CSF1R inhibition depletes tumor-associated macrophages and attenuates tumor progression in a mouse sonic Hedgehog-Medulloblastoma model.

The immune microenvironment of tumors can play a critical role in promoting or inhibiting tumor progression depending on the context. We present evidence that tumor-associated macrophages/microglia (TAMs) can promote tumor progression in the sonic hedgehog subgroup of medulloblastoma (SHH-MB). By combining longitudinal manganese-enhanced magnetic resonance imaging (MEMRI) and immune profiling of a sporadic mouse model of SHH-MB, we found the density of TAMs is higher in the ~50% of tumors that progress to lethal disease. Furthermore, reducing regulatory T cells or eliminating B and T cells in Rag1 mutants does not alter SHH-MB tumor progression. As TAMs are a dominant immune component in tumors and are normally dependent on colony-stimulating factor 1 receptor (CSF1R), we treated mice with a CSF1R inhibitor, PLX5622. Significantly, PLX5622 reduces a subset of TAMs, prolongs mouse survival, and reduces the volume of most tumors within 4 weeks of treatment. Moreover, concomitant with a reduction in TAMs the percentage of infiltrating cytotoxic T cells is increased, indicating a change in the tumor environment. Our studies in an immunocompetent preclinical mouse model demonstrate TAMs can have a functional role in promoting SHH-MB progression. Thus, CSF1R inhibition could have therapeutic potential for a subset of SHH-MB patients.

Monitoring of intracerebellarly-administered natural killer cells with fluorine-19 MRI.

PURPOSE: Medulloblastoma (MB) is the most common malignant brain tumor in children. Recent studies have shown the ability of natural killer (NK) cells to lyse MB cell lines in vitro, but in vivo successes remain elusive and the efficacy and fate of NK cells in vivo remain unknown. METHODS: To address these questions, we injected MB cells into the cerebellum of immunodeficient mice and examined tumor growth at various days after tumor establishment via bioluminescence imaging. NK cells were labeled with a fluorine-19 (19F) MRI probe and subsequently injected either intratumorally or contralaterally to the tumor in the cerebellum and effect on tumor growth was monitored. RESULTS: The 19F probe efficiently labeled the NK cells and exhibited little cytotoxicity. Fluorine-19 MRI confirmed the successful and accurate delivery of the labeled NK cells to the cerebellum of the mice. Administration of 19F-labeled NK cells suppressed MB growth, with the same efficacy as unlabeled cells. Immunohistochemistry confirmed the presence of NK cells within the tumor, which was associated with induction of apoptosis in tumor cells. NK cell migration to the tumor from a distal location as well as activation of apoptosis was also demonstrated by immunohstochemistry. CONCLUSIONS: Our results show that NK cells present a novel opportunity for new strategies in MB treatment. Further, 19F-labeled NK cells can suppress MB growth while enabling 19F MRI to provide imaging feedback that can facilitate study and optimization of therapeutic paradigms.

Reprogramming Medulloblastoma-Propagating Cells by a Combined Antagonism of Sonic Hedgehog and CXCR4.

The CXCR4 chemokine and Sonic Hedgehog (SHH) morphogen pathways are well-validated therapeutic targets in cancer, including medulloblastoma. However, single-agent treatments with SHH or CXCR4 antagonists have not proven efficacious in clinical trials to date. Here, we discovered that dual inhibition of the SHH and CXCR4 pathways in a murine model of SHH-subtype medulloblastoma exerts potent antitumor effects. This therapeutic synergy resulted in the suppression of tumor-propagating cell function and correlated with increased histone H3 lysine 27 trimethylation within the promoters of stem cell genes, resulting in their decreased expression. These results demonstrate that CXCR4 contributes to the epigenetic regulation of a tumor-propagating cell phenotype. Moreover, they provide a mechanistic rationale to evaluate the combination of SHH and CXCR4 inhibitors in clinical trials for the treatment of medulloblastoma, as well as other cancers driven by SHH that coexpress high levels of CXCR4. Cancer Res; 77(6); 1416-26. ©2016 AACR.

Inhibition of BRD4 attenuates tumor cell self-renewal and suppresses stem cell signaling in MYC driven medulloblastoma.

