Epithelial-mesenchymal transition markers in malignant ovarian germ cell tumors.

The purpose of this study was to determine the expression and potential clinical role of epithelial-to-mesenchymal transition (EMT)-related factors in malignant ovarian germ cell tumors (MOGCT). Protein expression of E-cadherin, N-cadherin, P-cadherin, Zeb1, HMGA2, and vimentin by immunohistochemistry was analyzed in 42 MOGCT from patients treated in Norway during the period 1981-2001. Expression was analyzed for association with clinicopathologic parameters. E-cadherin (p = 0.016) and HMGA2 (p = 0.002) expression was significantly higher in immature teratomas and yolk sac tumors compared with dysgerminomas. Vimentin (p < 0.001) and Zeb1 (p = 0.029) staining was significantly higher in immature teratomas compared with yolk sac tumors and dysgerminomas, whereas no significant differences were observed for N-cadherin and P-cadherin. EMT-associated markers were not significantly related to clinicopathologic parameters including age, tumor diameter, and FIGO stage. In conclusion, based on this limited series, EMT-associated markers are not associated with clinical parameters in MOGCT, in contrast to ovarian carcinoma. EMT-related proteins are differentially expressed among various MOGCT subtypes, suggesting differences in biological characteristics associated with invasion and metastasis.

Molecular characteristics of malignant ovarian germ cell tumors and comparison with testicular counterparts: implications for pathogenesis.

This review focuses on the molecular characteristics and development of rare malignant ovarian germ cell tumors (mOGCTs). We provide an overview of the genomic aberrations assessed by ploidy, cytogenetic banding, and comparative genomic hybridization. We summarize and discuss the transcriptome profiles of mRNA and microRNA (miRNA), and biomarkers (DNA methylation, gene mutation, individual protein expression) for each mOGCT histological subtype. Parallels between the origin of mOGCT and their male counterpart testicular GCT (TGCT) are discussed from the perspective of germ cell development, endocrinological influences, and pathogenesis, as is the GCT origin in patients with disorders of sex development. Integrated molecular profiles of the 3 main histological subtypes, dysgerminoma (DG), yolk sac tumor (YST), and immature teratoma (IT), are presented. DGs show genomic aberrations comparable to TGCT. In contrast, the genome profiles of YST and IT are different both from each other and from DG/TGCT. Differences between DG and YST are underlined by their miRNA/mRNA expression patterns, suggesting preferential involvement of the WNT/ß-catenin and TGF-ß/bone morphogenetic protein signaling pathways among YSTs. Characteristic protein expression patterns are observed in DG, YST and IT. We propose that mOGCT develop through different developmental pathways, including one that is likely shared with TGCT and involves insufficient sexual differentiation of the germ cell niche. The molecular features of the mOGCTs underline their similarity to pluripotent precursor cells (primordial germ cells, PGCs) and other stem cells. This similarity combined with the process of ovary development, explain why mOGCTs present so early in life, and with greater histological complexity, than most somatic solid tumors.

Evaluation of genomic changes in a large series of malignant ovarian germ cell tumors--relation to clinicopathologic variables.

Malignant ovarian germ cell tumors (mOGCT) affect women in their reproductive years, making fertility-saving treatment important. A reliable prediction of the clinical behavior is essential for an optimal therapeutic approach. The genetic changes and molecular mechanisms underlying these rare tumors remain poorly understood. To address these issues, we performed DNA ploidy analysis by high-resolution image cytometry in a series of 47 mOGCT and correlated the findings with the DNA copy number changes detected by comparative genomic hybridization (CGH) and clinical outcome. Of 47 tumors, 15 were diploid, 14 were tetraploid, 2 were polyploid, and 13 were aneuploid. All the immature teratomas were diploid, in contrast to the dysgerminomas and endodermal sinus tumors. The International Federation of Gynecology and Obstetrics (FIGO) staging, residual tumors after surgery, and DNA ploidy distribution were significant, independent prognostic factors in survival analysis. The study revealed that the number of DNA copy number aberrations was increased in tetraploid and aneuploid tumors as compared to diploid tumors. Furthermore, a high percentage of aneuploid nuclei in a sample were associated with a complex CGH profile of the tumor in question. The present study confirms that DNA aneuploidy assessment by image analysis may be linked to genetic instability, which is detected as genetic aberrations by CGH. DNA ploidy gives significant prognostic information in addition to the clinical stage in mOGCT with FIGO stage II-IV.

