JKT-1 is not a human seminoma cell line

The JKT-1 cell line has been used in multiple independent studies as a representative model of human testicular seminoma. However, no cell line for this specific tumour type has been independently confirmed previously; and therefore, the seminomatous origin of JKT-1 must be proven. The genetic constitution of the JKT-1 cells was determined using flow cytometry and spectral karyotyping, as well as array comparative genomic hybridization and fluorescent in situ hybridization. Marker profiling, predominantly based on differentially expressed proteins during normal germ cell development, was performed by immunohistochemistry and Western blot analyses. Moreover, genome wide affymetrix mRNA expression and profiling of 157 microRNAs was performed, and the status of genomic imprinting was determined. A germ cell origin of the JKT-1 cells was in line with genomic imprinting status and marker profile (including positive staining for several cancer-testis antigens). However, the supposed primary tumour, from which the cell line was derived, being indeed a classical seminoma, was molecularly proven not to be the origin of the cell line. The characteristic chromosomal anomalies of seminoma, e.g. gain of the short arm of chromosome 12, as well as the informative marker profile (positive staining for OCT3/4, NANOG, among others) were absent in the various JKT-1 cell lines investigated, irrespective of where the cells were cultured. All results indicate that the JKT-1 cell line is not representative of human seminoma. Although it can originate from an early germ cell, a non-germ cell derivation cannot be excluded.     

KIT and RAS signalling pathways in testicular germ cell tumours: new data and a review of the literature

Testicular germ cell tumours (TGCTs) are the leading cause of cancer deaths in young male Caucasians. Identifying changes in DNA copy number can pinpoint genes involved in tumour development. We defined the smallest overlapping regions of imbalance in TGCTs using array comparative genomic hybridization analysis. Novel regions, or regions which refined those previously reported, were identified. The expression profile of genes from 12p, which is invariably gained in TGCTs, and amplicons defined at 12p11.2-12.1 and 4q12, suggest KRAS and KIT involvement in TGCT and seminoma development, respectively. Amplification of these genes was not found in intratubular germ cell neoplasia adjacent to invasive disease showing these changes, suggesting their involvement in tumour progression. Activating mutations of RAS genes (KRAS or NRAS) and overexpression of KRAS were mutually exclusive events. These, correlations between the expression levels of KIT, KRAS and GRB7 (which encodes an adapter molecule known to interact with the KIT tyrosine kinase receptor) and other reported evidence reviewed here, are consistent with a role for activation of KIT and RAS signalling in TGCT development. In order to assess a role for KIT in seminomas, we modulated the level of KIT expression in TCam-2, a seminoma cell line. The likely seminomatous origin of this cell line was supported by demonstrating KIT and OCT3/4 overexpression and gain of 12p material. Reducing the expression of KIT in TCam-2 through RNA inhibition resulted in decreased cell viability. Further understanding of KIT and RAS signalling in TGCTs may lead to novel therapeutic approaches for these tumours.     

Fortschritte in der Grundlagenforschung bei testikulären Keimzelltumoren

Human testicular germ cell tumors (GCTs) comprise several types of neoplasias with different pathogenesis and clinical behavior, referred to as types I, II, and III. They represent different cells of origin, explaining their specific characteristics, including expression of markers useful for diagnosis. Here, the most frequent variant of testicular GCTs will be discussed, i.e., the type II GCT, referred to as TGCTs, i.e. seminomas and nonseminomas. Various risk factors have been identified. These tumors originate from a transformed primordial germ cell/gonocyte, known as carcinoma in situ (CIS), that is able to generate all differentiation lineages (omnipotent). The c-KIT-stem cell factor pathway is of relevance for development of this cancer. Retention of embryonic characteristics probably explains the unique treatment responsiveness to DNA-damaging agents. OCT3/4, a marker of pluripotency, is the optimal diagnostic marker for seminoma and embryonal carcinoma, and CIS, the latter also in semen, suitable for non-invasive screening. In addition, distinction between seminoma and embryonal carcinoma can be made using SOX17 and SOX2. Micro-satellite instability as well as BRAF mutations have been identified to be related to treatment resistance, possibly leading to improved clinical management.     