Medulloblastoma is a pediatric brain tumor with a variable prognosis due to clinical and genomic heterogeneity. Among the 4 major genomic sub-groups, patients with MYC amplified tumors have a particularly poor prognosis despite therapy with surgery, radiation and chemotherapy. Targeting the MYC oncogene has traditionally been problematic. Here we report that MYC driven medulloblastoma can be targeted by inhibition of the bromodomain protein BRD4. We show that bromodomain inhibition with JQ1 restricts c-MYC driven transcriptional programs in medulloblastoma, suppresses medulloblastoma cell growth and induces a cell cycle arrest. Importantly JQ1 suppresses stem cell associated signaling in medulloblastoma cells and inhibits medulloblastoma tumor cell self-renewal. Additionally JQ1 also promotes senescence in medulloblastoma cells by activating cell cycle kinase inhibitors and inhibiting activity of E2F1. Furthermore BRD4 inhibition displayed an anti-proliferative, pro-senescence effect in a medulloblastoma model in vivo. In clinical samples we found that transcriptional programs suppressed by JQ1 are associated with adverse risk in medulloblastoma patients. Our work indicates that BRD4 inhibition attenuates stem cell signaling in MYC driven medulloblastoma and demonstrates the feasibility BET domain inhibition as a therapeutic approach in vivo.

Long-term outcomes and role of chemotherapy in adults with newly diagnosed medulloblastoma.

OBJECTIVE: To assess the survival and role of adjuvant chemotherapy in adult medulloblastoma. METHODS: We reviewed outcomes of 66 patients (aged 18 y or more; median age, 33 y) with medulloblastoma. Forty-four (67%) patients had M0 disease, 9 had M1-M4, and 13 had MX. Thirty-one patients each for whom risk stratification was available were classified as high risk or standard risk. Fifty-six patients had histologic results: classic histology was the most common (n=46 [84%]), followed by desmoplastic (n=9), and large cell/anaplastic (n=1). Overall survival (OS) and progression-free survival (PFS) were estimated with Kaplan-Meier curves and log-rank tests. Cox regression analysis was used to compare recurrences. RESULTS: Median follow-up was 6.7 years. The estimated 5-year OS and PFS were 74% and 59%, respectively. High-risk versus standard-risk classification was associated with worse OS (61% vs. 86%; P=0.03) and recurrence (hazard ratio, 2.56; P=0.05) and a trend for worse PFS (49% vs. 69%; P=0.13). Gross total resection was associated with improved OS (P=0.03) and a trend toward improved PFS (P=0.09). No chemotherapy benefit could be demonstrated for the group as a whole. For high-risk patients with classic histology (n=25), chemotherapy was associated with a trend for improvement in 5-year PFS from 36% to 71% (P=0.10) and in 5-year OS from 49% to 100% (P=0.08). CONCLUSIONS: In adult patients with medulloblastoma, the extent of resection and risk classification predicts the outcome. These results suggest a chemotherapy benefit for high-risk patients with classic histology.

Optimizing the radiation therapy dose prescription for pediatric medulloblastoma: minimizing the life years lost attributable to failure to control the disease and late complication risk.

BACKGROUND: A mathematical framework is presented for simultaneously quantifying and evaluating the trade-off between tumor control and late complications for risk-based radiation therapy (RT) decision-support. To demonstrate this, we estimate life years lost (LYL) attributable to tumor recurrence, late cardiac toxicity and secondary cancers for standard-risk pediatric medulloblastoma (MB) patients and compare the effect of dose re-distribution on a common scale. METHODS: Total LYL were derived, based on the LYL attributable to radiation-induced late complications and the LYL from not controlling the primary disease. We compared the estimated LYL for three different treatments in 10 patients: 1) standard 3D conformal RT; 2) proton therapy; 3) risk-adaptive photon treatment lowering the dose to part of the craniospinal (CS) target volume situated close to critical risk organs. RESULTS: Late toxicity is important, with 0.75 LYL (95% CI 0.60-7.2 years) for standard uniform 24 Gy CS irradiation. However, recurrence risk dominates the total LYL with 14.2 years (95% CI 13.4-16.6 years). Compared to standard treatment, a risk-adapted strategy prescribing 12 Gy to the spinal volume encompassing the 1st-10th thoracic vertebrae (Th1-Th10), and 36 Gy to the remaining CS volume, estimated a LYL reduction of 0.90 years (95% CI -0.18-2.41 years). Proton therapy with 36 Gy to the whole CS volume was associated with significantly fewer LYL compared to the risk-adapted photon strategies, with a mean LYL difference of 0.50 years (95% CI 0.25-2.60 years). CONCLUSIONS: Optimization of RT prescription strategies considering both late complications and the risk of recurrence, an all-cause mortality dose painting approach, was demonstrated. The risk-adapted techniques compared favorably to the standard, and although in this context, the gain is small compared to estimated uncertainty, this study demonstrates a framework for all-cause mortality risk estimation, rather than evaluates direct clinical applicability of risk-adapted strategies.

