Expression of the src homology 3 (SH3) domain-containing expressed in tumorigenic astrocytes (SETA) gene is associated with the tumorigenic state in astrocytes. SETA encodes a variety of adapter proteins containing either one or two SH3 domains, as suggested by the sequence heterogeneity of isolated cDNAs. Using both SH3 domains in a yeast two-hybrid screen of a glial progenitor cell cDNA library, we isolated the rat homolog of the ALG-2-interacting protein 1 or ALG-2-interacting protein X (AIP1/Alix). In vitro confrontation experiments showed that the SH3-N domain of SETA interacted with the proline-rich C terminus of AIP1. In co-immunoprecipitation experiments, SETA and AIP1 interacted and could form a complex with apoptosis-linked gene 2 protein. Endogenous SETA and AIP1 proteins showed similar patterns of staining in primary rat astrocytes. Misexpression of a variety of SETA protein isoforms in these astrocytes revealed that they localized to the actin cytoskeleton. Furthermore, SETA proteins containing the SH3-N domain were able to sensitize astrocytes to apoptosis induced by UV irradiation. Expression of the isolated SH3-N domain had the greatest effect in these experiments, indicating that interference in the interaction between endogenous SETA and AIP1 sensitizes astrocytes to apoptosis in response to DNA damage.

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A key feature in the malignant behavior of glioblastoma is the tendency to invade host brain tissue surrounding the primary tumor site. Several members of the matrix metalloproteinase family are thought to contribute to this invasive capacity. A single nucleotide polymorphism has been described in the matrix metalloproteinase-1 (MMP-1) promoter that consists of either the presence or absence of a guanine nucleotide at position 21607. The presence of the guanine base creates a functional binding site for members of the ETS family of transcription factors and has been shown to increase MMP-1 transcription. The purpose of our study was to characterize this polymorphism in human glioblastoma. Promoter genotyping was performed on brain tumor tissue obtained from 81 patients and compared to 57 healthy individuals. The 2G/2G genotype is more prevalent in glioblastoma tissue compared to healthy individuals (p 5 0.01). mRNA and protein expression were measured in a subset of brain tumor and normal brain tissue samples. MMP-1 protein levels are significantly higher in glioblastoma tissue compared to normal brain (p 5 0.001). Electromobility shift assays and promoter assays were performed to assess binding capability and transcriptional activity, respectively. Proteins present in glioma cell lines can specifically bind the 2G promoter probe. MMP-1 transcription is significantly higher in cells transfected with the 2G promoter when compared to cells transfected with the 1G promoter (p<0.02). This polymorphism may provide a mechanism for increased expression of MMP-1 in malignant gliomas via elevation of MMP-1 mRNA transcription and may underlie the invasive phenotype. ' 2005 Wiley-Liss, Inc.Key words: brain tumors; matrix metalloproteinases; transcriptional regulation; SNP Gliomas account for 44% of all primary central nervous system tumors and of these the most common is the highly malignant glioblastoma multiforme (GBM). 1 Despite significant improvements in the diagnosis and treatment for patients with a GBM, this primary brain tumor remains essentially incurable. Although surgery and radiotherapy substantially improve patient survival, 2 95% of patients have a mean survival of 2 years following diagnosis. Patients foregoing treatment have a mean survival time of 4 months. The characteristic ability of GBMs to invade surrounding normal tissue makes total surgical resection virtually impossible.Matrix metalloproteinase-1 (MMP-1), also known as collagenase-1, is a member of the MMP family of zinc-dependent endopeptidases, which have the ability to cleave substrates in the extracellular matrix. Substrates for MMP-1 include collagen types I, II, III, VII and X, gelatin, entactin, aggrecan and tenascin. Until recently it was thought that MMPs were responsible mainly for the degradation of extracellular matrix components. However it has become clear that the MMP family has a wide range of other influences on biologic processes including the generation of bioactive proteins. [3][4][5] Examples include the cleavage of the proteo...