ONCOGENE AMPLIFICATION AND EXPRESSION IN NEURAL TUMORS

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The goal of this research is to assess the roles of oncogenes in neural tumors and in normal neural cells. Amplification of the oncogene N-myc occurs in approximately 50% of neuroblastomas and is associated with poor clinical outcome, yet not all neuroblastomas with an unfavorable prognosis have N-myc amplification. Cytogenetic evidence of gene amplification has also been found in neural tumors affecting the brain, such as medulloblastomas and cerebral primitive neuroectodermal tumors (PNET's), but the identities of the amplified genes have not been determined. This research will begin by examining neuroblastomas, medulloblastomas, and cerebral PNET's for amplification of N-myc and other oncogenes, by quantitative hybridization of Southern blots of tumor DNA samples with oncogene DNA sequences. The tumors will also be examined by "Northern" blotting to determine levels of oncogenes expression. This will confirm that oncogenes which are amplified are also expressed and will determine whether some tumors have enhanced expression of specific oncogenes without amplification. Tumors will also be studied at the single cell level using in situ hybridization. This will detect tissue heterogeneity and will reveal the histological staining properties of cells with oncogene amplification or expression. The data on oncogene amplification and expression will also be related to the clinical behavior of the tumors. Tumors with amplification will then be studied at the molecular level to elucidate the structure of the units of amplification. Genetic rearrangements within amplified DNA sequences which flank oncogenes will be examined for evidence of specific sequences at splice sites, which may be related to the process of amplification. Finally, the roles of oncogenes in neural tumors and in normal neural cells will be investigated. Normal fetal and adult tissues will be examined for oncogene expression and experiments will be initiated to study the physiological roles of oncogenes in neural tumor cell lines and primary cultures of neural cells. This research is intended to provide additional genetic markers for the clinical assessment of children with neural tumors. It will also help to elucidate the mechanisms of transformation and progression of these tumors and will contribute to our understanding of genes which control the proliferation and differentiation of normal neural cells.