Expression of embryonic stem cell markers in cultured JKT-1, a cell line derived from a human seminoma.

Testicular germ cell tumours (TGCTs), the most frequent solid tumour of the young men, originate from the primitive germ cells. They share some pluripotency stem-cell markers which may help to distinguish between seminoma, the most frequent TGCTs and non-seminoma tumours, such as embryonal carcinoma, teratocarcinoma or choriocarcinoma. Due probably to the propensity of seminoma to apoptosis, only two cell lines originated from pure testicular seminoma, TCam-2 and JKT-1 have been up to now, established, maintained and proposed as representative models of human testicular seminoma. However, both seem, following recent reports, to be able to drift. Thus, the molecular signature of embryonic stem-cell markers of the JKT-1 cells cultured in our laboratory, were studied by RT-PCR, Western blot and immunofluorescence (IF). JKT-1 cells analysed after 30 passages, expressed placenta alkaline phosphatase but not alphafoetoprotein (alphaFP) nor beta-human chorionic gonadotropin. JKT-1 cells also expressed markers of pluripotency such as NANOG and OCT3/4 and more specific seminoma markers, such as AP2gamma and HIWI. However, protein expression of OCT3/4 and AP2y was weak and these JKT-1 cells expressed SOX2, a marker of embryonal carcinoma and did not express c-KIT usually expressed in most seminoma. Possible derivation through in vitro culture conditions was supported by looking at later passages (61) which showed a decrease of NANOG and HIWI protein expression. JKT-1 cells express a signature of markers which is still near from the one express by seminoma cells, allowing carcinogenetic studies. However, because of their great ability to drift as shown for TCam-2, it is recommended to verify and to precise this molecular signature before reporting functional results.