Dependence of Wilms tumor cells on signaling through insulin-like growth factor 1 in an orthotopic xenograft model targetable by specific receptor inhibition

Hallmark discoveries in the biology of Wilms tumour

The modern study of Wilms tumour was prompted nearly 50 years ago, when Alfred Knudson proposed the 'two-hit' model of tumour development. Since then, the efforts of researchers worldwide have substantially expanded our knowledge of Wilms tumour biology, including major advances in genetics - from cloning the first Wilms tumour gene to high-throughput studies that have revealed the genetic landscape of this tumour. These discoveries improve understanding of the embryonal origin of Wilms tumour, familial occurrences and associated syndromic conditions. Many efforts have been made to find and clinically apply prognostic biomarkers to Wilms tumour, for which outcomes are generally favourable, but treatment of some affected individuals remains challenging. Challenges are also posed by the intratumoural heterogeneity of biomarkers. Furthermore, preclinical models of Wilms tumour, from cell lines to organoid cultures, have evolved. Despite these many achievements, much still remains to be discovered: further molecular understanding of relapse in Wilms tumour and of the multiple origins of bilateral Wilms tumour are two examples of areas under active investigation. International collaboration, especially when large tumour series are required to obtain robust data, will help to answer some of the remaining unresolved questions.

Retinoic acid promotes differentiation of WiT49- but not of CCG99-11 Wilms tumour cells

BACKGROUND

Most children with Wilms tumour are successfully treated with multidrug chemotherapy and surgery. These treatments cause severe side effects for the patients, an issue that needs to be addressed by exploring other treatment options with less or no side effects. One option is to complement current therapies with agents that could potentially induce tumour cell differentiation, for example retinoic acid (RA).

AIMS

To facilitate quick assessment of an agent's effect on Wilms tumour differentiation by a rapid in vitro model system.

METHODS AND RESULTS

Here WiT49 and CCG99-11 Wilms tumour cells were treated with 10 μM RA for 72 h or 9 days. Cultured cells were scraped off from Petri dishes, pelleted and embedded in paraffin in the same way as clinical tumour specimens are preserved. Cell morphology and differentiation were evaluated by analyses of haematoxylin eosin (H&E) and immunohistochemical stainings. Based on H&E, WT1 and CKAE1/3 stainings, RA treatment induced further epithelial differentiation of WiT49 cells, whereas there was no sign of induced maturation in CCG99-11 cells. Ki67 staining showed that RA inhibited cell proliferation in both cell lines.

CONCLUSIONS

Our study shows that in vitro culturing of WiT49 and CCG99-11 cells, followed by pelleting and paraffin embedding of cell pellets, could aid in a quick evaluation of potential differentiating agents against Wilms tumour. In addition, our results strengthen previous results that retinoic acid could be a potential complement to regular Wilms tumour treatment.

The epithelial splicing regulator ESRP2 is epigenetically repressed by DNA hypermethylation in Wilms tumour and acts as a tumour suppressor

Wilms tumour (WT), an embryonal kidney cancer, has been extensively characterised for genetic and epigenetic alterations, but a proportion of WTs still lack identifiable abnormalities. To uncover DNA methylation changes critical for WT pathogenesis, we compared the epigenome of foetal kidney with two WT cell lines, filtering our results to remove common cancer-associated epigenetic changes and to enrich for genes involved in early kidney development. This identified four hypermethylated genes, of which ESRP2 (epithelial splicing regulatory protein 2) was the most promising for further study. ESRP2 was commonly repressed by DNA methylation in WT, and this occurred early in WT development (in nephrogenic rests). ESRP2 expression was reactivated by DNA methyltransferase inhibition in WT cell lines. When ESRP2 was overexpressed in WT cell lines, it inhibited cellular proliferation in vitro, and in vivo it suppressed tumour growth of orthotopic xenografts in nude mice. RNA-seq of the ESRP2-expressing WT cell lines identified several novel splicing targets. We propose a model in which epigenetic inactivation of ESRP2 disrupts the mesenchymal to epithelial transition in early kidney development to generate WT.

