Adult Germ Cells Research Articles

Outcome prediction in adult male germ cell tumor patients through expression profiling

5084 Background: Germ cell tumors (GCTs) are the most common solid malignancy in young adult men. Although GCTs are highly curable, when patients do succumb to disease, they have the greatest average number of life years lost of any adult cancer. Currently, patients are risk-stratified using clinical markers defined by the International Germ Cell Cancer Consensus Group (IGCCCG). Identification of molecular markers could improve outcome prediction. Methods: Expression profiling was performed on 74 non-seminomatous tumors (NSGCT) from patients who had received cisplatin based chemotherapy (training set) and 34 similarly treated NSGCT patients (test set). A modified version of Prediction Analysis for Microarrays (PAM) was used to develop a classifier for the binary endpoint of 5 year overall survival (5yOS). We also developed a predictive score for overall survival (OS) based on a weighted sum of the top genes derived using the univariate Cox model. Results: PAM identified a set of 170 transcripts that predicted 5yOS in the training set with a cross-validated classification rate of 60%. In the test set, the predictive gene set correctly classified 90% of the specimens. The predicted good and bad outcome groups showed significant separation in a Kaplan-Meier analysis. For the OS endpoint, we developed a 10 gene model that had a cross-validated predictive accuracy (concordance index, CI) of 0.66. Application of this model to the test set resulted in a CI of 0.83. Dichotomization of the samples based on the median score resulted in significant separation of the patients based on outcome in a Kaplan-Meier analysis. For both endpoints, the gene-based predictor was an independent prognostic factor in a multivariate model that included IGCCCG risk stratification (P<0.01 for both). Conclusions: We have developed and validated two gene-based models that predict outcome in GCT patients. These gene sets should have clinical utility for outcome prediction in GCT patients and should provide novel targets for therapeutic intervention. No significant financial relationships to disclose.

DNA methylation of retrotransposon genes is regulated by Piwi family members MILI and MIWI2 in murine fetal testes

Silencing of transposable elements occurs during fetal gametogenesis in males via de novo DNA methylation of their regulatory regions. The loss of MILI (miwi-like) and MIWI2 (mouse piwi 2), two mouse homologs of Drosophila Piwi, activates retrotransposon gene expression by impairing DNA methylation in the regulatory regions of the retrotransposons. However, as it is unclear whether the defective DNA methylation in the mutants is due to the impairment of de novo DNA methylation, we analyze DNA methylation and Piwi-interacting small RNA (piRNA) expression in wild-type, MILI-null, and MIWI2-null male fetal germ cells. We reveal that defective DNA methylation of the regulatory regions of the Line-1 (long interspersed nuclear elements) and IAP (intracisternal A particle) retrotransposons in the MILI-null and MIWI2-null male germ cells takes place at the level of de novo methylation. Comprehensive analysis shows that the piRNAs of fetal germ cells are distinct from those previously identified in neonatal and adult germ cells. The expression of piRNAs is reduced under MILI- and MIWI2-null conditions in fetal germ cells, although the extent of the reduction differs significantly between the two mutants. Our data strongly suggest that MILI and MIWI2 play essential roles in establishing de novo DNA methylation of retrotransposons in fetal male germ cells.

Expression of Stimulated by Retinoic Acid Gene 8 (Stra8) in Spermatogenic Cells Induced by Retinoic Acid: An In Vivo Study in Vitamin A-Sufficient Postnatal Murine Testes1

Vitamin A is required for male fertility and normal spermatogenesis. Retinoic acid (RA), an active metabolite of vitamin A, is necessary for spermatogonial maturation and proper entry of germ cells into meiotic prophase in the postnatal testes. The expression of Stra8, which is essential for successful meiosis in both male and female gonads and normal spermatogenesis, is directly related to the availability of RA. This study examined the developmental expression pattern of Stra8 transcript in both male and female gonads, provided specific cellular localization of STRA8 protein in the postnatal and adult testis, and investigated RA actions in adult germ cells in a vitamin A-sufficient condition. The peak of Stra8 mRNA expression coincided with the onset of meiosis in postnatal testes. STRA8 protein was detected in gonocytes as early as 5 days postpartum. The expression of STRA8 protein in the neonatal testes was not uniform among spermatogonia, perhaps heralding the asynchronous beginning of spermatogenesis. In adult testes, the highest level of Stra8 mRNA and protein was found in seminiferous epithelial stages VI-VIII. STRA8 protein was localized to some type A and B spermatogonia, preleptotene spermatocytes, and early leptotene spermatocytes. In the vitamin A-sufficient adult testes, RA but not retinol acetate stimulated Stra8 mRNA expression. STRA8 protein expression in adult spermatogonia was induced by RA stimulation, suggesting its role in spermatogonial differentiation. Retinoic acid also increased the number of preleptotene spermatocytes exhibiting 5-bromo-2-deoxyuridine incorporation, indicating a more synchronized premeiotic DNA replication.

