Trial Information

Comparative 2-D Tumor Analysis in Familial Gliomas

The investigators propose to study the genetic changes in patients with familial glioma as
the first step in identifying the gene(s) that cause these tumors. With informed consent,
DNAs from tumor and non-tumor tissue, histologic sections, pedigrees and detailed clinical
information will be acquired for patients with familial gliomas. A genomic screening
methodology named 2D genomic scanning will be used. Differences detected between the tumor
and normal tissues (blood, fibroblasts) will identify events occurring in the tumoral
process. A comparison of the events in familial and sporadic gliomas will outline some of
the pathways suspected to be involved both in tumor initiation and progression. Briefly, DNA
fragments are amplified with the polymerase-chain-reaction (PCR) from tumor and normal
tissue using primers designed to identify 100 to 1000 random sites within the genome. The
PCR primers will hybridize throughout the genome and generate a manageable number of short
PCR products that are detected by gel electrophoresis and autoradiography. The PCR for both
tumor and constitutional tissues are amplified through 20 to 25 cycles to ensure adequate
signal but to avoid entering a non-exponential phase of the PCR amplification. The products
are radiolabelled and then run on a standard sequencing gel. The single lane containing
labelled PCR products is cut out and then overlaid onto a denaturing grading gel with a 10
to 75% grading of denaturant. The labelled DNA is then separated in the second dimension and
the DNA is detected by Southern Transfer to nylon membrane or by gel-drying and direct
exposure film. A direct comparison of PCR signals from the tumor and constitutional tissue
identifies the loss or gain of signal which reflects the same phenomena within the genome.
The isolation and characterization of fragment consistently altered in gliomas will provide
the first step in the search for genes responsible in the initiation and progression of
gliomas. Because of the collaboration among investigators of different centres in Canada,
the current investigators have a unique opportunity to perform the study on the largest
collection of familial gliomas in the world. They expect several genomic abnormalities in
each tumor. Some of these may be seen in several patients. Data will be analyzed primarily
using descriptive statistics, with frequency of genetic abnormalities at different
chromosomal locations described.