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Genetic and epigenetic alterations in tumor progression in a dedifferentiated chondrosarcoma
M Röpke1, C Boltze, H W Neumann
1Department of Orthopedics, Otto-von-Guericke University, Magdeburg, Germany. martin.roepke@medizin.uni-magdeburg.de
Abstract:
In this case of a dedifferentiated chondrosarcoma, we searched for genetic or epigenetic alterations in both components of the tumor, the low grade chondroblastic component, and the high grade osteosacomatouscomponent. To date, only little is known about aberrant patterns of DNA methylation in chondrosarcomas. Microdissection was used as a valuable method for clearly separating the tissues. We examined CpG island methylation of 8 tumor suppressor genes and candidate tumor suppressor genes, which are involved in different pathways: cell cycle (p21WAF1, p16INK4, p14ARF), apoptosis (DAPK, FHIT), DNA repair (hMLH1), and cell adherence (E-Cadherin). We found p16INK4 and E-cadherin promotor methylation in the low grade chondroid compartment of the dedifferentiated chondrosarcoma. P16INK4, FHIT, and E-cadherin were methylated in the highly malignant osteosarcomatous compartment of the tumor. Earlier investigations of this chondrosarcoma showed p53 mutation and p53-LOH in the anaplastic component. As shown in this case, it was accompanied by Rb-LOH. Early methylation of p16IK4 and E-cadherin in the chondroid compartment could point to the monoclonal origin of demonstrated dedifferentiated chondrosarcoma. Further alterations, as shown in p53, Rb and FHIT, are responsible for the "switch" to a high grade anaplastic sarcoma.
Insights
This study investigated DNA methylation in dedifferentiated chondrosarcoma, finding p16INK4 and E-cadherin promoter methylation in early tumor stages. These epigenetic changes may indicate a monoclonal origin for chondrosarcoma progression.
Area of Science:
- Oncology
- Epigenetics
- Cancer Genomics
Background:
- Chondrosarcomas are malignant tumors of cartilage.
- Dedifferentiated chondrosarcoma presents with both low-grade chondroid and high-grade osteosarcomatous components.
- Aberrant DNA methylation patterns in chondrosarcomas are not well understood.
Observation:
- Microdissection was employed to isolate distinct tumor components.
- CpG island methylation was analyzed in 8 tumor suppressor genes across different cellular pathways.
- Specific genes examined included those involved in cell cycle regulation, apoptosis, DNA repair, and cell adherence.
Findings:
- Promoter methylation of p16INK4 and E-cadherin was identified in the low-grade chondroid component.
- In the high-grade osteosarcomatous component, p16INK4, FHIT, and E-cadherin showed methylation.
- Previous findings indicated p53 mutation and loss of heterozygosity (LOH) in the anaplastic component, alongside Rb-LOH in this case.
Implications:
- Early methylation of p16INK4 and E-cadherin suggests a potential monoclonal origin for dedifferentiated chondrosarcoma.
- Subsequent genetic alterations in p53, Rb, and FHIT likely drive the transition to a high-grade anaplastic sarcoma.
- Understanding these epigenetic and genetic events is crucial for elucidating chondrosarcoma pathogenesis.