Fast detection of MYCN copy number alterations in brain neuronal tumors by real-time PCR

Clinical Importance of Myc Family Oncogene Aberrations in Epithelial Ovarian Cancer

Background

The Myc oncogene family has been implicated in many human malignancies and is often associated with particularly aggressive disease, suggesting Myc as an attractive prognostic marker and therapeutic target. However, for epithelial ovarian cancer (EOC), there is little consensus on the incidence and clinical relevance of Myc aberrations. Here we comprehensively investigated alterations in gene copy number, expression, and activity for Myc and evaluated their clinical significance in EOC.

Methods

To address inconsistencies in the literature regarding the definition of copy number variations, we developed a novel approach using quantitative polymerase chain reaction (qPCR) coupled with a statistical algorithm to estimate objective thresholds for detecting Myc gain/amplification in large cohorts of serous (n = 150) and endometrioid (n = 80) EOC. MYC, MYCN, and MYCL1 mRNA expression and Myc activity score for each case were examined by qPCR. Kaplan–Meier and Cox-regression analyses were conducted to assess clinical significance of Myc aberrations.

Results

Using a large panel of cancer cell lines (n = 34), we validated the statistical algorithm for determining clear thresholds for Myc gain/amplification. MYC was the most predominantly amplified of the Myc oncogene family members, and high MYC mRNA expression levels were associated with amplification in EOC. However, there was no association between prognosis and increased copy number or gene expression of MYC/MYCN/MYCL1 or with a pan-Myc transcriptional activity score, in EOC, although MYC amplification was associated with late stage and high grade in endometrioid EOC.

Conclusion

A systematic and comprehensive analysis of Myc genes, transcripts, and activity levels using qPCR revealed that although such aberrations commonly occur in EOC, overall they have limited impact on outcome, suggesting that the biological relevance of Myc oncogene family members is limited to certain subsets of this disease.

Prognostic significance of MYCN gene amplification and protein expression in primary brain tumors: Astrocytoma and meningioma

BACKGROUND

Astrocytoma and meningioma are the most common primary brain tumors. MYCN as a member of MYC proto-oncogenes has recently appeared as an attractive therapeutic target. Functions of MYCN are critical for growth of nervous system and neural differentiation.

OBJECTIVE

We examined MYCN amplification and protein expression in astrocytoma and meningioma cases.

METHODS

In this study, we used real-time PCR, FISH assay and flowcytometry to analyze DNA amplification and protein expression of MYCN.

RESULTS

Among 30 samples of brain tumor, 14 cases (46.6%) revealed MYCN amplification. High-protein expression of MYCN was also observed in 43.3% of patients. There was a significant correlation between MYCN gene amplification and protein expression (r= 0.523; p= 0.003), interestingly five case showed discrepancy between the gene amplification and protein expression. Although MYCN amplification fails to show correlation with poor prognosis (p= 0.305), protein high-expression of MYCN significantly reduce disease-free survival (p= 0.019).

CONCLUSIONS

Our results challenge the concept of the neural specificity of MYCN by demonstrating contribution of MYCN in meningioma. Moreover, this study highlights the importance of research at both level of DNA and protein, to determine the biological functions and medical impacts of MYCN.

Histology and molecular aspects of central neurocytoma

Central neurocytoma (CN) is a well-differentiated tumor of neural cells occurring within the ventricles. It is composed of monomorphic cells with round, regular nuclei within clear cytoplasm and must be distinguished from other clear cell tumors. Immunohistochemical markers of CN that aid in diagnosis include synaptophysin and neuronal nuclear antigen. The molecular biology of these tumors is becoming increasingly elucidated, particularly with the use of microarray analyses. Several oncogenic pathways have been suggested by these studies. Although progress continues to be made, knowledge of CN has yet to dictate targeted therapies in treating patients with these tumors.

Low-level copy number changes of MYC genes have a prognostic impact in medulloblastoma

High-level amplifications of MYC genes are associated with poor outcomes in childhood medulloblastoma (MB). However, the occurrence of MYCN and MYCC copy number increases below the intense amplification pattern is rarely reported, and its clinical impact has not yet been determined. Here, we describe this phenomenon and its prognostic significance in a cohort of 29 MB patients. Using interphase fluorescence in situ hybridization (I-FISH), low-level copy number alterations, i.e. gain of MYCN, were shown in 5/27 (19%) samples, whereas amplification was revealed in only 1/27 (4%) samples. MYCC gain was revealed in 6/29 (21%) MB, while amplification was disclosed in only 2/29 (7%). Hyperploidy and co-incidence of gains in both MYC loci were frequently observed in samples with copy number aberrations. Survival analysis has clearly shown that MYC copy number increases are associated with lowered event-free survival and overall survival in MB. In the case of MYCN, this negative correlation was statistically significant. We conclude that limited numerical alterations in loci 2p24 (MYCN) and 8q24 (MYCC), as assessed by I-FISH, are present in MB with a higher frequency than high-level amplifications. Poor prognoses were observed in patients with copy number increases in MYC genes. Our data illustrate the importance of further investigations in multicenter trials to better refine the emerging genomic-based prognostic stratification in MB.