Presumed pluripotency markers UTF-1 and REX-1 are expressed in human adult testes and germ cell neoplasms

UTF-1 and REX-1/ZFP42 are transcription factors involved in pluripotency. Because of phenotypic similarities between pluripotent embryonic stem cells and testicular germ cell tumours (TGCT) and the derivation of pluripotent cells from testes, we investigated the expression of UTF-1 and REX-1 during human gonadal development and in TGCT. Expression of UTF-1 and REX-1 was studied in 52 specimens from human gonadal development and in 86 samples from TGCT. UTF-1 and REX-1 were expressed throughout male gonadal development. In the mature testis, UTF-1 was expressed in spermatogonia, whereas REX-1 was expressed in meiotic cells and, together with OCT-3/4, in primary oocytes. Both UTF-1 and REX-1 were expressed in testicular carcinoma in situ and in TGCT. Contrarily to REX-1, UTF-1 was expressed in all spermatocytic seminomas. Unlike other pluripotency markers NANOG and OCT-3/4, UTF-1 and REX-1 are expressed throughout human testes development. The expression pattern indicated that UTF-1 plays a possible role in spermatogonial self-renewal, whereas expression of REX-1 in meiotic cells from both testes and ovary indicate a role in meiosis. UFT-1 and REX-1 are expressed in TGCT and the high abundance of UTF-1 in spermatocytic seminomas is consistent with the hypothesis that this tumour type originates from spermatogonia.

249. Regulated expression of KIT protein in juvenile and adult germ cells of the rodent testis

KIT receptor is an established marker of differentiating spermatogonia and its activation is required to trigger spermatogonial maturation. KIT mRNA, however, can be detected in undifferentiated spermatogonia in the absence of protein expression, as previously established by us in the irradiated adult rat testes [1]. This differential regulation of mRNA and protein is presumably modulated by either local hormone action or by cues from the adult testicular microenvironment. Endogenous regulatory factors known to stimulate KIT synthesis in juvenile male germ cells in vitro are bone morphogenetic protein 4 (BMP4) and retinoic acid (RA), while factors known to suppress KIT at the onset of spermatogenesis have not yet been identified. Activin A, implicated in KIT downregulation in a murine erythroleukemia cell line [2], is produced within the juvenile mammalian testis and influences activities of spermatogonia and Sertoli cells. We hypothesised that activin acts to repress KIT expression in spermatogonia and therefore modulate spermatogonial behaviour. Evidence for this was first derived from Sertoli and germ cell co-cultures of day 8 wild type mouse testes in which exogenous activin addition caused a dose-dependent reduction of KIT mRNA. Whole testes mRNA analyses of two activin transgenic mouse models, the newborn Inhba−/− (lacking activin A) and postnatal InhbaBK/BK (decreased bioactive activin), revealed a significant elevation in KIT expression relative to wild type littermates. In the postnatal day 7 InhbaBK/BK testes, an elevated proportion of differentiated spermatogonia, increased cell surface KIT protein levels, enhanced mRNA levels of a known downstream target of KIT signalling pathway, cyclind3 and a meiotic marker, Sycp3, were observed. These data provide the first comprehensive evidence for activin modulation of KIT expression at spermatogenesis onset, in germ cells of the juvenile testis. This finding is of fundamental importance to other KIT-dependent processes. (1) Prabhu, S.M., et al. Expression of c-Kit receptor mRNA and protein in the developing, adult and irradiated rodent testis. Reproduction, 2006. 131(3): p. 489–99. (2) Hino, M., et al. Down-modulation of c-kit mRNA and protein expression by erythroid differentiation factor/activin A. FEBS Lett, 1995. 374(1): p. 69–71.

