GENETIC ANALYSIS OF NEUROBLASTOMA

DESCRIPTION (Applicant's abstract reproduced verbatim): Neuroblastoma (Nb) is the most common solid tumor in children. Despite intensive treatment regimens, however, Nb has a relatively poor prognosis in advanced stages and accounts for 15 percent of all childhood deaths due to cancer. Stage 4S disease is a special variant form of Nb which occurs in infants under the age of 12 months and, even despite a large tumor load and distant metastases, these tumors will often regress spontaneously. Identifying the genes which allow this rapid expansion and metastasis of neuroblasts will be invaluable in understanding the early stage of Nb tumorigenesis. Constitutional chromosome translocations have been instrumental in the identification of genes responsible for a wide variety of human genetic diseases, where it has been shown that the function of critical genes is affected in some way by the breakpoints. We have recently cloned the genes interrupted by a constitutional 1;10 chromosome translocation from a patient who developed stage 4S neuroblastoma. The 1p22 chromosome breakpoint occurs within the NB4S gene. This gene has two identifiable motifs: a TBC1 domain and a coiled-coil domain. Both of these motifs are indicative of protein-protein interactions. The gene on chromosome 10, TRNG10, is a member of an emerging class of genes which are transcribed but not translated. This gene is overexpressed in cancer cells compared with normal cells. As a result of the translocation the TBC1 domain of NB4S is truncated by in-frame fusion to TRNG10. Mutation analysis of NB4S does not indicate that it functions as a tumor suppressor gene. Transfection studies, on the other hand, indicate that a truncated form of NB4S is a dominantly transforming oncogene. To establish the function of the novel chimeric gene we will undertake a series of in vitro studies to characterize the dominant transforming activity, as well as the spatial and temporal expression pattern. We will also use immunoprecipitation and yeast-two hybrid analysis to define interacting genes that may be important for function. In an attempt to establish a mouse model for 4S neuroblastoma, we will express the chimeric gene in transgenic mice. As a result of an improved understanding of the genetic events that give rise to Nb, it may eventually be possible to design novel therapeutic approaches directed against the gene and its product, as well as to assess their value in the pre-symptomatic identification of at-risk individuals.