Correlation of modified Shimada classification with MYCN and 1p36 status detected by fluorescence in situ hybridization in neuroblastoma

Genetics of congenital solid tumors

When we discuss the genetics of tumors, we cannot fail to remember that in the second decade of the twentieth century, more precisely in 1914, Theodore Boveri defined for the first time the chromosomal bases of cancer. In the last 30 years, progresses in genetics have only confirmed Boveri's remarkable predictions made more than 80 years ago. Before the cloning of the retinoblastoma 1 (RB1) gene, the existence of a genetic component in most, if not all, solid childhood tumors were well known. The existence of familial tumor aggregations has been found much more frequently than researchers expected to find at random. Sometimes, the demonstration of this family predisposition was very difficult, because the survival of children diagnosed as having a certain tumor, up to an age at which reproduction and procreation is possible, was very rare. In recent years, advances in the diagnosis and treatment of these diseases have made it possible for these children to survive until the age when they were able to start their own families, including the ability to procreate. Four distinct groups of so-called cancer genes have been identified: oncogenes, which promote tumor cell proliferation; tumor suppressor genes, which inhibit this growth/proliferation; anti-mutational genes, with a role in deoxyribonucleic acid (DNA) stability; and micro-ribonucleic acid (miRNA) genes, with a role in the posttranscriptional process.

CT-Based Radiomics Signature With Machine Learning Predicts MYCN Amplification in Pediatric Abdominal Neuroblastoma

Purpose

MYCN amplification plays a critical role in defining high-risk subgroup of patients with neuroblastoma. We aimed to develop and validate the CT-based machine learning models for predicting MYCN amplification in pediatric abdominal neuroblastoma.

Methods

A total of 172 patients with MYCN amplified (n = 47) and non-amplified (n = 125) were enrolled. The cohort was randomly stratified sampling into training and testing groups. Clinicopathological parameters and radiographic features were selected to construct the clinical predictive model. The regions of interest (ROIs) were segmented on three-phrase CT images to extract first-, second- and higher-order radiomics features. The ICCs, mRMR and LASSO methods were used for dimensionality reduction. The selected features from the training group were used to establish radiomics models using Logistic regression, Support Vector Machine (SVM), Bayes and Random Forest methods. The performance of four different radiomics models was evaluated according to the area under the receiver operator characteristic (ROC) curve (AUC), and then compared by Delong test. The nomogram incorporated of clinicopathological parameters, radiographic features and radiomics signature was developed through multivariate logistic regression. Finally, the predictive performance of the clinical model, radiomics models, and nomogram was evaluated in both training and testing groups.

Results

In total, 1,218 radiomics features were extracted from the ROIs on three-phrase CT images, and then 14 optimal features, including one original first-order feature and eight wavelet-transformed features and five LoG-transformed features, were identified and selected to construct the radiomics models. In the training group, the AUC of the Logistic, SVM, Bayes and Random Forest model was 0.940, 0.940, 0.780 and 0.927, respectively, and the corresponding AUC in the testing group was 0.909, 0.909, 0.729, 0.851, respectively. There was no significant difference among the Logistic, SVM and Random Forest model, but all better than the Bayes model (p <0.005). The predictive performance of the Logistic radiomics model based on three-phrase is similar to nomogram, but both better than the clinical model and radiomics model based on single venous phase.

Conclusion

The CT-based radiomics signature is able to predict MYCN amplification of pediatric abdominal NB with high accuracy based on SVM, Logistic and Random Forest classifiers, while Bayes classifier yields lower predictive performance. When combined with clinical and radiographic qualitative features, the clinics-radiomics nomogram can improve the performance of predicting MYCN amplification.

Expression of BARD1 β Isoform in Selected Pediatric Tumors

Currently, many new possible biomarkers and mechanisms are being searched and tested to analyse pathobiology of pediatric tumours for the development of new treatments. One such candidate molecular factor is BARD1 (BRCA1 Associated RING Domain 1)—a tumour-suppressing gene involved in cell cycle control and genome stability, engaged in several types of adult-type tumours. The data on BARD1 significance in childhood cancer is limited. This study determines the expression level of BARD1 and its isoform beta (β) in three different histogenetic groups of pediatric cancer—neuroblastic tumours, and for the first time in chosen germ cell tumours (GCT), and rhabdomyosarcoma (RMS), using the qPCR method. We found higher expression of beta isoform in tumour compared to healthy tissue with no such changes concerning BARD1 full-length. Additionally, differences in expression of BARD1 β between histological types of neuroblastic tumours were observed, with higher levels in ganglioneuroblastoma and ganglioneuroma. Furthermore, a higher expression of BARD1 β characterized yolk sac tumours (GCT type) and RMS when comparing with non-neoplastic tissue. These tumours also showed a high expression of the TERT (Telomerase Reverse Transcriptase) gene. In two RMS cases we found deep decrease of BARD1 β in post-chemotherapy samples. This work supports the oncogenicity of the beta isoform in pediatric tumours, as well as demonstrates the differences in its expression depending on the histological type of neoplasm, and the level of maturation in neuroblastic tumours.

