Characteristics and outcome of pediatric renal cell carcinoma patients registered in the International Society of Pediatric Oncology (SIOP) 93-01, 2001 and UK-IMPORT database: A report of the SIOP-Renal Tumor Study Group.

In children, renal cell carcinoma (RCC) is rare. This study is the first report of pediatric patients with RCC registered by the International Society of Pediatric Oncology-Renal Tumor Study Group (SIOP-RTSG). Pediatric patients with histologically confirmed RCC, registered in SIOP 93-01, 2001 and UK-IMPORT databases, were included. Event-free survival (EFS) and overall survival (OS) were analyzed using the Kaplan-Meier method. Between 1993 and 2019, 122 pediatric patients with RCC were registered. Available detailed data (n = 111) revealed 56 localized, 30 regionally advanced, 25 metastatic and no bilateral cases. Histological classification according to World Health Organization 2004, including immunohistochemical and molecular testing for transcription factor E3 (TFE3) and/or EB (TFEB) translocation, was available for 65/122 patients. In this group, the most common histological subtypes were translocation type RCC (MiT-RCC) (36/64, 56.3%), papillary type (19/64, 29.7%) and clear cell type (4/64, 6.3%). One histological subtype was not reported. In the remaining 57 patients, translocation testing could not be performed, or TFE-cytogenetics and/or immunohistochemistry results were missing. In this group, the most common RCC histological subtypes were papillary type (21/47, 44.7%) and clear cell type (11/47, 23.4%). Ten histological subtypes were not reported. Estimated 5-year (5y) EFS and 5y OS of the total group was 70.5% (95% CI = 61.7%-80.6%) and 84.5% (95% CI = 77.5%-92.2%), respectively. Estimated 5y OS for localized, regionally advanced, and metastatic disease was 96.8%, 92.3%, and 45.6%, respectively. In conclusion, the registered pediatric patients with RCC showed a reasonable outcome. Survival was substantially lower for patients with metastatic disease. This descriptive study stresses the importance of full, prospective registration including TFE-testing.

Kostmann disease and other forms of severe congenital neutropenia.

Congenital neutropenia with autosomal recessive inheritance was first described by the Swedish paediatrician Rolf Kostmann who coined the term 'infantile genetic agranulocytosis'. The condition is now commonly referred to as Kostmann disease. These patients display a maturation arrest of the myelopoiesis in the bone marrow and reduced neutrophil numbers and suffer from recurrent, often life-threatening infections. The molecular mechanism underlying congenital neutropenia has been intensively investigated, and mutations in genes that impinge on programmed cell death have been identified. The present review provides an overview of these studies.

Convergent evolution of 11p allelic loss in multifocal Wilms tumors arising in WT1 mutation carriers.

Wilms tumors in patients with constitutional WT1 mutations are examples of Knudson's tumor suppressor paradigm, with somatic inactivation of the second allele occurring through 11p loss of heterozygosity. The time point of this second hit has remained unknown. We analyzed seven Wilms tumors from two patients with constitutional WT1 mutations by whole exome sequencing and genomic array. All tumors exhibited wild type WT1 loss through uniparental isodisomy. Each tumor had a unique genomic breakpoint in 11p, typically accompanied by a private activating mutation of CTNNB1. Hence, convergent evolution rather than field carcinogenesis underlies multifocal tumors in WT1 mutation carriers.

Omission of doxorubicin from the treatment of stage II-III, intermediate-risk Wilms' tumour (SIOP WT 2001): an open-label, non-inferiority, randomised controlled trial.

