DETECTION OF CHROMOSOMAL CHANGES BY INTERPHASE CYTOGENETICS IN BIOPSIES OF RECURRENT ASTROCYTOMAS AND OLIGODENDROGLIOMAS

Recently, lineage-specific genetic pathways of tumor progression have been suggested in both oligodendrogliomas and astrocytomas. Aberration s consistently reported in gliomas include chromosomes 1, 7, IO, 17 an d 19. Identification of specific genetic damage may have important cli nical consequences, because oligodendrogliomas, unlike astrocytomas, a re responsive to chemotherapy. Genetic alterations specific for tumor type and tumor progression were investigated in 5 pairs of recurrent a strocytomas and s pairs of recurrent oligodendrogliomas by means of in terphase in situ hybridization (ISH) to paraffin-embedded, formalin-fi xed tissue sections. A set of DNA probes specific for the centromeric regions of chromosomes 1, 7, 10, 17, X and Y was applied. Since LOH st udies on oligodendrogliomas have revealed losses in the region of 1p32 -1p36, a DNA probe specific for the 1p36.3 locus was included. Hybridi zation with the 1p36.3 probe revealed loss of Ip in 5 of the 8 oligode ndroglioma recurrences, the aberration being present in the primary tu mors in 2 cases. In none of the astrocytomas was loss of Ip observed. Numerical aberrations were found in one astrocytoma pair (+7) and in t he second biopsy of an oligodendroglioma (+7, -10). Aneuploidy was fou nd by in situ hybridization in s of the 13 tumor pairs. Detection of a berrations in the 1p36.3 locus by interphase in situ hybridization to paraffin-embedded, formalin-fixed tumors may become a very useful tool in delineation of oligodendroglial from astrocytic genotypes, directi ng tumor specific therapy. The technique may be of crucial importance in tumor cases in which histologic criteria of lineage are not obvious .