Genome profiles of bilateral dysgerminomas, a unilateral gonadoblastoma, and a metastasis from a 46, XY phenotypic female.

We present a case report of a 16-year-old, phenotypic female with bilateral dysgerminomas, a unilateral gonadoblastoma, and a peritoneal metastasis. The patient's constitutional karyotype was 46,XY. The chromosomal copy number, examined by the comparative genomic hybridization technique, showed 3 gains in the dysgerminoma of the right ovary, 6 gains in the dysgerminoma of the left ovary, and 2 gains and 1 loss in the gonadoblastoma of the left ovary. The metastasis showed 5 gains of which 4 were also observed in the dysgerminoma of the left ovary. The DNA ploidy classifications of the gonadoblastoma and the dysgerminoma in the right ovary were tetraploid, whereas the dysgerminoma in the left ovary and the metastasis were aneuploid. We therefore propose that the metastasis most probably developed from the dysgerminoma of the left ovary.

Genome profiles of familial/bilateral and sporadic testicular germ cell tumors.

In order to investigate the genetics of testicular germ cell tumors (TGCTs), we examined 33 TGCTs, including 15 familial/bilateral and 18 sporadic tumors, using comparative genomic hybridization. The frequencies of the histological subtypes were comparable between the two groups. Gains of the whole or parts of chromosome 12 were found in 30 tumors (91%). Furthermore, increased copy number of the whole or parts of chromosomes 7, 8, 17, and X, and decreased copy number of the whole or parts of chromosomes 4, 11, 13, and 18 were observed in > or = 50% of the tumors. Sixteen smallest regions of overlapping changes were delineated on 12 different chromosomes. The chromosomal copy numbers of familial/bilateral and sporadic TGCTs were comparable, suggesting similar genetic pathways to disease in both groups. However, significant differences were observed between the two main histological subgroups. Gains from 15q and 22q were associated with seminomas (P = 0.005 and P = 0.02, respectively), whereas gain of the proximal 17q (17q11.2-21) and high-level amplification from chromosome arm 12p, and losses from 10q were associated with nonseminomas (P < 0.001, P = 0.04, and P = 0.03, respectively).

Alterations of the fragile histidine triad gene, FHIT, and its encoded products contribute to testicular germ cell tumorigenesis.

The fragile histidine triad (FHIT) gene, located within chromosome arm 3p, is a potential target for testicular tumorigenesis. In the present study, 62 primary testicular germ cell tumors were analyzed for allelic imbalance (AI) at 10 loci mapping to chromosome bands 3p14.1-21.1. Twenty-seven tumors (44%) showed AI at one or more 3p loci. The chromosome 3 copy number was evaluated by fluorescence in situ hybridization with centromere and p-telomere probes onto interphase nuclei from 22 of the tumors. Sixteen of these (73%) presented three or more signals of each probe in at least one-third of the nuclei. The combined fluorescence in situ hybridization and AI results indicated that tumors with AI at all loci, in most cases (five of six), reflected an increased chromosome copy number, whereas tumors presenting AI only at some loci reflected interstitial chromosomal changes. A smallest region of overlapping changes could be delineated from tumors showing interstitial chromosomal changes (n = 16). The smallest region of overlapping changes was flanked by D3S1312 and D3S1234 and included parts of FHIT. In the second part of this study, expression analyses of FHIT were performed. Transcripts of aberrant lengths were found in 7 of 17 (41%) analyzed tumors and were identified by sequencing as splice variants. Three different types of transcripts were found, and all lacked exon 3. Immunohistochemical staining showed reduced Fhit protein expression, compared with normal testicular tissue, in 62% (40 of 65) of the testicular germ cell tumors. Although we found a significant association between FHIT mRNA alterations and AI (P = 0.006), altered protein expression did not correlate with AI. The nonepithelial components of teratomas showed strong association with reduced Fhit protein compared with the epithelial component (P < 0.001). Interestingly, reduced Fhit expression seems to be associated with metastasis in the patient at the time of diagnosis, although the association was not statistically significant.