Gliomas are the most common primary human brain tumors. Even despite aggressive therapeutic treatments the most malignant of these, glioblastoma, is still a lethal disease. If new and efficient therapeutic approaches are to be developed then a more comprehensive understanding of the genetics and biology of the brain tumors will be required. Despite considerable analysis of genetic changes associated with the development of gliomas, no glioma-specific tumor suppressor gene has been identified to date. However, as a result of extensive cytogenetic and loss of heterozygosity (LOH) analysis it is now clear that partial or complete loss of chromosomes 10q and 19q occurs in the vast majority of malignant gliomas. These observations indicate that these regions contain genes, which, as a result of inactivation play an important role in tumorigenesis. An important mechanism resulting in gene inactivation is through chromosome translocations, which disrupt the genes at the breakpoints. Thus, these translocation breakpoints pinpoint the position of the critical tumor suppressor gene within the region of LOH. Recently, the principal investigator has identified three glioblastoma cells, which carry translocations involving chromosome regions 10q24 and 19q13. One of these cell lines carries a reciprocal 1(10;19)(q24;q13) translocation and all of these breakpoints lie exactly in the critical regions on chromosomes 10 and 19 indicated by LOH to be important. Using FISH analysis this lab has positioned YAC clones across the breakpoints on both chromosomes of the 10;19 reciprocal translocation. The exact molecular position of the translocation breakpoints were then identified using somatic cell hybrids created from these cells which contain the rearranged chromosomes. They have now isolated a smaller BAC clone from chromosome 10, which crosses the breakpoint. The principal investigator will now use the same strategy to isolate a BAC clone, which crosses the chromosome 19 breakpoint. Since these BAC clones are relatively small (170Kb on average) the applicant will use them to isolate the genes interrupted by the translocation using several different but complementary approaches including cDNA library screening, cDNA capture and exon trapping. The applicant will then use these genes to analyze the large number of brain tumor samples available to determine their wider involvement in brain tumorigenesis. The identification of the genes which are involved in the development of malignant gliomas will not only improve our understanding of the basic underlying mechanisms of the disease process but also may lead to the development of a targeted therapy against the genes and their products and also improve diagnosis and prognosis for this highly heterogeneous group of tumors.
