NB xenografts than controls (P < 0.001). The infiltrating Schwann cells were S-100-positive and reacted with anti-mouse major histocompatibility complex class Ib and p75(NGFR) but not anti-human p75(NGFR) and human leukocyte antigen class I antibodies. The sciatic nerve-engrafted tumors also had lower numbers of proliferating neuroblasts, higher numbers of differentiated neuroblasts and apoptotic cells, and decreased vascular density compared to controls. Our results indicate that infiltrating Schwann cells of mouse origin are capable of promoting human neuroblast differentiation, inducing apoptosis, and inhibiting proliferation and angiogenesis in vivo.

Association of Epigenetic Inactivation of RASSF1A with Poor Outcome in Human Neuroblastoma

PURPOSE

To investigate the prevalence and potential clinical significance of epigenetic aberrations in neuroblastoma (NB).

EXPERIMENTAL DESIGN

The methylation status of 11 genes that are frequently epigenetically inactivated in adult cancers was assayed in 13 NB cell lines. The prevalence of RASSF1A and TSP-1 methylation was also analyzed in 56 NBs and 5 ganglioneuromas by methylation-specific PCR. Associations between the methylation status of RASSF1A and TSP-1 and patient age, tumor stage, tumor MYCN status, and patient survival were evaluated.

RESULTS

Epigenetic changes were detected in all 13 NB cell lines, although the pattern of gene methylation varied. The putative tumor suppressor gene RASSF1A was methylated in all 13 cell lines, and TSP-1 and CASP8 were methylated in 11 of 13 cell lines. Epigenetic changes of DAPK and FAS were detected in only small numbers of cell lines, whereas none of the cell lines had methylation of p16, p21, p73, RAR-beta2, SPARC, or TIMP-3. RASSF1A was also methylated in 70% of the primary NB tumors tested, and TSP-1 methylation was detected in 55% of the tumors. RASSF1A methylation was significantly associated with age >1 year (P < 0.01), high-risk disease (P < 0.016), and poor survival (P < 0.001). In contrast, no association between TSP-1 methylation and prognostic factors or survival was observed.

CONCLUSIONS

Our results suggest that epigenetic inactivation of RASSF1A may contribute to the clinically aggressive phenotype of high-risk NB.

Neuroblastoma angiogenesis is inhibited with a folded synthetic molecule corresponding to the epidermal growth factor-like module of the follistatin domain of SPARC

Secreted protein acidic and rich in cysteine (SPARC) is a multifunctional matricellular glycoprotein. In vitro, SPARC inhibits the proliferation and migration of endothelial cells stimulated by growth factors and induces endothelial cell apoptosis. We previously showed that SPARC also inhibits angiogenesis in vivo and impairs the growth of the pediatric tumor neuroblastoma (NB). SPARC comprises three domains that are independently folded by a complex pattern of disulfide bonds and have a high degree of structural conservation. In this study, separate modules of the SPARC domains were synthesized as cysteine-linked peptides and tested for their ability to inhibit angiogenesis. Peptide FS-E, representing the epidermal growth factor (EGF)-like module of the follistatin (FS) domain, did not cause endothelial cell apoptosis but strongly inhibited basic fibroblast growth factor (bFGF)-induced endothelial cell migration with an ED(50) = 10 pmol/L. In vivo, peptide FS-E blocked bFGF-stimulated angiogenesis and neovascularization induced by NB cells. The EGF-like conformation was essential for peptide FS-E function because reduction of its two disulfide bonds completely abrogated peptide activity. Peptides FS-K and EC-N, corresponding to part of the Kazal module of the FS domain and the conserved alpha-helix in the extracellular calcium-binding domain, respectively, had minimal to no inhibitory activity. Our data show that the EGF-like module of the SPARC FS domain is angiosuppressive, and its structural conformation is critical for antiangiogenic activity.

