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Scattered genomic amplification in dedifferentiated liposarcoma
Nils Mandahl1, Linda Magnusson1, Jenny Nilsson1
1Division of Clinical Genetics, Department of Laboratory Medicine, Lund University, SE-221 84 Lund, Sweden.
Molecular Cytogenetics
|June 28, 2017
Summary
This study describes a novel dedifferentiated liposarcoma (DDLS) with a unique scattered amplification pattern, differing from typical ring or giant marker chromosomes. This finding offers new insights into liposarcoma cytogenetics and potential therapeutic targets.
Area of Science:
- Oncology
- Genetics
- Molecular Biology
Background:
- Atypical lipomatous tumor (ALT), well-differentiated liposarcoma (WDLS), and dedifferentiated liposarcoma (DDLS) typically exhibit near-diploid karyotypes with ring or giant marker chromosomes.
- These marker chromosomes often contain amplified genes like CDK4, HMGA2, and MDM2 from chromosome 12q.
- Pleomorphic liposarcomas (PLS) are characterized by highly aberrant and heterogeneous karyotypes.
Purpose of the Study:
- To present a case of DDLS with an atypical hypertriploid karyotype.
- To investigate the cytogenetic and molecular characteristics of this unique DDLS.
- To explore potential mechanisms underlying the observed genetic alterations.
Main Methods:
- Karyotyping to determine the overall chromosomal structure.
- SNP array analysis to identify copy number variations and amplifications.
- Fluorescence in situ hybridization (FISH) to visualize specific amplified sequences.
- RNA sequencing to assess gene expression levels.
Main Results:
- The DDLS case presented an atypical hypertriploid karyotype without ring or giant marker chromosomes.
- SNP array revealed amplification of 5p and discontinuous amplicons of 12q (including CDK4), along with other chromosomal regions (1q, 3q, 7p, 9p, 11q, 20q).
- FISH showed scattered distribution of 5p and 12q sequences across multiple chromosomes. RNA sequencing indicated elevated expression of TRIO, AMACR, CDK4, HMGA2, and MDM2.
Conclusions:
- The observed scattered amplification pattern is novel and distinct from typical cytogenetic findings like double minutes or homogeneously staining regions.
- This pattern does not align with chromothripsis.
- Possible mechanisms include alternative lengthening of telomeres (ALT) and telomere crisis events, frequently observed in DDLS.
