Topoisomerase I inhibitor, camptothecin, induces apoptogenic signaling in human embryonic stem cells
Authors: Santiago Gabriel Miriuka
Carolina Paola García
María Elida Scassa
Gustavo Emilio Sevlever
Guillermo Agustín Videla Richardson
Leonardo Romorini
Journal: Stem Cell Research (2014)
Discipline: MOLECULAR BIOLOGY & GENETICS
Keywords: Embryonic stem cells; DNA double strand breaks; genomic integrity; camptothecin; apoptosis
Affiliations: Laboratorio de Investigación aplicada a Neurociencias-LIAN-Fundación para la Lucha contra las Enfermedades Neurológicas de la Infancia-FLENI, Ruta 9, Km 52.5, B1625XAF Escobar, Provincia de Buenos Aires, Argentina. Electronic address: .

Abstract:  Embryonic stem cells (ESCs) need to maintain their genomic integrity in response to DNA damage to safeguard the integrity of the organism. DNA double strand breaks (DSBs) are one of the most lethal forms of DNA damage and, if not repaired correctly, they can lead to cell death, genomic instability and cancer. How human ESCs (hESCs) maintain genomic integrity in response to agents that cause DSBs is relatively unclear. In the present study we aim to determine the hESC response to the DSB inducing agent camptothecin (CPT). We find that hESCs are hypersensitive to CPT, as evidenced by high levels of apoptosis. CPT treatment leads to DNA-damage sensor kinase (ATM and DNA-PKcs) phosphorylation on serine 1981 and serine 2056, respectively. Activation of ATM and DNA-PKcs was followed by histone H2AX phosphorylation on Ser 139, a sensitive reporter of DNA damage. Nuclear accumulation and ATM-dependent phosphorylation of p53 on serine 15 were also observed. Remarkably, hESC viability was further decreased when ATM or DNA-PKcs kinase activity was impaired by the use of specific inhibitors. The hypersensitivity to CPT treatment was markedly reduced by blocking p53 translocation to mitochondria with pifithrin-μ. Importantly, programmed cell death was achieved in the absence of the cyclin dependent kinase inhibitor, p21(Waf1), a bona fide p53 target gene. Conversely, differentiated hESCs were no longer highly sensitive to CPT. This attenuated apoptotic response was accompanied by changes in cell cycle profile and by the presence of p21(Waf1). The results presented here suggest that p53 has a key involvement in preventing the propagation of damaged hESCs when genome is threatened. As a whole, our findings support the concept that the phenomenon of apoptosis is a prominent player in normal embryonic development. 

Retracted: No

PubPeer comments:
 Figure 1D: More similar than expected, could authors check please? ![file] Figure 3B: more similar than expected ![file] , 
 Thank you for your interest in our paper we welcome your comments. For Fig 1D and 3B, we have carefully checked our original data of images and found the highlighted errors. The possible reason would be that, during the building up of the Figures, we unintentionally duplicated the highlighted photomicrographs. In the corrected Figures, the images support the findings of the paper. In conclusion, the unintentional errors done did not alter the results of the scientific work. We are including the corrected images of Fig1D and 3B attached as files. ![file] ![file] ,