Scintigraphic response by 123I-metaiodobenzylguanidine scan correlates with event-free survival in high-risk neuroblastoma

PURPOSE

To investigate whether response to induction therapy, evaluated by metaiodobenzylguanadine (MIBG) and bone scintigraphy, correlates with event-free survival (EFS) in children with high-risk neuroblastoma (NB).

PATIENTS AND METHODS

Twenty-nine high-risk NB patients were treated prospectively with an intensive induction regimen and consolidated with three cycles of high-dose therapy with peripheral blood stem-cell rescue. The scintigraphic response was evaluated by MIBG and bone scans using a semi-quantitative scoring system. The prognostic significance of the imaging scores at diagnosis and following induction therapy was evaluated.

RESULTS

A trend associating worse 4-year EFS rates for patients with versus without osteomedullary uptake on MIBG scintigraphs at diagnosis was seen (35% +/- 11% v 80% +/- 18%, respectively; P =.13). Similarly, patients with positive bone scans at diagnosis had worse EFS than those with negative scans, although the difference did not receive statistical significance (34% +/- 10% v 83% +/- 15%, respectively; P =.06). However, significantly worse EFS was observed in patients with a postinduction MIBG score of >/= 3 compared to those with scores of less than 3 (0% v 58% +/- 11%; P =.002). There was no correlation between bone scan scores and outcome following induction therapy.

CONCLUSION

MIBG scores >/= 3 following induction therapy identifies a subset of NB patients who are likely to relapse following three cycles of high-dose therapy with peripheral blood stem-cell rescue, local radiotherapy, and 13-cis-retinoic acid. Alternative therapeutic strategies should be considered for patients with a poor response to induction therapy.

Treatment of Relapsed Wilms’ Tumor With High-Dose Therapy and Autologous Hematopoietic Stem-Cell Rescue: The Experience at Children’s Memorial Hospital

Purpose

To investigate whether high-dose therapy with hematopoietic stem-cell rescue (HSCR) will improve survival for patients with relapsed Wilms’ tumor.

Patients and Methods

Thirteen children with relapsed Wilms’ tumor were treated with one or two cycles of high-dose chemotherapy (HDT) followed by autologous HSCR. Twelve of 13 patients received reinduction chemotherapy before HDT and HSCR. The median age at diagnosis was 4.8 years, and the median time to relapse was 12 months. The histology was favorable in 12 of 13 patients. The ablative regimens included: (1) thiotepa (TT)/cyclophosphamide (CTX)/carboplatin (CP; n = 2); (2) TT/CTX (n = 5); (3) TT/etoposide (ETP; n = 1); and (4) CP/ETP/CTX (n = 1). Four patients received two cycles of HDT and HSCR. Cycle 1 consisted of CP/ETP/CTX, and melphalan/CTX were used in cycle 2.

Results

Seven of 13 patients are alive without evidence of disease, with a median follow-up of 30 months. The 4-year estimated event-free survival (EFS) rate is 60% (95% CI, 0.40 to 6.88), and the overall survival (OS) at 4 years is 73% (95% CI, 0.40 to 6.86). There was no transplant-related mortality. All patients engrafted to an absolute neutrophil count 500/μL at a median of 13 days (range, 8 to 62 days) and had an unsustained platelet count > 20.0μ at a median of 16 days (range, 10 to 202 days).

Conclusion

Our results suggest that HDT with HSCR is an effective treatment for patients with Wilms’ tumor who experience relapse.

Methylation-Associated Silencing of theHeat Shock Protein 47Gene in Human Neuroblastoma