In vivo differentiation and genomic evolution in adult male germ cell tumors

Germ cell tumors (GCTs) are the most common solid malignancy in young adult men, but the genes and genomic regions involved in their etiology are not fully defined. We report here an investigation of DNA copy number changes in GCTs using 1 Mb BAC arrays. As expected, 12p gain was the defining genomic alteration, occurring in 72/74 GCTs. Parallel expression profiling of these tumors identified potential oncogenes from gained regions (LYN and RAB25) and potential tumor suppressor genes in regions of loss (SYNPO2, TTC12, IGSF4, and EPB41L3). Notably, we observed specific genomic alterations associated with histology, including gain of 17p11.2-q21.32 and loss of 2p25.3 in embryonal carcinoma, gain of 8p23.3-12 and loss of 5p15.33-35.3, 11q23.1-25, and 13q12.11-34 in seminoma, and gain of 1q31.3-42.3, 3p, 14q11.2-32.33, and 20q and loss of 8q11.1-23.1 in yolk sac tumors (YST). Many significant genes that mapped to these regions had previously been associated with specific histologies, such as EOMES (chr3) and BMP2 (chr20) in YST and SPRY2 (chr13) and SOX17 (chr8) in seminomas. Additionally, our results suggest a model in which histologic differentiation of GCTs may drive genomic evolution.

Alterations of Sertoli cell activity in the long-term testicular germ cell death process induced by fetal androgen disruption

Fetal androgen disruption, induced by the administration of anti-androgen flutamide (0.4, 2, and 10 mg/kg day) causes a long-term apoptosis in testicular germ cells in adult male rat offspring. One of the questions raised by this observation is the role of the Sertoli cells in the adult germ cell apoptotic process. It is shown here that Sertoli cells originating from 15-day-old rats treated in utero with the anti-androgen (10 mg/kg d) did no longer protect adult germ cells against apoptosis. Indeed, untreated spermatocytes or spermatids exhibited increased (P<0.0001) active caspase-3 levels when co-cultured with Sertoli cells isolated from rat testes exposed in utero to the anti-androgen. This alteration of Sertoli cell functions was not due to modifications in the androgen signal in the adult (90-day-old) animals, since plasma testosterone and estradiol, androgen receptor expression, and androgen-targeted cell number (e.g., Sertoli cells in the seminiferous tubules) were not affected by the fetal androgen disruption. In contrast, this inability of Sertoli cells to protect germ cells against apoptosis could be accounted for by the potential failure of Sertoli cell functions. Indeed, adult testes exposed in utero to anti-androgens displayed decreased levels of several genes mainly expressed in adult Sertoli cells (anti-Mullerian hormone receptor type II (AMHR2), Cox-1, cyclin D2, cathepsin L, and GSTalpha). In conclusion, fetal androgen disruption may induce alterations of Sertoli cell activity probably related to Sertoli cell maturation, which potentially leads to increased adult germ cell apoptosis.

The DDX3 Subfamily of the DEAD Box Helicases: Divergent Roles as Unveiled by Studying Different Organisms and In Vitro Assays

DDX3 (or Ded1p), the highly conserved subfamily of the DEAD-box RNA helicase family (40 members in humans), plays important roles in RNA metabolism. DDX3X and DDX3Y, the two human paralogous genes of this subfamily of proteins, have orthologous candidates in a diverse range of eukaryotes, from yeast and plants to animals. While DDX3Y, which is essential for normal spermatogenesis, is translated only in the testes, DDX3X protein is ubiquitously expressed, involved in RNA transcription, RNA splicing, mRNA transport, translation initiation and cell cycle regulation. Studies of recent years have revealed that DDX3X participates in HIV and hepatitis C viral infections, and in hepatocellular carcinoma, a complication of hepatitis B and hepatitis C infections. In the urochordates (i.e., Botryllus schlosseri) and in diverse invertebrate phyla (represented by model organisms such as: Drosophila, Hydra, Planaria), DDX3 proteins (termed also PL10) are involved in developmental pathways, highly expressed in adult undifferentiated soma and germ cells and in some adult and embryo's differentiating tissues. As the mechanistic and functional knowledge of DDX3 proteins is limited, we suggest assembling the available data on DDX3 proteins, from all studied organisms and in vitro assays, depicting a unified mechanistic scheme for DDX3 proteins' functions. Understanding the diverse functions of DDX3 in multicellular organisms may be particularly important for effective strategies of drug design.