Targeting the HIF-1α-IGFBP2 axis therapeutically reduces IGF1-AKT signaling and blocks the growth and metastasis of relapsed anaplastic Wilms tumor

For patients with anaplastic Wilms tumor (WiT), metastasis and recurrence are common, and prognosis is generally poor. Novel therapies are needed to improve outcomes for patients with this high-risk WiT. A potential contributor to WiT development is constitutive activation of AKT by insulin-like growth factor 1 (IGF1) and its receptor (IGF1R) signaling pathway, but the complete underlying mechanism remains unclear. Here, we demonstrate that the hypoxia-inducible factor 1α (HIF-1α)-IGF binding protein 2 (IGFBP2) axis and the tumor-specific IGF1A are key players for constitutive activation of IGF1-AKT signaling leading to the tumor malignancy. HIF-1α and IGFBP2 are highly expressed in a majority of WiT patient samples. Deficiency of either HIF-1α or IGFBP2 or IGF1 in the tumor cells significantly impairs tumor growth and nearly abrogates metastasis in xenografted mice. Pharmacologic targeting of HIF-1α by echinomycin delivered via nanoliposomes can efficiently restrain growth and metastasis of patient-derived relapsed anaplastic WiT xenografts. Liposomal echinomycin is more potent and effective in inhibiting WiT growth than vincristine in an anaplastic WiT mouse model, and eliminates metastasis by suppressing HIF-1α targets and the HIF-1α-IGFBP2 axis, which governs IGF1-AKT signaling.

Decoding molecular interplay between RUNX1 and FOXO3a underlying the pulsatile IGF1R expression during acquirement of chemoresistance

Hyperactive Insulin like growth factor-1-receptor (IGF1R) signalling is associated with development of therapy resistance in many cancers. We recently reported a pulsatile nature of IGF1R during acquirement of platinum-taxol resistance in Epithelial Ovarian Cancer (EOC) cells and a therapy induced upregulation in IGF1R expression in tumors of a small cohort of high grade serous EOC patients. Here, we report Runt-related transcription factor 1 (RUNX1) as a novel transcriptional regulator which along with another known regulator Forkhead Box O3 (FOXO3a), drives the dynamic modulation of IGF1R expression during platinum-taxol resistance development in EOC cells. RUNX1-FOXO3a cooperatively bind to IGF1R promoter and produce a transcriptional surge during onset of resistance and such co-operativity falls apart when cells attain maximal resistance resulting in decreased IGF1R expression. The intriguing descending trend in IGF1R and FOXO3a expressions is caused by a Protein Kinase B (AKT)-FOXO3a negative feedback loop exclusively present in the highly resistant cells eliciting the pulsatile behaviour of IGF1R and FOXO3a. In vivo molecular imaging revealed that RUNX1 inhibition causes significant attenuation of the IGF1R promoter activity, decreased tumorigenicity and enhanced drug sensitivity of tumors of early resistant cells. Altogether our findings delineate a dynamic interplay between several molecular regulators driving pulsatile IGF1R expression and identify a new avenue for targeting EOC through RUNX1-IGF1R axis during acquirement of chemoresistance.

Immune expression in children with Wilms tumor: a pilot study

BACKGROUND

Given improvements in multimodality therapy, survival among children with Wilms tumor (WT) exceeds 90%. However, 15% of children with favorable histology and 50% of children with anaplastic WT experience recurrence or progression. Of patients with advanced disease, only 50% survive to adulthood. In adult malignancies (including renal tumors), patient survival has improved with the advent of immunotherapy. However, little is known about the immune microenvironment of WT, making the potential role of immunotherapy unclear.

OBJECTIVE

The objective of the study is to perform an exploratory, descriptive analysis of the immune milieu in WT.

STUDY DESIGN

Between 2016 and 2017, all pediatric patients with WT, some of whom received neoadjuvant chemotherapy, underwent ex vivo wedge biopsy at the time of nephrectomy. The fresh tumor tissue and peripheral blood samples were analyzed for infiltrating immune infiltrate and effector cells using flow cytometry. Immunohistochemistry was performed for CD4, CD8, and PD-L1 expression. Matched blood samples were obtained for each patient, and circulating immune cells were analyzed by flow cytometry.

RESULTS

A total of six patients were enrolled. One patient with neuroblastoma was excluded. The remaining five patients included the following: two with unilateral WT (resected before chemotherapy), two with bilateral WT (resected after neoadjuvant chemotherapy), and one with Denys-Drash syndrome, end-stage renal disease, and history of WT in the contralateral kidney. Immune analysis showed that WT were infiltrated by immune cells regardless of chemotherapy status. CD8 and CD4 T cells were present in the tumor tissue and exhibited an activated phenotype. Elevated levels of natural killer (NK) cells were observed in the tumors (Figure). Immune checkpoint PD-L1 was also found expressed in one of the tumors stained.