Hypermethylation of gene promoter CpG islands is a frequent mechanism for gene inactivation in a variety of human cancers, including neuroblastoma (NB). We demonstrated recently that treatment with the demethylating agent 5'-aza-2'-deoxycytidine (5-Aza-dC) significantly inhibited NB growth in vivo. In an effort to identify the genes and biological pathways that are responsible for the impaired NB tumor growth observed after treatment with 5-Aza-dC, we performed genome-wide gene expression analysis of control and treated NBL-W-S NB cells. We found >or=3-fold changes in expression of 44 genes that play roles in angiogenesis, apoptosis, cell adhesion, transcriptional regulation, and signal transduction. The gene encoding heat shock protein 47 (Hsp47), a collagen-specific molecular chaperon, was up-regulated >80-fold after 5-Aza-dC treatment. Expression studies confirmed that Hsp47 is silenced in a subset of NB cell lines and tumors. We also show that silencing of Hsp47 in NB cells is associated with aberrant methylation of promoter CpG islands and that Hsp47 expression can be restored after treatment with 5-Aza-dC. A strong correlation between Hsp47 and collagen type I and IV expression was seen in NB cells. Interestingly, tumorigenicity was inversely correlated with the level of collagen expression in NB cell lines, and higher levels of collagen were detected in mature NB tumors that are associated with favorable outcome compared with undifferentiated, advanced-stage NBs. Our studies support a role for Hsp47 in the regulation of collagen type I and IV production in NB cells and suggest that the level of collagen expression may influence NB tumor phenotype.

MYCN-mediated regulation of the MRP1 promoter in human neuroblastoma

In the childhood cancer neuroblastoma (NB), the level of expression of the multidrug resistance-associated protein (MRP1) gene is strongly correlated with expression of the MYCN oncogene in primary NB tumors, suggesting that MRP1 may be a target for MYCN-mediated gene regulation. In this study, we show that MYCN induction in human NB cells results in increased MRP1 mRNA and protein levels, which in turn is accompanied by increased drug resistance and enhanced MRP1-mediated drug efflux. Furthermore, luciferase activity from MRP1 promoter/luciferase gene reporter constructs was significantly increased in NB cells with exogenous overexpression of MYCN, whereas activity was decreased in NB cells stably transfected with MYCN-antisense vectors. Decreased luciferase activity was observed with promoter constructs that lacked one or two E-box sequences or had E-box double point mutations, while a truncated MRP1 promoter lacking all three E-boxes exhibited only basal levels of activity. Specific electrophoretic mobility shifts of MRP1 E-box sequences were detected with nuclear extracts from NB cells with MYCN overexpression, and complex formation was inhibited with the addition of antibodies directed against MYCN or MYC. These findings indicate that by interacting with E-box elements within the promoter, MYCN can upregulate MRP1 expression and modulate drug resistance in NB.

Methylation-associated silencing of the thrombospondin-1 gene in human neuroblastoma

Tumor angiogenesis, a major requirement for tumor outgrowth and metastasis, is regulated by pro- and antiangiogenic factors. Methylation-associated inactivation of the angiogenesis inhibitor thrombospondin-1 (TSP-1) has been observed recently in some adult tumors. To investigate the role of TSP-1 in pediatric cancer, we examined its pattern of expression and mechanisms of regulation in neuroblastoma (NB). TSP-1 was silenced in a subset of undifferentiated, advanced-stage tumors and NB cell lines. In contrast, most localized tumors expressed this angiogenesis inhibitor, and a significant correlation between morphological evidence of neuroblast differentiation and TSP-1 expression was observed. Luciferase assays demonstrated the presence of nuclear factors required for TSP-1 transcription in both TSP-1-positive and -negative cell lines, but no correlation between TSP-1 promoter activity and the level of TSP-1 mRNA expression was seen. Our studies indicate that the transcriptional silencing of TSP-1 was caused by methylation. TSP-1 promoter methylation was detected in all of the NB cell lines lacking TSP-1 mRNA and in 37% of the NB clinical tumors analyzed. Furthermore, treatment with the demethylating agent, 5-Aza-2'-deoxycytidine (5-Aza-dC), restored TSP-1 expression in NB cell lines. Disrupting methylation with 5-Aza-dC also led to significant inhibition of NB in vivo and re-expression of TSP-1 in a subset of NB xenografts. These results suggest that 5-Aza-dC inhibits NB growth by augmenting the expression of TSP-1 along with other genes that suppress tumor growth. Demethylating agents may prove to be effective candidates for the treatment of children with NB.

