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Introduction Pluripotent stem cells (PSC) are known to recurrently acquire genetic aberrations including chromosomal aneuploidy during long-term culture of which the consequences remain largely unknown. A recent study reported that xenografting of aneuploid mouse embryonic stem cells (mESC) gives rise to teratomas containing undifferentiated elements with metastatic capacity. This contrasts with benign teratomas composed of fully differentiated tissues from the three embryonic germ layers obtained by xenografting diploid mESCs. The highlighted study thus proposes that general aneuploidy may drive metastasis of PSC-derived teratomas, thus directly correlating it with malignant potential of PSCs. Main The aneuploid mESC lines used in the aforementioned study showed trisomies of chromosomes 6, 8, 11, 15 or combinations thereof. Interestingly, several of these trisomies, specifically in chromosomes 6, 8, and 11, constitute well-known chromosomal aberrations recurrently acquired in mESCs upon (long-term) in vitro culture. This is suggested to be driven by numerous (proto)oncogenes in these regions. Notably, recurrent chromosomal aberrations are also observed in human PSCs (hPSCs), mostly in chromosome 1, 12, 17, 20 and X, and have similarly been associated with the acquisition of a malignant phenotype in vitro, posing a risk to their potential clinical application. There is synteny between the chromosomes recurrently affected by such aberrations in mouse and human PSCs, namely mouse chromosome 6 and human chromosome 12 as well as mouse and human chromosome 1, suggesting a chromosome-specific phenomenon that may transcend the species barrier. Additionally, in the field of cancer, malignant (but not benign) human germ cell tumors (hGCTs), pathologically similar to the tumors derived from the aforementioned aneuploid mouse PSCs, are characterized by supernumerical copies of chromosome 12, highlighting the additional clinical relevance of these findings and the aneuploid mESC models for GCT research and treatment. Conclusions We suggest that chromosome-specific trisomies, rather than general aneuploidy, might drive teratoma metastasis upon mESC xenografting in vivo. We also observed indications of synteny between the recurrent chromosomal aberrations among human and mouse PSCs, suggesting potentially common intraspecies selection mechanisms. We finally reiterate the similarities observed between the PSC and GCT field related to chromosomal aberrations and malignancy, highlighting the relevance of these experimental models in both research fields.

Some germ cell tumors (GCTs) in men develop into hematologic malignancies; however, the clonal origins of such malignancies remain unknown. In this issue of the JCI, Taylor, Donoghue, et al. unravel the clonal relationship between primary mediastinal nonseminomas (PMNs) and hematologic somatic-type malignancies (HSTMs). Whole-exome sequencing was used to construct phylogenetic trees of the PMNs and the ensuing HSTM clones. HSTMs were derived from multiple distinct clones not detected within the PMNs. Clones from PMNs and HSTMs shared a common precursor, arguably an embryonal carcinoma cell resulting from a reprogrammed primordial germ cell from the thymus. Mutational and copy number variation analysis of a large cohort of patients with PMNs also demonstrated a high prevalence of TP53 mutations not found in testicular nonseminomas. These data likely explain why patients with PMNs are frequently resistant to platinum-based chemotherapy and provide TP53 mutations as potential targets.

The potential for the formation of teratomas or other neoplasms is a major safety roadblock to clinical application of pluripotent stem cell therapies. Preclinical assessment of the risk of tumor formation in this context poses considerable scientific and regulatory challenges, especially because animal xenograft models may not properly reflect the long-term tumorigenic potential of human cells. A better understanding of the biology of spontaneously occurring teratomas and related tumors in humans can help to guide efforts to assess and minimize the potential hazards of embryonic stem cell or induced pluripotent stem cell therapeutics. Here we review the features of teratomas derived experimentally from human pluripotent stem cells and argue that they most closely resemble spontaneous benign teratomas that occur early in both mouse and human life. The natural history and pathology of these spontaneously occurring teratomas provide important clues for preclinical safety assessment and patient monitoring in trials of stem cell therapies.