MYCN is amplified during S phase, and c‑myb is involved in controlling MYCN expression and amplification in MYCN‑amplified neuroblastoma cell lines

Neuroblastoma derived from primitive sympathetic neural precursors is a common type of solid tumor in infants. MYCN proto-oncogene bHLH transcription factor (MYCN) amplification and 1p36 deletion are important factors associated with the poor prognosis of neuroblastoma. Expression levels of MYCN and c-MYB proto-oncogene transcription factor (c-myb) decline during the differentiation of neuroblastoma cells; E2F transcription factor 1 (E2F1) activates the MYCN promoter. However, the underlying mechanism of MYCN overexpression and amplification requires further investigation. In the present study, potential c-Myb target genes, and the effect of c-myb RNA interference (RNAi) on MYCN expression and amplification were investigated in MYCN-amplified neuroblastoma cell lines. The mRNA expression levels and MYCN gene copy number in five neuroblastoma cell lines were determined by quantitative polymerase chain reaction. In addition, variations in potential target gene expression and MYCN gene copy number between pre- and post-c-myb RNAi treatment groups in MYCN-amplified Kelly, IMR32, SIMA and MHH-NB-11 cell lines, normalized to those of non-MYCN-amplified SH-SY5Y, were examined. To determine the associations between gene expression levels and chromosomal aberrations, MYCN amplification and 1p36 alterations in interphases/metaphases were analyzed using fluorescence in situ hybridization. Statistical analyses revealed correlations between 1p36 alterations and the expression of c-myb, MYB proto-oncogene like 2 (B-myb) and cyclin dependent kinase inhibitor 1A (p21). Additionally, the results of the present study also demonstrated that c-myb may be associated with E2F1 and L3MBTL1 histone methyl-lysine binding protein (L3MBTL1) expression, and that E2F1 may contribute to MYCN, B-myb, p21 and chromatin licensing and DNA replication factor 1 (hCdt1) expression, but to the repression of geminin (GMNN). On c-myb RNAi treatment, L3MBTL1 expression was silenced, while GMNN was upregulated, indicating G₂/M arrest. In addition, MYCN gene copy number increased following treatment with c-myb RNAi. Notably, the present study also reported a 43.545% sequence identity between upstream of MYCN and Drosophila melanogaster amplification control element 3, suggesting that expression and/or amplification mechanisms of developmentally-regulated genes may be evolutionarily conserved. In conclusion, c-myb may be associated with regulating MYCN expression and amplification. c-myb, B-myb and p21 may also serve a role against chromosome 1p aberrations. Together, it was concluded that MYCN gene is amplified during S phase, potentially via a replication-based mechanism.

High incidence of MYCN amplification in a Moroccan series of neuroblastic tumors: comparison to current biological data

MYCN protooncogene status was assessed for the first time in Morocco in peripheral neuroblastic tumors, including neuroblastoma, ganglioneuroblastoma, and ganglioneuroma. Correlations with age at diagnosis, stage, mitosis-karyorrhexis index, differentiation, and Shimada histology were evaluated. Thirty-six formalin-fixed, paraffin-embedded peripheral neuroblastic tumor tissue specimens collected between 2007 and 2010 from the Pathology Department were assessed for MYCN amplification using fluorescence in situ hybridization. MYCN amplification was found in 27.8% of cases. An association of MYCN amplification with unfavorable Shimada grading, higher mitosis-karyorrhexis index, and undifferentiated morphologic phenotype was found. We found no correlation with older age, advanced stage, or the presence of metastasis. Our results suggested that the presence of MYCN amplification is a strong biological indicator of a poor outcome and aggressive disease in neuroblastoma and nodular ganglioneuroblastoma.

p53, SKP2, and DKK3 as MYCN Target Genes and Their Potential Therapeutic Significance

Neuroblastoma is the most common extra-cranial solid tumor of childhood. Despite significant advances, it currently still remains one of the most difficult childhood cancers to cure, with less than 40% of patients with high-risk disease being long-term survivors. MYCN is a proto-oncogene implicated to be directly involved in neuroblastoma development. Amplification of MYCN is associated with rapid tumor progression and poor prognosis. Novel therapeutic strategies which can improve the survival rates whilst reducing the toxicity in these patients are therefore required. Here we discuss genes regulated by MYCN in neuroblastoma, with particular reference to p53, SKP2, and DKK3 and strategies that may be employed to target them.