BACKGROUND: Before this study started, the standard postoperative chemotherapy regimen for stage II-III Wilms' tumour pretreated with chemotherapy was to include doxorubicin. However, avoidance of doxorubicin-related cardiotoxicity effects is important to improve long-term outcomes for childhood cancers that have excellent prognosis. We aimed to assess whether doxorubicin can be omitted safely from chemotherapy for stage II-III, histological intermediate-risk Wilms' tumour when a newly defined high-risk blastemal subtype was excluded from randomisation. METHODS: For this international, multicentre, open-label, non-inferiority, phase 3, randomised SIOP WT 2001 trial, we recruited children aged 6 months to 18 years at the time of diagnosis of a primary renal tumour from 251 hospitals in 26 countries who had received 4 weeks of preoperative chemotherapy with vincristine and actinomycin D. Children with stage II-III intermediate-risk Wilms' tumours assessed after delayed nephrectomy were randomly assigned (1:1) by a minimisation technique to receive vincristine 1·5 mg/m(2) at weeks 1-8, 11, 12, 14, 15, 17, 18, 20, 21, 23, 24, 26, and 27, plus actinomycin D 45 µg/kg every 3 weeks from week 2, either with five doses of doxorubicin 50 mg/m(2) given every 6 weeks from week 2 (standard treatment) or without doxorubicin (experimental treatment). The primary endpoint was non-inferiority of event-free survival at 2 years, analysed by intention to treat and a margin of 10%. Assessment of safety and adverse events included systematic monitoring of hepatic toxicity and cardiotoxicity. This trial is registered with EudraCT, number 2007-004591-39, and is closed to new participants. FINDINGS: Between Nov 1, 2001, and Dec 16, 2009, we recruited 583 patients, 341 with stage II and 242 with stage III tumours, and randomly assigned 291 children to treatment including doxorubicin, and 292 children to treatment excluding doxorubicin. Median follow-up was 60·8 months (IQR 40·8-79·8). 2 year event-free survival was 92·6% (95% CI 89·6-95·7) for treatment including doxorubicin and 88·2% (84·5-92·1) for treatment excluding doxorubicin, a difference of 4·4% (95% CI 0·4-9·3) that did not exceed the predefined 10% margin. 5 year overall survival was 96·5% (94·3-98·8) for treatment including doxorubicin and 95·8% (93·3-98·4) for treatment excluding doxorubicin. Four children died from a treatment-related toxic effect; one (<1%) of 291 receiving treatment including doxorubicin died of sepsis, three (1%) of 292 receiving treatment excluding doxorubicin died of varicella, metabolic seizure, and sepsis during treatment for relapse. 17 patients (3%) had hepatic veno-occlusive disease. Cardiotoxic effects were reported in 15 (5%) of 291 children receiving treatment including doxorubicin. 12 children receiving treatment including doxorubicin, and ten children receiving treatment excluding doxorubicin, died, with the remaining deaths from tumour recurrence. INTERPRETATION: Doxorubicin does not need to be included in treatment of stage II-III intermediate risk Wilms' tumour when the histological response to preoperative chemotherapy is incorporated into the risk stratification. FUNDING: See Acknowledgments for funders.

Experimental teratoma: at the crossroad of fetal- and onco-development.

Xenografting is the so far only available in vivo model for assessing pluripotency of human stem cells. This review describes known biological features of experimental teratoma from human pluripotent stem cells. We focus on the dual nature mimicking both normal and abnormal development, and propose this model system to be particularly interesting for investigations of the relationship between developmentally controlled differentiation and neoplasia of embryonic origin. In resemblance to the wide range of clinical teratomas, pluripotent stem cell (PSC) induced teratoma (PSCT) typically shows a mixture of developing tissues in randomly distributed compartments. The combined literature suggests that for teratomas derived from human diploid bona fide PSC the embryonic development in the separate tissue-niches can show a controlled differentiation into organoid patterns closely mimicking early development. In the experimental situation such PSCT human homologous in vivo tissue-niches have been shown to provide also matching microenvironment for a micrometastatic colonization and outgrowth of embryonic tumors transplanted directly from patients. Single or small clusters of normal and neoplastic cells can easily be visualized together in microscope-based imaging systems, enabling multi-parameter detection of in the scans of tissue slides/specimens.

Tropism of the in situ growth from biopsies of childhood neuroectodermal tumors following transplantation into experimental teratoma.

Experimental teratoma induced from human pluripotent stem cells with normal karyotype can be described as a failed embryonic process and includes besides advanced organoid development also large elements of tissue with a prolonged occurrence of immature neural components. Such immature components, although benign, exhibit strong morphological resemblance with tumors of embryonic neuroectodermal origin. Here, we demonstrate that biopsy material from childhood tumors of neural embryonic origin transplanted to mature experimental teratoma can show an exclusive preference for matching tissue. Tumor specimens from five children with; Supratentorial primitive neuroectodermal tumor (sPNET); Pilocytic astrocytoma of the brainstem; Classic medulloblastoma; peripheral primitive neuroectodermal tumor (pPNET) or neuroblastoma (NB), respectively, were transplanted. Analysis of up to 120 sections of each tumor revealed an engraftment for three of the transplanted tumors: pPNET, sPNET, and NB, with a protruding growth from the latter two that were selected for detailed examination. The histology revealed a strict tropism with a non-random integration into what morphologically appeared as matched embryonic microenvironment recuperating the patient tumor histology. The findings suggest specific advantages over xenotransplantation and lead us to propose that transplantation to the human embryonic microenvironment in experimental teratoma can be a well-needed complement for preclinical in vivo studies of childhood neuroectodermal tumors.