Advances in the diagnosis and treatment of neuroblastoma

Neuroblastoma, a childhood neoplasm arising from neural crest cells, is characterized by a diversity of clinical behavior ranging from spontaneous remission to rapid tumor progression and death. To a large extent, outcome can be predicted by the stage of disease and the age at diagnosis. However, the molecular events responsible for the variability in response to treatment and the rate of tumor growth remain largely unknown. Over the past decade, transformation-linked genetic changes have been identified in neuroblastoma tumors that have contributed to the understanding of tumor predisposition, metastasis, treatment responsiveness, and prognosis. The Children's Oncology Group recently developed a Neuroblastoma Risk Stratification System that is currently in use for treatment stratification purposes, based on clinical and biologic factors that are strongly predictive of outcome. This review discusses the current risk-based treatment approaches for children with neuroblastoma and recent advances in biologic therapy.

The regulation of angiogenesis in neuroblastoma

Angiogenesis is required for the growth and metastasis of malignant tumors, and high vascular density has been correlated with aggressive tumor growth in many types of cancer. This process is regulated by the local balance of stimulatory and inhibitory molecules produced by tumor cells, stromal cells, and the organ-specific environment. In neuroblastoma, a pediatric malignancy that is characterized by a broad spectrum of clinical behavior, angiogenesis also appears to play an important role in determining tumor phenotype. The nature of the angiogenic balance in neuroblastoma is complex, and a spectrum of angiogenesis stimulators and inhibitors has been detected in neuroblastoma tumors. This review summarizes our current understanding of the regulation of angiogenesis in neuroblastoma.

SPARC is a key Schwannian-derived inhibitor controlling neuroblastoma tumor angiogenesis

Neuroblastoma (NB), a common pediatric neoplasm, consists of two main cell populations: neuroblastic/ganglionic cells and Schwann cells. NB tumors with abundant Schwannian stroma display a more benign clinical behavior than stroma-poor tumors. Recent studies suggest that Schwann cells influence NB tumor growth via secreted factors that induce differentiation, suppress proliferation, and inhibit angiogenesis. Two angiogenesis inhibitors, pigment epithelium-derived factor and tissue inhibitor of metalloproteinase-2, have been detected in Schwann cell secretions. Here, we isolated another Schwann cell-derived secreted inhibitor of angiogenesis, a 43-kDa protein identified as SPARC (secreted protein acidic and rich in cysteine), an extracellular matrix protein. We found SPARC to be critical for the antiangiogenic phenotype of cultured Schwann cells. We also show that purified SPARC potently inhibits angiogenesis and significantly impairs NB tumor growth in vivo. SPARC may be an effective candidate for the treatment of children with clinically aggressive, Schwannian stroma-poor NB tumors.

Treatment of high-risk neuroblastoma with triple-tandem high-dose therapy and stem-cell rescue: results of the Chicago Pilot II Study

PURPOSE

To investigate whether intensive induction therapy followed by triple-tandem cycles of high-dose therapy with peripheral-blood stem-cell rescue and local irradiation will improve event-free survival for patients with high-risk neuroblastoma.

PATIENTS AND METHODS

From August 1995 to January 2000, 25 consecutive newly diagnosed high-risk neuroblastoma patients and one child with recurrent MYCN-amplified disease were enrolled onto the Chicago Pilot II Protocol. After induction therapy and surgery, peripheral-blood stem cells were mobilized with three cycles of high-dose cyclophosphamide and granulocyte colony-stimulating factor. Patients then underwent triple-tandem cycles of high-dose therapy with peripheral-blood stem-cell rescue followed by radiation to the primary site.

RESULTS

Twenty-two of the 26 patients successfully completed induction therapy and were eligible for the triple-tandem consolidation high-dose therapy. Sufficient numbers of peripheral-blood stem cells were collected in all but one patient. Seventeen patients were able to complete all three cycles of high-dose therapy and peripheral-blood stem-cell rescue, two patients completed two cycles, and three patients completed one cycle. There was one toxic death, and one patient died from complications of treatment for graft failure. With a median follow-up of 38 months, the 3-year event-free survival and survival rates are 57% +/- 11% and 79% +/- 10%, respectively.

