Further characterization of the first seminoma cell line TCam-2

Testicular germ cell tumors of adolescents and adults (TGCTs) can be classified into seminomatous and nonseminomatoustumors. Various nonseminomatous cell lines, predominantly embryonal carcinoma, have been established and proven to be val-uable for pathobiological and clinical studies. So far, no cell lines have been derived from seminoma which constitutes morethan 50% of invasive TGCTs. Such a cell line is essential for experimental investigation of biological characteristics of the cell oforigin of TGCTs, i.e., carcinoma in situ of the testis, which shows characteristics of a seminoma cell. Before a cell line can beused as model, it must be verified regarding its origin and characteristics. Therefore, a multidisciplinary approach was under-taken on TCam-2 cells, supposedly the first seminoma cell line. Fluorescence in situ hybridization, array comparative genomichybridization, and spectral karyotyping demonstrated an aneuploid DNA content, with gain of 12p, characteristic for TGCTs.Genome wide mRNA and microRNA expression profiling supported the seminoma origin, in line with the biallelic expressionof imprinted genes IGF2/H19 and associated demethylation of the imprinting control region. Moreover, the presence of specificmarkers, demonstrated by immunohistochemistry, including (wild type) KIT, stem cell factor, placental alkaline phosphatase,OCT3/4 (also demonstrated by a specific Q-PCR) and NANOG, and the absence of CD30, SSX2-4, and SOX2, confirms thatTCam-2 is a seminoma cell line. Although mutations in oncogenes and tumor suppressor genes are rather rare in TGCTs,TCam-2 had a mutated BRAF gene (V600E), which likely explains the fact that these cells could be propagated in vitro. In con-clusion, TCam-2 is the first well-characterized seminoma-derived cell line, with an exceptional mutation, rarely found inTGCTs.