Three promoters PII, PI.f, and PI.tr direct the expression of aromatase (cyp19) gene in male rat germ cells

Aromatase is the key enzyme responsible for the irreversible transformation of androgens into estrogens. It is encoded by the cyp19 gene and is expressed in the mammalian testis under the control of the proximal promoter PII. Since both somatic and germ cells contain a biologically active aromatase, we looked for the existence of other promoters that may direct the expression of aromatase in adult rat germ cells. Besides the promoter II, we have shown the presence of transcripts derived from the brain promoter PI.f in spermatogonia-preleptotene spermatocytes (G-PL), pachytene spermatocytes (PS), and round spermatids (RS). A new aromatase cDNA has been isolated by 5'-rapid amplification of cDNA ends that we named I.tr (testis rat). The I.tr transcripts are found in all the testicular cell populations studied with a greater expression in PS. Because of the utilization of these three promoters in the adult rat testis, we studied their putative involvement according to the age. At 10 days, aromatase expression was very low and then strongly increased between 10 and 20 days, with a preferential activation of PII and PI.tr. Transcripts coming from PI.f were found starting from 20 days onwards. The new promoter PI.tr, localized between promoters PI.f and PII, is devoid of a TATA box but contains a transcriptional initiator (Inr) and putative regulatory sequences. Therefore, the identification of the specific trans-activating factors should bring some enlightenments to understand the regulation of these three promoters in germ cells especially according to their stage of development.

MAGE-A1, GAGE and NY-ESO-1 cancer/testis antigen expression during human gonadal development

Cancer/testis antigens (CTAs) are expressed in several cancers and during normal adult male germ cell differentiation. Little is known about their role in fetal development of human germ cells. We examined expression of the CTAs MAGE-A1, GAGE and NY-ESO-1 in fetal gonads by single and double immunohistochemical staining. We found that GAGE was expressed in the primordial germ cells of the gonadal primordium, whereas MAGE-A1 and NY-ESO-1 were first detected in germ cells of both testis and ovary after sexual differentiation was initiated. The number of positive germ cells and the staining intensity of all three CTAs peaked during the second trimester and gradually decreased towards birth in both male and female germ cells. In oocytes, MAGE-A1 expression terminated around birth, whereas NY-ESO-1 expression persisted through the neonatal stage and GAGE expression was maintained until adulthood. The population of GAGE-expressing male and female germ cells partially overlapped the population of OCT4-positive cells, whereas MAGE-A1 and NY-ESO-1 were clearly expressed only by OCT4-negative cells. Our results suggest that MAGE-A1 and NY-ESO-1 are associated with highly proliferating germ cells, whereas GAGE proteins have a more general function in germ cells unrelated to any specific developmental stage. The recognition of differential cellular expression of GAGE, MAGE-A1, NY-ESO-1 and OCT4 may help define biologically distinct germ cell subpopulations.

Expression of galectin‐3 and its regulation in the testes

Although spermatogenesis is a complex process under hormonal control, which includes mainly follicle stimulating hormone (FSH) and androgens, little is known about the intra-testicular mediators of these hormones. In the present study, galectin-3 (Gal-3) expression has been identified in human, rat and porcine testes where it is under hormonal control. Gal-3 is present in Sertoli cells and appears to be absent in human and (probably) in rat germ cells. Gal-3 expression was evidenced in the testes, in terms of both mRNA and protein (31 kDa). Gal-3 expression in cultured porcine Sertoli cells was shown to be under the positive control of FSH as well as of two cytokines epidermal growth factor (EGF) and tumour necrosis factor-alpha (TNF-alpha). Gal-3 expression in Sertoli cells is also potentially under the control of mature germ cells as an increased expression was observed in adult rat testes depleted in spermatocytes or spermatids. Although the function of testicular Gal-3 remains to be investigated, a potential role of Gal-3 in germ cell survival/regeneration is suggested based on its increased expression 1 month after a transient germ cell death process triggered by 10 days of treatment with the antiandrogen flutamide. Finally, although in the normal human testes, Gal-3 is exclusively located in the Sertoli cell cytoplasm, a nuclear localization is observed in the infertile testes. Together, the present findings have shown that (i) Gal-3 is expressed in the porcine, rat and human Sertoli cells; (ii) Gal-3 is under the positive control of FSH as well as of EGF and TNF-alpha and possibly of adult germ cells. These observations are compatible with a potential pro-survival role of Gal-3 in the testes.

