LIF insensitivity and expression of proteins activated by DNA damage response in teratoma-isolated cells derived from mouse embryonic stem cells

Abstract

We have isolated from teratomas a residual cell population reluctant to differentiate in the tumor to ectoderm, mesoderm and endoderm. The main characteristics of this population, compared with undifferentiated R1-cells were: persistent expression of Oct4 gene, modest expression of primordial germ cell markers, karyotype alterations and the capability to form teratomas once transplanted again to immunodeficient mice. The aim of the present report is to further characterize this cell population by studying two aspects that could be related to their teratogenecity: LIF insensitivity and the expression of DNA-damage activated proteins. We have used Western blot and immunocytochemistry to address these questions. Persistent phosphorylation of STAT3 was observed in the absence of leukemia inhibitory factor, explaining the insensitivity to the cytokine compared to R1-embryonic stem cells cultured in vitro. Second, we analyzed by Western-blot the expression level of different proteins involved in DNA damage response. Teratoma-isolated cells presented high expression levels of all assayed proteins, except for Rad9. In addition, cytoimmuno-detection using histone γH2AX antibody indicated the presence of DNA instability linked to double strand breaks. The data shown here, despite being preliminary, could help to explain the teratogenecity of this particular cell population.