e., the most widely used H9 and H1 hESC lines[23,26,27]. DNA microarray technique was used to analyze the transcriptional changes in H9 cell line of hESCs 24 h after 0.4Gy, 2Gy, and

4Gy of gamma-radiation[26]. Quite unexpectedly, it has been found that the order Nilotinib expression levels of a set of core transcription factors governing pluripotency, in particular, and stemness, in general, in hESCs are not changed significantly by IR exposures up to 4 Gy of gamma-radiation[26]. The most common themes involved in manifestation of response of IR-exposed hESCs include p53 stress signaling, cell death/apoptosis, cell cycle regulation, developmental processes, and many others. The key genes that were initially discovered as being IR-responsive in fully differentiated adult human cells, such as CDKN1A, GADD45A, BTG2, and some others, appear to be upregulated by genotoxic stress exposures in human pluripotent stem cells as well[23,26]. The effect of induced expression of stress response genes is clearly dose-dependent, since low doses of genotoxic stressors

may not elicit robust changes in transcriptional responses in hESCs[28]. A modest dose (0.4Gy) of gamma-radiation was found to have an impact on cell death, cancer, and p53 signaling pathways; IR exposure with this dose apparently failed to significantly reduce hESCs proliferation at 24 h post-IR[26]. Importantly, much higher dose of 2Gy of gamma-radiation led to changes in canonical TFG-β and Wnt/β-catenin signaling, including WNT10A (up 2.1-fold), WNT9A, and TGFBR2[26]. The perturbations in Wnt signaling axes following IR exposures could potentially affect the ultimate fate of irradiated hESCs, since Wnt genes are involved in key developmental pathways in human pluripotent stem cells[29,30]. This dose induced CDKN1A overexpression by 2.3-fold in H9 hESCs[26]. Noteworthy, the expression levels

for many genes implicated in general metabolism functions AV-951 (molecular transport SLC6A13, SLC25A13, cell morphology, amino acid metabolism, etc.) were significantly altered in hESCs by 2Gy of IR exposures[26]. Despite a high degree of similarity in gene expression profiles observed both after 2 Gy and 4 Gy of IR exposures, p53 and aryl hydrocarbon signaling, cancer-related processes, cell death, cell cycle and proliferation were found to undergo major modulations in hESCs after the higher dose (4 Gy). Among the highly induced IR-responsive genes were key genes implicated in p53 stress signaling, such as CDKN1A, TP53INP1, HDM2 and TNF receptor genes[26]. The minor gene expression alterations observed in the differentiation processes failed to lead to a loss of pluripotency even after 4 Gy of IR exposures.