Novel treatment options are needed for testicular germ cell tumor (TGCT) patients, particularly important for those showing or developing cisplatin resistance, the major cause of cancer-related deaths. As TGCTs pathobiology is highly related to epigenetic (de)regulation, epidrugs are potentially effective therapies. Hence, we sought to explore, for the first time, the effect of the two most recently FDA-approved HDAC inhibitors (HDACis), belinostat and panobinostat, in (T)GCT cell lines including those resistant to cisplatin. In silico results were validated in 261 patient samples and differential expression of HDACs was also observed across cell lines. Belinostat and panobinostat reduced cell viability in both cisplatin-sensitive cells (NCCIT-P, 2102Ep-P, and NT2-P) and, importantly, also in matched cisplatin-resistant subclones (NCCIT-R, 2102Ep-R, and NT2-R), with IC50s in the low nanomolar range for all cell lines. Treatment of NCCIT-R with both drugs increased acetylation, induced cell cycle arrest, reduced proliferation, decreased Ki67 index, and increased p21, while increasing cell death by apoptosis, with upregulation of cleaved caspase 3. These findings support the effectiveness of HDACis for treating TGCT patients in general, including those developing cisplatin resistance. Future studies should explore them as single or combination agents.

Dmrt1 (doublesex and mab-3 related transcription factor 1) is a conserved transcriptional regulator of male differentiation required for testicular development in vertebrates. Here, we show that in mice of the 129Sv strain, loss of Dmrt1 causes a high incidence of teratomas, whereas these tumors do not form in Dmrt1 mutant C57BL/6J mice. Conditional gene targeting indicates that Dmrt1 is required in fetal germ cells but not in Sertoli cells to prevent teratoma formation. Mutant 129Sv germ cells undergo apparently normal differentiation up to embryonic day 13.5 (E13.5), but some cells fail to arrest mitosis and ectopically express pluripotency markers. Expression analysis and chromatin immunoprecipitation identified DMRT1 target genes, whose missexpression may underlie teratoma formation. DMRT1 indirectly activates the GDNF coreceptor Ret, and it directly represses the pluripotency regulator Sox2. Analysis of human germ cell tumors reveals similar gene expression changes correlated to DMRT1 levels. Dmrt1 behaves genetically as a dose-sensitive tumor suppressor gene in 129Sv mice, and natural variation in Dmrt1 activity can confer teratoma susceptibility. This work reveals a genetic link between testicular dysgenesis, pluripotency regulation, and teratoma susceptibility that is highly sensitive to genetic background and to gene dosage.

Germ cell cancers (GCC) are the most frequent malignancy in young Caucasian males. GCC can consist of seminomas (SE) and non-seminomas (malignant NS: embryonal carcinoma (EC), yolk sac tumor (YS), choriocarcinoma (CH) and teratoma (TE)). Current serum-markers used for diagnosis and follow-up (AFP, hCG) are predominantly related to YS and CH and marker positivity can vary during disease. Therefore, stable markers consistently identifying more GCC components, specifically the stem cell components SE and EC, are of interest. Expression of the embryonic stem cell miR-371-3 and miR-302/367 clusters in SE/EC/YS suggest possible application of these micro-RNAs as GCC tumor-markers. The TSmiR protocol constitutes a complete, quality-controlled pipeline for the detection of miRs in serum, based on magnetic bead-based purification and qPCR quantification. As a proof of principle, TSmiR was applied to five independent serum sample series including 80 GCCs, 47 controls, 11 matched pre/post orchidectomy samples and 12 no-GCC testicular masses. GCC serum samples showed a consistent, significant (p < 0.0064) increase of miR-371/372/373/367 levels. Analogous, serum levels returned to baseline after orchidectomy (stage-I disease). Moreover, there was a trend toward higher miR levels in patients with metastasis. These results imply suitability for diagnosis and follow-up. TSmiR showed an overall sensitivity of 98%, clearly outperforming the traditional serum markers AFP/hCG (36%/57%, sensitivityAFP = 3%/45%; sensitivityhCG = 62%/66%, SE/NS). TSmiR misclassified one tumor as a control. Serum AFP/hCG and TSmiR combined identified all T samples correctly. In conclusion, TSmiR constitutes a highly sensitive and reproducible serum test for GCC patients, suitable to be prospectively tested for diagnostic and follow-up purposes. [Display omitted] •TSmiR is a complete quality controlled pipeline for the detection of miRs in serum.•Based on magnetic bead-based purification/qPCR quantification, no pre-amplification.•High sensitivity/specificity for GCC detection in five independent sample series.•miR levels return to baseline after surgery/are increased in metastasized disease.•Therefore, TSmiR is a potential valuable tool for diagnosis & follow-up of GCC.