Acute lymphoblastic leukemia in a patient with constitutional chromosome 1pter-p36.31 duplication and 1q43-qter deletion

Chromosome 1 is the largest of all human chromosomes, containing 3141 genes. It is linked to 890 known genetic diseases including congenital hypothyroidism, hemochromatosis, and prostate cancer. Recognized deletion and duplication syndromes have been described. Deletions in the short arm (p) of the chromosome have been identified in tumors of the brain and kidneys. Duplications in the long (q) arm of the chromosome are reported in myelodysplastic syndromes. Solitary 1p36 deletion or 1q42 duplication are rarely reported entities and their associations with malignancy have not been characterized. We report a case of a child with constitutional 1pter-p36.31 duplication and 1q43-qter deletion who developed acute lymphoblastic leukemia (ALL). The patient's oncologic presentation and subsequent clinical course raise the question of the association of the underlying genetic abnormality and its malignant potential, specifically in relation to ALL. Acquired chromosome 1 deletions and duplications have been well described in other malignant diseases. Constitutional chromosome 1p duplication and 1q deletions have not been described with ALL.

Neuroblastoma and bone metastases: clinical significance and prognostic value of Dickkopf 1 plasma levels

The critical role of the Wnt pathway inhibition in sustaining the onset of bone lesions has been demonstrated in a variety of bone diseases and tumors, and it has been associated with cancer aggressiveness. We have previously demonstrated that neuroblastoma cells express Dickkopf 1 (Dkk1), an inhibitor of the canonical Wnt pathway which prevents the differentiation of bone-forming cells. Since Dkk1 is a secreted factor, it could have potential clinical application as tumor marker for detecting bone metastasis and monitoring of disease. In this study, we investigated the diagnostic and prognostic value of Dkk1 plasma levels in 92 children affected by neuroblastoma, including 32 with bone metastases. Fifty-seven children hospitalized for minor surgical problems served as control group. Circulating levels of Dkk1 were higher in healthy children than in normal adults and were comparable to those found in adult patients with aggressive tumors. No significant differences were found between neuroblastoma patients and controls and between patients with and without bone metastases. However, when only patients with metastatic neuroblastoma were considered, the highest Dkk1 levels were detected in patients that poorly responded to induction chemotherapy and in subjects with unamplified MYCN and three or more different metastatic sites. The 'Receiver Operating Characteristic' curve enabled us to identify a threshold value to distinguish patients who were unresponsive to induction treatment. The relationship between Dkk1 and drug resistance was supported by in vitro experiments, since an increased sensitivity to doxorubicin was found in neuroblastoma cells releasing low Dkk1 levels, either constitutively or experimentally following the treatment with specific siRNA. In conclusion, Dkk1 is released by neuroblastoma cells and is able to affect the balance between osteoblastogenesis and osteoclastogenesis, thus favoring the onset of osteolytic metastases. Nevertheless, Dkk1 plasma levels do not allow the detection of bone lesions in neuroblastoma but seem to have a predictive value with regard to the severity and the prognosis of the disease in a subset of patients with metastatic tumor. New knowledge on the biological role of Dkk1 in driving the natural history of neuroblastoma has to be further investigated and could help to establish specific therapeutic strategies able to target key factors of tumor progression.

Effect of cytotoxic agents and retinoic acid on Myc-N protein expression in neuroblastoma

AIM

Neuroblastoma is an important pediatric tumor in which Myc-N amplification is a well-known poor prognostic indicator. It has a great diversity in clinical behavior. The effect of pharmacologic agents used in neuroblastoma treatment on Myc-N expression is still unclear.

METHOD

We analyzed Myc-N expression changes by immunocytochemistry in Myc-N-positive Kelly human neuroblastoma cell line using retinoic acid and cytotoxic drugs (cisplatin, vincristine, cyclophosphamide, etoposide, and doxorubicin) and their combinations compared with control conditions. First, concentration of drugs were determined as LD50 doses. Kelly cells and drugs were incubated for 24 hours in 5% CO2, 37 degrees C in 96-well plates. Myc-N expression was scored semiquantitatively as negative, mild, moderate, or high positive.

RESULTS

Myc-N amplification did not change with any agent or combination. It was higher than 20 copies in all conditions. Myc-N protein expression was high in control and doxorubicin group. It was moderate in retinoic acid, cyclophosphamide, retinoic acid combined with cyclophosphamide and retinoic acid combined with doxorubicin groups. The expression was mild in cisplatin, vincristine, etoposide, retinoic acid combined with etoposide, and retinoic acid combined with cisplatin groups. Myc-N expression was negative in retinoic acid combined with vincristine group.