Nephron sparing surgery (NSS) for unilateral wilms tumor (UWT): the SIOP 2001 experience.

BACKGROUND: Total nephrectomy (TN) remains the standard treatment of unilateral Wilms tumors (uWT). The SIOP WT-2001 protocol allowed Nephron Sparing Surgery (NSS) for polar or peripherally non-infiltrating tumors. AIM: Inventory of the current SIOP NSS-experience. PROCEDURES: 2,800 patients with a unilateral, localized or metastatic and an unequivocal surgical technique recorded were included. All had neo-adjuvant chemotherapy and delayed surgery. In 91 (3%) NSS was performed and in 2709 TN. Data was retrieved from the SIOP WT 2001 database. RESULTS: NSS group contained 65% stage I tumours and the TN group 48%. Tumor volume (at diagnosis and surgery) was significantly smaller in the NSS group. Within stage III, after NSS, 7/12 (58%) had positive margins (M +), 5 with tumor negative lymph nodes (LN-). After TN, 355/712 (55%) had M + , 182 were LN-. Treatment of M+ in the NSS group resulted in two conversions to TN (one combined with radiotherapy), three patients had radiotherapy only and in two patients local therapy, if given, was not recorded. After NSS, four recurrences occurred. For localized disease the 5-year overall (OS) and event free survival (EFS) in NSS group was 100 and 94.8 (95% CI:89.9-99.9), respectively, while OS and EFS in the TN group were 94.4 (95% CI: 93.2-95.5, log-rank test P = 0.06) and 86.5 (95% CI:85.0-88.1, log-rank test P = 0.06), respectively. CONCLUSIONS: NSS was only performed in 3% of patients with uWT. Despite excellent survival with few relapses, the gain of nephrons needs to be weighed against the risk to induce stage III with intensified therapy.

SIX1 protein expression selectively identifies blastemal elements in Wilms tumor.

BACKGROUND: Wilms tumor (WT) is the most common renal neoplasm in children. Histologically, most WTs consist of three tissue elements: blastema, epithelium, and stroma. Some cases also show diffuse or focal anaplastic features. Previous studies have shown that a predominance of blastemal cells in post-chemotherapy WT specimens is associated with a poor clinical course. However, there is currently no molecular marker for blastemal cells, and risk stratification for post-nephrectomy treatment is therefore often based on clinico-histological parameters alone. PROCEDURE: In the present study, three public gene expression microarray datasets, including 82 WTs and 8 normal fetal kidneys, were used to establish a consensus gene expression profile of WT. By bioinformatic analyses, 17 genes overexpressed in WT compared to fetal kidney were then selected for evaluation of their protein expression in WT cell lines and in the different histological components in paraffin-embedded WT tissue sections by immunofluorescence. RESULTS: Most of the evaluated proteins were expressed in all three common histological components. A prominent exception was SIX1, being expressed predominantly in blastemal elements in 24/25 pediatric cases containing blastema. Anaplastic elements exhibited highly variable SIX1-positivity. The SIX2 protein, known to be co-expressed with SIX1 during nephrogenesis, only exhibited blastemal-predominant expression in half of the SIX2 evaluated cases. CONCLUSIONS: Genes highly expressed in WT compared to fetal kidney are generally overexpressed in all of the three common WT tissue elements. An exception is the predominant expression of SIX1 in blastemal cells, hereby identifying this protein as a candidate marker for blastema.

Amplification of CDK4 and MDM2: a detailed study of a high-risk neuroblastoma subgroup.

