Genetic Analysis of Germ Cell Tumors: Current Progress and Future Prospects

Primary mediastinal choriocarcinoma in a female patient: Case report and review of the literature

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Primary mediastinal choriocarcinoma is rare, especially in female patients.

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Genomic losses predominated our case, which has not been previously reported.

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This tumor lacked human chorionic gonadotropin and required histologic diagnosis.

A variant c-KIT mutation, D816H, fundamental to the sequential development of an ovarian mixed germ cell tumor and systemic mastocytosis with chronic myelomonocytic leukemia

An activating point mutation of the c-KIT tyrosine kinase receptor gene, D816H, has been described in germ cell tumors (GCTs). We report an adolescent diagnosed with an ovarian mixed GCT and systemic mastocytosis with chronic myelomonocytic leukemia (SM-CMML). The teratoma and dysgerminoma differed by copy number aberrations via single nucleotide polymorphism (SNP) microarray, but were inclusive of the same c-KIT D816H point mutation (c.2446G>C) also identified in blood and bone marrow mast cells. These findings indicate not only a clonal origin of the GCT and hematologic malignancy, but also suggest a rare KIT mutation may be playing a fundamental role in malignancy development.

Testicular germ cell tumor susceptibility genes from the consomic 129.MOLF-Chr19 mouse strain

Chromosome substitution strains (CSS or consomic strains) are useful for mapping phenotypes to chromosomes. However, huge efforts are needed to identify the gene(s) responsible for the phenotype in the complex context of the chromosome. Here we report the identification of candidate disease genes from a CSS by using a combination of genetic and genomic approaches and by using knowledge about the germ cell tumor disease etiology. We used the CSS 129.MOLF-Chr19 chromosome substitution strain, in which males develop germ cell tumors of the testes at an extremely high rate. We were able to identify three protein-coding genes and one microRNA on chromosome 19 that have previously not been implicated to be testicular tumor susceptibility genes. Our findings suggest that changes in gene expression levels in the gonadal tissues of multiple genes from Chr 19 likely contribute to the high testicular germ cell tumor (TGCT) incidence of the 129.MOLF-Chr19 strain. Our data advance the use of CSS to identify disease susceptibility genes and demonstrate that the 129.MOLF-Chr19 strain serves as a useful model to elucidate the genetics and biology of germ cell transformation and tumor development.

Disrupted traffic of connexin 43 in human testicular seminoma cells: overexpression of Cx43 induces membrane location and cell proliferation decrease

Connexins, the constitutive proteins of gap junctions, are considered to be tumour suppressive agents and are often impaired in the tumourigenic processes. In the present study, the expression of connexin 43 (Cx43), which is involved in the control of spermatogenesis through Sertoli/germ cell coupling, has been investigated in human testicular seminoma cells (tumours and the JKT-1 cell line). Cx43 was immunolocalized in the Golgi apparatus without membrane expression and was detected by immunoblotting in JKT-1 as exclusive 70 kD bands. No mutation could be found by sequencing the transcript obtained by RT-PCR. Transfection with a Cx43-V5 vector reproduced the same gel shift, identifying these 70 kD bands as Cx43. The Cx43-70 kD bands were also expressed in normal testicular tissue, associated with the classical 43 kD isoforms. Stable transfection of JKT-1 with a Cx43-GFP vector allowed restoration of Cx43 membrane expression, functional cell coupling, and inhibition of the cell proliferation rate. Storage of Cx43 in the Golgi apparatus may correspond during spermatogenesis to an intermittent physiological process that becomes permanent in malignant seminoma cells as a result of the tumourigenic process. By preventing Cx43 membrane expression, this disrupted traffic may itself participate in tumour promotion.

Overrepresentation of the short arm of chromosome 12 in seminoma and nonseminoma groups of testicular germ cell tumors

The amplification of the short arm of the chromosome 12, especially as the i(12p) marker chromosome, has been found to be a highly nonrandom chromosome abnormality associated with testicular germ cell tumors (TGCT). A series of adult TGCT consisting of seven seminomas (SE) and eight nonseminomas (NS) was analyzed by conventional cytogenetics and fluorescent in situ hybridization. Multiplied chromosome 12 material originating from typical i(12p) and from other markers carrying chromosome 12-derived material was found in almost all analyzed tumors (6 of 7 SE cases and 8 of 8 NS cases). Heterogeneity in the copy number of i(12p) and other 12p-derived markers, as well as chromosome 12 aneuploidy, were higher in NS tumors than in SE.

No recurrent structural abnormalities apart from i(12p) in primary germ cell tumors of the adult testis

Malignant transformation may be caused by gene deregulation resulting from specific chromosomal rearrangements, by amplification, by mutations in proto-oncogenes, by loss of tumor suppressor genes, or a combination of these. We investigated the role of numerical and structural chromosomal abnormalities in 102 cytogenetically abnormal cases of primary testicular germ cell tumors of adolescents and adults (TGCT) [32 seminomas (SE) and 70 nonseminomatous germ cell tumors (NS)]. We confirmed that an isochromosome for 12p, i(12p), is the only consistent structural chromosomal abnormality in TGCT, present in about 70% of our cases. Both the frequency and the number of copies of i(12p) are higher in NS than in SE. This may suggest that i(12p) is involved in tumor progression. Besides i(12p), several clonal structural chromosomal abnormalities were found, but none appeared to be specific. SE and NS had chromosome numbers in the triploid range, with significantly higher numbers in SE than in NS (average modal chromosome numbers of 73.4 in SE and 65.0 in NS). Both in SE and NS, some chromosomes were significantly underrepresented (e.g., 11, 13, 18, and Y) and others overrepresented (e.g., 7, 8, 12, 21, and X). In SE, a significantly higher copy number of chromosomes 7, 15, 19, and 22 was found and a significantly lower number of chromosome 17, compared with NS. These chromosomes may play an important role in the differentiation of TGCT.

Acute myeloid leukaemia with +i(12p) shortly after treatment of mediastinal germ cell tumour

We report a patient who developed acute myeloid leukaemia (M2) shortly after successful treatment of a mediastinal germ cell tumour. The leukaemia was preceded by a documented myelodysplastic phase. Complex cytogenetic abnormalities were found in bone marrow and peripheral blood cells including +i(12p), typical of germ cell malignancy. Fluorescence in situ hybridization revealed the presence of +i(12p) in myeloblasts, erythroblasts and neutrophils but not in lymphocytes. This case provides further evidence for a common clonal origin of haematological malignancies and mediastinal germ cell tumours.

Lack of heritability in ovarian germ cell malignancies

OBJECTIVE

Our purpose was to determine whether relatives of patients with ovarian germ cell malignancies not associated with sex chromosome abnormalities are at increased risk for similar tumors.

STUDY DESIGN

We reviewed pedigrees of 78 presumptive 46,XX patients (ages ranging from newborn to 20 years) with malignant ovarian germ cell tumors, excluding cases of dysgerminoma and gonadoblastoma. A three-generation family history of each proband was reviewed specifically to identify cancer in any family member.

RESULTS

Seventy-eight mothers, 87 sisters, 135 aunts, and 156 grandmothers were surveyed. None had a malignant ovarian germ cell neoplasm or other malignant ovarian neoplasm.

CONCLUSION

First- and second-degree relatives of probands with ovarian germ cell malignancies do not have an increased risk for similar tumors. These findings were not predicted because of the well-recognized association of hereditary tumors and early age of onset.