DISCUSSION

In this pilot study, it was found that WTs were infiltrated by immune cells (CD45+) both before and after chemotherapy. Elevated levels of NK cells infiltrating the tumor specimens, which were quantitatively increased compared with levels of NK cells circulating in the blood, were noted. T cells, particularly CD4+ and CD8+ T cells, were present in tumor specimens. Tumor-infiltrating CD4 and CD8 T cells displayed an activated phenotype as defined by increased expression of human leukocyte antigen-DR isotype (HLA-DR), programmed cell death protein 1 (PD1), and CD57. Together, these findings suggest that WT microenvironment is immune engaged and may be susceptible to immunotherapy similar to other malignancies.

CONCLUSIONS

These pilot data suggest an immune-engaged tumor microenvironment is present within WT. This implies that WT may be susceptible to immunotherapy similar to adult renal tumors and other adult malignancies. Follow-up studies are currently underway.

17β-Estradiol promotes endometrial cancer proliferation and invasion through IL-6 pathway

Accumulating evidence revealed that the leading risk factor of endometrial cancer is exposure to endogenous and exogenous estrogens, while the exact mechanism underlying estrogen contribution to endometrial cancer progression has not been elucidated clearly. Interleukin (IL)-6 has been verified to be critical for tumor progression in several human cancers. In this study, we provided evidence that 17β-estradiol (E2) could significantly promote endometrial cancer cells viability, migration and invasion through activation of IL-6 pathway, which involved in its downstream pathway and target genes (p-Stat3, Bcl-2, Mcl-1, cyclin D1 and MMP2). Meanwhile, utilization of IL-6-neutralizing antibody could partially attenuate the increased cancer growth and invasion abilities in Ishikawa and RL95-2 endometrial cancer cell lines and an orthotopic endometrial cancer model. We established a causative link between estrogen and IL-6 signaling activation in the development of endometrial cancer. The molecular mechanism defined in this study provided the evidence that E2 promotes endometrial carcinoma progression via activating the IL-6 pathway, indicating that interruption of IL-6 might be an essential therapeutic strategy in estrogen-dependent endometrial cancer.

miR-140-5p could suppress tumor proliferation and progression by targeting TGFBRI/SMAD2/3 and IGF-1R/AKT signaling pathways in Wilms' tumor

Background

Wilms’ tumor is also called nephroblastoma and is the most common pediatric renal cancer. Several genetic and epigenetic factors have been found to account for the development of Wilms’ tumor. MiRNAs play important roles in this tumorigenic process. In the present study, we aimed to investigate the role of miR-140-5p in nephroblastoma by identifying its targets, as well as its underlying molecular mechanism of action.

Methods

The miRNA expression profile of nephroblastoma samples was investigated and the targets of miR-140-5p were predicted and validated using the miRNA luciferase reporter method. Moreover, the roles of miR-140-5p in regulating nephroblastoma cell proliferation, migration and cell cycle were analyzed by the CCK8, migration and flow cytometry assays, respectively. The downstream protein of the direct target of miR-140-5p was also identified.

Results

miR-140-5p was downregulated in Wilms’ tumor tissues, whereas in the nephroblastoma cell lines G401 and WT-CLS1 that exhibited high levels of miRNA-140-5p, inhibition of cellular proliferation and metastasis were noted as well as cell cycle arrest at the G1/S phase. TGFBRI and IGF1R were identified as direct target genes for miRNA-140-5p. In addition, SMAD2/3 and p-AKT were regulated by TGFBRI and IGF1R separately and participated in the miRNA-140-5p regulatory network. Ectopic expression of TGFBR1 and IGF-1R could abrogate the inhibitory effect of miR-140-5p.

Conclusion

We demonstrated that miRNA-140-5p participates in the progression of Wilms’ tumor by targeting the TGFBRI/SMAD2/3 and the IGF-1R/AKT signaling pathways.