CONCLUSION

The results of this pilot study demonstrate that it is feasible to intensify consolidation with triple-tandem high-dose chemotherapy and peripheral-blood stem-cell rescue and local irradiation, and suggest that this treatment strategy may lead to improved survival for patients with high-risk neuroblastoma.

HuD, a neuronal-specific RNA-binding protein, increases the in vivo stability of MYCN RNA

MYCN amplification and consequent deregulated expression plays a crucial role in determining the clinical behavior of neuroblastoma. Enhanced expression of MYCN confers growth potential to neuroblastoma cells, and a direct link between MYCN expression and the development of neuroblastoma has been demonstrated in transgenic mice studies. Although the molecular pathways underlying the regulation of MYCN have not been fully elucidated, post-transcriptional mechanisms appear to be important. Previously, we reported that an embryonic lethal abnormal vision-like (ELAV) protein binds with high specificity to at least two AU-rich elements within the MYCN 3'-untranslated region. In this study, we characterized the ability of cis-acting elements within the MYCN 3'-untranslated region to destabilize mRNA in cells and examined the functional consequences of its interactions with the ELAV protein HuD. We show that at least 4 cis-acting elements within the MYCN 3'-untranslated region are able to signal the degradation of stable heterologous mRNA. Ectopic overexpression of HuD dramatically inhibits RNA decay mediated by the full-length MYCN 3'-untranslated region and cis-acting destabilizing elements that harbor HuD binding sites in vivo. HuD may contribute to the malignant phenotype of neuroblastoma cells by stabilizing MYCN mRNA, thereby enhancing steady-state levels of expression of this oncogene.

p16/p14(ARF) cell cycle regulatory pathways in primary neuroblastoma: p16 expression is associated with advanced stage disease

p16 regulates the G(1)-S cell cycle transition by inhibiting the cyclin D-cyclin-dependent kinase (CDK)4/CDK6-mediated phosphorylation of retinoblastoma protein (pRb). We examined the possible derangement of the p16-CDK/cyclin D-pRb pathway in 40 primary neuroblastomas including 18 samples in the unfavorable stages (C and D) and 22 in the favorable stages (A, B, and Ds) by PCR, reverse transcription-PCR, Western blot, and immunohistochemistry and correlated the results with clinical outcome. No samples harbored alterations of the p16 gene. Interestingly, the samples in the unfavorable stages exhibited expression of p16 mRNA and protein more frequently than those in the favorable stages [mRNA, 9 of 18 (50%) versus 2 of 22 (9%), P = 0.006; protein, 5 of 16 (31%) versus 0 of 18 (0%), P = 0.013]. Alterations of the downstream components of the pathway were infrequent. pRb was deregulated in the majority of samples investigated [27 of 33 (82%), 24 with hyperphosphorylated pRb and 3 with no pRb protein]. The phosphorylation status of pRb did not correlate with p16 protein expression, suggesting that the elevated p16 protein may not be functioning properly to regulate the pathway. Among patients of all stages, p16 expression was significantly associated with a lower overall survival. There was no overexpression of MDM2, and loss of p14(ARF) expression and p53 mutation were infrequent events. Taken together, these findings suggest that up-regulated p16 expression may represent a unique feature of aggressive neuroblastoma.

Antiangiogenic therapy inhibits human neuroblastoma growth

BACKGROUND

Angiogenesis plays a crucial role in the progression and metastasis of malignant solid tumors. In many types of cancer, including neuroblastoma, high tumor vascularity correlates with poor outcome. Recently, a number of angiogenic inhibitors have been identified that had antitumor activity in preclinical studies.