Establishment and Characterization of a New Human Testicular Seminoma Cell Line, JKT-1

Background: A new human testicular cancer cell line (JKT-1) was established, successfully transplanted into nude mice, and has been maintained for over 2 years. We examined the biological characteristics of JKT-1 cells.
Methods: The original material for JKT-1 was derived from a primary lesion of a left testicular seminoma (pure, typical-type) from a 40-year-old male. The tumor tissue was minced and cultured according to the explant culture method. The cells grew as a monolayer with a doubling time of 28.5 hours.
Results: JKT-1 produced neither alpha-fetoprotein or β-human chorionic gonadotropin, but showed strong immunoreactivities for vimentin and placental alkaline phosphatase. A chromosomal analysis revealed a modal number of 66 with loss of the Y chromosome. Morphologically, JKT-1 cells have a pleomorphic polygonal shape, an increase in the nuclear/cytoplasm ratio, and poor development of organelle and desmosome-like cell-cell junctions. JKT-1 cells were subcutaneously transplanted into the backs of 6-week-old nude mice, and grew classical seminomatous tissue.
Conclusion: This report profiled a seminoma cell line established for both in vitro and in vivo experimental systems. Future studies are planned to investigate germ cells using this seminoma line.     

Analysis of the biological properties and use of comparative genomic hybridization to locate chromosomal aberrations in the human testicular seminoma cell line JKT-1 and its highly metastatic cell line JKT-HM

OBJECTIVE: To examine the biological properties, and utility of comparative genomic hybridization (CGH) to locate chromosomal aberrations, in a new human testicular seminoma cell line, JKT-1, and a highly metastatic cell line, JKT-HM, developed as an animal model of spontaneous metastasis. MATERIALS AND METHODS: JKT-HM was isolated by transplanting cells of JKT-1 into the dorsal skin of nude mice, using methods developed previously. The biological properties of JKT-1 and JKT-HM cells were examined using assays of cell proliferation and in vitro tumour cell invasion, and the DNA index (by flow cytometry). CGH was used to analyse chromosomal aberrations and to detect chromosomal regions causing metastasis in the testicular seminoma cell lines. RESULTS: The JKT-1 and JKT-HM cells showed no difference in morphology or cell proliferation. After transplanting JKT-HM into mice, the cells metastasized to the lung and lymph nodes in all five mice by 50 days. The in vitro tumour cell invasion and animal assays suggested potential invasion and metastasis of JKT-HM. The DNA index was 1.48 for JKT-1 and 1.50 for JKT-HM. CGH analysis revealed various chromosomal aberrations undetected by examining their karyotypes, e.g. loss of 18p, Yq and gain of Xq, and the technique has potential to detect genetic aberrations related to metastasis in this model. CONCLUSIONS: The two cell lines JKT-1 and JKT-HM, and the metastatic animal model used, were useful in studying human testicular seminoma and the metastatic behaviour of cancer. In addition, CGH was useful for analysing the chromosomes of two different cell lines derived from the same parent line.     

Association of intratubular seminoma and intratubular embryonal carcinoma with invasive testicular germ cell tumors

The classification of intratubular germ cell neoplasia of the testis includes an unclassified type (IGCNU), in addition to various other intratubular lesions that show specific forms of differentiation, such as intratubular seminoma and intratubular embryonal carcinoma. Although IGCNU is recognized as a precursor lesion for testicular germ cell tumors, the relationship between differentiated types of intratubular germ cell neoplasia and invasive germ cell tumors of the testis is not well established. The aim of the present study was to examine the association between invasive testicular germ cell tumors and intratubular neoplastic lesions, with particular emphasis on differentiated types of intratubular germ cell neoplasia. The seminiferous tubules adjacent to 42 testicular germ cell tumors were evaluated for the presence of various forms of intratubular germ cell neoplasia. IGCNU was observed in 37 (88%) of 42 cases, whereas intratubular seminoma and intratubular embryonal carcinoma were seen in 19% and 7% of the cases, respectively. Intratubular seminoma was associated primarily with seminomas or mixed germ cell tumors with a seminomatous component, but was also present in a case of a nonseminomatous germ cell tumor. Intratubular embryonal carcinoma was associated exclusively with nonseminomatous germ cell tumors. All cases of intratubular embryonal carcinoma were identified morphologically and exhibited histologic features corresponding to traditional definitions of this lesion. No examples of intratubular embryonal carcinoma as defined by CD30 expression alone in the absence of an intratubular proliferation were observed. The presence of intratubular seminoma in a nonseminomatous germ cell tumor suggests that it is a true preinvasive lesion rather than a manifestation of intratubular spread of an established invasive seminoma. The low incidence of intratubular embryonal carcinoma supports the theory that most nonseminomatous germ cell tumors evolve initially as seminomas, rather than directly from a differentiated intratubular neoplastic lesion.     

