Signalling, cell cycle and pluripotency in embryonic stem cells

International audienc

Vascular endothelial growth factor directly inhibits primitive neural stem cell survival but promotes definitive neural stem cell survival

There are two types of neural stem cells (NSCs). Primitive NSCs [leukemia inhibitory factor (LIF) dependent but exogenous fibroblast growth factor (FGF) 2 independent] can be derived from mouse embryonic stem (ES) cells in vitro and from embryonic day 5.5 (E5.5) to E7.5 epiblast and E7.5-E8.5 neuroectoderm in vivo. Definitive NSCs (LIF independent but FGF2 dependent) first appear in the E8.5 neural plate and persist throughout life. Primitive NSCs give rise to definitive NSCs. Loss and gain of functions were used to study the role of vascular endothelial growth factor (VEGF)-A and its receptor, Flk1, in NSCs. The numbers of Flk1 knock-out mice embryo-derived and ES cell-derived primitive NSCs were increased because of the enhanced survival of primitive NSCs. In contrast, neural precursor-specific, Flk1 conditional knock-out mice-derived, definitive NSCs numbers were decreased because of the enhanced cell death of definitive NSCs. These effects were not observed in cells lacking Flt1, another VEGF receptor. In addition, the cell death stimulated by VEGF-A of primitive NSC and the cell survival stimulated by VEGF-A of definitive NSC were blocked by Flk1/Fc-soluble receptors and VEGF-A function-blocking antibodies. These VEGF-A phenotypes also were blocked by inhibition of the downstream effector nuclear factor kappa B (NF-kappa B). Thus, both the cell death of primitive NSC and the cell survival of definitive NSC induced by VEGF-A stimulation are mediated by bifunctional NF-kappa B effects. In conclusion, VEGF-A function through Flk1 mediates survival (and not proliferative or fate change) effects on NSCs, specifically

Derivation and characterization of LIF and FGF2 dependent Porcine Induced Pluripotent Stem Cells [abstract]

Comparative Medicine - OneHealth and Comparative Medicine Poster SessionAuthentic embryonic stem cells (ESC) have probably never been derived from the inner cell mass (ICM) of pig, despite over 25 years of effort. Recently, several groups, including ours, have reported derivation of induced pluripotent stem cells (iPSC) from swine by reprogramming somatic cells with a combination of four factors (OCT4, SOX2, KLF4, C-MYC) delivered by retroviral transduction. The piPSC resembled FGF2- dependent human (h) ESC and are likely to advance swine as a model in biomedical research, since grafts could potentially be matched to the animal that donated the cells for re-programming. The dependence of piPSC on FGF2 also draws parallels to murine pluripotent stem cells derived from advanced epiblast, so-called 'epiblast stem cells'. Indeed, an emerging concept is that there are two kinds of ESC, one dependent on FGF2 and not competent to contribute to germ-line chimeras, the other upon LIF and germ-line competent. The objective of our recent investigations has been to develop LIF- dependent piPSC by using the same reprogramming factors but selecting the colonies on a modified LIF- medium supplemented with two kinase inhibitors, CHIR99021, which inhibits GSK-3beta, and kenpaullone, which inhibits both GSK-3beta and CDK1. The LIF-dependent piPSC, derived here from outgrowths of umbilical cord mesenchyme, expressed markers consistent with pluripotency and bore a striking resemblance to ICM-derived murine ESC in colony morphology, culture characteristics, and short cell cycle time. Currently, the ability of LIF-piPSC to give rise to teratoma and chimeras is under investigation. Supported by Missouri Life Sciences Board Grant 00022147 and NIH grant HD21896

TYK2-induced phosphorylation of Y640 suppresses STAT3 transcriptional activity

STAT3 is a pleiotropic transcription factor involved in homeostatic and host defense processes in the human body. It is activated by numerous cytokines and growth factors and generates a series of cellular effects. Of the STAT-mediated signal transduction pathways, STAT3 transcriptional control is best understood. Jak kinase dependent activation of STAT3 relies on Y705 phosphorylation triggering a conformational switch that is stabilized by intermolecular interactions between SH2 domains and the pY705 motif. We here show that a second tyrosine phosphorylation within the SH2 domain at position Y640, induced by Tyk2, negatively controls STAT3 activity. The Y640F mutation leads to stabilization of activated STAT3 homodimers, accelerated nuclear translocation and superior transcriptional activity following IL-6 and LIF stimulation. Moreover, it unlocks type I IFN-dependent STAT3 signalling in cells that are normally refractory to STAT3 transcriptional activation

Exogenous Leukemia Inhibitory Factor Stimulates Oligodendrocyte Progenitor Cell Proliferation and Enhances Hippocampal Remyelination

New CNS neurons and glia are generated throughout adulthood from endogenous neural stem and progenitor cells. These progenitors can respond to injury, but their ability to proliferate, migrate, differentiate, and survive is usually insufficient to replace lost cells and restore normal function. Potentiating the progenitor response with exogenous factors is an attractive strategy for the treatment of nervous system injuries and neurodegenerative and demyelinating disorders. Previously, we reported that delivery of leukemia inhibitory factor (LIF) to the CNS stimulates the self-renewal of neural stem cells and the proliferation of parenchymal glial progenitors. Here we identify these parenchymal glia as oligodendrocyte (OL) progenitor cells (OPCs) and show that LIF delivery stimulates their proliferation through the activation of gp130 receptor signaling within these cells. Importantly, this effect of LIF on OPC proliferation can be harnessed to enhance the generation of OLs that express myelin proteins and reform nodes of Ranvier in the context of chronic demyelination in the adult mouse hippocampus. Our findings, considered together with the known beneficial effects of LIF on OL and neuron survival, suggest that LIF has both reparative and protective activities that make it a promising potential therapy for CNS demyelinating disorders and injuries