PROCEDURE

To investigate the effect of the antiangiogenic agent TNP-470 on neuroblastoma tumor growth, we treated nude mice with TNP-470 after they were inoculated subcutaneously with 5 x 10(6) cells from the MYCN-amplified, human neuroblastoma cell line NBL-W-N.

RESULTS

TNP-470 did not significantly affect tumor growth when it was administered to mice with large tumors (>600 mm3). However, when TNP-470 was administered in the setting of microscopic disease 12 hr following tumor cell inoculation, treated mice had a significantly improved tumor-free survival at 12 weeks (P < 0.001), and overall survival at 45 weeks (P < 0.001), compared to control animals.

CONCLUSIONS

Our studies suggest that TNP-470 treatment may be most effective if it is administered in the setting of microscopic disease. We speculate that TNP-470 may inhibit neuroblastoma growth in children if treatment is initiated following intensive multimodality therapy, when residual disease is minimal.

Natural killer cell lymphoma: report of two pediatric cases, therapeutic options, and review of the literature

BACKGROUND

Natural killer (NK) cell lymphomas are rapidly fatal malignancies that to the authors' knowledge are rare in children. In the current study, the authors report the cases of two boys with NK cell lymphomas with refractory disease who both were salvaged with high dose chemotherapy and stem cell transplantation and compare these patients with those in the published experience.

METHODS

A comprehensive literature review was performed to identify other cases of pediatric patients with NK cell lymphomas, their treatment, and outcome.

RESULTS

One of the patients in the current study developed two recurrences and the other patient experienced early disease progression during front-line treatment. Both then were treated with high dose chemotherapy followed by stem cell rescue. At last follow-up, the patients remained free of disease at 15 months and 16 months, respectively, after transplantation (48 months and 22 months, respectively, from the time of diagnosis). In addition to the 2 patients in the current study, the authors found 13 pediatric patients reported in the literature to date. Of the 7 patients with localized (Stage I-II) disease, 5 patients (71%) were reported to be alive 1-107 months after diagnosis. Of the 6 patients with Stage IV disease, only the 2 patients who received high dose chemotherapy and stem cell rescue (33%) were alive at the time of last follow-up (at 30 months and 12 months, respectively). Including the patients reported in the current study, 9 of 15 children with NK cell lymphoma (all stages) (60%) were reported to be alive at the time of last follow-up.

CONCLUSIONS

Although pediatric NK cell lymphomas rapidly can become fatal, it appears that high dose chemotherapy followed by stem cell transplantation is effective therapy, especially in patients with advanced or resistant disease. Further follow-up is needed to determine whether this treatment approach will be curative.

Detection of MYCN gene amplification in neuroblastoma by fluorescence in situ hybridization: a pediatric oncology group study

To assess the utility of fluorescence in situ hybridization (FISH) for analysis of MYCN gene amplification in neuroblastoma, we compared this assay with Southern blot analysis using tumor specimens collected from 232 patients with presenting characteristics typical of this disease. The FISH technique identified MYCN amplification in 47 cases, compared with 39 by Southern blotting, thus increasing the total number of positive cases by 21%. The major cause of discordancy was a low fraction of tumor cells (< or =30% replacement) in clinical specimens, which prevented an accurate estimate of MYCN copy number by Southern blotting. With FISH, by contrast, it was possible to analyze multiple interphase nuclei of tumor cells, regardless of the proportion of normal peripheral blood, bone marrow, or stromal cells in clinical samples. Thus, FISH could be performed accurately with very small numbers of tumor cells from touch preparations of needle biopsies. Moreover, this procedure allowed us to discern the heterogeneous pattern of MYCN amplification that is characteristic of neuroblastoma. We conclude that FISH improves the detection of MYCN gene amplification in childhood neuroblastomas in a clinical setting, thus facilitating therapeutic decisions based on the presence or absence of this prognostically important biologic marker.

Treatment and outcome of 83 children with intraspinal neuroblastoma: the Pediatric Oncology Group experience

PURPOSE

To investigate whether the rate of neurologic recovery or the incidence of long-term sequelae differed for children with neuroblastoma (NB) initially treated with chemotherapy versus surgical decompression with laminectomy, we reviewed the Pediatric Oncology Group (POG) experience.