The Iroquois homeobox proteins IRX3 and IRX5 have distinct roles in Wilms tumour development and human nephrogenesis

Wilms tumour is a paediatric malignancy with features of halted kidney development. Here, we demonstrate that the Iroquois homeobox genes IRX3 and IRX5 are essential for mammalian nephrogenesis and govern the differentiation of Wilms tumour. Knock‐out Irx3⁻/Irx5⁻ mice showed a strongly reduced embryonic nephron formation. In human foetal kidney and Wilms tumour, IRX5 expression was already activated in early proliferative blastema, whereas IRX3 protein levels peaked at tubular differentiation. Accordingly, an orthotopic xenograft mouse model of Wilms tumour showed that IRX3^−/− cells formed bulky renal tumours dominated by immature mesenchyme and active canonical WNT/β‐catenin‐signalling. In contrast, IRX5^−/− cells displayed activation of Hippo and non‐canonical WNT‐signalling and generated small tumours with abundant tubulogenesis. Our findings suggest that promotion of IRX3 signalling or inhibition of IRX5 signalling could be a route towards differentiation therapy for Wilms tumour, in which WNT5A is a candidate molecule for enforced tubular maturation. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Mutations in microRNA processing genes in Wilms tumors derepress the IGF2 regulator PLAG1

Many childhood Wilms tumors are driven by mutations in the microRNA biogenesis machinery, but the mechanism by which these mutations drive tumorigenesis is unknown. Here we show that the transcription factor pleomorphic adenoma gene 1 (PLAG1) is a microRNA target gene that is overexpressed in Wilms tumors with mutations in microRNA processing genes. Wilms tumors can also overexpress PLAG1 through copy number alterations, and PLAG1 expression correlates with prognosis in Wilms tumors. PLAG1 overexpression accelerates growth of Wilms tumor cells in vitro and induces neoplastic growth in the developing mouse kidney in vivo. In both settings, PLAG1 transactivates insulin-like growth factor 2 (IGF2), a key Wilms tumor oncogene, and drives mammalian target of rapamycin complex 1 (mTORC1) signaling. These data link microRNA impairment to the PLAG1-IGF2 pathway, providing new insight into the manner in which common Wilms tumor mutations drive disease pathogenesis.

Pre-clinical imaging of transgenic mouse models of neuroblastoma using a dedicated 3-element solenoid coil on a clinical 3T platform

BACKGROUND

The use of clinical MRI scanners to conduct pre-clinical research facilitates comparisons with clinical studies. Here the utility and sensitivity of anatomical and functional MRI data/biomarkers acquired from transgenic mouse models of neuroblastoma using a dedicated radiofrequency (RF) coil on a clinical 3T scanner was evaluated.

METHODS

Multiparametric MRI of transgenic mice bearing abdominal neuroblastomas was performed at 3T, and data cross-referenced to that acquired from the same mice on a pre-clinical 7T MRI system. T2-weighted imaging, quantitation of the native longitudinal relaxation time (T1) and the transverse relaxation rate (R2*), and dynamic contrast-enhanced (DCE)-MRI, was used to assess tumour volume, phenotype and response to cyclophosphamide or cabozantinib.

RESULTS

Excellent T2-weighted image contrast enabled clear tumour delineation at 3T. Significant correlations of tumour volume (R=0.98, P<0.0001) and R2* (R=0.87, P<0.002) measured at 3 and 7T were established. Mice with neuroblastomas harbouring the anaplastic lymphoma kinase mutation exhibited a significantly slower R2* (P<0.001), consistent with impaired tumour perfusion. DCE-MRI was performed simultaneously on three transgenic mice, yielding estimates of Ktrans for each tumour (median Ktrans values of 0.202, 0.168 and 0.114 min-1). Cyclophosphamide elicited a significant reduction in both tumour burden (P<0.002) and native T1 (P<0.01), whereas cabozantinib induced significant (P<0.01) tumour growth delay.

CONCLUSIONS

Simultaneous multiparametric MRI of multiple tumour-bearing animals using this coil arrangement at 3T can provide high efficiency/throughput for both phenotypic characterisation and evaluation of novel therapeutics, and facilitate the introduction of functional MRI biomarkers into aligned imaging-embedded clinical trials.

