Establishment of a versatile seminoma model indicates cellular plasticity of germ cell tumor cells

Abstract

In western countries, 60% of all malignancies diagnosed in men between 17-45 years of age are germ cell tumors (GCT). GCT arise from the common precursor lesion carcinoma in situ, which transforms within an average of 9 years into invasive Type-II GCTs. Seminomas are considered to be the default developmental pathway of carcinoma in situ cells and the seminoma-like cell line TCam-2 has been used to study seminoma biology in vitro. However, the generation of an animal model, which would allow for the in vivo analysis of seminoma formation, remained elusive. We applied transplantation approaches using TCam-2 cell transfer into ectopic (skin, brain) and orthopic (testis) sites of immunodeficient mice. We demonstrate that a transplantation into the seminiferous tubules results in formation of a carcinoma in situ/seminoma. In contrast, TCam-2 cells adopt an embryonal carcinoma-like fate when grafted to the flank or corpus striatum and display downregulation of the seminoma marker SOX17 and upregulation of the embryonal carcinoma markers SOX2 and CD30. Grafted TCam-2 cells reduce AKT-, ERK-, EphA3-, and Tie2/TEK-signaling to levels comparable to embryonal carcinoma cells. Hence, TCam-2 cell transplantation into the testis generated a carcinoma in situ/seminoma mouse model, which enables addressing the biology of these tumors in vivo. The fact that TCam-2 cells give rise to a carcinoma in situ/seminoma or embryonal carcinoma in a transplantation site specific manner implies that conversion of carcinoma in situ/seminoma to an embryonal carcinoma does not require additional genetic aberrations but relies on signals from the tumor-microenvironment.

Seminoma and Embryonal Carcinoma Footprints Identified by Analysis of Integrated Genome-Wide Epigenetic and Expression Profiles of Germ Cell Cancer Cell Lines

“…In line with the histone modifications (see above), the SOX2 promoter region was found to be strongly hypomethylated in NCCIT (Figure 3A). SOX2 was partly methylated in TCam-2, in line with findings illustrating that TCam-2 can differentiate and become SOX2 positive after extra-gonadal injection in mice [54]. A 220 bp region directly upstream of the TSS of SOX2 (chr3:181429712) has previously been shown to be completely hypomethylated in TCam-2 [55].…”

An oncofetal and developmental perspective on testicular germ cell cancer

“…This suggests KIT dependence of SE and possibly a KITLG saturated micro-environment (threshold level for effect on viability already suggested for KIT in [354]). In the SE cell line TCam-2 [359][360][361][362] Goddard and coworkers identified a small but significant decrease in viability upon KIT knock down [354]. In a similar experiment from our group we could not replicate this result, nor did we detect a consistent effect of KITLG knock down or exogeneous KITL addition on TCam-2 viability (results in supplementary data).…”

SOX2 is essential for in vivo reprogramming of seminoma-like TCam-2 cells to an embryonal carcinoma-like fate

“…Nuclear PRDM1 and the H2A/H4R3me2s was also found in human seminomas, but not in ECs [11]. During in vitro differention of TCam-2 into a mixed non-seminoma and during the in vivo reprogramming, PRDM1 is downregulated and excluded from the nucleus [10, 20, 30]. Thus, in TCam-2-ΔSOX2 clones, nuclear PRDM1 might be responsible for maintenance of H2A/H4R3me2s and suppression of somatic differentiation.…”