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Poor prognosis germ-cell tumours are only cured in about half of patients. We aimed to assess whether treatment intensification based on an early tumour marker decline will improve progression-free survival for patients with germ-cell tumours. In this phase 3, multicentre, randomised trial, patients were enrolled from France (20 centres), USA (one centre), and Slovakia (one centre). Patients were eligible if they were older than 16 years, had evidence of testicular, retroperitoneal, or mediastinal non-seminomatous germ cell tumours based on histological findings or clinical evidence and highly elevated serum human chorionic gonadotropin or alfa-fetoprotein concentrations that matched International Germ Cell Cancer Consensus Group poor prognosis criteria. After one cycle of BEP (intravenous cisplatin [20 mg/m2 per day for 5 days], etoposide [100 mg/m2 per day for 5 days], and intramuscular or intravenous bleomycin [30 mg per day on days 1, 8, and 15]), patients' human chorionic gonadotropin and alfa-fetoprotein concentrations were measured at day 18–21. Patients with a favourable decline in human chorionic gonadotropin and alfa-fetoprotein continued BEP (Fav-BEP group) for 3 additonal cycles, whereas patients with an unfavourable decline were randomly assigned (1:1) to receive either BEP (Unfav-BEP group) or a dose-dense regimen (Unfav-dose-dense group), consisting of intravenous paclitaxel (175 mg/m2 over 3 h on day 1) before BEP plus intravenous oxaliplatin (130 mg/m2 over 3 h on day 10; two cycles), followed by intravenous cisplatin (100 mg/m2 over 2 h on day 1), intravenous ifosfamide (2 g/m2 over 3 h on days 10, 12, and 14), plus mesna (500 mg/m2 at 0, 3, 7 and 11 h), and bleomycin (25 units per day, by continuous infusion for 5 days on days 10–14; two cycles), with granulocyte-colony stimulating factor (lenograstim) support. Centrally blocked computer-generated randomisation stratified by centre was used. The primary endpoint was progression-free survival and the efficacy analysis was done in the intention-to-treat population. The planned trial accrual was completed in May, 2012, and follow-up is ongoing. This study is registered with ClinicalTrials.gov, number NCT00104676. Between Nov 28, 2003, and May 16, 2012, 263 patients were enrolled and 254 were available for tumour marker assessment. Of these 51 (20%) had a favourable marker assessment, and 203 (80%) had an unfavourable tumour marker decline; 105 were randomly assigned to the Unfav-dose-dense group and 98 to the Unfav-BEP group. 3-year progression-free survival was 59% (95% CI 49–68) in the Unfav-dose-dense group versus 48% (38–59) in the Unfav-BEP group (HR 0·66, 95% CI 0·44–1·00, p=0·05). 3-year progression-free survival was 70% (95% CI 57–81) in the Fav-BEP group (HR 0·66, 95% CI 0·49–0·88, p=0·01 for progression-free survival compared with the Unfav-BEP group). More grade 3–4 neurotoxic events (seven [7%] vs one [1%]) and haematotoxic events occurred in the Unfav-dose-dense group compared with in the Unfav-BEP group; there was no difference in grade 1–2 febrile neutropenia (18 [17%] vs 18 [18%]) or toxic deaths (one [1%] in both groups). Salvage high-dose chemotherapy plus a stem-cell transplant was required in six (6%) patients in the Unfav-dose-dense group and 16 (16%) in the Unfav-BEP group. Personalised treatment with chemotherapy intensification reduces the risk of progression or death in patients with poor prognosis germ-cell tumours and an unfavourable tumour marker decline. Institut National du Cancer (Programme Hospitalier de Recherche Clinique).