Kinase inhibitors of the IGF-1R as a potential therapeutic agent for rheumatoid arthritis

We have previously shown that the inhibition of connective tissue growth factor (CTGF) is a potential therapeutic strategy against rheumatoid arthritis (RA). CTGF consists of four distinct modules, including the insulin-like growth factor binding protein (IGFBP). In serum, insulin-like growth factors (IGFs) bind IGFBPs, interact with the IGF-1 receptor (IGF-1 R), and regulate anabolic effects and bone metabolism. We investigated the correlation between IGF-1 and the pathogenesis of RA, and the inhibitory effect on osteoclastogenesis and angiogenesis of the small molecular weight kinase inhibitor of the IGF-1 R, NVP-AEW541, against pathogenesis of RA in vitro. Cell proliferation was evaluated by cell count and immunoblotting. The expression of IGF-1 and IGF-1 R was evaluated by RT-PCR. Osteoclastogenesis was evaluated using tartrate-resistant acid phosphatase staining, a bone resorption assay, and osteoclast-specific enzyme production. Angiogenesis was evaluated by a tube formation assay using human umbilical vein endothelial cells (HUVECs). The proliferation of MH7A cells was found to be inhibited in the presence of NVP-AEW541, and the phosphorylation of extracellular signal-regulated kinase (ERK) and Akt was downregulated in MH7A cells. IGF-1 and IGF-1 R mRNA expression levels were upregulated during formation of M-colony stimulating factor (M-CSF) and receptor activator of NF-κB ligand (RANKL)-mediated osteoclast formation. Moreover, osteoclastogenesis was suppressed in the presence of NVP-AEW541. The formation of the tubular network was enhanced by IGF-1, and this effect was neutralized by NVP-ARE541. Our findings suggest that NVP-AEW541 may be utilized as a potential therapeutic agent in the treatment of RA.

Functional KRAS mutations and a potential role for PI3K/AKT activation in Wilms tumors

Wilms tumor (WT) is the most common renal neoplasm of childhood and affects 1 in 10 000 children aged less than 15 years. These embryonal tumors are thought to arise from primitive nephrogenic rests that derive from the metanephric mesenchyme during kidney development and are characterized partly by increased Wnt/β-catenin signaling. We previously showed that coordinate activation of Ras and β-catenin accelerates the growth and metastatic progression of a murine WT model. Here, we show that activating KRAS mutations can be found in human WT. In addition, high levels of phosphorylated AKT are present in the majority of WT. We further show in a mouse model and in renal epithelial cells that Ras cooperates with β-catenin to drive metastatic disease progression and promotes in vitro tumor cell growth, migration, and colony formation in soft agar. Cellular transformation and metastatic disease progression of WT cells are in part dependent on PI3K/AKT activation and are inhibited via pharmacological inhibition of this pathway. Our studies suggest both KRAS mutations and AKT activation are present in WT and may represent novel therapeutic targets for this disease.

Biology and treatment of renal tumours in childhood

In Europe, almost 1000 children are diagnosed with a malignant renal tumour each year. The vast majority of cases are nephroblastoma, also known as Wilms' tumour (WT). Most children are treated according to Société Internationale d'Oncologie Pédiatrique Renal Tumour Study Group (SIOP-RTSG) protocols with pre-operative chemotherapy, surgery, and post-operative treatment dependent on stage and histology. Overall survival approaches 90%, but a subgroup of WT, with high-risk histology and/or relapsed disease, still have a much poorer prognosis. Outcome is similarly poor for the rare non-WT, particularly for malignant rhabdoid tumour of the kidney, metastatic clear cell sarcoma of the kidney (CCSK), and metastatic renal cell carcinoma (RCC). Improving outcome and long-term quality of life requires more accurate risk stratification through biological insights. Biomarkers are also needed to signpost potential targeted therapies for high-risk subgroups. Our understanding of Wilms' tumourigenesis is evolving and several signalling pathways, microRNA processing and epigenetics are now known to play pivotal roles. Most rhabdoid tumours display somatic and/or germline mutations in the SMARCB1 gene, whereas CCSK and paediatric RCC reveal a more varied genetic basis, including characteristic translocations. Conducting early-phase trials of targeted therapies is challenging due to the scarcity of patients with refractory or relapsed disease, the rapid progression of relapse and the genetic heterogeneity of the tumours with a low prevalence of individual somatic mutations. A further consideration in improving population survival rates is the geographical variation in outcomes across Europe. This review provides a comprehensive overview of the current biological knowledge of childhood renal tumours alongside the progress achieved through international collaboration. Ongoing collaboration is needed to ensure consistency of outcomes through standardised diagnostics and treatment and incorporation of biomarker research. Together, these objectives constitute the rationale for the forthcoming SIOP-RTSG 'UMBRELLA' study.