Teratoma with Malignant Transformation: Experiences of the Cooperative GPOH Protocols MAKEI 83/86/89/96

The designation of a teratoma with malignant transformation (TMT) refers to the occurrence of somatic non-germ cell malignancies within a teratoma. While TMT is a rare but well recognised phenomenon in adult germ cell tumors (GCT), data on TMT in pediatric GCTs are lacking. Between 1982 and 2003, 641 patients with extracranial nontesticular pure teratoma (256 coccygeal, 246 ovarian, 139 other sites) were reported to the MAKEI protocols 83/86/89/96 by various, mainly German centres. Patients with teratoma and somatic malignancy were identified by database queries. Patients with malignant germ cell tumor components were excluded from this analysis. The clinical files were reviewed and re-evaluated centrally. Information was actualized by requisition to the participating hospitals. We identified nine patients (all female, age 0-39 years) meeting the histological criteria of TMT. Two patients had coccygeal teratomas and seven ovarian tumors. Carcinoma was the dominating malignancy (five of nine cases). Tumors with glial differentiation and embryonal tumors occurred in two cases each. Resection was performed in seven patients (including both coccygeal tumors) and adjuvant chemotherapy was administered in one of them. Two patients relapsed after resection, but both were cured with chemotherapy. Two patients suffered from advanced tumors and both were treated with primary chemotherapy. One patient was cured from the malignant component (astrocytoma), but the teratomatous components persisted. The other patient died as a result of progression of her malignant medulloepithelioma. Malignant transformation of pure teratomas constitutes a very rare entity in children and adolescents that is most commonly observed in postpubertal girls with ovarian teratoma. Compared to adult patients, similar malignant entities can be observed in association with teratoma. However, in our series, no sarcoma was diagnosed. In localised tumors, complete resection appears to be adequate, whereas chemotherapy should be considered in patients with R1- or R2-resection. Cisplatinum-based chemotherapy was effective as two of four relapsed patients survived tumor free. However, the ideal regimen has not yet been established and the known sensitivity of the histologic components to cytostatic drugs has to be considered in the choice of treatment. Further molecular biologic studies are necessary to understand the origin of these tumors.

Acrosome‐specific gene AEP1: Identification, characterization and roles in spermatogenesis

Spermatogenesis is a tightly regulated process leading to the development of spermatozoa. To elucidate the molecular spermatogenic mechanisms, we identified an acrosome-specific gene AEP1 in spermatids, which is located in rat chromosome 17p14 with a transcript size of 3,091 bp encoding a signal peptide, zinc finger-like motif, coiled-coil region, several predicted glycosylation and phosphorylation sites. Northern blot and RT-PCR analyses revealed the restricted expression of AEP1 to the testis only. In postnatal rat testes, AEP1 mRNA became detectable from postnatal 25 dpp (round spermatids) and onwards. By using in situ hybridization (ISH) and flow cytometry-fluorescent ISH, only the haploid spermatids yielded the positive AEP1 signal. Immunohistochemistry showed that AEP1 was expressed in the acrosomal cap of late-staged germ cells in rat testis, and co-localized with the acrosomal marker, peanut agglutinin. The spatial expression of AEP1 immunoreactivity in testis was conserved among diverse mammalian species (rat, pig, monkey, human). To further study its roles in spermatogenesis, we showed AEP1 and beta-actin was associated together in complex by co-immunoprecipitation in adult germ cells and by immunofluorescence assay in isolated spermatozoon. In human testes diagnosed with hypospermatogenesis, lower expression of AEP1 was observed, whereas there was no detectable signal in undescended testes. In short, AEP1 is an evolutionary-conserved acrosome-specific gene and likely functions in acrosome-cap formation.