Leukemia inhibitory factor protects cholangiocarcinoma cells from drug-induced apoptosis via a PI3K/AKT-dependent Mcl-1 activation

Cholangiocarcinoma is an aggressive, strongly chemoresistant liver malignancy. Leukemia inhibitory factor (LIF), an IL-6 family cytokine, promotes progression of various carcinomas. To investigate the role of LIF in cholangiocarcinoma, we evaluated the expression of LIF and its receptor (LIFR) in human samples. LIF secretion and LIFR expression were assessed in established and primary human cholangiocarcinoma cell lines. In cholangiocarcinoma cells, we tested LIF effects on proliferation, invasion, stem cell-like phenotype, chemotherapy-induced apoptosis (gemcitabine+cisplatin), expression levels of pro-apoptotic (Bax) and anti-apoptotic (Mcl-1) proteins, with/without PI3K inhibition, and of pSTAT3, pERK1/2, pAKT. LIF effect on chemotherapy-induced apoptosis was evaluated after LIFR silencing and Mcl-1 inactivation. Results show that LIF and LIFR expression were higher in neoplastic than in control cholangiocytes; LIF was also expressed by tumor stromal cells. LIF had no effects on cholangiocarcinoma cell proliferation, invasion, and stemness signatures, whilst it counteracted drug-induced apoptosis. Upon LIF stimulation, decreased apoptosis was associated with Mcl-1 and pAKT up-regulation and abolished by PI3K inhibition. LIFR silencing and Mcl-1 blockade restored drug-induced apoptosis. In conclusion, autocrine and paracrine LIF signaling promote chemoresistance in cholangiocarcinoma by up-regulating Mcl-1 via a novel STAT3- and MAPK-independent, PI3K/AKT-dependent pathway. Targeting LIF signaling may increase CCA responsiveness to chemotherapy

Tumour-derived leukaemia inhibitory factor is a major driver of cancer cachexia and morbidity in C26 tumour-bearing mice

BACKGROUND: Cancer cachexia is a metabolic wasting syndrome that is strongly associated with a poor prognosis. The initiating factors causing fat and muscle loss are largely unknown. Previously, we found that leukaemia inhibitory factor (LIF) secreted by C26 colon carcinoma cells was responsible for atrophy in treated myotubes. In the present study, we tested whether C26 tumour‐derived LIF is required for cancer cachexia in mice by knockout of Lif in C26 cells. METHODS: A C26 Lif null tumour cell line was made using CRISPR‐Cas9. Measurements of cachexia were compared in mice inoculated with C26 vs. C26^Lif−/− tumour cells, and atrophy was compared in myotubes treated with medium from C26 vs. C26^Lif−/− tumour cells. Levels of 25 cytokines/chemokines were compared in serum of mice bearing C26 vs. C26^Lif−/− tumours and in the medium from these tumour cell lines. RESULTS: At study endpoint, C26 mice showed outward signs of sickness while mice with C26^Lif−/− tumours appeared healthy. Mice with C26^Lif−/− tumours showed a 55–75% amelioration of body weight loss, muscle loss, fat loss, and splenomegaly compared with mice with C26 tumours (P < 0.05). The heart was not affected by LIF levels because the loss of cardiac mass was the same in C26 and C^26Lif−/− tumour‐bearing mice. LIF levels in mouse serum was entirely dependent on secretion from the tumour cells. Serum levels of interleukin‐6 and G‐CSF were increased by 79‐fold and 68‐fold, respectively, in C26 mice but only by five‐fold and two‐fold, respectively, in C26^Lif−/− mice, suggesting that interleukin‐6 and G‐CSF increases are dependent on tumour‐derived LIF. CONCLUSIONS: This study shows the first use of CRISPR‐Cas9 knockout of a candidate cachexia factor in tumour cells. The results provide direct evidence for LIF as a major cachexia initiating factor for the C26 tumour in vivo. Tumour‐derived LIF was also a regulator of multiple cytokines in C26 tumour cells and in C26 tumour‐bearing mice. The identification of tumour‐derived factors such as LIF that initiate the cachectic process is immediately applicable to the development of therapeutics to treat cachexia. This is a proof of principle for studies that when carried out in human cells, will make possible an understanding of the factors causing cachexia in a patient‐specific manner.This work was supported by NIAMS R01AR060217 to S. C. K. and R. W. J. and NIAMS R01 R01AR060209 to A. R. J., and by the Dudley Allen Sargent Research Fund. The authors certify that they comply with the ethical guidelines for publishing in the Journal of Cachexia, Sarcopenia and Muscle: update 2017.40 (R01AR060217 - NIAMS; R01 R01AR060209 - NIAMS; Dudley Allen Sargent Research Fund)Published versio