aglogo.gif (1177 bytes)The role of SDHD in sporadic paragangliomas of the head and neck region (glomus tumors)


Background of research project:

Non-chromaffin paragangliomas, or glomus tumors, are benign and slow growing tumors of the extra-adrenal paraganglion system, usually occurring at the carotid bifurcation in the head and neck region. Their incidence in the population is low, but a substantial proportion of them are due to a genetic defect that has been mapped to the long arm of chromosome 11. The inheritance pattern, however, is non-Mendelian and strongly suggests that the gene, PGL1, is subject to genomic imprinting. Recently, PGL1 was unmasked as being the SDHD gene, a subunit of the mitochondrial cytochrome B complex II. Germline mutations in SDHD have been found in nearly all paraganglioma families, and in about a third of all non-familial (sporadic) cases.

Research questions:

To investigate whether somatically acquired mutations in SDHD can be detected in sporadic glomus tumors.

Project description:

Germline mutations in tumor suppressor genes are typically inactivating mutations. The tumors arising in the carrier generally shows loss of the remaining wildtype allele. In non-inherited tumors of the same type, both mutations are acquired somatically during life. In familial glomus tumors, loss of the wildtype SDHD-allele is always seen, indicating that SDHD acts as a tumor suppressor gene in paraganglia. However, we have thus far been unable to demonstrate somatic SDHD-mutations in cases who are proven not to be carrier of a germline mutation. One reason for this is the cellular heterogeneity of paraganglioma: the tumor cells are embedded in stromal cells and other non-malignant cells. Isolation of genomic DNA from the whole tumor will therefore lead to a mixture of tumor-DNA and normal-DNA, in which the mutation may be difficult to detect.

Experimental design:

In this project we will perform microdissection technology to isolate tumor cells (and hence: tumor DNA) to near-purity. In some cases, we will be able to sort tumor cells on the basis of their deviant DNA-content in a flow cytometer. Purified tumor-DNA will be used for nested PCR-designs to detect mutations in the SDHD coding region by direct sequencing.

Techniques to be applied:

Microdissection; flow cytometry (in collaboration with the Department of Pathology); PCR; DNA sequencing.

Statistical methods:

None

Plan of work and time schedule:

We will first select eligible cases: those where microdissection can be succesful, and/or those with an aneuploid DNA-content. We currently have approximately 50 paragangliomas available for research purposes, either embedded as paraffin, or as fresh-frozen tissue. In a few cases, we will perform microdissection of 200-500 tumor cells. In aneuploid cases, flow sorting will be used to collect 10,000 tumor nuclei. DNA will be isolated from these samples, and be used for PCR and direct sequencing.

Equipment to be used:

Laser capture microdissection (at the Department of Pathology); PCR Themrocycler; automated DNA sequencer

Patients involved

Yes, about 10

Laboratory animals involved

No

Clinical/Non-clinical

Non-Clinical

Approval required from the Committee on medical ethics

No

Approval required from the committee on the use of laboratory animals

No

Updated:  19-02-2003
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