Imbalances of chromosome arm 1p in pediatric and adult germ cell tumors are caused by true allelic loss: A combined comparative genomic hybridization and microsatellite analysis

Previous studies on childhood germ cell tumors (GCTs) report highly variable frequencies of losses at chromosome arm 1p. Since deletions at 1p portend a poor prognosis in other embryonal tumors, this study aims to clarify the question of the frequency of true allelic loss at 1p and whether it constitutes a prognostic parameter. We analyzed 13 GCTs from different gonadal and extragonadal sites of children (4 teratomas, 9 malignant GCTs) and 18 GCTs of adolescents and adults (3 teratomas; 15 malignant GCTs) using automated microsatellite analysis with 23 polymorphic markers and chromosomal "high resolution" comparative genomic hybridization (HR-CGH). With this combined approach, we detected loss of heterozygosity (LOH) at 1p in 8/9 childhood malignant GCTs with concordant data from HR-CGH and microsatellite analyses. In contrast, LOH at 1p was not detected in childhood teratomas (0/4) and constituted a rare event in GCTs of adolescence and adulthood (3/18). The commonly deleted region was located at distal 1p36-pter, with a proximal boundary between the markers D1S450 and D1S2870. These data unequivocally demonstrate that deletion at 1p is common in childhood GCTs and results in allelic loss. This observation argues for the presence of a classical tumor suppressor at distal 1p. Considering the high frequency of LOH at 1p and the overall favorable prognosis of childhood GCTs, a prognostic impact of LOH at 1p in childhood GCTs appears unlikely. However, since two postpubertal tumors with LOH at 1p progressed, a prognostic relevance in this age group seems possible, warranting a prospective evaluation.

Testicular germ cells can colonize sexually undifferentiated embryonic gonad and produce functional eggs in fish

Understanding the mechanisms that regulate germ-cell development is crucial to reproductive medicine and animal production. Animal gametes originally derive from sexually undifferentiated primordial germ cells (PGCs), which develop into mitotic germ cells (oogonia or spermatogonia) before proceeding to meiosis [Wylie, C. (1999) Cell 96, 165-174]. Spermatogonia are thought to include a population of cells with stem cell activity, which proliferate throughout the lifespan of male animals and produce spermatozoa [Zhao, G. Q. & Garbers, D. L. (2002) Dev. Cell 2, 537-547]. However, the functional differences between PGCs and spermatogonial stem cells are poorly understood. Here we show that transplanted adult testicular germ cells can colonize sexually undifferentiated embryonic gonads and resume gametogenesis. Testicular germ cells containing spermatogonial stem cells isolated from adult male rainbow trout (Oncorhynchus mykiss) were transplanted into the peritoneal cavity of newly hatched embryos of both sexes, and the behavior of the donor cells was observed. The testicular germ cells differentiated into spermatozoa in male recipients and fully functional eggs in female recipients. Furthermore, the donor-derived spermatozoa and eggs obtained from the recipient fish were able to produce normal offspring. These findings indicate that fish testicular germ cells, probably spermatogonial stem cells, possess a high level of developmental plasticity and sexual bipotency, even after the animal reaches maturity. Furthermore, our results suggest that spermatogonial stem cells are at least partly functionally similar to PGCs.

Erasure of methylation imprint at the promoter and CTCF-binding site upstream of H19 in human testicular germ cell tumors of adolescents indicate their fetal germ cell origin

