GSE31310
A RNA-seq-based gene expression profiling of radiation-induced tumorigenic mammary epithelial cells
To understand tumorigenesis and cancer progression of mammary epithelium, we established a cell model combining over-expression of human telomerase reverse transcriptase gene (hTERT) and heavy-ion radiation from normal human mammary epithelial cells. We subsequently used RNA-seq method to acquire their transcriptomes from two characteristic cell lines, an immortal epithelial cell line (I_hMEC) and a tumorigenic epithelial cell line (T_hMEC), and to look for differentially expressed genes (DEGs) between immortalization and tumorigenicity. We identified 7,053 DEGs, of which 84 were not only highly expressed but also significantly regulated. We found that house-keeping (HK) genes and tissue-specific (TS) genes were regulated differently during tumorigenesis; HK genes tend to be activated but TS genes tend to be repressed. We looked into three important pathways in cancer development: p53 signaling, cell cycle, and apoptosis. Although both immortal and tumorigenic cells have infinite potential to replicate and can escape apoptosis, a great number of genes exhibited different modulation pattern between the two processes. We also found that a significant number of DEGs were involved in epigenetic modification of chromatins. In conclusion, these findings may provide novel biomarkers in studying tumorigenicity and further our understanding of cellular mechanism(s) in the transition from immortal to tumorigenic processes. Overall design: 2 samples examined: immortalized human mammary epithelial cell (I_hMEC) and tumorigenic  human mammary epithelial cell (T_hMEC)