Functional analysis of p53-target genes.

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We isolated p53-binding sites by genetic approach in yeast and then identified novel p53-target genes. One of these, called BAl1 , which was expressed in brain and repressed in 8/9 glioblastomas, was further characterized to inhibit neovascularization in the rat cornea by basic FGF.To investigate the in vivo anti-angiogenic effect of BAl1 gene on a human glioblastoma cell line, p53-defective human glioblastoma cells U373MG were transduced with the BAl1 gene using a recombinant adenoviral vector. In vivo neovascularization assay of the BAl1-infected glioblastoma cells was then performed using skinfold chamber system transplanted in SCID mice and revealed that BAl1 transduction resulted in reduced neovascurization in SCID mice.Expression of the glycosyl-phosphatidylinositol-anchored molecule-like protein (GML) gene, another p53 target, correlates with the sensitivity of some cancer cell lines to anticancer drugs and ionizing radiation. To investigate the function of GML further, we introduced the GML cDNA into various cancer cell lines under control of the tetracycline-regulated system. When we introduced GML into human glioblastoma cell line T98G, which lacks wild-type p53 and expresses no endogenous GML, we observed significant growth suppression accompanied by G2/M arrest in two independent, stable cell lines. We confirmed introduction of apoptosis by fluorescence-activated cell sorting (FACS) analysis and nuclear staining. Our results indicated that GML could induce apoptosis of T98G without functional p53, and implied that GML plays a crucial role in the apoptosis pathway in some cancer cells.