Recent studies have reported that embryonic stem (ES) cell-associated gene expression signatures have been
identified in poorly differentiated tumors, revealing a link between ES cell identity and cancer cells. Cancer
cells originate from cancer stem cells (CSCs). Both types of cells share common properties such as self-renewal
and heterogeneity. CSCs are also resistant to conventional chemotherapy and radiotherapy. Here, we show similar
gene expression patterns between ES cells and ionizing radiation (IR)-treated cancer cells. Using genomewide
transcriptome analysis, we compared the gene expression profiles among ES cells, cancer cells, and irradiated
cancer cells, and identified a subset of similar gene expression patterns between ES cells and irradiated cancer
cells, indicated by hierarchical clustering. These gene expression patterns were then confirmed by
quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) analyses. Using bioinformatic
analyses, these candidate genes are also associated with various biological pathways related to stemness in cancer.
Taken together, our data suggest that identification of common molecular characteristics between ES cells
and irradiated cancer cells is important to understand the properties of cancer stem cells and their resistance
to radiotherapy.r