Aberrant activation of the Wnt/b-catenin signaling pathway is a common event in human tumor progression. Wnt signaling has also been implicated in maintaining a variety of adult and embryonic stem cells by imposing a restraint to differentiation. To understand the function and mechanism of Wnt/b-catenin signaling on the pathogenesis of teratocarcinoma, we used the mouse teratocarcinoma P19 cell line as a model in vitro. Gsk3b specific inhibitor (SB216763) was used to activate Wnt/b-catenin signaling. All trans-retinoic acid (RA) was used to induce P19 cell differentiation. At different culture times, gene expression was examined by immunofluorescence staining, quantitative real-time PCR, and Westernblotting; BrdU incorporation assays were performed to measure P19 cell proliferation. Small interference RNA technology was used to downregulate c-myc expression. The results showed that SB216763 induced the nuclear translocation of b-catenin, upregulated the expression of c-myc and pluripotency related genes, oct4, sox2 and nanog, and blocked cell differentiation induced by all trans-RA. The proliferation of P19 cells was significantly enhanced by SB216763, as well as c-myc overexpression. C-myc downregulation inhibited P19 cell proliferation caused by activation of Wnt/b-catenin signaling and induced P19 cell differentiation. In conclusion, activation of the Wnt/b-catenin pathway could promote the proliferation and inhibit the differentiation of mouse teratocarcinoma cells by upregulation of c-myc expression. Anat Rec, 295:2104Rec, 295: -2113

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Recent studies demonstrated that the molecules secreted from astrocytes play important roles in the cell fate determination of neural stem cells (NSCs). However, the exact molecules involved and its possible mechanisms in the process remain largely unknown. In this study, astrocyte-conditioned medium (ACM) obtained from astrocytes unstimulated or stimulated by lipopolysaccharide was prepared to treat NSCs. The results showed that both the proliferation and differentiation of NSCs treated with stimulated ACMs were significantly increased compared with those treated with unstimulated ACM. Interleukin-6 (IL-6) antibody neutralization of the ACMs decreased NSC proliferation and astrogliogenesis, while NSC neurogenesis was increased. In contrast, recombinant IL-6 cytokine increased NSC proliferation and astrogliogenesis, but decreased neurogenesis. Furthermore, the expression of phosphorylated signal transducer and activator of transcription 3 (p-stat3) protein as well as serial of basic helix-loop-helix transcription factors (bHLH) mRNA in NSCs exposed to stimulated ACMs significantly increased, respectively. The expression levels of p-stat3 protein and bHLH mRNA of NSCs were significantly altered after adding anti-IL-6 antibody or recombinant IL-6, respectively. The data suggest that IL-6 secreted from activated astrocytes participates in ACM-induced proliferation and differentiation of NSCs via the phosphorylation of stat3 signals and the expression of bHLH transcription factors.

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