Liquid biopsy-based biomarkers, such as microRNAs, represent valuable tools for patient management, but often do not make it to integration in the clinic. We aim to explore issues impeding this transition, in the setting of germ cell tumors, for which novel biomarkers are needed. We describe a model for identifying and validating clinically relevant microRNAs for germ cell tumor patients, using both in vitro, in vivo (mouse model) and patient-derived data. Initial wide screening of candidate microRNAs is performed, followed by targeted profiling of potentially relevant biomarkers. We demonstrate the relevance of appropriate (negative) controls, experimental conditions (proliferation), and issues related to sample origin (serum, plasma, cerebral spinal fluid) and pre-analytical variables (hemolysis, contaminants, temperature), all of which could interfere with liquid biopsy-based studies and their conclusions. Finally, we show the value of our identification model in a specific scenario, contradicting the presumed role of miR-375 as marker of teratoma histology in liquid biopsy setting. Our findings indicate other putative microRNAs (miR-885-5p, miR-448 and miR-197-3p) fulfilling this clinical need. The identification model is informative to identify the best candidate microRNAs to pursue in a clinical setting.

The ability to form teratomas in vivo containing multiple somatic cell types is regarded as functional evidence of pluripotency for human pluripotent stem cells (hPSCs). Since the Teratoma assay is animal dependent, laborious, and only qualitative, the PluriTest and the hPSC ScoreCard assay have been developed as in vitro alternatives. Here we compared normal hPSCs, induced hPSCs (hiPSCs) with reactivated reprogramming transgenes, and human embryonal carcinoma cells (hECs) in these assays. While normal hPSCs gave rise to typical teratomas, the xenografts of the hECs and the hiPSCs with reactivated reprogramming transgenes were largely undifferentiated and malignant. The hPSC ScoreCard assay confirmed the line-specific differentiation propensities in vitro. However, when undifferentiated cells were analyzed by the PluriTest, only hECs were identified as abnormal whereas all other cell lines were indistinguishable and resembled normal hPSCs. Our results indicate that pluripotency assays are best selected on the basis of intended downstream applications.

Introduction: Insulin analogues are structurally modified molecules with altered pharmaco-kinetic and -dynamic properties compared to regular human insulin used by diabetic patients. While these compounds are tested for undesired mitogenic effects, an epidemiological discussion is ongoing regarding an association between insulin analogue therapy and increased cancer incidence, including breast cancer. Standard in vivo rodent carcinogenesis assays do not pick up this possible increased carcinogenic potential. Methods: Here we studied the role of insulin analogues in breast cancer development. For this we used the human relevant mammary gland specific p53^R270H/+WAPCre mouse model. Animals received life long repeated treatment with four different insulin (−like) molecules: normal insulin, insulin glargine, insulin X10 (AspB10) or insulin-like growth factor 1 (IGF1). Results: Insulin-like molecules with strong mitogenic signaling, insulin X10 and IGF1, significantly decreased the time for tumor development. Yet, insulin glargine and normal insulin, did not significantly decrease the latency time for (mammary gland) tumor development. The majority of tumors had an epithelial to mesenchymal transition phenotype (EMT), irrespective of treatment condition. Enhanced extracellular signaling related kinase (Erk) or serine/threonine kinase (Akt) mitogenic signaling was in particular present in tumors from the insulin X10 and IGF1 treatment groups. Conclusions: These data indicate that insulin-like molecules with enhanced mitogenic signaling increase the risk of breast cancer development. Moreover, the use of a tissue specific cancer model, like the p53^R270H/+WAPCre mouse model, is relevant to assess the intrinsic pro-carcinogenic potential of mitogenic and non-mitogenic biologicals such as insulin analogues.

Cardiovascular diseases caused by loss of functional cardiomyocytes (CMs) are a major cause of mortality and morbidity worldwide due in part to the low regenerative capacity of the adult human heart. Human pluripotent stem cell (hPSC)-derived cardiovascular progenitor cells (CPCs) are a potential cell source for cardiac repair. The aim of this study was to examine the impact of extensive remuscularization and coincident revascularization on cardiac remodelling and function in a mouse model of myocardial infarction (MI) by transplanting doxycycline (DOX)-inducible (Tet-On-MYC) hPSC-derived CPCs in vivo and inducing proliferation and cardiovascular differentiation in a drug-regulated manner. CPCs were injected firstly at a non-cardiac site in Matrigel suspension under the skin of immunocompromised mice to assess their commitment to the cardiovascular lineage and ability to self-renew or differentiate in vivo when instructed by systemically delivered factors including DOX and basic fibroblast growth factor (bFGF). CPCs in Matrigel were then injected intra-myocardially in mice subjected to MI to assess whether expandable CPCs could mediate cardiac repair. Transplanted CPCs expanded robustly both subcutis and in the myocardium using the same DOX/growth factor inducing regime. Upon withdrawal of these cell-renewal factors, CPCs differentiated with high efficiency at both sites into the major cardiac lineages including CMs, endothelial cells, and smooth muscle cells. After MI, engraftment of CPCs in the heart significantly reduced fibrosis in the infarcted area and prevented left ventricular remodelling, although cardiac function determined by magnetic resonance imaging was unaltered. Replacement of large areas of muscle may be required to regenerate the heart of patients following MI. Our human/mouse model demonstrated that proliferating hPSC-CPCs could reduce infarct size and fibrosis resulting in formation of large grafts. Importantly, the results suggested that expanding transplanted cells in situ at the progenitor stage maybe be an effective alternative causing less tissue damage than injection of very large numbers of CMs.

Predicting developmental potency and risk of posttransplantation tumor formation by human pluripotent stem cells (hPSCs) and their derivatives largely rely on classical histological analysis of teratomas. Here, we investigated whether an assay based on microRNAs (miRNA) in blood plasma is able to detect potentially malignant elements. Several hPSCs and human malignant germ cell tumor (hGCT) lines were investigated in vitro and in vivo after mouse xenografting. The multiple conventional hPSC lines generated mature teratomas, while xenografts from induced hPSCs (hiPSCs) with reactivated reprogramming transgenes and hGCT lines contained undifferentiated and potentially malignant components. The presence of these elements was reflected in the mRNA and miRNA profiles of the xenografts with OCT3/4 mRNA and the miR-371 and miR-302 families readily detectable. miR-371 family members were also identified in mouse plasma faithfully reporting undifferentiated elements in the xenografts. This study demonstrated that undifferentiated and potentially malignant cells could be detected in vivo.