Novel germ cell markers characterize testicular seminoma and fetal testis

Seminomas are characterized by expression of several stem cell markers, supporting their origin from germ cells. The current study focuses on novel germ cell markers in normal testes compared to those in fetal testes and different progression stages of seminomas. Microarray data were followed by RT-PCRs and immunohistochemistry on pure seminomas (pT1 to pT3) compared to adult and fetal testis. An upregulation of known germ cell markers, KIT, OCT4 and NANOG, was confirmed in seminoma specimens. We also identified novel germ cell markers such as BOB1 (POU2AF1, OBF1) and prominin 1 (PROM1, CD133), which were significantly upregulated in seminoma specimens, compared to normal testes. Furthermore, two Sertoli cell markers, SCGF (SCF) and the newly identified neuronal stem cell factor, MCFD2 (SDNSF), were expressed in seminoma cells. While BOB1 was expressed in fetal testis of second and third trimester of gestation, MCFD2 and PROM1 were only present in gonocytes up to the second trimester. All marker genes investigated were not further regulated in progressing tumour stages between pT1 and pT3. In conclusion, the germ cell markers described here provide evidence for the origin of seminoma cells, which could be from the developmental stage of early gonocytes or from spermatogonia re-expressing markers of the developing germ cells.

Gene signatures of testicular seminoma with emphasis on expression of ets variant gene 4

Gene expression patterns of testicular seminoma were analysed applying oligonucleotide microarrays in 40 specimens of different tumour stages (pT1, pT2, pT3) and in normal testes. Transcripts of maternally expressed 3 transcripts were expressed in seminoma without correlation with delta-like 1 homologue expression indicating an impaired imprinting status in seminoma. Interestingly, the transcripts of bromodomain-containing 2 and nuclear autoantigenic sperm protein associated with spermatogenesis were significantly upregulated in progressing tumour stages. Transcription factors TEA domain family member 4 and ETS variant gene 4 (ETV4), weakly expressed in normal testis, were strongly augmented during tumourigenesis. For ETV4 expression, a significant correlation with the increased expression of matrix metalloproteinase 2 and a disintegrin and metalloproteinase domain 15 was determined. The ETV4 protein was localised to nuclei of spermatogonia and revealed an intense staining in seminoma cells. Taken together, we characterised additional transcription factors and spermatogenesis-associated genes involved in the progression of seminoma.