It is not surprising that the HIF-1-alpha transcription factor network was involved in reoxygenation, because it has been reported in a similar situation, i.e., irradiation. Following radiotherapy, tumor reoxygenation leads to nuclear accumulation of HIF-1 in response to reactive oxygen species. One of genes, namely NDRG1, in the HIF-1-alpha transcription factor network draw our attention because it had the greatest change in expression following reoxygenation. NDRG1 is expressed ubiquitously in tissues stimulated under a wide variety of stresses and cell growth-regulatory conditions, such as hypoxia, DNA damage, cellular differentiation, proliferation and growth arrest. It has been reported that NDRG1 is strongly up-regulated under hypoxic conditions. An oncogenic and tumor-promoting role of NDRG1 has also been reported, because it was overexpressed in various human cancers, including lung, brain, skin, kidney, and breast cancers. However, NDRG1 functioned as a metastatic suppressor in prostate and colon cancers. The contradictory roles of NDRG1 in cancer remained to be clarified, although they might be explained by its multiple cellular localizations and complex regulation by diverse physiological and pathological factors. Recently, Toffoli et al. indicated that NDRG1 can be induced under intermittent hypoxia to promote cell migration. Several studies also suggested that NDRG1 is induced by hypoxia and associated with metastasis, but the regulatory mechanism of NDRG1 remains elusive and its function under reoxygenation is still unclear. NDRG1 had the maximal transcriptional response to reoxygenation in this study, which we felt warranted further investigation. We observed that the expression of NDRG1 had an inverse relationship with cell migration upon reoxygenation. These results implicate NDRG1 as a metastasis suppressor, consistent with the findings of Maruyama et al. The discrepancy between our results and those of Toffoli et al. may be due to different type of cells and experimental settings. In order to understand more fully the possible regulatory mechanisms of NDRG1 under reoxygenation, in silico sequence analysis was performed to predict DNA WY 14643 distributor binding motifs of transcription factors in the promoter of NDRG1. Among the MYC-associated binding motifs identified, zinc finger proteins, E2F-MYC activator/cell cycle regulators, and E-box binding factors could affect gene expression. These candidate transcription factors can be further validated by constructing various promoters using luciferase assays. Furthermore, the expression levels of several miRNAs have been shown to change in hypoxia. In particular, miR-210 is induced during hypoxia via a HIF1-dependent mechanism, and the expression of miR-210 had a strong correlation with the expression of NDRG1. Therefore, we hypothesized that the expression of NDRG1 was also regulated by miRNAs. Indeed, the binding sites of the seed regions of four hypoxia-related miRNAs were identified in the 39UTR of NDRG1. Therefore, we proposed a working model based on the bioinformatic prediction and literature survey. This model provides a framework for future biological experiments.