Stem cell-like gene expression signature identified in ionizing radiation-treated cancer cells

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 genome-wide 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.