12p-Amplicon structure analysis in testicular germ cell tumors of adolescents and adults by array CGH

Abstract

All invasive testicular germ cell tumors of adolescents and adults (TGCTs), that is, seminomas and nonseminomas, show gain of 12p sequences, mostly as isochromosomes. Although several candidate genes have been suggested, the relevant gene(s) have not been identified yet. About 10% of testicular seminomas, however, show a more restricted amplification of the 12p11.2-p12.1 region, in which the various amplicons show an apparent overlap, allowing for the shortest region of amplification overlap approach, aiming at the identification of pathogenetically relevant sequences residing in this region. Here we report on a high-resolution 12p-amplicon architecture analysis using microarray-based comparative genomic hybridization, the results of which were subsequently confirmed by fluorescent in situ hybridization studies. The 12p-specific microarray contained 63 positionally selected BAC clones, which are more or less evenly distributed over the short arm of chromosome 12 (average spacing: less than 500 Kb), including 20 clones within the region of amplification. Out of a series of 17 seminomas, seven seminomas showed amplification of the whole amplicon region, of which three showed a dip in T/R value in the center of the amplified area. A more complex amplification pattern was found in the other 10 seminomas: three showed predominant amplification at the centromeric border; one mainly at the telomeric border; six showed a balanced amplification of both the centromeric and telomeric regions. The only nonseminoma investigated showed a structure in which the centromeric border was only amplified. These data support a mechanistic model in which at least two 12p genes, situated at the border regions of the amplicon, are positional candidates capable of actively supporting tumor progression in TGCTs.

Molecular genetic analysis of central nervous system germ cell tumors with comparative genomic hybridization

“…It is generally assumed that the amplification of tumor genes at this region triggers malignant transformation at the transition from TIN to invasive malignant germ cell tumors. 8,9,31 Since in our patient the amplicon is located at the identical chromosomal region as in testicular germ cell tumors, this observation provides additional evidence in favor of a common pathogenesis of testicular and CNS-GCTs.…”

“…7 In the remaining tumors, gain of chromosomal material of 12p is related to either marker chromosomes or homogeneously staining regions that contain chromosomal material derived from chromosomal band 12p11.2-12.1. 8,9 Additional chromosomal imbalances have also been reported in testicular germ cell tumors. However, these are less frequent and less consistent as compared to gain of 12p.…”

Genomic copy number and expression patterns in testicular germ cell tumours

“…NS, which have a median age at diagnosis of 25, exhibit various stages of differentiation with cells from embryonic, extra-embryonic and somatic tissue types (Mostofi, 1973). Material from the short arm of chromosome 12 is invariably gained in these tumours and in roughly 10% of cases a smaller region of gain at 12p11.2 -p12.1 has been defined (Rodriguez et al, 2003;Zafarana et al, 2003).…”

In vivo differentiation and genomic evolution in adult male germ cell tumors

“…In addition to 12p, other chromosomal regions have also been identified that are frequently altered in GCTs (von Eyben, 2004), including gains on regions of 2p, 4q, 6p, 7, 8, 17q, 19p, and 21, and losses on chromosomes 4, 10q, 12q, 11, 13, and 18, (Korn et al, 1996;Murty et al, 1999;Kraggerud et al, 2002;Draper et al, 2004;von Eyben, 2004). Sem and NSGCTs have also demonstrated differential copy number gain/loss patterns, with gains of 15q and 22q and high-level amplifications of 12p associated with Sem (Kraggerud et al, 2002;Zafarana et al, 2003) and gains of proximal 17q and losses of 10q associated with NSGCTs .…”

“…The vast majority of GCTs manifest this gain as an isochromosome of 12p, while a small proportion show tandem duplication of material from 12p (Atkin and Baker, 1982;Bosl et al, 1989;Murty and Chaganti, 1998). Additionally, a number of tumors show subregional, high-level amplification of 12p (Bourdon et al, 2002;Looijenga and Oosterhuis, 2002;Zafarana et al, 2003). Extensive studies of 12p have identified a number of candidate target genes, including CCND2 and a cluster of stem cell genes at 12p13.31 (Houldsworth et al, 1997;Clark et al, 2004;Korkola et al, 2006).…”