PATIENTS AND METHODS

A retrospective review of children diagnosed with intraspinal NB registered on POG NB Biology Protocol 9047 was performed. Survival, neurologic outcome, and orthopedic sequelae were evaluated according to age of the patient at diagnosis, stage of disease, duration and severity of neurologic symptoms, and therapeutic intervention.

RESULTS

Between May 1990 and January 1998, 83 children with intraspinal NB were entered onto the study. Five-year survival for this cohort of patients was 71% +/- 9%. Forty-three (52%) of the patients had neurologic symptoms at diagnosis. After treatment, six of 15 severely affected patients, who presented with paralysis, completely recovered neurologic function. Two of five patients with moderate deficits, consisting of paresis and bowel/bladder dysfunction, completely recovered neurologic function. Seventeen of 22 assessable children, who had mild symptoms comprised of paresis alone, fully recovered. Seven of 24 assessable patients who had undergone laminectomy developed scoliosis, whereas spinal deformities were only detected in one of 49 assessable patients managed without laminectomy (P =.001).

CONCLUSION

The frequency of complete neurologic recovery in children with intraspinal NB inversely correlated with the severity of the presenting neurologic deficits. The rate of neurologic recovery was similar for patients treated with chemotherapy compared to those managed with laminectomy. Fewer orthopedic sequelae were observed in the children managed with chemotherapy than were seen in children managed with laminectomy.

Natural killer cell lymphoma: report of two pediatric cases, therapeutic options, and review of the literature

BACKGROUND

Natural killer (NK) cell lymphomas are rapidly fatal malignancies that to the authors' knowledge are rare in children. In the current study, the authors report the cases of two boys with NK cell lymphomas with refractory disease who both were salvaged with high dose chemotherapy and stem cell transplantation and compare these patients with those in the published experience.

METHODS

A comprehensive literature review was performed to identify other cases of pediatric patients with NK cell lymphomas, their treatment, and outcome.

RESULTS

One of the patients in the current study developed two recurrences and the other patient experienced early disease progression during front-line treatment. Both then were treated with high dose chemotherapy followed by stem cell rescue. At last follow-up, the patients remained free of disease at 15 months and 16 months, respectively, after transplantation (48 months and 22 months, respectively, from the time of diagnosis). In addition to the 2 patients in the current study, the authors found 13 pediatric patients reported in the literature to date. Of the 7 patients with localized (Stage I-II) disease, 5 patients (71%) were reported to be alive 1-107 months after diagnosis. Of the 6 patients with Stage IV disease, only the 2 patients who received high dose chemotherapy and stem cell rescue (33%) were alive at the time of last follow-up (at 30 months and 12 months, respectively). Including the patients reported in the current study, 9 of 15 children with NK cell lymphoma (all stages) (60%) were reported to be alive at the time of last follow-up.

CONCLUSIONS

Although pediatric NK cell lymphomas rapidly can become fatal, it appears that high dose chemotherapy followed by stem cell transplantation is effective therapy, especially in patients with advanced or resistant disease. Further follow-up is needed to determine whether this treatment approach will be curative.

Expression of the putative tumour suppressor gene, p73, in neuroblastoma and other childhood tumours

BACKGROUND

The recently characterised p53 homologue, p73, has been mapped to chromosome 1p36, a region often found deleted in neuroblastoma. Although p73 has been implicated as a candidate tumour suppressor for neuroblastoma, mutations in the gene appear to be rare, thus suggesting other mechanisms for its aberrant behaviour.

PROCEDURE

We analysed p73 gene expression in a panel of primary neuroblastoma tumours and cell lines, as well as other tumours of childhood, using a reverse transcriptase-polymerase chain reaction assay.