Expression of miR-124 inhibits growth of medulloblastoma cells.

Medulloblastoma is the most common malignant brain tumor in children, and a substantial number of patients die as a result of tumor progression. Overexpression of CDK6 is present in approximately one-third of medulloblastomas and is an independent poor prognostic marker for this disease. MicroRNA (miR)-124 inhibits expression of CDK6 and prevents proliferation of glioblastoma and medulloblastoma cells in vitro. We examined the effects of miR-124 overexpression on medulloblastoma cells both in vitro and in vivo and compared cell lines that have low and high CDK6 expression. MiR-124 overexpression inhibits the proliferation of medulloblastoma cells, and this effect is mediated mostly through the action of miR-124 upon CDK6. We further show that induced expression of miR-124 potently inhibits growth of medulloblastoma xenograft tumors in rodents. Further testing of miR-124 will help define the ultimate therapeutic potential of preclinical models of medulloblastoma in conjunction with various delivery strategies for treatment.

Pharmacological activation of the p53 pathway by nutlin-3 exerts anti-tumoral effects in medulloblastomas.

Medulloblastomas account for 20% of pediatric brain tumors. With an overall survival of 40%-70%, their treatment is still a challenge. The majority of medulloblastomas lack p53 mutations, but even in cancers retaining wild-type p53, the tumor surveillance function of p53 is inhibited by the oncoprotein MDM2. Deregulation of the MDM2/p53 balance leads to malignant transformation. Here, we analyzed MDM2 mRNA and protein expression in primary medulloblastomas and normal cerebellum and assessed the mutational status of p53 and MDM2 expression in 6 medulloblastoma cell lines. MDM2 expression was elevated in medulloblastomas, compared with cerebellum. Four of 6 medulloblastoma cell lines expressed wild-type p53 and high levels of MDM2. The tumor-promoting p53-MDM2 interaction can be inhibited by the small molecule, nutlin-3, restoring p53 function. Targeting the p53-MDM2 axis using nutlin-3 significantly reduced cell viability and induced either cell cycle arrest or apoptosis and expression of the p53 target gene p21 in these 4 cell lines. In contrast, DAOY and UW-228 cells harboring TP53 mutations were almost unaffected by nutlin-3 treatment. MDM2 knockdown in medulloblastoma cells by siRNA mimicked nutlin-3 treatment, whereas expression of dominant negative p53 abrogated nutlin-3 effects. Oral nutlin-3 treatment of mice with established medulloblastoma xenografts inhibited tumor growth and significantly increased survival. Thus, nutlin-3 reduced medulloblastoma cell viability in vitro and in vivo by re-activating p53 function. We suggest that inhibition of the MDM2-p53 interaction with nutlin-3 is a promising therapeutic option for medulloblastomas with functional p53 that should be further evaluated in clinical trials.

Arsenic antagonizes the Hedgehog pathway by preventing ciliary accumulation and reducing stability of the Gli2 transcriptional effector.

Aberrant Hedgehog (Hh) pathway activation has been implicated in cancers of diverse tissues and organs, and the tumor growth-inhibiting effects of pathway antagonists in animal models have stimulated efforts to develop pathway antagonists for human therapeutic purposes. These efforts have focused largely on cyclopamine derivatives or other compounds that mimic cyclopamine action in binding to and antagonizing Smoothened, a membrane transductory component. We report here that arsenicals, in contrast, antagonize the Hh pathway by targeting Gli transcriptional effectors; in the short term, arsenic blocks Hh-induced ciliary accumulation of Gli2, the primary activator of Hh-dependent transcription, and with prolonged incubation arsenic reduces steady-state levels of Gli2. Arsenicals active in Hh pathway antagonism include arsenic trioxide (ATO), a curative agent in clinical use for acute promyelocytic leukemia (APL); in our studies, ATO inhibited growth of Hh pathway-driven medulloblastoma allografts derived from Ptch+/-p53-/- mice within a range of serum levels comparable to those achieved in treatment of human APL. Arsenic thus could be tested rapidly as a therapeutic agent in malignant diseases associated with Hh pathway activation and could be particularly useful in such diseases that are inherently resistant or have acquired resistance to cyclopamine mimics.

