A teratoma is a benign tumor containing a mixture of differentiated tissues and organotypic derivatives of the three germ layers, while a teratocarcinoma also contains embryonal carcinoma cells (EC cells). Experimental teratomas and teratocarcinomas have been derived from early mammalian embryos transplanted into the adult animal (ectopic sites). In the rat, the pluripotency of the transplanted epiblast was demonstrated and a quantifiable restriction of developmental potential persisted after subsequent transplantation of chemically defined cultivated postimplantation embryos. The rat is nonpermissive for teratocarcinoma development and rat pluripotent cell lines have been established only recently. Transplantation of mouse embryos, epiblast, or embryonic stem cells (mESCs) gave rise to teratocarcinomas. The pluripotency of reprogrammed human cells has been tested by a 'gold standard' trilaminar teratoma assay in immunocompromised mice in vivo. Human pluripotent stem cells proposed for use in regenerative medicine such as human embryonic stem cell (hESC), human nuclear-transfer/therapeutic cloning embryonic stem cell (NT-ESC), or human induced pluripotent stem cell (hiPSC) lines, once differentiated in vitro to the desired cell type, should be again tested in a long-term animal teratoma assay to exclude their malignancy. Such an approach led to a recently implemented human therapy with retinal pigmented epithelium. For greater biosafety, the teratoma assay should be standardized and complemented by assessments of mutations/epimutations, RNA/protein expression, and possible immunogenicity of autologous pluripotent cells. Furthermore, the standardized teratoma assay should be directed more to the assessment of EC/malignant cell features than of differentiated tissues, especially after a unique case of human therapy with neural stem cells was found to lead to malignancy. For further resources related to this article, please visit the WIREs website.

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Prostate cancer (PCa) represents the most commonly diagnosed neoplasm among men. miRNAs, as biomarkers, could further improve reliability in distinguishing malignant versus nonmalignant, and aggressive versus nonaggressive PCa. However, conflicting data was reported for certain miRNAs, and there was a lack of consistency and reproducibility, which has been attributed to diverse (pre)analytical factors. In order to address current challenges in miRNA clinical research on PCa, a PubMed-based literature search was conducted with the last update in May 2019. After identifying critical variations in designs and protocols that undermined clear-cut evidence acquisition, and reliable translation into clinical practice, we propose guidelines for most critical steps that should be considered in future research of miRNA as biomarkers, especially in PCa.

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Antiepileptic/teratogen valproate (VPA) is a histone deacetylase inhibitor/ epigenetic drug proposed for the antitumor therapy where it is generally crucial to target poorly or undifferentiated cells to prevent a recurrence. Transplanted rodent gastrulating embryos-proper (primitive streak and three germ layers) are the source of teratoma/teratocarcinoma tumors. Human primitive-streak remnants develop sacrococcygeal teratomas that may recur even when benign (well differentiated). To screen for unknown VPA impact on teratoma-type tumors, we used original 2-week embryoderived teratoma in vitro biological system completed by a spent media metabolome analysis. Gastrulating 9.5-day-old rat embryos-proper were cultivated in Eagle's minimal essential medium (MEM) with 50% rat serum (controls) or with the addition of 2 mM VPA. Spent media metabolomes were analyzed by FTIR. Compared to controls, VPA acetylated histones; significantly diminished overall teratoma growth, impaired survival, increased the apoptotic index, and decreased proliferation index and incidence of differentiated tissues (e.g., neural tissue). Control teratomas continued to grow and differentiate for 14 days in isotransplants in vivo, but in vitro VPA-treated teratomas resorbed. Principal component analysis of FTIR results showed that spent media metabolomes formed well-separated clusters reflecting the treatment and day of cultivation. In metabolomes of VPA-treated teratomas, we found elevation of previously described histone acetylation biomarkers [amide I a-helix and A(CH 3)/A(CH 2)]) with apoptotic biomarkers within the amide I region for b-sheets, and unordered and CH 2 vibrations of lipids. VPA may be proposed for therapy of the undifferentiated component of teratoma tumors and this biological system Abbreviations ASD, autism spectrum disorder; EC, embryonal carcinoma; GTS, growing teratoma syndrome; HDACi, histone deacetylase inhibitor; MEM, minimal essential medium; PCA, principal component analysis; PCNA, proliferating cell nuclear antigen; RMSEC, root mean square error of calibration; RMSECV, root mean square error of cross-validation; SAHA, suberoylanilidehydroxamic acid; VPA, valproate; WEC, whole rat embryo.