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Papillary Tumor of the Pineal Region: A Distinct Molecular Entity
Stephanie Heim1, Martin Sill2, David T W Jones3
1Institute of Neuropathology, University Hospital Münster, Münster, Germany.
Abstract:
Papillary tumor of the pineal region (PTPR) is a neuroepithelial brain tumor, which might pose diagnostic difficulties and recurs often. Little is known about underlying molecular alterations. We therefore investigated chromosomal copy number alterations, DNA methylation patterns and mRNA expression profiles in a series of 24 PTPRs. Losses of chromosome 10 were identified in all 13 PTPRs examined. Losses of chromosomes 3 and 22q (54%) as well as gains of chromosomes 8p (62%) and 12 (46%) were also common. DNA methylation profiling using Illumina 450k arrays reliably distinguished PTPR from ependymomas and pineal parenchymal tumors of intermediate differentiation. PTPR could be divided into two subgroups based on methylation pattern, PTPR group 2 showing higher global methylation and a tendency toward shorter progression-free survival (P = 0.06). Genes overexpressed in PTPR as compared with ependymal tumors included SPDEF, known to be expressed in the rodent subcommissural organ. Notable SPDEF protein expression was encountered in 15/19 PTPRs as compared with only 2/36 ependymal tumors, 2/19 choroid plexus tumors and 0/23 samples of other central nervous system (CNS) tumor entities. In conclusion, PTPRs show typical chromosomal alterations as well as distinct DNA methylation and expression profiles, which might serve as useful diagnostic tools.
Insights
Papillary tumors of the pineal region (PTPR) have distinct genetic changes, including chromosome 10 losses. Molecular profiling differentiates PTPR from other brain tumors and may predict outcomes.
Area of Science:
- Neuro-oncology
- Molecular Pathology
- Genomics
Background:
- Papillary tumor of the pineal region (PTPR) is a rare neuroepithelial brain tumor.
- PTPR often presents diagnostic challenges and has a tendency to recur.
- Limited information exists regarding the molecular basis of PTPR.
Purpose of the Study:
- To investigate chromosomal copy number alterations, DNA methylation patterns, and mRNA expression profiles in PTPR.
- To identify molecular markers for PTPR diagnosis and prognostication.
Main Methods:
- Analysis of chromosomal copy number alterations (CNAs) in 24 PTPR samples.
- DNA methylation profiling using Illumina 450k arrays.
- mRNA expression profiling and SPDEF protein expression analysis.
Main Results:
- Consistent losses of chromosome 10 were observed in PTPR.
- Common CNAs included losses of chromosomes 3 and 22q, and gains of chromosomes 8p and 12.
- DNA methylation profiling distinguished PTPR from ependymomas and other pineal tumors.
- PTPR could be classified into two methylation subgroups, with one group showing higher methylation and a trend towards shorter progression-free survival.
- SPDEF gene and protein overexpression was a notable finding in PTPR compared to other central nervous system tumors.
Conclusions:
- PTPR exhibits characteristic chromosomal alterations and distinct DNA methylation and gene expression profiles.
- These molecular features can serve as valuable diagnostic tools for PTPR.
- Further research into SPDEF's role in PTPR is warranted.