Genome-wide epigenetic modification plays a crucial role in regulating genome functions at critical stages of development. In particular, DNA methylation is known to be reprogrammed on a genome-wide level in germ cells and in preimplantation embryos, although it is relatively stable in somatic cells. In this reprogramming process, the genome becomes demethylated, and methylated de novo during later stages of development. Reprogramming of DNA methylation in male germ cells has not been fully investigated. Testicular germ cell tumors (TGCTs) possess a pluripotential nature and display protean histology from germ cells to embryonal and somatic cell differentiation. These properties make TGCT a unique model for studying germ cell development and gametogenesis in respect of DNA reprogramming. In order to obtain an insight into the epigenetic dynamics of TGCTs, we conducted a comprehensive analysis of differential methylated regions (DMRs) on H19 and IGF2 in TGCTs compared with testicular malignant lymphomas. In the present study, we show that methylation imprint at the promoter and CTCF-binding site upstream of H19 was completely erased in both seiminomatous and non-seminomatous TGCTs, whereas differential methylation was observed in testicular lymphomas. The erasure of methylation imprint was also observed in TGCTs with malignant transformation. We found biallelic unmethylation at the promoter and the CTCF-binding site upstream of H19 is required, but not sufficient for the biallelic expression of H19 in TGCTs. These data suggest that factors other than methylation contribute to transcriptional regulation of imprinted genes in TGCTs. The present data have shown that TGCTs carry distinctive epigenetic profiles at the core-imprinting domain of H19/IGF2 from other neoplasms of somatic cell origin. The data also suggest that both seminomatous and non-seminomatous TGCTs carry methylation profiles similar to fetal germ cells, but not adult germ cells, indicating the origin of TGCTs as fetal germ cells.

Involvement of adenomatous polyposis coli ( APC) gene in testicular yolk sac tumor of infants

The pathogenesis of testicular yolk sac tumor (YST) of infants is still unclear. Infantile YSTs rarely show isochromosome 12p or aneuploidy, which are common in adult germ cell tumors. On the other hand, recent epigenetic studies suggest the involvement of some tumor suppressor genes, including the adenomatous polyposis coli (APC) gene. In the present study, we examined 10 infantile pure YSTs for mutation, allelic loss, promoter methylation, and protein expression status of the APC gene to evaluate whether the APC gene plays a significant role in the pathogenesis of infantile YSTs. Loss of heterozygosity at 5q21, where the APC gene is localized, was detected in at least 3 (30%) of the 9 YSTs examined. None of the 10 YSTs showed mutations. Promoter methylation was detected in 7 (70%) of the 10 YSTs; among 7 YSTs showing methylation, 3 YSTs also harbored loss of heterozygosity at 5q21. Immunohistochemically, 8 infantile YSTs did not express the APC protein, whereas 2 YSTs without showing APC methylation, as well as germ cells of normal infantile testes, expressed this protein in the cytoplasm. These data indicate that inactivation of the APC gene, by allelic loss and/or promoter methylation, is related to the occurrence of infantile YSTs.

Human embryonic stem cell genes OCT4, NANOG, STELLAR, and GDF3 are expressed in both seminoma and breast carcinoma

The seminoma class of testicular germ cell tumor (TGCT) are characterized by a morphological resemblance to primordial germ cells (PGCs) or gonocytes, and chromosome duplications at 12p. Recently, it was determined that human embryonic stem cells (hESCs) express genes in common with PGCs, and that three of these genes, GDF3, STELLAR, and NANOG, are located on 12p. The current study was designed to identify whether expression of these 12p genes were elevated in seminoma relative to normal testis, and to determine whether elevated expression was unique to seminoma. Real-time polymerase chain reaction (PCR) and immunohistochemistry were used to assess gene expression in seminoma samples relative to normal testis and endpoint PCR was used to identify the presence or absence of these genes in breast carcinoma. GDF3 expression was increased in eight of nine seminomas compared with normal testis, whereas NANOG, OCT4, or both were expressed at the highest levels in seminoma compared with all other markers analyzed. In addition, the NANOG protein was expressed in the majority of seminoma cells. The adult meiotic germ cell markers BOULE and TEKT1 were undetectable in seminoma, whereas the embryonic and adult germ cell markers DAZL and VASA were significantly reduced. Analysis of these markers in breast carcinoma and the MCF7 breast carcinoma cell line revealed that a core hESC-transcriptional profile could be identified consisting of OCT4, NANOG, STELLAR, and GDF3 and that NANOG protein could be detected in breast carcinoma. These observations suggest that seminoma and breast carcinoma express a common stem cell profile and that the expression of DAZL and VASA in seminoma mark the germ cell origin of seminoma that is absent in breast carcinoma. Our findings suggest that stem cell genes may either play a direct role in different types of carcinoma progression or serve as valuable markers of tumorigenesis.