Establishment of a Conditionally Immortalized Wilms Tumor Cell Line with a Homozygous WT1 Deletion within a Heterozygous 11p13 Deletion and UPD Limited to 11p15

We describe a stromal predominant Wilms tumor with focal anaplasia and a complex, tumor specific chromosome 11 aberration: a homozygous deletion of the entire WT1 gene within a heterozygous 11p13 deletion and an additional region of uniparental disomy (UPD) limited to 11p15.5-p15.2 including the IGF2 gene. The tumor carried a heterozygous p.T41A mutation in CTNNB1. Cells established from the tumor carried the same chromosome 11 aberration, but a different, homozygous p.S45Δ CTNNB1 mutation. Uniparental disomy (UPD) 3p21.3pter lead to the homozygous CTNNB1 mutation. The tumor cell line was immortalized using the catalytic subunit of human telomerase (hTERT) in conjunction with a novel thermolabile mutant (U19dl89-97tsA58) of SV40 large T antigen (LT). This cell line is cytogenetically stable and can be grown indefinitely representing a valuable tool to study the effect of a complete lack of WT1 in tumor cells. The origin/fate of Wilms tumors with WT1 mutations is currently poorly defined. Here we studied the expression of several genes expressed in early kidney development, e.g. FOXD1, PAX3, SIX1, OSR1, OSR2 and MEIS1 and show that these are expressed at similar levels in the parental and the immortalized Wilms10 cells. In addition the limited potential for muscle/ osteogenic/ adipogenic differentiation similar to all other WT1 mutant cell lines is also observed in the Wilms10 tumor cell line and this is retained in the immortalized cells. In summary these Wilms10 cells are a valuable model system for functional studies of WT1 mutant cells.

Context Sensitive Modeling of Cancer Drug Sensitivity

Recent screening of drug sensitivity in large panels of cancer cell lines provides a valuable resource towards developing algorithms that predict drug response. Since more samples provide increased statistical power, most approaches to prediction of drug sensitivity pool multiple cancer types together without distinction. However, pan-cancer results can be misleading due to the confounding effects of tissues or cancer subtypes. On the other hand, independent analysis for each cancer-type is hampered by small sample size. To balance this trade-off, we present CHER (Contextual Heterogeneity Enabled Regression), an algorithm that builds predictive models for drug sensitivity by selecting predictive genomic features and deciding which ones should-and should not-be shared across different cancers, tissues and drugs. CHER provides significantly more accurate models of drug sensitivity than comparable elastic-net-based models. Moreover, CHER provides better insight into the underlying biological processes by finding a sparse set of shared and type-specific genomic features.

Clinical next-generation sequencing reveals aggressive cancer biology in adolescent and young adult patients

BACKGROUND

The aggressive biology of cancers arising in adolescent and young adult (AYA; ages 15-39 years) patients is thought to contribute to poor survival outcomes.

METHODS

We used clinical next-generation sequencing (NGS) results to examine the molecular alterations and diverse biology of cancer in AYA patients referred to the Phase 1 program at UT MD Anderson Cancer Center.

RESULTS

Among the 28 patients analyzed (14 female and 14 male), 12 had pediatric-type cancers, six had adult-type cancers, and ten had orphan cancers. Unique, hitherto unreported aberrations were identified in all types of cancers. Aberrations in TP53, NKX2-1, KRAS, CDKN2A, MDM4, MCL1, MYC, BCL2L2, and RB1 were demonstrated across all tumor types. Five patients harbored TP53 aberrations; three patients harbored MYC, MCL1, and CDKN2A aberrations; and two patients harbored NKX2-1, KRAS, MDM4, BCL2L2, and RB1 alterations. Several patients had multiple aberrations; a patient with wild-type gastrointestinal stromal tumor harbored five alterations (MDM4, MCL1, KIT, AKT3, and PDGRFA).

CONCLUSIONS

This preliminary report of NGS of cancer in AYA patients reveals diverse and unique aberrations. Further molecular profiling and a deeper understanding of the biology of these unique aberrations are warranted and may lead to targeted therapeutic interventions.