Testicular tumors are the most common tumors in adolescent and young men and germ cell tumors (TGCTs) account for most of all testicular cancers. Increasing incidence of TGCTs among males provides strong motivation to understand its biological and genetic basis. Gains of chromosome arm 12p and aneuploidy are nearly universal in TGCTs, but TGCTs have low point mutation rate. It is thought that TGCTs develop from premalignant intratubular germ cell neoplasia that is believed to arise from the failure of normal maturation of gonocytes during fetal or postnatal development. Progression toward invasive TGCTs (seminoma and nonseminoma) then occurs after puberty. Both inherited genetic factors and environmental risk factors emerge as important contributors to TGCT susceptibility. Genome-wide association studies have so far identified more than 30 risk loci for TGCTs, suggesting that a polygenic model fits better with the genetic landscape of the disease. Despite high cure rates because of its particular sensitivity to platinum-based chemotherapy, exploration of mechanisms underlying the occurrence, progression, metastasis, recurrence, chemotherapeutic resistance, early diagnosis and optional clinical therapeutics without long-term side effects are urgently needed to reduce the cancer burden in this underserved age group. Herein, we present an up-to-date review on clinical challenges, origin and progression, risk factors, TGCT mouse models, serum diagnostic markers, resistance mechanisms, miRNA regulation, and database resources of TGCTs. We appeal that more attention should be paid to the basic research and clinical diagnosis and treatment of TGCTs.

In 2004, a team led by Jonathan Tilly reported that mice contained oogonial stem cells (OSCs), suggesting that females may be able to generate new oocytes in adulthood—a concept that was, and still is, quite controversial even though those findings have since been replicated by others. In a new report, Tilly and colleagues now perfect the purification of mouse OSCs and, using this technique, they show that similar cells exist in women of reproductive age. They also show that the mouse and human OSCs are able to give rise to oocytes in vivo (in the case of the human cells after xenotransplantation into NOD-SCID mice), while also showing that the mouse OSCs can give rise to embryos after in vitro fertilization. Germline stem cells that produce oocytes in vitro and fertilization-competent eggs in vivo have been identified in and isolated from adult mouse ovaries. Here we describe and validate a fluorescence-activated cell sorting-based protocol that can be used with adult mouse ovaries and human ovarian cortical tissue to purify rare mitotically active cells that have a gene expression profile that is consistent with primitive germ cells. Once established in vitro , these cells can be expanded for months and can spontaneously generate 35- to 50-μm oocytes, as determined by morphology, gene expression and haploid (1 n ) status. Injection of the human germline cells, engineered to stably express GFP, into human ovarian cortical biopsies leads to formation of follicles containing GFP-positive oocytes 1–2 weeks after xenotransplantation into immunodeficient female mice. Thus, ovaries of reproductive-age women, similar to adult mice, possess rare mitotically active germ cells that can be propagated in vitro as well as generate oocytes in vitro and in vivo .

In the human embryo, the genetic program that orchestrates germ cell specification involves the activation of epigenetic and transcriptional mechanisms that make the germline a unique cell population continuously poised between germness and pluripotency. Germ cell tumors, neoplasias originating from fetal or neonatal germ cells, maintain such dichotomy and can adopt either pluripotent features (embryonal carcinomas) or germness features (seminomas) with a wide range of phenotypes in between these histotypes. Here, we review the basic concepts of cell specification, migration and gonadal colonization of human primordial germ cells (hPGCs) highlighting the analogies of transcriptional/epigenetic programs between these two cell types.

Abstract Objectives Preferentially expressed antigen in melanoma (PRAME) has a key role in regulating pluripotency of primordial germ cells and in the development of germ cell tumors of the testis (GCTT). However, its immunohistochemical expression in normal testes and its neoplastic counterpart remain largely unknown. Methods We retrospectively investigated the expression of PRAME in 26 cases of GCTT, 21 cases of germ cell neoplasia in situ (GCNIS), and 17 cases of uninvolved background testes. Results We found that PRAME was expressed more strongly by seminomatous rather than nonseminomatous GCTT (P = .000) and by pure seminoma rather than the seminoma component of seminomatous/nonseminomatous GCTT (P = .025). In addition, GCNIS and uninvolved background testes displayed high levels of PRAME expression. Conclusions PRAME is an additional marker for the differential diagnosis of GCTT and could play a key role in the transition from seminomatous to nonseminomatous GCTT.

