Dirk Heckel

MGEA6 is tumor-specific overexpressed and frequently recognized by patient-serum antibodies.

Tumorigenesis of meningioma has been associated with chromosome 22, most notably the NF2 gene, but additional genes have also been implicated in meningioma development. Previously, we have cloned the cDNAs for the meningioma expressed antigen 6 (MGEA6) and its splice variant MGEA11. Here, we show that antibodies against recombinantly expressed MGEA6/11 are found in 41.7% (10/24) of the sera from meningioma patients and in 2/8 sera of glioblastoma patients, whereas no response was seen in 12 sera from healthy persons. Western-blot analyses using generated polyclonal antibodies, revealed overexpression in meningioma and glioma tumor samples compared to normal brain. Immunohistochemical staining of tissue sections confirms reactivity in meningioma tumor cells and tumor cells of glial origin. We found no reactivity to normal astrocytes and only faint reactivity to normal leptomeninges. Sequence analysis predicted membranic localization of MGEA6/11, that was confirmed by cell fractionation. The immune response to MGEA6/11 is frequent in both meningioma and glioma patients and may likely be attributed to overexpression of the MGEA6/11 protein in the tumor cells.

Identification of an amplified gene cluster in glioma including two novel amplified genes isolated by exon trapping

Abstract Gene amplification, which occurs in more than 50% of malignant gliomas, is considered to play a pivotal role in tumorigenesis. There are, however, few studies aimed toward the isolation of novel genes from amplified sequences. Previously, we reported amplification of the protooncogene MET (hepatocyte growth factor receptor; 7q31) in more than 20% of glioblastomas. For an approximate size estimation of the amplification unit we analyzed three glioblastomas all of which carried an amplified MET gene, by Southern blot analysis and/or competitive polymerase chain reaction using eight DNA markers. Although the extent of the amplified domain varied, the close vicinity of the MET gene was the only region consistently amplified in these glioblastomas. A yeast artificial chromosome (YAC) contig of 900 kb was refined spanning the amplified region flanking the MET gene. The YAC inserts were subcloned into 59 cosmids, which were used for exon trapping. Eight sequences were identical to parts of the genes MET and CAPZA2 (human actin capping protein α-subunit). Two newly identified exons and the CAPZA2 exons were amplified in tumor TX3095, which retains an amplified MET gene. The new exons were localized close to MET and CAPZA2. Characterization of the clones, which were termed glioma-amplified sequence (GAS)7-1 and GAS7-2, showed an open reading frame and a different expression pattern in multiple human tissues. This study reports the identification of a cluster of amplified genes including two novel genes in a region amplified in more than 20% of glioblastomas.

KUB3 amplification and overexpression in human gliomas

Gene amplification is known to occur frequently in human glioma. Recently we reported cloning of a novel gene termed glioma‐amplified sequence 16 (GAS16) by microdissection‐mediated cDNA capture. In this article, we demonstrate that GAS16 results from an alternative splicing process of the Ku70 binding protein 3 (KUB3) that is essential for DNA double‐strand break repair. The alternative splice product was found in glioblastoma and in normal fetal brain. We determined the amplification frequency of KUB3 in glioma with different grading. We analyzed a total of 102 glioma primary tumors and found KUB3 to be amplified in 12/82 (14%) glioblastomas, 4/13 anaplastic astrocytomas (30%), and 2/4 astrocytomas, but in none of three pilocytic astrocytomas. Northern blot analysis of glioblastoma shows a strong correlation between KUB3 amplification and overexpression. Amplification of KUB3 appears to be independent of other genetic changes frequently associated with the development of gliomas, including EGFR amplification, LOH of TP53, and LOH of chromosome 10. The KUB3 amplification and overexpression may interfere with the function of KUB3 in the DNA–PK complex involved in the maintenance of genome stability and reduction of mutation frequency. GLIA 36:1–10, 2001.