In neuroblastoma, MYCN amplification and 11q-deletion are important, although incomplete, markers of high-risk disease. It is therefore relevant to characterize additional alterations that can function as prognostic and/or predictive markers. Using SNP-microarrays, a group of neuroblastoma patients showing amplification of one or multiple 12q loci was identified. Two loci containing CDK4 and MDM2 were commonly co-amplified, although amplification of either locus in the absence of the other was observed. Pharmacological inhibition of CDK4/6 with ribociclib or abemaciclib decreased proliferation in a broad set of neuroblastoma cell lines, including CDK4/MDM2-amplified, whereas MDM2 inhibition by Nutlin-3a was only effective in p53wild-type cells. Combined CDK4/MDM2 targeting had an additive effect in p53wild-type cell lines, while no or negative additive effect was observed in p53mutated cells. Most 12q-amplified primary tumors were of abdominal origin, including those of intrarenal origin initially suspected of being Wilms' tumor. An atypical metastatic pattern was also observed with low degree of bone marrow involvement, favoring other sites such as the lungs. Here we present detailed biological data of an aggressive neuroblastoma subgroup hallmarked by 12q amplification and atypical clinical presentation for which our in vitro studies indicate that CDK4 and/or MDM2 inhibition also could be beneficial.

Deletions of 16q in Wilms tumors localize to blastemal-anaplastic cells and are associated with reduced expression of the IRXB renal tubulogenesis gene cluster.

Wilms tumor is the most common pediatric renal neoplasm, but few molecular prognostic markers have been identified for this tumor. Somatic deletion in the long arm of chromosome 16 (16q) is known to predict a less favorable outcome in Wilms tumor, but the underlying molecular mechanisms are not known. We show that 16q deletions are typically confined to immature anaplastic-blastic tumor elements, while deletions are absent in maturing tumor components. The smallest region of deletion overlap mapped to a 1.8-Mb segment containing the IRXB gene cluster including IRX3, IRX5, and IRX6, of which IRX3 is a recently identified regulator of tubular maturation during nephrogenesis. Tumors with 16q deletion showed a lower overall mRNA expression of IRXB genes, and 16q-deleted tumor cells failed to express IRX3 while it was expressed in differentiating tubular tumor elements with intact 16q. Consistent with a role for IRX3 in tubular differentiation, gene sets linked to Notch signaling, Rho signaling, and ion channel activity were enriched in tumors with high IRX3 expression, while WTs with low expression were enriched for gene sets linked to cell cycle progression. Low mRNA levels of IRXB genes were associated with diffuse anaplasia, high-stage disease, and death. A disturbed balance between tubular differentiation and self-renewal of anaplastic-blastic elements may thus be one mechanism linking 16q deletion to adverse outcome in Wilms tumor.

Nephroblastoma: does the decrease in tumor volume under preoperative chemotherapy predict the lymph nodes status at surgery?

BACKGROUND: Partial nephrectomy (NSS) for unilateral nephroblastoma may be beneficial, although in case of regional lymph node (LN) involvement, radiotherapy counteracts the functional benefit of NSS. The aim is to verify whether decrease of tumor volume under preoperative chemotherapy implies clearance of regional LN. PROCEDURE: SIOP 9301 (1993-2001) collected 1,450 localized nephroblastoma patients of whom 1,360 (93%) had sufficiently available data and were retrospectively reviewed. RESULTS: Histologic subtypes were classically distributed. Patients were divided in those with tumor positive LN (76, 5.5%) and those with tumor negative LN (1,284, 94.5%) at surgery. In the LN(+) group, the tumor volume changed from a median of 554 (318-772) to 192 (63-458) ml = 67% (27-88%) during preoperative ChT. In the LN(-) group-377 (200-612) to 130 (44-294) ml = 62% (28-83%) (NS). Increase of tumor volume was observed in 16% of patients with LN(+), and 11% of those with LN(-) (NS); ranges are interquartile. Initial tumor volume was significantly larger in the LN(+) patients (P = 0.00091) but not different (NS) at surgery; patients with initial tumor volume under 318 ml had the regional LN involved significantly less frequently (P = 0.00751). CONCLUSIONS: Change in tumor volume under preoperative chemotherapy is not a predictor for LN status at surgery, although larger initial volume is associated with a higher risk of LN invasion. The decrease of tumor volume is not a good criterion for the safety of NSS. The low rate of LN(+) (5.5%) indicates that this risk is low.

Malignant rhabdoid tumours of the kidney (MRTKs), registered on recent SIOP protocols from 1993 to 2005: a report of the SIOP renal tumour study group.