Distribution of pituitary adenylate cyclase‐activating polypeptide (PACAP) in the human testis and in testicular germ cell tumors

Pituitary adenylate cyclase‐activating peptide (PACAP) is a neuropeptide expressed in the central nervous system and peripheral organs. Previous studies revealed the role and distribution of PACAP in the rodent testis, however, its presence in the human testis and in testicular germ cell tumors is not known. We used RT‐PCR and immunohistological observations to investigate whether human testicular tissue and testicular germ cell tumors contain PACAP. The mRNAs for PACAP and its receptors were detected in total RNA extracted from human testes. PACAP immunoreactivity was observed in spermatogonia and spermatids from normal testes. In contrast, diffuse PACAP immunopositivity was observed in seminoma tumor cells, while only faint immunoreactivity was observed in embryonal carcinoma cells. Our data suggest that PACAP may play a role in human spermatogenesis and in testicular germ cell tumor development.     

Vasculogenesis and angiogenesis in nonseminomatous testicular germ cell tumors

Testicular germ cell tumors (TGCTs) comprise the vast majority of all testicular malignancies and are the most common type of cancer among young male adults. The nonseminomatous variant of TGCTs is characterized by the presence of embryonic and extraembryonic tissues together with a population of pluripotent cancer stem cells, the so-called embryonal carcinoma. One of the main causes of the resistance of these tumors to therapy is their ability to invade adjacent tissues and metastasize into distant sites of the body. Both of these tumor processes are highly favored by the neovascularization of the malignant tissue. New vessels can be generated by means of angiogenesis or vasculogenesis, and both have been observed to occur during tumor vascularization. Nevertheless, the precise contribution of each process to the neoplastic vascular bed of TGCTs remains unknown. In addition, another process known as tumor-derived vasculogenesis, in which malignant cells give rise to endothelial cells, has also been reported to occur in a number of tumor types, including experimental TGCTs. The participation and cross talk of these 3 processes in tumor vascularization is of particular interest, given the embryonic origin of teratocarcinomas. Thus, in the present review, we discuss the importance of all 3 vascularization processes in the growth, invasion, and metastasis of testicular teratocarcinomas and summarize the current state of knowledge of the TGCT microenvironment and its relationship with vascularization. Finally, we discuss the importance of vascularization as a therapeutic target for this type of malignancy.     

Current knowledge of risk factors for testicular germ cell tumors

The development of the human gonads is tightly regulated by the correct sequential expression of many genes and hormonal activity. Disturbance of this regulation does not only prevent proper development of the gonads, but it also contributes to the development of testicular germ cell tumors. Recent genetic studies, especially genome‐wide association studies, have made great progress in understanding genetic susceptibility. Although there is strong evidence of inherited risks, many environmental factors also contribute to the development of testicular germ cell tumors. Histopathological studies have shown that most testicular germ cell tumors arise from germ cell neoplasia in situ, which is thought to be arrested and transformed primordial germ cells. Seminoma has features identical to germ cell neoplasia in situ or primordial germ cells, whereas non‐seminoma shows varied differentiation. Seminomas and embryonic cell carcinomas have the feature of pluripotency, which is thought to be the cause of histological heterogeneity and mixed pathology in testicular germ cell tumors. Testicular germ cell tumors show high sensitivity to chemotherapies, but 20–30% of patients show resistance to standard chemotherapy. In the present review, the current knowledge of the epidemiological and genomic factors for the development of testicular germ cell tumors is reviewed, and the mechanisms of resistance to chemotherapies are briefly mentioned.     