Orthotopic Wilms tumor xenografts derived from cell lines reflect limited aspects of tumor morphology and clinical characteristics

BACKGROUND

Wilms tumor (WT) is a pediatric tumor of the kidney, the treatment of which includes heavy chemotherapy. Affected children would likely benefit from more targeted therapies with limited side effects. Establishment of relevant orthotopic WT xenografts is important to better understand mechanisms of WT growth and for preclinical drug testing.

PROCEDURE

Here we established and characterized orthotopic xenografts from WT cell lines WiT49, CCG-99-11, and WT-CLS1 to ascertain in what aspects each of them recapitulated WT histology, immunophenotype, invasion, and metastatic spread.

RESULTS

WiT49 xenografts recapitulated near triphasic WTs with clear WT1 staining and anaplastic features, but with tumor restricted to the kidney. On the contrary both CCG-99-11 and WT-CLS1 xenografts conveyed metastatic disease. CCG-99-11 showed a blastemal phenotype whereas WT-CLS1 xenografts did not properly reflect any specific WT subtype.

CONCLUSIONS

From the three tested cell lines, orthotopic WiT49 xenografts best reflect the triphasic pattern of classical WT.

The IGF signalling pathway in Wilms tumours--a report from the ENCCA Renal Tumours Biology-driven drug development workshop

It is hypothesised that Wilms tumour (WT) results from aberrant renal development due to its embryonic morphology, associated undifferentiated precursor lesions (termed nephrogenic rests) and embryonic kidney-like chromatin and gene expression profiles. From the study of overgrowth syndrome-associated WT, germline dysregulation was identified in the imprinted region at 11p15 affecting imprinted genes IGF2 and H19. This is also detected in ~70% sporadic cases, making this the most common somatic molecular aberration in WT. This review summarises the critical discussion at an international workshop held under the auspices of The European Network for Cancer Research in Children and Adolescents (ENCCA) consortium, where the potential for drug development to target IGF2 and the WT epigenome was debated. Here, we consider current cancer treatments which include targeting the IGF pathway and the use of methylation agents alone or in combination with other drugs in clinical trials of paediatric cancers. Finally, we discuss the possibility of the use of these drugs to treat patients with WT.

Activation of Ras overcomes B-cell tolerance to promote differentiation of autoreactive B cells and production of autoantibodies

Newly generated immature B cells are selected to enter the peripheral mature B-cell pool only if they do not bind (or bind limited amount of) self-antigen. We previously suggested that this selection relies on basal extracellular signal-regulated kinase (Erk) activation mediated by tonic B-cell antigen receptor (BCR) signaling and that this signal can be replaced by an active rat sarcoma (Ras), which are small GTPase proteins. In this study we compared the activity of Ras and Erk in nonautoreactive and autoreactive immature B cells and investigated whether activation of Ras can break tolerance. Our results demonstrate lower levels of active Erk and Ras in autoreactive immature B cells, although this is evident only when these cells display medium/high avidity for self-antigen. Basal activation of Erk in immature B cells is proportional to surface IgM and dependent on sarcoma family kinases, whereas it is independent of B-cell activating factor, IFN, and Toll-like receptor signaling. Ectopic expression of the constitutively active mutant Ras form N-RasD12 in autoreactive cells raises active Erk, halts receptor editing via PI3 kinase, and promotes differentiation via Erk, breaking central tolerance. Moreover, when B cells coexpress autoreactive and nonautoreactive BCRs, N-RasD12 leads also to a break in peripheral tolerance with the production of autoantibodies. Our findings indicate that in immature B cells, basal activation of Ras and Erk are controlled by tonic BCR signaling, and that positive changes in Ras activity can lead to a break in both central and peripheral B-cell tolerance.