BACKGROUND: Survival data of malignant rhabdoid tumour of the kidney (MRTK) registered in SIOP trials, advocating preoperative chemotherapy, are not available. AIM: To evaluate characteristics, response and survival of MRTK patients registered in recent SIOP protocols. METHODS: An evaluation of all MRTK patients treated from 1993 to 2005 (SIOP trials 93-01 and 2001) was performed. Data were obtained from study specific case record forms and entered centrally in a database. RESULTS: Hundred and seven patients were identified (57 male), with a median age at diagnosis of 13 months (interquartile range 6-27 months), and a median follow-up time of 60 months. Left and right kidneys were equally affected. Tumour stage distribution was stage I (6%), stage II (22%), stage III (43%), stage IV (22%) and stage V (3%). Stage IV patients included 17 with pulmonary metastasis (8 lung-only) and 12 with multiple organ metastases (bone, brain and liver). Primary surgery was the upfront treatment approach in 22/107 patients (21%), by which 19 patients reached a complete remission (CR). Median difference in tumour volume before and after preoperative chemotherapy was 69 ml (interquartile range: 4.5-158.0, P < 0.0001), indicating marked chemosensitivity. The 5-year event-free survival (EFS) of the total group was 22% (95% CI: 15-33) and overall survival 26% (95% CI: 18-37). Most events (86%) occurred within the first 2 years after diagnosis. Younger age at diagnosis was an important adverse prognostic factors for survival. In contrast, tumour volume at diagnosis, nor volume reduction was associated with outcome. CONCLUSION: MRTK has a poor outcome especially in young and advanced-stage disease patients. Neither tumour volume at diagnosis, nor pre-operative chemosensitivity are prognostic factors for survival.

Incidence and survival analyses in children with solid tumours diagnosed in Sweden between 1983 and 2007.

AIM: Solid tumours constitute 40% of childhood malignancies. The Swedish Childhood Cancer Registry is population based and includes all children with cancer reported from the six paediatric oncology centres in Sweden. The aim was to investigate incidence and survival. METHODS: We used the new WHO ICCC-3 for reclassification of the patients. Incidence and survival analyses were performed in the study population. RESULTS: Two thousand four hundred and eighty-seven children (<15 years) were diagnosed with solid tumours in Sweden between 1983 and 2007. The distribution of diagnoses was similar to that reported in other studies. The annual incidence was 65.3 per million children. The survival rates at 10 years of follow-up have improved significantly when comparing the two time periods, 1983-1995 and 1995-2007 (76 vs. 82%; p < 0.01). CONCLUSIONS: The mean annual incidence of solid tumours in children was 65.3/million and has been stable during the study period. Survival rates for solid tumours at 5, 10 and 20 years follow-up were 80, 79 and 76%, respectively.

Stromal and epithelial predominant Wilms tumours have an excellent outcome: the SIOP 93 01 experience.

BACKGROUND: Wilms tumour (WT) has various subtypes that are correlated with prognosis and require distinct therapy. Stromal predominant (SpWT) and epithelial WT (EpWT) have previously been associated with a good outcome. The current analysis describes the outcome and (tumour) characteristics of all patients with SpWT, EpWT, including highly differentiated epithelial type (HDET), treated according to the International Society of Pediatric Oncology (SIOP) 93-01 study. PROCEDURE: All children older than 6 months and below 18 years of age with localized or metastatic WT and intermediate risk (IR) histology or HDET treated with pre-operative chemotherapy were included in the present analysis. RESULTS: A total of 1,389 eligible patients had IR or HDET histology: 1% HDET, 4% EpWT, 10% SpWT, and 85% other IR. For EpWT/HDET, 93% had stage I/IIN-, 5-year EFS was 90.2% and overall survival of (OS) 98.4%, as compared to 84.0% and 92.5% in other IR histology (NS). Stage I EpWT/HDET had a significant better outcome than stage I of other IR. In SpWT 82% of cases had stage I/IIN-; 5-year EFS was 94.3% and OS 99.2%, significantly better compared to other IR histology. All patients with stage I are alive (2/149 relapses); 3/52 stage IIN-, 2/21 stage IIN+/III, and 6/12 stage IV patients relapsed (1 deceased per stage group). CONCLUSIONS: The good outcome for EpWT and SpWT generally is very good which may be related to low age and low stage in most cases. A reduction of treatment intensity and/or duration may be justified especially for low stage SpWT that has an EFS close to 100%.

Human antimicrobial protein hCAP18/LL-37 promotes a metastatic phenotype in breast cancer.