The authors trace the emergence of porcine primordial germ cells and develop in vitro models of primordial germ cell development from human and monkey pluripotent stem cells in order to provide insight into early human development. Models of primordial germ cell formation Mouse embryos develop in an elongated cylinder, whereas human embryos initially form in a flat disc. The flat disc morphology is also observed in pig and monkey embryos, making them more suitable for studying some aspects of development, such as the formation of primordial germ cells (PGCs), the precursors of sperm and eggs. M. Azim Surani and colleagues adopt three approaches to develop useful models of human PGCs. They trace the emergence of PGCs and show that they originate from the posterior epiblast and in response to similar signals and epigenetic changes as seen in human development. Using an in vitro model of PGC development from human and monkey pluripotent stem cells, they demonstrate that a balanced SOX17–BLIMP1 gene dosage is necessary and sufficient for specification of human PGCs from cells in a differentiating embryoid that are at an equivalent stage to the posterior epiblast. Human primordial germ cells (hPGCs), the precursors of sperm and eggs, originate during weeks 2–3 of early post-implantation development 1 . Using in vitro models of hPGC induction 2 , 3 , 4 , recent studies have suggested that there are marked mechanistic differences in the specification of human and mouse PGCs 5 . This may be due in part to the divergence in their pluripotency networks and early post-implantation development 6 , 7 , 8 . As early human embryos are not accessible for direct study, we considered alternatives including porcine embryos that, as in humans, develop as bilaminar embryonic discs. Here we show that porcine PGCs originate from the posterior pre-primitive-streak competent epiblast by sequential upregulation of SOX17 and BLIMP1 in response to WNT and BMP signalling. We use this model together with human and monkey in vitro models simulating peri-gastrulation development to show the conserved principles of epiblast development for competency for primordial germ cell fate. This process is followed by initiation of the epigenetic program 9 , 10 , 11 and regulated by a balanced SOX17 – BLIMP1 gene dosage. Our combinatorial approach using human, porcine and monkey in vivo and in vitro models provides synthetic insights into early human development.

Human germ cell tumours (GCTs) are derived from stem cells of the early embryo and the germ line. They occur in the gonads (ovaries and testes) and also in extragonadal sites, where migrating primordial germ cells are located during embryogenesis. This group of heterogeneous neoplasms is unique in that their developmental potential is in effect determined by the latent potency state of their cells of origin, which are reprogrammed to omnipotent, totipotent or pluripotent stem cells. Seven GCT types, defined according to their developmental potential, have been identified, each with distinct epidemiological and (epi)genomic features. Heritable predisposition factors affecting the cells of origin and their niches likely explain bilateral, multiple and familial occurrences of the different types of GCTs. Unlike most other tumour types, GCTs are rarely caused by somatic driver mutations, but arise through failure to control the latent developmental potential of their cells of origin, resulting in their reprogramming. Consistent with their non-mutational origin, even the malignant tumours of the group are characterized by wild-type TP53 and high sensitivity for DNA damage. However, tumour progression and the rare occurrence of treatment resistance are driven by embryonic epigenetic state, specific (sub)chromosomal imbalances and somatic mutations. Thus, recent progress in understanding GCT biology supports a comprehensive developmental pathogenetic model for the origin of all GCTs, and provides new biomarkers, as well as potential targets for treatment of resistant disease.