Protective role of 17 ß-estradiol on medulloblastoma development in Patched 1 heterozygous mice.

Medulloblastoma (MB) is the most common pediatric tumor of the CNS, representing ∼20% of all childhood CNS tumors. Although in recent years many molecular mechanisms that control MB development have been clarified, the effects of biological factors such as sex on this tumor remain to be explained. Epidemiological data, in fact, indicate a significant difference in the incidence of MB between the 2 sexes, with considerably higher susceptibility of males than females. Besides this different susceptibility, female sex is also a significant favorable prognostic factor in MB, with girls having a much better outcome. Despite these literature data, there has been little investigation into estrogen influence on MB development. In our study, we evaluated how hormone deficiency resulting from ovariectomy and hormone replacement influences the development of early and advanced MB stages in Patched1 heterozygous mice, a well-characterized mouse model of radiation-induced MB. Susceptibility to MB development was significantly increased in ovariectomized Ptch1(+/-) females and restored to levels observed in control mice after estrogen replacement. We next investigated the molecular mechanisms by which estrogen might influence tumor progression and show that ERß, but not ERα, is involved in modulation of MB development by estrogens. Finally, our study shows that a functional interaction between estrogen- and IGF-I-mediated pathways may be responsible for the effects observed.

Deletion of Atoh1 disrupts Sonic Hedgehog signaling in the developing cerebellum and prevents medulloblastoma.

Granule neuron precursors (GNPs) are the most actively proliferating cells in the postnatal nervous system, and mutations in pathways that control the GNP cell cycle can result in medulloblastoma. The transcription factor Atoh1 has been suspected to contribute to GNP proliferation, but its role in normal and neoplastic postnatal cerebellar development remains unexplored. We show that Atoh1 regulates the signal transduction pathway of Sonic Hedgehog, an extracellular factor that is essential for GNP proliferation, and demonstrate that deletion of Atoh1 prevents cerebellar neoplasia in a mouse model of medulloblastoma. Our data shed light on the function of Atoh1 in postnatal cerebellar development and identify a new mechanism that can be targeted to regulate medulloblastoma formation.

Two tumor suppressors, p27Kip1 and patched-1, collaborate to prevent medulloblastoma.

Two cyclin-dependent kinase inhibitors, p18(Ink4c) and p27(Kip1), are required for proper cerebellar development. Loss of either of these proteins conferred a proliferative advantage to granule neuron progenitors, although inactivation of Kip1 exerted a greater effect. Mice heterozygous for Patched-1 (Ptc1+/-) that are either heterozygous or nullizygous for Kip1 developed medulloblastoma rapidly and with high penetrance. All tumors from Ptc1+/-;Kip1+/- or Ptc1+/-;Kip1-/- mice failed to express the wild-type Ptc1 allele, consistent with its role as a canonical "two-hit" tumor suppressor. In contrast, expression of the wild-type p27(Kip1) protein was invariably maintained in medulloblastomas arising in Ptc1+/-;Kip1+/- mice, indicating that Kip1 is haploinsufficient for tumor suppression. Although medulloblastomas occurring in Ptc1+/- mice were histopathologically heterogeneous and contained intermixed regions of both rapidly proliferating and nondividing more differentiated cells, tumors that also lacked Kip1 were uniformly less differentiated, more highly proliferative, and invasive. Molecular analysis showed that the latter medulloblastomas exhibited constitutive activation of the Sonic hedgehog signaling pathway without loss of functional p53. Apart from gains or losses of single chromosomes, with gain of chromosome 6 being the most frequent, no other chromosomal anomalies were identified by spectral karyotyping, and half of the medulloblastomas so examined retained a normal karyotype. In this respect, this mouse medulloblastoma model recapitulates the vast majority of human medulloblastomas that do not sustain TP53 mutations and are not aneuploid.