IGF-1R inhibition enhances radiosensitivity and delays double-strand break repair by both non-homologous end-joining and homologous recombination

Inhibition of type 1 insulin-like growth factor receptor (IGF-1R) enhances tumor cell sensitivity to ionizing radiation. It is not clear how this effect is mediated, nor whether this approach can be applied effectively in the clinic. We previously showed that IGF-1R depletion delays repair of radiation-induced DNA double-strand breaks (DSBs), unlikely to be explained entirely by reduction in homologous recombination (HR) repair. The current study tested the hypothesis that IGF-1R inhibition induces a repair defect that involves non-homologous end joining (NHEJ). IGF-1R inhibitor AZ12253801 blocked cell survival and radiosensitized IGF-1R-overexpressing murine fibroblasts but not isogenic IGF-1R-null cells, supporting specificity for IGF-1R. IGF-1R inhibition enhanced radiosensitivity in DU145, PC3 and 22Rv1 prostate cancer cells, comparable to effects of Ataxia Telangiectasia Mutated inhibition. AZ12253801-treated DU145 cells showed delayed resolution of γH2AX foci, apparent within 1 h of irradiation and persisting for 24 h. In contrast, IGF-1R inhibition did not influence radiosensitivity or γH2AX focus resolution in LNCaP-LN3 cells, suggesting that radiosensitization tracks with the ability of IGF-1R to influence DSB repair. To differentiate effects on repair from growth and cell-survival responses, we tested AZ12253801 in DU145 cells at sub-SF50 concentrations that had no early (⩽48 h) effects on cell cycle distribution or apoptosis induction. Irradiated cultures contained abnormal mitoses, and after 5 days IGF-1R-inhibited cells showed enhanced radiation-induced polyploidy and nuclear fragmentation, consistent with the consequences of entry into mitosis with incompletely repaired DNA. AZ12253801 radiosensitized DNA-dependent protein kinase (DNA-PK)-proficient but not DNA-PK-deficient glioblastoma cells, and did not radiosensitize DNA-PK-inhibited DU145 cells, suggesting that in the context of DSB repair, IGF-1R functions in the same pathway as DNA-PK. Finally, IGF-1R inhibition attenuated repair by both NHEJ and HR in HEK293 reporter assays. These data indicate that IGF-1R influences DSB repair by both major DSB repair pathways, findings that may inform clinical application of this approach.

Final height and IGF1 in adult survivors of Wilms tumour

OBJECTIVE

One-sided nephrectomy is followed by increased levels of IGF1, associated with linear growth during childhood. The aim was to evaluate final height and IGF1 levels in nephrectomized Wilms tumour survivors when compared with healthy Dutch references and survivors of other cancer types.

DESIGN

Cross-sectional retrospective study.

METHODS

Data of 575 adult childhood cancer survivors were analysed. median follow-up time was 17.8 (range 5.048.8) years. Analysis of (co)variance was performed to evaluate differences between subgroups: nephrectomized Wilms survivors treated with or without abdominal irradiation (n=41 and n=36) and survivors of other cancer types treated with or without irradiation involving the cranium, abdomen or total body (n=149 and n=349). Main outcome measures were IGF1 and height, expressed as SDS.

RESULTS

After adjustment for age at diagnosis, former corticosteroid treatment and renal impairment, height SDS in non-irradiated nephrectomized Wilms survivors was significantly higher than that in non-irradiated survivors of other cancer types (estimated mean SDS -0.09 vs -0.49, P=0.044), abdominal irradiated survivors (SDS -0.70, P=0.015) and other irradiated survivors (SDS -1.47, P<0.001). Non-irradiated nephrectomized Wilms tumour survivors had significantly higher IGF1 SDS than other irradiated survivors (estimated mean SDS -0.05 vs -1.36, P<0.001 and 0.11 vs 1.37, P<0.001), while there was no significant difference with the other two subgroups.

CONCLUSIONS

Adult survivors of Wilms tumour showed better attainment of final height and relatively higher IGF1 levels than those of other cancer types who had significantly shorter stature and lower IGF1 levels than Dutch references.

Type 1 insulin-like growth factor receptor targeted therapies in pediatric cancer

Data from over 20 years ago demonstrated potential use for insulin-like growth factor (IGF) signaling modulators, specifically with IGF-1R antagonists, in a variety of pediatric and adolescent cancers, particularly in sarcomas. However, in spite of promising preclinical data, IGF-1R inhibitors have not had the success as single agents that was originally hoped for in clinical trials. Several potential mechanisms exist by which tumors are resistant to IGF-1R inhibitors. Notably, these resistance mechanisms are currently best understood in Ewing sarcoma and alveolar rhabdomyosarcoma. Various treatment schema have been proposed as a potential way to overcome this resistance. The use of IGF-1R inhibitors, mechanisms of resistance, and current ongoing clinical studies using IGF-1R inhibitors in pediatric cancers are reviewed here.