In mouse embryonic stem cells converted to an epiblast fate in vitro —a state in which the cells can also gain germ cell fate if exposed to the signalling molecule BMP4—the sole expression of the transcription factor NANOG is shown to be sufficient to induce germ cell fate, in the absence of BMP4. The role of Nanog in germ cells The transcription factor gene Nanog is expressed both in pluripotent cells and in primordial germ cells in mice, but its function in germ cells has not been defined. Azim Surani and colleagues find that in embryonic stem cells converted to an epiblast fate in vitro , a state in which they can also gain germ cell fate if exposed to the signalling molecule BMP4, sole expression of Nanog is sufficient to induce germ cell fate in the absence of BMP4. They demonstrate that the resetting of the chromatin that occurred in the primed epiblast allows NANOG to bind and activate the expression of key germ cell factors. The pluripotent factor Sox2 prevents the action of Nanog on these germ cell factors in the epiblast state, while SOX2 and NANOG work together to maintain pluripotency in naive embryonic stem cells. Nanog , a core pluripotency factor in the inner cell mass of blastocysts, is also expressed in unipotent primordial germ cells (PGCs) in mice 1 , where its precise role is yet unclear 2 , 3 , 4 . We investigated this in an in vitro model, in which naive pluripotent embryonic stem (ES) cells cultured in basic fibroblast growth factor (bFGF) and activin A develop as epiblast-like cells (EpiLCs) and gain competence for a PGC-like fate 5 . Consequently, bone morphogenetic protein 4 (BMP4), or ectopic expression of key germline transcription factors Prdm1 , Prdm14 and Tfap2c , directly induce PGC-like cells (PGCLCs) in EpiLCs, but not in ES cells 6 , 7 , 8 . Here we report an unexpected discovery that Nanog alone can induce PGCLCs in EpiLCs, independently of BMP4. We propose that after the dissolution of the naive ES-cell pluripotency network during establishment of EpiLCs 9 , 10 , the epigenome is reset for cell fate determination. Indeed, we found genome-wide changes in NANOG-binding patterns between ES cells and EpiLCs, indicating epigenetic resetting of regulatory elements. Accordingly, we show that NANOG can bind and activate enhancers of Prdm1 and Prdm14 in EpiLCs in vitro ; BLIMP1 (encoded by Prdm1 ) then directly induces Tfap2c . Furthermore, while SOX2 and NANOG promote the pluripotent state in ES cells, they show contrasting roles in EpiLCs, as Sox2 specifically represses PGCLC induction by Nanog . This study demonstrates a broadly applicable mechanistic principle for how cells acquire competence for cell fate determination, resulting in the context-dependent roles of key transcription factors during development.

Reproductive cell formation An RNA interference screen of 30 gene candidates has identified Lin28, a negative regulator of let-7 microRNA processing, as a potentially key regulator of primordial germ cell development, the process in the developing embryo that selects the cells destined to produce sperm and eggs. In addition, Lin28 levels are elevated in primary human germ cell tumours, suggesting that it may also be implicated in germ cell malignancy. In order to investigate the earliest molecular mechanisms of germ cell specification, mouse embryonic stem cells were differentiated into putative primordial germ cells (PGCs) in vitro . The use of inhibitory RNAs to then screen candidate genes for effects on the development of these cells demonstrates a genetic pathway for PGC specification involving Lin28 , a negative regulator of let-7 microRNA processing. The rarity and inaccessibility of the earliest primordial germ cells (PGCs) in the mouse embryo thwart efforts to investigate molecular mechanisms of germ-cell specification. stella (also called Dppa3 ) marks the rare founder population of the germ lineage 1 , 2 . Here we differentiate mouse embryonic stem cells carrying a stella transgenic reporter into putative PGCs in vitro . The Stella + cells possess a transcriptional profile similar to embryo-derived PGCs, and like their counterparts in vivo , lose imprints in a time-dependent manner. Using inhibitory RNAs to screen candidate genes for effects on the development of Stella + cells in vitro , we discovered that Lin28 , a negative regulator of let-7 microRNA processing 3 , 4 , 5 , 6 , is essential for proper PGC development. Furthermore, we show that Blimp1 (also called Prdm1 ), a let-7 target and a master regulator of PGC specification 7 , 8 , 9 , can rescue the effect of Lin28 deficiency during PGC development, thereby establishing a mechanism of action for Lin28 during PGC specification. Overexpression of Lin28 promotes formation of Stella + cells in vitro and PGCs in chimaeric embryos, and is associated with human germ-cell tumours. The differentiation of putative PGCs from embryonic stem cells in vitro recapitulates the early stages of gamete development in vivo , and provides an accessible system for discovering novel genes involved in germ-cell development and malignancy.