Correlation between expression of metastasis-related genes and lymph node metastasis in testicular cancer

To investigate the factors related to lymph node metastasis of testicular germ cell tumors, we first established a seminoma orthotopic model with lymph node metastasis in SCID mice by inoculating small fragments from subcutaneous xenografts. Second, we compared the expression patterns of metastasis-related genes of the seminoma xenografts and of the TCam-2 cells which were established as a seminoma cell line from a primary testicular seminoma. Third, we immunohistochemically analyzed human germ cell tumors (25 seminomas, 17 nonseminomas) using monoclonal antibodies to CD34, VEGF, VEGF-C, Flt-4, MMP-2 and E-cadherin. Testicular seminoma xenografts grew in 32/32 (100%) of the inoculated mice, of which 15 (47%) developed macroscopic metastasis to the renal hilar lymph node. Circulating tumor cells were detectable by using a PCR assay for the human beta-globin gene in 25/32 (78%) mice, although metastatic foci were not histologically evident in the visceral organs, including lungs, liver, kidneys and spleen. This may reflect the lymphophilic characteristics of the seminoma cells used. Regarding mRNA expression of metastasis-related genes, an increased expression of MMP-2 and VEGF compared with that in the s.c. xenografts was demonstrated by RT-PCR assay in the testicular seminoma xenografts. In addition, uPAR, MMP-1, MMP-2, MT1-MMP and MT3-MMP showed a a stronger expression and PAI-2 a weaker expression in the seminoma xenografts than did TCam-2 cells. These results suggest a higher metastatic potential of the seminoma xenografts, especially testicular xenografts, as compared with TCam-2 cells. In the immunohistochemical study, a significant correlation was found between MMP-2 expression and lymph node metastasis, which is compatible with the results for the metastasis-related gene expression from the seminoma xenografts.     

Immunological tissue markers in the diagnosis of testicular cancer

Summary Immunohistochemistry greatly contributes to the accuracy of the diagnosis in testicular germ cell tumors (TGCT). Human chorionic gonadotropin (HCG) and alphafetoprotein (AFP) are the most used markers in testicular cancer, where the immunostaining is positive in non-seminomatous TGCT. Pure seminoma does not produce these proteins but some are combined with syncytiotrophoblastic cells which elaborate HCG, producing elevated HCG serum levels and positive immunostaining. Other markers deserve mention. Among these there are placental alkaline phosphatase (PLAP), ferritin (Fe), pregnancy specific beta₁-glycoprotein (SP₁), human placental lactogen (HPL), carcinoembrionic antigen (CEA) and alpha₁-antitrypsin (A₁AT). In addition, the recognition of intermediate filament proteins, such as keratin and vimentin, allow differentiation between seminoma and embryonal carcinoma.     

Spontaneous maturation in the metastatic region of a bilateral testicular germ cell tumor

A case of bilateral testicular germ cell tumor of different cell types was found to have a mature teratoma in the metastatic region. Histology of the right testis revealed seminoma and embryonal carcinoma while the left testis revealed seminoma and mature teratoma. A mature teratoma, containing cartilage components, was also found in the right para-aortic lymph node. The findings of the case are described and the literature on cases with maturation in the metastatic region are reviewed.     

Epigenetic profile of testicular germ cell tumours

DNA methylation is the best known and most thoroughly studied epigenetic mechanism. Hypermethylation of CpG islands associated with silencing of tumour suppressor genes or tumour-related genes is a common hallmark of human cancer. The list of tumour-related genes with aberrant hypermethylation in their CpG islands has been increasing. There is also the potential for using DNA methylation profile data as markers for various types of human cancer. In this paper, we review the methylation profile of testicular germ cell tumours (TGCTs). We show that TGCTs have distinctive DNA methylation profiles that differ from those of somatic tissue-derived cancers or somatic tissues. We also discuss the methylation profile of TGCTs in terms of the DNA reprogramming that occurs in primordial germ cells or pre-implantation embryos. Finally, we describe the potential clinical utility of this unique methylation phenotype in TGCTs with regard to developing a novel tumour marker. These data suggest that unmethylated DNA fragments in TGCTs may have diagnostic implications. Further elucidation of epigenetic profiles in TGCTs is expected to provide a new insight into the biology of this disease.