RESULTS

Although low-level p73 expression was detected in 44/45 primary neuroblastoma tumours, no association with prognostic markers could be discerned. In no case was the level of p73 expression in the primary tumours as high as that observed in p73-expressing neuroblastoma cell lines. Expression of the p73 gene was also detected in 24/34 other childhood tumours.

CONCLUSION

Collectively, the data raise doubts over the role of this gene as a tumour suppressor in neuroblastoma.

Antiangiogenic therapy inhibits human neuroblastoma growth

BACKGROUND

Angiogenesis plays a crucial role in the progression and metastasis of malignant solid tumors. In many types of cancer, including neuroblastoma, high tumor vascularity correlates with poor outcome. Recently, a number of angiogenic inhibitors have been identified that had antitumor activity in preclinical studies.

PROCEDURE

To investigate the effect of the antiangiogenic agent TNP-470 on neuroblastoma tumor growth, we treated nude mice with TNP-470 after they were inoculated subcutaneously with 5 x 10(6) cells from the MYCN-amplified, human neuroblastoma cell line NBL-W-N.

RESULTS

TNP-470 did not significantly affect tumor growth when it was administered to mice with large tumors (>600 mm3). However, when TNP-470 was administered in the setting of microscopic disease 12 hr following tumor cell inoculation, treated mice had a significantly improved tumor-free survival at 12 weeks (P < 0.001), and overall survival at 45 weeks (P < 0.001), compared to control animals.

CONCLUSIONS

Our studies suggest that TNP-470 treatment may be most effective if it is administered in the setting of microscopic disease. We speculate that TNP-470 may inhibit neuroblastoma growth in children if treatment is initiated following intensive multimodality therapy, when residual disease is minimal.

Residential pesticide exposure and neuroblastoma

Neuroblastoma is the most common neoplasm in children under 1 year of age. We examined the relation between residential exposure to pesticides and neuroblastoma, using data from a case-control study of risk factors for neuroblastoma. Incident cases of neuroblastoma (N = 538) were identified through the Pediatric Oncology Group and the Children's Cancer Group. One age-matched control was identified for each case by random digit dialing. Telephone interviews with each parent collected information on residential exposure to pesticides. Pesticide use in both the home and garden were modestly associated with neuroblastoma [odds ratio (OR) = 1.6 (95% confidence interval [95% CI] = 1.0-2.3, and OR = 1.7 (95% CI = 0.9-2.1), respectively]. Compared with infants [OR = 1.0 (95% CI = 0.6-2.0)], stronger associations were found for garden pesticides in children diagnosed after 1 year of age [OR = 2.2 (95% CI = 1.3-3.6)], which suggests that pesticides may act through a mechanism more common for neuroblastomas in older children. There was no evidence of differential pesticide effects in subgroups of neuroblastoma defined by MYCN oncogene amplification or tumor stage.

Prognostic significance of EPHB6, EFNB2, and EFNB3 expressions in neuroblastoma

BACKGROUND

EPH family receptor tyrosine kinases and their ligand ephrins play pivotal roles in development. High-level expression of transcripts encoding EPHB6 receptors (EPHB6), its ligands ephrin-B2 and ephrin-B3 (EFNB2, EFNB3) is predictive of favorable disease outcome of neuroblastoma (NB). When combined with TrkA expression, the expression of EPHB6, EFNB2, or EFNB3 predicts more accurately the disease outcome than each of the four variables alone.

PROCEDURE

Cox regression and Kaplan-Meier analyses were used to assess the prognostic significance of EPHB6, EFNB2, EFNB3, and TrkA expressions in NB without MYCN amplification.

RESULTS

High-level expression of EFNB3 or TrkA predicted favorable NB outcome of NB without MYCN amplification (p < 0.03). As found in the general NB population, EPHB6, EFNB2, or EFNB3 expression in combination with TrkA expression was significantly predictive of the disease outcome of normal MYCN NB (p < 0.01).

CONCLUSIONS

EPHB6, EFNB2, and EFNB3 expressions may permit further refinement of the prognostic stratification of NB into favorable and unfavorable groups.