Death-associated protein 3 (Dap-3) is overexpressed in invasive glioblastoma cells in vivo and in glioma cell lines with induced motility phenotype in vitro

Purpose: To discover the genetic determinants of glioma invasion in vivo, w e compared the mRNA expression profiles of glioblastoma cells residing at t he tumor core versus those at the invasive rim of a human tumor resection. Experimental Design: From a single glioblastoma specimen, 20,000 individual cells from each region (core and invasive rim) were collected by laser cap ture microdissection and analyzed by mRNA differential display. Differentia l expression of gene candidates was confirmed by laser capture microdissect ion and quantitative reverse transcription-PCR in additional glioblastoma m ultiforme specimens, and the role in migration was further evaluated in gli oma cell lines in vitro. Results: Reproducible overexpression the death-associated Protein 3 (Dap-3) mRNA (NM 004632, GenBank; also reported as human ionizing resistance confe rring protein mRNA, HSU18321, GenBank) by invasive cells was identified. Al though the full-length Dap-3 protein has been described as proapoptotic, th e NH2-terminal fragment can act in a dominant negative way resulting in pro tection from programmed cell death. In glioma cell lines T98G and G112 with an induced motility phenotype, Dap-3 was up-regulated at the mRNA and prot ein level as assessed by quantitative reverse transcription-PCR, cDNA micro array, and Western blot analysis. These cells showed an increased resistanc e to undergo camptothecin-induced apoptosis, which was overcome by effectiv e Dap-3-antisense treatment. Antisense treatment also decreased the migrati on ability of T98G cells. Conclusions: Dap-3 is up-regulated in invasive glioblastoma multiforme cell s in vivo and in glioma cells with an induced motility phenotype in vitro. When migration is activated, Dap-3 is up-regulated and cells become resista nt to apoptosis. These findings suggest that Dap-3 confers apoptosis-resist ance when migration behavior is engaged.