The long term goal is to elucidate the roles of receptor protein-tyrosine kinases (PTKs) of the EPH family during development of the nervous system and their potential involvement in human diseases, including hereditary/congenital neurological disorders and cancer of the nervous system origin. Receptor protein-tyrosine kinases (PTK) of the EPH family and their transmembrane-bound ligands (LERKs) have been shown to be involved in axonogenesis, axon guidance, acquisition of brain subregional identities, and neuronal cell survival. In addition, some members of the EPH-related PTKs have been implicated in oncogenesis. They previously isolated and characterized a human EPH-related PTK gene, DRT. This proposal is designed to study the role of DRT in the pathogenesis of neuroblastoma (NB), a common pediatric tumor of embryonic neural crest origin. DRT maps to chromosome 1p36.1, a site of frequent deletion and rearrangement in neuroblastoma. DRT transcripts are highly expressed in NB cell lines, compared to those of two other EPH-related genes, ECK and NET. Several NB cell lines express aberrant size DRT transcripts, suggesting that the DRT locus has undergone certain structural alterations that lead to generation of the abnormal DRT transcripts. Moreover, DRT is often co-expressed with its ligand genes, LERK-5 and LERK-8, in NB cell lines. Based on these observations, we hypothesize that DRT contributes to the pathogenesis of NB by (1) auto-activation by the co-expression of its ligand(s), and/or (2) by genetic mutations that result in the constitutive activation of the DRT kinase, providing NB cells with increased survivability and/or growth advantage. In this proposal, specifically (1) they will examine whether DRT and LERK genes are expressed in primary neuroblastoma tumors, and whether the expression of DRT and/or LERK genes is associated with certain biological and clinical features of NB tumors. (2) they will investigate if the over-expression of DRT, LERKs and their combinations transform an indicator cell line, NIH3T3, and convert the cells to form tumors in athymic nude mice. (3) they will also examine whether or not the DRT kinase modulates survival and differentiation of NB cells. (4) they will examine if DRT is mutated in NB cell lines and tumors. Results of this study should provide important insights into the biology and genetics of neuroblastoma and ultimately may lead to a therapeutic approach.