Human embryonal carcinoma (EC) cells comprise the pluripotent stem cells of malignant non-seminomatous germ cell tumors (GCTs) and represent the malignant counterpart of embryonic stem cells (ESCs). WNT/β-catenin signaling has been implicated in regulating adult and embryonic stem cells although its role in EC cells is less investigated. Here, we studied WNT signaling in a panel of representative pluripotent and nullipotent human EC cell lines. We found that EC cell lines show distinct levels of intrinsic WNT signaling and respond differently to ectopic WNT activation. Short-term activation of WNT signaling induced a differentiation-response in the pluripotent EC cells (NT2 and NCCIT) whereas the nullipotent EC cells (TERA1 and 2102Ep) were refractory and maintained high levels of OCT4 and SSEA4 expression. Long-term activation of WNT signaling in NCCIT and, to a lesser extent, TERA1 cells led to (re)gain of OCT4 expression and a switch from SSEA4 to SSEA1 surface antigens ultimately resulting in OCT4 + /SSEA4 − /SSEA1 + profile. Cisplatin treatment indicated that the OCT4 + /SSEA4 − /SSEA1 + NCCIT cells became more resistant to chemotherapy treatment. Our findings are of particular interest for the GCT and ES cell biology and shed light on the role of WNT signaling in human EC cells.

To date no informative biomarkers exist to accurately predict presence of lymph node metastases (LNM) in esophageal adenocarcinoma (EAC). We studied the discriminative value of Olfactomedin 4 (OLFM4), an intestinal stem cell marker, in EAC. Patients who had undergone esophagectomy as single treatment modality for both advanced (pT2-4) and early (pT1b) adenocarcinoma of the esophagus or gastro-esophageal junction were selected for this study from an institutional database (Erasmus MC University Medical Center, Rotterdam, The Netherlands). Surgical resection specimens of 196 advanced and 44 early EAC were examined. OLFM4 expression was studied by immunohistochemistry and categorized as low (<30%) or high (> = 30%) expression. Low OLFM4 was associated with poor differentiation grade in both advanced (60% vs. 34.8%, p = 0.001) and early EAC (39.1% vs. 9.5%, p = 0.023). LNM were present in 161 (82.1%) of advanced and 9 (20.5%) of early EAC respectively. Low OLFM4 was independently associated with the presence of LNM in advanced EAC in multivariable analysis (OR 2.7; 95% CI, 1.16-6.41; p = 0.022), but not in early EAC (OR 2.1; 95% CI, 0.46-9.84; p = 0.338). However, the difference in association with LNM between advanced (OR 2.7; 95% CI, 1.18-6.34; p = 0.019) and early (OR 2.3; 95% CI, 0.47-11.13; p = 0.302) EAC was non-significant (p = 0.844), suggesting that the lack of significance in early EAC is due to the small number of patients in this group. OLFM4 was not of significance for the disease free and overall survival. Overall, low expression of intestinal stem cell marker OLFM4 was associated with the presence of LNM. Our study suggests that OLFM4 could be an informative marker with the potential to improve preoperative assessment in patients with EAC. Further studies are needed to confirm the value of OLFM4 as a biomarker for LNM.

Objective: The purpose of this review is to evaluate the outcomes of testis sparing surgery (TSS) and to investigate under which circumstances TSS can be considered a safe treatment option in pediatric patients with testicular tumors. Methods: A database search was performed in Cochrane, Pubmed, and Embase for studies that focused on TSS as treatment for testicular tumors in the pediatric population, excluding reviews and single case reports. Results: Twenty studies, describing the surgical treatment of 777 patients with testicular tumors, were included in the analysis. The majority of pediatric patients with benign germ cell tumors (GCTs) (mean age: 3.7 years) and sex cord-stromal tumors (SCSTs) (mean age: 6.6 years) were treated with TSS, 61.9% and 61.2%, respectively. No cases of testicular atrophy occurred. Four of the benign GCTs, i.e., three teratomas and one epidermoid cyst, recurred. No cases of recurrence were reported in patients with SCSTs. Of the 243 malignant GCTs (mean age: 4.2 years), only one patient had TSS (0.4%). Conclusion: TSS is a safe treatment option for prepubertal patients less than 12 years of age with benign GCTs and low grade SCSTs.