Sonic Hedgehog signaling impairs ionizing radiation-induced checkpoint activation and induces genomic instability.

The Sonic Hedgehog (Shh) pathway plays important roles in embryogenesis, stem cell maintenance, tissue repair, and tumorigenesis. Haploinsufficiency of Patched-1, a gene that encodes a repressor of the Shh pathway, dysregulates the Shh pathway and increases genomic instability and the development of spontaneous and ionizing radiation (IR)-induced tumors by an unknown mechanism. Here we show that Ptc1(+/-) mice have a defect in the IR-induced activation of the ATR-Chk1 checkpoint signaling pathway. Likewise, transient expression of Gli1, a downstream target of Shh signaling, disrupts Chk1 activation in human cells by preventing the interaction of Chk1 with Claspin, a Chk1 adaptor protein that is required for Chk1 activation. These results suggest that inappropriate Shh pathway activation promotes tumorigenesis by disabling a key signaling pathway that helps maintain genomic stability and inhibits tumorigenesis.

Post-transcriptional down-regulation of Atoh1/Math1 by bone morphogenic proteins suppresses medulloblastoma development.

Bone morphogenic proteins 2 and 4 (BMP2 and BMP4) inhibit proliferation and induce differentiation of cerebellar granule neuron progenitors (GNPs) and primary GNP-like medulloblastoma (MB) cells. This occurs through rapid proteasome-mediated degradation of Math1 (Atoh1), a transcription factor expressed in proliferating GNPs. Ectopic expression of Atoh1, but not of Sonic hedgehog (Shh)-regulated Gli1 or Mycn, cancels these BMP-mediated effects and restores Shh-dependent proliferation of GNPs and MB cells in vitro and in vivo. Genes regulating the BMP signaling pathway are down-regulated in mouse MBs. Thus, BMPs are potent inhibitors of MB and should be considered as novel therapeutic agents.

Inhibition of medulloblastoma tumorigenesis by the antiproliferative and pro-differentiative gene PC3.

Medulloblastoma, the most common brain tumor in childhood, appears to originate from cerebellar granule cell precursors (GCPs), located in the external granular layer (EGL) of the cerebellum. The antiproliferative gene PC3 (Tis21/BTG2) promotes cerebellar neurogenesis by inducing GCPs to shift from proliferation to differentiation. To assess whether PC3 can prevent the neoplastic transformation of GCPs and medulloblastoma development, we crossed transgenic mice conditionally expressing PC3 (TgPC3) in GCPs with Patched1 heterozygous mice (Ptc(+/-)), a model of medulloblastoma pathogenesis characterized by hyperactivation of the Sonic Hedgehog pathway. Perinatal up-regulation of PC3 in Ptc(+/-)/TgPC3 mice results in a decrease of medulloblastoma incidence of approximately 40% and in a marked reduction of preneoplastic abnormalities, such as hyperplastic EGL areas and lesions. Moreover, overexpression of cyclin D1, hyperproliferation, and defective differentiation--observed in Ptc(+/-) GCPs--are restored to normality in Ptc(+/-)/TgPC3 mice. The PC3-mediated inhibition of cyclin D1 expression correlates with recruitment of PC3 to the cyclin D1 promoter, which is accompanied by histone deacetylation. Remarkably, down-regulation of PC3 is observed in preneoplastic lesions, as well as in human and murine medulloblastomas. As a whole, this indicates that PC3 may prevent medulloblastoma development by controlling cell cycle and promoting differentiation of GCPs.

Maternal supplement, micronutrient, and cured meat intake during pregnancy and risk of medulloblastoma during childhood: a children's oncology group study.

