title: DNA damage causes TP53-dependent coupling of self-renewal and senescence pathways in embryonal carcinoma cells.
abstract: Recent studies have highlighted an apparently paradoxical link between self-renewal and senescence triggered by DNA damage in certain cell types. In addition, the finding that TP53 can suppress senescence has caused a re-evaluation of its functional role in regulating these outcomes. To investigate these phenomena and their relationship to pluripotency and senescence, we examined the response of the TP53-competent embryonal carcinoma (EC) cell line PA-1 to etoposide-induced DNA damage. Nuclear POU5F1/OCT4A and P21CIP1 were upregulated in the same cells following etoposide-induced G 2M arrest. However, while accumulating in the karyosol, the amount of OCT4A was reduced in the chromatin fraction. Phosphorylated CHK2 and RAD51/γH2AX-positive nuclear foci, overexpression of AURORA B kinase and moderate macroautophagy were evident. Upon release from G 2M arrest, cells with repaired DNA entered mitoses, while the cells with persisting DNA damage remained at this checkpoint or underwent mitotic slippage and gradually senesced. Reduction of TP53 using sh- or si-RNA prevented the upregulation of OCT4A and P21CIP1 and increased DNA damage. Subsequently, mitoses, micronucleation and senescence were all enhanced after TP53 reduction with senescence confirmed by upregulation of CDKN2A/P16INK4A and increased sa-β-galactosidase positivity. Those mitoses enhanced by TP53 silencing were shown to be multicentrosomal and multi-polar, containing fragmented and highly deranged chromosomes, indicating a loss of genome integrity. Together, these data suggest that TP53-dependent coupling of self-renewal and senescence pathways through the DNA damage checkpoint provides a mechanism for how embryonal stem cell-like EC cells safeguard DNA integrity, genome stability and ultimately the fidelity of self-renewal.
authors.affiliation: Cancer Sciences Unit, Southampton University Faculty of Medicine, General Hospital, Southampton, UK.
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Jackson
authors.forename: Kristine
authors.initials: K
authors.lastname: Salmina
authors.forename: Anda
authors.initials: A
authors.lastname: Huna
authors.forename: Inna
authors.initials: I
authors.lastname: Inashkina
authors.forename: Eriks
authors.initials: E
authors.lastname: Jankevics
authors.forename: Una
authors.initials: U
authors.lastname: Riekstina
authors.forename: Zane
authors.initials: Z
authors.lastname: Kalnina
authors.forename: Andrey
authors.initials: A
authors.lastname: Ivanov
authors.forename: Paul A
authors.initials: PA
authors.lastname: Townsend
authors.forename: Mark S
authors.initials: MS
authors.lastname: Cragg
authors.forename: Jekaterina
authors.initials: J
authors.lastname: Erenpreisa
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D064107:Aurora Kinase B; D064127:Aurora Kinases; D001343:Autophagy; D045744:Cell Line, Tumor; D016922:Cellular Senescence / Q000502:physiology*; D064447:Checkpoint Kinase 2; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000096:biosynthesis; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000096:biosynthesis / Q000235:genetics; D004249:DNA Damage / Q000235:genetics*; D004260:DNA Repair / Q000502:physiology*; D054278:Embryonal Carcinoma Stem Cells / Q000378:metabolism; D005047:Etoposide / Q000494:pharmacology; D005260:Female; D059565:G2 Phase Cell Cycle Checkpoints / Q000187:drug effects; D006657:Histones / Q000096:biosynthesis; D006801:Humans; D050814:Octamer Transcription Factor-3 / Q000096:biosynthesis / Q000235:genetics; D010051:Ovarian Neoplasms; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis; D034622:RNA Interference; D034741:RNA, Small Interfering; D051135:Rad51 Recombinase / Q000096:biosynthesis; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation; D001616:beta-Galactosidase / Q000096:biosynthesis
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D019941:Cyclin-Dependent Kinase Inhibitor p16; D050759:Cyclin-Dependent Kinase Inhibitor p21; C468783:H2AX protein, human; D006657:Histones; D050814:Octamer Transcription Factor-3; C494173:POU5F1 protein, human; D034741:RNA, Small Interfering; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D005047:Etoposide; D064447:Checkpoint Kinase 2; C576921:AURKB protein, human; D064107:Aurora Kinase B; D064127:Aurora Kinases; C578634:CHEK2 protein, human; D017346:Protein Serine-Threonine Kinases; C495153:RAD51 protein, human; D051135:Rad51 Recombinase; D001616:beta-Galactosidase
keywords: DNA damage; OCT4A/POU5F1; TP53; pluripotency; self-renewal; senescence; tumor cells