| Summary: | 碩士 === 國立臺灣大學 === 生理學研究所 === 98 === Oxygen fluctuation resulting from hyper-proliferation of tumor cells, abnormal metabolism and disorganized tumor neovasculature characterizes the microenvironment of many cancers, which influences tumor development and angiogenesis. Hypoxia/ reoxygenation induce oxidative stress, which leads to DNA damage and genomic instability. Multiple cellular responses were activated in order to survive under this microenvironment, but little is known about the dynamic response upon reoxygenation. To investigate the dynamic response of signalling pathways in tumor adaptation, a breast cancer cell line MCF-7 was cultured under 0.5 % oxygen condition 24 hours and was harvested at various time points during reoxygenation. Genome-wide microarray results revealed that 274 genes were differentially expressed during reoxygenation; 47.4% of them were up-regulated and 52.3% down-regulated. Furthermore, pathway analysis, including canonical pathway and gene networks, were performed using Ingenuity Pathway Analysis. Selected genes of interest were validated by quantitative real-time PCR, such as N-myc downstream regulated 1 (NDRG1) and cyclin D3 (CCND3). Reoxygenation restored G1 arrest induced by CCND3 knockdown compared to hypoxia. Overexpression NDRG1 suppressed cell migration specifically under reoxygenation through ROS regulating NDRG1 expression in MCF-7. Our results showed dynamic changes of MCF-7 gene expression and molecular pathways upon reoxygenation, which shed some light on understanding cellular response to reoxygenation.
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