We conducted a case-control study of medulloblastoma/primitive neuroectodermal tumors of brain (PNET) to pursue findings related to vitamin and mineral supplements, micronutrients, and cured meat consumption during gestation. Mothers of 315 cases ages <6 years at diagnosis in 1991 to 1997 identified from the United States and Canada through the Children's Oncology Group and mothers of 315 controls selected by random-digit dialing were interviewed. In the periconception period of the index pregnancy, case mothers were less likely than control mothers to report use of multivitamins [adjusted odds ratio (OR), 0.7; 95% confidence interval (95% CI), 0.4-1.0; P = 0.08] and to be in the highest quartile of iron and folate intake from food and supplements combined (adjusted OR for iron, 0.5; 95% CI, 0.3-0.9; P(trend) = 0.008; adjusted OR for folate, 0.5; 95% CI, 0.3-0.9; P(trend) = 0.007). Case and control mothers had similar intakes of cured meats, although case mothers were more likely to have the combination of high cured meat and low vitamin C intake (OR, 1.5; 95% CI, 1.0-2.3; P = 0.08). The results of the study add to the evidence of a protective role for multivitamins, suggest a possible role for micronutrients early in pregnancy, and generally do not support an association between cured meats and medulloblastoma/PNET.

Maternal diet during pregnancy and its association with medulloblastoma in children: a children's oncology group study (United States).

Fruit, vegetables, vitamin C, and folate during pregnancy have been suggested as protective factors for medulloblastoma/primitive neuroectodermal tumor (PNET), a common brain tumor in children. The authors sought to replicate these findings and investigate other aspects of diet. Mothers of 315 cases under age six at diagnosis and 315 controls were interviewed about their pregnancy diet. The authors observed modest, inverse associations for fruits/juices (odds ratio (OR) for highest compared to lowest category = 0.6, 95% confidence interval (CI): 0.3, 1.1) and vitamin C (OR = 0.6, 95% CI: 0.4, 1.1). In contrast to the previous study, folate and vegetables showed no association. As hypothesized, cured meats were not associated with medulloblastoma/PNET, in contrast to other childhood brain tumors. An inverse association with non-fresh peaches and similar fruits (OR = 0.5, 95% CI: 0.3, 0.8) and a positive association with non-chocolate candy (OR = 1.7, 95% CI: 1.0, 3.0) replicated previous findings. French fries (OR = 2.4, 95% CI: 1.2, 4.9) and chili peppers (OR = 1.8, 95% CI: 1.0, 3.0) were associated with medulloblastoma/PNET. The results suggest that some aspects of diet are worthy of further research.

Long-term results of the first 500 cases of acoustic neuroma surgery.

OBJECTIVE: This retrospective study focuses on 2 outcome results after surgical intervention for acoustic neuroma: (1) facial nerve status, and (2) hearing preservation. STUDY DESIGN: A total of 484 patients with an acoustic neuroma. RESULTS: Postoperative facial nerve outcomes were significantly different (P < 0.001) according to the size of the tumors. Tumor size had even more influence on the immediate postoperative results. In addition, statistical significance (P < 0.05) was demonstrated in comparing facial nerve outcomes with the surgeon's surgical experience. We also noted that as the patient's age increases, the likelihood for facial dysfunction may increase for all postoperative intervals. The overall success rate of retaining useful hearing was 27% (26 of 95). Class A hearing was retained in 66% (10 of 15) of cases operated on through middle fossa approach in the last 5 years. CONCLUSION: This study demonstrates that tumor size and surgeon's experience are the most significant factors influencing the facial nerve status and hearing outcome after removal of acoustic neuroma.

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.

Improving survival in recurrent medulloblastoma: earlier detection, better treatment or still an impasse?

Early detection of relapse has been advocated to improve survival in children with recurrent medulloblastoma. However, the prognostic factors and the longer term outcome of these patients remains unclear. Pattern of recurrences were analysed in three consecutive protocols of the Société Française d'Oncologie Pédiatrique (1985-91). A uniform surveillance programme including repeated lumbar puncture combined with computerized tomography (CT) or magnetic resonance imaging (MRI) scan was applied for all registered patients. Forty-six out of 116 patients had progressive or recurrent disease. The median time from diagnosis to recurrence was 10.5 months and 76% relapses occurred during the first 2 years. Seventeen patients had asymptomatic relapses that were detected by the surveillance protocol. Forty-one patients were treated at time of progression. Twenty-three responded to salvage therapy and 11 achieved a second complete remission. The median survival time after progression was 5 months (<1-41 months), and only two patients remained alive at time of follow-up. Length of survival is primarily related to some specific patterns of relapse (time from diagnosis to recurrence, circumstances of relapse, extent of relapse) and to the response to salvage therapy. No evidence of long-term benefit appeared from any form of treatment.