INTRODUCTION: Human cathelicidin antimicrobial protein, hCAP18, and its C-terminal peptide LL-37 is a multifunctional protein. In addition to being important in antimicrobial defense, it induces chemotaxis, stimulates angiogenesis and promotes tissue repair. We previously showed that human breast cancer cells express high amounts of hCAP18, and hypothesised that hCAP18/LL-37 may be involved in tumour progression. METHODS: hCAP18 mRNA was quantified in 109 primary breast cancers and compared with clinical findings and ERBB2 mRNA expression. Effects of exogenous LL-37 and transgenic overexpression of hCAP18 on ErbB2 signalling were investigated by immunoblotting using extracts from breast cancer cell lines ZR75-1 and derivatives of MCF7. We further analysed the impact of hCAP18/LL-37 on the morphology of breast cancer cells grown in soft agar, on cell migration and on tumour development in severe combined immunodeficiency (SCID) mice. RESULTS: The expression of hCAP18 correlated closely with that of ERBB2 and with the presence of lymph node metastases in oestrogen receptor-positive tumours. hCAP18/LL-37 amplified Heregulin-induced mitogen-activated protein kinase (MAPK) signalling through ErbB2, identifying a functional association between hCAP18/LL-37 and ErbB2 in breast cancer. Treatment with LL-37 peptide significantly stimulated the migration of breast cancer cells and their colonies acquired a dispersed morphology indicative of increased metastatic potential. A truncated version of LL-37 competitively inhibited LL-37 induced MAPK phosphorylation and significantly reduced the number of altered cancer cell colonies induced by LL-37 as well as suppressed their migration. Transgenic overexpression of hCAP18 in a low malignant breast cancer cell line promoted the development of metastases in SCID mice, and analysis of hCAP18 transgenic tumours showed enhanced activation of MAPK signalling. CONCLUSIONS: Our results provide evidence that hCAP18/LL-37 contributes to breast cancer metastasis.

High-resolution molecular cytogenetic analysis of Wilms tumors highlights diagnostic difficulties among small round cell kidney tumors.

Many solid tumors exhibit characteristic gene fusions, which are reflected by balanced translocations at the cytogenetic level. These changes might be useful diagnostic and prognostic tools. In Wilms tumor (WT, nephroblastoma) no fusions genes or recurrent balanced translocations have been described thus far. To screen for cryptic balanced translocations, we have analyzed 17 renal neoplasms, histopathologically classified as WT, by a combination of G-banding, multicolor FISH, and subtelomeric FISH. This approach revealed several submicroscopic chromosomal aberrations and three different seemingly balanced translocations, resulting in a heterozygous deletion of HACE1, an EWSR1/ERG fusion, and an EWSR1/FLI1 fusion, respectively. As EWSR1 rearrangements are known to be a characteristic of Ewing tumors (ET), our findings illustrate the diagnostic problems regarding small cell kidney tumors and strongly argue for the need of adjuvant diagnostic techniques in this group of neoplasms. In summary, our genomic screening approach proved efficient in finding structural chromosomal aberrations. The fact that no recurrent translocations were found in the WTs of this study argues against the presence of a frequent pathognomonic translocation in this disease entity.

Analysis of neuroblastoma tumour progression; loss of PHOX2B on 4p13 and 17q gain are early events in neuroblastoma tumourigenesis.

Neuroblastomas are biologically and clinically heterogeneous tumours that most often occur sporadically in children at median age of 2 years. The PHOX2B gene is implicated in the development of the autonomic nervous system and has been found to be infrequently mutated in sporadic neuroblastoma tumours and in some patients with hereditary neuroblastoma. We have screened a selected series of 36 paediatric tumours with presumed genetic predisposition, 34 of them neuroblastomas, for mutations in PHOX2B. A constitutional heterozygous missense mutation was found in a boy who developed bilateral adrenal tumours and stage 4 disease during infancy. The second allele of the PHOX2B locus was lost in the tumour DNA. Histopathological evaluation of the tumours suggested growth of two primary tumours, one with diploid DNA content and the other with tetraploid DNA content, i.e. a case of neuroblastoma stage 4M (multifocal tumour). However, array CGH (comparative genomic hybridization) data performed on both tumour masses from the patient instead supported a model where a common malignant precursor gave rise to the diploid tumour and subsequently the tetraploid tumour have progressed from the common precursor or by metastasis from the diploid tumour with additional genetic changes. The whole genome dosage analysis showed that the remaining alleles of PHOX2B had been lost in both tumours together with a specific 17q gain pattern. The tetraploid tumour had these features together with additional whole chromosomal loss of chromosomes 3, 9, 14 and 15. Based on the data presented here we suggest that loss of PHOX2B and 17q gain are early events in neuroblastoma tumourigenesis. We also propose investigators to re-analyze the rare cases of multifocal neuroblastomas with the array CGH technique for better understanding of the origin of these tumours.

