Identification of the critical region of 12p over-representation in testicular germ cell tumors of adolescents and adults

Abstract

Cytogenetically, testicular germ cell tumors of adolescents and adults (TGCTs) are characterized by gain of 12p-sequences, most often through isochromosome formation (i(12p)). Fluorescence in situ hybridization (FISH) has shown that i(12p))-negative TGCTs also cryptically contain extra 12p-sequences. The consistency of 12p-over-representation in all histological subtypes of TGCTs, including their preinvasive stage, suggests that gain of one or more genes on 12p is crucial in the development of this cancer. So far, studies aimed at the identi®cation of the relevant gene(s) were based on thè candidate-gene approach'. No convincing evidence in favor of or against a particular gene has been reported. We combined conventional karyotyping, comparative genomic hybridization, and FISH to identify TGCTs with ampli®cations of restricted regions of 12p. Out of 49 primary TGCTs (23 without i(12p), 13 with and 13 unknown), eight tumors (six without i(12p) and two unknown) showed ampli®cations corresponding to 12p11.1-p12.1. Using bicolour-FISH, physical mapping, and semi-quantitative polymerase chain reactions, the size of the shortest region of overlap of ampli®cation (SROA) was estimated to be between 1750 ± 3000 kb. In addition, we mapped a number of genes in and around this region. While fourteen known genes could be excluded as candidates based on their location outside this region, we demonstrate that KRAS2, JAW1 and SOX5 genes are localized within the SROA. While KRAS2 and JAW1 map to the proximal border of the SROA, SOX5 maps centrally in the SROA. KRAS2 and JAW1 are expressed in all TGCTs, whereas one 12p amplicon-positive TGCT lacks expression of SOX5. The critical region of 12p over-represented in TGCTs is less than 8% of the total length of the short arm of chromosome 12. It will be helpful in the identi®cation of the gene(s) involved in TGCT-development.

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

“…Data regarding the physical description of these amplicons as well as the SRO are summarized in Table 2. The borders of the amplicon, as previously determined by FISH on tissue sections (Mostert et al, 1998;Roelofs et al, 2000;Zafarana et al, 2002), were found to be fully in line with the data obtained by array CGH. Since 20 out of the 68 BACs map within the SRO, the array data also allowed a detailed analysis of the amplicon structure for each individual tumor.…”

“…Several years ago, we initiated a study on TGCTs, in particular seminomas, with a restricted 12p amplification (Suijkerbuijk et al, 1994;Mostert et al, 1996Mostert et al, , 1998. We subsequently showed that the breakpoints of the amplicon cluster significantly (Roelofs et al, 2000;Zafarana et al, 2002), which could indicate that two relevant genes are present within the SRO, one at the centromeric and the other at the telomeric side.…”

Sacrococcygeal teratomas: clinico-pathological characteristics and isochromosome 12p status

“…The best studied among them is i12p. 4 This cytogenetic abnormality is present in the majority of testicular teratomas, regardless of age and presence of immature elements. In contrast, i12p is largely absent in immature ovarian teratomas and uniformly absent in mature ones.…”

“…Whereas ovarian teratomas are typically cystic, composed of mature elements and almost uniformly benign, postpubertal testicular tumors are considered to nearly always 2 carry a potential for malignant behavior, even when composed entirely of mature elements. 3 The cytogenetic and molecular characteristics that underpin the differences among gonadal germ cell tumors are now better understood, with the landmark finding of isochromosome 12p or 12p amplification in the majority of testicular germ cell tumors, 4 but a complete absence thereof in benign, mature ovarian teratomas. 5 A recent study of anterior mediastinal extragonadal germ cell tumors has shown that the biological behavior and prognosis of teratomas at this site is intermediate between those of the testis and the ovary.…”

Self-renewal of teratocarcinoma and embryonic stem cells

“…In contrast, the case for an involvement of Stella is less clear (Payer et al, 2003). However, the genetics of testicular germ cell tumour susceptibility are controversial, with some studies mapping the region encompassing Nanog, Stella and GDF3 outwith the region of minimal duplication in isochromosome 12 (Mostert et al, 1998;Rodriguez et al, 2003;Skotheim and Lothe, 2003).…”