CONCLUSIONS

Myc-N expression is reduced with cytotoxic agents and retinoic acid in neuroblastoma although Myc-N amplification remains the same. Retinoic acid combined with vincristine is the most effective combination to reduce Myc-N expression. Our results suggest that therapeutic applications of these agents as low dose maintenance therapy might be useful.

p53 is a direct transcriptional target of MYCN in neuroblastoma

MYCN amplification occurs in approximately 25% of neuroblastomas, where it is associated with rapid tumor progression and poor prognosis. MYCN plays a paradoxical role in driving cellular proliferation and inducing apoptosis. Based on observations of nuclear p53 accumulation in neuroblastoma, we hypothesized that MYCN may regulate p53 in this setting. Immunohistochemical analysis of 82 neuroblastoma tumors showed an association of high p53 expression with MYCN expression and amplification. In a panel of 5 MYCN-amplified and 5 nonamplified neuroblastoma cell lines, and also in the Tet21N-regulatable MYCN expression system, we further documented a correlation between the expression of MYCN and p53. In MYCN-amplified neuroblastoma cell lines, MYCN knockdown decreased p53 expression. In Tet21N MYCN+ cells, higher levels of p53 transcription, mRNA, and protein were observed relative to Tet21N MYCN- cells. In chromatin immunoprecipitation and reporter gene assays, MYCN bound directly to a Myc E-Box DNA binding motif located close to the transcriptional start site within the p53 promoter, where it could initiate transcription. E-Box mutation decreased MYCN-driven transcriptional activation. Microarray analysis of Tet21N MYCN+/- cells identified several p53-regulated genes that were upregulated in the presence of MYCN, including MDM2 and PUMA, the levels of which were reduced by MYCN knockdown. We concluded that MYCN transcriptionally upregulates p53 in neuroblastoma and uses p53 to mediate a key mechanism of apoptosis.

Analysis of biological prognostic factors using tissue microarrays in neuroblastic tumors

BACKGROUND

Neuroblastic tumors (NT) are pediatric neoplasms with a heterogeneous genetic profile. They present genotypic alterations of prognostic value, the study of which is mandatory in designing therapeutic management. Tissue microarrays (TMA) from paraffin material allow the analysis of a large number of cases with minimal costs. The main purpose of the present study is to analyze specific genetic markers of neuroblastic tumors included in TMAs and determine their prognostic value. We compare the results obtained by different molecular techniques at different substrates to evaluate the feasibility of these assays.

PROCEDURE

One hundred thirty-nine samples were included in four different TMAs. We performed FISH assays to determine the status of MYCN gene, 1p36 region and 17q23 arm. The prognostic value of the genetic markers as well as the statistical correlation among clinical variables and outcome were analyzed by SPSS.

RESULTS

MYCN amplification was detected in 35.3% of the cases, whereas 1p36 deletion and 17q23 gain was observed in 46.8% and 58.3% of the cases, respectively. An adverse prognosis was noted among these patients. Other adverse factors were age (>18 months) as well as high stage of disease (stage 4). Phenotypic signs of differentiation correlated with good outcome.

CONCLUSION

Retrospective studies using paraffin-embedded tissues assembled in TMA are a useful tool for the analysis of prognostic factors in NT.

Combining anatomic and molecularly targeted imaging in the diagnosis and surveillance of embryonal tumors of the nervous and endocrine systems in children

Combining anatomical and functional imaging can improve sensitivity and accuracy of tumor diagnosis and surveillance of pediatric malignancies. MRI is the state-of-the-art modality for demonstrating the anatomical location of brain tumors with contrast enhancement adding additional information regarding whether the tumor is neuronal or glial. Addition of SPECT imaging using a peptide that targets the somatostatin receptor (Octreoscan) can now differentiate medulloblastoma from a cerebellar pilocytic astrocytoma. Combined MRI and Octreoscan is now the most sensitive and accurate imaging modality for differentiating recurrent medulloblastoma from scar tissue. CT is the most common imaging modality for demonstrating the anatomical location of tumors in the chest and abdomen. Addition of SPECT imaging with either MIBG or Octreoscan has been shown to add important diagnostic information on the nature of tumors in chest and abdomen and is often more sensitive than CT for identification of metastatic lesions in bone or liver. Combined anatomical and functional imaging is particularly helpful in neuroblastoma and in neuroendocrine tumors such as gastrinoma and carcinoid. Functional imaging with MIBG and Octreoscan is predictive of response to molecularly targeted therapy with 131I-MIBG and 90Y-DOTA-tyr3-Octreotide. Dosimetry using combined anatomical and functional imaging is being developed for patient-specific dosing of targeted radiotherapy and as an extremely sensitive monitor of response to therapy. Both MIBG and Octreotide are now being adapted to PET imaging which will greatly improve the utility of PET in medulloblastoma as well as increase the sensitivity for detection of metastatic lesions in neuroblastoma and neuroendocrine tumors.