Alteration of Transforming Growth Factor-β Signaling System Expression in Adult Rat Germ Cells with a Chronic Apoptotic Cell Death Process after Fetal Androgen Disruption

In utero exposure to chemicals with antiandrogen activity induces undescended testis, hypospadias, and sub- or infertility. The hypospermatogenesis observed in the adult rat testis exposed in utero to the antiandrogen flutamide has been reported to be a result of a long-term apoptotic cell death process in mature germ cells. However, little if anything is known about the upstream signaling mechanisms controlling this apoptosis. In the present study, we have investigated the possibility that the TGF-beta signaling pathway may be at play in this control of the apoptotic germ cell death process. By using a model of adult rat exposed in utero to 0, 0.4, 2, or 10 mg/kg.d flutamide, we observed that pro-TGF-beta signaling members, such as the three isoforms of TGF-beta ligands (TGF-beta1-3), the two TGF-beta receptors (TGF-betaRI and -RII) and the R-Smads Smad 1, Smad 2, Smad 3, and Smad 5 were inhibited at the mRNA and protein levels, whereas the anti-TGF-beta signaling member Smad 7 was overexpressed. Furthermore, we report that the overexpression of Smad 7 mRNA could induce an activation of c-Jun N-terminal kinase, because of the observed c-Jun overexpression, activation, and nuclear translocation leading to an increase in the transcription of the proapoptotic factor Fas-L. Together, the alterations of TGF-beta signaling may represent upstream mechanisms underlying the adult germ cell apoptotic process evidenced in adult rat testis exposed in utero to antiandrogenic compounds such as flutamide.

Conditional Expression of the CTCF-Paralogous Transcriptional Factor BORIS in Normal Cells Results in Demethylation and Derepression of MAGE-A1 and Reactivation of Other Cancer-Testis Genes

Brother of the Regulator of Imprinted Sites (BORIS) is a mammalian CTCF paralog with the same central 11Zn fingers (11ZF) that mediate specific interactions with varying approximately 50-bp target sites. Regulated in vivo occupancy of such sites may yield structurally and functionally distinct CTCF/DNA complexes involved in various aspects of gene regulation, including epigenetic control of gene imprinting and X chromosome inactivation. The latter functions are mediated by meCpG-sensitive 11ZF binding. Because CTCF is normally present in all somatic cells, whereas BORIS is active only in CTCF- and 5-methylcytosine-deficient adult male germ cells, switching DNA occupancy from CTCF to BORIS was suggested to regulate site specificity and timing of epigenetic reprogramming. In addition to 11ZF-binding paternal imprinting control regions, cancer-testis gene promoters also undergo remethylation during CTCF/BORIS switching in germ cells. Only promoters of cancer testis genes are normally silenced in all somatic cells but activated during spermatogenesis when demethylated in BORIS-positive germ cells and are found aberrantly derepressed in various tumors. We show here that BORIS is also expressed in multiple cancers and is thus itself a cancer-testis gene and that conditional expression of BORIS in normal fibroblasts activates cancer-testis genes selectively. We tested if replacement of CTCF by BORIS on regulatory DNA occurs in vivo on activation of a prototype cancer-testis gene, MAGE-A1. Transition from a hypermethylated/silenced to a hypomethylated/activated status induced in normal cells by 5-aza-2'-deoxycytidine (5-azadC) was mimicked by conditional input of BORIS and is associated with complete switching from CTCF to BORIS occupancy at a single 11ZF target. This site manifested a novel type of CTCF/BORIS 11ZF binding insensitive to CpG methylation. Whereas 5-azadC induction of BORIS takes only few hours, derepression of MAGE-A1 occurred 1 to 2 days later, suggesting that BORIS mediates cancer-testis gene activation by 5-azadC. Indeed, infection of normal fibroblasts with anti-BORIS short hairpin RNA retroviruses before treatment with 5-azadC blocked reactivation of MAGE-A1. We suggest that BORIS is likely tethering epigenetic machinery to a novel class of CTCF/BORIS 11ZF target sequences that mediate induction of cancer-testis genes.