Defective chromosome segregation and telomere dysfunction in aggressive Wilms' tumors.

PURPOSE: In many childhood neoplasms, prognostic subgroups have been defined based on specific chromosome changes. In Wilms' tumor (WT), such subclassification has been hampered by the diverse and relatively unspecific pattern of chromosomal imbalances present in these tumors. Unspecific patterns of cytogenetic imbalances in tumors are often caused by mitotic segregation errors due to short dysfunctional telomeres. As an alternative to cytogenetic classification, we therefore have evaluated whether the rate of telomere-dependent chromosomal instability could influence the clinical course in WT patients. EXPERIMENTAL DESIGN: Telomere function and mitotic segregation errors were assessed in 12 cultured tumors and in tumor tissue sections from 41 WT patients. RESULTS: Abnormal telomere shortening was found in cultured cells and in tissue sections from highly aggressive tumors. In vitro, dysfunctional telomeres were associated to specific cell division abnormalities, including anaphase bridges and multipolar mitoses. Assessment of mitotic figures in tissue sections revealed that anaphase bridges and multipolar mitoses were predominantly, but not exclusively, present in high-risk tumors and were predictors of poor event-free and overall survival. CONCLUSIONS: Telomere-dependent mitotic instability is present in a subgroup of WT, predominantly consisting of high-risk tumors.

Doxorubicin-provoked increase of mitotic activity and concomitant drain of G0-pool in therapy-resistant BE(2)-C neuroblastoma.

In this study chemotherapy response in neuroblastoma (NB) was assessed for the first time in a transplantation model comprising non-malignant human embryonic microenvironment of pluripotent stem cell teratoma (PSCT) derived from diploid bona fide hESC. Two NB cell lines with known high-risk phenotypes; the multi-resistant BE(2)-C and the drug sensitive IMR-32, were transplanted to the PSCT model and the tumour growth was exposed to single or repeated treatments with doxorubicin, and thereafter evaluated for cell death, apoptosis, and proliferation. Dose dependent cytotoxic effects were observed, this way corroborating the experimental platform for this type of analysis. Notably, analysis of doxorubicin-resilient BE(2)-C growth in the PSCT model revealed an unexpected 1,5-fold increase in Ki67-index (p<0.05), indicating that non-cycling (G0) cells entered the cell cycle following the doxorubicin exposure. Support for this notion was obtained also in vitro. A pharmacologically relevant dose (1µM) resulted in a marked accumulation of Ki67 positive BE(2)-C cells (p<0.0001), as well as a >3-fold increase in active cell cycle (i.e. cells positive staining for PH3 together with incorporation of EdU) (p<0.01). Considering the clinical challenge for treating high-risk NB, the discovery of a therapy-provoked growth-stimulating effect in the multi-resistant and p53-mutated BE(2)-C cell line, but not in the drug-sensitive p53wt IMR-32 cell line, warrants further studies concerning generality and clinical significance of this new observation.

Four evolutionary trajectories underlie genetic intratumoral variation in childhood cancer.

A major challenge to personalized oncology is that driver mutations vary among cancer cells inhabiting the same tumor. Whether this reflects principally disparate patterns of Darwinian evolution in different tumor regions has remained unexplored1-5. We mapped the prevalence of genetically distinct clones over 250 regions in 54 childhood cancers. This showed that primary tumors can simultaneously follow up to four evolutionary trajectories over different anatomic areas. The most common pattern consists of subclones with very few mutations confined to a single tumor region. The second most common is a stable coexistence, over vast areas, of clones characterized by changes in chromosome numbers. This is contrasted by a third, less frequent, pattern where a clone with driver mutations or structural chromosome rearrangements emerges through a clonal sweep to dominate an anatomical region. The fourth and rarest pattern is the local emergence of a myriad of clones with TP53 inactivation. Death from disease was limited to tumors exhibiting the two last, most dynamic patterns.